Dense wavelength division and multiplexing scheme for integrated photonic circuits.

Abstract

Disclosed are apparatus and methods for generating dense wavelength division and multiplexing (DWDM) optical streams in a photonic integrated circuit (PIC). An optical input source containing several (N) optical channels (wavelengths) can be demultiplexed (deinterleaved) into multiple optical streams, each containing a corresponding subset of the optical channels of the optical input source. Each of the multiple demultiplexed optical streams can be modulated with an associated set of data streams by a silicon-based microring modulator to generate a corresponding modulated optical stream. A first pair of modulated optical streams can be combined (interleaved) to generate a first optical output stream containing N / 2 modulated optical channels, and a second pair of modulated optical streams can be combined (interleaved) to generate a second optical output stream containing N / 2 modulated optical channels. The channel spacing of the first and second optical output streams can be twice the channel spacing of the optical input source.

Description

[Technical field]

[0001] Aspects of the present disclosure relate generally to integrated optical circuits, and more particularly to dense wavelength division and multiplexing schemes for transmitting and receiving optical signals. [Background technology]

[0002] Optical interconnection technologies can be used to provide high-speed, low-power input / output (I / O) interfaces for integrated circuits. As the complexity and density of integrated circuits increases, so does the bandwidth demand imposed on the optical I / O interfaces. For example, some integrated circuits may contain hundreds or even thousands of optical I / O interfaces to meet the bandwidth demand. Each optical I / O interface typically requires a photonic I / O cell to terminate a corresponding optical fiber, and thus hundreds or thousands of optical fibers may be required to meet the bandwidth demand. It may be infeasible to fit hundreds or thousands of optical fibers into an IC package.

[0003] Some integrated circuits may use silicon-based optical ring modulators to modulate data for optical I / O interfaces. Silicon-based optical ring modulators generally have a fixed free spectral range (FSR) and minimum channel spacing that may limit the number of optical channels that can be supported in a given fiber, which unnecessarily limits channel density. Therefore, more efficient use of fiber bandwidth is needed so that the number of optical fibers and corresponding photonic I / O cells required to support a given I / O bandwidth can be reduced. Summary of the Invention

[0004] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter. Moreover, the systems, methods, and devices of the present disclosure each have several inventive aspects, no single inventive aspect of which is solely responsible for the desirable attributes disclosed herein.

[0005] One inventive aspect of the subject matter described in this disclosure may be implemented in an optical modulation circuit to generate a dense wavelength division and multiplexing (DWDM) modulated optical stream. In some embodiments, the optical modulation circuit may include an input terminal, a first channel de-interleaver, a second channel de-interleaver, a first microring modulator (MRM) array, a second MRM array, and a first optical interleaver. The input terminal may receive an optical input source including a plurality of optical channels or optical wavelengths. The first channel de-interleaver may be configured to separate the optical input source into a first optical stream and a second optical stream, and the second channel de-interleaver may be configured to separate the first optical stream into a first separated optical stream and a second separated optical stream. The first MRM array may be configured to modulate a first set of data streams onto the optical channels of the first separated optical stream to generate a first modulated optical stream, and the second MRM array may be configured to modulate a second set of data streams onto the optical channels of the second separated optical stream to generate a second modulated optical stream. The first optical interleaver may be configured to generate a first optical output stream based on the first and second modulated optical streams. In some aspects, the first optical stream includes odd-numbered optical channels of the optical input source, and the second optical stream includes even-numbered optical channels of the optical input source. Additionally or alternatively, the first separated optical stream includes a first set of alternating optical channels of the first optical stream, and the second separated optical stream includes a second set of alternating optical channels of the first optical stream, and the first set of alternating optical channels is different from the second set of alternating optical channels.

[0006] The optical modulation circuit may also include a third channel deinterleaver, a third MRM array, a fourth MRM array, and a second optical interleaver. The third channel deinterleaver may be configured to separate the second optical stream into a third separated optical stream and a fourth separated optical stream. The third MRM array may be configured to modulate a third set of data streams onto the optical channels of the third separated optical stream to generate a third modulated optical stream, and the fourth MRM array may be configured to modulate a fourth set of data streams onto the optical channels of the fourth separated optical stream to generate a fourth modulated optical stream. The second optical interleaver may be configured to generate a second optical output stream based on the third and fourth modulated optical streams.

[0007] Another inventive aspect of the subject matter described in this disclosure may be implemented in a photonics integrated circuit. The photonics integrated circuit may include a plurality of optical modulation circuits and a plurality of optical detection circuits. Each optical modulation circuit may include an input terminal for receiving a plurality of optical channels or optical wavelengths from an optical source. Each optical detection circuit may have an input terminal for receiving a plurality of modulated optical channels from an external source. In some embodiments, each of the optical modulation circuits may include a first channel deinterleaver, a second channel deinterleaver, a third channel deinterleaver, a plurality of microring modulation (MRM) arrays, a first optical interleaver, and a second optical interleaver. The first channel deinterleaver may be configured to separate the optical input source into a first optical stream and a second optical stream, the second channel deinterleaver may be configured to separate the first optical stream into a first separated optical stream and a second separated optical stream, and the third channel deinterleaver may be configured to separate the second optical stream into a third separated optical stream and a fourth separated optical stream. Each of the plurality of MRM arrays may be configured to modulate a unique set of data streams onto an optical channel of a corresponding separated optical stream of the separated optical streams to generate each of the first modulated optical stream, the second modulated optical stream, the third modulated optical stream, and the fourth modulated optical stream. The first optical interleaver may be configured to generate a first optical output stream based on the first and second modulated optical streams, and the second optical interleaver may be configured to generate a second optical output stream based on the third and fourth modulated optical streams.

[0008] In some embodiments, the first separated light stream includes a first set of alternating light channels of the first light stream, the second separated light stream includes a second set of alternating light channels of the first light stream, the third separated light stream includes the first set of alternating light channels of the second light stream, and the fourth separated light stream includes the second set of alternating light channels of the second light stream. In some aspects, the first separated light stream includes odd numbered light channels of the light input source and the second separated light stream includes even numbered light channels of the light input source.

[0009] Another inventive aspect of the subject matter described in this disclosure may be implemented as a method. In some embodiments, the method may include splitting an optical input source into a first optical stream and a second optical stream, splitting the first optical stream into a first separated optical stream and a second separated optical stream, modulating a first set of data streams onto the optical channels of the first separated optical stream to generate a first modulated optical stream, modulating a second set of data streams onto the optical channels of the second separated optical stream to generate a second modulated optical stream, and generating a first optical output stream based on a combination of the first modulated optical stream and the second modulated optical stream. In some aspects, the first optical stream includes odd-numbered optical channels of the optical input source and the second optical stream includes even-numbered optical channels of the optical input source. Additionally or alternatively, the first separated optical stream includes a first set of alternating optical channels of the first optical stream and the second separated optical stream includes a second set of alternating optical channels of the first optical stream, the first set of alternating optical channels being different from the second set of alternating optical channels.

[0010] The method may also include splitting the second optical stream into a third separated optical stream and a fourth separated optical stream, modulating a third first set of data streams onto the optical channels of the third separated optical stream to generate a third modulated optical stream, modulating a fourth set of data streams onto the optical channels of the fourth separated optical stream to generate a fourth modulated optical stream, and generating a second optical output stream based on a combination of the third modulated optical stream and the fourth modulated optical stream.

[0011] Exemplary implementations are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings. Like numbers refer to like elements throughout the drawings and this specification. It should be noted that the relative dimensions of the following figures may not be to scale. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a block diagram of an example photonics integrated circuit, according to some implementations. [Figure 2A] 1 is a block diagram of an exemplary light modulation circuit, according to some implementations. [Figure 2B] 2B is a functional diagram illustrating an example operation of the light modulation circuit of FIG. 2A according to some implementations. [Diagram 3] 1 is a simplified block diagram of a microring modulator according to some implementations. [Figure 4] 4 is an example graph illustrating example characteristics of the microring modulator of FIG. 3 according to some implementations. [Diagram 5] 2B is a chart of an example channel assignment for the optical modulation circuit of FIG. 2A according to some implementations. [Figure 6] FIG. 1 is a block diagram of an example microring modulation array, according to some implementations. [Figure 7] 1 is an example flowchart illustrating example operations for generating a light output according to some implementations. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Energy-efficient photonics integrated circuits (PICs) can be used to meet the ever-increasing input / output (I / O) bandwidth requirements of large-scale data processing circuits, such as those deployed in next-generation data centers, which can exceed 100 Terabits per second (Tbps). Photonics ICs are typically coupled to each of several optical fibers using corresponding photonic I / O cells that provide an interface between the optical fibers and the optical circuits provided within the photonics IC. Photonics ICs can use wavelength division multiplexing (WDM), for example, to place multiple optical wavelengths on each optical fiber such that the outer circumference of the photonics IC can physically accommodate the optical fibers and their corresponding photonic I / O cells, thereby reducing the number of optical fibers required to achieve a given bandwidth. Multiple microring modulators coupled to a common bus waveguide using staggered resonance to match channel wavelengths carried in the bus waveguide can be used to modulate data onto multiple wavelengths by having multiple microrings. However, the number of channels that can be provided in each optical waveguide is limited by the free spectral range (FSR) of the microring modulator. Furthermore, optical signals generally require a minimum channel spacing to avoid crosstalk and other interference between adjacent channels, which can also limit the number of channels that can be provided on each optical signal.

[0014] Implementations of the subject matter described in this disclosure may be used to increase the number of optical channels provided onto an optical fiber beyond the limits typically imposed by microring modulators. According to various aspects of the present disclosure, a photonics IC may include a plurality of optical modulation circuits that may increase the number of optical channels provided onto a given optical fiber by using a dense wavelength division and multiplexing (DWDM) scheme to modulate data onto a plurality of optical channels of one or more optical signals. In some implementations, each optical modulation circuit may receive an optical input source including several (N) optical wavelengths and may separate the optical input source into a plurality of optical streams, each including a corresponding subset of the wavelengths of the optical input source. Each of the plurality of separated optical streams may be modulated with a plurality of data streams by a corresponding plurality of microring modulators to generate a corresponding modulated optical stream. A first pair of the modulated optical streams may be combined to generate a first optical output stream including a first set of N / 2 modulated optical channels, and a second pair of the modulated optical streams may be combined to generate a second optical output stream including a second set of N / 2 modulated optical channels.

[0015] In some implementations, the optical input source may include 32 wavelengths (frequencies) in the O band (close to 1310 nm) with a channel spacing of about 65 GHz, and the first channel deinterleaver may separate the optical input source into a first optical stream and a second optical stream. The first optical stream may include 16 odd-numbered channels of the optical input source and may have a channel spacing of about 130 GHz, and the second optical stream may include 16 even-numbered channels of the optical input source and may have a channel spacing of about 130 GHz. The second channel deinterleaver may separate the first optical stream into a first separated optical stream and a second separated optical stream, and the third channel deinterleaver may separate the second optical stream into a third separated optical stream and a fourth separated optical stream. The first separated optical stream may be modulated with a first set of data streams by a first MRM array coupled to a first waveguide carrying these channels to generate a first modulated optical stream. The second separated optical stream on the second waveguide may be modulated with a second set of data streams by a second MRM array coupled to the second waveguide to generate a second modulated optical stream. The third separated optical stream on the third waveguide may be modulated with a third set of data streams by a third MRM array coupled to the third waveguide to generate a third modulated optical stream. The fourth separated optical stream on the fourth waveguide may be modulated with a fourth set of data streams by a fourth MRM array coupled to the fourth waveguide to generate a fourth modulated optical stream. In some embodiments, each of the first, second, third, and fourth modulated optical streams may include a corresponding set of eight wavelengths with a channel spacing of about 260 GHz.

[0016] The first modulated optical stream and the second modulated optical stream may be combined in a first optical interleaver to generate a first optical output stream, and the third modulated optical stream and the fourth modulated optical stream may be combined in a second optical interleaver to generate a second optical output stream. Each of the first and second optical output streams may include 16 optical channels and may have a channel spacing of about 130 GHz, which is twice the channel spacing of the optical input source. For target modulation rates that may exceed 50 Gigabaud, combining further channels may be undesirable because smaller channel spacings may result in spectral overlap of the modulated channels, which may cause signal degradation.

[0017] In the following description, numerous specific details are set forth, such as examples of specific components, circuits, and processes, to provide a thorough understanding of the present disclosure. As used herein, the term "coupled" means directly coupled or coupled through one or more intervening components or circuits. Also, in the following description, for purposes of explanation, specific names and / or details are set forth to provide a thorough understanding of the exemplary implementations. However, it will be apparent to one skilled in the art that these specific details may not be required to practice the exemplary implementations. In other instances, well-known circuits and devices are shown in block diagram form to avoid obscuring the present disclosure. Any of the signals provided via the various buses described herein may be time multiplexed with other signals and provided via one or more common buses. Additionally, the interconnections between circuit elements or software blocks may be depicted as buses or as single signal lines. Each of the buses may alternatively be a single signal line, and each of the single signal lines may alternatively be a bus, with a single line or bus representing any one or more of the myriad physical or logical mechanisms for communication between components. Exemplary implementations should not be construed as limited to the specific examples described herein, but rather as including within their scope all implementations as defined by the appended claims.

[0018] 1 is a block diagram of a portion of an example photonics integrated circuit (IC) 100 according to some implementations. The photonics IC 100 may include a first number (N) of optical modulation circuits 110(1)-110(N) and a second number (M) of optical detection circuits 120(1)-120(M), where each of the first number N and the second number M may be any suitable non-zero integer. Each of the optical modulation circuits 110(1)-110(N) may receive multiple egress data channels (D egr ), and an optical input source (OS in ), and an optical input coupled to an optical egress link (L egr Although not shown in FIG. 1 for simplicity, each of the optical modulation circuits 110(1)-110(N) may include an optical output coupled to an associated optical input source OS by a first photonic I / O cell. in , and the second and third photonic I / O cells can couple the optical egress link L egr The optical input source OS in may be integrated onto the photonics IC 100 or may be received via an optical fiber external to the photonics IC 100.

[0019] In some implementations, each of the optical modulation circuits 110(1)-110(N) is connected to an associated input data channel (D in ) and can receive multiple data streams provided on an optical input source (OS in ), and may be configured to modulate the optical input with the multiple received data streams to generate one or more modulated optical signals including data associated with the multiple received data streams. In some aspects, each of the optical modulation circuits 110(1)-110(N) may include multiple micro-ring modulators (not shown in FIG. 1 for simplicity) for modulating the optical input with data associated with a corresponding multiple received data streams. The one or more modulated optical signals generated by each of the optical modulation circuits 110(1)-110(N) may be coupled to an optical egress link L for transmission to one or more other circuits or devices (not shown for simplicity). egr , may be given to corresponding pairs of

[0020] In the exemplary implementation of FIG. 1, each of the optical modulation circuits 110(1)-110(N) has 32 associated egress (or transmit) data channels (D egr ) and can receive 32 independent data streams via the associated optical input source OS in In some implementations, the optical modulation circuits 110(1)-110(N) may receive unmodulated light having 32 evenly spaced wavelengths from a single optical input source and may use multiple microring modulators to modulate 32 independent data streams onto the corresponding wavelengths of the received optical input source. In some implementations, each of the optical modulation circuits 110(1)-110(N) may modulate one optical egress link L egr 1 may combine a group of 16 modulated optical channels for transmission over an optical egress (or transmit) link L, such that each of the optical modulation circuits 110(1)-110(N) of FIG. egr For example, the first optical modulation circuit 110(1) may be capable of modulating and combining 32 optical channels for transmission on corresponding pairs of first light source OS in、1A first set of egress data channels D on the optical input given by egr、1 32 independent data streams received via the corresponding pair of optical egress links L egr、1-1 and L egr、2-1 Similarly, the Nth optical modulation circuit 110(N) may generate two groups of modulated optical signals for transmission on the Nth optical input source OS in、N On the optical input given by egr、N 32 independent data streams received via the corresponding pair of optical egress links L egr、N-1 and L egr、N-2 1 may generate two groups of modulated optical signals for transmission over

[0021] In other implementations, each of optical modulation circuits 110(1)-110(N) may receive other suitable numbers of data streams and optical wavelengths, may be coupled to other numbers of optical links, and / or may include other circuitry suitable for modulating and combining multiple optical channels for transmission through one or more optical egress links.

[0022] Each of the photodetection circuits 120(1) to 120(M) detects an associated optical ingress link (L ing ), and a number of ingress data channels (D ing Although not shown in FIG. 1 for simplicity, each of the photodetection circuits 120(1)-120(M) may include an electrical output coupled to an associated optical ingress link L ing In some implementations, each of the optical detection circuits 120(1)-120(M) may be coupled to an associated optical ingress link L ingThe optical detector circuits 120(1)-120(M) may receive the modulated optical signals given above and may be configured to demodulate the received modulated optical signals to decode data contained in the received modulated optical signals. In some aspects, each of the optical detector circuits 120(1)-120(M) may transmit the received data to an associated ingress data channel D. ing may be provided as multiple data streams.

[0023] In the exemplary implementation of FIG. 1, each of the optical detection circuits 120(1)-120(M) may receive a modulated optical signal having 16 channels, including an ingress data channel D ing In some aspects, each of the 16 data streams may be configured to demodulate a received optical signal to generate 16 data streams for output onto a corresponding set of optical ingress links L. ing For example, the first photodetector circuit 120(1) may include data extracted from a corresponding one of the 16 channels of the modulated optical signal received from the first set of ingress data channels D ing、1 A first optical ingress link L is used to generate 16 separate data streams for output onto the ing、1 , and so on, the Mth optical demodulation circuit 120(M) may demodulate the data encoded on the 16 channels of the optical signal received from the Mth set of ingress data channels D ing、M 1, the Mth optical ingress link L is connected to the Mth optical ingress link L to generate 16 separate data streams for output on the ing、M The optical fiber 100 may demodulate data encoded on 16 channels of an optical signal received from

[0024] 2A is a block diagram of an example light modulation circuit 200 according to some implementations. The light modulation circuit 200, which may be an example of the light modulation circuits 110(1)-110(N) of FIG. 1, is a light modulation circuit for modulating an associated light source L in Optical input source from OS in and a first input for receiving an associated egress data channel D egra second input for receiving a plurality of data streams provided as data sets DS1 to DS4 from each optical egress link L egr、1 and L egr、2 Two optical outputs on Stream OS out1 and OS out2 In the example of FIG. 2A, the optical modulation circuit 200 is shown to include a first channel deinterleaver 210, a pair of second channel deinterleavers 220(1)-220(2), a number of microring modulator (MRM) arrays 230(1)-230(4), and a number of optical interleavers 240(1)-240(2). The first channel deinterleaver 210 receives an optical input source OS in , includes a first output coupled to a channel deinterleaver 220(1) and includes a second output coupled to a channel deinterleaver 220(2). The channel deinterleaver 220(1) includes a first output coupled to a first MRM array 230(1) and includes a second output coupled to a second MRM array 230(2). The channel deinterleaver 220(2) includes a first output coupled to a third MRM array 230(3) and includes a second output coupled to a fourth MRM array 230(4). Each of the first and second MRM arrays 230(1)-230(2) includes an output coupled to a first optical channel interleaver 240(1), and each of the third and fourth MRM arrays 230(3)-230(4) includes an output coupled to a second optical channel interleaver 240(2). The first optical channel interleaver 240(1) is a first optical egress link L egr、1 a second optical channel interleaver 240(2) including an output coupled to a second optical egress link L egr、2 Includes outputs coupled to

[0025] Optical input source OS in may provide a number of optical wavelengths onto which a corresponding number of data streams may be modulated. egr、1 and L egr、2Each of the optical modulation circuits 200 may provide a plurality of optical channels over which a corresponding plurality of optical signals may be transmitted. egr、1 and L egr、2 The optical input source OS uses data associated with a corresponding data stream to generate a number of modulated optical channels that can be transmitted via in In some implementations, the optical input source OS in may provide 32 wavelengths upon which 32 independent data streams may be modulated by optical modulation circuit 200, and egress data channel D egr may provide 32 channels over which up to 32 independent data streams may be received by the optical modulation circuit 200. In such an implementation, the optical modulation circuit 200 may include an optical egress link L egr、1 and L egr、2 In some embodiments, the optical modulation circuit 200 may be configured to modulate each of the 32 input optical wavelengths with data from a corresponding data stream to generate two groups of modulated optical signals for transmission on the first optical egress link L. egr、1 First optical output stream on OS out1 and a second optical egress link L. egr、2 Second optical output stream on OS out2 The optical fiber 10 may be configured to combine a second group of 16 modulated optical signals for transmission as a modulated optical signal.

[0026] Optical input source OS in Each of the optical channels associated with the optical egress link L may be characterized by a distinct wavelength and may be spaced apart from adjacent optical channels by a fixed channel spacing. egr、1 and L egr、2Each of the optical channels associated with the optical input source OS may be characterized by a distinct wavelength and may be spaced apart from adjacent optical channels by a fixed channel spacing. in can provide 32 independent optical wavelengths with a channel spacing of about 65 GHz, and the first and second optical egress links L egr、1 and L egr、2 Each of these can provide 16 independent optical channels with a channel spacing of approximately 130 GHz.

[0027] In an exemplary operation, the first channel deinterleaver 210 deinterleaves a received optical input source OS to generate a first optical stream 211 and a second optical stream 212. in In some implementations, the first optical stream 211 may be a light input source OS in , and the second optical stream 212 may include the “odd” numbered optical channels of the optical input source OS in For example, the optical input source OS in In an implementation including 32 optical channels CH1-CH32, the first optical stream 211 is in 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, in Each of the first optical stream 211 and the second optical stream 212 may include an optical input source OS in Optical input source OS to include alternate optical channels in By separating the first optical stream 211 and the second optical stream 212, the channel spacing within each of the first optical stream 211 and the second optical stream 212 is in Therefore, the optical input source OS in In an implementation where the channel spacing between the first and second optical streams is about 65 GHz, the channel spacing within each of the first and second optical streams 211 and 212 may be about 130 GHz. inIt should be understood that the above enumerates consecutive optical channels within a single optical channel and is not intended to limit any particular optical channel to any particular frequency or wavelength. In other implementations, the first optical stream 211 is connected to an optical input source OS in , and the second optical stream 212 may include even numbered optical channels from the optical input source OS in The optical channel may include odd numbered optical channels.

[0028] The channel deinterleaver 220(1) may separate the first optical stream 211 to generate a first separated optical stream 221 and a second separated optical stream 222. In some implementations, the first separated optical stream 221 may include a first set of alternating channels of the first optical stream 211, and the second separated optical stream 222 may include a second set of alternating channels of the first optical stream 211. In other implementations, the first separated optical stream 221 may include a second set of alternating channels of the first optical stream 211, and the second separated optical stream 222 may include a first set of alternating channels of the first optical stream 211. In this manner, each of first separated optical stream 221 and second separated optical stream 222 may include alternating optical channels of first optical stream 211, which may enable the channel spacing within each of first separated optical stream 221 and second separated optical stream 222 to be twice the channel spacing of first optical stream 211. Thus, for an implementation in which the channel spacing of first optical stream 211 is approximately 130 GHz, the channel spacing within each of first separated optical stream 221 and second separated optical stream 222 may be approximately 260 GHz.

[0029] Similarly, the channel deinterleaver 220(2) may separate the second optical stream 212 to generate a third separated optical stream 223 and a fourth separated optical stream 224. In some implementations, the third separated optical stream 223 may include a first set of alternating channels of the second optical stream 212, and the fourth separated optical stream 224 may include a second set of alternating channels of the second optical stream 212. In other implementations, the third separated optical stream 223 may include a second set of alternating channels of the second optical stream 212, and the fourth separated optical stream 224 may include a first set of alternating channels of the second optical stream 212. In this manner, each of the third separated optical stream 223 and the fourth separated optical stream 224 may include alternating optical channels of the second optical stream 212, which may allow the channel spacing within each of the third separated optical stream 223 and the fourth separated optical stream 224 to be twice the channel spacing of the second optical stream 212. Thus, for implementations in which the channel spacing of the second optical stream 212 is approximately 130 GHz, the channel spacing within each of the third separated optical stream 223 and the fourth separated optical stream 224 may be approximately 260 GHz.

[0030] In some implementations, each of the MRM arrays 230(1)-230(4) may include a plurality of micro-ring modulators (not shown in FIG. 2A for simplicity) configured to modulate an associated optical signal with data from a corresponding data stream. A given micro-ring modulator in the MRM arrays 230(1)-230(4) may be a silicon-based optical device capable of modulating an optical channel (e.g., a particular wavelength of light) with data from a corresponding data stream. In some aspects, each of the micro-ring modulators may be characterized by a free spectral range (FSR), which is the distance separation (in wavelength or frequency) between adjacent resonances that defines the range of wavelengths or frequencies that an optical channel may be accommodated within. In some aspects, each of the MRM arrays 230(1)-230(4) may have a modulation rate of approximately 56 Gbps. Thus, each of the micro-ring modulators may modulate only optical channels having wavelengths within the FSR of that micro-ring modulator. For example, a micro-ring modulator having a radius of 5 microns may have an FSR equal to approximately 13.5 nm. The Q-factor (or width of resonance) of the microring, as defined by the target channel symbol rate, sets the minimum channel spacing. For example, with a symbol rate of approximately 56 Gbps, this channel spacing may be 1.5 nm for optical wavelengths near 1310 nm (or in the O band). In this scenario, each MRM array 230 may accommodate only eight wavelengths. As described in more detail below, the optical modulation circuit 200 modulates the optical input source OS in a manner that may enable the microring modulator described above to simultaneously modulate up to 16 optical channels, rather than the conventional limit of eight optical channels. in The optical channels within the optical fiber may be separated.

[0031] 2A, the data streams may be provided to the MRM arrays 230(1)-230(4) as respective data sets DS1-DS4, such that each of the data sets DS1-DS4 includes multiple unique data streams. In some implementations, each of the data sets DS1-DS4 may include up to eight unique data streams, and thus the four MRM arrays 230(1)-230(4) may collectively modulate up to 32 unique data streams onto the optical signals 221-224 generated by the channel deinterleavers 220(1)-220(2). In such implementations, each of the MRM arrays 230(1)-230(4) may include eight microring modulators (not shown for simplicity), with each modulator configured to modulate one optical channel with data from a corresponding data stream.

[0032] The first MRM array 230(1) may receive the first separated optical stream 221 and the first data set DS1 including eight unique data streams. Each of the eight microring modulators provided in the first MRM array 230(1) may, for example, modulate one of the optical channels in the first separated optical stream 221 with data from a corresponding one of the eight data streams included in the first data set DS1 to generate the first modulated optical stream 231 including eight modulated optical channels. In some implementations, the first modulated optical stream 231 may inherit a channel spacing of about 260 GHz from the first separated optical stream 221.

[0033] The second MRM array 230(2) may receive the second separated optical stream 222 and the second data set DS2 including eight unique data streams. Each of the eight microring modulators provided in the second MRM array 230(2) may, for example, modulate one of the optical channels in the second separated optical stream 222 with data from a corresponding one of the eight data streams included in the second data set DS2 to generate the second modulated optical stream 232 including eight modulated optical channels. In some implementations, the second modulated optical stream 232 may inherit a channel spacing of about 260 GHz from the second separated optical stream 222.

[0034] The third MRM array 230(3) may receive the third separated optical stream 223 and a third data set DS3 including eight unique data streams. Each of the eight microring modulators provided in the third MRM array 230(3) may, for example, modulate one of the optical channels in the third separated optical stream 223 with data from a corresponding one of the eight data streams included in the third data set DS3 to generate the third modulated optical stream 233 including eight modulated optical channels. In some implementations, the third modulated optical stream 233 may inherit a channel spacing of about 260 GHz from the third separated optical stream 223.

[0035] The fourth MRM array 230(4) may receive the fourth separated optical stream 224 and the fourth data set DS4 including eight unique data streams. Each of the eight microring modulators provided in the fourth MRM array 230(4) may, for example, modulate one of the optical channels in the fourth separated optical stream 224 with data from a corresponding one of the eight data streams included in the fourth data set DS4 to generate the fourth modulated optical stream 234 including eight modulated optical channels. In some implementations, the fourth modulated optical stream 234 may inherit a channel spacing of about 260 GHz from the fourth separated optical stream 224.

[0036] In some implementations, each of the first separated optical stream 221, the second separated optical stream 222, the third separated optical stream 223, and the fourth separated optical stream 224 may be a wavelength division and multiplexed (WDM) optical stream, as described in more detail below. Furthermore, in some implementations, the modulated optical channels in the first modulated optical stream 231 and the second modulated optical stream 232 may be offset from one another based on the wavelength of each optical channel, for example, as determined by the operation of the first channel deinterleaver 210 and the second channel deinterleaver 220(1). Similarly, the modulated optical channels in the third modulated optical stream 233 and the fourth modulated optical stream 234 may be offset from one another based on the wavelength of each optical channel, for example, as determined by the operation of the first channel deinterleaver 210 and the third channel deinterleaver 220(2).

[0037] The first optical interleaver 240(1) receives an optical input source OS modulated by each of the 16 data streams associated with the first and second data sets DS1-DS2. in A first optical output stream OS may include 16 odd optical channels. out1In some implementations, a channel offset between the first modulated optical stream 231 and the second modulated optical stream 232 may allow, for example, the first optical output stream OS to be combined with minimal crosstalk between the modulated channels. out1 As a result, the first optical output stream OS out1 The channel spacing between the optical channels of the first optical output stream OS out1 is sometimes called a dense wavelength division multiplexing (DWDM) optical stream.

[0038] Similarly, the second optical interleaver 240(2) receives an optical input source OS modulated by each of the 16 data streams associated with the third and fourth data sets DS3-DS4. in A second optical output stream OS out2 In some implementations, a channel offset between the third modulated optical stream 233 and the fourth modulated optical stream 234 may be used to, for example, combine the second optical output stream OS with minimal crosstalk (if any) between the modulated channels. out2 As a result, the second optical output stream OS out2 The channel spacing between the optical channels of the second optical output stream OS out2 is sometimes called a DWDM optical stream.

[0039] 2B is a functional diagram 250 illustrating an example operation of the optical modulation circuit 200 of FIG. 2A according to some implementations. in is split by a channel deinterleaver 210 to generate optical signals 211 and 212. The first optical signal 211 is input from an optical input source OS in 16 odd channels, with a channel spacing of 130 GHz, and the second optical signal 212 is from an optical input source OS in 1, and has a channel spacing of 130 GHz. The first optical signal 211 is split by a channel deinterleaver 220(1) to generate optical signals 221 and 222, and the second optical signal 212 is split by a channel deinterleaver 220(2) to generate optical signals 223 and 224. Each of the optical signals 221-224 may be, for example, in It contains eight channels separated by a channel spacing of 260 GHz so as to contain one-quarter of the optical channels.

[0040] Each of the eight channels of optical signal 221 is modulated with a unique data stream by a first MRM array 230(1) to generate a first modulated optical signal 231, each of the eight channels of optical signal 222 is modulated with a unique data stream by a second MRM array 230(2) to generate a second modulated optical signal 232, each of the eight channels of optical signal 223 is modulated with a unique data stream by a third MRM array 230(3) to generate a third modulated optical signal 233, and each of the eight channels of optical signal 224 is modulated with a unique data stream by a fourth MRM array 230(4) to generate a fourth modulated optical signal 234. Modulated optical signals 231 and 232, each of which includes eight modulated optical channels separated by a channel spacing of 260 GHz, are referred to as a first optical output stream OSC. out1Similarly, modulated optical signals 233 and 234, each containing eight modulated optical channels separated by a channel spacing of 260 GHz, are combined in a first optical interleaver 240(1) to generate a second optical output stream OSC out2 The first and second optical output streams OSC are combined in a second optical interleaver 240(2) to generate out1 and OSC out2 Each of the first and second optical output streams OSC each contains 16 channels of modulated data with adjacent channels separated by a channel spacing of 130 GHz. Thus, the first and second optical output streams OSC out1 and OSC out2 The channel spacing of the optical input source OS in This is twice the channel spacing.

[0041] 3 is a simplified block diagram of a microring modulator 300, according to some implementations. The microring modulator 300, which may be one example of a microring modulator provided within each of the MRM arrays 230(1)-230(4) of FIG. 2A, may be coupled to a waveguide 310 that receives an optical input source 302 having one or more optical wavelengths. In some implementations, the microring modulator 300 may be configured to modulate a particular wavelength of light corresponding to one optical channel. For example, the optical input source 302 may include an optical channel having a wavelength λ, and the microring modulator 300 may be configured to modulate the λ-based optical channel with data 304 to generate a modulated optical output signal 306 that may be propagated through the waveguide 310.

[0042] The microring modulator 300 may be characterized by an FSR that specifies a range of operating wavelengths, and an array of microring modulators 300 may be configured to modulate various wavelengths within the FSR. In some implementations, the microring modulator 300 may be configured to modulate a wavelength λ based on a nominal diameter of the microring modulator 300. A heating element (not shown for simplicity) may be used to selectively tune the microring modulator 300 for the wavelength λ.

[0043] In some implementations, the microring modulator 300 may be silicon-based and may be designed to operate at wavelengths around 1310 nm, which corresponds to 229 THz, may have a radius of about 5 microns, and may have an FSR of about 13.5 nm. The microring modulator may be designed to operate at greater than 50 GBd. As a result, the operating characteristics of the microring modulator 300 may be suitable for the channel spacing of the optical streams 221-224 generated by the channel deinterleaver pair 220(1)-220(2). In other implementations, the microring modulator 300 may have other suitable operating characteristics. For example, in at least one other implementation, the microring modulator 300 may operate at wavelengths other than 1310 nm.

[0044] FIG. 4 is an example graph 400 illustrating example characteristics of a microring modulator 300 according to some implementations. Graph 400 illustrates optical power (transmittance) as a function of wavelength (normalized to 1 when the wavelength deviates significantly from resonance) for a number of transmission curves 402 associated with the microring modulator 300 of FIG. 3. When the wavelength is at resonance of the microring, the transmission is close to 0. The transmission curves 402 illustrate the manner in which light may be modulated by the microring modulator 300. For example, a wavelength corresponding to an optical channel modulated by the microring modulator 300 is shown by line 404. The transmittance may be tuned (e.g., modulated) over a range 410 for the wavelength of the optical channel represented by line 404, for example, by varying the voltage across a PN junction embedded in the waveguide of the ring.

[0045] Wavelengths associated with adjacent optical channels are also shown in graph 400. For example, line 406 may indicate a first wavelength that may be associated with an adjacent optical channel having a smaller wavelength, and line 408 may indicate a second wavelength that may be associated with an adjacent optical channel having a larger wavelength. In some implementations, the spacing between adjacent optical channels may be based at least in part on crosstalk detected on the adjacent channels. Additionally or alternatively, the spacing between adjacent optical channels may be based at least in part on transmission losses caused by other micro-ring modulators.

[0046] 5 is a chart 500 of example channel assignments for the optical modulation circuit 200 of FIG. 2A, according to some implementations. The example chart 500 is based on each of the MRM arrays 230(1)-230(4) of the optical modulation circuit 200 including multiple microring modulators 300 each having an FSR of 13.5 nm, and therefore the channel assignments shown in the chart 500 can fit within the FSR of 13.5 nm. It should be understood that other channel assignments are possible for other FSRs.

[0047] The first channel assignment 510 includes eight channels 511-518, each having a channel separation (e.g., channel spacing) of about 1.5 nm with wavelengths around 1310 nm. The channels 511-518 may be offset with respect to any arbitrary wavelength, and adjacent channels may be offset by 1.5 nm. In some embodiments, the 1.5 nm channel spacing may correspond to the 260 GHz channel spacing at 1310 nm described above with respect to the optical streams 221-224 and modulated optical streams 231-234 of FIG. 2A. For the example of FIG. 5, the first channel 511 has a channel offset of 0 nm, the second channel 512 has a channel offset of 1.5 nm, the third channel 513 has a channel offset of 3.0 nm, and so on, with the eighth channel 518 having a channel offset of 10.5 nm. The first channel assignment 510 also includes optical channel number assignments corresponding to the optical channel numbers described above with respect to FIG. 2A. For example, the first channel 511 may correspond to optical channel 1, the second channel 512 may correspond to optical channel 5, the third channel 513 may correspond to optical channel 9, and so on, with the eighth channel 518 corresponding to optical channel 29. In some implementations, the first channel assignment 510 may correspond to the first split optical stream 221 of FIG. 2A and the first MRM array 230(1) may be configured to modulate the optical channels shown in the first channel assignment 510.

[0048] The second channel assignment 520 includes eight channels 521-528, each having a channel width (e.g., channel spacing) of about 1.5 nm. Adjacent channels may be offset by 1.5 nm, which may correspond to the 260 GHz channel spacing described above with respect to FIG. 2A. For the example of FIG. 5, the first channel 521 has a channel offset of 0.375 nm, the second channel 522 has a channel offset of 1.875 nm, the third channel 523 has a channel offset of 3.375 nm, and so on until the eighth channel 528 has a channel offset of 10.875 nm. The second channel assignment 520 also includes optical channel number assignments corresponding to the optical channel numbers described above with respect to FIG. 2A. For example, the first channel 521 may correspond to optical channel 2, the second channel 522 may correspond to optical channel 6, the third channel 523 may correspond to optical channel 10, and so on, with the eighth channel 528 corresponding to optical channel 30. In some implementations, the second channel assignment 520 may correspond to the second split optical stream 222 of FIG. 2A and the second MRM array 230(2) may be configured to modulate the optical channels shown in the second channel assignment 520.

[0049] The third channel assignment 530 includes eight channels 531-538, each having a channel width (e.g., channel spacing) of about 1.5 nm. Adjacent channels may be offset by 1.5 nm, which may correspond to the 260 GHz channel spacing described above with respect to FIG. 2A. For the example of FIG. 5, the first channel 531 has a channel offset of 0.75 nm, the second channel 532 has a channel offset of 2.25 nm, the third channel 533 has a channel offset of 3.75 nm, and so on, with the eighth channel 534 having a channel offset of 11.25 nm. The third channel assignment 530 also includes optical channel number assignments that correspond to the optical channel numbers described above with respect to FIG. 2A. For example, the first channel 531 may correspond to optical channel 3, the second channel 532 may correspond to optical channel 7, the third channel 533 may correspond to optical channel 11, and so on, with the eighth channel 538 corresponding to optical channel 31. In some implementations, the third channel assignment 530 may correspond to the third split optical stream 223 of FIG. 2A, and the third MRM array 230(3) may be configured to modulate the optical channels shown in the third channel assignment 530.

[0050] The fourth channel assignment 540 includes eight channels 541-548, each having a channel width (e.g., channel spacing) of about 1.5 nm. Adjacent channels may be offset by 1.5 nm, which may correspond to the 260 GHz channel spacing described above with respect to FIG. 2A. For the example of FIG. 5, the first channel 541 has a channel offset of 1.125 nm, the second channel 542 has a channel offset of 2.625 nm, the third channel 543 has a channel offset of 4.125 nm, and so on until the eighth channel 548 has a channel offset of 11.625 nm. The fourth channel assignment 540 also includes optical channel number assignments corresponding to the optical channel numbers described above with respect to FIG. 2A. For example, the first channel 541 may correspond to optical channel 4, the second channel 542 may correspond to optical channel 8, the third channel 543 may correspond to optical channel 12, and so on, with the eighth channel 548 corresponding to optical channel 32. In some implementations, the fourth channel assignment 540 may correspond to the fourth split optical stream 224 of FIG. 2A and the fourth MRM array 230(4) may be configured to modulate the optical channels shown in the fourth channel assignment 540.

[0051] Those skilled in the art will recognize that the channel widths and channel offsets described with respect to channel assignments 510, 520, 530, and 540 are exemplary and not limiting. Other channel widths and offsets are possible. For example, other channel widths are feasible, provided that the crosstalk and insertion loss associated with those channel widths have little or no effect on adjacent channels. Furthermore, other channel widths and offsets are feasible, provided that the channel assignment for the eight adjacent channels is maintained along with the FSR of the associated microring modulator.

[0052] FIG. 6 is a block diagram of an example MRM array 600, according to some implementations. The MRM array 600 may be an example of one or more of the MRM arrays 230(1)-230(4) of FIG. 2A. The MRM array 600 may include eight microring modulators 601-608 and a waveguide 620. Each of the microring modulators 601-608 may include an input for receiving each of the eight data streams 611-618 and may include an output coupled to the waveguide 620. For example, the first microring modulator 601 may receive the first data stream 611, the second microring modulator 602 may receive the second data stream 612, and so on, with the eighth microring modulator 608 receiving the eighth data stream 618. For purposes of description herein, each of the microring modulators 601-608 may be silicon based, may have an FSR of about 13.5 nm, and may have a radius of about 5 microns.

[0053] In some implementations, the MRM array 600 may be configured to modulate the optical channels according to one of the channel assignments shown in FIG. 5. In some aspects, the MRM array 600 may be configured to modulate the optical channels of the first split optical stream 221 by configuring the microring modulators 601-608 to modulate the optical channels according to the first channel assignment 510. For example, the first microring modulator 601 may be configured to modulate optical channel 1, the second microring modulator 602 may be configured to modulate optical channel 5, and so on, the eighth microring modulator 608 may be configured to modulate optical channel 29.

[0054] In other aspects, the MRM array 600 may be configured to modulate the optical channels of the second split optical stream 222 by configuring the microring modulators 601-608 to modulate the optical channels in accordance with the second channel assignment 520. For example, the first microring modulator 601 may be configured to modulate optical channel 2, the second microring modulator 602 may be configured to modulate optical channel 6, and so on, with the eighth microring modulator 608 configured to modulate optical channel 30.

[0055] In other aspects, the MRM array 600 may be configured to modulate the optical channels of the third split optical stream 223 by configuring the microring modulators 601-608 to modulate the optical channels in accordance with the third channel assignment 530. For example, the first microring modulator 601 may be configured to modulate optical channel 3, the second microring modulator 602 may be configured to modulate optical channel 7, and so on, with the eighth microring modulator 608 configured to modulate optical channel 31.

[0056] In other aspects, the MRM array 600 may be configured to modulate the optical channels of the fourth split optical stream 224 by configuring the microring modulators 601-608 to modulate the optical channels in accordance with the fourth channel assignment 540. For example, the first microring modulator 601 may be configured to modulate optical channel 4, the second microring modulator 602 may be configured to modulate optical channel 8, and so on, with the eighth microring modulator 608 configured to modulate optical channel 32.

[0057] 7 shows an example flowchart illustrating example operations 700 for generating a light output, according to some implementations. Although described herein as being performed by the light modulation circuit 200 of FIG. 2A, the operations 700 may be performed by any technically feasible processor, device, hardware platform, etc.

[0058] The optical modulation circuit 200 may split 701 an optical input source into a first optical stream and a second optical stream. In some implementations, the optical input source OS in may be separated into a first optical stream 211 and a second optical stream 212 using a channel deinterleaver 210. In some aspects, the first optical stream 211 is received from an optical input source OS in , and the second optical stream 212 may include odd numbered optical channels from the optical input source OS in The optical channel may include even numbered optical channels.

[0059] The optical modulation circuit 200 may separate the first optical stream into a first separated optical stream and a second separated optical stream (702). In some implementations, the first optical stream 211 may be separated into a first separated optical stream 221 and a second separated optical stream 222 using a channel deinterleaver 220(1). In some aspects, the first separated optical stream 221 may include a first set of alternating optical channels of the first optical stream 211, and the second separated optical stream 222 may include a second set of alternating optical channels of the first optical stream 211, where the second set of alternating optical channels is different from the first set of alternating channels.

[0060] The optical modulation circuit 200 may modulate a first set of data streams onto the optical channels of the first separated optical stream to generate a first modulated optical stream (703), and may modulate a second set of data streams onto the optical channels of the second separated optical stream to generate a second modulated optical stream (704). In some implementations, the first MRM array 230(1) may modulate a data stream associated with a first data set DS1 onto the optical channels of the first separated optical stream 221 to generate a first modulated optical stream 231, and the second MRM array 230(2) may modulate a data stream associated with a second data set DS2 onto the optical channels of the second separated optical stream 222 to generate a second modulated optical stream 232.

[0061] The optical modulation circuit 200 may generate a first optical output stream based on a combination of the first modulated optical stream and the second modulated optical stream (705). In some implementations, the first channel interleaver 240(1) may interleave the first optical output stream OS out1 The first modulated optical stream 231 and the second modulated optical stream 232 may be combined to generate

[0062] The optical modulation circuit 200 may split the second optical stream into a third separated optical stream and a fourth separated optical stream (706). In some implementations, the second optical stream 212 may be split into a third separated optical stream 223 and a fourth separated optical stream 224 using a channel deinterleaver 220(2). In some aspects, the third separated optical stream 223 may include a first set of alternating optical channels of the second optical stream 212, and the fourth separated optical stream 224 may include a second set of alternating optical channels of the second optical stream 212, where the second set of alternating optical channels is different from the first set of alternating channels.

[0063] The optical modulation circuit 200 may modulate the third set of data streams onto the optical channels of the third separated optical stream to generate a third modulated optical stream (707), and may modulate the fourth set of data streams onto the optical channels of the fourth separated optical stream to generate a fourth modulated optical stream (708). In some implementations, the third MRM array 230(3) may modulate the data streams associated with the third data set DS3 onto the optical channels of the third separated optical stream 223 to generate the third modulated optical stream 233, and the fourth MRM array 230(4) may modulate the data streams associated with the fourth data set DS4 onto the optical channels of the fourth separated optical stream 224 to generate the fourth modulated optical stream 234.

[0064] The optical modulation circuit 200 may generate a second optical output stream based on a combination of the third modulated optical stream and the fourth modulated optical stream (709). In some implementations, the second optical combiner 240(2) may generate a second optical output stream OS out2 The third modulated optical stream 233 and the fourth modulated optical stream 234 may be combined to generate

[0065] Those skilled in the art will appreciate that information and signals may be represented using any of a variety of different technologies and techniques. For example, the data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0066] Moreover, those skilled in the art will appreciate that the various exemplary logic blocks, modules, circuits, and algorithm steps described in connection with the aspects disclosed herein may be implemented as electronic hardware, computer software, or a combination of both. To clearly illustrate this interchangeability of hardware and software, various exemplary components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the particular application and design constraints imposed on the overall system. Those skilled in the art may implement the described functionality in different ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

[0067] The methods, sequences, or algorithms described in connection with the aspects disclosed herein may be implemented directly in hardware, in software modules executed by a processor, or in a combination of the two. The software modules may reside in RAM latches, flash latches, ROM latches, EPROM latches, EEPROM latches, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. Alternatively, the storage medium may be integral to the processor.

[0068] In the above specification, the exemplary implementations have been described with reference to certain exemplary implementations thereof. However, it will be apparent that various modifications and changes may be made to those implementations without departing from the broader scope of the disclosure as set forth in the appended claims. The specification and drawings are therefore to be regarded in an illustrative rather than a restrictive sense.

Claims

1. an input terminal for receiving an optical input source including a plurality of optical channels or optical wavelengths and having a first channel spacing; a first channel deinterleaver configured to separate the optical input source into a first optical stream and a second optical stream, the first optical stream and the second optical stream having a second channel spacing greater than the first channel spacing; a second channel deinterleaver configured to separate the first optical stream into a first separated optical stream and a second separated optical stream, the first separated optical stream and the second separated optical stream having a third channel spacing greater than the second channel spacing; a first microring modulation (MRM) array configured to modulate a first set of data streams onto optical channels of the first separated optical stream to generate a first modulated optical stream; a second MRM array configured to modulate a second set of data streams onto optical channels of the second separated optical stream to generate a second modulated optical stream; a first optical interleaver configured to generate a first optical output stream based on the first and second modulated optical streams; An optical modulation circuit comprising:

2. 2. The optical modulation circuit of claim 1, wherein the first optical stream comprises odd-numbered optical channels of the optical input source and the second optical stream comprises even-numbered optical channels of the optical input source.

3. 2. The optical modulation circuit of claim 1, wherein the first separated optical stream comprises a first set of alternating optical channels of the first optical stream and the second separated optical stream comprises a second set of alternating optical channels of the first optical stream, the first set of alternating optical channels being different from the second set of alternating optical channels.

4. the first MRM array comprises a first plurality of microring modulators each configured to modulate an associated data stream of the first set of data streams onto a corresponding optical channel of the first separated optical stream; the second MRM array comprising a second plurality of microring modulators each configured to modulate an associated data stream of the second set of data streams onto a corresponding optical channel of the second separated optical stream.

2. The optical modulation circuit according to claim 1.

5. 5. The optical modulation circuit of claim 4, wherein each of said first and second pluralities of micro-ring modulators has a free spectral range of at least 13.5 nm and a radius of approximately 5 microns.

6. the first channel spacing is approximately 65 GHz and the second channel spacing of each of the first and second optical streams is twice the channel spacing of the optical input source, i.e., approximately 130 GHz; a fourth channel spacing of each of the first and second modulated optical streams is four times the channel spacing of the optical input source, i.e., approximately 260 GHz; a fifth channel spacing of the first optical output stream is twice the channel spacing of the optical input source, i.e., approximately 130 GHz; 2. The optical modulation circuit according to claim 1.

7. a third channel deinterleaver configured to separate the second optical stream into a third separated optical stream and a fourth separated optical stream; a third MRM array configured to modulate a third set of data streams onto optical channels of the third separated optical stream to generate a third modulated optical stream; a fourth MRM array configured to modulate a fourth set of data streams onto the optical channels of the fourth separated optical stream to generate a fourth modulated optical stream; a second optical interleaver configured to generate a second optical output stream based on the third and fourth modulated optical streams; and The optical modulation circuit of claim 1 further comprising:

8. an input terminal for receiving an optical input source including a plurality of optical channels or optical wavelengths and having a first channel spacing; a number of optical modulation circuits coupled to said input terminal; a number of photodetector circuits configured to receive the modulated optical signal and to output a data stream; 13. A photonics integrated circuit comprising: a first channel deinterleaver configured to separate the optical input source into a first optical stream and a second optical stream, the first optical stream and the second optical stream having a second channel spacing greater than the first channel spacing; a second channel deinterleaver configured to separate the first optical stream into a first separated optical stream and a second separated optical stream, the first separated optical stream and the second separated optical stream having a third channel spacing greater than the second channel spacing; a third channel deinterleaver configured to separate the second optical stream into a third separated optical stream and a fourth separated optical stream, the third separated optical stream and the fourth separated optical stream having a fourth channel spacing that is greater than the second channel spacing; a plurality of microring modulation (MRM) arrays configured to modulate a unique set of data streams onto optical channels of a corresponding separated ones of the separated optical streams to generate each of a first modulated optical stream, a second modulated optical stream, a third modulated optical stream, and a fourth modulated optical stream, respectively; a first optical interleaver configured to generate a first optical output stream based on the first and second modulated optical streams; a second optical interleaver configured to generate a second optical output stream based on the third and fourth modulated optical streams; and A photonics integrated circuit comprising:

9. 9. The photonics integrated circuit of claim 8, wherein said first optical stream comprises odd-numbered optical channels of said optical input source and said second optical stream comprises even-numbered optical channels of said optical input source.

10. the first separated optical stream includes a first set of alternating optical channels of the first optical stream; the second separated optical stream includes a second set of alternating optical channels of the first optical stream; the third separated optical stream includes a first set of alternating optical channels of the second optical stream; 10. The photonics integrated circuit of claim 8, wherein the fourth separated optical stream comprises a second set of alternating optical channels of the second optical stream.

11. 10. The photonics integrated circuit of claim 8, wherein each of the plurality of MRM arrays comprises a number of microring modulators configured to modulate an associated one of the unique data streams onto a corresponding one of the separated optical streams.

12. The first channel spacing is about 65 GHz; the second channel spacing of each of the first and second optical streams is about 130 GHz; each of the modulated optical streams has a fifth channel spacing of about 260 GHz; The photonics integrated circuit of claim 8 , wherein each of said optical output streams has a sixth channel spacing of about 130 GHz.

13. 13. The photonics integrated circuit of claim 12, wherein said optical input source includes 32 optical channels, each of said first and second optical streams includes 16 optical channels, each of said modulated optical streams includes 8 optical channels, and each of said optical output streams includes 16 optical channels.

14. splitting an optical input source into a first optical stream and a second optical stream; splitting the first optical stream into a first separated optical stream and a second separated optical stream; modulating a first set of data streams onto optical channels of the first separated optical stream to generate a first modulated optical stream; modulating a second set of data streams onto optical channels of the second separated optical stream to generate a second modulated optical stream; generating a first optical output stream based on a combination of the first modulated optical stream and the second modulated optical stream; Including, the optical input source has a first channel spacing, and the first optical stream and the second optical stream have a second channel spacing that is greater than the first channel spacing; the first separated optical stream and the second separated optical stream have a third channel spacing greater than the second channel spacing. method.

15. splitting the second optical stream into a third separated optical stream and a fourth separated optical stream; modulating a third set of data streams onto optical channels of the third separated optical stream to generate a third modulated optical stream; modulating a fourth set of data streams onto the optical channels of the fourth separated optical stream to generate a fourth modulated optical stream; generating a second optical output stream based on a combination of the third modulated optical stream and the fourth modulated optical stream; The method of claim 14 further comprising:

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