Scalable multiband WDM optical computing interconnect architecture

Abstract

A scalable multiband wavelength division multiplexing (WDM) transceiver architecture suitable for high bandwidth optical computing interconnect (OCI) between computing resources. The WDM wavelength range is divided into two or more color / wavelength bands. Each band of the WDM optical signal may be coupled by separate semiconductor optical amplifiers (SOAs) that are tuned to different bands. The wavebands may be transmitted over an optical MUX / DeMUX for transmission over an optical fiber. The optical MUX / DeMUX may include a band MUX / DeMUX or a polarization MUX / DeMUX.

Description

Background Technology

[0001] Many computing applications, such as machine learning (ML), can be enhanced by higher bandwidth communication between computing resources, as sharing computing memory resources across computing nodes becomes increasingly necessary. Sharing computing tasks across processor (CPU, XPU, and GPU) clusters optimizes overall computing power. Traditionally, data connections between computing units in a cluster are electrical, typically varying in length from a few millimeters to <250 meters. However, optical data connection architectures known as Optical Compute Interconnect (OCI) are emerging as a viable means of implementing Tbps aggregated links between computing and / or memory nodes.

[0002] In OCI, dense wavelength division multiplexing (DWDM) provides a viable solution for scaling up and down computational resources, and further decomposing such resources. OCI may require a significant increase in the number of wavelengths (N) in DWDM, as well as an increase in the desired number of input / output fibers (M), and also an increase in the optical modulation baud rate (R) to achieve a total capacity (N*M*R) far greater than the current 2Tbps (8λ*8 fiber*32GBaud NRZ) link. For example, a 16Tbps OCI might require a first doubling of the wavelengths: (16λ*8 fiber*128Gbps PAM4). A 32Tbps OCI might require another doubling of the wavelengths: (32λ*8 fiber*128Gbps PAM4).

[0003] Therefore, new OCI architectures capable of achieving such wavelength extensions, and the associated photonic integrated circuit (PIC) implementations of these architectures, are commercially viable. Attached Figure Description

[0004] In the accompanying drawings, the materials described herein are illustrated by way of example rather than limitation. For the sake of simplicity and clarity, the elements illustrated in the drawings are not necessarily drawn to scale. For example, the dimensions of some elements may be enlarged relative to others for clarity. Furthermore, reference numerals have been repeated between the figures where deemed appropriate to indicate corresponding or similar elements. In the figures:

[0005] Figure 1This is a schematic diagram of a scalable dual-band OCI transmitter architecture according to some embodiments;

[0006] Figure 2A and Figure 2B This is a schematic diagram of a scalable dual-band OCI receiver architecture according to some embodiments;

[0007] Figure 3 It is a scalable multiband OCI transceiver architecture that includes polarization MUX and DeMUX, based on some dual-band embodiments;

[0008] Figure 4 This is a PIC implementation of a dual-band OCI transceiver architecture for 16 channels, according to some embodiments;

[0009] Figure 5 This is a schematic diagram of a scalable multiband OCI transmitter architecture based on some four-band embodiments;

[0010] Figure 6A , Figure 6B and Figure 6C This is a schematic diagram of a 4×1 MUX according to some embodiments;

[0011] Figure 7A and Figure 7B This is a schematic diagram of a multi-band OCI receiver architecture according to some embodiments;

[0012] Figure 8 This is a schematic diagram of a 1×4 DeMUX according to some embodiments;

[0013] Figure 9 This is a PIC implementation of a four-band OCI transceiver architecture for 32 channels, according to some embodiments;

[0014] Figure 10A This is a schematic diagram of a computing cluster including a multi-band OCI transceiver PIC, according to some embodiments;

[0015] Figure 10B This is a schematic diagram of a computing cluster including a multi-band OCI transceiver PIC, based on some alternative embodiments; and

[0016] Figure 11 This is a functional block diagram of an electronic computing device according to some embodiments, which may include one or more scalable multi-band OCI transceivers. Detailed Implementation

[0017] Various embodiments are described with reference to the accompanying drawings. Although specific configurations and arrangements are depicted and discussed in detail, this is for illustrative purposes only. Those skilled in the art will recognize that other configurations and arrangements are possible without departing from the spirit and scope of this description. It will be apparent to those skilled in the art that the techniques and / or arrangements described herein can also be used in a variety of other systems and applications besides those detailed herein.

[0018] The following detailed description is referenced to the accompanying drawings, which form part of this document and illustrate exemplary embodiments. Furthermore, it should be understood that other embodiments may be utilized, and structural and / or logical changes may be made without departing from the scope of the claimed subject matter. It should also be noted that orientations and references (e.g., up, down, top, bottom, etc.) may be used only to facilitate the description of the features in the drawings. Therefore, the following detailed description should not be construed as limiting, and the scope of the claimed subject matter is defined only by the appended claims and their equivalents.

[0019] Numerous details are set forth in the following description. However, it will be apparent to those skilled in the art that the various embodiments can be practiced without these specific details. In some instances, well-known methods and apparatuses are shown in block diagram form rather than in detail to avoid obscuring the embodiments. Throughout this specification, references to "embodiment," "one embodiment," or "some embodiments" mean that a particular feature, structure, function, or characteristic described in connection with that embodiment is included in at least one embodiment. Thus, the phrases "in an embodiment," "in one embodiment," or "in some embodiments" appearing in multiple places throughout this specification do not necessarily refer to the same embodiment. Furthermore, in one or more embodiments, particular features, structures, functions, or characteristics can be combined in any suitable manner. For example, the first embodiment can be combined with the second embodiment where there is no mutual exclusion between a particular feature, structure, function, or characteristic associated with the first embodiment and a particular feature, structure, function, or characteristic associated with the second embodiment.

[0020] As used in the specification and appended claims, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and covers any and all possible combinations of one or more of the associated listed items.

[0021] The terms “coupled” and “connected” and their derivatives are used herein to describe functional or structural relationships between components. These terms are not intended to be synonyms for each other. Rather, in certain embodiments, “connected” may be used to indicate that two or more elements are in direct physical, optical, or electrical contact with each other. “Coupled” may be used to indicate that two or more elements are in direct or indirect physical or electrical contact with each other (with other intervening elements between them), and / or that two or more elements cooperate or interact with each other (e.g., in a causal relationship).

[0022] As used herein, the terms "above," "below," "between," and "on" refer to the relative position of a component or material with respect to other components or materials, where such physical relationships are noteworthy. For example, in the context of materials, one material or layer above or below another material may be in direct contact, or may have one or more intervening materials or layers. Furthermore, one material between two materials or layers may be in direct contact with both materials / layers, or may have one or more intervening materials / layers. In contrast, a first material or layer "on" a second material or layer is in direct contact with that second material / layer. Similar distinctions are made in the context of component assemblies.

[0023] As used throughout this specification and in the claims, a list of items connected by the terms “at least one of…” or “one or more of…” may mean any combination of the listed items. For example, the phrase “at least one of A, B or C” may mean A; B; C; A and B; A and C; B and C; or A, B and C.

[0024] As further described below, the multi-band WDM transceiver architecture enables a highly scalable and low-cost OCI architecture that can be implemented using silicon photonics (SiPh) integrated circuits. In general, the multi-band architecture described in this paper divides the range of channel wavelengths propagating within the transceiver across multiple color / wavelength (e.g., red / blue) bands. Each color band includes a portion of the channel wavelength, thereby enabling a unified transmission link and transmit-receive (TRx) PIC design that utilizes more than eight channel wavelengths without relying on a wide-gain bandwidth semiconductor optical amplifier (SOA), which remains elusive and presents significant technical challenges (e.g., quantum well design).

[0025] By mitigating the bandwidth limitations of the SOA, the multiband architecture described herein allows for an expansion of the number of channel wavelengths without incurring the larger cross-gain modulation and four-wave mixing nonlinear losses associated with passing DWDM signals with more wavelengths through the in-line SOA. Since the nonlinear optical phenomena of the SOA (e.g., four-wave mixing) affect the optical signal-to-noise ratio (OSNR) of the optical circuitry, the multiband architecture described herein also improves the system bit error rate (BER) and device performance (such as gain uniformity and power output uniformity). Therefore, the multiband architecture described herein allows OCI to better accommodate the higher BER requirements imposed by emerging PAM4 modulation formats (e.g., those incorporated into Peripheral Component Interconnect Express (PCIe7) and Universal Chipplet Interconnect Express (UCIe) specifications).

[0026] Figure 1 This is a schematic diagram of an n-wavelength scalable dual-band OCI transmitter architecture 100, including a first block 101 and a second block 102 of a wavelength division multiplexing (WDM) photonic circuitry system. Each block 101, 102 includes m optical waveguides 113, each used to propagate a WDM optical signal across one band of the channel wavelength. The number of wavelengths n can vary depending on the implementation (e.g., 8, 12, 16, or 32, etc.). In the illustrated example, the number of wavelengths n is equally divided between blocks 101 and 102. The photonic circuitry system used for block 101 is used to multiplex and demultiplex signals emitted (launched) from the optical transmitter array 110. The first transmitter array 110 includes transmitters 1111–111 n / 2 Its relationship with the center wavelength or line λ1-λ n / 2 Optical signals are output on n / 2 consecutive or periodic wavelength channels associated with each other. The photonic circuitry system for block 102 is similarly used for outputting signals from the transmitter 111. n / 2+1 –111 n The signals emitted by another optical transmitter array 110 are multiplexed and split. These transmitters are used to multiplex and split the signals emitted by the center wavelength λ. n / 2+1 –λ n Optical signals are output on n / 2 consecutive wavelength channels with center wavelengths λ. n / 2+1 –λ n All are compared to the channel wavelength λ1-λ n / 2Long wavelength. Therefore, block 101 can be called the blue block, and block 102 can be called the red block.

[0027] Channel wavelength λ1-λ n It can span any part of the spectrum, such as 1270 nm–1590 nm. In some exemplary embodiments, the channel wavelength λ1-λ n At least a portion of the O-band (i.e., 1360 nm–1270 nm), the L-band (i.e., 1577 nm–1565 nm), and / or the C-band (1564 nm–1530 nm) spanning the electromagnetic spectrum. λ1–λ n The channel spacing can vary depending on the implementation. However, for some DWDM embodiments, the channel spacing is less than 1.6 nm for the channel wavelength of at least one band (i.e., <200 GHz at 1550 nm). The longest band channel (λ) n / 2 ) and the shortest band channel (λ) n / 2+1 The inter-band spacing between wavelengths can be approximately the same as the intra-band channel spacing between wavelengths associated with the same band. However, the inter-band spacing can also differ significantly from the intra-band channel spacing (e.g., greater than 50%), leaving the desired guard band in λ. n / 2 With λ n / 2+1 between.

[0028] Output signals from one or more optical transmitter arrays 110 are coupled to one of optical multiplexers / splitters 1121, 1122, which output WDM optical signals spanning a first or second wavelength band to each of m optical waveguides 113. Multiplexers / splitters 1121, 1122 can each have any device architecture, as the embodiments herein are not limited in this respect. The architecture of multiplexer / splitter 1121 can also be substantially the same as that of multiplexer / splitter 1122. In some embodiments where n / 2 equals m, multiplexers / splitters 1121, 1122 have a square (e.g., 8×8) MUX / splitter device architecture, which may include multi-mode interference (MMI) couplers / power splitters.

[0029] For block 101, multiple optical transmission modulators 114 are coupled to each optical waveguide 113 to modulate a WDM optical signal across a first band of channel wavelengths using transmission data 115. In the illustrated embodiment, each optical modulator 114 is a (micro)ring resonator modulator (MRM) tuned to a channel wavelength within a band of the channel wavelength. For block 101, each modulator 114 is tuned to modulate wavelengths λ1-λ2. n / 2 The transmission power of one wavelength. For block 102, modulators 114 are each tuned to modulate wavelength λ. n / 2+1 –λ n The transmission power is for one wavelength. In an exemplary embodiment, relatively low optical power (e.g., less than 3-5 dBm) is input to each MRM to limit baseline drift caused by self-thermal nonlinearity. Note that the OCI receiver transmission link will further include a length of optical fiber, and the optical circuitry system for block 101 includes a post-modulator 114 SOA group 121 with power for wavelengths λ1–λ2. n / 2 Optimized gain bandwidth, while the optical circuitry system for block 102 includes SOA group 122, which has wavelength λ n / 2+1 –λ n Optimized gain bandwidth.

[0030] In an exemplary embodiment, SOA group 121 includes m SOA 120s. B,1 -120 B,m These m SOA 120 B,1 -120 B,m It has a center wavelength within the blue band. In some embodiments, all SOA 120 B,1 -120 B,m They have substantially the same first center wavelength and can have substantially the same first photoluminescence (PL) band, the same first 3dB gain bandwidth (e.g., about 12nm), noise figure, saturation optical power, etc. The first center SOA wavelength can fall within the wavelength λ1-λ n / 2 Any location within, and advantageously close to the center wavelength of the first band (e.g., λ). n / 4 All SOA 120 R,1 -120 R,m It can have a substantially identical second center wavelength, and can have a substantially identical second PL band, the same second 3dB gain bandwidth, noise figure, saturation optical power, etc. The second center SOA wavelength can fall within λ. n / 2+1 –λn Any location within, and advantageously close to the center wavelength of the second band (e.g., λ). 3n / 4 Although the 3dB gain bandwidth of SOA group 121 can overlap with that of SOA group 122, the 3dB gain bandwidth of SOA group 121 does not include wavelength λ. n / 2+1 –λ n One or more of them, while the 3dB gain bandwidth of SOA group 122 does not include wavelengths λ1-λ2. n / 2 One or more of them.

[0031] After amplification by a band-specific SOA, the wavelengths of the two bands are combined for transmission into one or more optical fibers. For example... Figure 1 As shown, each optical waveguide 113 of block 101 is coupled to the corresponding 2×1 optical multiplexer 1251-125. m The first input port, while the various optical waveguides 113 of block 102 are coupled to the 2×1 optical multiplexer 1251-125. m The second input port. Multiplexer 1251-125 m They can share the same device architecture. In some embodiments, the band multiplexer includes a 2×1 bandpass filter (BPF). The SiPh can implement the BPF using, for example, an ultraflat Bragg grating similar to a laser Bragg grating, a three-ring or two-ring assisted Mach-Zender interferometer (MZI), a Bragg grating assisted reverse coupler / MZI, or a coupled resonator optical waveguide. In other embodiments, each multiplexer 1251-125 m It is a 2×1 power combiner, such as a 2×1 MMI coupler. In other embodiments, each multiplexer is 1251-125. m It is a polarization multiplexer. For example, a polarization multiplexer can include a 2×1 polarization rotator and combiner (PRC), which can also be implemented by SiPh.

[0032] like Figure 1 As shown, the transmitter architecture 100 terminates in an output coupler array comprising multiple fiber couplers 130. In the illustrated example, n WDM signals are used to transmit from m corresponding fiber couplers 130 to m fibers 1351-1352. mIn an array, to achieve a transmission throughput of n*m*R. Each fiber coupler 130 can have any device architecture suitable for coupling from a waveguide to an optical fiber. In some examples, each fiber coupler 130 may include an edge coupler (EC), such as, for example, an inverted / conical edge coupler. Each fiber coupler may include a grating coupler (GC), for example, each fiber 135 may be any known fiber suitable for OCI applications. The optical fiber may include, for example, a single-mode (SM) fiber core. The fiber core may have any suitable composition, but in an exemplary embodiment, the fiber core is made of glass suitable for transmitting one or more bands. The glass may be SiO2, SiO2 doped with GeO2, germanium silicate, phosphorus pentoxide, phosphosilicate, Al2O3, aluminosilicate, etc., or any combination thereof. In an exemplary SM embodiment, the core diameter is less than 10 μm (e.g., about 9 μm). Together with the fiber core, each optical fiber may include one or more cladding layers axially surrounding the fiber core.

[0033] Figure 2A This is a schematic diagram of an OCI receiver architecture 201 according to some embodiments. Receiver architecture 201 is compatible with embodiments of transmitter architecture 100 that include band multiplexers or power combiners. Receiver architecture 201 includes a plurality of input fiber couplers 130. In the illustrated example, to input from m fibers 1351-135... m An array receives m WDM signals of arbitrary polarization into m corresponding fiber couplers 130, which are advantageously polarization-independent fiber couplers. Each fiber coupler 130 is used to simultaneously propagate both TE and TM modes into an optical waveguide 113. The optical waveguide 113 can be optimized for low propagation loss of both TE and TM modes, such as a wide waveguide width, or a waveguide core size optimized for quasi-polarization independence. Each optical waveguide 113 is coupled to an optical signal conditioner 250, such as a polarization splitter-rotator (PSR) and a polarization combiner (PC), to convert all optical input signals to TE polarization. For the PC, the two outputs of the PSR are coupled to the input of a tunable MZI, where a phase shifter is controlled by heater power to adjust the phase of the incoming light so that the desired single polarization can be obtained at one output waveguide of the MZI. Alternatively, the signal conditioner 250 may include an infinite polarization combiner. Optical waveguide 113 propagates the TE signal to the optical signal detector array 2701-270. nFor example, each detector 270 includes a self-powered photodetector (SPPD) coupled to the optical waveguide 113 via a wavelength-selective micro-ring add / drop filter.

[0034] Figure 2B This is a schematic diagram of a dual-band OCI receiver architecture 202, which offers superior scalability compared to receiver architecture 201. Receiver architecture 202 is compatible with embodiments of transmitter architecture 100, which includes band multiplexers or power combiners. As shown, optical waveguide 113 couples the signal input via fiber optic coupler 130 to optical signal conditioner 250, and further propagates the TE mode signal to 1×2 to m band demultiplexers 2601-260. m One of them. In some embodiments, band demultiplexers 2601-260 m Each has its own multiplexer 1251-125 m ( Figure 1 The same architecture is used to separate the red and blue bands multiplexed in transmitter architecture 100. Receiver architecture 202 ( Figure 2B This can further include band-specific SOA groups 221 and 222, which can be substantially as described above for SOA groups 121 and 122 ( Figure 1 As described in SOA group 221. Figure 2B ), 120 per SOA B,1 -120 B,n / 2 Used for propagation to detectors 2701-270 n / 2 Previously, the optical signal power was amplified. For SOA group 222, each SOA is 120. R,1 -120 R,n / 2 Used to propagate to detector 270 n / 2+1 -270 n Previously, the optical signal power was amplified.

[0035] Figure 3 This is a scalable multi-band OCI transceiver architecture 300, further illustrated with embodiments of a dual-band transmitter architecture 100 including a polarization MUX and a dual-band receiver architecture 301 including a polarization DeMUX. For architecture 300, multiplexers 1251-125... mEach of these includes a 2×1 polarization rotator combiner that changes the signal propagated by waveguide 113 within one of blocks 101 and 102 from TE-guided mode to TM-guided mode propagating to the second input port of the 2×1 polarization MUX. On the receiver side, demultiplexers 2601-260... m WDM signals in TE and TM modes are received from coupler 130. In some embodiments, each DeMUX 260 includes an infinitely polarized DeMUX, such as a polarization beamsplitter that couples the TE mode signal to a first waveguide and the TM mode signal to a second waveguide, where the TM mode signal is further converted to TE mode (TE') by a polarization rotator. The two waveguides can be coupled via one or more MMI couplers, with phase control (e.g., via heater power) in at least one waveguide to achieve a known polarization state. Alternatively, each DeMUX 260 may include a polarization combiner. In other embodiments, each DeMUX 260 includes a PSR that separates the optical signal propagating in TE-guided mode from the optical signal propagating in TM-guided mode, which is further converted back to TE-guided mode (TE'). The TE and TE' modes output from each DeMUX 260 are coupled to signal detectors 2701-270, respectively. n / 2 and detector 270 n / 2+1 -270 n Alternatively, a band-specific SOA can also be incorporated into receiver architecture 301, for example, as described for receiver architecture 202.

[0036] Figure 4 The figure illustrates a PIC400 implementation of a dual-band OCI transceiver architecture for 16 channels, according to some embodiments. The PIC transceiver may include any of the photonic circuitry systems described above in the context of transmitter architecture 100, receiver architectures 201, 202, and transceiver architecture 300.

[0037] The PIC 400 is advantageously a single-chip transceiver comprising a monolithic region of substrate 105. Substrate 105 can have any composition suitable for fabricating planar optical waveguides. In advantageous embodiments, substrate 105 comprises one or more layers of silicon. Substrate 105 may comprise a device material layer of substantially pure monocrystalline silicon. The device material layer may be the top layer of a semiconductor-on-insulator (SOI) substrate material stack, which further comprises an underlying insulating material layer. In exemplary embodiments, where the device material layer is substantially pure silicon, the insulating material is advantageously primarily silicon and oxygen (e.g., SiO2). One or more additional substrate material layers may be located below or on the back side of the insulating material layer as mechanical support. For example, bulk silicon of any thickness (e.g., 20 μm–800 μm) may be on the back side of the insulating material. Substrate 105 may alternatively comprise other materials, such as a monolithic glass layer.

[0038] PIC 400 includes an optical transmitter circuitry 401 on a first region (coverage area) of substrate 105 and an optical receiver circuitry 402 on a second region of substrate 105. In an exemplary SiPh embodiment, the optical transmitter circuitry 401 implements a dual-band transmitter architecture 100. Figure 1 For example, optical waveguide 113 is a planar waveguide, which may include a ridge on substrate 105. The planar ridge waveguide may include silicon, for example, either as pure silicon or as a silicon-nitrogen compound, which may exhibit lower nonlinear losses than pure silicon.

[0039] In some embodiments, the optical transmitter circuitry 401 includes an integrated laser source 410. In other embodiments, indicated by the dashed box, the laser source 410 may be external to the PIC 400, and the optical transmitter circuitry 401 instead includes an additional fiber optic coupler (not depicted) to provide an interface to the external laser source. For embodiments with an integrated laser source, each optical emitter 111 is advantageously a laser diode, and more specifically, for the exemplary SiPh embodiment, each optical emitter 111 is a hybrid silicon laser diode. The hybrid silicon laser diode includes an active portion of a waveguide 113. The active waveguide portion is coupled to a passive portion of the waveguide 113, which, for example, has a larger lateral width than the active portion. The term “hybrid” refers to a non-silicon (e.g., III-V) material that can be bonded to the substrate 105. The III-V material may include any suitable PiN diode material stack, such as a quantum well (QW) or quantum dot (QD) material heterostructure comprising an n-type material layer and a p-type material layer. Such heterostructures can be, for example, III-V group crystalline alloy material systems, such as GaAs / InGaAs or InP / InGaP.

[0040] The first transmitter array 110 outputs an optical signal in a first (e.g., blue) band, which includes eight shorter wavelengths λ1-λ8. The second transmitter array 110 outputs an optical signal in a second (e.g., red) band, which includes eight longer wavelengths λ9-λ1. 16 The optical MUX / splitters 1121-1122 output DWM signals propagated by each of m optical waveguides 113, essentially as described above. In some embodiments where each MUX / splitter 112 includes an MMI coupler, the MMI coupler comprising m input ports optically coupled to m output ports via multimode waveguides, the multimode waveguides power-splitting the multiplexed signal across each output port. For the first band, each of the m waveguides 113 is coupled to eight MRMs and further coupled to one of the m blue SOA 120s in SOA group 121. For the second band, each of the m waveguides 113 is coupled to eight MRMs and further coupled to one of the m red SOA 120s in SOA group 122. Each SOA may include any suitable gain medium and / or pump architecture, and for some SiPh embodiments, may include one or more III-V materials heterogeneously integrated with substrate 105.

[0041] The output ports of SOA groups 121 and 122 are optically coupled via separate planar waveguides that transmit signals to the input ports of each of the m optical multiplexers 125 via one or more waveguide intersection arrays 131. Two or more optical waveguides 113 may cross within the waveguide intersection array 131 to route signals of different wavelengths to different input ports of the multiplexers 125. The waveguide intersection array 131 may include 2×2 waveguide crossovers, which may have any waveguide crossover architecture suitable for SiPh and providing acceptable crosstalk and / or optical loss. The waveguide crossovers may be planar direct crossovers, multimode interference-based planar crossovers, planar crossovers including resonant cavities, planar subwavelength grating crossovers, or any crossover structure including vertical couplers made of silicon, silicon nitride, polymers, etc.

[0042] The PIC 400 includes a first group of m fiber optic couplers 130 coupled to the output port of the multiplexer 125, and a second group of m fiber optic couplers 130 coupled to one of the m input signal conditioners 250 within the receiver 402. The PIC 400 may further include any of the photonic circuitry systems terminating at the 16 optical signal detectors 270 described above for the receiver architecture. SOA groups 221 and 222 are illustrated with dashed lines to emphasize that they are optional within the PIC 400.

[0043] The multi-band WDM OCI architecture according to the embodiments herein can have more than two bands. For a transmission throughput of n×m×R, the number of wavelengths n is divided by the number of bands k (k = 2, 4, ...), where each of the k bands comprises a smaller number of wavelengths n / k, which optimizes performance. Figure 5 This is a schematic diagram of a scalable multiband OCI transmitter architecture 500 based on some four-band (i.e., k=4) embodiments. For clarity, architecture 100 ( Figure 1 The reference numerals introduced in the figure are retained in architecture 500 ( Figure 5 In this embodiment, the photonic components are essentially identical. As shown, n channel wavelengths are divided into four distinct bands, each with the same number of wavelengths. The number of channel wavelengths may vary (e.g., 8, 16, 32, etc.), with each band consisting of 1 / 4 of the wavelengths (e.g., 2, 4, 8, etc.). Similar to the dual-band embodiment, the shortest wavelengths are grouped together within one band, while the longest wavelengths are grouped together within another band. The remaining half of the wavelengths are further divided into moderately short and moderately long bands. For transmitter architecture 500, wavelengths λ1-λ2 are... n It can span the above in transmitter architecture 100 ( Figure 1Any of the spectral ranges described in the context of λ1-λ n The channel spacing can similarly vary depending on the implementation. However, for some DWDM embodiments, the channel wavelength λ1-λ in at least one band is fixed. n / 4 , λ n / 4+1 -λ n / 2 , λ n / 2+1 -λ 3n / 4 , λ 3 / 4+1 -λ n The channel spacing is less than 1.6 nm (i.e., for 1550 nm, <200 GHz). The longest channel in the band (e.g., λ) n / 4 ) and the shortest channel of the next band (e.g., λ) n / 4+1 The inter-band spacing between bands may be approximately the same as the intra-band channel spacing between consecutive wavelengths within a band. Alternatively, the inter-band spacing may differ significantly from the intra-band channel spacing (e.g., greater than 50%).

[0044] The photonic circuit system for each of the four WDM bands further includes SOA1-SOA4. Dividing the channel count into more bands can further mitigate cross-gain modulation loss, four-wave mixing, and SOA nonlinearity, while reducing optical power saturation to achieve a better BER lower bound margin. In some embodiments, each of SOA1-SOA4 is band-specific. For example, each of SOA1-SOA4 may have a unique center wavelength suitable for the corresponding band. In some embodiments, the center wavelength of SOA1 is close to λ1-λ n / 4 The center of SOA4, while the center wavelength of SOA4 is close to λ. n / 4+1 -λ n / 2 The center. Alternatively, SOA1 and SOA2 can have the same center wavelength (e.g., close to λ). n / 4 SOA3 and SOA4 also have the same center wavelength (e.g., close to λ). 3n / 4 The center wavelength of SOA1 is different from that of SOA2.

[0045] The transmitter architecture 500 further includes a 4×1 MUX 525 for each of the m waveguides, which are coupled to one of the m fiber couplers 130. In some examples, the 4×1 MUX 525 includes at least one polarization rotator combiner that converts some TE-guided modes into TM-guided modes. Figures 6A-6C This is a schematic diagram of a 4×1 MUX according to some illustrative embodiments.

[0046] First refer to Figure 6AThe 4×1 MUX 525 includes three cascaded PRC 621s. A first pair of four waveguides transmitting the two shortest of the four bands is coupled to a pair of input ports of the first PRC 621. A second pair of four waveguides transmitting the two longest of the four bands is coupled to a pair of input ports of the second PRC 621. The output ports of each of the first and second PRC 621s are coupled to the input port of the third PRC 621. All wavelengths λ1-λ2 are included. n The WDM signals (some propagating in TE-guided mode and others in TM-guided mode) leave the third PRC 621.

[0047] Figure 6B The figure illustrates another embodiment of the 4×1 MUX 525, which includes 2×1 MMIs 622 and two 2×1 PRCs 621. In this example, a first pair of four-waveguides transmitting the two shortest of the four bands is coupled to a pair of input ports of the first PRC 621. A second pair of four-waveguides transmitting the two longest of the four bands is coupled to a pair of input ports of the second PRC 621. The output ports of each of the first and second PRCs 621 are coupled to the input ports of the MMIs 622, which combine those WDM signals propagating in TE-guided mode and those propagating in TM-guided mode.

[0048] Figure 6C The figure illustrates another embodiment of the 4×1 MUX 525, which includes two 2×1 MMIs 622 coupled to a 2×1 PRC 621. In this example, a first pair of four waveguides transmitting the two shortest bands of the four bands are coupled to a pair of input ports of the first MMI 622 for power combining, while a second pair of four waveguides transmitting the two longest bands of the four bands are coupled to a pair of input ports of the second MMI 622. The output ports of each of the first and second MMIs 622 are coupled to the input ports of the PRC 621, which converts the TE-guided mode from one of the MMIs 622 into a TM-guided mode, which is output along with the other TE-guided mode.

[0049] Figure 7A and Figure 7B This is a schematic diagram of a multi-band OCI receiver architecture according to some embodiments. First, refer to... Figure 7A OCI Receiver Architecture 701 and Receiver Architecture 201 ( Figure 2AIt is substantially the same and includes n wavelength-selective signal detectors 270 coupled to the optical waveguide via a signal conditioner 250, which further includes a PSR and a PC for converting WDM signals propagating in TE and TM modes to TE-only mode. Figure 7B The figure illustrates an OCI receiver architecture 702 including a 1×4 optical demultiplexer 760. In an embodiment that includes a PSR and a PC as signal conditioners 250, the demultiplexer 760 is a 1×4 band DeMUX. Utilizing the demultiplexer 760, architecture 702 can include k (e.g., 4) sub-band SOAs 120, which are optimized for a subset of n wavelengths, prioritizing a wideband SOA that provides lower performance for n wavelengths. In other embodiments, the demultiplexer 760 is a 1×4 polarization demultiplexer, and the optical circuitry system 770 has alternative configurations, such as... Figure 8 Further illustrations are provided.

[0050] Figure 8 The diagram illustrates an embodiment where the optical circuitry 770 includes a 1×2 PSR 852, which separates the received WDM optical signal propagating in TE and TM modes on a polarization basis, and then converts the signal propagating in TM mode to a TE-guided mode (TE'). One output port of the PSR 852 is coupled to the input port of a 1×2 (blue) bandpass filter 853, which is typically single-polarized and used for wavelengths λ1–λ2. n / 4 and wavelength λ n / 4+1 –λ n / 2 To distinguish between them. Another output port of the PSR 852 is coupled to the input port of a second 1×2 (red) BPF 853, which is used for wavelength λ. n / 4+1 -λ 3n / 4 and wavelength λ 3n / 4+1 -λ n Distinguishing between them. Although a 1×2 bandpass filter may cause optical loss, it enables the use of micro-ring interpolation filters with small free spectral range and / or large ring radius, and it can use band SOA to compensate for the loss.

[0051] Figure 9 The diagram illustrates a PIC900 implementation of a four-band OCI transceiver architecture for 32 channels, according to some embodiments. For clarity, the previous implementation of the dual-band OCI transceiver PIC400 (…) Figure 4 The reference numerals introduced are retained in architecture 900 for substantially the same optical components.

[0052] The PIC 900 is advantageously a single-chip transceiver comprising a monolithic region of substrate 105. In advantageous embodiments, substrate 105 comprises one or more layers of silicon. In an exemplary SiPh embodiment, optical transmitter circuitry 901 implements a four-band transmitter architecture 500 with planar waveguides. Figure 5 The optical transmitter circuitry 901 may include ridges on substrate 105. Planar ridge waveguides may include silicon, for example, either as pure silicon or as a compound of silicon and nitrogen (e.g., Si3N4). In some embodiments, the optical transmitter circuitry 901 includes an integrated laser source 410. In other embodiments, indicated by dashed boxes, the laser source 410 may be external to the PIC 900, and the optical transmitter circuitry 901 instead includes additional fiber optic couplers (not depicted) to provide an interface to an external laser source. Each optical transmitter 111 is advantageously a laser diode, and more specifically, for the exemplary SiPh embodiment, each optical transmitter 111 is a hybrid silicon laser diode.

[0053] As shown, the first transmitter array 110 outputs optical signals in a first band, which includes eight shorter wavelengths λ1-λ8. The second transmitter array 110 outputs optical signals in a second band, which includes eight longer wavelengths λ9-λ1. 16 The third transmitter array 110 outputs optical signals in the third band, which includes eight longer wavelengths λ. 17 -λ 24 The fourth transmitter array 110 outputs optical signals in the fourth band, which includes eight longer wavelengths λ. 25 -λ 32 The optical MUX / splitters 1121-1124 output DWM signals propagated by each of m optical waveguides 113, essentially as described above. In some embodiments where each of the MUX / splitters 112 includes an MMI coupler, the MMI coupler comprising optical coupling to an optical transmitter 1111-111 32The optical MUX / splitters 1121-1124 can all have substantially the same architecture. For the first band, each of the m waveguides 113 is coupled to eight MRMs and further coupled to one of the m SOAs, SOA 1201. For the second band, each of the m waveguides 113 is coupled to eight MRMs and further coupled to one of the m SOAs, SOA 1202. For the third band, each of the m waveguides 113 is coupled to eight MRMs and further coupled to one of the m SOAs, SOA 1203. For the fourth band, each of the m waveguides 113 is coupled to eight MRMs and further coupled to one of the m SOAs, SOA 1204. The output ports of SOA1-SOA4 are optically coupled via separate planar waveguides that transmit signals to the input ports of each of the m optical 4×1 multiplexers 525 via one or more waveguide intersecting arrays 131.

[0054] The PIC 900 includes a first set of m fiber optic couplers 130 coupled to the output port of the multiplexer 525, and a second set of m fiber optic couplers 130 coupled to one of the m input signal conditioners 250 within the receiver 902. The PIC 900 may further include any of the photonic circuitry systems terminating in the 32 optical signal detectors 270 described above for the receiver architecture.

[0055] The OCI transmitter and receiver architecture described in this paper, as well as the PIC transceiver implementation described further in this paper, can be used on a variety of systems and platforms. Figure 10A The diagram illustrates a computing cluster 1000 that includes a WDM OCI link comprising fiber optic cable 135 spanning a distance D between two computing systems 1006 and 1007. The distance D can range from a few centimeters to 250 meters. Computing systems 1006 and 1007 can each be commercial servers, including any number of high-performance computing units, configured, for example, within a rack. As further illustrated in the expanded view, the OCI link includes one PIC 400 providing an interface to a first computing unit 1091 of system 1006, and another PIC 400 providing an interface to a second computing unit 1092 of system 1007. PIC 400 includes one or more of the multiband features described elsewhere herein for PIC 400 (or PIC 900).

[0056] exist Figure 10B In this context, computing cluster 1000 includes alternative Tx-Rx fiber pairing options that facilitate PCIe / UCIe to fiber / wavelength mapping. One or both of computing units 1091 and 1092 may include optical waveguide cross switches (e.g., similar to...). Figure 4 and Figure 9 The cross switch 131 shown is used to map any fiber with any channel wavelength required for such paired Tx-Rx fiber packets.

[0057] Figure 11 This is a block diagram of a computing device 1100 according to some embodiments. For example, one or more components of the computing device 1100 may include any of the multi-band WDM transceivers discussed elsewhere herein. Multiple components in Figure 11 The components are illustrated as being included in computing device 1100, but any one or more of these components may be omitted or duplicated as appropriate for the application. In some embodiments, some of the components included in computing device 1100 may be attached to one or more printed circuit boards (e.g., a motherboard). In some embodiments, the individual components may be fabricated on a single system-on-a-chip (SoC) die, or implemented using multiple separate chiplets or dies packaged together. Additionally, in various embodiments, computing device 1100 may not include... Figure 11 The computing device 1100 may include one or more of the components shown in the figure, but may include an interface circuitry for coupling to the one or more components. For example, the computing device 1100 may not include a display device 1103, but may include a display device interface circuitry (e.g., a connector and driver circuitry) to which the display device 1103 may be coupled.

[0058] Computing device 1100 may include processing device 1101 (e.g., one or more processing devices). As used herein, the term processing device or processor indicates a device that processes electronic data from registers and / or memory to convert the electronic data into other electronic data that can be stored in registers and / or memory. Processing device 1101 may include memory 1121, communication device 1122, cooling / active cooling device 1123, battery / power regulation device 1124, logic 1125, interconnection 1126, thermal regulation device 1127, and hardware security device 1128.

[0059] Processing device 1101 may include one or more digital signal processors (DSPs), application-specific integrated circuits (ASICs), central processing units (CPUs), graphics processing units (GPUs), cryptographic processors (specialized processors that execute cryptographic algorithms within hardware), server processors, or any other suitable computing devices.

[0060] Processing device 1101 may include memory 1102, which itself may include one or more memory devices, such as volatile memory (e.g., dynamic random-access memory (DRAM)), non-volatile memory (e.g., read-only memory (ROM)), flash memory, solid-state memory, and / or hard drives. In some embodiments, processing device 1101 and memory 1102 share a package. The memory may be used as cache memory and may include embedded dynamic random-access memory (eDRAM) or spin transfer torque magnetic random-access memory (STT-M RAM).

[0061] The computing device 1100 may include a thermal regulation / cooling device 1123. The thermal regulation / cooling device 1123 can maintain the processing device 1101 (and / or other components of the computing device 1100) at a predetermined low temperature during operation. This predetermined low temperature can be any temperature discussed elsewhere herein.

[0062] In some embodiments, computing device 1100 may include communication chip 1107 (e.g., one or more communication chips). For example, communication chip 1107 may be configured to manage wireless communication for transmitting data to and from computing device 1100. The term "wireless" and its derivatives can be used to describe circuits, devices, systems, methods, techniques, communication channels, etc., that enable data transmission through non-solid-state media using modulated electromagnetic radiation.

[0063] Computing device 1100 includes PIC 400, such as one of the photonic WDM transceiver architectures described herein. For example, PIC 400 may facilitate communication between one or more instances of processing device 1101 and / or one or more instances of memory 1102.

[0064] The computing device 1100 may include a battery / power circuit system 1108. The battery / power circuit system 1108 may include one or more energy storage devices (e.g., batteries or capacitors) and / or circuitry for coupling components of the computing device 1100 to a power source (e.g., AC line power) that is separate from the computing device 1100.

[0065] The computing device 1100 may include a display device 1103 (or a corresponding interface circuitry system, as discussed above). The display device 1103 may include, for example, any visual indicator (such as a head-up display, computer monitor, projector, touch screen display, liquid crystal display (LCD), light-emitting diode display, or flat panel display).

[0066] The computing device 1100 may include an audio output device 1104 (or a corresponding interface circuitry system, as discussed above). The audio output device 1104 may include any device (such as a speaker, headset, or earphones) that generates auditory indicators.

[0067] The computing device 1100 may include an audio input device 1110 (or a corresponding interface circuitry system, as discussed above). The audio input device 1110 may include any device that generates a signal representing sound (such as a microphone, microphone array, or digital instrument (e.g., an instrument with a musical instrument digital interface (MIDI) output)).

[0068] The computing device 1100 may include a global positioning system (GPS) device 1109 (or a corresponding interface circuitry system, as discussed above). The GPS device 1109 may communicate with satellite-based systems and may receive the location of the computing device 1100, as is known in the art.

[0069] The computing device 1100 may include another output device 1105 (or a corresponding interface circuitry system, as discussed above). Examples include audio codecs, video codecs, printers, wired or wireless transmitters for providing information to other devices, or additional storage devices.

[0070] The computing device 1100 may include another input device 1111 (or a corresponding interface circuitry system, as discussed above). Examples may include an accelerometer, gyroscope, compass, image capture device, keyboard, cursor control device (such as a mouse), stylus, touchpad, barcode reader, Quick Response (QR) code reader, any sensor, or radio frequency identification (RFID) reader.

[0071] Computing device 1100 may include a security interface device 1112. Security interface device 1112 may include any device that provides security measures for computing device 1100, such as intrusion detection, biometric verification, secure encoding or decoding, management of access lists, malware detection, or spyware detection.

[0072] The computing device 1100 or a subset thereof may have any suitable form factor, such as a server or other networked computing component, mobile device, printer, scanner, monitor, set-top box, entertainment control unit, vehicle control unit, digital camera, digital video recorder, or wearable computing device.

[0073] Although certain features described herein have been described with reference to various implementations, this description is not intended to be limiting. Therefore, various modifications and other implementations of the implementations described herein that will be apparent to those skilled in the art to which this disclosure pertains are considered to fall within the spirit and scope of this disclosure.

[0074] It will be appreciated that the practice of the disclosed techniques and architectures is not limited to the embodiments described herein, but can be modified and changed without departing from the scope of the appended claims. For example, the above embodiments may include specific combinations of features further provided below.

[0075] In a first example, an apparatus includes: a first plurality of optical modulators coupled to a first optical waveguide for generating wavelength division multiplexing (WDM) optical signals with first plurality of intensity modulations across a first band comprising two or more channel wavelengths. The apparatus includes: a second plurality of optical modulators coupled to a second optical waveguide for generating second plurality of intensity-modulated WDM optical signals across a second band comprising two or more channel wavelengths, wherein the two or more channel wavelengths of the second band are longer than the two or more channel wavelengths of the first band. The apparatus includes: an optical multiplexer including a first input port and a second input port, the first input port being coupled to the first optical waveguide and the second input port being coupled to the second optical waveguide. The apparatus includes: a first semiconductor optical amplifier (SOA) coupled to the first optical waveguide between the multiplexer and the first plurality of modulators, the first SOA having a first center wavelength. The apparatus includes: a second semiconductor optical amplifier (SOA) coupled to the second optical waveguide between the multiplexer and the second plurality of modulators, the second SOA having a second center wavelength different from the first center wavelength.

[0076] In the second example, for any of the first examples, the device includes a first plurality of optical emitters multiplexed in a first optical waveguide. Each of the first plurality of optical emitters is used to output a single optical signal spanning a first wavelength band. The device includes a second plurality of optical emitters multiplexed in a second optical waveguide. Each of the second plurality of optical emitters is used to output a single optical signal spanning a second wavelength band.

[0077] In the third example, for either the first or second example, the modulator, the first optical waveguide and the second optical waveguide, the optical multiplexer, the first SOA and the second SOA are integrated on a single substrate comprising silicon.

[0078] In the fourth example, for any of the first to third examples, the 3dB gain bandwidth of the first SOA does not include at least one wavelength in the second band, and the 3dB gain bandwidth of the second SOA does not include at least one wavelength in the first band.

[0079] In the fifth example, for any of the first to fourth examples, the optical multiplexer includes a bandpass filter (BPF), a multimode interference (MMI) combiner, or a polarization rotator and combiner (PRC).

[0080] In the sixth example, for any of the first to fifth examples, the first band includes two channel wavelengths, and the second band includes two channel wavelengths. The first optical waveguide is one of at least two first optical waveguides. The second optical waveguide is one of at least two second optical waveguides. The first plurality of optical modulators and the second plurality of optical modulators each include two optical modulators. The first SOA is one of at least two first semiconductor optical amplifiers. Each of the first semiconductor optical amplifiers is coupled to a respective first optical waveguide in the first optical waveguide. The second SOA is one of at least two second semiconductor optical amplifiers. Each of the second semiconductor optical amplifiers is coupled to a respective second optical waveguide in the second optical waveguide. The optical multiplexer is one of at least two optical multiplexers. Each of the optical multiplexers is coupled to a single first optical waveguide in the first optical waveguide and a single second optical waveguide in the second optical waveguide.

[0081] In the seventh example, for any of the first to sixth examples, the device includes: a third plurality of optical modulators coupled to a third optical waveguide for generating a third plurality of intensity-modulated WDM optical signals spanning a third band of channel wavelengths, the channel wavelength of the third band being longer than that of the second band. The device includes: a third semiconductor optical amplifier (SOA) coupled to the third optical waveguide between the multiplexer and the third plurality of modulators, the third SOA having a third center wavelength different from the first and second center wavelengths. The device includes: a fourth plurality of optical modulators coupled to a fourth optical waveguide for generating a fourth plurality of intensity-modulated WDM optical signals spanning a fourth band of channel wavelengths, the channel wavelength of the fourth band being longer than that of the third band. The device includes: a fourth semiconductor optical amplifier (SOA) coupled to the fourth optical waveguide between the multiplexer and the fourth plurality of modulators, the fourth SOA having a fourth center wavelength different from the first, second, and third center wavelengths.

[0082] In the eighth example, for any of the seventh examples, the optical multiplexer is coupled to each of the first, second, third, and fourth optical waveguides, and the optical multiplexer includes at least one polarization rotator and combiner (PRC).

[0083] In the ninth example, for any of the eighth examples, the optical multiplexer includes a first PRC and a second PRC, the first PRC being coupled to a first optical waveguide and the second optical waveguide, and the second PRC being coupled to a third optical waveguide and a fourth optical waveguide.

[0084] In the tenth example, the device further includes a plurality of photodetectors (PDs) and a plurality of optical add-drop filters, wherein each of the PDs is coupled to an optical fiber coupler through a respective optical add-drop filter.

[0085] In the eleventh example, for any of the tenth examples, two or more subsets of the add-drop filter are coupled to an optical fiber coupler via at least one of a band demultiplexer or a polarization demultiplexer, and the SOA is coupled between each subset of the add-drop filter and the band demultiplexer or polarization demultiplexer.

[0086] In the twelfth example, for any of the eleventh examples, the first and second subsets of the add-drop filter are coupled to the polarization splitter rotator (PSR) via a first bandpass filter (BPF) or a first polarization rotator (PR) and a first polarization combiner (PC). The third and fourth subsets of the add-drop filter are coupled to the PSR via a second BPF or a second PR and a second PC. The PSR is further coupled to an optical fiber coupler.

[0087] In the thirteenth example, the photonic integrated circuit (PIC) includes wavelength division multiplexing (WDM) receiver circuitry and multi-band WDM transmitter circuitry. The WDM transmitter circuitry further includes: a first planar optical waveguide for transmitting a first plurality of intensity-modulated optical signals spanning a first band of the channel wavelength to an output optical multiplexer via a first semiconductor optical amplifier (SOA) having a first photoluminescence (PL) band. The WDM transmitter circuitry further includes: a second planar optical waveguide for transmitting a second plurality of intensity-modulated optical signals spanning a second band of the channel wavelength to an output optical multiplexer via a second SOA having a second PL band.

[0088] In the fourteenth example, for any of the thirteenth examples, the multi-band WDM transmitter circuit further includes n optical transmitters for outputting optical signals in n wavelength channels, with channel spacing between the n wavelength channels. The transmitter circuit includes: a first input optical multiplexer that couples each of m first planar optical waveguides to a first subset of the optical transmitters associated with a first band of the wavelength channels. The transmitter circuit includes: a second input optical multiplexer that couples each of m second planar optical waveguides to a second subset of the optical transmitters associated with a second band of the wavelength channels. The transmitter circuit includes: m first SOAs, and each of the first SOAs is coupled to one of the first planar optical waveguides. The transmitter circuit includes: m second SOAs, and each of the second SOAs is coupled to one of the second planar optical waveguides. The transmitter includes m output optical multiplexers. Each output optical multiplexer in the output optical multiplexer is coupled to a single fiber coupler among m fiber couplers. Each output optical multiplexer in the output optical multiplexer is coupled both to a single first planar optical waveguide in the first planar optical waveguide and to a single second planar optical waveguide in the second planar optical waveguide.

[0089] In the fifteenth example, and for any of the fourteenth examples, n is at least 8, m is at least 8, the first band and the second band each include at least 4 wavelength channels, and the transmitter includes a hybrid silicon III-V laser.

[0090] In the sixteenth example, and for any of the thirteenth to fourteenth examples, the WDM receiver circuit system includes: a second plurality of m fiber couplers and n photodetectors (PDs), the n photodetectors (PDs) being coupled to each fiber coupler through an optical add-drop filter.

[0091] In the seventeenth example, a system includes: a first computing unit; a second computing unit; and an optical computing interconnect (OCI) that couples the first computing unit to the second computing unit via optical fiber, wherein the OCI includes wavelength division multiplexing (WDM) receiver circuitry and multi-band WDM transmitter circuitry. The WDM transmitter circuitry includes an optical multiplexer coupled to a first planar optical waveguide for receiving a first plurality of intensity-modulated optical signals amplified by a first semiconductor optical amplifier (SOA) having a first center wavelength and spanning a first band of the channel wavelength, and the optical multiplexer coupled to a second planar optical waveguide for receiving a second plurality of intensity-modulated optical signals amplified by a second SOA having a second center wavelength and spanning a second band of the channel wavelength.

[0092] In the eighteenth example, for any of the seventeenth examples, the optical fiber is a single-mode optical fiber with a length of less than 250m, and the OCI includes: a first WDM receiver circuit and a first multi-band WDM transmitter circuit, coupled to opposite ends of the first optical fiber; and a second WDM receiver circuit and a second multi-band WDM transmitter circuit, coupled to opposite ends of the second optical fiber.

[0093] In the nineteenth example, and for any of the seventeenth to eighteenth examples, the WDM receiver circuit is a multi-band WDM receiver circuit, including at least one of an optical band demultiplexer or an optical polarization demultiplexer.

[0094] In the twentieth example, for any of the seventeenth to nineteenth examples, the optical fiber is one of at least eight optical fibers, the first band includes two channel wavelengths, the second band includes two channel wavelengths, the first band and the second band are coupled to each optical fiber in the optical fiber, and the first optical waveguide and the second optical waveguide each include a silicon-containing ridge on a silicon-containing substrate.

[0095] However, the above embodiments are not limited thereto, and in various implementations, the above embodiments may include employing only a subset of such features, different orders of employing such features, different combinations of employing such features, and / or additional features in addition to those expressly listed. Therefore, the scope of the disclosed technology and architecture should be determined with reference to the appended claims together with the full scope of the equivalents conferred by those claims.

Claims

1. An apparatus comprising: a first plurality of optical modulators coupled to a first optical waveguide for generating a first plurality of intensity-modulated wavelength division multiplexed (WDM) optical signals spanning a first waveband comprising two or more channel wavelengths; a second plurality of optical modulators coupled to a second optical waveguide for generating a second plurality of intensity-modulated WDM optical signals spanning a second waveband of two or more channel wavelengths that are longer than the two or more channel wavelengths of the first waveband; an optical multiplexer comprising a first input port coupled to the first optical waveguide and a second input port coupled to the second optical waveguide; a first semiconductor optical amplifier (SOA) coupled to the first optical waveguide between the multiplexer and the first plurality of modulators, the first SOA having a first center wavelength; and a second semiconductor optical amplifier (SOA) coupled to the second optical waveguide between the multiplexer and the second plurality of modulators, the second SOA having a second center wavelength different from the first center wavelength.

2. The apparatus of claim 1, further comprising: a first plurality of optical transmitters multiplexed into the first optical waveguide, wherein individual ones of the first plurality of optical transmitters are for outputting individual ones of the optical signals spanning the first waveband; and a second plurality of optical transmitters multiplexed into the second optical waveguide, wherein individual ones of the second plurality of optical transmitters are for outputting individual ones of the optical signals spanning the second waveband. the modulators, the first and second optical waveguides, the optical multiplexer, the first and second SOAs are integrated on a single substrate comprising silicon.

3. The apparatus of claim 1, wherein, a 3 dB gain bandwidth of the first SOA does not include at least one wavelength within the second waveband, and a 3 dB gain bandwidth of the second SOA does not include at least one wavelength within the first waveband.

4. The apparatus of claim 1, wherein, the optical multiplexer comprises a bandpass filter (BPF), a multimode interference (MMI) combiner, or a polarization rotator and combiner (PRC).

5. The apparatus of claim 1, wherein, 6. The apparatus of any one of claims 1-5, wherein: the first waveband comprises two channel wavelengths; the second waveband comprises two channel wavelengths; the first optical waveguide is one of at least two first optical waveguides; the second optical waveguide is one of at least two second optical waveguides; the first and second pluralities of optical modulators each comprise two optical modulators; the first SOA is one of at least two first semiconductor optical amplifiers, wherein individual ones of the first semiconductor optical amplifiers are coupled to individual ones of the first optical waveguides; and the second SOA is one of at least two second semiconductor optical amplifiers, wherein individual ones of the second semiconductor optical amplifiers are coupled to individual ones of the second optical waveguides. the second SOA is one of at least two second semiconductor optical amplifiers, wherein each of the second semiconductor optical amplifiers is coupled to a separate one of the second optical waveguides; the optical multiplexer is one of at least two optical multiplexers, wherein each of the optical multiplexers is coupled to a separate one of the first optical waveguides and a separate one of the second optical waveguides.

7. The apparatus of any of claims 1-5, further comprising: a third plurality of optical modulators coupled to a third optical waveguide for generating a third plurality of intensity-modulated WDM optical signals spanning a third band of channel wavelengths, the channel wavelengths of the third band being longer than the channel wavelengths of the second band; a third semiconductor optical amplifier (SOA) coupled to the third optical waveguide between the multiplexer and the third plurality of modulators, the third SOA having a third center wavelength different from the first and second center wavelengths; a fourth plurality of optical modulators coupled to a fourth optical waveguide for generating a fourth plurality of intensity-modulated WDM optical signals spanning a fourth band of channel wavelengths, the channel wavelengths of the fourth band being longer than the channel wavelengths of the third band; and a fourth semiconductor optical amplifier (SOA) coupled to the fourth optical waveguide between the multiplexer and the fourth plurality of modulators, the fourth SOA having a fourth center wavelength different from the first, second, and third center wavelengths.

8. The apparatus of claim 7, wherein, the optical multiplexer is coupled to each of the first, second, third, and fourth optical waveguides, and wherein the optical multiplexer includes at least one polarization rotator and combiner (PRC).

9. The apparatus of claim 8, wherein, the optical multiplexer includes a first PRC coupled to the first and second optical waveguides and a second PRC coupled to the third and fourth optical waveguides.

10. The apparatus of claim 1, further comprising a plurality of photodetectors (PDs) and a plurality of optical add / drop filters, wherein, each of the PDs is coupled to a fiber coupler by a separate one of the optical interleaver filters.

11. The apparatus of claim 10, wherein: two or more subsets of the interleaver filters are coupled to the fiber coupler by at least one of a band demultiplexer or a polarization demultiplexer; and an SOA is coupled between each of the subsets of interleaver filters and the band demultiplexer or the polarization demultiplexer.

12. The apparatus of claim 11, wherein: a first and second subset of the interleaver filters are coupled to a polarization split router (PSR) by a first bandpass filter (BPF) or a first polarization rotator (PR) and a first polarization combiner (PC); a third and fourth subset of the interleaver filters are coupled to the PSR by a second BPF or a second PR and a second PC; and the PSR is further coupled to the fiber coupler.

13. A photonic integrated circuit (PIC) comprising: a wavelength division multiplexed (WDM) receiver circuit; and a multi-band WDM transmitter circuit further comprising: a first planar optical waveguide for passing a first plurality of intensity modulated optical signals spanning a first band of channel wavelengths through a first semiconductor optical amplifier (SOA) having a first photoluminescence (PL) band to an output optical multiplexer; and a second planar optical waveguide for passing a second plurality of intensity modulated optical signals spanning a second band of channel wavelengths through a second SOA having a second PL band to the output optical multiplexer.

14. The PIC of claim 13, wherein, The multi-band WDM transmitter circuit further comprises: n optical transmitters for outputting optical signals at n wavelength channels having a channel spacing therebetween; a first input optical multiplexer coupling each of m first planar optical waveguides to a first subset of the optical transmitters associated with a first band of the wavelength channels; a second input optical multiplexer coupling each of m second planar optical waveguides to a second subset of the optical transmitters associated with a second band of the wavelength channels; m first SOAs, wherein each of the first SOAs is coupled to one of the first planar optical waveguides; m second SOAs, wherein each of the second SOAs is coupled to one of the second planar optical waveguides; and m output optical multiplexers, wherein each of the output optical multiplexers is coupled to a separate one of m fiber couplers, and wherein each of the output optical multiplexers is coupled to both a separate one of the first planar optical waveguides and a separate one of the second planar optical waveguides.

15. The PIC of claim 14, wherein: n is at least 8; m is at least 8; each of the first band and the second band comprises at least 4 wavelength channels; and the transmitters comprise hybrid silicon III-V lasers.

16. The PIC of any of claims 13-15, wherein, The WDM receiver circuit comprises: a second plurality of m fiber couplers; and n photodetectors (PDs) coupled to each of the fiber couplers, wherein each of the PDs is coupled through an optical add-drop filter.

17. A system comprising: a first computing unit; a second computing unit; and an optical computing interconnect (OCI) coupling the first computing unit to the second computing unit through an optical fiber, wherein the OCI comprises: a wavelength division multiplexed (WDM) receiver circuit; and a multi-band WDM transmitter circuit further comprising: a first planar optical waveguide for passing a first plurality of intensity modulated optical signals spanning a first band of channel wavelengths through a first semiconductor optical amplifier (SOA) having a first photoluminescence (PL) band to an output optical multiplexer; and a second planar optical waveguide for passing a second plurality of intensity modulated optical signals spanning a second band of channel wavelengths through a second SOA having a second PL band to the output optical multiplexer. The multi-band WDM transmitter circuit further comprises: n optical transmitters for outputting optical signals at n wavelength channels having a channel spacing therebetween; a first input optical multiplexer coupling each of m first planar optical waveguides to a first subset of the optical transmitters associated with a first band of the wavelength channels; a second input optical multiplexer coupling each of m second planar optical waveguides to a second subset of the optical transmitters associated with a second band of the wavelength channels; m first SOAs, wherein each of the first SOAs is coupled to one of the first planar optical waveguides; m second SOAs, wherein each of the second SOAs is coupled to one of the second planar optical waveguides; and m output optical multiplexers, wherein each of the output optical multiplexers is coupled to a separate one of m fiber couplers, and wherein each of the output optical multiplexers is coupled to both a separate one of the first planar optical waveguides and a separate one of the second planar optical waveguides.

15. The PIC of claim 14, wherein: n is at least 8; m is at least 8; each of the first band and the second band comprises at least 4 wavelength channels; and the transmitters comprise hybrid silicon III-V lasers. The WDM receiver circuit comprises: a second plurality of m fiber couplers; and n photodetectors (PDs) coupled to each of the fiber couplers, wherein each of the PDs is coupled through an optical add-drop filter.

17. A system comprising: a first computing unit; a second computing unit; and an optical computing interconnect (OCI) coupling the first computing unit to the second computing unit through an optical fiber, wherein the OCI comprises: a wavelength division multiplexed (WDM) receiver circuit; and A multi-band WDM transmitter circuit, the multi-band WDM transmitter circuit including an optical multiplexer coupled to a first planar optical waveguide for receiving a first plurality of intensity modulated optical signals spanning a first band of channel wavelengths amplified by a first semiconductor optical amplifier (SOA) having a first center wavelength, and coupled to a second planar optical waveguide for receiving a second plurality of intensity modulated optical signals spanning a second band of channel wavelengths amplified by a second SOA having a second center wavelength.

18. The system of claim 17, wherein: the optical fibers are single mode optical fibers having a length of less than 250 m; and the OCI includes: a first WDM receiver circuit and a first multi-band WDM transmitter circuit coupled to opposite ends of a first optical fiber of the optical fibers; and a second WDM receiver circuit and a second multi-band WDM transmitter circuit coupled to opposite ends of a second optical fiber of the optical fibers.

19. The system of any of claims 17-18, wherein, the WDM receiver circuit is a multi-band WDM receiver circuit including at least one of an optical band demultiplexer or an optical polarization demultiplexer.

20. The system of any of claims 17-18, wherein: the optical fibers are one of at least 8 optical fibers; the first band includes 2 channel wavelengths; the second band includes 2 channel wavelengths; the first band and the second band are coupled to each of the optical fibers; and the first optical waveguide and the second optical waveguide each include a silicon- comprising ridge over a substrate comprising silicon.

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