Optically coupled multi-node computing system

Abstract

An apparatus includes a plurality of nodes coupled to an optical network, each node including an optical transmitter interface configured to transmit optical signals at locations along a coupled optical path of the optical network and an optical receiver interface configured to receive optical signals at locations along the coupled optical path of the optical network. The apparatus includes a first optical path of the optical network configured to propagate a guided mode around a closed path and a second optical path of the optical network configured to propagate a guided mode around the closed path. The first optical path and the second optical path overlap each other at a first set of four locations, the first optical path is coupled to two or more of the nodes at a second set of respective locations different from the locations in the first set of locations, and the second optical path is coupled to two or more of the nodes at a third set of respective locations different from all of the locations in the first set of locations and the second set of locations.

Description

Technical Field

[0001] This disclosure relates to an optically coupled multi-node computing system. Background Technology

[0002] Optical signals have been used to transmit data over both long and short distances, including within data centers and individual optical devices. An example of an optical network within a device is an optical network on a chip (ONoC). There are also various optical network topologies used to connect system nodes. Summary of the Invention

[0003] In general, an apparatus includes: an integrated circuit comprising a plurality of nodes coupled to an optical network, each node including: an optical transmitter interface configured to transmit an optical signal at a location along a coupled optical path of the optical network; and an optical receiver interface configured to receive an optical signal at a location along the coupled optical path of the optical network. The apparatus includes: a first optical path of the optical network including at least a portion of a guided mode fabricated in at least one layer of the integrated circuit and configured to propagate a guided mode around a closed path; and a second optical path of the optical network including at least a portion of a guided mode fabricated in at least one layer of the integrated circuit and configured to propagate a guided mode around a closed path. The first and second optical paths overlap each other at a first set of four locations on the integrated circuit. The first optical path is coupled to two or more of the plurality of nodes at a second set of corresponding locations on the integrated circuit, different from all locations in the first set of locations. The second optical path is coupled to two or more of the plurality of nodes at a third set of corresponding locations on the integrated circuit, different from all locations in the first and second sets of locations.

[0004] The implementation may include one or more of the following features. The first optical path may include at least a first straight segment and a second straight segment parallel to each other, wherein at least one of a plurality of nodes is coupled along the first straight segment at two or more locations in the second group, and at least one of the plurality of nodes is coupled along the second straight segment at two or more locations in the second group.

[0005] The first optical path and the second optical path can overlap each other at the four positions in the first group without switching the optical signal between the first optical path and the second optical path at any of the four positions in the first group.

[0006] At at least one of the four locations in the first group, a portion of the first optical path in the first layer of the integrated circuit may overlap with a portion of the second optical path in the second layer of the integrated circuit.

[0007] At at least one location on the integrated circuit, a portion of the second optical path may be in the first layer of the integrated circuit.

[0008] At least one of the plurality of nodes may be coupled to the first optical path at one or more locations in the second set of locations, and coupled to the second optical path at one or more locations in the third set of locations.

[0009] The first optical path and the second optical path may overlap each other, wherein at least one switch is configured to switch optical signals between the first optical path and the second optical path at at least one of the four positions in the first group.

[0010] The first optical path and the second optical path can be fabricated in the same layer of the integrated circuit.

[0011] The switch may include at least two waveguide ring resonators located near one of the four positions in the first group where the first and second optical paths overlap.

[0012] The device may further include: a third optical path of the optical network, the third optical path comprising at least a portion of a guided mode fabricated in at least one layer of the integrated circuit and configured to propagate a guided mode around a closed path; and a fourth optical path of the optical network, the fourth optical path comprising at least a portion of a guided mode fabricated in at least one layer of the integrated circuit and configured to propagate a guided mode around a closed path. The third and fourth optical paths may overlap each other at four locations in a fourth group on the integrated circuit. The third optical path is coupled to two or more nodes in a fifth group of locations on the integrated circuit, different from all locations in the first, second, third, and fourth groups of locations. The fourth optical path is coupled to two or more nodes in a sixth group of locations on the integrated circuit, different from all locations in the first, second, third, fourth, and fifth groups of locations.

[0013] The integrated circuit may be a first integrated circuit, and the device may include a second integrated circuit, which includes multiple nodes coupled to an optical network.

[0014] The first optical path of the optical network may include at least a portion fabricated in at least one layer of the second integrated circuit.

[0015] The device may include a third integrated circuit comprising multiple nodes coupled to an optical network.

[0016] The second optical path of the optical network may include at least a portion fabricated in at least one layer of the third integrated circuit.

[0017] At least one of the plurality of nodes coupled to the first optical path can be configured to transmit an optical signal using a first optical wavelength, and at least one of the plurality of nodes coupled to the first optical path can be configured to transmit an optical signal using a second optical wavelength different from the first optical wavelength.

[0018] The device may include a controller configured to schedule the transmission of optical signals between the nodes, wherein the controller may be configured to set the first node as a transmitter during a first time period and prevent other nodes from transmitting signals on the optical path coupled to the first node during the first time period.

[0019] Each of at least some of these nodes may include at least one of a central processing unit, a graphics processing unit, a tensor processing unit, a digital signal processor, or a matrix processor.

[0020] In another general aspect, an apparatus includes: a plurality of nodes coupled to an optical network, each node including: an optical transmitter interface configured to transmit an optical signal at a location along a coupled optical path of the optical network; and an optical receiver interface configured to receive an optical signal at a location along the coupled optical path of the optical network. The apparatus includes: a first optical path of the optical network configured to propagate a guided pattern around a closed path; and a second optical path of the optical network configured to propagate the guided pattern around a closed path. The first and second optical paths may overlap each other at a first set of four locations, the first optical path may couple to two or more nodes in the node at a second set of corresponding locations different from those in the first set of locations, and the second optical path may couple to two or more nodes in the node at a third set of corresponding locations different from all locations in the first and second sets of locations.

[0021] The first optical path and the second optical path can overlap each other at the four positions in the first group without switching the optical signal between the first optical path and the second optical path at any of the four positions in the first group.

[0022] The first optical path and the second optical path may overlap each other, wherein at least one switch is configured to switch optical signals between the first optical path and the second optical path at at least one of the four positions in the first group.

[0023] The nodes, the first optical path, and the second optical path can be set on a single substrate.

[0024] At least some of these nodes may include integrated circuits.

[0025] The device may include an integrated circuit, wherein the node is part of the integrated circuit.

[0026] The first and second optical paths may include planar waveguides formed on a single substrate.

[0027] The first subgroup of the node, the first portion of the first optical path, and the first portion of the second optical path can be disposed on the first substrate. The second subgroup of the node, the second portion of the first optical path, and the second portion of the second optical path can be disposed on the second substrate.

[0028] At least a portion of the first optical path may include a planar waveguide formed on the substrate.

[0029] At least a portion of the second optical path may include a planar waveguide formed on the substrate.

[0030] In another general aspect, an apparatus includes: an array of nodes; and an optical network including a first optical path and a second optical path. The first optical path is configured to propagate a guiding pattern around a first closed path and is optically coupled to a plurality of nodes in the array. The second optical path is configured to propagate a guiding pattern around a second closed path and is optically coupled to a plurality of nodes in the array. The optical network is configured such that no switch is provided between the first and second optical paths, such that an optical signal traveling in the first optical path remains in the first optical path without being switched to the second optical path, and an optical signal traveling in the second optical path remains in the second optical path without being switched to the first optical path. The apparatus includes a controller configured to schedule the transmission of optical signals between the nodes through the optical network.

[0031] The implementation may include one or more of the following features: the first optical path can be optically coupled to all nodes in the array, and the second optical path can be optically coupled to all nodes in the array.

[0032] The controller can be configured to set a first node as a transmitter during a first time period, the first node can be configured to transmit optical signals on the first optical path during the first time period, and the controller can be configured to prevent other nodes from transmitting signals on the first optical path during the first time period.

[0033] The controller can be configured to set a second node as a transmitter during the first time period, the second node can be configured to transmit optical signals on the second optical path during the first time period, and the controller can be configured to prevent other nodes from transmitting signals on the second optical path during the first time period.

[0034] The array of nodes may include node rows and node columns. The first optical path may include one or more waveguide segments extending in the row direction and optically coupled to the plurality of nodes, and the second optical path may include one or more waveguide segments extending in the column direction and optically coupled to the plurality of nodes.

[0035] The first optical path may include a waveguide segment located between the nodes in the Nth and (N+1)th rows, and may be optically coupled to all nodes in the Nth and (N+1)th rows, where N is an integer equal to or greater than 1.

[0036] The second optical path may include a waveguide segment located between the nodes in column M and column (M+1) and optically coupled to all nodes in column M and column (M+1), where M is an integer equal to or greater than 1.

[0037] Each of at least some of these nodes may include at least one of a central processing unit, a graphics processing unit, a tensor processing unit, a digital signal processor, or a matrix processor.

[0038] In another general aspect, an apparatus includes: a plurality of nodes; and an optical network including a first optical path and a second optical path. The first optical path is configured to propagate a guiding pattern around a first closed path and is optically coupled to the plurality of nodes in an array. The second optical path is configured to propagate a guiding pattern around a second closed path and is optically coupled to the plurality of nodes in the array. The first and second optical paths overlap each other at at least two locations in a first set, the first optical path couples to two or more nodes in the array at corresponding locations in a second set different from those in the first set, and the second optical path couples to two or more nodes in the array at corresponding locations in a third set different from all locations in the first and second sets.

[0039] The implementation may include one or more of the following features. The device may include a controller configured to schedule the transmission of optical signals between nodes through the optical network. The controller may be configured to set a first node as a transmitter during a first time period and to set a first switch to a pass or switch state. The first node may be configured to transmit optical signals via the first switch through the first optical path during the first time period, and the controller may be configured to prevent other nodes from transmitting signals on the first optical path during the first time period.

[0040] The first node can be configured to transmit an optical signal at a first wavelength around the first optical path in a first direction, and at least one node coupled to the optical network can be configured to couple substantially all remaining optical power at the first wavelength from the first optical path to prevent interference with the optical signal at the first wavelength transmitted by the first node.

[0041] The first node may include an optical transmitter interface and an optical receiver interface. The optical transmitter interface may be configured to transmit a first optical signal at a first wavelength along a portion of a first closed path, and to transmit a second optical signal at a second wavelength along a portion of the first closed path. The optical receiver interface may be configured to receive an optical signal at a third wavelength from a location along the first closed path.

[0042] The second node may include an optical transmitter interface and an optical receiver interface. The optical transmitter interface may be configured to transmit an optical signal at the third wavelength along a portion of the first closed path, and is also configured to transmit an optical signal at the second wavelength along a portion of the first closed path. The optical receiver interface may be configured to receive an optical signal at the first wavelength from a location along the first closed path.

[0043] The third node may include an optical transmitter interface and an optical receiver interface. The optical transmitter interface may be configured to transmit an optical signal at the first wavelength onto the first closed path, and may also be configured to transmit an optical signal at the third wavelength onto the first closed path. The optical receiver interface may be configured to receive an optical signal at the second wavelength from a location along the first closed path.

[0044] The plurality of nodes may include at least a first node, a second node, and a third node coupled to the first closed path. The plurality of nodes may be configured to communicate using a plurality of wavelengths, including at least a first wavelength, a second wavelength, and a third wavelength, on the first optical network.

[0045] The first node may include: an optical transmitter interface configured to transmit a first optical signal at the first wavelength onto the first closed path; an optical receiver interface configured to simultaneously detect a second optical signal at a second wavelength and a third optical signal at a third wavelength from the first closed path; and demodulation circuitry coupled to the optical receiver interface of the first node. The demodulation circuitry may be configured to determine, for multiple time slots, a mapping between multiple amplitude levels detected during those time slots and binary symbols modulated onto each of the second and third optical signals.

[0046] The second node may include: an optical transmitter interface configured to transmit the second optical signal onto the first closed path; an optical receiver interface configured to simultaneously detect multiple optical signals at wavelengths different from the second wavelength from the first closed path; and demodulation circuitry coupled to the optical receiver interface of the second node. The demodulation circuitry may be configured, for multiple time slots, to determine a mapping between multiple amplitude levels detected during that time slot and binary symbols modulated onto each of the multiple optical signals detected by the optical receiver interface of the second node.

[0047] In another general aspect, an apparatus includes: an array of nodes; and an optical network including a first optical loop and a second optical loop, wherein the first optical loop is optically coupled to all nodes in the array, and the second optical loop is optically coupled to all nodes in the array. The apparatus includes a controller configured to schedule the transmission of optical signals between the nodes through the optical network. The controller is configured to allow only one node to broadcast an optical signal through the first optical loop during a first time period, and to prevent other nodes from transmitting optical signals through the first optical loop during the first time period; to allow only one node to broadcast an optical signal through the second optical loop during a second time period, and to prevent other nodes from transmitting optical signals through the second optical loop during the second time period.

[0048] The controller can be configured to schedule the first node and the second node to communicate with each other through the first optical loop during the third time period, schedule the third node and the fourth node to communicate with each other through the second optical loop during the third time period, and prevent other nodes from sending optical signals on the first optical loop and the second optical loop during the third time period.

[0049] For example, no switch is provided between the first and second optical loops, such that an optical signal traveling in the first optical loop remains in the first optical loop without being switched to the second optical loop, and an optical signal traveling in the second optical loop remains in the second optical loop without being switched to the first optical loop; and the optical signal is transmitted between nodes through the optical network.

[0050] Each node may include: an optical transmitter interface configured to transmit an optical signal at a first location along a first optical loop or a second optical loop; and an optical receiver interface configured to receive an optical signal at a second location along the first optical loop or the second optical loop. The first and second optical loops may overlap each other at a first set of four locations, the first optical loop may couple to two or more nodes at a second set of corresponding locations different from all locations in the first set, and the second optical loop may couple to two or more nodes at a third set of corresponding locations different from all locations in the first and second sets.

[0051] Each of at least some of these nodes may include at least one of a central processing unit, a graphics processing unit, a tensor processing unit, a digital signal processor, or a matrix processor.

[0052] In another general aspect, an apparatus includes: an array of four rows and four columns of nodes, a first optical loop, and a second optical loop. The first optical loop includes a first optical path segment located between the first and second rows, and a second optical path segment located between the third and fourth rows. The second optical loop includes a third optical path segment located between the first and second columns, and a fourth optical path segment located between the third and fourth columns. Each node in the first and second rows is optically coupled to the first optical path segment, each node in the third and fourth rows is optically coupled to the second optical path segment, each node in the first and second columns is optically coupled to the third optical path segment, and each node in the third and fourth columns is optically coupled to the fourth optical path segment.

[0053] In another general aspect, a method includes transmitting optical signals from a first node to a second node via an optical network. Each node includes: an optical transmitter interface configured to transmit optical signals at locations along a coupled optical path of the optical network; and an optical receiver interface configured to receive optical signals at locations along the coupled optical path of the optical network. The method includes: a closed-path propagation guidance mode around a first optical path of the optical network; and a closed-path propagation guidance mode around a second optical path of the optical network. The first and second optical paths overlap each other at a first set of four locations, the first optical path couples to two or more nodes in the node at a second set of corresponding locations different from those in the first set of locations, and the second optical path couples to two or more nodes in the node at a third set of corresponding locations different from all locations in the first and second sets of locations.

[0054] In another general aspect, an apparatus includes: an integrated circuit comprising one or more nodes coupled to an optical network, and a first optical path of the optical network. The first node of the one or more nodes includes: an optical transmitter interface configured to transmit an optical signal at a first location along the coupled optical path of the optical network; and an optical receiver interface configured to receive an optical signal at a second location along the coupled optical path of the optical network. The first optical path of the optical network is fabricated in at least one layer of the integrated circuit and configured to propagate at least a portion of a guided mode around a closed path. The optical transmitter interface in the first node is configured to transmit an optical signal at a first wavelength around the first optical path in a first direction. At least one node coupled to the optical network is configured to couple substantially all remaining optical power at the first wavelength from the first optical path to prevent interference with the optical signal at the first wavelength transmitted by the optical transmitter interface of the first node.

[0055] The implementation may include one or more of the following features. A node coupled to the optical network and configured to couple substantially all remaining optical power from the first optical path at the first wavelength may include a first node.

[0056] The optical transmitter interface in the first node may include a light source coupled to the first optical path via an optical structure that transmits an optical signal at a first wavelength from the light source to the first location.

[0057] The optical transmitter interface of the first node may include an optical power termination structure that receives substantially all remaining optical power coupled from the first optical path at the first wavelength at the first location.

[0058] The optical structure may include at least two ring resonators, wherein the optical signal is at a first wavelength, and the remaining optical power propagates around each ring resonator in opposite directions.

[0059] The optical receiver interface may include an optical splitter configured to couple a portion of the optical power propagating through the second location to one or more detectors.

[0060] The one or more detectors include a plurality of detectors, and the optical receiver interface includes an optical structure configured to couple optical power at different wavelengths to different corresponding detectors of the plurality of detectors.

[0061] A node coupled to an optical network and configured to couple substantially all remaining optical power at the first wavelength from the first optical path may include a second node of one or more nodes on the integrated circuit.

[0062] The second node may include: an optical transmitter interface configured to transmit an optical signal at a third location along the coupled optical path of the optical network; and an optical receiver interface configured to receive an optical signal at a fourth location along the coupled optical path of the optical network.

[0063] The optical receiver interface in the second node can be configured to couple substantially all remaining optical power at the first wavelength from the first optical path.

[0064] Nodes coupled to the optical network and configured to couple substantially all remaining optical power at the first wavelength from the first optical path may include nodes external to the integrated circuit.

[0065] In another general aspect, an apparatus includes: a plurality of nodes coupled to an optical network, and a first optical path of the optical network configured to propagate a guided mode around a closed path. The first node of the plurality of nodes includes: an optical transmitter interface configured to transmit an optical signal at a first location along the coupled optical path of the optical network; and an optical receiver interface configured to receive an optical signal at a second location along the coupled optical path of the optical network. The optical transmitter interface in the first node is configured to transmit an optical signal at a first wavelength around the first optical path in a first direction. At least one node coupled to the optical network is configured to couple substantially all remaining optical power at the first wavelength from the first optical path to prevent interference with the optical signal at the first wavelength transmitted by the optical transmitter interface of the first node.

[0066] The implementation may include one or more of the following features. The node and the first optical path may be disposed on a single substrate.

[0067] At least some of these nodes may include integrated circuits.

[0068] The device may include an integrated circuit, wherein the node is part of the integrated circuit.

[0069] The first optical path may include a planar waveguide formed on a single substrate.

[0070] The first subgroup of the node and the first portion of the first optical path can be disposed on the first substrate, and the second subgroup of the node and the second portion of the first optical path can be disposed on the second substrate.

[0071] In another general aspect, a method includes transmitting an optical signal at a first wavelength from a first node to a second node via an optical network comprising a first optical path configured to propagate a guided mode around a closed path. The first node is configured to transmit the optical signal around the first optical path in a first direction. At least one node coupled to the optical network couples substantially all remaining optical power at the first wavelength from the first optical path to prevent interference with the optical signal at the first wavelength transmitted by the first node.

[0072] The implementation may include one or more of the following features. The at least one node coupled to the optical network and configured to couple substantially all remaining optical power from the first optical path at the first wavelength may include a first node.

[0073] In another general aspect, an apparatus includes: a first optical network configured to propagate a guided pattern around a first closed path; and at least a first node, a second node, and a third node coupled to the first closed path. The first node includes: an optical transmitter interface configured to transmit an optical signal at a first wavelength to the second node along a portion of the first closed path, and configured to transmit an optical signal at a second wavelength to the third node along a portion of the first closed path; and an optical receiver interface configured to receive an optical signal at a third wavelength from a location along the first closed path. The second node includes: an optical transmitter interface configured to transmit an optical signal at a third wavelength to the first node along a portion of the first closed path, and configured to transmit an optical signal at the second wavelength to the third node along a portion of the first closed path; and an optical receiver interface configured to receive an optical signal at the first wavelength from a location along the first closed path. The third node includes: an optical transmitter interface configured to transmit an optical signal at the first wavelength onto the first closed path, and configured to transmit an optical signal at the third wavelength onto the first closed path; and an optical receiver interface configured to receive an optical signal at the second wavelength from a location along the first closed path.

[0074] Implementations may include one or more of the following features. The device may also include a second optical network configured to propagate a guiding pattern around a second closed path, wherein the third node is coupled to the second closed path.

[0075] The device may also include a fourth node coupled to the second closed path.

[0076] The device may also include a third optical network configured to propagate a guided pattern around a third closed path, wherein the fourth node is coupled to the third closed path.

[0077] The device may also include at least a fifth node and a sixth node coupled to the third closed path.

[0078] The fifth node may include: an optical transmitter interface configured to transmit an optical signal at a second wavelength to the sixth node along a portion of the third closed path, and configured to transmit an optical signal at a third wavelength to the fourth node along a portion of the third closed path; and an optical receiver interface configured to receive an optical signal at a first wavelength from a location along the third closed path. The sixth node may include: an optical transmitter interface configured to transmit an optical signal at a first wavelength to the fifth node along a portion of the third closed path, and configured to transmit an optical signal at a third wavelength to the fourth node along a portion of the third closed path; and an optical receiver interface configured to receive an optical signal at a second wavelength from a location along the third closed path. The fourth node may include: an optical transmitter interface configured to transmit an optical signal at a second wavelength onto the third closed path, and configured to transmit an optical signal at a first wavelength onto the third closed path; and an optical receiver interface configured to receive an optical signal at a third wavelength from a location along the third closed path.

[0079] The optical receiver interface of the first node can also be configured to receive an optical signal at the second wavelength from a location along the first closed path.

[0080] In another general aspect, an apparatus includes: a first optical network configured to propagate a guiding pattern around a first closed path; a second optical network configured to propagate a guiding pattern around a second closed path; a switching node coupled to the first closed path and the second closed path; and a plurality of nodes configured to communicate between the plurality of nodes using a first wavelength group through the first optical network, and to communicate with the switching node through the first optical network using a second wavelength different from the first wavelength group.

[0081] The implementation may include one or more of the following features. The plurality of nodes may include a first node and a second node coupled to the first closed path but not coupled to the second closed path. The first node may include an optical transmitter interface configured to transmit an optical signal at a first wavelength to the second node along a portion of the first closed path. The optical transmitter interface of the first node may be configured to transmit an optical signal at a second wavelength to the switching node along a portion of the first closed path. The first node may also include an optical receiver interface configured to receive an optical signal at a third wavelength from a location along the first closed path.

[0082] The second node may include: an optical transmitter interface configured to transmit an optical signal at a third wavelength to the first node along a portion of the first closed path; the optical transmitter interface of the second node may be configured to transmit an optical signal at a second wavelength to the third node along a portion of the first closed path; and the second node may include an optical receiver interface configured to receive an optical signal at the first wavelength from a location along the first closed path.

[0083] The switching node may include: an optical transmitter interface configured to transmit an optical signal at the first wavelength onto the first closed path; the optical transmitter interface of the switching node may be configured to transmit an optical signal at the third wavelength onto the first closed path; and the switching node may include an optical receiver interface configured to receive an optical signal at the second wavelength from a location along the first closed path.

[0084] In another general aspect, a method is provided for transmitting optical signals among a plurality of nodes coupled to an optical network configured to propagate guided patterns around a closed path. The method includes: at each node in a subgroup of the plurality of nodes, transmitting an optical signal from that node to other nodes in the subgroup using a unique wavelength from a wavelength group allocated to that node for transmission within the subgroup. The method includes: at each node in the subgroup, receiving optical signals from other nodes in the subgroup using wavelengths from the wavelength group other than the unique wavelength allocated to that node for transmission within the subgroup. The method includes: at a node not in a subgroup of the plurality of nodes, communicating with each node in the subgroup using a wavelength not in that wavelength group.

[0085] In another general aspect, an apparatus includes: a first optical network configured to propagate a guided pattern around a first closed path; and a plurality of nodes, including at least a first node, a second node, and a third node coupled to the first closed path. The plurality of nodes are configured to communicate using a plurality of wavelengths including at least a first wavelength, a second wavelength, and a third wavelength on the first optical network. The first node includes: an optical transmitter interface configured to transmit a first optical signal at the first wavelength onto the first closed path; an optical receiver interface configured to simultaneously detect a second optical signal at the second wavelength and a third optical signal at the third wavelength from the first closed path; and demodulation circuitry coupled to the optical receiver interface of the first node. The demodulation circuitry is configured to determine, for a plurality of time slots, a mapping between a plurality of amplitude levels detected during the time slot and binary symbols modulated onto each of the second and third optical signals. The second node includes: an optical transmitter interface configured to transmit the second optical signal onto the first closed path; an optical receiver interface configured to simultaneously detect multiple optical signals at wavelengths different from the second wavelength from the first closed path; and a demodulation circuit coupled to the optical receiver interface of the second node. The demodulation circuit is configured to determine, for multiple time slots, a mapping between multiple amplitude levels detected during those time slots and binary symbols modulated onto each of the multiple optical signals detected by the optical receiver interface of the second node.

[0086] The implementation may include one or more of the following features. The third node may include: an optical transmitter interface configured to transmit the third optical signal onto the first closed path; an optical receiver interface configured to simultaneously detect multiple optical signals at wavelengths different from the third wavelength from the first closed path; and a demodulation circuit coupled to the optical receiver interface of the third node. The demodulation circuit may be configured to determine, for multiple time slots, a mapping between multiple amplitude levels detected during the time slot and binary symbols modulated onto each of the multiple optical signals detected by the optical receiver interface of the third node.

[0087] This binary symbol can correspond to a non-return-to-zero (NRZ) binary symbol.

[0088] For the demodulation circuitry of the optical receiver interface coupled to the first node, the multiple amplitude levels detected during the time slot, including four amplitude levels, may include: a first amplitude level corresponding to approximately zero power in the second optical signal and approximately zero power in the third optical signal; a second amplitude level corresponding to a first predetermined power amount in the second optical signal and approximately zero power in the third optical signal; a third amplitude level corresponding to approximately zero power in the second optical signal and a second predetermined power amount in the third optical signal; and a fourth amplitude level corresponding to a third predetermined power amount, which is substantially equal to the sum of the first predetermined power amount in the second optical signal and the second predetermined power amount in the third optical signal.

[0089] The first node may further include a second optical receiver interface configured to simultaneously detect multiple optical signals at wavelengths different from the first wavelength, the second wavelength, and the third wavelength from the first closed path. The first node may also include a second demodulation circuit coupled to the second optical receiver interface of the first node and configured to determine, for multiple time slots, a mapping between multiple amplitude levels detected during the time slot and binary symbols modulated onto each of the multiple optical signals detected by the second optical receiver interface of the first node.

[0090] The plurality of nodes may include 2N+1 nodes. The demodulation circuitry coupled to the optical receiver interface of the first node may include at least N detectors, each detector being configured to determine, for a plurality of time slots, a mapping between at least four amplitude levels detected during that time slot and binary symbols modulated onto each of at least two optical signals.

[0091] The plurality of nodes may include 2N+1 nodes, and the demodulation circuitry coupled to the optical receiver interface of the first node may be configured to determine, for the plurality of time slots, at least 2 detected during that time slot. N A mapping between an amplitude level and a binary symbol modulated onto each of at least 2N optical signals.

[0092] The first node can be configured to couple substantially all remaining optical power at the first wavelength from the first optical path to prevent interference with the first optical signal transmitted by the optical transmitter interface of the first node.

[0093] In another general aspect, an apparatus includes: a first optical network configured to propagate a guided pattern around a first closed path; and a plurality of nodes, including at least a first node coupled to the first closed path. The plurality of nodes are configured to communicate on the first optical network using a plurality of wavelengths including at least a first wavelength, a second wavelength, and a third wavelength. The first node includes: an optical transmitter interface configured to transmit a first optical signal at the first wavelength onto the first closed path; an optical receiver interface configured to simultaneously detect a second optical signal at the second wavelength and a third optical signal at the third wavelength from the first closed path; and demodulation circuitry coupled to the optical receiver interface of the first node. The demodulation circuitry is configured to determine, for a plurality of time slots, a mapping between a plurality of amplitude levels detected during the time slot and binary symbols modulated onto each of the second and third optical signals.

[0094] The implementation may include one or more of the following features. The plurality of nodes may include a second node comprising: an optical transmitter interface configured to transmit the second optical signal onto the first closed path; an optical receiver interface configured to simultaneously detect from the first closed path multiple optical signals at wavelengths different from the second wavelength; and demodulation circuitry coupled to the optical receiver interface of the second node. The demodulation circuitry is configured to determine, for multiple time slots, a mapping between multiple amplitude levels detected during the time slot and binary symbols modulated onto each of the multiple optical signals detected by the optical receiver interface of the second node.

[0095] In another general aspect, a method includes transmitting a first optical signal at a first wavelength onto a first closed path at a first node coupled to a first optical network configured to propagate a guiding mode around a first closed path; simultaneously detecting a second optical signal at a second wavelength and a third optical signal at a third wavelength from the first closed path at the first node; and determining, for a plurality of time slots, a mapping between a plurality of amplitude levels detected during the time slots and binary symbols modulated onto each of the second and third optical signals.

[0096] The implementation may include one or more of the following features. The method may include: sending a second optical signal onto the first closed path at a second node coupled to the first optical network; simultaneously detecting multiple optical signals at wavelengths different from the second wavelength from the first closed path; and determining, for multiple time slots, a mapping between multiple amplitude levels detected during the time slot and binary symbols modulated onto each of the multiple optical signals detected by the optical receiver interface of the second node.

[0097] Details of one or more embodiments of the subject matter described herein are set forth in the accompanying drawings and the following description. Other features, aspects, and advantages of the invention will become apparent from the description, drawings, and claims.

[0098] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the event of any conflict with a patent application or its disclosure, this specification (including the definitions) shall prevail. Attached Figure Description

[0099] This disclosure is best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be emphasized that, in accordance with common practice, the various features in the drawings are not drawn to scale. Instead, for clarity, the dimensions of the various features have been arbitrarily enlarged or reduced.

[0100] Figure 1A and Figure 1B This is a schematic diagram of an example of an optically coupled multi-node computing system.

[0101] Figure 2A , Figure 2B , Figure 2C and Figure 2D This is a schematic diagram of an example optical loop arrangement.

[0102] Figure 3A and Figure 3B This is a schematic diagram of an example interconnection of multiple photonic integrated circuits.

[0103] Figure 4A and Figure 4B This is a schematic diagram of the different states of the example switch.

[0104] Figure 5A and Figure 5B This is a schematic diagram of the different states of the example switch.

[0105] Figure 6A and Figure 6B This is a schematic diagram illustrating the different states of an example receiver / transmitter module used in a node.

[0106] Figure 7 This is a schematic diagram of an example of an optically coupled multi-node computing system.

[0107] Figure 8A This is a schematic diagram of an example optical communication interface.

[0108] Figure 8B This is a schematic diagram of an example optical receiver interface.

[0109] Figure 9A , Figure 9B and Figure 9CIt is a table used to receive values ​​of multiple wavelengths simultaneously.

[0110] Figure 10 This is a schematic diagram of an example of an optically coupled multi-node computing system.

[0111] Figure 11 This is a schematic diagram of the interface part of an optically coupled multi-node computing system.

[0112] Figure 12 This is a schematic diagram of an example rack-mounted optical system.

[0113] Figure 13 This is a schematic diagram of an example cluster (pod) optical system.

[0114] In the various figures, the same reference numerals and names denote the same elements. Detailed Implementation

[0115] Figure 1A A schematic diagram illustrating an example of an optically coupled multi-node computing system 100A is shown. System 100A includes 16 nodes (labeled 0 to 15) (e.g., 106a, 106b, 106c, 106d, collectively referred to as 106) coupled to an optical network comprising overlapping unidirectional optical loops 102 and 104 providing an optical signal flow for transmitting optical signals between different pairs of nodes 106. For example, each optical loop 102, 104 can be implemented as an optical waveguide formed on an integrated platform to propagate guided modes around a closed path. In this example, the paths of optical loops 102, 104 overlap at four locations (e.g., 108) where they overlap, and do not include any switching elements. Therefore, if the waveguides at these overlapping locations are fabricated in different layers of a photonic integrated circuit without physical intersection, optical signals can pass through these overlapping locations without significant loss. Alternatively, if the waveguides do intersect each other at the overlapping locations, the optical signal can pass through these overlapping locations with relatively small loss (e.g., 0.05 dB–0.1 dB at each intersection).

[0116] Exemplarily, optical loops 102 and 104 of the optical network can serve as a first optical path and a second optical path, respectively. The first optical path of the optical network includes at least a portion of a guided mode fabricated in at least one layer of the integrated circuit and configured to propagate a guided mode around a closed path; and the second optical path of the optical network includes at least a portion of a guided mode fabricated in at least one layer of the integrated circuit and configured to propagate a guided mode around a closed path. Exemplarily, the first optical path and the second optical path can be fabricated in different layers without physical intersection. Optionally, the first optical path and the second optical path can also be fabricated in the same layer.

[0117] Node 106 can be configured as a computing node comprising one or more processors, as well as other optical, electronic, or optoelectronic circuitry, which may be integrated into an integrated circuit for each node or into a single integrated circuit comprising all 16 nodes. The processors may include one or more digital central processing units (or cores) and / or one or more photonic computing modules such as an optoelectronic matrix multiplication module, as described, for example, in U.S. Patent Application 16 / 431,167, filed June 4, 2019, and U.S. Patent Application 17 / 204,320, filed March 17, 2021 (provided in Appendix A), both of which are incorporated herein by reference. In this example, each node is coupled to two optical loops 102 and 104 via a corresponding pair of transmitter and receiver modules 110. For example, transmitter and receiver modules 110 may use a ring resonator 116 coupled to a location on the optical loop. In this example, each node 106 is optically coupled to two loops 102, 104, so that optical signals can travel from one node to any other node in a single hop. Here, the term "hop" generally refers to the transmission of an optical signal from one node or switch to another. Therefore, if an optical signal travels directly from node A to node B, that is one hop. If the optical signal travels from node A to node B via a switch node or intermediate node C, that is two hops. The split bandwidth of this implementation is:

[0118]

[0119] Here, N represents the number of nodes, Tx / Rx BW represents the transmit bandwidth (Tx BW) or receive bandwidth (Rx BW) (usually Tx BW = Rx BW), and #wavelength represents the number of wavelengths used to transmit signals between nodes 106. The partition bandwidth generally refers to the maximum bandwidth between any two nodes 106 in system 100A. For any two nodes in system 100A, the maximum bandwidth between these two nodes will be at least this partition bandwidth. For a pair of nodes, the maximum bandwidth between the two nodes in this pair may be greater than this partition bandwidth. The partition bandwidth is a measure of the transmission bottleneck in the system, therefore a larger partition bandwidth is generally preferred.

[0120] In some implementations, each node transmits an optical signal using a specified wavelength, and different nodes use different wavelengths. For example, node 0 transmits an optical signal using wavelength WL0, node 1 transmits an optical signal using wavelength WL1, ..., node 15 transmits an optical signal using wavelength WL15. When nodes 1 through 15 receive an optical signal with wavelength WL0, they know that the optical signal was transmitted from node 0. Similarly, when nodes 0 and 2 through 15 receive an optical signal with wavelength WL1, they know that the optical signal was transmitted from node 1. Each node can decide whether to further process the optical signal or ignore it upon receiving it. In this example, each node broadcasts the optical signal to other nodes, and the other nodes determine how to process the received signal.

[0121] Because there are two optical loops 102 and 104, each node can potentially transmit a first optical signal on optical loop 102 and a second optical signal on optical loop 104 during the same time slot. Having two optical loops 102 and 104 increases the communication bandwidth between nodes compared to having only one optical loop.

[0122] In some implementations, the number of wavelengths used by nodes for optical signal transmission is less than the number of nodes. Two or more nodes share the same wavelength when transmitting optical signals. System 100A includes a controller for scheduling optical signal transmissions between nodes sharing the same wavelength on the same loop. For example, suppose nodes 0 to 3 transmit optical signals using wavelength WL0, nodes 4 to 7 transmit optical signals using wavelength WL1, nodes 8 to 11 transmit optical signals using wavelength WL2, and nodes 12 to 15 transmit optical signals using wavelength WL3. The controller can schedule data transmissions at different times by different nodes sharing a wavelength through the optical loop. For example, the controller can configure one of nodes 0 to 3 to transmit an optical signal of wavelength WL0 in time slot 0 in the loop, configure one of nodes 4 to 7 to transmit an optical signal of wavelength WL1 in time slot 0 in the loop, configure one of nodes 9 to 11 to transmit an optical signal of wavelength WL2 in time slot 0 in the loop, and configure one of nodes 12 to 15 to transmit an optical signal of wavelength WL3 in time slot 0 in the loop.

[0123] Because there are two optical loops 102 and 104, each node may transmit a first optical signal on optical loop 102 and a second optical signal on optical loop 104 during the same time slot. It is also possible for the first node to transmit the first optical signal on optical loop 102 and the second node to transmit the second optical signal on optical loop 104 during the same time slot when the first and second nodes share the same transmission wavelength.

[0124] In some implementations, multiple nodes share the same transmission wavelength, and system 100A includes a controller for scheduling optical signal transmissions between nodes 106. The controller also informs the intended receivers of the signal so that receiver nodes know they should expect to receive the signal in a specific time slot. For example, the controller can schedule data transmissions between different pairs of nodes via an optical loop at different times. The controller can configure a first node (e.g., node 1) as a transmitter on the optical loop and a second node (e.g., node 10) as a receiver on the optical loop during a first time period t1, and prevent other nodes from transmitting optical signals on the same optical loop during the first time period t1. The controller can configure a third node (e.g., node 3) as a transmitter on the optical loop and a second node (e.g., node 0) as a receiver on the optical loop during a second time period t2, and prevent other nodes from transmitting optical signals on the same optical loop during the second time period t1, and so on. Because there are two optical loops 102 and 104, it is possible for the first node to send a first optical signal to the second node on optical loop 102 and for the third node to send a second optical signal to the fourth node on optical loop 104 during the same time period. Having two optical loops 102 and 104 increases the communication bandwidth between nodes compared to having only one optical loop.

[0125] System 100A includes an array of four rows and four columns of nodes. Optical loop 102 includes a first waveguide portion extending between the first and second column nodes and optically coupled to each node in the first and second columns. Optical loop 102 also includes a second waveguide portion extending between the third and fourth column nodes and optically coupled to each node in the third and fourth columns. Thus, optical loop 102 is optically coupled to each node in the array of nodes. Optical loop 104 includes a first waveguide portion extending between the first and second row nodes and optically coupled to each node in the first and second rows. Optical loop 104 also includes a second waveguide portion extending between the third and fourth row nodes and optically coupled to each node in the third and fourth rows.

[0126] Figure 1BA schematic diagram illustrating an example of an optically coupled multi-node computing system 100B is shown. System 100B includes 16 nodes (labeled 0 to 15) (e.g., 118a, 118b, 118c, 118d, collectively referred to as 118) coupled to an optical network comprising overlapping unidirectional optical loops 102 and 104 that provide optical signal streams for transmitting optical signals between different pairs of nodes 118. In this example, overlapping locations include switches 120a, 120b, 120c, 120d (collectively referred to as 120) configured to transmit optical signal streams between the two optical loops 112 and 114. Therefore, in this example, each node 118 is coupled to only one of the optical loops 112 or 114, and if the optical signal does not pass through switch 120, the optical signal can travel from one node to any other node in a single hop, or if the optical signal travels along the path through switch 120, it can travel from one node to any other node in two hops. Furthermore, optical crosstalk between optical loops 112 and 114 can be reduced by the presence of the switch. The split bandwidth of this implementation is also:

[0127]

[0128] In some implementations, system 100B includes a controller for scheduling optical signal transmission between nodes 118 and configuring switches 120 to enable optical signals to be transmitted from a transmitter to a receiver. For example, to enable node 1 to transmit optical signals to node 4, the controller configures switches 120b, 120d, and 120c to be in a passing state (see [link to documentation]). Figure 4A and 5A This allows the optical signal to pass through optical loop 114 from node 1 to switch 120b, from switch 120b to switch 120d, from switch 120d to switch 120c, and from switch 120c to node 4. To enable node 1 to send an optical signal to node 5, the controller configures switches 120b and 120d to a passing state and switch 120c to a switching state (see [link to controller configuration]). Figure 4B and 5BThis allows the optical signal to pass through node 1 to switch 120b, from switch 120b to switch 120d, from switch 120d to switch 120c on optical loop 114, and from switch 120c to node 5 on optical loop 112. Alternatively, the controller can configure switch 120b to be in a switching state and switches 120d and 120c to be in a passing state, allowing the optical signal to pass through node 1 to switch 120b, from switch 120b to switch 120d, from switch 120d to switch 120c on optical loop 114, and from switch 120c to node 5 on optical loop 112.

[0129] In some implementations, the controller can evaluate the switch configuration to determine whether only one pair of nodes can communicate with each other during a time period, or whether two pairs of nodes can communicate with each other during that time period. If the switch is configured to cause optical loops 112, 114 to form a single optical path during a first time period, then only two nodes can communicate with each other on that optical path during that first time period. If the switch is configured to cause optical loops 112, 114 to form two separate optical paths during a second time period, then the first and second nodes can communicate with each other, and the third and fourth nodes can communicate with each other during that second time period.

[0130] In some embodiments, each switch 120 toggles the optical signal to allow it to either continue traveling on the same optical loop or switch to a different optical loop without further processing. In some embodiments, such as in a larger optical network where the optical signal can pass through a large number of switches resulting in significant signal attenuation, one or more switches may provide optical amplification to improve the signal level. In some embodiments, one or more switches may convert the received optical signal into an electrical signal, process the electrical signal using electronic circuitry, convert the electrical signal back into an optical signal, and transmit the optical signal to a next destination.

[0131] Other examples of such optically coupled multi-node computing systems can be implemented. For instance, in some implementations, there may be subgroups containing overlapping locations of switches. Moreover, multiple optical loops oriented vertically (e.g., in the Y direction) and horizontally (e.g., in the X direction) can be combined such that any two optical loops overlap each other at four locations. Figure 2A An example of an arrangement 200A with four optical loops is shown, wherein the four optical loops are respectively the first to the fourth optical paths, the four optical loops including two horizontal loops 130 having long straight sections extending in the x direction and two vertical loops 132 having long straight sections extending in the y direction. Figure 2BAn example of another arrangement 200B with four optical loops is shown, which includes two horizontal loops 140 and two vertical loops 142, wherein a switch 144 is provided at each location where the two loops overlap.

[0132] Figure 2C An example of a unidirectional loop optical network 200C with six optical loops is shown. These six optical loops include two horizontal loops 130 with long straight sections extending in the x-direction, two vertical loops 132 with long straight sections extending in the y-direction, and two diagonal loops 134 and 136. Diagonal loop 134 allows nodes in the upper right quadrant of the node array to communicate with nodes in the lower left quadrant. Diagonal loop 136 allows nodes in the upper left quadrant of the node array to communicate with nodes in the lower right quadrant.

[0133] Figure 2D An example of a unidirectional loop optical network 200D with a right optical loop is shown, comprising two horizontal loops 130 with long straight segments extending in the x-direction, two vertical loops 132 with long straight segments extending in the y-direction, and four diagonal loops 136. The diagonal loops 134 allow nodes in the upper right quadrant of the node array to communicate with nodes in the lower left quadrant. The diagonal loops 136 allow nodes in the upper left quadrant of the node array to communicate with nodes in the lower right quadrant. Compared to a unidirectional loop optical network 200C, the unidirectional loop optical network 200D has a higher transmission bandwidth in the diagonal directions.

[0134] Furthermore, if there are subgroups of adjacent nodes fabricated on different photonic integrated circuits (PICs), the PICs can be interconnected to provide a closed path through portions of optical loops interconnected by optical fibers or fiber bundles, for example... Figure 3A As shown in arrangement 300A, this arrangement includes four photonic integrated circuits (PICs), wherein the upper left photonic integrated circuit, clockwise to the lower left photonic integrated circuit, are the first to fourth integrated circuits, respectively. Each integrated circuit may include multiple nodes coupled to the optical network. The corresponding ends of portions of the loop waveguide 150 are interconnected via segments of optical fiber 152. This technique can be used to scale up the system.

[0135] Figure 3BAn example of a unidirectional loop optical network 300B is shown, which includes a partial loop waveguide 150 interconnected by segments of optical fibers 152 extending in the x and y directions. The unidirectional loop optical network 300B also includes a partial loop waveguide 154 interconnected by segments of optical fibers 156 extending diagonally. The diagonal partial loop waveguide 154 and the segments of optical fibers 156 allow nodes in the upper right photonic integrated circuit (second integrated circuit) to communicate with nodes in the lower left photonic integrated circuit (fourth integrated circuit), and allow nodes in the upper left photonic integrated circuit (first integrated circuit) to communicate with nodes in the lower right photonic integrated circuit (third integrated circuit).

[0136] Exemplarily, the first optical path of the optical network includes at least a portion fabricated in at least one layer of the second integrated circuit. The second optical path of the optical network includes at least a portion fabricated in at least one layer of the third integrated circuit. Various types of switches can be used at overlapping locations. In some embodiments, two ring resonators 162, 164 are used to form switch 160. Switch 160 has Figure 4A The transmission status shown and Figure 4B The switching states are shown. In the transmission state, the optical signal 170 traveling on waveguide 166 continues on waveguide 166, and the optical signal 172 traveling on waveguide 168 continues on waveguide 168. In the switching state, the optical signal 174 traveling on waveguide 166 is switched to waveguide 168, and the optical signal 176 traveling on waveguide 168 is switched to waveguide 166. For example, when having Figure 4A , 4B The switch shown is used for transmitting and switching states. Figure 2B In the optical loop arrangement, and when the switch is in the switching state, the optical signal will switch from the horizontal loop to the vertical loop, or from the vertical loop to the horizontal loop. Given the narrow bandwidth of the ring resonator, this type of switch can be used to switch a single wavelength at a time. The ring resonator can be tuned, or a separate pair of rings can be pre-configured for each wavelength.

[0137] In some implementations, a Mach-Zehnder interferometer (MZI) is used to form the switch. This switch has... Figure 5A The transmission status shown and Figure 5B The switching state is shown in the diagram. Given the wide bandwidth of MZI, this type of switch can be used to switch multiple wavelengths simultaneously (e.g., all wavelengths).

[0138] Figure 6A and 6BThe different states of the receiver / transmitter module 110, including both an optical receiver interface (Rx) 180 and an optical transmitter interface (Tx) 182, are shown. Figure 6A In this configuration, the optical receiver interface Rx 180 is configured to couple substantially all the optical power in the received optical signal 188 to the photodetector (PD) 184, and the optical transmitter interface Tx 182 is configured to modulate the light from the light source 186 to provide the optical signal 186, which has been modulated with data. The dashed lines indicate the state of the corresponding waveguide where substantially no optical power propagates. Figure 6B In this state, the optical receiver interface Rx180 is configured to allow the input optical signal 190 to pass through without being coupled and detected, and the optical transmitter interface Tx 182 is configured to prevent any optical signal from being sent onto the coupled optical path. Measurement photodiodes (MPDs) 192 and 194 can be used to verify the tuning of the ring resonator used for coupling the transmitted / received optical signals. Figure 6A Under these conditions, photodiode 192 should measure a low signal, and photodiode 194 should also measure a low signal. Figure 6B In this state, photodiode 192 should be idle and no signal should be measured, and photodiode 194 should measure a high signal.

[0139] Figure 7 Another example is shown of an optically coupled multi-node computing system 700 comprising multiple chips and using four different wavelengths for inter-chip communication. In this example, system 700 includes four chips (labeled 1 to 4) 702a, 702b, 702c, and 702d (collectively referred to as 702), which are interconnected (e.g., via optical fiber 704) to communicate over a unidirectional loop optical network 722. For example, each chip 702 may represent an optical communication interface for a computing node (not shown). Each chip includes an optical receiver interface Rx 706 and an optical transmitter interface Tx 708. In this example, each chip 702 is configured to use different laser wavelengths for transmission (i.e., wavelengths 1 to 4) and is configured to receive each of the three remaining wavelengths in a corresponding photodetector coupled by a corresponding ring resonator tuned to those wavelengths. For example, chip 702a is configured to transmit data using laser wavelength 1, chip 702b is configured to transmit data using laser wavelength 2, chip 702c is configured to transmit data using laser wavelength 3, and chip 702d is configured to transmit data using laser wavelength 4.

[0140] Each chip 702's optical receiver interface 706 includes a photodetector 706 for detecting received optical signals. The optical receiver interface 706 includes an optical splitter 714 having a first branch 718 and a second branch 720. The optical splitter splits the received optical signal, and a portion of the received optical power (e.g., 25%) is sent to the first branch 718, while the remaining portion (e.g., 75%) is sent to the second branch 720. The optical signal in the first branch 718 is coupled to the photodetector 706.

[0141] The optical transmitter interface Tx 708 includes a pair of ring resonators 710 configured to both couple the transmitted optical signal (originating from the optical transmitter interface Tx 708) in the appropriate direction to the optical network 722, and couple substantially all received optical power in the second branch 720 at the same allocated wavelength (e.g., from the same transmitted signal, after it has propagated around the loop) to the optical terminator 712 to prevent the received optical power from interfering with the transmitted optical signal. The coupled (received) optical power propagates in opposite directions around the pair of ring resonators 710 into the optical terminator 712.

[0142] Reference Figure 8A Example optical communication interface 800 can be used in optical systems that communicate between various optical communication interfaces using five wavelengths. Optical communication interface 800 includes similar... Figure 7 Chip 802 is an alternative to chip 702, but chip 802 includes four photodetectors in its optical receiver interface instead of the three photodetectors used in chip 702. Chip 802 includes an optical transmitter interface 810 and an optical receiver interface 804. The optical transmitter interface 810 uses one wavelength, and the optical receiver interface 804 has a separate group of ring resonators 806 and photodetectors 808 for each remaining wavelength in the system. In this example, the optical transmitter interface 810 uses wavelength 1. The optical receiver interface 804 includes four groups of ring resonators 806, each group of ring resonators 806 being designed to couple a specific wavelength from 2 to 5 to a corresponding photodiode 808.

[0143] In systems using an odd number of wavelengths (e.g., 2N+1, where N is an integer), the remaining 2N wavelengths can be detected individually (as in this example), or they can be detected by fewer photodetectors within a wavelength subgroup (e.g. Figure 8B The optical receiver interface 850 is shown. In this example, there are still 5 wavelengths, but only 2 photodetectors 852 are present instead of (in the optical receiver interface 850). Figure 8A(The example uses) four photodetectors 808. Each photodetector 852 receives optical signals from two pairs of ring resonators 854.

[0144] In some implementations, the system uses PAM4 modulation to modulate optical signals transmitted between optical communication interfaces or chips to have four different predetermined amplitude levels. Each photodetector 852 is connected to a corresponding demodulation circuit (PAM4 RX) 856, which is configured to perform PAM-4 demodulation on the four different predetermined amplitude levels of the received optical signal. Since two different wavelengths are combined onto a single photodetector 856, the optical power amplitude levels are added incoherently (i.e., without interference). As the optical signal travels along the optical loop 722, a portion of the optical power is splittered by each chip encountered along the optical loop 722. The more chips the optical signal encounters, the greater the amount of optical power splittered, and the smaller the remaining optical power. Considering the coupling ratio of the directional coupler / splitter in each chip 702, and the corresponding number of times a given signal (at a given wavelength) from a given chip is splittered before being received at that chip, there will be a distinct and unique amplitude level associated with each chip / wavelength.

[0145] Figures 9A to 9C Includes a table showing exemplary values ​​for the power levels of optical signals with various wavelengths when the optical signal passes through various numbers of chips. Figure 9A Table 900 includes examples showing the power levels of optical signals of various wavelengths when the optical signal passes through various numbers of chips. The values ​​in Table 900 are normalized to a maximum value of 1. Figure 9A The example assumes that chip 1 uses wavelength 1 for transmitting optical signals. Similarly, chips 2 through 5 use wavelengths 2 through 5 for transmitting optical signals, respectively. If chip 1 sends an optical signal with wavelength 1 and amplitude 1 to chip 2, the power level of the optical signal with wavelength 1 received at chip 2 is 0.7. If chip 1 sends an optical signal with amplitude 1 to chip 3, passing through chip 2, the power level of the optical signal with wavelength 1 received at chip 3 is 0.7 * 0.7 = 0.49. If chip 1 sends an optical signal with amplitude 1 to chip 4, passing through chips 2 and 3, the power level of the optical signal with wavelength 1 received at chip 4 is 0.7. 3 =0.343. If chip 1 sends an optical signal with an amplitude of 1 to chip 5, passing through chips 2 to 4 along the way, the power level of the optical signal with a wavelength of 1 received at chip 5 will be 0.7. 4= 0.2401. Similarly, if chip 2 sends an optical signal with wavelength 2 and amplitude 1 to chip 3, the power level of the optical signal with wavelength 2 received at chip 3 is 0.7. If chip 2 sends an optical signal with amplitude 1 to chip 1, passing through chip 3 to chip 5, the power level of the optical signal with wavelength 2 received at chip 1 is 0.2401.

[0146] Figure 9B Table 902 shows the obtained amplitude level and the normalized amplitude level (normalized to the maximum amplitude of 1), which is derived from... Figure 9C The mapping of wavelengths (labeled WL#) received at each of the two receivers (RX0, RX1) shown in Table 904 is obtained. Using this scheme, multiple optical signals at different wavelengths from different corresponding transmitting chips can be simultaneously detected on a single photodetector, thereby reducing the total number of photodetectors required. In this example, chip 1 includes receivers RX0 and RX1. Receiver RX0 detects wavelengths WL3 and WL5, and receiver RX1 detects wavelengths WL2 and WL4. Chip 2 includes receivers RX0 and RX1, where receiver RX0 detects wavelengths WL1 and WL4, and receiver RX1 detects wavelengths WL3 and WL5. Chip 3 includes receivers RX0 and RX1, where receiver RX0 detects wavelengths WL2 and WL5, and receiver RX1 detects wavelengths WL1 and WL4. Chip 4 includes receivers RX0 and RX1, where receiver RX0 detects wavelengths WL1 and WL3, and receiver RX1 detects wavelengths WL2 and WL5. Chip 5 includes receivers RX0 and RX1, wherein receiver RX0 detects wavelengths WL2 and WL4, and receiver RX1 detects wavelengths WL1 and WL3.

[0147] like Figure 9B As shown, if the receiver RX0 of chip 1 detects an optical signal with an amplitude of approximately 1.043, it can be inferred that the received signal is '1' at wavelength WL3 and '1' at wavelength WL5. If the receiver RX0 of chip 1 detects an optical signal with an amplitude of 0.7, it can be inferred that the received signal is '1' at wavelength WL5 and '0' at wavelength WL3. If the receiver RX0 of chip 1 detects an optical signal with an amplitude of 0.343, it can be inferred that the received signal is '1' at wavelength WL3 and '0' at wavelength WL5. If the receiver RX0 of chip 1 detects an optical signal with an amplitude of 0, it can be inferred that the received signal is '0' at wavelength WL3 and '0' at wavelength WL5.

[0148] If receiver RX1 of chip 1 detects an optical signal with an amplitude of 0.7301, it can be inferred that the received signal is '1' at wavelength WL2 and '1' at wavelength WL4. If receiver RX1 of chip 1 detects an optical signal with an amplitude of 0.49, it can be inferred that the received signal is '1' at wavelength WL4 and '0' at wavelength WL2. If receiver RX1 of chip 1 detects an optical signal with an amplitude of 0.2401, it can be inferred that the received signal is '1' at wavelength WL2 and '0' at wavelength WL4. If receiver RX1 of chip 1 detects an optical signal with an amplitude of 0, it can be inferred that the received signal is '0' at wavelength WL2 and '0' at wavelength WL4. The analog signals detected at receivers RX0 and RX1 of chips 2 to 5 can be converted to digital values ​​in a similar manner.

[0149] Figure 10 Another example of an optically coupled multi-node computing system 1000 is shown. In this example, eight computing nodes 1002 are optically connected via a loop optical network 1004 and electrically connected in one of two Peripheral Component Fast Interconnect (PCIE) networks 1006a, 1006b (collectively referred to as 1006), controlled by corresponding PCIE switches 1008a, 1008b (collectively referred to as 1008) having ports 1010 for connection to other systems (e.g., host systems). There is also a ninth node 1012, which has a switch 1014 optically connected to the eight computing nodes 1002 in the same loop optical network 1004. The loop optical network 1004 may be, for example, a dense wavelength division multiplexed (DWDM) ring network providing all-to-all direct routing between the computing nodes 1002 and the switch node 1012. Laser source 1016 (e.g., a comb laser) can provide light of different wavelengths, which are then modulated by individual nodes 1002. Laser source 1016 transmits laser light through waveguide nodes, such as those similar to... Figure 7 and Figure 8A The example shown (except that the laser source is outside the node). Alternatively, in other examples, each node 1002, 1012 may include or be coupled to its own laser source.

[0150] Figure 11An example is shown including optical transmitter (TX) and receiver (RX) interfaces in each node 1002, 1012 for coupling optical signals to and from the loop optical network 1004. In this configuration, each compute node 1002 includes a processing engine (PE) 1100, which is assigned a unique laser wavelength (L#) for transmission to other compute nodes 1002 and is configured to receive each other wavelength used by the compute node 1002. Each compute node 1002 is connected to a TX interface for transmission on the unique laser wavelength (one of wavelengths L0 to L7) assigned to that compute node 1002. For example, PE 0 is connected to a TX interface configured to transmit an optical signal at wavelength L0, PE 1 is connected to a TX interface configured to transmit an optical signal at wavelength L1, PE 2 is connected to a TX interface configured to transmit an optical signal at wavelength L2, and PE 7 is connected to a TX interface configured to transmit an optical signal at wavelength L7. Each processing engine is connected to a TX interface configured to send an optical signal with a common laser wavelength (L8) to the switch node 1012. Only one processing engine sends an optical signal with wavelength L8 at any given time slot. The switch node 1012 transmits and receives signals at wavelength L8 when communicating with the compute node 1002.

[0151] Switching node 1012 also includes another set of optical receiver RX and optical transmitter TX interfaces for communication on different loop optical networks 1102. In this example, there are eight switching nodes 1012, configured such that when a switching node 1012 communicates with other switching nodes 1012 on the loop optical network 1102, each switching node 1012 is configured to transmit on a unique laser wavelength (one of wavelengths L0 to L7) assigned to that switching node 1012. For example, switching node 0 is configured to transmit an optical signal of wavelength L0 on the loop optical network 1102, switching node 1 is configured to transmit an optical signal of wavelength L1 on the loop optical network 1102, switching node 2 is configured to transmit an optical signal of wavelength L2 on the loop optical network 1102, and switching node 7 is configured to transmit an optical signal of wavelength L7 on the loop optical network 1102.

[0152] Figure 12An example of a rack optical system 1200 is shown, comprising racks for eight optically coupled multi-node computing systems (e.g., 1000a, 1000b, 1000c (collectively referred to as 1000)). Each system 1000 includes a chassis and is connected to another loop optical network 1202 of the rack via corresponding switch interfaces in their switch nodes. For communication on the loop optical network 1202, each system 1000 includes switches for different wavelengths assigned to subgroups of eight of nine wavelengths. For example, a switch in system 1000a can communicate with other systems 1000 on the loop optical network 1202 using wavelength 1. Similarly, switches in systems 1000b and 1000c can communicate with other systems 1000 on the loop optical network 1202 using wavelengths 1 and 2, respectively. Each computing node 1002 in system 1000 is 3 hops away from any other computing node 1002 in another system 1000 (e.g., node A in system 1 to switch 1 in system 1, switch 1 in system 1 to switch 2 in system 2, and switch 2 in system 2 to node B in system 2).

[0153] Figure 13 An example of a clustered optical system 1300 is shown, comprising eight rack optical systems (e.g., 1200a, 1200b (collectively referred to as 1200)), each rack optical system 1200 including eight multi-node computing systems 1000. In this example, the clustered optical system 1300 includes eight rows of multi-node computing systems 1000 and eight columns of multi-node computing systems 1000. The clustered optical system 1300 includes loop optical networks, such as 1302a, 1302b (collectively referred to as 1302), wherein each loop optical network 1302 connects the multi-node computing systems 1000 in rows. Each multi-node computing system 1000 is connected to the loop optical networks 1202 and 1302 via a corresponding switch interface in its switch node, thereby allowing the multi-node computing system 1000 to communicate with any other multi-node computing system 1000 in the clustered optical system 1300.

[0154] Each multi-node computing system 1000 includes a switch node comprising two distinct sets of switch interfaces for connecting to these additional loop optical networks 1202, 1302. One set of switch interfaces is used to connect to other multi-node computing systems 1000 within the same rack optical system 1200 via the loop optical network 1202, and the other set of switch interfaces is used to connect to other multi-node computing systems 1000 in the same row of different rack optical systems 1200.

[0155] To enable communication between each row of the cross-rack optical system 1200 on the loop optical network 1302, the switches of each rack optical system 1200 are assigned to different wavelengths of a subgroup of 8 wavelengths out of 9 wavelengths. Each computing node 1002 in a rack / chassis is 4 hops away from any other computing node 1002 in another rack / chassis (e.g., node A in system 1 of rack 1 to switch 1 of system 1 of rack 1, switch 1 of system 1 of rack 1 to switch 2 of system 1 of rack 2, switch 2 of system 1 of rack 2 to switch 3 of system 2 of rack 2, and switch 3 of system 2 of rack 2 to node B of system 2 of rack 2).

[0156] For example, in rack 1, a switch in system 1 can send a signal with wavelength 1 to other systems in rack 1 via loop optical network 1202a; a switch in system 2 can send a signal with wavelength 2 to other systems in rack 1 via loop optical network 1202a, and so on. A switch in system 1000 of rack 1 can communicate with other systems 1000 in rack 1 via loop optical network 1202a using wavelengths 1 to 8, and communicate with other systems 1000 in racks 2 to 8 via wavelength 9. In rack 2, a switch in system 1 can send a signal with wavelength 2 to other systems in rack 2 via loop optical network 1202b; a switch in system 2 can send a signal with wavelength 3 to other systems in rack 2 via loop optical network 1202b, and so on. The switches in system 1000 of rack 2 can communicate with other systems 1000 in the same rack using wavelengths 2 to 9 on loop optical network 1202b, and with other systems 1000 in racks 1 and 3 to 8 using wavelength 1. The switches in system 1000 of rack 3 can communicate with other systems 1000 in rack 3 using wavelengths 3 to 9 and 1 on loop optical network 1202c, and with other systems 1000 in racks 1, 2 and 4 to 8 using wavelength 2, and so on.

[0157] In some implementations, multiple optically coupled multi-node computing systems can be formed on multiple corresponding layers of a substrate to increase the node density in a given volume. For example, a first optically coupled multi-node computing system can be formed on a first layer or a first set of layers in the substrate, and a second optically coupled multi-node computing system can be formed on a second layer or a second set of layers in the substrate. For example, each multi-node computing system includes N nodes, so the two multi-node computing systems have a total of 2N nodes. The first node, having circuitry in the first layer or the first set of layers, includes transmitter and receiver modules on the second layer or the second set of layers, which allow the first node to communicate with nodes on the second layer or the second set of layers via a loop optical network in the second layer or the second set of layers. The circuitry of the first node on the first layer or the first set of layers is electrically coupled to the transmitter and receiver modules on the second layer or the second set of layers via vertical contacts (such as vias). This design allows any node among the 2N nodes to optically communicate with any node among the other 2N nodes via one of the optical networks in the first and second optically coupled multi-node computing systems. In a similar manner, three or more optically coupled multi-node computing systems can be formed on three or more corresponding layers or groups of layers of a substrate.

[0158] In some examples, multiple optically coupled multi-node computing systems can be formed on multiple corresponding substrates stacked vertically to increase the node density in a given volume. For example, a first optically coupled multi-node computing system can be formed on a first substrate, and a second optically coupled multi-node computing system can be formed on a second substrate. For example, each multi-node computing system includes N nodes, so the two multi-node computing systems have a total of 2N nodes. The first node on the first substrate includes transmitter and receiver modules on the second substrate, which allow the first node to communicate with nodes on the second substrate via a loop optical network on the second substrate. The circuitry of the first node on the first substrate is electrically coupled to the transmitter and receiver modules on the second substrate via vertical contacts extending vertically across the first and second substrates. This design allows any node in the 2N nodes to optically communicate with any node in the other 2N nodes via one of the optical networks in the first and second optically coupled multi-node computing systems. In a similar manner, three or more optically coupled multi-node computing systems can be formed on three or more corresponding substrates.

[0159] In some implementations, having Figures 1B to 8B Any of the optically coupled multi-node computing systems shown in the diagram can be formed on multiple corresponding layers or groups of layers in a substrate, or on multiple substrates stacked vertically together, or on a combination thereof.

[0160] The number of nodes and optical loops in a multi-node computing system can differ from the example above. For instance, n1 horizontal optical loops (with parallel straight waveguide segments extending in the x-direction) and n2 vertical optical loops (with parallel straight waveguide segments extending in the y-direction) can be used, where n1 differs from n2.

[0161] Some of the systems, components, and / or functional operations described in this specification may be implemented in digital electronic circuits, or computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in a combination of one or more of them. Embodiments of the subject matter described in this specification may be implemented using one or more modules of computer program instructions encoded on a computer-readable medium for execution by or control of the operation of a data processing apparatus. The computer-readable medium may be a manufactured product such as a hard disk drive in a computer system or an optical disc sold through retail channels, or an embedded system. The computer-readable medium may be separately acquired and subsequently encoded with one or more modules of computer program instructions, such as by transmitting one or more modules of computer program instructions over a wired or wireless network. The computer-readable medium may be a machine-readable storage device, a machine-readable storage substrate, a memory device, or a combination of one or more of the above.

[0162] Computer programs (also known as programs, software, software applications, scripts, or code) can be written in any form of programming language, including compiled or interpreted languages, declarative or procedural languages, and can be deployed in any form, including as standalone programs or as modules, components, subroutines, or other units suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored as a part of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), as a single file dedicated to said program, or as multiple coordinating files (e.g., a file storing one or more modules, subroutines, or code sections). Computer programs can be deployed to execute on a single computer or on multiple computers located at a site or distributed across multiple sites and interconnected via a communication network.

[0163] The processes and logic flows described in this specification can be executed by one or more programmable processors that execute one or more computer programs to perform functions by manipulating input data and producing outputs. These processes and logic flows can also be executed by dedicated logic circuitry, and the device can be implemented as dedicated logic circuitry, such as FPGAs (Field-Programmable Gate Arrays) or ASICs (Application-Specific Integrated Circuits).

[0164] Although this disclosure has been described in conjunction with certain embodiments, it should be understood that this disclosure is not limited to the disclosed embodiments, but rather is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, the scope of which should be interpreted in the broadest possible sense to include all such modifications and equivalent structures permitted by law.

Claims

1. A device for communication, comprising: An integrated circuit, comprising multiple nodes coupled to an optical network, each node comprising: An optical transmitter interface is configured to transmit optical signals at locations along the coupled optical path of the optical network, and An optical receiver interface is configured to receive optical signals at a location along the coupled optical path of the optical network; The first optical path of the optical network includes at least a portion fabricated in at least one layer of the integrated circuit and configured to propagate a guided mode around a closed path; and The second optical path of the optical network includes at least a portion of a guided mode fabricated in at least one layer of the integrated circuit and configured to propagate around a closed path. in: The first optical path and the second optical path overlap each other at four locations in the first group on the integrated circuit. The first optical path couples to two or more nodes of the plurality of nodes at a second set of corresponding locations on the integrated circuit that are different from all locations in the first set of locations, and The second optical path is coupled to two or more of the plurality of nodes at a third corresponding position on the integrated circuit, which is different from all positions in the first group of positions and the second group of positions.

2. The apparatus according to claim 1, wherein, The first optical path includes at least a first straight segment and a second straight segment parallel to each other, wherein at least one of the plurality of nodes is coupled along the first straight segment at two or more locations in the second group, and at least one of the plurality of nodes is coupled along the second straight segment at two or more locations in the second group.

3. The apparatus according to claim 2, wherein, The first optical path and the second optical path overlap each other at four locations in the first group without switching the optical signal between the first optical path and the second optical path at any of the four locations in the first group.

4. The apparatus according to claim 3, wherein, At at least one of the four locations in the first group, a portion of the first optical path in the first layer of the integrated circuit overlaps with a portion of the second optical path in the second layer of the integrated circuit.

5. The apparatus according to claim 4, wherein, At at least one location on the integrated circuit, a portion of the second optical path is in the first layer of the integrated circuit.

6. The apparatus according to any one of claims 3 to 5, wherein, At least one of the plurality of nodes is coupled to the first optical path at one or more locations in the second set of locations, and is coupled to the second optical path at one or more locations in the third set of locations.

7. The apparatus according to claim 2, wherein, The first optical path and the second optical path overlap each other, wherein at least one switch is configured to switch the optical signal between the first optical path and the second optical path at at least one of the four positions in the first group.

8. The apparatus according to claim 7, wherein, The first optical path and the second optical path are fabricated in the same layer of the integrated circuit.

9. The apparatus according to claim 7 or 8, wherein, The switch includes at least two waveguide ring resonators located near one of the four positions in the first group where the first optical path and the second optical path overlap.

10. The apparatus according to any one of claims 1 to 5, 7 to 8, further comprising: The third optical path of the optical network includes at least a portion of a guided mode fabricated in at least one layer of the integrated circuit and configured to propagate around a closed path. as well as The fourth optical path of the optical network includes at least a portion of a guided mode fabricated in at least one layer of the integrated circuit and configured to propagate around a closed path. in: The third optical path and the fourth optical path overlap each other at the fourth set of four locations on the integrated circuit. The third optical path is coupled to two or more nodes of the plurality of nodes at a fifth corresponding position on the integrated circuit that is different from all positions in the first group of positions, the second group of positions, the third group of positions, and the fourth group of positions, and The fourth optical path is coupled to two or more nodes in the plurality of nodes at a sixth corresponding position on the integrated circuit that is different from all positions in the first group of positions, the second group of positions, the third group of positions, the fourth group of positions, and the fifth group of positions.

11. The apparatus according to any one of claims 1 to 5, 7 to 8, wherein, The integrated circuit is a first integrated circuit, and the device includes a second integrated circuit, the second integrated circuit including a plurality of nodes coupled to the optical network.

12. The apparatus according to claim 11, wherein, The first optical path of the optical network includes at least a portion fabricated in at least one layer of the second integrated circuit.

13. The apparatus according to claim 12, wherein, The device includes a third integrated circuit, which includes multiple nodes coupled to the optical network.

14. The apparatus according to claim 13, wherein, The second optical path of the optical network includes at least a portion fabricated in at least one layer of the third integrated circuit.

15. The apparatus according to any one of claims 1 to 5, 7 to 8, 12 to 14, wherein, At least one of the plurality of nodes coupled to the first optical path is configured to transmit an optical signal using a first optical wavelength, and at least one of the plurality of nodes coupled to the first optical path is configured to transmit an optical signal using a second optical wavelength different from the first optical wavelength.

16. The apparatus according to any one of claims 1 to 5, 7 to 8, 12 to 14, further comprising a controller configured to schedule the transmission of optical signals between the nodes, wherein, The controller is configured to set the first node as a transmitter during a first time period and to prevent other nodes from transmitting signals on the optical path coupled to the first node during the first time period.

17. The apparatus according to any one of claims 1 to 5, 7 to 8, 12 to 14, wherein, Each of at least some of the nodes includes at least one of a central processing unit, a graphics processing unit, a tensor processing unit, a digital signal processor, or a matrix processor.

18. An apparatus for communication, comprising: Multiple nodes are coupled to the optical network, each node including: An optical transmitter interface is configured to transmit optical signals at locations along the coupled optical path of the optical network, and An optical receiver interface is configured to receive optical signals at a location along the coupled optical path of the optical network; The first optical path of the optical network is configured to propagate a guided mode around a closed path; and The second optical path of the optical network is configured to propagate a guiding pattern around a closed path. Wherein, the first optical path and the second optical path overlap each other at four positions in the first group, the first optical path couples to two or more nodes in the node at corresponding positions in the second group that are different from the positions in the first group, and the second optical path couples to two or more nodes in the node at corresponding positions in the third group that are different from all the positions in the first group and the second group.

19. The apparatus according to claim 18, wherein, The first optical path and the second optical path overlap each other at four locations in the first group without switching the optical signal between the first optical path and the second optical path at any of the four locations in the first group.

20. The apparatus according to claim 18, wherein, The first optical path and the second optical path overlap each other, wherein at least one switch is configured to switch the optical signal between the first optical path and the second optical path at at least one of the four positions in the first group.

21. The apparatus according to any one of claims 18 to 20, wherein, The node, the first optical path, and the second optical path are disposed on a single substrate.

22. The apparatus according to any one of claims 18 to 20, wherein, At least some of the nodes include an integrated circuit.

23. The apparatus according to any one of claims 18 to 20, comprising an integrated circuit, wherein, The node is part of the integrated circuit.

24. The apparatus according to claim 21, wherein, The first optical path and the second optical path comprise planar waveguides formed on a single substrate.

25. The apparatus according to any one of claims 18 to 20, wherein, The first subgroup of the node, the first portion of the first optical path, and the first portion of the second optical path are disposed on the first substrate; as well as The second subgroup of the node, the second part of the first optical path, and the second part of the second optical path are disposed on the second substrate.

26. The apparatus according to claim 25, wherein, At least a portion of the first optical path includes a planar waveguide formed on the substrate.

27. The apparatus according to claim 26, wherein, At least a portion of the second optical path includes a planar waveguide formed on the substrate.

28. An apparatus for communication, comprising: An array including multiple nodes; An optical network includes a first optical path and a second optical path, wherein the first optical path is configured to propagate a guided pattern around a first closed path and is optically coupled to a plurality of nodes in the array, and the second optical path is configured to propagate a guided pattern around a second closed path and is optically coupled to a plurality of nodes in the array. The plurality of nodes includes a first node and a second node. The first optical path and the second optical path overlap each other at at least two positions in a first group. The first optical path is coupled to two or more nodes in the node at corresponding positions in a second group that are different from the positions in the first group. The second optical path is coupled to two or more nodes in the node at corresponding positions in a third group that are different from all the positions in the first group and the second group.

29. The apparatus of claim 28, further comprising a controller configured to schedule the transmission of optical signals between nodes via the optical network, the controller being configured to set a first node as a transmitter and set a first switch to a transmission state or a switching state during a first time period, the first node being configured to transmit optical signals via the first switch through the first optical path during the first time period, and the controller being configured to prevent other nodes from transmitting signals on the first optical path during the first time period.

30. The apparatus according to claim 28 or 29, wherein, The first node is configured to transmit an optical signal at a first wavelength around the first optical path in a first direction, and at least one node coupled to the optical network is configured to couple substantially all remaining optical power at the first wavelength from the first optical path to prevent interference with the optical signal at the first wavelength transmitted by the first node.

31. The apparatus according to claim 28 or 29, wherein, The first node includes: an optical transmitter interface configured to transmit a first optical signal at a first wavelength along a portion of the first closed path, and to transmit a second optical signal at a second wavelength along a portion of the first closed path; and An optical receiver interface configured to receive an optical signal at a third wavelength from a location along the first closed path.

32. The apparatus according to claim 31, wherein, The second node includes: an optical transmitter interface configured to transmit an optical signal at the third wavelength along a portion of the first closed path, and configured to transmit an optical signal at the second wavelength along a portion of the first closed path; and An optical receiver interface configured to receive an optical signal at the first wavelength from a location along the first closed path.

33. The apparatus according to claim 32, wherein, The plurality of nodes includes a third node, the third node comprising: an optical transmitter, the optical transmitter interface being configured to transmit an optical signal at the first wavelength onto the first closed path, and being configured to transmit an optical signal at the third wavelength onto the first closed path, and... An optical receiver interface configured to receive an optical signal at the second wavelength from a location along the second closed path.

34. The apparatus according to any one of claims 28 to 29, 32 to 33, wherein, The plurality of nodes includes at least a first node, a second node, and a third node coupled to the first closed path, and the plurality of nodes are configured to communicate on the first optical network using a plurality of wavelengths including at least a first wavelength, a second wavelength, and a third wavelength.

35. The apparatus according to claim 34, wherein, The first node includes: An optical transmitter interface configured to transmit a first optical signal at the first wavelength onto the first closed path. An optical receiver interface configured to simultaneously detect a second optical signal at a second wavelength and a third optical signal at a third wavelength from the first closed path, and A demodulation circuit coupled to the optical receiver interface of the first node and configured to determine, for a plurality of time slots, a mapping between a plurality of amplitude levels detected during the time slots and binary symbols modulated onto each of the second and third optical signals.

36. The apparatus according to claim 35, wherein, The second node includes: An optical transmitter interface configured to transmit the second optical signal onto the first closed path. An optical receiver interface configured to simultaneously detect multiple optical signals at wavelengths different from the second wavelength from the first closed path, and A demodulation circuit coupled to the optical receiver interface of the second node and configured to determine, for a plurality of time slots, a mapping between a plurality of amplitude levels detected during the time slots and binary symbols modulated onto each of the plurality of optical signals detected by the optical receiver interface of the second node.

37. A method for communication, comprising: Optical signals are transmitted from the first node to the second node via an optical network, each node comprising: An optical transmitter interface configured to transmit optical signals at locations along a coupled optical path of the optical network, and An optical receiver interface configured to receive optical signals at a location along the coupled optical path of the optical network; Closed-path propagation guidance mode around the first optical path of the optical network; and Closed-path propagation guidance mode around the second optical path of the optical network; Wherein, the first optical path and the second optical path overlap each other at four positions in the first group, the first optical path couples to two or more nodes in the node at corresponding positions in the second group that are different from the positions in the first group, and the second optical path couples to two or more nodes in the node at corresponding positions in the third group that are different from all the positions in the first group and the second group.

Images