Patent Grant
9989699
The present invention relates to optical fibers having low bend losses and suitable for use with silicon photonic devices.
The need for greater bandwidth and higher data transmission rates has motivated efforts to develop next-generation platforms for information storage and delivery. It is widely believed that optical information systems will provide superior performance to today's microelectronics-based systems. Integrated optical systems based on silicon photonics are a leading replacement technology for microelectronic systems. Silicon photonics interfaces with standard CMOS technologies and WDM (wavelength division multiplexing) to convert electrical signals to optical signals, to transmit optical signals, and to reconvert optical signals to electrical signals. In disaggregated systems, transfer of signals between units occurs through optical links that provide high bandwidth and high data transfer rates.
Data centers with disaggregated architecture are being proposed for future data centers, involving use of silicon photonics and WDM technology. While a number of these systems have focused on using multimode optical fibers, system architectures using single-mode fibers are also contemplated.
Consequently, there is a need for suitable optical fibers for such data center applications and like applications
Disclosed herein are optical waveguide fibers comprising:
a depressed index cladding region surrounding the core region, the depressed index cladding region comprising an outer radius r3 and a relative refractive index Δ3 less than −0.2%, and an absolute volute of trench volume V3 such 45% Δ-micron2≤|V3|≤200% Δ-micron2;
a first outer cladding region surrounding the depressed index cladding region, the outer cladding region comprising a relative refractive index Δ4 and an outer radius r4; and
a second outer cladding layer a relative refractive index Δ5, said second outer cladding region comprising silica based glass doped with 5 to 20 wt % titania and having a thickness TM, such that 2 micron≤TM≤30 microns, the second outer layer having an outer radius r5 of not greater than 65 microns;
wherein the optical fiber has a mode field diameter at 1550 nm (MFD1550) and 8.3 microns≤MFD1550≤10.5 microns, a single mode cutoff wavelength <1550 nm when bent 1 turn around a 2.5 mm radius mandrel, an effective area at 1550 nm of at least 65 micron2 and less than 85 micron2, and a bending loss at 1550 nm as determined by the mandrel wrap test using a mandrel comprising a radius of 2.5 mm-of ≤1.0 dB/turn.
According to at least some exemplary embodiments of the optical fiber disclosed herein, the single mode cutoff wavelength is between 1100 nm and 1450 mm when the fiber bent 1 turn around a 2.5 mm radius mandrel. According to at least some exemplary embodiments disclosed herein 60% Δ-micron2≤|V3|≤200% Δ-micron2.
According to at least some exemplary embodiments disclosed herein the fiber exhibits bending loss at 1550 mm as determined by the mandrel wrap test using a mandrel comprising a radius of 2.5 mm-of ≤0.55 dB/turn, and in some embodiments ≤0.4 dB/turn, in some embodiments ≤0.2 dB/turn, for example ≤0.1 dB/turn, or even ≤0.01 dB/turn.
According to at least some exemplary embodiments disclosed herein the fiber the outer radius r1 of the core region is 3.0≤r1≤6, and the trench volume V3 is such that 70% Δ-micron2≤|V3|≤150% Δ-micron2.
According to at least some exemplary embodiments 80% Δ-micron2≤|V3|≤200% Δ-micron2, and in some embodiments 100% Δ-micron2≤|V3|≤150% Δ-micron2. According to at least some exemplary embodiments 60% Δ-micron2≤|V3|≤140% Δ-micron2, and in some embodiments 70% Δ-micron2≤|V3|≤140% Δ-micron2. In some embodiments 80% Δ-micron2≤|V3|≤140% Δ-micron2.
According to at least some exemplary embodiments 30 microns≤r5≤63 microns, and in some embodiments 30 microns≤r5≤50 microns. According to at least some exemplary embodiments 40 microns≤r5≤62.5 microns. For example, in some exemplary embodiments, the outer radius r5 of the second outer cladding is 62.5, 60, 55, 50, 42, 41.7, 35, 31.25, or 30 microns.
According to at least some exemplary embodiments the optical fiber has a fiber cutoff wavelength <1550 nm when bent 1 turn around a 2.5 mm radius mandrel, an effective area at 1550 nm of at least 65 micron2 and less than 85 micron2, and a bending loss at 1550 nm as determined by the mandrel wrap test using a mandrel comprising a radius of 2.5 mm-of ≤1.0 dB/turn.
According to at least some exemplary embodiments the optical fiber has a 22 m cable cutoff wavelength less than 1550 nm. According to at least some exemplary embodiments the optical fiber has a 22 m cable cutoff wavelength less than 1300 nm, for example between 1000 nm and 1350 nm, for example between 1000 nm and 1300 nm. According to at least some exemplary embodiments the optical fiber has a 22 m cable cutoff wavelength between 1200 nm and 1550 nm, for example between 1200 nm and 1350 nm.
According to at least some exemplary embodiments the optical fiber the second outer cladding layer comprises 5 to 15 wt % titania, and 3 micron≤TM≤15 microns.
In some exemplary embodiments 2 micron≤TM≤20 microns. In some exemplary embodiments 2 micron≤TM≤15 microns. In some exemplary embodiments 3 micron≤TM≤15 microns. In some exemplary embodiments 2 micron≤TM≤10 microns. In some embodiments 2 micron≤TM≤5 microns.
In some embodiments the mode field diameter at 1550 nm (MFD1550) is 9 microns≤MFD1550≤10 microns. In some embodiments the mode field diameter at 1550 nm (MFD1550) 9.5 microns≤MFD1550≤10.3 microns.
In some embodiments the relative refractive index of the depressed index cladding region, Δ3, is −0.2%≤Δ3≤−0.7%, and in some embodiments −0.3%≤Δ3≤−0.5%.
According to the exemplary described herein the core region comprises α, and 10≤α≤100. However, in some exemplary embodiments 1≤α≤10.
According to at least some exemplary embodiments disclosed herein the fiber includes a coating surrounding the second outer cladding layer, the coating comprises: a primary coating P having a Young's modulus 0.1 to 1 MPa; and a secondary coating S having a Young's modulus of 1100 MPa to 2500 MPa, wherein the secondary coating has an outer coating diameter of not greater than 260 microns, in some embodiments not greater than 250 nm, and in some embodiments not greater than 242 microns, for example less than 210 microns
According to at least some exemplary embodiments a micro-optic device comprises:
a core region comprising an outer radius r1 in the range from 3.0 to 7.0 microns and a relative refractive index Δ1max in the range from 0.32% to 0.5%;
a depressed index cladding region surrounding the core region, the depressed index cladding region comprising an outer radius r3 and a relative refractive index Δ3 less than −0.2%, and a trench volume V3 such that of 45% Δ-micron2≤|V3|≤200% Δ-micron2;
a first outer cladding region surrounding the depressed index cladding region, the outer cladding region comprising a relative refractive index Δ4 and an outer radius r4; and
a second outer cladding layer a relative refractive index Δ5 the second outer cladding region comprising silica based glass doped with 5 to 20 wt % titania and having a thickness TM, such that 3 micron≤TM≤30 microns, the second outer layer having an outer radius r5 of not greater than 65 microns;
wherein the optical fiber has a mode field diameter at 1550 nm (MFD1550) is 8.3 microns≤MFD1550≤10.5 microns, a single mode cutoff wavelength <1550 nm when bent 1 turn around a 2.5 mm radius mandrel, an effective area at 1550 nm of at least 65 micron2 and less than 85 micron2, and a bending loss at 1550 nm as determined by the mandrel wrap test using a mandrel comprising a radius of 2.5 mm-of ≤1.0 dB/turn.
In some embodiments the optical fiber has a section that is bent to a bend radius rb of not greater than 3 mm, for example 0.5 mm to 2.5 mm. In some embodiments the bend radius rb is 2.5 mm≥rb≥1 mm, and in some embodiments 2.5 mm≥rb≥1.5 mm.
In some embodiments the optical fiber has a section that is bent to a bend radius of ≤2.5 mm, and the fiber exhibits bending loss at 1550 nm as determined by the mandrel wrap test using a mandrel comprising a radius of 2.5 mm-of ≤0.55 dB/turn, and in some embodiments ≤0.1 dB/turn, or even of ≤0.01 dB/turn. In some embodiments the optical fiber has a section that is bent to a bend radius of ≤2 mm, and the fiber exhibits bending loss at 1550 nm as determined by the mandrel wrap test using a mandrel comprising a radius of 2 mm-of ≤1 dB/turn, for example ≤0.55 dB/turn, and in some embodiments ≤0.1 dB/turn, or even ≤0.01 dB/turn.
Reference will now be made in detail to the present preferred embodiments, examples of which are illustrated in the accompanying drawings.
Additional features and advantages will be set forth in the detailed description which follows and will be apparent to those skilled in the art from the description or recognized by practicing as described in the following description together with the claims and appended drawings.
The “refractive index profile” is the relationship between refractive index or relative refractive index and the radial position within the waveguide fiber. The radius for each segment of the refractive index profile is given by the abbreviations r1, r2, r3, r4, etc. and lower and upper case are used interchangeably herein (e.g., r1 is equivalent to R1).
The term “relative refractive index percent” (also referred to herein as “relative refractive index”, and “refractive index delta”) is defined as Δ %=100× (ni2−nc2)/2ni2, and as used herein, unless stated otherwise, nc is the average refractive index of the first outer cladding region 40 (which in some embodiments is undoped silica). As used herein, the relative refractive index is represented by Δ and its values are given in units of “%”, unless otherwise specified. The terms: delta, Δ, Δ %, % Δ, delta %, % delta and percent delta may be used interchangeability herein. That is, as used herein, relative refractive index percent (or relative refractive index, or refractive index delta) of a given fiber region is measured relative to undoped silica. In cases where the refractive index of a region is less than the average refractive index of undoped silica, the relative index percent is negative and may be referred to as having a depressed region or depressed index. In cases where the refractive index of a region is greater than the average refractive index of undoped silica, the relative index percent is positive. An “updopant” is herein considered to be a dopant which has a propensity to raise the refractive index relative to pure undoped SiO2. A “downdopant” is herein considered to be a dopant which has a propensity to lower the refractive index relative to pure undoped SiO2. Examples of updopants include GeO2 (germania), Al2O3, P2O5, TiO2, Cl, Br. Examples of down dopants include fluorine and boron.
“Chromatic dispersion”, herein referred to as “dispersion” unless otherwise noted, of a waveguide fiber is the sum of the material dispersion, the waveguide dispersion, and the inter-modal dispersion. In the case of single mode waveguide fibers the inter-modal dispersion is zero. Zero dispersion wavelength is a wavelength at which the dispersion has a value of zero. Dispersion slope is the rate of change of dispersion with respect to wavelength.
“Effective area” is defined as:
Aeff=2π(∫f2rdr)2/(∫f4rdr),
where the integration limits are 0 to ∞, and f is the transverse component of the electric field associated with light propagated in the waveguide. The effective area Aeff depends on the wavelength of the optical signal and is reported herein for wavelengths of 850 nm, 980 nm, 1060 nm and 1550 nm. As used herein, unless otherwise noted, “effective area” or “Aeff” refers to optical effective area at a wavelength of 1550 nm.
The term “alpha parameter” or “α-parameter” or “alpha value” or just “α” refers to a parameter used to define a relative refractive index profile of the core, expressed in terms of Δ(r) which is in units of “%”, where r is radius, which follows the equation,
Δ(r)=Δ(ro)(1−[|r−ro|/(r1−ro)]α),
where ro is the point at which Δ(r) is maximum (also referred herein as Δ1max), r1 is the point at which Δ(r) % is zero, and r is in the range ri≤r≤rf, where Δ is defined above, ri is the initial point of the α-profile, rf is the final point of the α-profile, and α is an exponent which is a real number. In some embodiments of the optical fiber described herein (for example in fibers that do not have a centerline dip in the fiber core) Δ(r0)=Δ(ri). In some embodiments r1≡rf.
The terms “trench” and “depressed index cladding region” are used interchangeably herein and refer to a cladding region that has a minimum relative refractive index that is lower than that of the adjacent regions that are in contact therewith. The trench volume V3 is defined herein as
V3=2∫Δ3-2(r)rdr
The mode field diameter (MFD) is measured using the Peterman II method wherein, 2w=MFD, and w2=(2∫f2 r dr/∫[df/dr]2 r dr), the integral limits being 0 to ∞, and MFD1550 is mode field diameter at 1550 nm wavelength.
The bend resistance of a waveguide fiber can be gauged by induced attenuation under prescribed test conditions, for example by deploying or wrapping the fiber around a mandrel of a prescribed diameter, e.g., by wrapping 1 turn around a either a 6 mm, 10 mm, or 20 mm or similar diameter mandrel (e.g. “1×10 mm diameter macrobend loss” or the “1×20 mm diameter macrobend loss”) and measuring the increase in attenuation per turn.
Fiber cutoff (also referred to herein as fiber cutoff wavelength) is measured by the standard 2 m fiber cutoff test, FOTP-80 (EIA-TIA-455-80), to yield the “fiber cutoff wavelength”, also known as the “2 m fiber cutoff” or “measured cutoff”. The FOTP-80 standard test is performed to either strip out the higher order modes using a controlled amount of bending, or to normalize the spectral response of the fiber to that of a multimode fiber.
By fiber cutoff wavelength when bent 1 turn around a 2.5 mm radius mandrel we mean the fiber cutoff wavelength as measured by the standard 2 m fiber cutoff test, FOTP-80 (EIA-TIA-455-80) deployed with an additional single bend around a 2.5 mm radius mandrel situated within 20 cm distance from the end of the fiber where the light is launched. Similarly, by fiber cutoff wavelength when bent 1 turn around a 2 mm radius mandrel we mean the fiber cutoff wavelength as measured by the standard 2 m fiber cutoff test, FOTP-80 (EIA-TIA-455-80) deployed with an additional single bend around a 2 mm radius mandrel situated within 20 cm distance from the end of the fiber where the light is launched.
By cabled cutoff wavelength, or “cabled cutoff” as used herein, we mean the single mode cutoff as measured by the 22 m cabled cutoff test described in the EIA-445 Fiber Optic Test Procedures, which are part of the EIA-TIA Fiber Optics Standards, that is, the Electronics Industry Alliance-Telecommunications Industry Association Fiber Optics Standards.
By cable cut off with a 2.5 mm radius bend, we mean the single mode cutoff as measured by the 22 m cabled cutoff test described in the EIA-445 Fiber Optic Test Procedures measured with an additional single bend around a 2.5 mm radius mandrel. Similarly, by cable cut off with a 2 mm radius bend, we mean the single mode cutoff as measured by the 22 m cabled cutoff test described in the EIA-445 Fiber Optic Test Procedures measured with an additional single bend around a 2 mm radius mandrel.
Unless otherwise noted herein, optical properties (such as dispersion, dispersion slope, etc.) are reported for the LP01 mode.
One challenging problem is to couple light from a silicon photonic device to a single mode fiber with low cost. An attractive approach is to use a grating to couple the light out of the surface of a silicon (Si) waveguide to an optical fiber as shown in
Optical fibers 100 disclosed herein are capable of exhibiting an effective area Aeff at 1550 nm which is greater than about 55 microns2, preferably between 60 and 85 microns2. In some preferred embodiments, the effective area at 1550 nm is between about 75 and 82 micron2.
A coating 70 surrounds the cladding layer 60. The coating 70 extends to an outer diameter r6.
As stated above, optical fibers 100 are capable of providing low bend loss at tight radii of curvature and high resistance to surface damage for bent fiber connector applications, for example when used with a ferrule connector 5 coupling it to a silicon photonics chip 7, as shown in
According to at least some of the embodiments of the optical fiber 100 disclosed herein, the bending loss at 1550 nm around a mandrel with a bend radius rb of 2.5 mm is ≤0.8 dB/turn, in some embodiments ≤0.5 dB/turn, in some embodiments ≤0.4 dB/turn, in some embodiments ≤0.2 dB/turn, in some embodiments ≤0.1 dB/turn, in some embodiments ≤0.05 dB/turn, and in some embodiments ≤0.01 dB/turn. Also, according to at least some the embodiments of the optical fiber 100 disclosed herein, the bending loss at 1550 nm with a bend radius rb of 2 mm is ≤1 dB/turn, in some embodiments ≤0.5 dB/turn, and in some embodiments ≤0.4 dB/turn. Also, according to at least some the embodiments of the optical fiber 100 disclosed herein the bending loss at 1550 nm with a bend radius rb of 2 mm is ≤0.2 dB/turn, in some embodiments ≤0.1 dB/turn, and in some embodiments ≤0.05 dB/turn. Also, according to at least some the embodiments of the optical fiber 100 disclosed herein the bending loss at 1550 nm with a bend radius rb of 2 mm is ≤0.02 dB/turn, and in some embodiments ≤0.01 dB/turn. Also, according to at least some the embodiments of the optical fiber 100 disclosed herein, the bending loss at 1550 nm with a bend radius rb of 1.5 mm is ≤1 dB/turn, in some embodiments ≤0.5 dB/turn, and in some embodiments ≤0.4 dB/turn, and in some embodiments ≤0.2 dB/turn. Also, according to at least some the embodiments of the optical fiber 100 disclosed herein, the bending loss at 1550 nm with a bend radius rb of 1 mm is ≤1 dB/turn, in some embodiments ≤075 dB/turn, in some embodiments ≤0.5 dB/turn, and in some embodiments ≤0.4 dB/turn, and in some embodiments ≤0.2 dB/turn.
The outer most cladding layer 60 (also referred to herein as layer ML, or the second outer cladding layer) comprises TiO2 (titania) and protects the outer glass surface of the first outer cladding 40 also referred to herein as the (first outer cladding region 40) from damage during handling and also during stripping of the coating 70, as well as improves fiber's mechanical reliability, especially in the presence of abrasions to the glass surfaces as can happen during assembly of miniature glass components.
In the profile of
It should be noted that the inner cladding region 20 is optional and may be eliminated as noted hereinabove. When inner cladding region 20 is missing, depressed index region 30 is directly adjacent core region 10. The relative ordering of relative refractive indices Δ1, Δ3, and Δ4 satisfy the conditions Δ1>Δ4>Δ3.
In the embodiments disclosed herein the relative ordering of relative refractive indices Δ1, Δ2, Δ3, and Δ4 satisfy the conditions Δ1>Δ4>Δ3 and Δ1>Δ2>Δ3. The values of Δ2 and Δ4 may be equal or either may be greater than the other, but both Δ2 and Δ4 are between Δ1 and Δ3.
According to the embodiments of the optical fiber 100 described herein, the maximum relative refractive index Δ1 of the core region 10 (relative to Δ4 of the the outer cladding region 40) is between 0.3% to 0.6%, more preferably between 0.32% to 0.5%. According to some embodiments the core region 10 has radius r1 is between 3 to 6 μm, more preferably between 4 μm and 5 μm. The core region 10 can have a step index profile with α>10, or alternatively can exhibit a graded index profile with α≤10, for example α≤5 (e.g., 1≤α≤10, or 1≤α≤5). The relative refractive index Δ2 of the inner cladding region 20 (relative to Δ4 of the the outer cladding region 40) is between −0.05 to 0.05%. The inner cladding region 20 can be pure silica glass, or silica glass doped with an up-dopant such as Cl, or GeO2. The minimum relative refractive index Δ3 of the trench region 30 (relative to Δ4 of the the outer cladding region 40) is between −0.2 to −0.7%, and in some embodiments between −0.3 to −0.5%. In the exemplary embodiments the trench region 30 is silica based glass doped with boron or fluorine. The width w of the trench region 30 (w=r3−r2) is between 3 to 20 microns, in some embodiments between 4 and 15 microns. The outer cladding region 40 can be pure silica glass, or silica glass doped with an up-dopant such as Cl, or GeO2. The cladding layer 60 (also referred to herein as “outer most cladding layer”, the second outer cladding layer, or a “mechanical reliability layer”) comprises 5 to 20 wt. % TiO2, and in some embodiments, between 5-15 wt. % TiO2. The outer most cladding layer 60 has a radial thickness TM between 3 to 30 microns, and in some embodiments, between 5 to 15 microns. The outer most cladding layer 60 improves mechanical stability/reliability of the fiber 100. In at least some embodiments Δ5>Δ1.
The outer cladding region 40 of the fiber 100, surrounds the lower index trench region 30. In the exemplary embodiments described herein the outer cladding starts at a radius r3 has an outer radius r4. The outer cladding region 40 of the fiber 100 comprises relative refractive index Δ4 which is higher than the relative refractive index Δ3 of trench region 30 thereby forming a region which is “updoped” with respect to trench region 30. The trench region 30 is preferably downdoped relative to pure silica, for example with fluorine or boron. Note, however that the outer cladding region 40 may be either pure silica, or may be updoped relative to pure silica.
The absolute value |V3| of the volume V3 of the trench region 30 may be greater than 45% Δmicron2, and in some embodiments may be greater than 50% Δmicron2. The absolute value for the volume V3 of the trench region 30 is in some embodiments is at least 60% Δmicron2, and in some embodiments is at least 80% Δmicron2. In some embodiments, the absolute value for the volume V3 of the first cladding region (2) is less than 200% Δmicron2, in some embodiments less than 150% Δmicron2, and in some other embodiments less than 125% Δmicron2. According to some embodiments the absolute value of the volume V3 is between about 45 and 200% Δ microns2, for example between 60 and 200% A microns2, or for example between 60 and 190% Δ microns2, or between 45 and 175% Δ microns2, or between 60 and 175% Δ microns2, for example between 45 and 150% A microns2, or between 60 and 150% Δ microns2, between 80 and 150% Δ microns2, or between 60 and 125% Δ microns2, or between 80 and 125% Δ microns2 According to some embodiments 80% Δ-micron2≤|V3|≤200% Δ-micron2. microns2 According to some embodiments 70% Δ-micron2≤|V3|≤150% Δ-micron2. According to some embodiments 100% Δ-micron2≤|V3|≤150% Δ-micron2.
The core and cladding regions of fiber 100 may be produced in a single-step process or multi-step process by methods which are well known in the art. Suitable methods include: the double crucible method, rod-in-tube procedures, and doped deposited silica processes, also commonly referred to as chemical vapor deposition (“CVD”) or vapor phase oxidation. A variety of CVD processes are known and are suitable for producing the core and cladding layer used in the coated optical fibers of the present invention. They include external CVD processes, axial vapor deposition processes, modified CVD (MCVD), inside vapor deposition, and plasma-enhanced CVD (PECVD).
The glass portion of the coated fibers may be drawn from a specially prepared, cylindrical preform which has been locally and symmetrically heated to a temperature sufficient to soften the glass, e.g., a temperature of about 2000° C. for a silica glass. As the preform is heated, such as by feeding the preform into and through a furnace, a glass fiber is drawn from the molten material. See, for example, U.S. Pat. Nos. 7,565,820; 5,410,567; 7,832,675; and 6,027,062; the disclosures of which are hereby incorporated by reference herein, for further details about fiber making processes.
Based on our analysis the optical fibers 100 with an outer cladding layer 60 having an outer diameter of d5 of not greater than 126 microns can be bent to very tight bend radii rb and advantageously provide improved the mechanical reliability under tight bending conditions even in the presence of small abrasions to the glass surfaces, as can happen during assembly of miniature glass assemblies, or due to stripping off of the coating layer 70 from the fiber.
According to some exemplary embodiments (for example those of Tables 1-4) the inner cladding region 20 and/or the outer cladding region 40 has a substantially constant relative refractive index profile, i.e. the difference between the relative refractive index at any two radii within the inner cladding region is less than 0.02%, and in some preferred embodiments less than 0.01%. Thus, according to at least some embodiments disclosed herein the relative refractive index profile of the outer cladding region 40, has substantially flat shape. Also, according to at least some embodiments disclosed herein the relative refractive index profile of the inner cladding region 20 has substantially flat shape.
The central core region (1) may be a step index core, or as shown, for example in
According to some embodiments the optical fiber exhibits:
According to some embodiments 1200 nm<cable cutoff wavelength<1540 nm. According to some embodiments 1200 nm<cable cutoff wavelength<1540 nm, when deployed with an additional single bend around a 2.5 mm radius mandrel.
According to some embodiments the optical fiber exhibits:
(i) MFD1550>8 microns (e.g., 8.3 microns≤MFD1550≤10.5 microns or 8.5 microns≤MFD1550≤10.5 microns, and in some embodiments MFD1550>9 microns, for example 9 microns to 10.3 microns);
(ii) cable cutoff wavelength greater than 1260 nm and less than <1540 nm;
(iii) bend loss at 2.5 mm radius mandrel≤1 dB/turn;
(iv) bend loss at 5 mm radius mandrel<0.5 dB/turn
wherein the bend loss is macrobend loss and is measured at 1550 nm wavelength/
According to some embodiments the optical fiber exhibits 0.001 dB/turn<macrobend loss at 2.55 mm bend radius<0.55 dB/turn; and 0.001 dB/turn<macrobend loss at 5 mm bend radius<0.5 dB/turn; wherein the macrobend loss is measured at 1550 nm wavelength.
According to some exemplary embodiments the fiber exhibits:
MFD1550>8 microns (e.g., 8.3 microns≤MFD1550≤10.5 microns, for example 8.3 microns≤MFD1550≤10.5 microns, and in some embodiments MFD1550>9 microns, for example 9 microns to 10.3 microns));
Cable Cutoff <1570 nm;
Macrobend loss at 2.5 mm radius<0.5 dB/turn dB/turn, measured at a 1550 nm wavelength.
The fibers disclosed herein may be drawn from optical fiber preforms made using conventional manufacturing techniques and using known fiber draw methods and apparatus, for example as is disclosed in U.S. Pat. Nos. 7,565,820; 5,410,567; 7,832,675; 6,027,062, the specifications of which is hereby incorporated by reference.
Various exemplary embodiments will be further clarified by the following examples. It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the claims.
Tables 1A, 1B, and 2-5, below, list characteristics of illustrative modeled fiber examples 1-21 having a refractive index similar to that shown in
According to the exemplary embodiments of Tables 1A-5, the optical fiber has a mode field diameter at 1550 nm (MFD1550) of 8.3 microns≤MFD1550≤10.5 microns (e.g., 8.5 microns≤MFD1550≤10.5 microns), a single mode cutoff wavelength <1550 nm when bent 1 turn around a 2.5 mm radius mandrel, an effective area at 1550 nm of at least 65 micron2 and less than 85 micron2, and a bending loss at 1550 nm as determined by the mandrel wrap test using a mandrel comprising a radius of 2.5 mm-of ≤1.0 dB/turn.
The optical fiber has
The manufactured fiber 100 that has the refractive index profile of
The optical fibers (100) disclosed herein may be surrounded by the protective coating 70 that surrounds the second outer cladding layer 60, The protective coating may comprise a primary coating P contacting and surrounding the outer cladding region 60, the primary coating P having a Young's modulus of less than 1.0 MPa, preferably less than 0.9 MPa, and in some embodiments not more than 0.8 MPa, and in some embodiments not more than 0.5 MPa, and in some embodiments not more than 0.3 MPa, for example 0.1 to 1 MPa, and in some embodiments 0.1 to 0.5 MPa. The protective coating 70 further comprises a secondary coating S contacting and surrounding the primary coating P, the secondary coating S having a Young's modulus of greater than 1200 MPa, and in some embodiments greater than 1400 MPa, for example at least 1500 MPa, or at least 1600 MPa, at least 1800 MPa, or 1400 MPa to 2500 MPa or 1500 MPa to 2500 MPa. The lower modulus of the primary coating (e.g. <0.5 MPa supports good microbend performance, and higher modulus secondary coating (e.g., >1500 MPa) supports improve puncture resistance of the secondary coating, even when its thickness is reduced. According to some embodiments the outer diameter of the secondary coating S is not greater than 250 microns, for example not greater than 242 microns (e.g., ≤225 microns, ≤10 microns, or ≤00 microns), for example 175-242 microns, or 175 to 225 microns, or 180 to 200 microns. The above fiber designs enable good micro and macro bending performance even with coating diameters of less than 225 microns, which enables smaller diameter, lower cost, higher fiber density cables with excellent optical performance.
As used herein, the Young's modulus, elongation to break, and tensile strength of a cured polymeric material of a primary coating is measured using a tensile testing instrument (e.g., a Sintech MTS Tensile Tester, or an INSTRON Universal Material Test System) on a sample of a material shaped as a film between about 0.003″ (76 micron) and 0.004″ (102 micron) in thickness and about 1.3 cm in width, with a gauge length of 5.1 cm, and a test speed of 2.5 cm/min.
Additional description of suitable primary and secondary coatings can be found in PCT Publication WO2005/010589 which is incorporated herein by reference in its entirety.
The fibers disclosed herein exhibit low PMD values particularly when fabricated with OVD processes. Spinning of the optical fiber may also lower PMD values for the fiber disclosed herein.
It is to be understood that the foregoing description is exemplary only and is intended to provide an overview for the understanding of the nature and character of the fibers which are defined by the claims. The accompanying drawings are included to provide a further understanding of the preferred embodiments and are incorporated and constitute part of this specification. The drawings illustrate various features and embodiments which, together with their description, serve to explain the principals and operation. It will become apparent to those skilled in the art that various modifications to the preferred embodiments as described herein can be made without departing from the spirit or scope of the appended claims.
This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Ser. No. 62/413,605, filed on Oct. 27, 2016, the content of which is relied upon and incorporated herein by reference in its entirety.
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| 20170068046 | Bickham | Mar 2017 | A1 |
| Number | Date | Country |
|---|---|---|
| 2005010589 | Feb 2005 | WO |
| 2011109263 | Sep 2011 | WO |
| 2016168042 | Oct 2016 | WO |
| Entry |
|---|
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| Vethanayagam et al; “Mechanical Performance and Reliability of Corning Titan SMF CPC5 Fiber After Exposure to a Variety of Environments”; Proc. SPIE 1366, Fiber Optics Reliability, Feb. 1991; pp. 343-350. |
| International Search Report and Written Opinion PCT/US2017/058022 dated Jan. 25, 2018. |
| Number | Date | Country | |
|---|---|---|---|
| 20180120503 A1 | May 2018 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62413605 | Oct 2016 | US |
