Patent Application
20210349264
The present invention is generally directed to optical communications, and more specifically to optical devices that include multiple optical chips with direct optical coupling between the chips.
Passive optical networks are becoming prevalent in part because service providers want to deliver high bandwidth communication capabilities to customers. Passive optical networks are a desirable choice for delivering high-speed communication data because they may not employ active electronic devices, such as amplifiers and repeaters, between a central office and a subscriber termination. The absence of active electronic devices may decrease network complexity and/or cost and may increase network reliability.
The portion of the network 100 that is closest to central office 101 is generally referred to as the F1 region, where F1 is the “feeder fiber” from the central office 101. The portion of the network 100 closest to the end users 105 can be referred to as an F2 portion of network 100. The network 100 includes a plurality of break-out locations 102 at which branch cables are separated out from the main cable lines. Branch cables are often connected to drop terminals 104 that include connector interfaces for facilitating coupling of the fibers of the branch cables to a plurality of different subscriber locations 105.
An incoming signal is received from the central office 101, and is then typically split at the FDH 103, using one or more optical splitters (e.g., 1×8 splitters, 1×16 splitters, or 1×32 splitters) to generate different user signals that are directed to the individual end users 105. In typical applications, an optical splitter is provided prepackaged in an optical splitter module housing and provided with a splitter output in pigtails that extend from the module. The optical splitter module provides protective packaging for the optical splitter components in the housing and thus provides for easy handling for otherwise fragile splitter components. This modular approach allows optical splitter modules to be added incrementally to FDHs 103 as required.
It is desirable, however, to apportion the optical power output from the central office 101 equally among all users, which means that the optical splitter modules located closer to the central office 101 split off a smaller fraction of the incoming optical signal because the optical signal is strong, while optical splitter modules located further from the central office 101 split off a greater fraction of the incoming optical signal. The fraction of the optical signal split off from the main optical signal is referred to as the tapping fraction. For example, as shown in
To achieve an equal distribution of optical power among the four users 204, the optical tap modules 208a, 208b, 208c respectively split off ¼, ⅓ and ½ of the incident optical power. In other words, the tapping fractions of the splitter modules 208a, 208b and 208c are respectively ¼, ⅓ and ½. The optical splitter modules 208 each split off a fixed fraction of the incident optical power.
In another embodiment, schematically illustrated in
Thus, the technician installing the optical tap modules must be supplied with a variety of optical tap modules, that tap different fractions of the incident optical signal, depending on where the network the tap module is to be located. Furthermore, the larger the number of tap modules placed serially along the network, the greater the number of different tap modules that needs to be carried in inventory.
There is a need, therefore, to simplify the process of making optical splitter modules to reduce the numbers of types of optical splitter modules required to be carried in inventory.
One embodiment of the present invention is directed to an optical device that has a first optical chip having at least a first optical tap and a second optical tap. Each optical tap comprises an input waveguide, a main output waveguide and a tap waveguide. The first optical tap has a first tap ratio and the second optical tap has a second tap ratio. The second tap ratio is different from the first tap ratio. A second optical chip has an input waveguide coupled to a waveguide splitter network having a plurality of splitter output waveguides. The first and second optical chips are coupled together, the input waveguide of the second optical chip being coupled to receive an optical signal from one of the tap waveguides of the first optical chip.
Another embodiment of the present invention is directed to an optical device that includes a plurality of optical chips. A first optical chip has at least a first input waveguide and at least a first output waveguide. A second optical chip has at least a second input waveguide and at least a second output waveguide. The at least a second input waveguide of the second optical chip is coupled to receive an optical signal from the at least a first output waveguide of the first optical chip. Wherein one of the first and second optical chips is formed in a high index contrast platform and the other of the first and second optical chips is formed in a low index contrast platform.
Another embodiment of the invention is a method of forming an optical device that includes a first optical chip having a plurality of first optical functional elements having different operational characteristics, each first optical functional element having at least a first input waveguide and a first output waveguide. A second optical chip is provided, the second chip having a second optical functional element having at least a second input waveguide and at least a second output. One of the first optical functional elements of the first optical chip is selected. The at least a second input waveguide of the second optical chip is aligned to the at least a first output waveguide of the selected first optical element. The first and second optical chips are mounted so as to maintain the alignment of the at least a second input waveguide of the second optical chip to the at least a first output waveguide of the selected first optical element.
The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and the detailed description which follow more particularly exemplify these embodiments.
The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:
While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
The present invention is directed to providing optical circuits that are adjustable and that can take advantage of preferred manufacturing in different planar lightwave circuit (PLC) platforms.
The first optical chip 302 may be formed using any suitable optical waveguide technology, such as planar lightwave circuit (PLC). Waveguide systems are often defined by their refractive index contrast, which is given by (nc2-ncl2)/(2nc2). The refractive index contrast is usually presented as a percentage. For example, in some embodiments, waveguide structures are formed by doping in silica (silicon dioxide) and typically have a refractive index contrast less than 0.4% and, in many embodiments, have a refractive index contrast of around 0.1%. This type of waveguide structure, where the optical mode typically matches directly to the optical mode of a silica fiber, is referred to as a low index contrast structure. Other embodiments of waveguides can have a higher contrast ratio. For example, a waveguide formed in silicon (Si, nc=3.44 at 1550 nm) may have a contrast of around 35% when the cladding is silica (ncl=1.44 at 1550 nm), while a silicon nitride (SiN) waveguide (nc=1.99 at 1550 nm) may have a contrast of around 25%. Also, silica waveguides doped with a relatively high atomic number atom, such as titanium, can have a contrast ratio of 1.35%. Typically, high index contrast waveguides require matching of the optical mode field between the waveguide and a silica optical fiber, for example via a mode spot converter such as a waveguide taper. In general, refractive index contrast ratios less than 1% are considered low and while those above 1% are considered high.
The second optical chip 304 includes a 1:X splitter. In the illustrated embodiment, the second optical chip 304 includes a 1:4 splitter. The second optical chip 304 includes an input waveguide 312 coupled to the tap output waveguide 308 of the first chip. The input waveguide 312 leads to a 1:4 splitter network 314. There are four tap output waveguides 316 from the splitter network 314. In the illustrated embodiment, each split in the splitter section is a 50:50 split, so that each output tap waveguide 316 carries 25% of the tapped optical signal that enters the input waveguide 312, i.e. x/4%, where x % is the tapped optical signal. The second chip 304 may also include a main signal waveguide 318 that is coupled to receive the optical signal from the main output waveguide 310 of the first optical chip 302.
Like the first optical chip 302, the second optical chip 304 may be formed in a low index contrast platform, or in a high index contrast platform. The second optical chip 304 may include a different number of output waveguides, for example using a 1:2, 1:8, 1:16 splitter or the like. In other embodiments, the splitter section 314 of the second optical chip may direct different fractions of the input signal to respective output waveguides 316, in which case the magnitude of the signal at one or more of the output waveguide 316 may be different from the magnitudes of the optical signals at the other output waveguides 316.
One approach to manufacturing a hybrid coupled-chip optical device is now described with reference to
Turning first to
In the illustrated embodiment there are four optical taps 402a-402d, with respective input waveguides 404a-404d, tap waveguide 406a-406d and main output waveguides 408a-408d. Each tap 402 has a different tap ratio. For example, the first tap waveguide 406a may carry W % of the signal propagating along the input waveguide 404A, while the second tap waveguide 406b carries X % of the optical signal propagating along the second input waveguide 404b, the third tap waveguide 406c carries Y % of the optical signal propagating along the third input waveguide 404c and the fourth tap waveguide 406d carries Z % of the optical signal propagating along the fourth input waveguide 404d, where W, X, Y and Z are all different. For example, in some embodiments, W<X<Y<Z.
The broadband tap 402 may be designed to tap a fraction of light from the input waveguide. If the chip 400 covers a sufficiently broad range of tap fractions, the different taps 402 may include different designs. For example, in some embodiments, the taps 402 may include adiabatic couplers, or other types of coupler, to tap a desired percentage of light from the input waveguide 404a-404d.
The chip 500 may be processed to reduce the splitting ratio. For example, the chip 500 may be cleaved along line 510 using precision dicing to produce the cleaved chip 520 illustrated in
The chip 500 may be formed in a low index contrast platform, or in a high index contrast platform. In other embodiments, the splitter section of the second optical chip 500 may direct different fractions of the input signal to respective output waveguides, rather than the same fraction, in which case the magnitude of the signal at one or more of the output waveguides may be different from the magnitudes of the optical signals at the other output waveguides. In other embodiments, the splitter network may have a number of outputs that is not equal to a power of two. For example, if the y-splitter that has output waveguides 508g and 508h were to be replaced by a single waveguide, then the splitter network 506a on chip 500 would have seven output waveguides, rather than eight.
In some embodiments, the waveguide 502 need not act as a bypass but may be used as an input to a second splitter network 506d that has a number of outputs 512b, as illustrated in
Because the tap chip 400 has a number of different tap outputs, and because the splitter chip 500 has a number of possible splitter arrangements, it is advantageously possible to manufacture a wide variety of tap/splitter assemblies from a small number of parts.
An embodiment of an optical tap/splitter 700 using the coupled tap and splitter chips is schematically illustrated in
A second alignment block 708, for example a v-groove block, is located at the output end of the splitter chip 500. A main signal optical fiber 710 is mounted in the second alignment block 708 in alignment with the bypass output waveguide 502b of the splitter chip 500. A number of optical fibers 712 are mounted in the second alignment block 708 in alignment with the splitter chip output waveguides 508a-508h. The main signal optical fiber 710 and the optical fibers 712 may be fiber pigtails.
It will be appreciated that an optical tap/splitter according to the present invention may be different from the embodiments illustrated. For example, the tap chip may include a different number of tap channels that each have a different tap ratio, the splitter chip may be aligned with any one of the tap channels of the tap chip, and the splitter chip may have a different splitter ratio, and hence include more or fewer outputs than those illustrated.
The assembly of the optical components to make the optical tap/splitter 700 may be carried out using standard integrated optical fabrication techniques. One approach is discussed with reference to
After alignment with the fiber 1104, a second chip 1110 may be aligned to the output of the first chip 1102 using a similar procedure, as shown in
Once the first and second chips 1102, 1110 are mounted together, output fibers 1112 may be aligned to the various outputs of the second chip 1110, as schematically illustrated in
It will be appreciated that other procedures may be followed to assemble the components. For example, the adhesive may be applied between components before their relative positions are optimized. In another example, the device may be formed by adding more than just a second ship to the first chip. For example, a third chip may be added to the second chip once the second chip has been mounted to the first chip.
Another embodiment of a coupled-chip optical device 800 is schematically illustrated in
The coupled-chip optical device 800 includes a first chip 802, a second chip 804 and a third chip 806. In this embodiment, the first chip 802 includes an input waveguide 810 coupled to an arrayed waveguide grating (AWG) 812. The AWG 812 separates a wavelength division multiplexed optical signal received from the input waveguide 810 into its different wavelength components, which are directed along single wavelength waveguides 814a-814d that carry respective single wavelength components of the WDM optical signal received by the chip 802 along the input waveguide 810.
The single wavelength waveguides 814a-814d are optically coupled to respective input waveguides 820a-820d on the second chip 804. The second chip 804 includes an optical switch array 822 that includes optical switches 824a-824d coupled to receive optical signals along respective input waveguides 820a-820d. Each optical switch 824a-824d is operable to switch its incoming optical signal between a respective output waveguide 826a-826d, that couples to the third chip 806, and a respective switched output waveguide 828a-828d. When in the bar state an optical switch 824a-824d passes the incoming optical signal on to the output waveguide 826a-826d. If, on the other hand, the optical switch 824a-824d is in the cross state, then the incoming optical signal is directed to the switched output waveguide 828a-828d. The optical switches 824a-824d may be any suitable type of optical waveguide switch, such as electro-optic switches, interferometric switches, totally internally reflecting (TIR) switches, switched couplers, microfluidically activated switches such as electro-wetting on dielectric (EWOD) adiabatic or TIR switches, liquid crystal-based switches, microelectromechanical systems (MEMS) switches, or the like.
The second optical chip 804 is coupled to the third chip 806, so that the output waveguides 826a-826d of the second optical chip 804 are aligned with the input waveguides 830a-830d of the third optical chip 806. The input waveguides 830a-830d connect to a second AWG 832 that combines the signals, at different wavelengths, propagating along the input waveguides 830a-830d into a single WDM optical signal that propagates along the output waveguide 834.
The coupled-chip optical device 800 may be included within a housing, and be provided with connections via fiber pigtails, e.g. to the input waveguide 810, the output waveguide 834 and one or more of the switched output waveguides 828a-828d. The coupled-chip optical device 800 may operate as an add/drop multiplexer, where one or more of the wavelength components of the WDM signal is dropped and directed via the switched output waveguides to a branch network.
It will be appreciated that the coupled-chip optical device 800 may operate in the reverse direction to add a wavelength component to a WDM signal, with optical signals entering the device 800 along waveguide 834 and one or more of waveguides 828a-828d, and leaving along waveguide 810.
In some embodiments, the first and third optical chips 802, 806 are formed in a high index contrast platform, for example using silicon or silicon nitride waveguides, while the switch array 822 of the second optical chip 804 is fabricated using silica waveguides. Thus, the coupled-chip device 800 includes both a high index contrast chip, first and third optical chips 802, 806, and a low index contrast chip 804.
Different types of optical function may be included in a coupled-chip device that uses chips of different index contrast platforms, referred to herein as a hybrid coupled-chip device. For example, certain operations such as dispersive separation, as is found in an AWG, may be implemented in a high index contrast platform and other operations, such as switching, e.g. TIR switching, and optical signal splitting in a y-coupler network may be implemented in a low index contrast network.
At least one output waveguide 914 from the first functional section 912 couples to the second optical chip 904. The cross-sectional dimensions of single mode waveguides in the high index contrast chip platform are typically less than those of single mode waveguides fabricated in a low index contrast platform. It is advantageous to maximize the coupling efficiency for light propagating between waveguides fabricated in the two different types of platform. One approach to maximizing coupling efficiency is illustrated in
The input waveguide 920 transmits light from the first optical chip 902 to the second functional section 922 that operates on the optical signal. The operation may be any desired optical operation that is suitably enabled in a low index contrast platform, such as splitting with a network of y-couplers, switching, and the like. In the illustrated embodiment, four output waveguides 924a-924d transmit respective optical signals from the second functional section 922 to the output of the second chip 904.
The present invention is not intended to be limited to only the illustrated embodiments, but also many different variations thereof. For example, it is not restricted in the number of optical chips that may be coupled together to provide a coupled-chip optical device. Furthermore, it is not intended to be restricted in the number of input waveguides or output waveguides, nor in the number of input fibers or output fibers that may be coupled to the coupled-chip device. The coupled-chip device may be incorporated within a housing and provided with optical fiber connections, for example optical fiber pigtails. An exemplary embodiment, illustrated in
The input waveguides 1010 lead to the optical function section 1016 of the first optical chip 1004, which may include any of the functionalities described above. The output waveguides 1018 of the first optical chip 1004 couple from the optical function section 1016 to the second optical chip 1006. The output waveguides 1018 may also include tapered sections 1018a for mode coupling if the input waveguides 1020 of the second optical chip 1006 have a different dimension from that of the output waveguide 1018. The input waveguides 1020 of the second chip 1006 carry signals from the first chip 1004 to the second optical function section 1022, which may include any of the functionalities described above. Output waveguides 1024 from the second optical function section 1022 couple optical signals between the second optical function section 1022 and output fibers 1026. The output fibers 1026 may be mounted in an alignment block 1028 for accurate alignment to the output waveguides 1024. The output fibers 1026 pass through the wall of the housing 1002 and may be fiber pigtails.
The convention adopted in the present description is that light signals enter the device from the left and propagate to the right, in which case waveguides and optical fibers on the left side of a device have been referred to as input waveguides or fibers, and those on the right as output waveguides of fibers. It will be appreciated that many optical devices can operate on light propagating through the device in different directions. For example, an AWG can operate as a wavelength demultiplexer for light signals propagating in one direction through the device and as a wavelength multiplexer for light signals propagating in the opposite direction. Accordingly, although various waveguides and fibers are labeled as “input” and “output” in this description, it should be understood that they are used only for ease of description. The labels “input” and “output” have been used herein for convenience, and it should be understood that the waveguides and optical fibers described herein may carry optical signals in both directions and may operate to input an optical signal to a device and also to output a signal from an optical device.
Various modifications, equivalent processes, as well as numerous structures to which the present invention may be applicable will be readily apparent to those of skill in the art to which the present invention is directed upon review of the present specification. The claims are intended to cover such modifications and devices.
As noted above, the present invention is applicable to fiber optical communication and data transmission systems. Accordingly, the present invention should not be considered limited to the particular examples described above, but rather should be understood to cover all aspects of the invention as fairly set out in the attached claims.
This application is being filed on Oct. 4, 2019 as a PCT International Patent Application and claims the benefit of U.S. Patent Application Ser. No. 62/741,918, filed on Oct. 5, 2018, the disclosure of which is incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2019/054732 | 10/4/2019 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62741918 | Oct 2018 | US |
