Patent Grant
7050688
The present invention relates generally to fiber optic articles, assemblies, and cables. More specifically, the invention relates to fiber optic articles, assemblies, and cables that preserve optical performance.
Optical articles, assemblies, and cables include optical waveguides such as optical fibers that transmit optical signals such as voice, video, and/or data information. Optical fibers are drawn from a glass preform/blank and are coated in a manufacturing process. After their manufacture, the optical fibers have a given optical performance level that is relatively sensitive to external forces that can degrade optical performance. Consequently, optical waveguides generally require packaging to protect them from the application of stresses and/or strains that can degrade optical performance. Unfortunately, the packaging of conventional optical waveguides into optical articles, assemblies, and cables often impart stresses that cause unavoidable degradation in optical performance. Likewise, environmental conditions can also degrade optical performance.
The degradation in optical performance between a final state and an initial state can be measured as delta attenuation. Delta attenuation is measured in terms of decibels per kilometer (dB/km) and represents a loss in optical power transmitted along the optical waveguide. A system designer must be concerned with these power losses when designing an optical network. For instance, transmitting/receiving equipment must have a signal with enough power to overcome the power losses, and maintain signal recognition. System designers must also balance optical network power requirements with cost considerations. Generally speaking, optical networks having relatively high losses require more components and/or components rated at higher power levels to overcome the optical network power losses. These additional and/or high power components add undesirable expense to the optical network.
In one embodiment, the present invention is directed to a fiber optic ribbon including a plurality of optical fibers and a joining material. At least one of the plurality of optical fibers having a core, a cladding, and a coating system as described herein. The joining material connects the plurality of optical fibers, thereby forming a planar structure. In preferred embodiments, the fiber optic ribbon has a maximum delta attenuation of about 0.050 dB/km or less for a ribbon optical performance test at a reference wavelength of 1550 nm.
The present invention is also directed to a tube assembly including at least one optical waveguide and a tube. The at least one optical waveguide has a core, a cladding, and a coating system as described herein and is disposed within the tube.
The present invention is further directed to a fiber optic cable including at least one optical waveguide and a jacket. The at least one optical waveguide has a core, a cladding, and a coating system as described herein and is disposed within the jacket.
a–b are plan and cross-sectional views depicting print indicia on the ribbon of
c is a schematic representation depicting a reel having a ribbon wound thereon with a trapezoidal wind shape.
The present invention will now be described more fully hereinafter with reference to the accompanying drawings showing preferred embodiments, of the invention. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that the disclosure will fully convey the scope of the invention to those skilled in the art. The drawings are not necessarily drawn to scale but are configured to clearly illustrate the invention.
The present invention is directed to optical articles, assemblies, and cables that preserve optical performance. Moreover, the optical articles, assemblies, and cables, of the present invention may achieve performance levels that were previously unattainable, for instance, the present invention contemplates acceptable optical performance for wavelengths such as 1625 nm and higher. Likewise, cable engineers have new freedom in designing articles, assemblies, and/or cables using the concepts of the present invention while still maintaining acceptable optical performance. For instance, compared with conventional designs the assemblies and cables of the present invention can have fewer strength members, thinner tube walls and/or jackets, increased packing densities, and/or smaller sizes/diameters. Additionally, articles, assemblies, and/or cables of the present invention advantageously preserve optical performance, i.e., have low delta attenuation, when subjected to manufacturing processes and/or environmental conditions such as temperature cycling. In other words, the articles, assemblies, and cables can withstand increased stress/strain before having significant attenuation.
The concepts of the present invention can be practiced with articles, assemblies, and cables having any suitable optical waveguide 12. For example, suitable optical fibers can be single-mode, multi-mode, pure-mode, erbium doped, polarization-maintaining fiber, large effective area fibers or other suitable types of light waveguides, and/or combinations thereof. Moreover, the packaging of articles, assemblies, and cables according to the present invention can take different forms such as ribbons, stacks of ribbons, tube assemblies, buffered optical waveguides, bundles of optical waveguides, cables, interconnect assemblies, and the like.
Each optical waveguide 12 may include a silica-based core (not numbered) that is operative to transmit light and is surrounded by a silica-based cladding (not numbered) having a lower index of refraction than the core. Additionally, optical waveguide 12 includes coating system 14 having an inner coating 14a and an outer coating 14b. Coating system 14 can also include an identifying means such as ink or other suitable indicia for identification purposes that includes an adhesion agent that inhibits the removal of the identifying means. Moreover, optical waveguide 12 can have any, suitable size or shape. In one embodiment, two or more layers of coloring ink, or other suitable layers, are applied to the optical waveguide 12. Additionally, other advantageous embodiments of the present invention have other substances applied to coating system 14 as will be discussed herein. Inner coating 14a is a relatively soft coating that generally surrounds the cladding and serves to cushion the cladding and core, thereby aiding in preserving optical performance. Suitable inner coatings 14a of coating system 14 are disclosed in U.S. Pat. No. 6,563,996; U.S. patent application Pub. Nos. 2003/0077059 and 20030095770; and U.S. patent application Ser. No. 09/916,536 filed on Jul. 27, 2001, the disclosures of which are incorporated herein by reference. Outer coating 14b is a relatively rigid coating that generally surrounds inner coating 14a of optical waveguide 12. Suitable outer coatings 14b of coating system 14 are disclosed in U.S. patent application Pub. No. 2003/0059188 and U.S. patent application Ser. No. 09/722,895 filed on Nov. 27, 2000, the disclosures of which are incorporated herein by reference. Preferably, coating system 14 includes an inner coating 14a and an outer coating 14b as disclosed in the U.S. patent application filed even date herewith, listing Fabian, et al. as the inventive entity and titled “OPTICAL FIBER COATING SYSTEM AND COATED OPTICAL FIBER,” the disclosure of which is incorporated herein by reference. Suitable optical waveguides of the present invention will be commercially available from Corning Incorporated of Corning, N.Y.
As the skilled artisan will appreciate, the inner coating 14a may be the cured reaction product of an inner coating curable composition. Similarly, outer coating 14b may each be the cured reaction product of an outer coating curable composition. Desirable inner and outer coating curable compositions are given below in Table 1. Curable compositions are formulated such that the amounts of oligomer, monomer, and photoinitiator total 100 wt %; other additives such as antioxidant are added to the total mixture in units of pph. KWS 4131 and BR3741 are oligomers from Bomar Specialties. PHOTOMER 4003, PHOTOMER 4028 and PHOTOMER 3016 fare monomers available from Cognis. PHOTOMER 4003 is ethoxylated(4) nonylphenol acrylate. PHOTOMER 4028 is ethoxylated(4EO/BP) Bisphenol A diacrylate. PHOTOMER 3016 is the diacrylated adduct of Bisphenol A diacrylate with two equivalents of glycidol. TONE M-100 is a caprolactone acrylate monomer available from Dow Chemical. IRGACURE 819 and IRGACURE 814 are photoinitiators available from Ciba Additives. IRGANQX 1035 is an antioxidant available from Ciba Additives.
Besides inks, other substances such as release agents, and/or adhesion promoters may be applied to, or over, coating, system 14 as a further layer. For example, a release substance may be coated over an ink layer so that a matrix material or other joining material can be easily removed from the optical waveguides of assembly 10 without removing the ink layer. For instance, a suitable release agent is available commercially from Zeon of Charlotte, N.C. under the tradename of UVA skin 56A. However, any suitable substance can be added as a further layer to coating system 14. Suitable further layers also include agents for tailoring adhesion, friction, or static characteristics. In one advantageous embodiment, two ink layers are applied to optical waveguide 12 for identifying 24 loose fibers in a tube. For instance, a black tracer is applied as a first layer and a second continuous colored layer is applied over the tracer for identifying a second set of twelve optical waveguides.
Joining material 16 connects the individual optical waveguides in an elongate structure. Joining material 16 is preferably a radiation-curable matrix material such as 950-706 available from DSM Desotech Inc. of Elgin Ill.; however, other suitable materials can be used. For instance, other suitable UV curable materials include, cationic or cationic/free radical blends. Additionally, thermoplastics, thermosets, other polymers, elastomers, expoxies, hot melt glues, or other joining materials may also be used. Preferably, joining material 16 has a coefficient of thermal expansion that is compatible with the coefficient of thermal expansion for the optical waveguides. Embodiments according to the present invention can use a joining material 16 that has enhanced flame and smoke retardance since typical radiation-curable materials generally are susceptible to burning that can cause difficulty in meeting flame and smoke ratings for plenum and riser applications. For instance, joining material 16 can be a polymer such as flame-retardant PVC or a LSZH material. Likewise, radiation-curable materials or other suitable joining material 16 may include flame retardant components such as aluminum trihydrate (ATH) in their formulations.
Manufacturing steps during packaging such as ribbonizing and/or other conditions such as environmental conditions can cause residual stress and/or strains on the assembly. Unlike the present invention, these residual stresses and/or strains can cause significant degradation in the optical performance of conventional articles, assemblies, and/or cables. By way of example, a conventional unprinted optical fiber ribbon has a given optical attenuation (dB/Km) at a specified reference wavelength. However, after printing on the conventional optical fiber ribbon the optical attenuation (dB/Km) at the same reference wavelength may have a relatively large increase while on the ribbon winding spool. In other words, the optical performance of the conventional optical fiber ribbon is degraded by the printing process, thereby causing a relatively high delta attenuation.
How the printing process can affect conventional ribbons using optical fibers with conventional coating systems is known. For instance, U.S. Pat. No. 6,064,789 discloses that the delta attenuation between printed ribbons and unprinted ribbons can be decreased by using predetermined print pitch (characters/cm) and/or increasing spacing between the printed indicia. Additionally, U.S. Pat. No. 6,360,044 discloses that delta attenuation between printed ribbons and unprinted ribbons can be improved by printing randomly spaced ink shapes on an article used for the transmission of optical signals. Thus, a common manufacturing step such as printing can cause significant delta attenuation depending on printing conditions.
With the known effects of printing on a ribbon, a ribbon optical performance test was, designed to subject ribbons to severe printing conditions. The severe conditions of the ribbon optical performance test serve to quantify optical performance of a ribbon design, i.e., how susceptible the optical performance of the unit is to stress and/or strains. The ribbon optical performance test was performed for both single-mode and multi-mode ribbons. Additionally, the tested ribbons 10 were hybrid ribbons. In other words, the hybrid ribbons had groups of both conventional ribbon assemblies and ribbon assemblies according to the present invention in predetermined combinations within a given ribbon. Consequently, the hybrid ribbons that were tested minimize any unknown differential process variations possibly induced among ribbon lengths and provided a higher reliability for statistical comparison purposes. Moreover, the results of the ribbon optical performance test are presented as a maximum, or an average, delta attenuation for similar assemblies at the same reference wavelength. Likewise, the other ribbon experiments discussed herein also used hybrid ribbons for minimizing process variations, thereby enhancing the statistical analysis of the data.
The ribbon optical performance test tested twelve fiber ribbons joined by a, radiation-curable matrix available from DSM Desotech Inc. of Elgin, Ill. under the tradename Cablelite 950-706. Cablelite 950-706 has a tensile strength of about 28 Mpa, an elongation to break of about 31%, and a modulus of about 770 Mpa. The tested ribbons all used the same standard geometry for a twelve fiber ribbon, namely, a thickness of 0.310 mm and a width of 3.12 mm. Likewise, each optical fiber of the tested ribbons had a core/cladding outer diameter of about 125 microns, an inner coating diameter of about 190 microns, an outer coating diameter of about 245 microns, and an ink layer with a nominal diameter of about 258 microns. The ink used is available from DSM Desotech Inc. under the tradename LTS.
As used herein, the ribbon optical performance test requires that an unprinted ribbon 10 be wound onto a suitable reel used throughout the test using similar wind conditions such as wind tension, speed, and wind pitch. Moreover, the test requires that a suitable length of ribbon so that the measured signal to noise ratio is not an issue. For instance, a 1 kilometer sample of ribbon is wound with a tension of, for example, 300 grams at a speed of 200 meters per minute with a trapezoidal wind shape 19b as shown in
As an example, a suitable reel has a hub with a diameter of about 225 mm and about 300 mm between reel flanges. After the ribbon is wound on the reel, the optical attenuation at one or more predetermined reference wavelengths is measured for each optical waveguide of ribbon 10 while it is on the reel. Moreover, the unprinted optical attenuation measurement should occur after any transient optical response from manufacturing the ribbon dampens, for example, the experimental measurement results presented were performed within 24±6 hours of the manufacture of ribbon 10.
Thereafter, as shown in
Bars 21 and 22 respectively represent an average and a maximum delta attenuation for large effective area single-mode ribbons 10 according to the present invention measured at a reference wavelength of 1625 nm. Likewise, bars 25 and 26 respectively represent an average and a maximum delta attenuation for the same ribbons at a reference wavelength 1550 nm. The ribbons representing bars 21, 22, 25, and 26 had a coating system 14 using inner coating A and the outer coating of Table 1. As shown for both reference wavelengths, the average and maximum delta attenuation for the ribbons of the present invention are essentially about 0.000 dB/km; however, non-zero values for bars 21, 22, 25, and 26 are shown for illustrative purposes. Specifically, at 1625 nm the average; and maximum attenuations, bars 21 and 22, were respectively −0.004 dB/Km and 0.005 dB/km for the ribbon optical performance test. At 1550 nm, the average and maximum attenuations, bars 25 and 26, respectively were −0.003 dB/Km and 0.005 dB/km for the ribbon optical performance test. The relatively small, and even negative attenuation values, indicate that the measurements are within the test noise floor.
On the other, hand, the average delta attenuation for the conventional single-mode large effective area ribbons at both wavelengths was significantly higher as shown in
Average and maximum delta attenuation measurements were also performed for a conventional single-mode ribbon to illustrate the sensitivity of the single-mode large effective area assemblies. At 1550 nm, the average and maximum delta attenuations for a conventional single-mode ribbon respectively were 0.027 dB/Km and 0.062 dB/km for the ribbon optical performance test. Stated another way, the average and maximum delta attenuation values for the conventional single-mode large effective area ribbon assemblies is more than double the respective attenuation values of the conventional single-mode ribbon.
The severe printing conditions of the ribbon optical performance test had little, or no effect, on the average delta attenuation for the large effective area single-mode ribbons of the present invention. On the other hand, the conventional ribbons had significant delta attenuation that generally increased as the wavelength increased. In other words, the ribbons of the present invention preserved the optical performance by more than an order of magnitude at reference wavelengths of 1625 nm and 1550 nm in the ribbon optical performance test. Table 2 is a summary of the test results for the ribbon optical performance test.
Articles, assemblies, and/or cables using ribbons according to the present invention can take advantage of this ability to preserve optical performance in a variety of ways. Stated another way, configurations and designs that were difficult, if not impossible, to qualify previously for given wavelength performance levels are now possible with the present invention. For instance, assemblies of the present invention can have suitable performance levels at wavelengths such as 1625 nm, 1650 nm and higher, whereas the conventional assemblies have significant power losses. As another example, cable designs previously suitable for single-mode waveguides can now employ multi-mode waveguides with suitable optical performance.
The ribbon optical performance test was also performed on multi-mode ribbons.
Bars 31 and 32 respectively represent an average and a maximum delta attenuation for multi-mode optical fibers of ribbon 10 according to the present invention measured at reference wavelengths of 850 nm. Likewise, bars 35 and 36 respectively represent an average and a maximum delta attenuation for the same ribbons at a reference wavelength of 1300 nm. As shown, average and maximum delta attenuations for the ribbons having multi-mode optical fibers according to the present invention were relatively low at both reference wavelengths compared with the conventional multi-mode ribbon. Specifically, at 850 nm the average and maximum delta attenuations bars 31 and 32, were respectively 0.015 dB/km and 0.090 dB/km. At 1300 nm, the average and maximum attenuations, bars 35 and 36, were respectively 0.006 dB/km and 0.077 dB/km.
On the other hand, the conventional multi-mode ribbons had significant average and maximum delta attenuations for both reference wavelengths. Bars 23 and 24 respectively represent an average and a maximum delta attenuation of 0.310 dB/km and 0.919 dB/km for conventional multi-mode ribbons measured at a reference wavelength of 850 nm. Likewise, bars 37 and 38 respectively represent an average and a maximum delta attenuation of 0.270 dB/km and 0.760 dB/km for the same ribbons at a reference wavelength of 1300 nm. Table 3 is a summary of the test results for the multi-mode ribbon optical performance test.
The conventional multi-mode ribbons had relatively elevated levels of average and maximum delta attenuations for the ribbon optical performance test. With these performance levels conventional multi-mode ribbons may be difficult to package with acceptable optical performance for inhibiting power losses of an optical network. Conversely, the severe printing conditions of the ribbon optical performance test had relatively little effect on the delta attenuations for the multi-mode ribbons of the present invention. Stated another way, the tested multi-mode ribbon had about an order of magnitude reduction in delta attenuation compared with the conventional multi-mode ribbon.
As shown, both the single-mode and multi-mode ribbons of the present invention had significant improvements compared with their conventional counterparts. Generally speaking, the average delta attenuation improvement for both single-mode and multi-mode embodiments was about an order of magnitude or more compared with their respective conventional counterpart ribbons under the ribbon optical performance test. Likewise, the maximum delta attenuation improvement for both single-mode and multi-mode embodiments was about an order of magnitude or more compared with their respective conventional counterpart ribbons.
The experimental results discussed in the ribbon optical performance tests are exemplary and other embodiments of the present invention may also provide excellent optical performance. For instance, assemblies according to the present invention can have other coating systems 14 that provide similar benefits. Likewise, the coating systems 14 are suitable for other core/cladding configurations than those tested. Hence, single-mode ribbons 10 of the present invention have an average delta attenuation for the ribbon optical performance test that is preferably about 0.020 dB/km or less, more preferably about 0.010 dB/km or less, and most preferably about 0.005 dB/km or less at a reference wavelength of 1550 nm. Likewise, single-mode optical assemblies of the present invention have a maximum delta attenuation for the ribbon optical performance test that is preferably about 0.050 dB/km or less, more preferably about 0.030 dB/km or less, and most preferably about 0.020 dB/km or less at a reference wavelength of 1550 nm.
Furthermore, the results presented illustrate that the advantages of the present invention are beneficial for multi mode assemblies such as 50 micron multi-mode assemblies. However, the results for the ribbon optical performance test are exemplary and other core/cladding configurations such as a 62.5 micron multi-mode ribbon may have other beneficial results. Accordingly, multi-mode ribbons 10 have an average delta attenuation for the ribbon optical performance test that is preferably about 0.300 dB/km or less, more preferably about 0.200 dB/km or less, and most preferably about 0.100 dB/km or less at a reference wavelength of 850 nm. Likewise, multi-mode optical assemblies of the present invention can have a maximum delta attenuation for the ribbon optical performance test that is preferably about 0.500 dB/km or less, more preferably about 0.300 dB/km or less, and most preferably about 0.100 dB/km or less at a reference wavelength of 850 nm. At a reference wavelength of 1300 nm, multi-mode optical assemblies of the present invention have an average delta attenuation, for the ribbon optical performance test that is preferably about 0.200 dB/km or less, more preferably about 0.150 dB/km or less, and most, preferably about 0.100 dB/km or less and/or a maximum delta attenuation that is preferably about 0.400 dB/km or less, more preferably about 0.200 dB/km or less, and most preferably about 0.100 dB/km or less.
Other changes in conditions are possible for investigating the optical degradation, i.e., the delta attenuation, of articles, assemblies, and/or cables. One frequent environmental change experienced during service is the change in temperature that can degrade optical performance. The change in temperature can cause differential stain and/ stress on the optical articles, assemblies, or cables, thereby causing delta attenuation. Therefore, assemblies were also temperature cycled in order quantify the performance gains of the present invention. As before, the multi-mode assemblies according to the present invention included optical fibers 12 with a coating system 14. The assemblies tested and presented had the same ribbon geometry and coating system 14 as used in the ribbon optical performance test. Specifically, coating system 14 for the tested multi-mode portions had inner coating A and the outer coating as specified in Table 1.
As used herein, a ribbon temperature performance test requires that a ribbon of a suitable length be wound onto a suitable reel in a manner as described above for the ribbon optical performance test. However, for comparative purposes, it is only important that the ribbons are wound on a reel of the same design under the same wind conditions. Then the ribbon package is placed into a thermal chamber. The temperature within the thermal chamber is cycled while measuring delta attenuation at predetermined times after the package reaches thermal stability at the predetermined temperature.
Specifically, after winding, preferably using a trapezodial wind package, the ribbon package is placed in a thermal chamber at 23° C. and the ribbon package is allowed to reach a steady-state temperature so that a baseline attenuation measurement can be taken at a predetermined reference wavelength. The temperature chamber is taken down to −40° C., then the ribbon package completes two temperature cycles from −40° C. to 70° C. as will be defined. Thereafter the ribbon package is held at 85° C. for five days of heat aging followed by two more temperature cycles of −40° C. to 70° C. and then the temperature is ramped back down to 23° C. for a final attenuation measurement. As used herein, a temperature cycle begins at 23° C. and is ramped down to about −40° C. over a four-hour period then this temperature plateau is held, or dwelled, for four hours after which, an attenuation measurement is taken. Next, the temperature is ramped up to 70° C. over a four-hour period, then this temperature plateau is held for four hours after which an attenuation measurement is taken, thereby completing one temperature cycle. The second temperature cycle begins while ramping the temperature back down to −40° C. over a four-hour period. After the second temperature cycle is completed, a heat aging test is performed at 85° C. and held for five days and then an attenuation measurement is taken. Thereafter, the temperature is ramped back down to 23° C. so the last two temperature cycles can be performed followed by ramping the temperature back down to 23° C. for a final attenuation measurement. Delta attenuations for temperature cycling are calculated by taking the attenuation measurement after the dwell times at each predetermined point and subtracting the baseline attenuation (initial attenuation at 23° C.) at the same reference wavelength.
For the most part, the delta attenuation is elevated for both conventional ribbons. However, the delta attenuation for the conventional large effective area ribbons is the highest, thereby showing that they are more sensitive to the temperature performance test. On the other hand, the single-mode ribbons of the present invention show that they preserve optical performance in the ribbon temperature performance test.
In this particular experiment, the ribbons tested had relatively high levels of initial attenuation, thus, during temperature cycling the stress was relieved and the delta attenuation was negative.
The experimental results discussed in the ribbon temperature performance tests are exemplary. Moreover, embodiments of the present invention such as different core/claddings and/or coating systems 14 may have other values while still providing excellent optical performance. For instance, single-mode optical assemblies of the present invention have a maximum delta attenuation for the ribbon temperature performance test that is preferably about 0.0300 dB/km or less, more preferably about 0.0250 dB/km or less, and most preferably about 0.020 dB/km or less at a reference wavelength of 1550 nm.
Optical assemblies of the present invention can also employ other geometry, materials, and/or constructions than those depicted in ribbon 10. For instance, as depicted in
U.S. patent application Ser. No. 10/159,730 filed on May 31, 2002, the disclosure of which is incorporated herein by reference, discusses ribbons that influence the fracture point of the secondary matrix, thereby reducing the likelihood of wings. Specifically, ribbon 70 has a non-uniform thickness such as one or more bulbous end portions 74a, 74c. End portions 74a, 74c each having a respective maximum thickness Ta,Tc, which is greater than a medial thickness Tb, that generally occurs at a distance r from the edge of ribbon 70 for influencing the initiation of a fracture point in a unitized ribbon. Suitable values of range r generally dispose the maximum thickness Ta, Tc over a cross-section of edge fiber 12a. Additionally, ribbons can have end portions with shapes that are different than illustrated, or can have a single bulbous end portion.
Ribbon 70 is useful in larger assemblies where end portions 74a, 74c create a preferential tear portion in ribbons having subunits. For instance,
Additionally, ribbons having a uniform thickness can also have a preferential tear portion such as a recess or notch 93 having a suitable width, depth, or shape adjacent to the interface between subunits 92 of the present invention as shown in ribbon 90 of
Additionally, unitized ribbons can be constructed to separate in a specific order of separation. U.S. patent application Ser. No. 10/411,406 filed on Apr. 10, 2003, the disclosure of which is incorporated herein by reference, discusses ribbons that can separate in a preferential separation sequence for connectorization or splicing purposes. For instance,
Furthermore, the concepts of a preferential separation sequence between ribbon-units can employ subunits having other suitable geometry. For instance,
As shown, second joining material 127 includes at least one preferential tear portion disposed adjacent to ribbon interfaces E/F and F/G. Specifically, preferential tear portions of second joining material are recessed portions 127a having a generally concave shape that is offset at a distance d from the ribbon-unit interface. For example, distance d is between about 125 μm and about 300 μm, but other suitable distances can be used. Additionally, recessed portions 127a can have other shapes, widths, and/or depths. Additionally, the top and bottom of ribbon 120 can have different numbers or shapes of recessed portions 127a. In this case, recessed portions 127a are generally symmetrical about axis A—A at the ribbon-unit interface.
Still further, the concepts of a preferential separation sequence between ribbon-units can employ more than two joining materials. For instance,
Other constructions of ribbon assemblies are also possible using the concepts of the present invention. In other embodiments, the joining material modulus characteristics of ribbon assemblies can be controlled within predetermined ranges and/or ratios for enhancing separation characteristics of the assembly. For instance, U.S. Pat. No. 6,253,013 discusses ribbon assemblies having a subunit/common matrix modulus ratio that is about 1.5 or greater, the disclosure of which is incorporated herein by reference.
Ribbon assemblies can also include a marking indicia for identification purposes. For instance, alpha/numeric characters can be printed on the outer surface or between matrix layers of ribbon 10. In another embodiment, ribbon 10 can include identifying information about the ribbon conveyed by a series of colored regions such as a ribbon number and/or the type of optical waveguides in the ribbon as discussed in U.S. patent application Ser. No. 09/886,559 filed on Jun. 21, 2001, the disclosure of which is incorporated herein by reference. In other embodiments, ribbon 10 has a radiation markable section that has a radiation, reactive ingredient compounded with a base matrix material as discussed in U.S. Pat. No. 6,370,304, the disclosure of which is incorporated herein by reference.
Still other ribbon constructions are within the scope of this invention.
Moreover, assemblies of the present invention such as ribbons can be used in larger assemblies and/or cables. One such assembly is constructed by stacking at least one ribbon of the present invention with other ribbons, thereby forming a dense array of optical fibers. Ribbon stacks can have various configurations or suitable numbers of optical waveguides such as twelve, thirty-six, seventy-two or multiples thereof; however, other suitable ribbon stacks are possible.
As known in the art, ribbon stacks can also include a pre-wet layer of grease between the ribbons to facilitate movement between ribbons, for instance, during bending. Additionally, the pre-wet layer holds the ribbons of the stack together, through surface tension, thereby providing stack integrity. Other ribbon stack embodiments using the concepts of the present invention are possible. For instance, a slip layer between ribbons of a stack can be wet or dry such as oils, graphite, talc, silicone mircospheres, Teflon® powders, or the like.
Additionally, grease pre-wet layers can include suitable fillers. Fillers for the pre-wet layer can influence the viscosity of the pre-wet layer and/or reduce the material costs. Conventional ribbon stacks typically use a pre-wet layer having fillers that do not cause elevated levels of stress or strain on the optical ribbons. For example, U.S. patent application Pub. No. 2002/0102079 discusses how the particle size of the fillers affects the optical performance of a ribbon. Unlike conventional ribbon stacks, the ribbon stacks according to the present invention are less sensitive to stress and/or strains caused by relatively large particles, or other media, in the pre-wet layer. Thus, the percentage of fillers and/or the particle size of the filler may be increased in a pre-wet layer, while still providing suitable optical performance.
One type of a dry ribbon stack has a semi-solid film disposed on an outer surface of the ribbons as disclosed in U.S. patent application Ser. No. 10/325,539 filed on Dec. 20, 2002, the disclosure of which is incorporated herein by reference.
Ribbon stacks can use other methods for holding the ribbons of the stack together to provide stack integrity. For instance, ribbon stack 170, or portions of ribbon stack 170, can also have a binder or a stitch therearound, additionally other types of binders are possible. For example, a binder 174, or stitched threads, may be used to hold the entire group of ribbons together as depicted. Binders 174 can include threads, yarns, tapes, or other suitable materials for holding at least two optical waveguides together. Binders 174, or stitched threads, may also contain water-swellable materials and/or be colored for identification purposes. In other embodiments, the binder or stitch can hold less than all of the ribbons of the stack together. For example, as depicted in
Other ribbon stacks are also possible. For instance, any of the ribbon assemblies can be used in a stack. Additionally, different types of ribbons can be used in a single stack or a portion of a stack. Stacks can also have optical waveguides arranged, or stacked, in a common connecting material, thereby providing a monolithic stack. For example,
The optical performance and the temperature cycling tests show that optical articles, assemblies and cables according to the present invention can handle higher levels of stress and/or strain without degrading optical performance. In other words, assemblies and/or cable configurations can allow ribbon 10, or other configurations of optical waveguides, to experience higher levels of stress and/or strain without significant increases in attenuation levels. Consequently, assembly and/or cable designs can have smaller diameters, reduced tensile enhancement, i.e., fewer or smaller strength components, relaxed stranding requirements, wide ranges of excess ribbon length (ERL), and/or a higher optical waveguide packing density while maintaining reliable optical performance. Likewise, optical waveguides such as optical fibers can have wider ranges of excess fiber length (EFL).
By way of example, one or more ribbons can be used as a portion of a ribbon tube assembly. Moreover, tube assemblies with ribbons having optical waveguides 12 disposed in high stress locations are advantageous. For instance, in one embodiment ribbons 10 of the ribbon stack 170 have optical waveguides 12 disposed solely as end optical fibers A,B. End optical fibers A,B typically experience the highest levels of stress and/or strain when, for example, the ribbon contacts the tube wall during bending. In other embodiments, all of the optical waveguides of the ribbon tube assembly are optical waveguides 12. Additionally, tube assemblies can be used as a portion of larger assemblies such as monotube cables, stranded tube cables, or drop cables.
Like the pre-wet layer, conventional tube assemblies typically use a thixotropic material composition that does not cause elevated levels of stress and/or strain on the optical waveguides. For example, conventional tube assemblies use thixotropic materials having specific viscosity ranges so that at relatively low temperatures the optical performance is acceptable. A typical thixotropic material for conventional tube assemblies is available from the Stewart Group of Charlotte, N.C. under the tradename K550. Additionally, thixotropic materials suitable for conventional tube assemblies may include inorganic fillers such as silica fillers for reducing cost and/or influencing the viscosity of the thixotropic material; however, fillers may be organic such as hollow (expanded or unexpanded) or solid thermoplastic microspheres such as Expancel® commercially available from Expancel, Inc. of Duluth, Ga. Thixotropic materials may also include fillers for flame-retardant purposes such as magnesium hydroxide or aluminum trihydrate (ATH). However, the silica, or other fillers, must have a relatively fine particle size for achieving acceptable optical performance in conventional tube assemblies. In other words, if the particle size of the filling material is too large the particles can cause undesirable optical attenuation in conventional tube assemblies.
On the other hand, the articles and assemblies of the present invention can handle increased levels of stress and/or strain. Consequently, tube assembly 100 can use thixotropic materials that would have caused elevated and/or unacceptable levels of optical attenuation in conventional tube assemblies. By way of example, assemblies and/or cables of the present invention can have thixotropic materials with lower viscosities, fillers having larger particle sizes, a wider range of filler particle density, irregular shapes, and/or increased particle hardness. However, thixotropic materials have the disadvantage of being relatively messy and must be cleaned from the optical waveguide before optical connection or splicing. Consequently, materials other than thixotropic materials are useful for at least partially filling a tube assembly.
U.S. Pat. No. 6,374,023, the disclosure of which is incorporated herein by reference, discusses filling materials having thermoplastic polymeric molecules that have bonded, thereby forming a three-dimensional network. Generally speaking, unlike thixotropic materials, these filling materials having three-dimensional networks are dry materials that are easily and cleanly removed from optical waveguides. Furthermore, assemblies using filling materials having three-dimensional networks may eliminate the tube or be used as a friction element within the tube as discussed in U.S. patent application Ser. No. 09/966,646 filed on Sep. 28, 2001, the disclosure of which is incorporated herein by reference. In other words, the material forms a soft housing such as a buffer tube about the optical waveguide 12.
Additionally, tube assemblies according to the present invention may have a relatively dense packing of ribbons within the tube. Stated another way, a ribbon packing density within a tube can be relatively high without degrading optical performance because assemblies such as ribbons can have more contact with the inner wall of the tube during, for example, bending. Assemblies of the present invention achieve their packing density, for example, by increasing the allowable number of ribbons within a tube, using thinner tube walls, and/or using ribbons having a smaller cross-sectional area.
The ribbon packing density can be calculated as the area occupied by the ribbons divided by the area circumscribed by the outer diameter of the tube, which yields a number less than unity. The ribbon packing density can be improved by using a tube assembly having less free space between the ribbon stack and the tube wall, using a tube having a thinner wall thickness, and/or using stack profiles that conform with the tube shape. Likewise, an optical fiber packing density can be calculated. The optical fiber packing density can be calculated as the area occupied by the optical waveguides divided by the area circumscribed by the outer diameter of the tube, which yields a number less than unity. Generally speaking, the ribbon packing density is the preferred way to compare ribbon tube assemblies. For embodiments that do not employ ribbons, the optical waveguide packing density is a way in which assemblies may be compared. Optical waveguide packing density is a ratio of the area occupied by the optical waveguides divided by the outer dimension of a given component.
Illustratively, a tube assembly houses eighteen ribbons. 10 each having twelve uncolored optical fibers 12 with a nominal outer diameter of 245 microns. Given ribbons having a width of 3.12 mm and a height of 0.310 mm the total area for all eighteen ribbons can be calculated as about 17.41 mm2. The tube has an ID of about 9.0 mm and a tube wall thickness of about 1.0 mm for an OD of about 11 mm for an occupied area of about 95 mm2. Thus, in this case, the ribbon packing density is about 0.18. The present invention allows high ribbon packing densities while still maintaining optical performance. Using the same ribbon and tube dimensions as given above,
Furthermore, the compression of dry insert 274 can provide a portion or essentially all of the coupling force between dry insert 274 and tube 275. Compression of dry insert 274 is actually a localized maximum compression of dry insert 274. The localized maximum compression of dry insert 274 occurs at the corners of the ribbon stack across the diameter. Calculating the percentage of compresssion of dry insert 274 in
Additionally, dry tube assembly 270 can include a binder 273 for securing dry insert 274 about optical waveguide 12 as discussed in, U.S. patent application Ser. No. 10/448,874 filed on May 30, 2003, the disclosure of which is incorporated herein by reference. Specifically, at least one binder 273 is surrounded by a polymer layer. In the case of dry tube assembly 270 the polymer layer is tube 275. The polymer layer, i.e., tube 275, at least partially melts the at least one binder 273 when the polymer layer is extruded thereover, thereby at least partially bonding the at least one binder with the polymer layer. Consequently, when the craftsman opens, or removes the tube formed by the polymer layer, binder 273 at least partially comes off with the polymer layer because it is at least partially bonded therewith. This bonding between binder 273 and the polymer layer generally eliminates the time consuming step of removing binder 193 from the dry insert when accessing the optical waveguides. In other embodiments, the polymer layer can essentially melt binder 273. Moreover, a binder that melts when a polymer layer is extruded thereover can be used in other suitable locations and/or with other assemblies.
Tube assemblies of the present invention may also have wider ranges of excess ribbon length (ERL). ERL is the percent difference between the ribbon length minus the length of tube, or other article, that houses the ribbon. For example, during bending of a tube assembly, the ribbons reposition themselves to an inner diameter of the bend and may contact the inner wall of a tube if there is not a sufficient ERL, this contact may cause optical degradation. However, a slightly positive ERL may reduce this effect during bending. However, too high an ERL value can cause undulations within the tube that have a similar effect by causing the ribbons to contact the tube wall. Additionally, a positive ERL in an assembly generally allows the assembly to carry a tensile stress without transferring the stress to the ribbons. Embodiments according to the present invention can have wider ranges of ERL such as between about zero percent and about 0.25 or greater percent ERL because the assemblies are not as sensitive, for example, to the forces cause by the ribbons contacting the tube wall.
Tubes of the assemblies are preferably made from a dielectric polymeric material such as a polyethylene, a polypropylene, a polyvinylchloride (PVC), or a PBT. Moreover, polymer tubes along with other components of the cable, can be formed from flame-retardant polymeric materials, thereby improving flame-retardant properties of the cable. However, other suitable materials such as semi-conductive or conductive materials such as steel or copper can be used where suitable such as in submarine applications. Other suitable materials for the tube can include composite materials. Composite materials may include suitable fillers in a polymer material for reducing post-extrusion shrinkage. Suitable fillers include clay, nano-carbon tubes, titanium dioxide (TiO2), or like fillers.
Filling, the tube assembly with a thixotropic material provides other benefits such as aiding in maintaining the tube shape before the tube is cooled and solidifies. Since dry tube assemblies are generally not filled with a thixotropic material the tube may deform or collapse, thereby forming an oval shaped tube instead of a round tube. U.S. patent application Ser. No. 10/448,509 filed on May 30, 2003, the disclosure of which is incorporated herein by reference, discusses dry tube assemblies where the tube is formed from a bimodal polymeric material having a predetermined average ovality. As used herein, ovality is the difference between a major diameter D1 and a minor diameter D2 of tube 280 (
In other embodiments, the tube can have one or more strength members or ripcords within a tube wall, and/or a water-swellable coating thereon or embedded therein as discussed in U.S. Pat. Nos. 5,388,175 and 6,195,486, the disclosures of which are incorporated herein by reference. The tube may also be a co-extrusion of two or more materials for tailoring tube properties and/or reducing material costs. Other tube assemblies according to the present invention can include other components such as electrical components inside the tube or within the tube wall. Other tube assemblies can also have at least one removable section or weakened portion. An example of which is discussed in U.S. Pat. No. 5,970,196, the disclosure of which is incorporated herein by reference.
Other tube assemblies are also within the scope of the present invention. For instance,
Tube assemblies according to the present invention having at least one optical waveguide 12 can be used as a portion of a cable such as a monotube cable, a stranded tube cable, or a drop cable. Moreover, the at least one optical waveguide 12 of the tube assembly may be a portion of a ribbon, an optical waveguide bundle, a tight-buffered fiber or ribbon, a bare fiber, or other suitable configuration.
Generally speaking, cables having at least one tube assembly include a sheath system disposed around the tube assembly. The sheath assembly includes at least one jacket and other optional components such as tensile strength, members, anti-buckling members, anti-shrink members, ripcords, tapes, binders, and/or armor. Using these components a multitude of different cable configurations are possible. The following cable embodiments are representative cables using the concepts of the present invention.
In this embodiment, strength members 305 are disposed adjacent to water-swellable tape 303. Besides being disposed radially outward of tube 307, strength members may have other suitable locations such as within the tube or jacket wall. Strength members 305 may be reinforced plastic rods that provide both tensile strength and anti-buckling resistance for an all-dielectric construction. By way of example, suitable reinforcement for the strength members can be glass, aramid, or fiberglass materials for respectively forming glass-reinforced plastic (GRP), aramid reinforced plastic (ARP), or fiberglass reinforced plastic rods. Additionally, strength members can have suitable shapes and sizes for the particular cable design. Moreover, embodiments of the present invention can use other materials for strength members, for instance, other dielectric, semi-conductive, or conductive materials. Suitable dielectric strength members include flexible fiberglass rovings, aramid yarns, and other like materials. Suitable conductive strength members may include steel, copper, copper-cladded steel, or other suitable materials. Additionally, semi-conductive strength members such as carbon fibers are also possible. As depicted, strength members 305 are configured for a preferential bend characteristic. However, other embodiments can have strength members arranged for a non-preferential bend characteristic (
Cable 300 also includes ripcord 306 that is preferably disposed radially inward of jacket 308 for aiding in the removal of the same. Suitable ripcords are made from materials such as PBTs, polyesters, and polypropylenes. Ripcords of the present invention may be disposed on a tape or formed from a metallic material having surface roughness as discussed in U.S. patent application Ser. No. 10/036,027 filed on Dec. 26, 2001, the disclosure of which is incorporated herein by reference. Additionally, ripcords are useful for ripping other layers of an assembly such as a tape, film, or armor. However, the ripcord should have suitable characteristics for ripping the intended material without breaking.
Jacket 308 is preferably a polymeric material such as polyethylene, polypropylene, PVC, PBT, or other suitable polymers. The polymeric material can comprise blends, additives, and fillers. In plenum and riser applications, jacket 308 is a suitable flame-retardant material. Suitable flame-retardant materials include polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), flame-retardant polyethylene (FRPE), but other suitable flame-retardant materials can be used. In flame-retardant embodiments, other components are also preferably constructed from flame-retardant materials. Additionally, jackets, tubes, or other polymeric flame-retardant components may include a reduced level of a hydrated inorganic filler in a polymer blend that includes a polymerization or copolymerzation product of one or more ethylenically unsaturated monomers and an aliphatic polyketone as discussed in U.S. Pat. No. 6,025,422, the disclosure of which is incorporated herein by reference.
Jackets as well as other polymer components can also include other suitable additives or fillers for shrinkage control, adhesion characteristics, and/or cost reductions. One additive may be a fungicide for inhibiting the growth of fungus. Additionally, polymer components requiring resistance to fungus in the absence of a fungicide, may be formed from an extruded blend of a nonplasticized PVC and ether-based polyurethane as discussed in U.S. Pat. No. 6,057,018, the disclosure of which is incorporated herein by reference. Additionally, jackets according to the present invention can also have a reduced wall thickness because the optical assemblies can tolerate larger stresses and/or strains, from crushing, impacts, or tensile forces without degrading optical performance of the assembly.
The plurality of strength members 315 are preferably flexible fiberglass strength members helically stranded in a single layers about tube assembly 311; however, the strength members may be disposed in two contra-helically stranded layers. In other embodiments, the strength members 315 include water-swellable materials for blocking the migration of water near the strength members. The uniform placement of the strength members results in a cable having a non-preferential bend characteristic. Ripcord 316 lies radially inward of jacket 318. Additionally, the tube of tube assembly 311 and jacket 318 are formed from suitable materials for meeting desired plenum or riser ratings. Cables such as cable 310 may take other forms such as having tight-buffered or bare optical waveguides 12, instead of ribbons within the tube. Likewise, other embodiments can include profiled ribbon stacks within the tube as discussed previously. Additionally cables may also have other configurations that include armor, flame-retardant tapes or polymer materials, and/or electrical components.
Delta attenuation caused by a cabling manufacturing process was also examined. Specifically, a cabling performance test was conducted on a cable similar to cable 300 having eighteen multi-mode ribbons 10 and a conventional cable. More specifically, the cables tested each respectively had eighteen twelve-fiber ribbons. The delta attenuation (dB/km) results for the cabling performance test are summarized in Table 6. As shown, the tested cable according to the present invention had about one-third the delta attenuation as a similar conventional cable during the cable manufacturing process. Additionally, in service a cable experiences a total delta attenuation. In other words, the total delta attenuation is the sum of delta attentuations due to individual components such as cable manufacturing component and an environmental component. Thus, embodiments of the present invention are suitable for use where high levels of reliability and performance are required. Moreover, cables of the present invention may be specified with performance levels such as cabling delta attenuation less than 0.300 dB, and more preferably less than 0.200 dB for multi-mode cables.
In other embodiments, the sheathing system of any of these cables can have other suitable configurations. For instance,
Additionally, one or more tube assemblies of the present invention can be stranded to form other cable designs of the present invention.
Another stranded tube cable 380 is depicted in
The concepts of the present invention are also useful with other assemblies in other cable designs. Specifically, assemblies-having optical waveguides 12 can include slotted core cables (SC) and/or U-shaped carriers.
Ribbons of the present invention may also be used in other cable configurations that utilize relatively low ribbon counts. For instance,
Another embodiment is shown in
Another cable 430 according to the present invention is depicted in
Articles, assemblies, or cables of the present invention can also include one or more suitable connectors. Suitable connectors include SC, FC, duplex, and MTP; however, other optical connectors may be used.
Especially advantageous embodiments of the present invention also include ribbons and interconnect assemblies employing the concepts of U.S. patent application Ser. No. 09/943,996, the disclosure of which is incorporated herein by reference. The '996 patent application is directed to, among other things, selecting optical waveguides having predetermined characteristics for minimizing insertion losses for interconnect assemblies such as ribbons, pigtails, and interconnect cables.
In this case, assembly 450 has at least one optical waveguide 12 selected using a predetermined range of optical waveguide characteristics for improving the insertion loss of assembly 450. As shown in
In another advantageous embodiment, optical waveguides are selected and processed to have a low skew in optical propagation time for the signal as discussed in U.S. Pat. No. 5,768,460, the disclosure of which is incorporated herein by reference. For instance, in one embodiment the skew in optical propagation time for signals transmitted over the optical waveguides of the ribbon assembly is less than 1.0 psec/m.
Other configurations and/or manufacturing steps can cause delta attenuation of optical waveguide 12. By way of example, buffering optical waveguides can cause increases in delta attenuation.
Assembly 470 may also include an interfacial layer 471 between optical waveguide 12 and buffer layer 472 such as disposed over coating system 14. Interfacial layer 471 (not visible) acts as a slip layer for aiding in stripping of the buffer layer 472 from assembly 470. For instance, interfacial layer 471 can include a non-reactive solid lubricant in particulate form dispersed in a cross-linked film-forming binder as discussed in U.S. Pat. No. 5,408,564, the disclosure of which is incorporated herein by reference. Another advantageous embodiment is discussed in U.S. patent application Pub. No. 2002/0102078, the disclosure of which is incorporated herein by reference. In particular, the disclosure discusses a release layer 471 generally surrounding the protective layer and at least partially bonding thereto, which includes an acrylate with oligomers, monomers, and a reactive release substance distributed within a matrix. The reactive release layer preferably includes silicone, more particularly, the release layer may be selected from the group consisting of methyl and phenyl silicones. Moreover, the matrix can be mechanically or chemically bonded to the protective layer so that stripping the buffer layer essentially does not remove the release layer. Additionally, the release layer preferably has a secant modulus of about 20–600 MPa, an elongation to break ratio of preferably less than about 10% and/or a tensile strength of less than about 20 MPa. Of course, other suitable materials can be used as an interfacial layer for acting as a release layer such as oils or other lubricants applied to the optical waveguide or formulated into the outer coating.
Buffer layer 472 is preferably formed from a polymeric material, but other suitable materials such as elastomeric materials, or UV materials are possible. Additionally, buffer layer 472 can have a low-shrink buffer layer or manufacturing method therefor as discussed in U.S. patent application Ser. No. 10/098,971 filed on Mar. 15, 2002, the disclosure of which is incorporated herein by reference.
Assembly 470 is advantageous because it has a relatively small delta attenuation after buffering. In one experiment, a maximum delta attenuation for a population of multi-mode assemblies 470 was measured at reference wavelengths of 850 nm and 1300 nm for comparison with similar conventional tight-buffered assemblies. Specifically, the tested assemblies 470 included a 50 micron multi-mode optical fiber 12 with an interfacial layer 471 surrounded by a flame-retardant PVC buffer layer 472. Moreover, optical waveguides 12 of tested assembly 470 had coating system 14 with an inner coating B and the outer coating as specified in Table 1.
The tested conventional assemblies had a construction that was similar to assembly 470 so a valid comparison could be made. The maximum delta attenuations for the population were averaged for the respective reference wavelengths. The results are summarized in Table 8. As shown, assembly 400 has an average maximum delta attenuation that is about one-half of an average maximum delta attenuation for a conventional assembly at a reference wavelength of 1300 nm. Likewise, assembly 400 had an average maximum delta attenuation that was significantly less than the conventional assembly at a reference wavelength of 850 nm.
Additionally, the buffered optical waveguide assemblies can be used in single-waveguide cables.
Filaments 502 of cable 500 provide tensile strength along with cushioning and covering protection for assembly 470. In other words, filaments cushion the assembly from impact and cover the assembly so that the extruded jacket does not stick to the assembly 400 during manufacture. Filaments 502 preferably include aramid yarns for tensile strength; however, other suitable materials such as fiberglass can be used for providing tensile strength. In other embodiments, filaments 502 include two or more materials such as aramid and polyester. The aramid essentially provides the tensile strength, while both the aramid and polyester provide cushioning and covering protection. Additionally, filaments can include a coating for providing one or more of the following properties: anti-static, anti-abrasion, lubrication, flame-inhibitance, flame-resistance, non-wicking, smoke-inhibitance, water-blocking and/or water-swelling.
The jacket generally provides environmental protection by surrounding filaments 502 and assembly 400. Jacket 504 is preferably a polymer material and more preferably a PVC such as available under the tradename 16881 from NAP of Madison, Miss., a division of the Georgia Gulf Co. However, other polymers such as a flame-retardant polyethylene or low smoke zero halogen material can be used. The flame resistance of the cable may be specified, for example, by UL standard 1666 for riser-rated cables or by UL standard 910 for plenum-rated cables. In tested embodiments, jacket 504 had an outer diameter of about 2.9 mm; however, other sizes of diameters may be used. Other embodiments of cable 500 can use a low-shrink cable jacket and/or a manufacturing method therefor as discussed in U.S. patent application Ser. No. 10/038,073 filed on Jan. 4, 2002, the disclosure of which is incorporated herein by reference.
Single-waveguide cables (SWC) were also tested for temperature cycling performance. In this case, a special temperature cycling test was performed on a small population of 50 micron multi-mode cables 500 for comparison with a similar conventional cable at reference wavelengths of 850 and 1300 nm. The special temperature cycling test was similar for both cables and was useful for examining the delta attenuation at a 0° C. stage. The delta attenuation (dB/km) for the SWC at a second 0° C. stage are summarized in Table 9. As shown, the delta attenuation due to temperature cycling shows significantly reduced values for the present invention at the second 0° C. stage.
Additionally, temperature cycling was performed using indoor cable standard ICEA-596-2001 to test performance of SWC at −20° C. Specifically, temperature cycling for three 50 micron-multi-mode riser-rated SWCs having an OD of 2.9 mm was performed at a reference wavelength of 1300 nm. The riser-rated SWCs tested used a PVC buffer material available from AlphaGary under the tradename 2052 and a PVC jacket available from NAP under the tradename 16881. Moreover, optical waveguides 12 of tested assembly had coating system 14 with an inner coating B and the outer coating as specified in Table 1. The average maximum delta attenuation (dB/km) at −20° C. stages for the SWCs using ICEA-596-2001 are summarized in Table 10.
Additionally, buffered optical waveguide assemblies according to the present invention can be used in larger assemblies having multiple optical waveguides. For instance,
Although, cable 520 depicts six assemblies 470 stranded in one layer, other embodiments can include other numbers of assemblies in one or more layers. For example,
Cable 540 was tested measuring delta attenuation for temperature cycling and tensile performance using ICEA-596-2001, along with cable manufacturing delta attentuation. Specifically, cable 540 had nine assemblies 470 stranded about a central member 542 formed from four 2450 denier Kevlar® filaments. Buffer layer 472 of assemblies 470 was made from a PVC available from AlphaGary under the tradename 2052. The first layer of assemblies 470 was secured by a first stranded filament layer 544 formed from eight 1420 denier Kevlar® filaments. Fifteen assemblies 470 of the second layer are stranded about the first layer and secured using a second stranded filament layer 546 formed from eighteen 1420 denier Kevlar® filaments. Additionally, the cable core is surround by a jacket 548 made from a PVC available from NAP under the tradename 16881. The maximum delta attenuation (dB/km) at −20° C. stages for cable 540 at a reference wavelength of 1300 nm are summarized in Table 11.
The ICEA-596-2001 tensile test has two mutually exclusive requirements for qualifying a cable, namely, a tensile loading requirement and an optical fiber strain requirement. The tensile loading requirement applies a rated installation load for thirty minutes and measures the fiber strain at the end of thirty minutes with the load applied. Thereafter, the load is reduced to 30% of the rated installation loading, called the residual load, and held for ten minutes at which time the delta attenuation and fiber strain is measured with the load applied. The fiber strain requirement states that the axial fiber strain must be less than, or equal, to 20% of the fiber proof at the rated installation load and less than, or equal, to 20% of the fiber proof level at the residual load. The attenuation requirement states that the delta attenuation at residual load must be less than or equal to 0.60 dB/km. Table 12 summarizes the average delta attenuation (dB/km) at a reference wavelength of 1300 nm for both the rated installation load and the residual load along with the optical fiber strain at both loads. As shown, tested cable 540 passed the ICEA-596-2001 tensile test for both the tensile loading requirement and the optical fiber strain requirement. The delta attenuation value at the rated installation load are given for reference.
Furthermore, the average and maximum cabling attenuations associated with manufacturing tested cable 540 according to the present invention were examined at a reference wavelength of 1300 nm. Respectively, the average and maximum cabling attenuations for manufacturing were 0.494 dB/km and 0.549 dB/km. An average cabling attenuation associated with manufacturing similar conventional cables was taken from production data for comparison purposes. The average delta attenuation for the conventional 24 position cable is 0.57 dB/km.
Additionally, 24 position cables 540 were subjected to GR-409 mechanical testing for determining delta attenuation on multi-mode designs. Specifically, tensile testing according to GR-409 was performed on cable 540. The GR-409 specification requires that all of the optical waveguides of the cable have a maximum delta attenuation that is less than 0.4 dB/km. In total ten cables were tested, five were conventional cables and five were according to the present invention. The delta attenuation (dB/km) data for the GR-409 tensile test at 1300 nm is summarized in Table 13.
As shown, the average maximum delta attenuation for cables 540 is about one-third of the maximum value for the conventional cables tested. More importantly, conventional cables 1, 4, and 5 failed the GR-409 requirement for maximum attenuation. On the other hand, all of tested cables 540 passed this GR-409 requirement. Thus, cable 540 has superior performance over the conventional cable with the multi-mode assemblies.
Stranded cables using assemblies such as 470 can have other configurations that are suitable for both indoor and outdoor applications.
Of course, dual-layer configurations are possible and generally speaking are more difficult to qualify in performance tests.
Cables 550 and 560 in 50 micron multi-mode configurations were tested according to a modified ICEA-696-2001 temperature cycling test and compared with similar conventional cables. The standard ICEA-696-2001 temperature cycling test requires two −40° C. to 70° C. cycles. In order to pass the ICEA-596-2001 temperature cycling test, the cable must have a maximum delta attenuation of 0.600 dB/km or less. In the past, qualifying conventional cables with this specification was difficult. Moreover, the specification was extremely difficult, if not impossible, with 50 micron multi-mode dual-layer cable configurations.
The modified ICEA-696 temperature test included two −20° C. cycles at the beginning of the test for determining performance at −20° C., which were followed by standard ICEA-596 temperature cycling test. The modified ICEA-696 temperature test is considered a more severe temperature cycling test since the additional −20° C. temperature cycles subject the cable to additional stress levels. A single layer 12-position cable was tested in both plenum and riser configurations and the dual-layer cable was tested in a plenum configuration. Tables 14 and 15 respectively summarize the maximum and average delta attenuation (dB/km) results for the modified ICEA-696 test at a reference wavelength of 1300 nm for a plenum and riser-rated cables along with corresponding conventional cables. The plenum-rated cables tested are denoted with a P, and used a PVDF material for the jacket available from Dyneon under the tradename 31008-003. The riser-rated cables are denoted with a R and used a PVC material available from AlphaGary under the tradename GW 2371.
As shown in Tables 13 and 14, the conventional 24-fiber dual-layer plenum configuration had elevated levels of attenuation for the modified ICEA-696 temperature test. On the other hand, the tested cable 560 P met the requirements of the ICEA-696-2001 temperature test since the maximum delta attenuation was less than 0.60 dB/km.
Cables 550 and 560 in 50 micron multi-mode configurations were also tested according to the respective ICEA-696-2001 tensile tests and compared with similar conventional cables. The ICEA-696-2001 tensile test requires applying a rated installation load and measuring the delta attenuation and fiber strain. The rated installation load is held for one hour and then the fiber strain is measured with the load applied. In this case, the delta attenuation was also measured at the rated installation load to gauge the difference in optical performance between the cables at equivalent strain values. Thereafter, the load is reduced to 30% of the rated installation loading, called the residual load, and held for ten minutes at which time the delta attenuation and fiber strain is measured with the load applied. Finally, the load is removed and the cable is allowed to relax for five minutes before taking the final delta attenuation measurement. In order to pass the ICEA-696-2001 tensile test, the multi-mode cable must have a maximum delta attenuation of 0.60 dB/km or less at residual load and after removal of the load. Like the temperature cycling test, a single layer 12-position cable was tested in both plenum and riser configurations and the dual-layer cable was tested in a plenum configuration for this tensile test. Table 16 summarizes the maximum delta attenuation (dB/km) results for the ICEA-696 tensile test at a reference wavelength of 1300 nm for a plenum and riser-rated cables along with corresponding conventional cables. Like before, the plenum and riser configurations are respectively noted by P and R in the Tables.
As shown in Table 16, the conventional cables had elevated levels of delta attenuation at the 1-hour hold at the rated installation load. On the other hand, the tested cables according to the present invention met the requirements of the ICEA-696-2001 tensile test since the maximum delta attenuation was less than 0.60 dB/km. Moreover, the cables according to the present invention had significant reduction of delta attenuation compared with the conventional cables at the 1-hour hold measurement.
Additionally, the concepts of the present invention may be used in other stranded cable configurations.
Other embodiments of the present invention can package optical waveguide 12 in other ways. For instance,
Assemblies like assembly 580 may be used as stranded subunits in larger assemblies. For instance,
Other assemblies of the present invention were also tested to determine, the delta attenuation due to manufacturing. For instance,
Additionally, the zipcords were temperature cycled using standard ICEA-596-2001 to test performance of the zipcord at −20° C. Specifically, temperature cycling zipcords was performed at a reference wavelength of 1300 nm. The maximum delta attenuation (dB/km) at −20° C. stages for the zipcords tested using ICEA-596-2001 are summarized in Table 18.
Zipcords according to the present invention can also include embodiments having features as disclosed in U.S. patent application Ser. No. 10/209,485 filed on Jul. 31, 2002, the disclosure of which is incorporated herein by reference. For instance, optical waveguides 12 may have a bandwidth capacity ratio between the first and second optical waveguides of about 2:1 or greater. Additionally, the appropriate leg of the zipcord can have a marking indicia 609 for marking the leg with the high capacity optical waveguide 12.
The concepts of the present invention can also be practiced with other suitable assemblies having both one or more electrical components and at least one optical waveguides 12. By way of example,
Still other exemplary embodiments according to the present invention are possible. For instance, cable assemblies according to the present invention can also be configured as drop/access cables.
In one embodiment, strength member 624, or other drop cable strength members, are a solid metallic material such as steel having a relatively low bend energy and good memory shape so that it can be bent into a relatively tight radius so that it may function as a tie down. Thus, the strength member is suitable, if necessary, for; self-attaching to studs, hooks, or the like without the added expense and labor of clamps and/or other hardware, yet it is still suitable for such hardware. The strength member may also be annealed to relieve work hardening. In another embodiment, the strength member has a carbon content between about 0.30 percent to about 0.75 percent. A coating may also be applied to the strength member. For instance, suitable coatings include zinc-based or polymer coatings for environmental/corrosion protection, a copper coating for conductivity; however, other suitable coating(s) may be useful.
The concepts of the present invention can also be practiced with high-data rate communication systems. For instance, the chromatic dispersion characteristics of the optical waveguides can be controlled in dispersion managed cable system (DMCS) so that the positive and negative chromatic dispersion in the system at least partially offset each other. One way to manage dispersion is by controlling a helix value of a cable as discussed in U.S. patent application Ser. No. 10/035,769 filed on Dec. 26, 2001, the disclosure of which is incorporated herein by reference. Moreover, dispersion managed cable systems can employ cables having controlled helix-plus-EFL (excess fiber length) values as discussed in U.S. patent application Ser. No. 10/107,424, the disclosure of which is incorporated herein by reference.
Furthermore, dispersion managed cable systems can be optically connected optical waveguides 12 that have a mode field differential, i.e., a D+ optical waveguide and a D− optical waveguide, using a bridge fiber within a cable as discussed in U.S. patent application Ser. No. 09/908,183 filed on Jul. 18, 2001, the disclosure of which is incorporated herein by reference. Optical waveguides for dispersion managed cable systems may be allocated according to U.S. patent application Ser. No. 10/328,507 filed on Dec. 24, 2002, the disclosure of which is incorporated herein by reference. The dispersion managed cable systems can also have marking indicia on the buffer tubes or cable jacket so that the craftsman can identify specific optical waveguides. The buffer tubes or cable marking indicia is preferably according to U.S. patent application Ser. No. 09/902,239 filed on Jul. 10, 2001, the disclosure of which is incorporated herein by reference.
Many modifications and other embodiments of the present invention will become apparent to a skilled artisan. For instance, articles, assemblies, and/or cables can include suitable configurations having other components such as strength members, ripcords, water-swellable materials, armor, electrical components, or other cable components. Additionally, the concepts of the present invention are useful with other fiber optic assemblies or cables such as optical backplanes. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed herein and that modifications and other embodiments may be made within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. The invention has been described with reference to silica-based optical fibers, but the inventive concepts of the present invention are applicable to other suitable optical waveguides, fiber optic articles, assemblies, and/or cable configurations as well.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4474830 | Taylor | Oct 1984 | A |
| 4514037 | Bishop et al. | Apr 1985 | A |
| 4552433 | Titchmarsh et al. | Nov 1985 | A |
| 4581165 | Frank et al. | Apr 1986 | A |
| 4609718 | Bishop et al. | Sep 1986 | A |
| 4629287 | Bishop | Dec 1986 | A |
| 4682850 | White et al. | Jul 1987 | A |
| 4682851 | Ansel | Jul 1987 | A |
| 4798852 | Zimmerman et al. | Jan 1989 | A |
| 4900126 | Jackson et al. | Feb 1990 | A |
| 4962992 | Chapin et al. | Oct 1990 | A |
| 5062685 | Cain et al. | Nov 1991 | A |
| 5093386 | Bishop et al. | Mar 1992 | A |
| 5104433 | Chapin et al. | Apr 1992 | A |
| 5388175 | Clarke | Feb 1995 | A |
| 5408564 | Mills | Apr 1995 | A |
| 5416880 | Edwards et al. | May 1995 | A |
| 5420955 | Cooke et al. | May 1995 | A |
| 5442722 | DeCarlo | Aug 1995 | A |
| 5527835 | Shustack | Jun 1996 | A |
| 5561730 | Lochkovic et al. | Oct 1996 | A |
| 5561731 | Cooke et al. | Oct 1996 | A |
| 5566266 | Nave et al. | Oct 1996 | A |
| 5639846 | Shustack | Jun 1997 | A |
| 5744514 | Shustack | Apr 1998 | A |
| 5768460 | Levi et al. | Jun 1998 | A |
| 5837750 | Szum et al. | Nov 1998 | A |
| 5852698 | Bringuier | Dec 1998 | A |
| 5857051 | Travieso et al. | Jan 1999 | A |
| 5908484 | Decker et al. | Jun 1999 | A |
| 5917978 | Rutterman | Jun 1999 | A |
| 5970196 | Greveling et al. | Oct 1999 | A |
| 6014487 | Field et al. | Jan 2000 | A |
| 6014488 | Shustack | Jan 2000 | A |
| 6023547 | Tortorello | Feb 2000 | A |
| 6025422 | Hall | Feb 2000 | A |
| 6035087 | Bonicel et al. | Mar 2000 | A |
| 6049647 | Register et al. | Apr 2000 | A |
| 6057018 | Schmidt | May 2000 | A |
| 6057034 | Yamazaki et al. | May 2000 | A |
| 6064789 | Mills | May 2000 | A |
| 6075065 | Yamazaki et al. | Jun 2000 | A |
| 6097866 | Yang et al. | Aug 2000 | A |
| 6101305 | Wagman et al. | Aug 2000 | A |
| 6110593 | Szum et al. | Aug 2000 | A |
| 6122424 | Bringuier | Sep 2000 | A |
| 6136880 | Snowwhite et al. | Oct 2000 | A |
| 6192178 | Logan et al. | Feb 2001 | B1 |
| 6195486 | Field et al. | Feb 2001 | B1 |
| 6215934 | Aloisio, Jr. et al. | Apr 2001 | B1 |
| 6243523 | Aloisio et al. | Jun 2001 | B1 |
| 6249629 | Bringuier | Jun 2001 | B1 |
| 6253013 | Lochkovic et al. | Jun 2001 | B1 |
| 6289158 | Blyler et al. | Sep 2001 | B1 |
| 6298189 | Szum et al. | Oct 2001 | B1 |
| 6304701 | Bringuier et al. | Oct 2001 | B1 |
| 6316516 | Chien et al. | Nov 2001 | B1 |
| 6326416 | Chien et al. | Dec 2001 | B1 |
| 6356690 | McAlpine et al. | Mar 2002 | B1 |
| 6360044 | Mills et al. | Mar 2002 | B1 |
| 6363192 | Spooner | Mar 2002 | B1 |
| 6370303 | Fitz et al. | Apr 2002 | B1 |
| 6370304 | Mills et al. | Apr 2002 | B1 |
| 6374023 | Parris | Apr 2002 | B1 |
| 6389204 | Hurley | May 2002 | B1 |
| 6449412 | Rutterman et al. | Sep 2002 | B1 |
| 6463199 | Quinn et al. | Oct 2002 | B1 |
| 6472450 | Szum et al. | Oct 2002 | B1 |
| 6487347 | Bringuier | Nov 2002 | B1 |
| 6496628 | Opel et al. | Dec 2002 | B1 |
| 6501887 | Bringuier et al. | Dec 2002 | B1 |
| 6501888 | Gimblet et al. | Dec 2002 | B1 |
| 6519399 | Strong et al. | Feb 2003 | B1 |
| 6528553 | Komiya et al. | Mar 2003 | B1 |
| 6531522 | Winningham | Mar 2003 | B1 |
| 6534557 | Szum et al. | Mar 2003 | B1 |
| 6535673 | Lochkovic | Mar 2003 | B1 |
| 6539152 | Fewkes et al. | Mar 2003 | B1 |
| 6542674 | Gimblet | Apr 2003 | B1 |
| 6546175 | Wagman et al. | Apr 2003 | B1 |
| 6553167 | Hurley et al. | Apr 2003 | B1 |
| 6553169 | Fabian | Apr 2003 | B1 |
| 6559197 | Fewkes et al. | May 2003 | B1 |
| 6563996 | Winningham | May 2003 | B1 |
| 6579618 | Ishikawa et al. | Jun 2003 | B1 |
| 6584263 | Fewkes et al. | Jun 2003 | B1 |
| 6602601 | Fewkes et al. | Aug 2003 | B1 |
| 6621966 | Lail | Sep 2003 | B1 |
| 6633709 | VanVickle et al. | Oct 2003 | B1 |
| 6636673 | Register, III et al. | Oct 2003 | B1 |
| 6671441 | Bocanegra et al. | Dec 2003 | B1 |
| 6775451 | Botelho et al. | Aug 2004 | B1 |
| 20020009272 | Parris | Jan 2002 | A1 |
| 20020102078 | Bringuier et al. | Aug 2002 | A1 |
| 20020102079 | Lail et al. | Aug 2002 | A1 |
| 20020102086 | Fewkes et al. | Aug 2002 | A1 |
| 20020146225 | Bulters et al. | Oct 2002 | A1 |
| 20020197030 | McAlpine et al. | Dec 2002 | A1 |
| 20020197040 | Takahashi et al. | Dec 2002 | A1 |
| 20030012530 | Yamasaki et al. | Jan 2003 | A1 |
| 20030016923 | Summers et al. | Jan 2003 | A1 |
| 20030018122 | Bishop et al. | Jan 2003 | A1 |
| 20030044140 | Fewkes et al. | Mar 2003 | A1 |
| 20030044141 | Melton et al. | Mar 2003 | A1 |
| 20030049446 | Schissel et al. | Mar 2003 | A1 |
| 20030059188 | Baker et al. | Mar 2003 | A1 |
| 20030077059 | Chien et al. | Apr 2003 | A1 |
| 20030091307 | Hurley et al. | May 2003 | A1 |
| 20030095770 | Fewkes et al. | May 2003 | A1 |
| 20030100627 | Bishop et al. | May 2003 | A1 |
| 20030118295 | Lail et al. | Jun 2003 | A1 |
| 20030118299 | Seddon et al. | Jun 2003 | A1 |
| 20030118300 | Seddon et al. | Jun 2003 | A1 |
| 20030118301 | Hurley et al. | Jun 2003 | A1 |
| 20030123839 | Chou et al. | Jul 2003 | A1 |
| 20030128941 | Lanier et al. | Jul 2003 | A1 |
| 20030174989 | Lanier et al. | Sep 2003 | A1 |
| 20030185529 | Register et al. | Oct 2003 | A1 |
| 20030197032 | Petit | Oct 2003 | A1 |
| 20030223713 | Chiasson et al. | Dec 2003 | A1 |
| 20030223714 | Conrad et al. | Dec 2003 | A1 |
| 20040022504 | Hurley et al. | Feb 2004 | A1 |
| 20040022510 | Suzuki et al. | Feb 2004 | A1 |
| 20040052483 | Chandraiah et al. | Mar 2004 | A1 |
| Number | Date | Country |
|---|---|---|
| WO 9917144 | Apr 1999 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20050013573 A1 | Jan 2005 | US |
