Optical systems exploiting remote sources, coherent photonic interposer circuits and electronic-photonic integrated circuits

Abstract

The increasing demands in applications exploiting photonic communications are moving emphasis towards coherent modulation formats to further increase capacity. Compared to conventional on-off keying modulation formats within current optical communications networks coherent modulation formats encode information in both phase and amplitude of the optical signal. However, managing coherent communications is more complex than on-off keying and accordingly partitioning the electrical and photonic domains becomes attractive such that each domain is directed to the functionality best suited to it rather than seeking to force all functionality into the photonic domain. Configurations of the invention provide methods and systems for interfacing electronic integrated circuit (ICs) with coherent photonic interposer circuits and coherent photonic electronic interface circuits for increased spectral efficiency, bandwidth and link budget of links and optical switches interfacing electronic ICs.

Description

OPTICAL SYSTEMS EXPLOITING REMOTE SOURCES, COHERENT PHOTONIC INTERPOSER CIRCUITS AND ELECTRONIC-PHOTONIC INTEGRATED CIRCUITSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application claims the benefit of priority from U.S. Provisional Patent Application 63 / 701,737 filed October 1, 2024 and U.S. Provisional Patent Application 63 / 797,366 filed April 30, 2025; the entire contents of each being incorporated herein by reference.FIELD OF THE INVENTION

[0002] This patent application is directed to photonic interconnects and routing for interfacing electronic integrated circuits (ICs) and more particularly to remote photonic sources and routing architectures for interfacing electronic ICs, photonics integrated circuits (PICs), and coherent photonic interposer circuits (CPICs) / coherent photonic electronic interface circuits (CEICs) for increasing spectral efficiency, bandwidth and link budget of links interfacing electronic ICs.BACKGROUND OF THE INVENTION

[0003] Photonics has become a dominant or evolving technological solution in a wide range of applications from sensing, biomedical sensing, to quantum computing, quantum sensing, and telecommunications. Within communications streaming media, mobile data traffic, and cloud computing continue to fuel an increasing demand for bandwidth. Further, increasing demands for bandwidth and interconnection speed are migrating from the external system interfaces to internal interfaces between printed circuit boards or between ICs on a PCB.

[0004] In order to meet increasing demands in all of these applications photonic communications are moving towards coherent modulation formats to further increase capacity. Compared to conventional on-off keying modulation formats within current optical communications networks coherent modulation formats encode information in both phase and amplitude of the optical signal.

[0005] Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments in conjunction with the accompanying figures.SUMMARY OF THE INVENTION

[0006] It is an object of the present invention to mitigate limitations in the prior art relating to photonic interconnects and routing for interfacing electronic integrated circuits (ICs) and more particularly to remote photonic sources and routing architectures for interfacing electronic ICs and coherent photonic interposer circuits (CPICs) / coherent photonic electronic interface circuits (CEICs) for increasing spectral efficiency, bandwidth and link budget of links interfacing electronic ICs.

[0007] In accordance with an embodiment there is provided a method comprising: a plurality of M nodes; an optical emitter generating continuous wave (CW) or pulsed optical signals at a plurality of N wavelengths and an NxM optical switch where each output of the M outputs of the NxM switch is optically connected to an input port of a predetermined node of the plurality of M nodes; an at least MxM wavelength dependent router wherein each input of the M inputs of the at least MxM wavelength dependent router is coupled to an output port of another predetermined node of the plurality of M nodes and each output of the M outputs of the at least MxM router is coupled to another input port of a further predetermined node of the plurality of M nodes; wherein each node of the plurality of M nodes encodes data onto the CW optical signals it receives from the optical emitter; the wavelength of the N wavelengths coupled to each node of the plurality of M nodes is established in dependence upon a routing configuration of the at least MxM wavelength dependent router and which other node of the plurality of M nodes the node of the plurality of M nodes is to transmit data to; andN and M are each positive integers greater than or equal to 2.

[0008] In accordance with an embodiment there is provided a method comprising: a plurality of M nodes; an optical emitter generating continuous wave (CW) or pulsed optical signals at a plurality of N wavelengths and at least aNx2M optical switch where each output of a first set of M outputs of the Nx2M switch is optically connected to an input port of a predetermined node of the plurality of M nodes and each output of a second set of M outputs of the at least a Nx2M switch is optically connected to an input port of a coherent receiver forming part of a different predetermined node of the plurality of M nodes;an at least MxM wavelength dependent router wherein each input of the M inputs of the at least MxM wavelength dependent router is coupled to an output port of another predetermined node of the plurality of M nodes and each output of the M outputs of the at least MxM router is coupled to another input port of a further predetermined node of the plurality of M nodes; wherein each node of the plurality of M nodes incorporates a coherent transmitter to encode data onto the CW or pulsed optical signals it receives from the optical emitter where the wavelength of the N wavelengths coupled to that node of the plurality of M nodes is established in dependence upon a routing configuration of the at least MxM wavelength dependent router and which other node of the plurality of M nodes the node of the plurality of M nodes is to transmit data to;N and M are each positive integers greater than or equal to 2; each node of the plurality of nodes incorporates the coherent receiver which receives the encoded optical signal from the at least MxM wavelength dependent router of the node of the plurality of M nodes transmitting data to it at the wavelength of the N wavelengths coupled to that node of the plurality of M nodes and a CW optical signal at the wavelength of the N wavelengths coupled to it directly from the at least aNx2M router.

[0009] In accordance with an embodiment there is provided a method comprising: a coherent photonic interposer (CPI) comprising a number N coherent photonic interposer circuits (CPICs); andN coherent electronic integrated circuits (CEIC) where each CEIC is electrically coupled to a defined CPIC of the N CPICs; wherein each CEIC receives: data for transmission from an electronic circuit of a set of electronic circuits and provides other data and control signals for the associated CPIC to coherently modulate a continuous wave (CW) or pulsed optical signals coupled to the associated CPIC; and a set of electrical signals from a coherent receiver forming part of the associated CPIC to generate further data for transmission to another electronic circuit of the set of electronic circuits from the set of electrical signals where the CEIC provides other control signals to the associated CPIC to coherently detect another coherently modulated optical signal received by the CPIC; each CPIC receives:the CW or pulsed optical signals which is at a predetermined wavelength together with the other data and control signals from the CEIC associated with the CPIC and encodes the other data onto the CW or pulsed optical signals to generate a coherently modulated optical signal which is transmitted from the CPIC; and the another coherently modulated optical signal at another predetermined wavelength which is coherently detected to generate the set of electrical signals provided to the associated CEIC by a coherent receiver circuit which receives the other control signals from the associated CEIC and a CW or pulsed optical signals which is at the same or another predetermined wavelength; andN is an integer greater than or equal to 1.

[0010] In accordance with an embodiment there is provided a method comprising: an input optical interleaver to deinterleave an input optical signal comprising a number of optical signals upon a defined grid of spacing X GHz into two output optical signals where each output of the input optical interleaver comprises optical signals upon a grid of spacing 2X GHz and the two output optical signals are offset relative to one another by X GHz; a pair of first wavelength selective switches (WSSs) where each first WSS is coupled to an output of the optical interleaver; a number of second WSSs where each second WSS is connected to a defined output of a defined first WSS of the pair of WSSs; and a number of output optical interleavers to interleave input optical signals to an output optical signal where each input to a defined output optical interleaver of the number of output optical interleavers comprises optical signals from a defined second WSS of the number of second WSSs upon the grid of spacing 2X GHz and the output of each output optical interleaver of the number of output optical interleavers comprises optical signals upon the defined grid of X GHz spacing; whereinX is positive.

[0011] In accordance with an embodiment there is provided a method comprising: a waveguide coupled to an input for receiving a number M optical signals at a number of M wavelengths; along the waveguide a number N wavelength tunable couplers where each wavelength tunable coupler is tunable over a defined wavelength range such that the wavelength tunable coupler can be tuned to either couple a defined optical signal of the M optical signalsfrom the waveguide to an output port or not couple any optical signal of the M optical signals from the waveguide; whereinN and M are positive integers.

[0012] Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments in conjunction with the accompanying figures.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Embodiment are described, by way of example only, with reference to the attached Figures, wherein:

[0014] Figure 1A depicts a general topology of a photonic switch for a computer cluster exploiting a remote reconfigurable photonic source and wavelength selective router;

[0015] Figure IB depicts a general topology of a photonic switch for a computer cluster exploiting a remote reconfigurable photonic source and wavelength selective router with coherent photonic links;

[0016] Figure 2 depicts an exemplary topology of a 4-node computer cluster exploiting a photonic switch with a remote reconfigurable photonic source and wavelength selective router;

[0017] Figure 3 depicts a switch system exploiting a coherent photonic interposer (CPI) comprising coherent photonic interposer circuits (CPICs) for interfacing to coherent electronic interface circuits (CEICs) and therein an electronic circuit according to an embodiment;

[0018] Figure 4A depicts electronic circuits communicating via an optical link which interfaces either end with a CPI comprising CPICs for interfacing to CEICs and therein the electronic circuits according to an embodiment;

[0019] Figure 4B depicts a variant of the system according to an embodiment as depicted in Figure 4A;

[0020] Figures 5 A and 5B depict cross-sections of exemplary assemblies such as that depicted in Figures 3, 4A and 4B comprising optical interfaces with a CPI comprising CPICs for interfacing to CEICs and therein the electronic circuits according to an embodiment;

[0021] Figure 6 depicts an exemplary CPIC - CEIC architecture according to an embodiment;

[0022] Figure 7 depicts an exemplary CPIC - CEIC architecture according to an embodiment;

[0023] Figure 8 depicts a reconfigurable laser source according to an embodiment for use within other embodiments;

[0024] Figure 9 depicts a reconfigurable laser source according to an embodiment for use within other embodiments;

[0025] Figure 10 depicts a reconfigurable laser source according to an embodiment for use within other embodiments;

[0026] Figure 11 depicts a reconfigurable laser source according to an embodiment for use within other embodiments;

[0027] Figures 12A and 12B depict reconfigurable laser sources according to an embodiment for use within other embodiments;

[0028] Figure 13 depicts a node interconnection configuration according to an embodiment employing a wavelength selective laser (WSL) bank;

[0029] Figure 14 depicts a configuration for a WSL bank employing micro-ring resonators supporting a node interconnection configuration such as depicted in Figure 13;

[0030] Figure 15 depicts a multi-path communications network exploiting reconfigurable laser banks with multiple sub-networks; and

[0031] Figure 16 depicts a multi-path communications network exploiting reconfigurable laser banks with multiple sub-networks.DETAILED DESCRIPTION

[0032] The present invention is directed to photonic interconnects and routing for interfacing electronic integrated circuits (ICs) and more particularly to remote photonic sources and routing architectures for interfacing electronic ICs, photonic integrated circuits (PICs), and coherent photonic interposer circuits (CPICs) / coherent photonic electronic interface circuits (CEICs) for increasing spectral efficiency, bandwidth and link budget of links interfacing electronic ICs.

[0033] The ensuing description provides representative embodiment(s) only, and is not intended to limit the scope, applicability or configuration of the disclosure. Rather, the ensuing description of the embodiment(s) will provide those skilled in the art with an enabling description for implementing an embodiment or embodiments. It would be understood by one of skill in the art that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the claims. Accordingly, an embodiment is an example or implementation and not the sole implementation. Various appearances of “one embodiment,” “an embodiment” or “some embodiments” do not necessarily all refer to the same embodiments. Although various features may be described inthe context of a single embodiment, the features may also be provided separately or in any suitable combination. Conversely, whilst embodiments may be described herein in the context of separate embodiments for clarity, the invention can also be implemented in a single embodiment or any combination of embodiments.

[0034] Reference in the specification to “one embodiment,” “an embodiment,” “some embodiments” or “other embodiments” means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least one embodiment, but not necessarily all embodiments. The phraseology and terminology employed herein is not to be construed as limiting but is for descriptive purposes only. It is to be understood that where the claims or specification refer to “a” or “an” element, such reference is not to be construed as there being only one of that element. It is to be understood that where the specification states that a component feature, structure, or characteristic “may,” “might,” “can” or “could” be included, that particular component, feature, structure, or characteristic is not required to be included.

[0035] Reference to terms such as “left,” “right,” “top,” “bottom”, “front” and “back” are intended for use in respect to the orientation of the particular feature, structure, or element within the figures depicting embodiments. It would be evident that such directional terminology with respect to the actual use of a device has no specific meaning as the device can be employed in a multiplicity of orientations by the user or users.

[0036] Reference to terms “including,” “comprising,” “consisting” and grammatical variants thereof do not preclude the addition of one or more components, features, steps, integers or groups thereof and that the terms are not to be construed as specifying components, features, steps or integers. Likewise, the phrase “consisting essentially of,” and grammatical variants thereof, when used herein is not to be construed as excluding additional components, steps, features integers or groups thereof but rather that the additional features, integers, steps, components or groups thereof do not materially alter the basic and novel characteristics of the claimed composition, device or method. If the specification or claims refer to “an additional” element, that does not preclude there being more than one of the additional elements.

[0037] A “two-dimensional” waveguide, also referred to as a 2D waveguide or a planar waveguide, as used herein may refer to, but is not limited to, an optical waveguide supporting propagation of optical signals within a predetermined wavelength range which guides the optical signals vertically relative to a substrate upon which the 2D waveguide is formed but does not guide the optical signals laterally relative to the propagation direction of the optical signals within the 2D waveguide.

[0038] A “three-dimensional” waveguide, also referred to as a 3D waveguide, a channel waveguide, or simply waveguide as used herein may refer to, but is not limited to, an optical waveguide supporting propagation of optical signals within a predetermined wavelength range which guides the optical signals vertically relative to the substrate upon which the 3D waveguide is formed as well as laterally relative to the propagation direction of the optical signals within the 3D waveguide.

[0039] A “photonic integrated circuit” (PIC) as used herein may refer to, but is not limited to, the monolithic integration of multiple integrated optics devices into a circuit formed upon a common substrate providing an optical routing and processing functionality. The PIC is fabricated using processing techniques at a wafer level, e.g. semiconductor manufacturing, CMOS manufacturing flows, MEMS processing flows, and post-processing flows etc.

[0040] Embodiments may refer to the term “hybridly integrated” which may refer to, but not be limited to, the “integration” of an optical element onto a substrate by attaching the optical element or another element physically integrated with the optical element to the substrate (platform) such that the optical element is retained in position. Such attachment means may include, but not be limited to, soldering, epoxy, van der Waals forces, electrostatic attachment, magnetic attachment, physical interlocking and friction. Accordingly, in these embodiments the optical element being hybridly integrated may be viewed as being implemented within a parallel manufacturing process to the other optical element(s) prior to being co-assembled. This parallel manufacturing process may employ one or more processes selected from the group comprising, but not limited to, liquid phase epitaxy (LPE), metal organic chemical vapor deposition (MOCVD), organometallic vapor-phase epitaxy (OMVPE), Low-Pressure Chemical Vapor Deposition (LPCVD), Plasma-Enhanced Chemical Vapor Deposition (PECVD), selective area epitaxy, an additive manufacturing process, a non-additive manufacturing process, crystal growth, doping, induced damage, etching, doping and deposition.

[0041] This may, within other embodiments, refer to, but not be limited to, the “integration” of an optical element onto a substrate using a different manufacturing methodology and / or techniques to those employed in forming other optical components upon the substrate. For example, this may employ an LPE process to form the other optical element upon the substate wherein the optical component upon the substrate was formed by MOCVD or vice-versa. Alternatively, both the optical component and other optical component may be fabricated using the same manufacturing methodology or a combination of manufacturing methodologies. These manufacturing methodologies may employ one or more processes selected from thegroup comprising, but not limited to, LPE, MOCVD, OMVPE, selective area epitaxy, an additive manufacturing process, anon-additive manufacturing process, crystal growth, doping, induced damage, etching, doping, deposition, an additive manufacturing process and a nonadditive manufacturing process. Accordingly, in these embodiments the optical element being hybridly integrated may be viewed as being implemented within one or more further processing stages of the same manufacturing process as the other optical element(s). However, in each instance the optical waveguide and / or optical component properties require that an optical interface be implemented between the optical waveguide and optical component in order to provide efficient optical coupling between one and the other.

[0042] An optical element may employ one or more semiconductors grown using LPE, MOCVD, and OMVPE, for example. The one or more semiconductors may be selected from, but not limited to, group III-V semiconductors, group II-VI semiconductors, group IV semiconductors, and group IV-V-VI semiconductors. Examples of group III-V semiconductors may include A1P, AIN, AlGaSb, AlGaAs, AlGalnP, AlGaN, AlGaP, GaSb, GaAsP, GaAs, GaN, GaP, InAlAs, InAlP, InSb, InGaSb, InGaN, GalnAlAs, GalnAlN, GalnAsN, GalnAsP, GalnAs, GalnP, InN, InP, InAs, InAsSb, and AllnN. Examples of group II-VI semiconductors may include ZnSe, HgCdTe, ZnO, ZnS, and CdO. Examples of group IV Semiconductors may include Si, Ge, and strained silicon. A group IV-V-VI semiconductor may be GeSbTe.

[0043] Within embodiments the platform or substrate upon which the integration is performed may be a silicon substrate wherein the one or more optical waveguides upon the platform exploit a silicon nitride core with silicon oxide upper and lower cladding, a SiO2— Si2N4— SiO2waveguide structure. Alternatively, the one or more optical waveguides may employ a silicon core with silicon nitride or silicon oxide as upper and lower claddings. Optionally, the upper cladding may be omitted within other embodiments.

[0044] However, other optical waveguide structures may be employed including, but not limited to, silica-on-silicon, doped (e.g., germanium, Ge) silica core with undoped cladding, silicon oxynitride, polymer-on-silicon, thin-fdm lithium niobate, thin-film lithium tantalate, or doped silicon waveguides for example. Additionally, other waveguide structures may be employed including vertical and / or lateral waveguide tapers and forming microball lenses on the ends of the waveguides via laser and / or arc melting of the waveguide tip.

[0045] Further, whilst embodiments are described with respect to silicon-on-insulator (SOI) waveguides by way of example, e.g. SiO2— Si3N4— SiO2SiO2— Ge SiO2— SiO2or Si — SiO2; other embodiments may be employed to coupled passive waveguides to activesemiconductor waveguides, such as indium phosphide (InP) or gallium arsenide (GaAs), e.g. a semiconductor optical amplifier (SOA), laser diode, etc. Optionally, an active semiconductor structure may be epitaxially grown onto a silicon IO-MEMS structure, epitaxially lifted off from a wafer and bonded to a silicon integrated optical microelectromechanical systems (IO- MEMS) structure, etc.

[0046] However, within other embodiments a variety of waveguide coupling structures coupling onto and / or from waveguides employing material systems that include, but not limited to, SiO2— Si3N4— SiO2SiO2— Ge: SiO2— SiO2Si — SiO2ion exchanged glass, ion implanted glass, polymeric waveguides, InGaAsP, GaAs, III-V materials, II-VI materials, thin-film lithium niobate, thin-film lithium tantalate, and optical fiber. Whilst primarily waveguide-waveguide systems have been described other embodiments may be employed in aligning intermediate coupling optics, e.g., ball lenses, spherical lenses, graded refractive index (GRIN) lenses, etc. for free-space coupling into and / or from a waveguide device.

[0047] Further, whilst embodiments are described primarily with respect to a silicon substrate other substrates may be employed within other embodiments. These may include, but not be limited to, a semiconductor, a ceramic, a metal, an alloy, a glass, or a polymer.

[0048] A “ceramic” as used herein may refer to, but is not limited to, an inorganic, nonmetallic solid material comprising metal, non-metal or metalloid atoms primarily held in ionic and covalent bonds. Such ceramics may be crystalline materials such as oxide, nitride or carbide materials, elements such as carbon or silicon, and non-crystalline. Exemplary ceramics may include high temperature ceramics or high temperature co-fired ceramics such as alumina (A12O3), zirconia (ZrO2), and aluminum nitride (AIN) or a low temperature cofired ceramic (LTCC). A LTCC may be formed from a glass - ceramic combination.

[0049] A “glass” as used herein may refer to, but is not limited to, a non-crystalline amorphous solid. A glass may be fused quartz, silica, a soda-lime glass, a borosilicate glass, a lead glass, an aluminosilicate glass for example. A glass may include other inorganic and organic materials including metals, aluminates, phosphates, borates, chalcogenides, fluorides, germanates (glasses based on GeO2), tellurites (glasses based on TeO2), antimonates (glasses based on Sb2O3), arsenates (glasses based on As2O3), titanates (glasses based on TiO2), tantalates (glasses based on Ta2O5), nitrates, carbonates, plastics, and an acrylic.

[0050] Further, whilst the embodiments are described and depicted with respect to a waveguide employing a core embedded within a cladding, a so-called buried waveguide, other waveguide geometries such as rib waveguide, diffused waveguide, ridge or wire waveguide, strip-loaded waveguide, slot waveguide, and anti-resonant reflecting optical waveguide (ARROWwaveguide), photonic crystal waveguide, suspended waveguide, alternating layer stack geometries, sub-wavelength grating (SWG) waveguides and augmented waveguides (e.g. Si — SiO2— Polymer). Further, whilst the embodiments are described and depicted with respect to a step-index waveguide other waveguide geometries such as graded index and hybrid index (combining inverse-step index and graded index) may be employed.

[0051] As noted above photonics has become a dominant or evolving technological solution in a wide range of applications from sensing, biomedical sensing, to quantum computing, quantum sensing, and telecommunications. Streaming media, mobile data traffic, and cloud computing continue to fuel an increasing demand for bandwidth in local area networks (LANS), metropolitan area networks (MANs), data centers and long haul networks as well as between servers or racks of servers. With these increasing demands for bandwidth and interconnection speed pressure is therefore applied to the interfaces at the other levels of the system such that photonics is migrating from the external system interfaces to internal systems interfaces between printed circuit boards rather than between servers etc. and even to between ICs on an interposer / package substrate, PCB or distributed modular PCB.

[0052] In order to meet increasing demands in all of these applications photonic communications are moving towards coherent modulation formats to further increase capacity. Compared to conventional on-off keying modulation formats within current optical communications networks coherent modulation formats encode information in both phase and amplitude of the optical signal.

[0053] Accordingly, embodiments provide optical interface circuits, referred to as coherent photonic interposer circuits (CPICs), to manage the photonic levels aspects of a coherent photonic link and opto-electronic interface circuits, referred to as coherent photonic electronic interface circuits (CEICs), to manage the electronic to photonic interfaces. Further, embodiments provide reduced system complexity and cost through employing remote photonic source banks, rather than requiring every transceiver to have its own photonic sources, whilst leveraging wavelength division multiplexing for increased bandwidth, switch speed, and power-free or power-efficient routing. The embodiments partition the electrical and photonic domains such that they are directed to functions best suited to them rather than seeking to force all functionality into the photonic domain as many prior art systems do.

[0054] The following specification is split into two sections. The first section outlines embodiments which address reducing system complexity and cost through remote photonic source banks, rather than requiring every transceiver to have its own photonic sources, and wavelength division multiplexing for increased bandwidth and power-free routing. The secondsection outlines embodiments exploiting coherent photonic interposer circuits (CPICs) to manage the photonic levels aspects of a coherent photonic link and coherent photonic electronic interface circuits (CEICs), to manage the electronic to photonic interfaces of coherent links at the IC and / or board level.

[0055] The embodiments are described and depicted with respect to Figures 1 and 2 which provide a switch system for a computer cluster with multiple compute nodes (e.g., servers, processor units, sub-clusters of processor units etc.). The system is built upon a remote reconfigurable laser bank (an embodiment of a remote photonic source bank) and a multipleport wavelength-selective routing device for power-free routing. The switch architectures depicted in Figures 1 and 2 may be employed with intensity-modulation direct-detection (IMDD) and coherent optical transmission-detection methodologies.

[0056] Figure 1A depicts a general topology 100A of a photonic switch for aNode Cluster 130 exploiting a Remote Reconfigurable Photonic Source (RRPS) 110 and Wavelength Selective Router 140. The RRPS 110 comprises an array of N fixed waveguide optical sources 102(1) to 102(N) which are coupled to a NxM Switch 104 such that the output of the RRPS 110 is M optical links which are connected to an array of M Compute Node 130(1) to 130(M) which are themselves coupled to the input ports of an MxM Wavelength Router 145 and to the output ports of the MxM Wavelength Router 145.

[0057] Each Compute Cluster 130 of the M Compute Node 130(1) to 130(M) does not contain optical sources but encodes data onto the wavelength coupled to it from the RRPS 110 which is then coupled to the MxM Wavelength Router 145 and therein back to a Compute Cluster 130 of the M Compute Node 130(1) to 130(M).

[0058] Accordingly, if Compute Cluster 130(1) wishes to transmit data to Compute Cluster 130(M) then the RRPS 110 is configured to transmit to the Compute Cluster 130(1) the wavelength which then coupled to the 1stinput port of the MxM Wavelength Router 145 is routed to the M* output port of the MxM Wavelength Router 145. Accordingly, the RRPS 110 configures the NxM Switch 104 to route the appropriate optical source of the N fixed waveguide optical Sources 102(1) to 102(N) to the Compute Cluster 130(1). Accordingly, the RRPS 110 removes the requirements for each Compute Cluster 130 to have a multi-wavelength optical source and / or for the topology 100 to employ a MxM optical switch. Accordingly, the Compute Cluster 130 generates optical signals per se but encodes data onto the optical signals it receives. Each Compute Cluster of the Compute Node 130(1) to 130(M) comprising an optical receiver to convert the optical signals coupled from the MxM Wavelength Router 145 to electrical signals the Compute Cluster can employ.

[0059] Within another embodiment the RRPS 110 is simply an array of tunable wavelength sources which are directly coupled to the Compute Cluster 130. However, such tunable optical sources are generally complex and limited optical power semiconductor devices whereas the RRPS 110 can employ lower complexity, lower cost semiconductor sources or higher power sources according to the optical link budget from the RRPS 110 to the detectors within the Compute Cluster.

[0060] The configuration described and depicted within Figure 1A exploits direct modulation as the description considers that only the optical signal routed to a Compute Cluster 130 is the one it encodes and which is wavelength routed by the MxM Wavelength Router 140 to the destination Compute Cluster 130. However, a minor modification to the RRPS and replacement of direct detection within the Compute Node 130 with coherent detectors that the topology 100 can support coherent detection and coherent communication techniques, protocols etc. This alternate architecture is depicted in Figure IB wherein the RRPS 115 now comprises aNx2M Switch 106 and Node Cluster 135 comprises an array of M Compute Node 130(1) to 130(M) wherein each Compute Node 130(1) to 130(M) now comprises a coherent receiver rather than the direct detection in Figure 1A such that each Compute Node 130(1) to 130(M) has a Coherent Receiver (Rx) 135(1) to 135(M) associated with it.

[0061] Accordingly, each Compute Node 130(1) to 130(M) now comprises a coherent modulator, e.g. phase modulator, rather than an amplitude modulator to encode the data upon the wavelength it receives which is appropriate for routing the data from that node to the intended receiving node. The Coherent Rx 135(1) to 135(M) in order to convert the appropriate wavelength coupled to its associated node from the Wavelength Selective Router 140. As depicted each Coherent Rx 135(1) to 135(M) is coupled to the Nx2M Switch 106 such that the Nx2M Switch 106 provides to each Coherent Rx 135(1) to 135(M) within a node receives the same wavelength as that employed by the node transmitting to it.

[0062] Within another embodiment the Nx2M switch is a bank of N 1x2 power splitters and a pair of NxM switches such that the wavelengths being provided to each Compute Node 130(1) to 130(M) for transmitting data are handled by one NxM switch and the wavelengths for the Coherent Rx 135(1) to 135(M) are handled by the other NxM switch. The bank ofN 1x2 power splitters may therefore direct a percentage X of the Sources 102(1) to 102(N) to the Compute Nodes 130(1) to 130(M) for transmitting data and the remaining (1-X) percent to the Coherent Rx 135(1) to 135(M).

[0063] Within embodiments the Sources 102(1) to 102(N) may for formed from one or more optical sources as known in the art. These may include, for example, an array of discretesemiconductor lasers, one or more arrays of semiconductor lasers monolithically or hybridly integrated and a broadband optical source with wavelength filtering and post-filter optical amplification. Alternatively, the Sources 102(1) to 102(N) may for formed from one or more source(s) employing micro-resonators for generating a comb of frequencies.

[0064] Within embodiments the Sources 102(1) to 102(N) may be aligned to a grid, e.g. an International Telecommunications Union (ITU) 50 GHz, 100 GHz or 200 GHz dense wavelength division multiplexing (DWDM) grids, an ITU 20nm coarse WDM (CWDM) grid, a system specific grid or a supplier specific grid. Optionally, according to the photonic technology(ies) employed for the different elements non-uniform channel spacings may be employed.

[0065] The wavelength range of the optical sources and therein the other photonic components may, for example, be within the 850nm band or within one or more of the original (O) band between 1260-1360nm, extended (E) band between 1360-1460nm, short (S) band between 1460-1530nm, conventional (C) band between 1530-1565nm and long (L) band between 1565- 1625nm. However, within other embodiments other wavelength ranges may be employed.

[0066] Within embodiments the NxM Optical Switch 104 in Figure 1A and / or the Nx2M Optical Switch 106 in Figure IB may be, according to the speed of reconfiguration of the links between the nodes of each of Cluster 130 in Figure 1A and Cluster 135 in Figure IB, based upon mechanical switching elements and / or matrices, microelectromechanical systems (MEMS) switching elements and / or matrices, photonic integrated circuit switch elements and / or matrices etc. Within embodiments the optical switch may include, but not be limited to, reconfigurable non-blocking or strictly non-blocking optical switch matrices and broadcast and select optical switches. Accordingly, embodiments may employ discrete or arrayed semiconductor optical amplifiers (SOAs), Mach-Zehnder Interferometer (MZI) switches in silicon-on-insulator (SOI) or III-V semiconductor material systems with carrier injection or depletion, a MZI matrix on thin-film lithium niobate (LiNbO3) or other material platforms with linear electro-optic effects, resonator-based switch matrices, e.g., using micro-ring add-drop filters with free carrier injection or depletion, MEMS switches or a combination thereof.

[0067] The optical switches may be slow or fast optical switches according to the design of the system with respect to the reconfiguration of communications between compute nodes. Accordingly, a slow switch may reconfigure the compute node interconnects on a timescale of milliseconds or microseconds whereas a fast switch may reconfigure the interconnection within nanoseconds or picoseconds. A benefit of fast reconfiguration is the ability of the interconnect to handle small network flows at a packet level where a flow may only last 100 ns for exampleor below 1 JJ.S. Accordingly, the interconnect may reconfigure at a packet level or to accommodate bursts of traffic.

[0068] The MxM wavelength router with a uniform channel grid for the optical sources may be an array waveguide (AWGR) routing device for example in which the connection between an input port to which output port depends on the input wavelength received by the input port. The MxM wavelength router may include optical amplification but otherwise be passive in respect of lacking any control of the routing other than solely by wavelength to a given port. Accordingly, within embodiments the wavelength router may exploit one or more of arrays of IxM switches, RxR sub-switches, RxS sub-switches, AWG routers, and waveguide technologies upon SOI, silicon-on-nitride (SiN), III-V and LiNbO3 for example.

[0069] Whilst the embodiments described and depicted in Figures 1A and IB have been described with a single wavelength from the RRPS to a Compute Node and therein via the Wavelength Selective Router to another Compute Node in another configuration multiple wavelengths may be fed to a single Compute Node such that the same data encoded by that Compute Node is transmitted to multiple Compute Nodes.

[0070] Now referring to Figure 2 there is depicted an exemplary topology of a 4-node Compute Cluster exploiting a photonic switch with a remote reconfigurable photonic source and wavelength selective router with an alternate routing for coherent detection.. The embodiment depicted being where the number of sources N=4 and the number of Compute Nodes M=4. Accordingly, there is depicted a RRPS 205, comprising a Source 210 comprising the array of 4 fixed waveguide optical sources (WOS) 102(1) to 102(4) which are coupled to Switch 220 and therein Cluster 230 comprising first to fourth 1x2 Elements 222(1) to 222(4) and a pair of 4x4 Switches 234(A) and 234(B) respectively. The Cluster 230 being coupled to the Wavelength Selective Router 240 which comprises first to eighth 1x4 Wavelength Filters 240(1) to 240(8). Accordingly, the signals from a Compute Node within the Cluster 230 are routed to another Compute Node within the Cluster 230 based upon the wavelength coupled to the Compute Node and the Wavelength Routing pattern of the Wavelength Selective Router 240.

[0071] Accordingly, as depicted Compute Node 232(1) is coupled to first 1x4 Wavelength Filters 240(1) for transmission and second 1x4 Wavelength Filters 240(2) for reception. As depicted the outputs 1, 2, 3 and 4 of first 1x4 Wavelength Filters 240(1) are coupled to ports 1, 2, 2, and 2 of the fourth, sixth and eighth 1x4 Wavelength Filters 240(4), 240(6) and 240(8) respectively. Ports 1, 2, 3, and 4 of the second 1x4 Wavelength Filters 240(2) are coupled toports 2, 3, 4 and 1 of the seventh, fifth, third and first 1x4 Wavelength Filters 240(7), 240(5), 240(3) and 240(1) respectively.

[0072] If first 4x4 Switch 234(A) couples second WOS 102(2) with wavelength 2 to first Compute Node 232(1) then this is routed by the Wavelength Selective Router 240 to the second Compute Node 232(2). Accordingly, to receive this signal at wavelength 2 with its coherent receiver the second Compute Node 232(2) needs to receive wavelength 2 from second WOS 102(2) via the second 4x4 Switch 234(B).

[0073] Within embodiments a channel from an Optical Source to Compute Node and therein to another Compute Node via the Wavelength Selective Router has been described with respect to a single channel or wavelength essentially to this point. However, a network designed to operate upon a CWDM grid, e.g. 20 nm, may be a low cost system in some embodiments by employing low cost sources, e.g. uncooled laser diodes. However, an alternate embodiment employs within each channel a comb of DWDM channels, e.g. 100GHz channels are upon a 0.8nm grid such that 8 wavelengths may fit within the CWDM filter allowing 8 channels of transmission (5.6nm wide comb overall) from each Compute Node to another Compute Node where each channel may be part of a single communication or parts of multiple communications between these compute nodes. Depending upon the design of the wavelength routing / switching elements 16 channels at 100 GHz or 16 channels at 50 GHz coupled be passed through the “CWDM” channel concurrently.

[0074] Each wavelength may be modulated according to the overall design of the system at rates of 2.4 Gb / s, lOGb / s, 20Gb / s, 40 Gb / s, lOOGb / s etc. Further, the distance between compute nodes may be short, long or ultra-long according to the design and partitioning of the optical sources / wavelength selective routing etc. with or without the use of erbium doped fiber amplifiers or Raman optical amplifiers, SOAs etc. Ultra-long may exceed 100s of kilometers.

[0075] Within Section 1 optical interconnection between compute nodes was presented with respect to wavelength dependent routing allowing for a reduce of overall power consumption relative to electronic switching matrices for data being transmitted at rates up to, and potentially above, 100 Gb / s per channel over long spans. Whilst direct detection and coherent detection architectures were discussed within this section the concept of an optical interconnection system comprising several electrical integrated circuits (ICs) and photonic integrated circuits (PICs) is extended to consider a single photonic interposer, as referred to herein, which transmits and receives optical signals through phase modulation or phase and amplitude modulation. On one-side the photonic interposer is connected electrically to other ICs etc. and on the other side connected photonically to other circuit boards, systems etc.

[0076] These elements connections may be through electrical and / or optical paths (such as metal traces, through vias and optical waveguides) that are embedded in the photonic interposer to local elements or remotely via optical fiber links to remote elements. In this manner, the electronic and photonic chips of the photonic interposer can also be interconnected to each other through the electrical and / or optical paths for energy / data conversion, transmissions, communications and storage through either electrical or optical signals and the photonic interposer can be coupled to optical fibers to transmit and receive optical power and signals over distance from other electronic or photonic systems that may or may not integrated on another photonic interposer.

[0077] Emphasis in the following description is with respect to coherent photonics which is regarded as costly and power-demanding due to the use of digital signal processing (DSP). However, embodiments exploit simplified coherent detection schemes and integrated photonics to largely mitigate these challenges. Integrated photonics being particularly beneficial as it allows for monolithic integration of the coherent transmitter and coherent receiver circuits to a common platform hybridly or monolithically integrated with electronic ICs with small footprints such that ultra-compact coherent transceivers become feasible to handle the interconnection of electronic ICs either intra-PCB or inter-PCB.

[0078] Referring to Figure 3 there is depicted a System 300 exploiting a coherent photonic interposer (CPI) 305 comprising coherent photonic interposer circuits (CPICs) 310 for interfacing to coherent photonic electronic interface circuits (CEICs) 320 and therein an electronic circuit, Application Specific Integrated Circuit 340 according to an embodiment. The CPI 3305 is depicted with first to fourth Circuits 330(A) to 330(D) which connection to other CPIs 305 within an overall system or back to the CPI 305 via the Fiber Array interfaces. Each optical fiber within each of the first to fourth Circuits 330(A) to 330(D) is coupled to a CPIC 310 and therein a CEIC 320 before the Application Specific Integrated Circuit (ASIC) 340.

[0079] Also depicted are first and second Laser Banks 320(A) and 320(B) within are coupled to first to second Optical Filter Arrays 325(A) and 325(B) which provide the optical signals to the CPICs 310 within the first to fourth Circuits 330(A) to 330(D). These optical signals may be for the transmission of data from a CPIC 310 or coherent detection of data by a CPIC 310 from a remote CPIC 310 employing coherent transmission.

[0080] Accordingly, data from the ASIC 340 is coupled to a CEIC 320 for transmission to another part of a system of which System 300 forms part of or another system. The CEIC 320 being coupled to a CPIC 310 and provides the appropriate power and / or data signals to theCPIC 310 to establish the optical encoding of the data using an optical signal provided to the CPIC 310 from a Laser Bank, e.g. forming part of one of the first and second Laser Banks 320(A) and 320(B), via an Optical Filter, e.g. forming part of one of the first and second Optical Filter Arrays 325(A).

[0081] Similarly, data received for the ASIC 340 is coupled to a CEIC 320 after transmission from another part of the system of which System 300 forms part of or another system. The CEIC 320 receiving the optical signal encoded with the data being coupled to a CPIC 310 which provides the appropriate power to the CPIC 310 and receives the data signals from the CPIC 310. Coherent detection of the received optical signal by the CPIC 310 is achieved by a coherent receiver which also receives an optical signal from a Laser Bank, e.g. forming part of one of the first and second Laser Banks 320(A) and 320(B) respectively, via an Optical Filter, e.g. forming part of one of the first and second Optical Filter Arrays 325(A) and 325(B) respectively.

[0082] Within other embodiments the first and second Laser Banks 320(A) and 320(B) respectively and first and second Optical Filter Arrays 325(A) and 325(B) respectively may be a common optical sub-system coupled to the System 300 and other systems such as one or more other Systems 300 such that the optical sub-system is coupled to the CPI 305 of each System 300 and therein the CPICs 310 within each System 300.

[0083] Whilst Figure 3 depicts a system exploiting coherent transmission and detection of data, a variant of the System 300 may exploit direct amplitude modulation and detection or that another variant of the System 300 may exploit some interfaces that support coherent transmission and detection of data and other interfaces that may exploit direct amplitude modulation and detection.

[0084] Optionally, a CPIC 310 may exploit a modulator combining a pair of 1x2 elements that can be set to 50:50 and 100:0 with phase modulators allowing the CPIC 310 to provide amplitude modulation when the pair of 1x2 elements are set to 50:50 and phase modulation when the pair of 1x2 elements that can be set to 100:0 so that the optical signal only passes through one phase modulator. Alternatively, a pair of 1x2 optical switches may select a MZI or phase modulator or a MZI may be implemented with a phase modulator before or after it wherein in one control configuration the MZI is set to full transmission and the phase modulator driven and in the other control configuration the phase modulator is not driven and the MZI is biassed and modulated. In this manner, a CPI 305 of a System 300 may be configurable for both direct and coherent transmission options.

[0085] Now referring to Figure 4A there is depicted a System 400 which depicts a pair of Electronic Circuits 440 upon first and second Systems 400A and 400B communicating via an optical link which interfaces either end to the first and second Systems 400A and 400B comprising CPICs 310 for interfacing to CEICs 320 and therein the Electronic Circuits 440 according to an embodiment. Each of first and second Systems 400A and 400B being similar in design to that of System 300 in Figure 3. However, rather than a single ASIC as depicted in Figure 3 the CEICs 320 are coupled on each of the left and right sides of each of the first and second Systems 400A and 400B to first and second Microprocessors 410(A) and 410(B) and first and second High Bandwidth Memories (BPMs) 420(A) and 420(B). Each of the first and second Systems 400A and 400B having the CPICs 310 coupled on the left and right sides to first and second Optical Filter Arrays 425(A) and 425(B) respectively which are each coupled to a common Laser Bank 430 which provides the optical signals to each of the first and second Systems 400 A and 400B.

[0086] Optionally, within other embodiments the first and second Optical Filter Arrays 425(A) and 425(B) may be coupled to the common Laser Bank 430 via other Fiber Arrays which form an optical bus between the first and second Systems 400A and 400B with appropriate power taps on each of the first and second Systems 400A and 400B which may be programmable to allow for the placement of multiple Systems together with a common Laser Bank 430 at an end of the sequence. This being depicted schematically in System 430 in Figure 4B wherein the Laser Bank 430 is coupled to the second System 400B and therein to the first System 400A via first and second Tap Arrays 435(A) and 435(B)

[0087] Referring to Figure 5 there is depicted a Cross-Section 500 of an exemplary assembly such as that depicted in Figures 3, 4A and 4B comprising optical interfaces with a CPI 530 such as CPI 305 in Figure 3 comprising CPICs 310 for interfacing to CEICs 320 and therein the Electronic Circuits 510 according to an embodiment. As depicted in Cross-Section 500 these Electronic Circuits 510 may be an ASIC such as depicted in Figure 3 or an xPU and / or HBM as depicted in Figures 4A and 4B respectively.

[0088] Also depicted are Optical Fiber 580 providing an optical interface to the CPI 530 such as forming part of a Fiber Array 330 in Figure 3. The CPI 530 comprises CPICs 310 wherein electrical connections from the CPICs 310 are made to the CEICs 320 and therein via the CPI 530 to the Electronic Circuits 510. Electrical connections are also provided to the CPICs 310 and CEICs 320 from a Carrier 560 via Substrate 550 upon which the CPI 530 is formed or disposed. Additional electrical connections may be made via Wirebond 540 from a Pad 570 on the Carrier 560 to the CPI 530.

[0089] The Carrier 560 is depicted as being interconnected to the Substrate 550 via solder balls although other techniques as known in the art may be employed. Electrical connections within the Substrate 550 may be electrical vias and multi-layer cofired ceramic substrates with electrical interconnections or via other techniques as known in the art may be employed. Electrical connections within the CPI 530 may be via electrical vias etc. Optical connections with then CPICs 310 have been omitted for clarity. Optical interconnects may exist within the CPI 530 and / or Substrate 550. Similarly, whilst the CEICs 320 and CPICs 310 have been depicted at the edges of the CPI 530 they may be disposed at other points across the CPI 530 according to the desired interconnection and the number / type / positioning of the Electronic Circuits 510.

[0090] A subset of the CEICs may be hybridly integrated upon the CPI with the CPICs whilst another subset of the CEICs may be monolithically integrated with the CPICs within the CPI according to the transmission speed(s), CPI substrate material and device technologies etc. Within another embodiment a further subset of the CEICs may be designed such that a part is monolithically integrated and another part hybridly integrated.

[0091] Whilst within Figures 3 to 5A the fiber interfaces have been depicted at the edge of the CPI 530 these may also be within the footprint of the CPI 530 and may be out of the plane of the CPI 530 where vertical emitters, such as vertical-cavity surface-emitting lasers (VCSELs) for example, are employed or other optical elements such as gratings change the plane of propagation of the optical signals to perpendicular to the CPI 530. Within other embodiments a vertical optical interface may be from the CPI 530 through the Substrate 550 and Carrier 560. Whilst within Figure 5A electrical interconnections are depicted within the body of the CPI 530 within other embodiments with the exception of electrical vias they may be only upon one or more surfaces of the CPI 530.

[0092] Now referring to Figure 5B there is depicted a Cross-Section 500 of an exemplary assembly such as that depicted in Figures 3, 4A and 4B comprising optical interfaces with a CPI 530 such as CPI 305 in Figure 3 comprising CPICs 310 for interfacing to CEICs 320 and therein the Electronic Circuits 510 according to an embodiment. As depicted the CPI 530 is now a discrete circuit attached upon the Substrate 550 and therein to the Carrier 560.

[0093] Now referring to Figure 6 there is depicted an exemplary CPIC - CEIC Architecture 600 according to an embodiment. The Architecture 600 comprising CPIC 600A and CEIC 600B for coherent transmission and detection. The CEIC 600B comprising on the upper transmit side a transmitter DSP (TX DSP) 645 which is coupled to Driver Circuit 640 which provides the appropriate DC and AC signals to the CPIC 600 A. On the lower receive side theCEIC 600B comprises transimpedance amplifier (TIA) Array 680 which is coupled with a receiver DSP (RX DSP) 685 which converts the electrical signals from the TIA Array 680 to data.

[0094] The CPIC 600A operates upon X-Polarisation and Y-Polarisations on the transmit side via first and second Photonic Modulator Circuit 610A and 61 OB respectively and on the receive side via first and second 90° Hybrid Circuits 660A and 670B respectively. Each of the first and second Photonic Modulator Circuit 610A and 610B respectively receive a Local Oscillator signal (a photonic CW signal with specific center wavelength and bandwidth) which is then split to first and second MZIs 630A and 630B respectively. The output of the second MZI 630B is coupled to a Phase Shifter 620 before these outputs of these paths are combined within the first Photonic Modulator Circuit 610A and combined with the output of the second Photonic Modulator Circuit 610B at first Polarisation Circuit 650(A) to generate the output of the transmit side of the CPIC 600 A.

[0095] The receive side of the CPIC 600A comprises a second Polarisation Circuit 650(B) which splits the received signal into the X-Polarisation and Y-Polarisations which are then processed by the first and second 90° Hybrid Circuits 660A and 670B respectively and which receive the local oscillator. The output of each of the first and second 90° Hybrid Circuits 660A and 670B respectively is coupled to two pairs of balanced photodetectors to generate I and Q signals which are then coupled to the CEIC 600B.

[0096] Optionally, the local oscillator for the transmit side and receive side may be different such that two different Local Oscillator connections to the CPIC 600A are provided. Optionally, a Local Oscillator may be integrated as part of the CPIC 600A. The local oscillator can be implemented in the forms of on-chip or hybrid integrated laser sources or remote laser sources.

[0097] Now referring to Figure 7 there is depicted an exemplary CPIC - CEIC Architecture 700 according to an embodiment. The Architecture 700 comprising CPIC 700 A and CEIC 600B for coherent transmission and detection. CEIC 600B being described and depicted in Figure 6. Similarly, the receive side of the CPIC 700A is as described and depicted in Figure 6. However, the upper transmit side now comprises first and second Photonic Modulator Circuit 710A and 710B respectively receive a Local Oscillator signal (a photonic CW signal with specific center wavelength and bandwidth) which is then split to first and second Ring Assisted MZIs 720A and 720B respectively. The output of the second Ring Assisted MZI 720B is coupled to a Phase Shifter 620 before these outputs of these paths are combined within the first Photonic Modulator Circuit 710A and then combined with the output of the secondPhotonic Modulator Circuit 71 OB at first Polarisation Circuit 650(A) to generate the output of the transmit side of the CPIC 700A.

[0098] Each of the first and second Ring Assisted MZIs 720A and 720B respectively employs a ring resonator upon each arm of the MZI. Within embodiments the ring resonator on each arm may be the same or they may be different to one another. Within other embodiments an arm may have two or more ring resonators whilst another has one ring resonator or both arms may have two or more ring resonators with the number per arm being equal or unequal.

[0099] Whilst within the embodiments described and depicted in respect of Figures 3A to 7 the optical path from or to each CPIC is depicted as being to another CPIC upon another CPI some CPICs may receive and transmit to other CPICs which are upon the same CPI so that high data rate communications between different circuits or portions of a circuit upon the same CPI are implemented to, for example, reduce power consumption, increase the distance between communicating elements, reduce electromagnetic interference or increase the data rate.

[0100] Whilst within the embodiments described and depicted in respect of Figures 3 A to 7 the number of CPICs upon the CPIs depicted is implied as being the same. However, the number of CPICs upon a CPI may be defined in dependence upon the desired interconnectivity of the system the CPI forms part of, e.g. left and right side communications as depicted in Figures 4A and 4B or left, right, up and down as depicted in Figure 3, and the electrical functionality of the system the CPI forms part of. Accordingly, a CPI with N CPICs may communicate to another CPI with M CPICs where N and M are both integers equal to or greater than 1.

[0101] Within embodiments a CPIC requires a CW optical signal at a wavelength defined in dependence upon the coherently modulated optical signal it is intended to coherently detect. This may be achieved through different control protocols at a layer above the photonic which has not been depicted for clarity. However, within other embodiments this may be encoded within a preamble of a communication from a CPIC which is amplitude modulated and defines the required wavelength for decoding the subsequent packet(s) of data.

[0102] Within Figures 1A to 2 there are reconfigurable laser banks, such as Remote Reconfigurable Photonic Source (RRPS) 110, RRPS 115 and RRPS 205 which in conjunction with optical switching provide multiple ports which are dynamically configurable in the optical wavelength(s) upon each port which are coupled to one or more photonic circuits which are local to or remote from each RRPS. Referring to Figure 8 there is depicted RRPS 800 accordingto an embodiment which may be employed within the embodiments described and depicted within Figures 1 to 7 or within other photonic networks, circuits etc.

[0103] As depicted in Figure 8 RRPS 800 receives at an input of the RRPS 800 the output of a multi-wavelength laser source (MWLS). This may, for example, exploit a Quantum Dot Multi-Wavelength Laser (QD MWL), an optical amplifier (semiconductor or fiber based) with optical filters (e.g. Lyot-type and Fabry -Perot), enhanced four-wave-mixing (FWM) via highly nonlinear fiber (HNLF) and an erbium-doped fiber amplifier (EDFA) in a fiber loop or a multiwavelength injection locking of quantum dot Fabry-Perot (FP) lasers by optical self-inj ection via an external cavity in order to generate the multi-wavelength comb.

[0104] This multi-wavelength comb from the MWLS, X(l) to Z(M). is coupled to a Waveguide 810 along which are disposed a number N optical rings 820(1) to 820(N) which can be tuned to selectively couple a defined wavelength from the Waveguide 810 into the optical ring. Accordingly, the N Optical Rings 820(1) to 820(N) are tuned via control voltages V(l) to V(N). Each optical ring of the N Optical Rings 820(1) to 820(N) is coupled via a coupler of N Couplers 830(1) to 830(N) to an output to provide outputs X(OP-l) to X(OP-N). In RRPS 800 the outputs of each coupler of the N Couplers 830(1) to 830(N) are coupled to Optical Amplifiers 840(1) to 840(N).

[0105] Within other embodiments according to the output power of the MWLS and the losses through the Waveguide 810, optical ring of the N Optical Rings 820(1) to 820(N) and coupler of the N Couplers 830(1) to 830(N) the Optical Amplifiers 840(1) to 840(N) may be omitted. Within other embodiments the Optical Amplifiers 840(1) to 840(N) may be replaced by an optical amplifier between the MWLS and the Waveguide 810.

[0106] A cross-section of the optical waveguide within a portion of the ring waveguide in each of the N optical rings 820(1) to 820(N) is depicted in Insert 850 wherein the optical waveguide sits between a p-j unction and an n-j unction, i.e. the optical waveguides are formed within a waveguide system supporting formation of p-doped regions, n-doped regions and intrinsic regions together with an electro-optic effect such as silicon, InP, GaAs, etc. Accordingly, the application of a voltage V across the p-n junction results in a change of the refractive index of the optical waveguide and a shift in its coupling to the Waveguide 810 such that the appropriate wavelength from the multiple wavelengths propagating in the Waveguide 810 can be coupled to that optical ring.

[0107] Within RRPS 800 the N Optical Rings 820(1) to 820(N) act as optical ring based switch elements and accordingly these may be replaced with other optical switch elements to route a wavelength from the MWLS to an output with another wavelength selective opticalswitch such as a tunable coupled-resonator optical waveguide (CROW) filters and tunable Mach-Zehnder Interferometer (MZI) filter. Similarly, the p-n junction in Insert 850 to exploit the electro-optic effect in the ring waveguides may be replaced with another tuning mechanism such as heaters to exploit the thermo-optic effect to induce optical phase shift within the ring waveguide.

[0108] Within embodiments M and N are positive integers. According to the design of the optical network / photonic circuits coupled to the outputs of the RRPS 800 M may be less than N, equal to N or greater than N.

[0109] Now referring to Figure 9 there is depicted RRPS 900 comprising a Source Array 900A and Routing Block 900B which are linked via Loop Waveguide 970 where Source Array 900A and Routing Block 900B are upon a common substrate. Within other embodiments the Loop Waveguide 960 may be a photonic wire bond, see for example “Photonic wire bonding methods and processes for the advanced packaging of photonic devices and systems” WO / 2023 / 159311, to connect Source Array 900A and Routing Block 900B which are different photonic circuits or via an optical fiber such that the Source Array 900A and Routing Block 900B can be remote from one another or disposed locally but at distances of centimeters, meters to kilometers for example.

[0110] Source Array 900A comprises M Input Couplers 910(1) to 910(M) which receive optical signals at wavelengths L(l) to L(M) wherein each Input Coupler is coupled to an Input Ring of M Input Rings 920(1) to 920(M) where these couple to first Common Waveguide 960 which is coupled to one end of the Loop Waveguide 960. The Source Array 900A may be passive such that all input wavelengths are coupled to the first Common Waveguide 960 or it may be active wherein a portion of each ring waveguide is electrically controllable, such as Insert 850 in Figure 8, such that which wavelengths of the L(l) to L(M) coupled to Source Array 900A are coupled to first Common Waveguide 960 is configurable.

[0111] The Loop Waveguide 970 is also coupled to second Common Waveguide 980 of the Routing Block 900B which receives those wavelengths coupled to first Common Waveguide 960. Disposed along the second Common Waveguide 980 are N Output Rings 930(1) to 930(N) which couple from the second Common Waveguide 980 to N Output Couplers 940(1) to 940(M) and therein Optical Amplifiers 850(1) to 850(N).

[0112] The Routing Block 900B may be passive such that all input wavelengths that are coupled to the second Common Waveguide 980 which align with a wavelength of an Output Ring of the N Output Rings 930(1) to 930(N) are coupled out of the second Common Waveguide 980. Alternatively, the Routing Block 900B may be active wherein a portion ofeach ring waveguide is electrically controllable, such as Insert 850 in Figure 8, such that which wavelengths of the X(l) to Z(M) coupled to the second Common Waveguide 980 that are coupled from it is configurable such that which wavelength of X(l) to X(M) is coupled to each output X(OP-l) to Z(OP-N) is configurable.

[0113] Within embodiments M and N are positive integers. According to the design of the RRPS 900 M may be less than N, equal to N or greater than N.

[0114] Within RRPS 900 the N Output Rings 930(1) to 930(N), and the M Input Rings 920(1) to 920(M) where Source Array 900A is active, act as optical ring based switch elements and accordingly these may be replaced with other optical switch elements such as tunable CROW filters and tunable MZI filters for example. Similarly, the p-n junction in Insert 850 to exploit the electro-optic effect in the ring waveguides may be replaced with another tuning mechanism such as heaters to exploit the thermo-optic effect to induce optical phase shift within the ring waveguide. Where the Source Array 900A is passive then the M Input Rings 920(1) to 920(M) act as wavelength dependent optical couplers and accordingly these may be replaced with other optical switch elements such as CROW filters, MZI filters, directional couplers, MZIs etc.

[0115] Within embodiments M and N are positive integers. According to the design of the optical network / photonic circuits coupled to the outputs of the RRPS 800 M may be less than N, equal to N or greater than N.

[0116] Referring to Figure 10 there is depicted RRPS 1000 according to an embodiment for use within other embodiments. RRPS 1000 comprising Input Waveguide 1010 coupled to first Optical Drop Router (ODR) 1020(1) which receives X(l) to Z(M) from a MWLS. First ODR 1020(1) drops selected wavelengths from the input coupled to the MWLS to first Drop Waveguide 1040 and the non-dropped wavelengths are coupled to first Output 1030. The first Output 1030 being coupled to second ODR 1020(2) which drops selected wavelengths coupled to the second ODR 1020(2) to second Drop Waveguide 1050 and therein a first output port (O / P 1) and routes the non-dropped wavelengths to second Output 1060 and therein to the second output port (O / P 2). The first Drop Waveguide 1040 is coupled to third ODR 1020(3) which drops selected wavelengths coupled to the third ODR 1020(3) to third Drop Waveguide 1070 and therein a fourth output port (O / P 4) and routes the non-dropped wavelengths to third Output 1080 and therein to the third output port (O / P 3). Each of the outputs O / P 1 to O / P 4 comprising an optical amplifier 1090.

[0117] Each of the first to third ODRs 1020(1), 1020(2) and 1020(3) being an Optical Ring array functioning as an optical drop module which allows for configurable dropping ofwavelengths from an input to generate an output of non-dropped wavelengths and another output of dropped wavelengths. Each Optical Ring array comprising a number of optical ring resonators which as described above in respect of Figure 8 can be electrically controlled to defined wavelengths to drop them or aligned off these defined wavelengths such that the signal pass through. As depicted in Figure 10 first ODR 1020(1) has first to fourth control signals Vn1to Vn4, second ODR 1020(2) has first to fourth control signals V211to V214and third ODR 1020(3) has first to fourth control signals V221to V224.

[0118] As depicted in Figure 10 for RRPS 1000 the number of optical ring resonators within each of the first to third ODRs 1020(1), 1020(2) and 1020(3) is four and if each can cover the full wavelength range of the MWLS then up to 4 wavelengths can be dropped by each of the first to third ODRs 1020(1), 1020(2) and 1020(3) respectively. In this scenario if M=4 for the MWLS then this allows all input wavelengths to be routed to a single output port (O / P 1 to O / P 4) or for them to be distributed between the outputs. If M>8 for the MWLS then the minimum number of wavelengths routable to O / P 2 is M-8 as each of the first ODR(l) and second 0DR(2) can only drop a maximum of 4 wavelengths and the total number of wavelengths to outputs O / P 3 and O / P 4 is a maximum of 4. Rather than a binary tree with two stages that the RRPS 1000 may comprise more stages to provide an increased number of output ports.

[0119] If each optical ring resonator within the first to third ODRs 1020(1), 1020(2) and 1020(3) can only tune over a portion of the wavelength range of the MWLS then the number of wavelengths that each of the first to third ODRs 1020(1), 1020(2) and 1020(3) can only drop is only a portion of the wavelengths from the MWLS where different subsets of the optical ring resonators may select wavelengths within different portions of the wavelength range of the MWLS to cover the full wavelength range of the MWLS or different ODRs may access different portions of the wavelength range of the MWLS.

[0120] Whilst RRPS 1000 is depicted as a symmetric binary tree other configurations of ODRs may be employed including, but not limited to, asymmetric binary trees, linear arrays or combinations thereof.

[0121] Within Figure 10 each ODR is depicted as comprising the same number of optical ring resonators but other embodiments the number of optical ring resonators within each ODR may vary. For example, the number of optical ring resonators within first ODR 1020(1) may be N, the number of optical ring resonators within second ODR 1020(2) may be S and the number of optical ring resonators within third ODR 1020(3) may be T where N, S and T are positive integers. Within embodiments N, S, T and M are positive integers. According to thedesign of the RRPS 1000 M may be less than any of N, S and T, equal to one or more of N, S and T or greater than N, S and T.

[0122] Within RRPS 1000 each of the first to third ODRs 1020(1), 1020(2) and 1020(3) comprises a series of optical ring resonators which act as optical ring based switch elements and accordingly these may be replaced with other optical switch elements such as such as tunable CROW filters and tunable MZI filters for example. In some instances the interconnections for the drop channel to a subsequent optical element may be different if the dropped wavelengths do not counter-propagate relative to the non-dropped channels. Similarly, the p-n junction in Insert 850 to exploit the electro-optic effect in the ring waveguides may be replaced with another tuning mechanism such as heaters to exploit the thermo-optic effect to induce optical phase shift within the ring waveguide.

[0123] Now referring to Figure 11 there is depicted a RRPS 1100 which depicts a reconfigurable laser source according to an embodiment for use within other embodiments. The RRPS 1100 is depicted as having four inputs (I / P 1 to I / P 4) and four outputs (O / P 1 to O / P 4). As depicted the RRPS 1100 comprises a crossbar configuration wherein each input is coupled to a Drop Waveguide 1110 (as a wavelength is dropped from this waveguide) , which each receives an optical wavelength X(l) to X(4), and crosses a number of Add Waveguides 1120 (as a wavelength is added to this waveguide), where each is coupled to an output port via an optional Optical Amplifier 1140. Disposed at the intersection of each Drop Waveguide 1110 and Add Waveguide 1120 is an Optical Ring Resonator 1130 which has an electrical control signal VJJ where I represents the drop row and J the input column such that, for example, to route X(2) from I / P 2 to O / P 4 then the Optical Ring Resonator at the junction of the fourth drop row and second input column is controlled with P42to couple X(2). Similarly, if RRPS 1100 is to be configured to route Z(3) from I / P 3to O / P 4 then the Optical Ring Resonator at the junction of the fourth drop row and third input column is controlled with P43.

[0124] Whilst RRPS 1100 is depicted as an optical crossbar other optical switch configurations may be employed to provide routing of M optical wavelengths to N output ports where M and N are positive integers, which in RRPS 1100 are N=M=4. According to the design of the RRPS 900 M may be less than N, equal to N or greater than N. Such optical switches may include, but not be limited to, those known in the art which are strictly non-blocking, reconfigurably non-blocking and blocking.

[0125] Whilst the RRPS 1100 in Figure 11 depicts single wavelengths being coupled to the Drop Waveguides 1110 in other configurations multiple wavelengths may be coupled to a Drop Waveguide 1110 which may be dropped to multiple Add Waveguides 1120.

[0126] Within RRPS 1100 each of the optical ring resonators act as an optical ring based switch elements and accordingly these may be replaced with other optical switch elements such as tunable CROW filters and tunable MZI filters for example. In some instances the interconnections for the drop channel to a subsequent optical element may be different if the dropped wavelengths do not counter-propagate relative to the non-dropped channels. Similarly, the p-n junction in Insert 850 to exploit the electro-optic effect in the ring waveguides may be replaced with another tuning mechanism such as heaters to exploit the thermo-optic effect to induce optical phase shift within the ring waveguide.

[0127] Referring to Figure 12A there is depicted a RRPS 1200A which depicts a reconfigurable laser source according to an embodiment for use within other embodiments. The RRPS 1200A depicted in Figure 12 is presented with a 4 wavelength comb comprising wavelengths X(1 ), X(2), Z(3) and X(4).

[0128] The RRPS 1200A is depicted as having an Input Wavelength Interleaver 1210 coupled to a MWLS such that it receives multiple wavelengths in a comb from the MWLS. A first output of the First Stage Wavelength Interleaver 1210 is coupled to a first First Stage Wavelength Selective Switch (WSS) 1220(1) and a second output of the second First Stage Wavelength Interleaver 1210 is coupled to a second WSS 1220(2). Each of the first and second WSSs 1220(1) and 1220(2) receive secondary combs of wavelengths from the first Wavelength Interleaver 1210 at double the wavelength spacing of the comb of the MWLS and route different wavelengths within the received comb to outputs of the WSS.

[0129] A wavelength interleaver may receive optical signals upon a grid of spacing X GHz, for example upon a 100 GHz, 200 GHz, 400 GHz grid, and splits them into two streams where each stream is upon a grid at 2X GHz, e.g. 100 GHz input grid is split into 2 200 GHz grids with the two outputs offset by 100 GHz. Alternatively, a wavelength interleaver may provide or generate two streams of optical signals upon a grid of spacing X GHz, for example upon a 100 GHz, 200 GHz, 400 GHz grid, and combine them a single stream at 2X GHz where each input stream is offset from the other by X GHz. For example, 2 200GHz input streams offset by 100 GHz are combined to a single 100 GHz output grid.

[0130] As depicted in RRPS 1200A first First Stage WSS 1220(1) is coupled to first and second Second Stage WSSs 1230(1) and 1230(2) whilst second First Stage WSS 1220(2) is coupled to first and second Second Stage WSSs 1230(3) and 1230(4) respectively. EachSecond Stage WSS 1230 routes different wavelengths within the received comb from the First Stage WSS 1220 to outputs of the Second Stage WSS 1230. The outputs of each Second Stage WSS 1230 are coupled to a subset of first to fourth Output Wavelength Interleavers 1240(1) to 1240(4). For example, the outputs of first Second Stage WSS 1230(1) are coupled to first and third Output Wavelength Interleavers 1240(1) and 1240(3) and the outputs of second Second Stage WSS 1230(2) are coupled to second and fourth Output Wavelength Interleavers 1240(2) and 1240(4). The outputs of each Output Wavelength Interleaver 1240 being coupled to an output via an optional Optical Amplifier 1250.

[0131] Whilst RRPS 1200A provides for generating a number of outputs with defined wavelengths from an MWLS input it has limited reconfiguration as, for example, X(l) is routed via Input Wavelength Interleaver 1210, first First Stage WSS 1220(1) and first Second Stage WSS 1230(1) such that it can only be routed to either first or third Output Wavelength Interleavers 1240(1) to 1240(3). However, if each First Stage WSS 1220 can be tuned so that its outputs swap then X(l) would be routed to second Second Stage WSS 1230(2) such that it can be routed to either second or fourth Output Wavelength Interleavers 1240(2) to 1240(4) but the routing of Z(3) is still constrained such that RRPS 1200A is a blocking RRPS. Similarly tuning of the Input Wavelength Interleaver 1210 may be implemented.

[0132] Optionally, as depicted in Figure 12B an RRPS 1200B is depicted wherein the Second Stage WSSs 1230 are replaced with Stage 2 WSSs 1260(1) to 1260(4) respectively and Output Wavelength Interleavers 1240 are replaced with Wavelength Combiners 1270(1) to 1270(4) respectively such that each Stage 2 WSS can connect to any Wavelength Combiner 1270 of the first to fourth Wavelength Combiners 1270(1) to 1270(4) then the RRPS 1200B is strictly non-blocking as now any wavelength can be routed to any output via the shuffle between the Stage 2 WSSs 1260 and Wavelength Combiners 1270. Optionally other interconnections may be employed comprising Stage 2 WSSs 1260 and Wavelength Combiners 1270 which are strictly non-blocking, reconfigurably non-blocking and blocking.

[0133] The RRPS architectures depicted within Figures 12A and 12B can be generalized to a number N wavelengths where N is a positive integer. Within embodiments the architectures depicted within Figures 8 and 10 may be employed as WSS elements within the RRPS 1200A and 1200B. Similarly, the architecture in Figure 9 may be employed if a wavelength division demultiplexer is disposed prior to the inputs to demultiplex the input wavelength comb. Accordingly, the elements within a WSS may be implemented using optical ring resonators, MZIs, ring-assisted MZIs etc.

[0134] Within embodiments the Input Wavelength Interleaver 1210 and / or the Output Wavelength Interleavers 1240 may be implemented using optical ring resonators, MZIs, ring- assisted MZIs etc. as well as via optical waveguide implementations of free-space optical interleavers for a monolithic implementation of an RRPS although within other embodiments hybrid integration may be employed to incorporate one or more micro-optic elements within a guide wave photonic circuit.

[0135] Now referring to Figure 13 there is depicted a node interconnection configuration (NIC) 1300 according to an embodiment employing a wavelength selective laser (WSL) bank. WSL Bank 1310, a Compute Node Array 1320 and a Wavelength Selective Router (WSR) 1330. The WSL Bank 1310 comprises first to M WSLs 1315(1) to 1315(M) respectively which are connected via an Interface 1340 to the Compute Node Array 1320 comprising first to M Compute Nodes 1325(1) to 1325(M), where each WSL within the WSL Bank 1310 is connected directly to a single node of the Compute Node Array 1320. Each Compute Node receives the output of its associated WSL and encodes data the Compute Node wishes to transmit to other Compute Nodes on the wavelengths received from the associated WSL. A TX port of each Compute Node is coupled to an input port of the MxM port WSR 1330 which then routes the wavelengths received from a node to the receiving Compute Node or Compute Nodes which are coupled via a RX port to an output port of the WSR 1330.

[0136] Accordingly, in contrast to the general topology 100A of the photonic switch for a computer cluster exploiting a remote reconfigurable photonic source and wavelength selective router in Figure 1A, the NIC eliminates fixed wavelength sources and the switching network to generate the wavelength coupled to each Compute Node and replacement them with an array of WSLs. Each WSL may generate one, two or more wavelengths which are coupled to its associated Compute Node, encoded with data and then routed by the WSR to one or more other Compute Nodes.

[0137] If a Compute Node wishes to broadcast it can request its associated WSL generate all M wavelength and then encode each with the same data. Alternatively, a Compute Node may receive X wavelengths where 2 < X < M and encode data specific for each Compute Node of the X Compute Nodes receiving data upon the appropriate wavelength requested from its WSL. Optionally, each WSL and its associated Node may be co-located. Optionally, the WSL Bank 1310 may be a number of WSL Banks each comprising a subset of the first to M WSLs 1315(1) to 1315(M) respectively. Similarly, the Compute Node Array 1320 may be a number of Compute Node Arrays each comprising a subset of the first to M Compute Nodes 1325(1) to 1325(M). The WSR 1330 may be centralized or distributed.

[0138] Within some configurations the wavelengths generated by a first subset of the first to M WSLs 1315(1) to 1315(M) respectively may be a subset of the wavelengths supported by the WSR 1330 such that some Compute Nodes can only communicate via the WSR 1330 with a subset of the other Compute Nodes.

[0139] Referring to Figure 14 there is depicted a configuration for a WSL Bank 1400 employing micro-ring resonators supporting a node interconnection configuration such as depicted in Figure 13. Within a configuration such as depicted by NIC 1300 in Figure 1300 the WSL Bank 1400 may replace subset of the first to M WSLs 1315(1) to 1315(M) respectively where this subset of the first to M WSLs 1315(1) to 1315(M) respectively may be co-located or spatially associated. WSL Bank 1400 comprising a Multi-Wavelength Source (MLS) 1410 which is coupled to a LN Splitter 1420. Each output of the LN Splitter 1420 is coupled to a defined Wavelength Filter Array (WFA) of the N WFAs 1430(1) to 1430(N).

[0140] Within another configuration two or more MLS 1410 each generating different subsets of the overall wavelength set configured by the set of WFAs 1430(1) to 1430(N) respectively wherein the LN Splitter 1420 becomes an R:N splitter where R is the number of MLS 1410. Alternatively, the WSL Bank 1400 may be one of a set of WSL Banks where each WSL Bank is coupled to a subset of the other elements, such as a subset of the first to M Compute Nodes 1325(1) to 1325(M) respectively in NIC 1300.

[0141] Each WFA of the set of WFAs 1430(1) to 1430(N) respectively comprises a linear array of M Micro-Ring Resonator Filters (MMRFs) 1440(1) to 1440(M) respectively where each MMRF of the M Micro-Ring Resonator Filters (MMRFs) 1440(1) to 1440(M) is employed to select which wavelength of the M wavelengths from the MLS 1410 wherein the selected wavelengths are amplified by an Optical Amplifier (OA) 1450 before propagating to the subsequent elements of the system the WSL Bank 1400 forms part of. Each of the M MicroRing Resonator Filters (MMRFs) 1440(1) to 1440(M) is controlled via one or more control line V(l) to V(M) such that a selected MMRF is detuned so as to not couple the associated wavelength to the OA 1450 and therein on to the system. Within other embodiments the MMRFs may be tuned to couple a selected wavelength from an input waveguide to an output waveguide disposed on the other side of the MMRF wherein the OA 1450 is disposed on the output waveguide, such a design being similar to that depicted within Figure 10 with first to third ODR 1020(1) to 1020(3) respectively. Within other configurations the filter elements, depicted as MMRFs, may be tunable Brag gratings, Mach-Zehnder interferometers, coupled ring resonators etc.

[0142] Now referring to Figure 15 there is depicted a multi-path communications network (MPC-Network) 1500 exploiting reconfigurable laser banks with multiple sub-networks in an exemplary configuration. As depicted first to fourth Nodes 1500A to 1500D are depicted together with first and second Sub-Nets 1500E and 1500F respectively. The first Sub-Net 1500E comprising first Remote Laser Bank (RLB) 1550E and first Router 1560E whilst second Sub-Net 1500F comprising second RLB 1550F and second Router 1560F. Each of the first to fourth Nodes 1500A to 1500D comprises a pair of first transmit-receive (TRX) modules 1510 on one side of a Processor (xPU) 1570 away from the first and second Sub-Nets 1500E and 1500F respectively and a pair of second TRX modules 1520 on another side of the xPU 1570 towards the first and second Sub-Nets 1500E and 1500F respectively.

[0143] Each of the first and second RLBs 1550E and 1550F within each of the first and second Sub-Nets 1500E and 1500F respectively are coupled to a port on each of the pair of first TRX modules 1520 in the first and fourth Nodes 1500A and 500D respectively and a port of each of the pair of second TRX modules 1520 in the second and third Nodes 1500B and 1500C respectively.

[0144] Each of the first and second Routers 1560E and 1560F within each of the first and second Sub-Nets 1500E and 1500F respectively are coupled to another port on each of the pair of first TRX modules 1520 in the first and fourth Nodes 1500A and 500D respectively and another port of each of the pair of second TRX modules 1520 in the second and third Nodes 1500B and 1500C respectively.

[0145] Each of first and second Routers 1560E and 1560F being a wavelength router (WR). Each Node of the first to fourth Nodes 1500A to 1500D is connected to the RLBs within the first and second Sub-Nets 1500E and 1500F such that they receive wavelengths from each of the first and second RLBs 1550E and 1550F and transmit data to the Routers within the first and second Sub-Nets 1500E and 1500F upon the wavelengths received from the RLBs. Accordingly, each node of the first to fourth Nodes 1500A to 1500D respectfully thereby transmits data to other nodes of the first to fourth Nodes 1500A to 1500D respectfully via the first and second Sub-Nets 1500E and 1500F respectively.

[0146] Within some configurations of the MPC-Network 1500 the first and second Sub-Nets 1500E and 1500F may have the same port configuration whilst using different wavelengths for different TRXs in the same node. Accordingly, as depicted in Figure 15 multiple sub-nets are employed through multiple spatial paths or spatial - wavelength division multiplexing to increase the overall bandwidth of the network without increasing the number of wavelength channels overall.

[0147] Referring to Figure 16 there is depicted a multi-path communications network (MPC- Network) exploiting reconfigurable laser banks with multiple sub-networks. As depicted MLC- Network 1600 comprises first to fourth Nodes 1500A to 1500D respectively, which are configured in the same manner as depicted in Figure 15. Rather than first and second Sub-Nets 1500E and 1500F respectively MPC-Network 1600 interconnects the first to fourth Nodes 1500A to 1500D respectively via first and second Routers 1620A and 1620B respectively wherein the optical sources coupled to each of the first to fourth Nodes 1500A to 1500D respectively for providing the appropriate wavelengths to them are generated by RLB 1630 where Splitters 1610 are disposed on the RLB 1610 to split them to the nodes.

[0148] Accordingly, in this configuration the first and second Sub-Nets 1500E and 1500F rather than employing different RLBs per sub-net employ a common RLB. Accordingly, 1 & Sub-net 2 may have different port configurations, whilst using the same optical sources within the RLB allowing for many-to-many, many-to-one, or one-to-many collective operations; e.g., Sub-Net 1 connecting node 1-2, 2-3, 3-4, and 4-1 and Sub-Net 2 connecting node 1-3, 2-4, 3- 1, and 4-2, such that collective operation can be performed (4, 1)-1, (1, 4)-2, (2, l)-3, (3, 2)-4. Additional subsets can be added by increasing the number of TRX modules within a node or nodes and thus the number of sub-nets.

[0149] Within other configurations tunable optical filters may be implemented on the receiver side of the TRXs of each node. The sub-nets may be implemented using different methodologies, such as broadcast and select using optical gates (e.g. semiconductor optical amplifier (SOA) gates) that can be integrated either within the wavelength routers or TRX receivers.

[0150] The remote reconfigurable laser enabled optical cross-connect switch (OCS) outlined may be employed discretely or it may be hybrid integrated with one or more other types of OCS, such as path-switching components such as MEMS, liquid crystal switches etc., as well as electrical switches, for a larger hierarchical network or to flatten the network.

[0151] Whilst Figures 15 and 16 depict a single RLB within each sub-net or a common RLB to both sub-nets this RLB may be one of a number of RLBs (either tunable or fixed in wavelength) which may be employed to at least one of cover a broader spectral range and thus increase the number of wavelength channels and support an increase in the number of sub-nets for broader-band connectivity and / or more complex collective operations.

[0152] Specific details are given in the above description to provide a thorough understanding of the embodiments. However, it is understood that the embodiments may be practiced without these specific details. For example, circuits may be shown in block diagrams in order not toobscure the embodiments in unnecessary detail. In other instances, well-known circuits, processes, algorithms, structures, and techniques may be shown without unnecessary detail in order to avoid obscuring the embodiments.

[0153] The foregoing disclosure of the exemplary embodiments has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many variations and modifications of the embodiments described herein will be evident in light of the above disclosure. The scope of the invention is to be defined only by the claims appended hereto, and by their equivalents.

[0154] Further, in describing representative embodiments, the specification may have presented the method and / or process of the present invention as a particular sequence of steps. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the specification should not be construed as limitations on the claims. In addition, the claims directed to the method and / or process of the present invention should not be limited to the performance of their steps in the order written, and one skilled in the art can readily appreciate that the sequences may be varied and still remain within the spirit and scope of the present invention.

Claims

CLAIMSWhat is claimed is:

1. A system comprising: a plurality of M nodes; an optical emitter generating continuous wave (CW) or pulsed optical signals at a plurality of N wavelengths and an NxM optical switch where each output of the M outputs of the NxM switch is optically connected to an input port of a predetermined node of the plurality of M nodes; an at least MxM wavelength dependent router wherein each input of the M inputs of the at least MxM wavelength dependent router is coupled to an output port of another predetermined node of the plurality of M nodes and each output of the M outputs of the at least MxM router is coupled to another input port of a further predetermined node of the plurality of M nodes; wherein each node of the plurality of M nodes encodes data onto the CW or pulsed optical signals it receives from the optical emitter; the wavelength of the N wavelengths coupled to each node of the plurality of M nodes is established in dependence upon a routing configuration of the at least MxM wavelength dependent router and which other node of the plurality of M nodes the node of the plurality of M nodes is to transmit data to; andN and M are each positive integers greater than or equal to 2.

2. The system according to claim 1, wherein an NxM optical switch reconfigures the wavelengths coupled to each node of the plurality of M nodes upon a change of a destination of data from at least one node of the plurality of M nodes.

3. A system comprising: a plurality of M nodes; an optical emitter generating continuous wave (CW) or pulsed optical signals at a plurality of N wavelengths and at least aNx2M optical switch where each output of a first set of M outputs of the Nx2M switch is optically connected to an input port of a predetermined node of the plurality of M nodes and each output of a second set of M outputs of the atleast a Nx2M switch is optically connected to an input port of a coherent receiver forming part of a different predetermined node of the plurality of M nodes; an at least MxM wavelength dependent router wherein each input of the M inputs of the at least MxM wavelength dependent router is coupled to an output port of another predetermined node of the plurality of M nodes and each output of the M outputs of the MxM router is coupled to another input port of a further predetermined node of the plurality of M nodes; wherein each node of the plurality of M nodes incorporates a coherent transmitter to encode data onto the CW or pulsed optical signals it receives from the optical emitter where the wavelength of the N wavelengths coupled to that node of the plurality of M nodes is established in dependence upon a routing configuration of the at least MxM wavelength dependent router and which other node of the plurality of M nodes the node of the plurality of M nodes is to transmit data to;N and M are each positive integers greater than or equal to 2; each node of the plurality of nodes incorporates the coherent receiver which receives the encoded optical signal from the at least MxM wavelength dependent router of the node of the plurality of M nodes transmitting data to it at the wavelength of the N wavelengths coupled to that node of the plurality of M nodes and a CW or pulsed optical signals at the wavelength of the N wavelengths coupled to it directly from the at least Nx2M router.

4. The system according to claim 3, wherein an Nx2M optical switch reconfigures the wavelengths coupled to each node of the plurality of M nodes upon a change of a destination of data from at least one node of the plurality of M nodes.

5. A system comprising: a coherent photonic interposer (CPI) comprising a number N coherent photonic interposer circuits (CPICs); andN coherent electronic integrated circuits (CEIC) where each CEIC is electrically coupled to a defined CPIC of the N CPICs; wherein each CEIC receives: data for transmission from an electronic circuit of a set of electronic circuits and provides other data and control signals for the associated CPIC to coherentlymodulate a continuous wave (CW) or pulsed optical signals coupled to the associated CPIC; and a set of electrical signals from a coherent receiver forming part of the associated CPIC to generate further data for transmission to another electronic circuit of the set of electronic circuits from the set of electrical signals where the CEIC provides other control signals to the associated CPIC to coherently detect another coherently modulated optical signal received by the CPIC; each CPIC receives: the CW or pulsed optical signals which are at a predetermined wavelength together with the other data and control signals from the CEIC associated with the CPIC and encodes the other data onto the CW or pulsed optical signals to generate a coherently modulated optical signal which is transmitted from the CPIC; and the another coherently modulated optical signal at another predetermined wavelength which is coherently detected to generate the set of electrical signals provided to the associated CEIC by a coherent receiver circuit which receives the other control signals from the associated CEIC and a CW or pulsed optical signals which is at the another predetermined wavelength; andN is an integer greater than or equal to 1.

6. The system according to claim 5, wherein the predetermined wavelength and another predetermined wavelength are at the same wavelength.

7. The system according to claim 5, wherein the predetermined wavelength and another predetermined wavelength are at different wavelengths.

8. The system according to claim 5, wherein at least one of: a subset of the N CEICs are hybridly integrated upon the CPI; another subset of the N CEICs are monolithically integrated in the CPI; a further subset of the N CEIC have a first part of each CEIC hybridly integrated upon the CPI and a second part of each CEIC monolithically integrated in the CPI.

9. The system according to claim 5, wherein the another coherently modulated optical signal is received from another CPIC which is another CPIC of the N CPICs upon the same CPI as the CPIC of the N CPICs receiving the another coherently modulated optical signal; and the CW or pulsed optical signals at the another predetermined wavelength and the CW optical signal are received from a laser source which is common to a defined subset of the N CPICs.

10. The system according to claim 5, wherein the another coherently modulated optical signal is received from another CPIC which is a CPIC of another M CPICs upon a different CPI; the CW optical signal at the another predetermined wavelength and the CW optical signal are received from a laser source which is common to a defined subset of the N CPICs; andM is an integer greater than or equal to 1.

11. The system according to claim 5, wherein the CPI comprising the N CPICs, the N CEICs electrically coupled to the N CPICs and the set of electronic circuits comprises a first system of a set of system; each other system of the set of systems comprises another CPI with an integer M CPICs, M CEICs electrically coupled to the M CPICs and another set of electronic circuits; each system of the set of systems is coupled to a predefined subset of the set of systems via an optical fiber array interface; andM is an integer greater than or equal to 1.

12. A system comprising: a waveguide coupled to an input for receiving a number M optical signals at a number of M wavelengths; along the waveguide a number N wavelength tunable couplers where each wavelength tunable coupler is tunable over a defined wavelength range such that the wavelength tunable coupler can be tuned to either couple a defined optical signal of the M optical signals from the waveguide to an output port or not couple any optical signal of the M optical signals from the waveguide; whereinN and M are positive integers.

13. The system according to claim 12, wherein each wavelength tunable coupler is an optical ring resonator optically coupled to the waveguide which is electrically tunable and a coupler optically coupled to the optical resonator and the output port.

14. The system according to claim 12, further comprising: another waveguide coupled to the waveguide to provide the number M optical signals at the number of M wavelengths; along the another waveguide a number M other wavelength tunable couplers where each wavelength tunable coupler is tunable over a defined wavelength range such that the wavelength tunable coupler can be tuned to either couple an optical signal at a wavelength of the number of M wavelengths to the another waveguide from an input port or not couple the optical signal at the wavelength of the number of M wavelengths to the another waveguide.

15. The system according to claim 14, wherein each other wavelength tunable coupler is an other optical ring resonator optically coupled to the another waveguide which is electrically tunable and an other coupler optically coupled to the optical resonator and an input port; and the input of the waveguide and the output of the other waveguide as one of directly coupled, coupled via an optical waveguide and coupled via optical fiber.

16. The system according to claim 12, wherein the output port is another waveguide which extends along the number N wavelength tunable couplers; and any optical signals of the M optical signals coupled from the waveguide are coupled to the another waveguide.

17. The system according to claim 16, wherein the waveguide, the another waveguide and the number N wavelength tunable couplers form an optical drop router (ODR) circuit; the wavelength drop circuit is coupled to another ODR circuit and a further ODR;an end of the waveguide coupled distal to that coupled to the input is coupled to the another wavelength drop circuit which comprises a number S other wavelength tunable couplers; an end of the another waveguide in a propagation direction of optical signals of the M optical signals coupled from the waveguide is coupled to the further wavelength drop circuit which comprises a number T further wavelength tunable couplers; andS and T are positive integers.

18. The system according to claim 12, wherein the waveguide and the number N wavelength tunable couplers form an optical circuit of a number of optical circuits; the output port of each wavelength tunable coupler of the N wavelength tunable couplers is an other waveguide of a number N other waveguides where the N other waveguides are common to the number of optical circuits such that each optical signal dropped from the waveguide of an optical circuit of the number of optical circuits via a wavelength tunable coupler of the N wavelength tunable couplers within that optical circuit of the number of optical circuits is added to an other waveguide of the N other waveguides.

19. A system comprising: an input optical interleaver to deinterleave an input optical signal comprising a number of optical signals upon a defined grid of spacing X GHz into two output optical signals where each output of the input optical interleaver comprises optical signals upon a grid of spacing 2X GHz and the two output optical signals are offset relative to one another by X GHz; a pair of first wavelength selective switches (WSSs) where each first WSS is coupled to an output of the optical interleaver; a number of second WSSs where each second WSS is connected to a defined output of a defined first WSS of the pair of WSSs; and a number of output optical interleavers to interleave input optical signals to an output optical signal where each input to a defined output optical interleaver of the number of output optical interleavers comprises optical signals from a defined second WSS of the number of second WSSs upon the grid of spacing 2X GHz and the output of each output optical interleaver of the number of output optical interleavers comprises optical signals upon the defined grid of X GHz spacing; wherein X is positive.

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