Transceiver-switch device

Abstract

There is provided a transceiver-switch device (16, 20, 40), for communicating data in 5 an optical network (19, 95), the network (19) comprising a plurality of nodes (90, 92, 94) connected by optical signal paths, the device (16, 20, 40), provided at one node of said plurality of nodes (90, 92, 94), being configured to execute selection of optical wavelength, time of communication, and optical signal path, for communication of data in the optical network (19, 95) to and from said node, and wherein said device (16, 20, 10 40) is provided in a single physical module.

Description

[0001] TRANSCEIVER-SWITCH DEVICE

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a device for data communication in an optical network.

[0004] BACKGROUND OF THE INVENTION

[0005] Recently, the volume of data within cloud data centers, machine learning systems, high performance computing and telecommunication networks has accelerated in growth exponentially and significantly faster than the growth of network bandwidth supported by traditional electronic packet-switched networks. Scaling electronic networks to support the expanding datasphere incurs significant penalties in cost, power consumption, and latency, primarily due to the switches, which compel network engineers to limit overall network bandwidth. One of the fundamental challenges is to deliver highly energy-efficient networks that scale to support the ever-increasing application demands, which is inherently possible with optical networks (due to wavelength-division multiplexing (WDM) and novel modulation techniques) . In conventional networking strategy, the transceiver and switches are kept as two separate devices performing different functions. However, there is a problem that additional complexity is added to the core of the network, requiring it to be active and, in some cases, provide memory elements (there is no optical memory).

[0006] Conventional optical transceivers are designed for high-bandwidth point-to- point transmission but are not designed for switching, because dedicated switches handle that function at the core of the network. Even commercially available wavelength-tunable optical transceivers take hundreds of milliseconds to seconds to tune, resulting in significant idle periods, and are unsuitable for packet -speed switching, which requires switching in just a few nanoseconds. Consequently, they are used in tandem with existing electronic switches.

[0007] The present invention has been devised in view of the above problems.

[0008] SUMMARY OF THE INVENTION

[0009] According to a first aspect of the invention there is provided a transceiver-switch device, for communicating data in an optical network, the network comprising a plurality of nodes connected by optical signal paths, the device, provided at one node of said plurality of nodes, being configured to execute selection of optical wavelength, time of communication, and optical signal path, for communication of data in the optical network to and from said node, and wherein said device is provided in a single physical module.

[0010] Further optional features are defined in the dependent claims.

[0011] Embodiments of the invention can overcome these networking challenges and satisfy the overall bandwidth requirements by combining both transceivers and switches functionality within the same device, largely simplifying the core and making it passive.

[0012] The invention described in this patent combines both transceiver and switching capabilities within a single transceiver-switch device, that can switch in up to three dimensions: wavelength (sub-microsecond speed tuning), space (path selection) and time (sub-ns speed switching). This invention will bring the optical switching capability to each transceiver at the edge of the network (processor, memory and storage device), which will eliminate or reduce the switching at the core of the network. Embodiments of the invention combine wavelength tuning with space and time switching (defined and fine-tuned to specific tuning speeds) and develops a method to achieve end-to-end networking (transmit, switch and receive) at the edge. Preferred embodiments of the invention are unique because they combine and co-locate in one or a group of silicon integrated photonic (SiP) circuits with high-bandwidth transmission and ultra-fast switching capability.

[0013] As shown in Fig. IB, one option of use for the opto-electronic transceiver-switch is with existing electronic switches in order to by-pass layers of electronic switches in existing networks, significantly reducing latency and power. Another option is to replace the core altogether with a passive optical core, for example according to one of the configurations disclosed in GB2624660; this can completely transform the landscape of current networks creating a significant step -change advance.

[0014] In further preferred embodiments of the invention, a clock signal is copropagated along with data in the opto-electronic transceiver-switch. Data, such as digital data, is usually encoded using well-defined timing constraints governed by a reference clock at a transmitting node. The overall end-to-end switching latency also includes the clock and data recovery (CDR) locking time in addition to the optical switching time. CDR locking time is incurred because, unlike the continuous point-to- point interconnections between electronic packet switches, a new physical -layer link is established every time an optical switch is reconfigured to transmit a new data packet. The conventional receiver therefore needs to recover a new clock every time this occurs . Embodiments that employ co-propagating clock with the data by-passes the need for CDR circuitry, because the co-propagated clock is used to sample the data at the receiver.

[0015] DESCRIPTION OF THE DRAWINGS

[0016] Embodiments of the invention will now be described, by way of non -limiting example, with reference to the accompanying drawings. The invention may further comprise, in any combination, any features of the embodiments which will now be described.

[0017] Fig. 1A illustrates a conventional data center network;

[0018] Fig. IB illustrates an optical network employing transceiver -switch devices according to an embodiment of the invention;

[0019] Fig. 1C illustrates an example of an all-optical network employing transceiver - switch devices according to an embodiment of the invention;

[0020] Fig. 2A shows an opto-electronic transceiver-switch device according to a first embodiment of the invention, configured as follows:

[0021] Transmission path: x*lasers + modulator + IxN switches + amplifiers) ;

[0022] Reception path: x*(Nxl switches + N optical amplifiers + Photodiodes) ;

[0023] Fig. 2B shows an opto-electronic transceiver-switch device according to a second embodiment of the invention, configured as follows :

[0024] Transmission path: Same as first embodiment in Fig. 2A + additional channel for clock co-propagation i.e. additional laser + modulator + l :x splitter + amplifier;

[0025] Reception path: Same as first embodiment in Fig. 2A + additional channel for clock co-propagation i.e. additional l :x combiner + amp + filter + photoreceiver;

[0026] Fig. 3A shows an opto-electronic transceiver-switch device according to a third embodiment of the invention, configured as follows :

[0027] Transmission path: x*(lasers + modulators) + multiplexer / combiner + IxN switch + amplifiers;

[0028] Reception path: Nxl switch + N optical amplifiers + x*(Demultiplexer / Filter + Photodiodes);

[0029] Fig. 3B shows an opto-electronic transceiver-switch device according to a fourth embodiment of the invention, configured as follows:

[0030] Transmission path: Same as third embodiment in Fig. 3A + additional channel for clock co-propagation i.e. additional laser + modulator;

[0031] Reception path: Same as third embodiment in Fig. 3 A + additional channel for clock co-propagation i.e. additional photoreceiver; Fig. 4A shows an opto-electronic transceiver-switch device according to a fifth embodiment of the invention, configured as follows :

[0032] Transmission path: Same as first embodiment in Fig. 2A + additional couplers + MxN switches;

[0033] Reception path: Same as first embodiment in Fig. 2A + splitter (or bridge) from Receiver to the MxN switch in the transmitter path in order to re-transmit;

[0034] Fig. 4B shows an opto-electronic transceiver-switch device according to a sixth embodiment of the invention, configured as follows :

[0035] Transmission path: Same as fifth embodiment in Fig. 4A + additional channel for clock co-propagation i.e. additional Laser + Modulator + l :x splitter + amplifier;

[0036] Reception path: Same as fifth embodiment in Fig. 4 A + additional channel for clock copropagation i.e. additional l :x combiner + amplifier + filter + Photo receiver; and

[0037] Fig. 5 illustrates a working principle of an opto-electronic transceiver-switch device in a WDM / TDM based network.

[0038] In the drawings, like parts are in some instances indicated with like reference numerals, and, for conciseness, description thereof will not be repeated. Terms such as “optical” and “light” used herein do not limit the subject matter in any way to visible light, but encompass any suitable region of the electromagnetic spectrum, including at least infra-red (IR), visible, and ultra-violet (UV), and can be considered equivalent to a term such as “photonic”.

[0039] DETAILED DESCRIPTION OF THE INVENTION

[0040] Fig. 1A shows an example of an arrangement of servers 10 in racks 12 within current electronic data center networks, and Fig. IB illustrates how a transceiver-switch device 14 embodying the invention can be used to improve the performance of the network. As shown Fig. 1A, each rack 12 connects to a standard electronic top-of-rack switch 13 using transceivers Tx / Rx 14. After the packet is processed within the switch 13, the output of these switches 13 connects to a higher layer of switches 15 using another set of transceivers Tx / Rx 13. In this multi-tiered approach, a packet from a source server reaches a destination server after hopping and traversing across multiple electronic switches 13, 15.

[0041] As shown in Fig. IB, each of the network end-points can use an opto-electronic transceiver-switch (1 :N Tx-Rx-Sw) device 16, which can optionally be configured to use an optical bridge in order to completely by-pass an entire hop, resulting in reduced operation cost, power consumption and latency. Alternatively, as shown in Fig. 1C, the electronic switches 13, 15 can be replaced with an all-optical network 19, such that data is communicated between servers entirely in the optical domain, without being converted to the electrical domain for switching (and is only converted in the transceiver-switch device 16 at each server). Note that in Figs. IB and 1C, not all optical connections have been shown; this is in order to simplify the illustration for legibility. For example, the transceiver switch device 16 at the top of each rack 12 of servers 10 is illustrated as being fully connected to each other server 10 in its rack 12, and is connected to the network. In a preferred embodiment, every transceiver-switch device (1 :N Tx-Rx-Sw) 16 of each server 10 is optically connected to the transceiver switch device of every other server in its rack (these connections are not shown) as well as being connected to the network (either switch 13 or optical network 19).

[0042] Fig. 2A shows an opto-electronic transceiver-switch device 20 of a first embodiment, which equips the transceiver with a space / time switching capability when installed at a network node. Within each device 20 (also referred to as a module), there are up to x transmitters 22, each of which is composed of a laser source 24 (fixed wavelength, fixed bank of multiple wavelengths, or tunable wavelength), a modulator 26, where high-speed RF data is modulated onto the optical carrier, and a IxN switch + amplifier 28. At every reconfiguration, the IxN switch is configured to select one of N output ports (or paths), the amplifier amplifies the signal to optimum power to support a specified link budget and the modulated optical data signal is sent across the network via a path based on the switch configuration. The IxN switch can select one output port, many output ports, or all output ports, thereby allowing the support of unicast, multicast or broadcast transmission to up to N output ports (routes).

[0043] On the reception side, within each device 20, there are up to x receivers 30 and within each receiver 30, there is a IxN switch 31 , which enables the selection of source from where data is to be received, with an optional amplifier, which boosts the signal to the required power level, a tunable or fixed filter 32 separates the received data channel, and a dedicated photo-receiver 33, which is used to convert the data signal back to its electronic form.

[0044] Fig. 2B shows a second embodiment of the opto-electronic transceiver-switch device, which is like the first embodiment (see Fig. 2A), but in addition co-propagates clock along with data. In addition to the structure shown in Fig. 2A, a dedicated laser source 34 (labelled Taser y’) is used, which operates at a wavelength that is different from all data wavelengths, and a modulator 35 (channel y) is used to modulate the laser light with the clock CLK and generate the optical clock signal. A “l :x splitter and amplifier” 36 splits, amplifies and distributes the clock signal across to all data paths, where a multiplexer / combiner (not shown) combines clock and data to be co -propagated and sent across the network. The amplifier part in the splitter and amplifier 36 is optional.

[0045] At the receiver a dedicated splitter (not shown) is used to tap off a copy of the optical clock signal, which is sent via a x: l combiner 37 to a dedicated filter 38 (fixed or tuned) and photo-receiver 39, which are used to convert the optical clock signal back to its electronic form and which is then used as the reference clock to sample the data, eliminating the requirement or use of CDR circuitry in the receiver.

[0046] Fig. 3A shows a third embodiment of the transceiver-switch device, which equips the transceiver with a wavelength / space / time switching capability when installed at a network node. Within each device 40, there are up to x transmitters labelled Tx-1 to Tx-x, each of which is composed of a laser source 44 (fixed wavelength, fixed bank of multiple wavelengths, or tunable wavelength), and a modulator 46 , where high-speed RF data is modulated onto the optical carrier. A multiplexer 48 multiplexes (combines) the x optical signals onto a single medium (e.g. waveguide) which is followed by a single IxN switch 50, allowing two dimensions of switching: wavelength and path.

[0047] Within the receiver section, there is one IxN switch and amplifier 52, which selects the source from where data is to be received and amplifies the signals to the required power level. One demultiplexer / filter 54 separates the received group of x data, each at a unique wavelength and sends them onto up to x data photo receivers 56, which are used to convert the data signal back to its electronic form.

[0048] Fig. 3B shows a fourth embodiment of the transceiver-switch device, which is like the third embodiment, but in addition co-propagates clock along with data. In addition to the structure shown in Fig. 3A, a dedicated laser source 34 is used, which operates at a wavelength that is different from all data wavelengths, and a modulator 35 (channel y) is used to modulate the laser light with the clock CLK and generate the optical clock signal. The clock signal is also sent to the multiplexer / combiner 48 and co-propagated along with the optical data signals.

[0049] At the receiver, the demultiplexer / filter 54 has an additional dedicated channel for clock, which has a dedicated filter (fixed or tuned) and photo -receiver 39, which is used to convert the optical clock signal back to its electronic form and which is then used as the reference clock to sample the data, eliminating the requirement or use of CDR circuitry in the receiver. Fig. 4A shows a fifth embodiment of the transceiver-switch device, essentially the same as the embodiment in Fig. 2A, but where an additional optical loopback 60 is created from the receiver path 62 to the transmitter path 64 in order to facilitate data retransmission without the need for electronic packet processing. This is achieved by providing an MxN switch 66 in the receiver path 62 and an MxN switch 68 in the transmitter path 64. This bridging or loopback is performed by controlling the MxN switch in the receiver path 62 to select between the multiple received channels to be bridged and controlling the MxN switch in the transmitter path to select between the multiple transmitted channels to be sent across. Typically, the number of optical output channels for each transmitter-switch (Tx-Sw) is N, and the number of optical input channels for each receiver-switch (Rx-Sw) is also N (although these do not have to be the same value N); each MxN switch can connect any of the N channels to any one of M optical paths (M does not have to be the same as N, and M is typically less than N) - a number of these M optical paths are connected to the adjacent MxN switch via the optical loopback 60, and the remainder of the paths are ultimately connected to the respective laser or photoreceiver.

[0050] Fig. 4B shows a sixth embodiment of the transceiver-switch device, which is like the fifth embodiment, but in addition co-propagates clock along with data. In addition to the structure shown in Fig. 4A, a dedicated laser source 34 (labelled laser y) is used, which operates at a wavelength that is different from all data wavelengths, and a modulator 35 is used to modulate the laser light with the clock CLK and generate the optical clock signal. A “l :x splitter and amplifier” 36 splits, amplifies and distributes the clock signal across to all data paths, where a multiplexer / combiner 80 combines optical clock and optical data signals to be co-propagated and sent across the network.

[0051] At the receiver a dedicated splitter 82 is used to tap off a copy of the optical clock signal, which is sent to a dedicated filter 38 (fixed or tuned) and photo-receiver 39, which are used to convert the optical clock signal back to its electronic form and which is then used as the reference clock to sample the data, eliminating the requirement or use of CDR circuitry in the receiver.

[0052] Fig. 5 shows schematically how communication is time-division multiplexed for unique source nodes in a network. If and when the same wavelengths have to be used by different source nodes in a network due to destination node availability, they are time division multiplexed. For example, the figure shows how a single destination node 90 receives data from multiple source nodes 92, 94 using the same wavelengths over time across an optical network 95. In this example, each node comprises a transceiver- switch as already described with reference to Fig. 3B, but each could, for example, be according to any of Figs. 5 to 7. Figure 8 shows that transmitters of a first source (node 92) tune their data channels to wavelengths Al to Ax, and co-propagate clock in Ay in timeslot TO to communicate their data to the specified destination (node 90), shown on the right. In timeslot Tl , a second source (node 94) uses the same set of wavelengths Al to Ax for its data and Ax for its clock to communicate with the same destination. Both data and clock elements are received and processed by the receiving node 90 at different timeslots.

[0053] According to preferred implementations, specific exemplary details are as follows (each feature can be used separately or in any combination):

[0054] Laser wavelengths - Anywhere in O / S / C / L / E bands.

[0055] Laser tuning speed - sub-microseconds.

[0056] Modulation - NRZ or PAM4.

[0057] Clock frequency - 100-800 MHz.

[0058] Data rate / frequency - in the range of from 100 Gb / s / lane to 3.2 Tb / s / lane. Device packaging - Advanced silicon photonics.

[0059] Form factor - pluggable such as OSFP-XD or co-packaged or in-packaged optical engine.

[0060] The switching structures (such as IxN and MxN) - can comprise optical couplers / splitters or SMZI (Single-Photon Mach Zehnder Interferometer) or SOA (Semiconductor Optical Amplifiers) based sub-microsecond speed switches or an arrayed waveguide grating router (AWGR) which can be passive and cyclic.

[0061] Receiver filters - flat-top filter based on micro-ring resonators or MZIs (Mach Zehnder Interferometer) or grating or a combination thereof.

Claims

CLAIMS1. A transceiver-switch device, for communicating data in an optical network, the network comprising a plurality of nodes connected by optical signal paths, the device, provided at one node of said plurality of nodes, being configured to execute selection of optical wavelength, time of communication, and optical signal path, for communication of data in the optical network to and from said node, and wherein said device is provided in a single physical module.

2. A device according to claim 1 , wherein the module is pluggable.

3. A device according to claim 1 or 2, comprising at least one photonic integrated circuit and / or co-packaged optics module.

4. A device according to any preceding claim, comprising: a time selector for selecting a time slot for transmitting, from said one node, an optical data signal representing a unit of data; a wavelength selector for selecting an optical wavelength, from a plurality of selectable wavelengths, as the basis for propagating the optical data signal; a data convertor for converting an electrical signal representing the unit of data into said optical data signal; and a switching structure for switching the optical data signal to at least one selected port, from a plurality of selectable ports, for transmission over at least one optical path in the optical network to one other node or to a plurality of other nodes.

5. A device according to claim 4, further comprising a plurality of laser light sources for emitting different wavelengths to provide the plurality of selectable wavelengths.

6. A device according to claim 4, further comprising at least one tunable laser light source for emitting different wavelengths to provide the plurality of selectable wavelengths.

7. A device according to any of claims 4 to 6, further configured to transmit, simultaneously in a time slot, a plurality of optical data signals each using a unique pairing of wavelength and optical path, wherein the plurality of optical data signals represents a plurality of units of data.

8. A device according to any of claims 4 to 7, further comprising: an input for receiving a reference clock signal giving timing information for the unit of data; and a clock convertor for converting the reference clock signal to an optical clock signal, wherein the optical clock signal is at a wavelength offset by a predetermined amount from the wavelength selected for the optical data signal, wherein the device is arranged to co-propagate the optical clock signal simultaneously with the optical data signal via the at least one selected port and at least one optical path in the same time slot.

9. A device according to claim 8, further configured to co-propagate the optical clock signal simultaneously with a plurality of optical data signals propagated at different respective wavelengths, wherein the plurality of optical data signals represents a plurality of units of data, and wherein the optical clock signal represents timing information common to each of the plurality of units of data.

10. A device according to any of claims 4 to 9, wherein the data convertor comprises a modulator arranged to modulate light from a source at the selected optical wavelength by one of double-sideband modulation and single-sideband modulation.

11. A device according to any preceding claim comprising: a destination port, from among a plurality of ports of said one node, for receiving an optical data signal propagated over an optical path in the optical network in a specific time slot; a plurality of photo-receivers; a switching structure for directing the received optical data signal from said destination port on a route to at least one of said plurality of photo-receivers; a separator for optically separating the optical data signal, prior to reception by a respective photo-receiver that is arranged to convert the optical data signal to electrical form.

12. A device according to claim 11 , wherein the separator comprises at least one of: a fixed filter; a tunable filter; a wavelength demultiplexer.

13. A device according to claim 11 or 12 wherein: the destination port is configured for receiving simultaneously an optical data signal and an optical clock signal co-propagated over the same optical path in the optical network and in the same time slot; the switching structure is configured for directing the received signals from said destination port on a route to said plurality of photo-receivers; the separator is arranged to optically separating the optical data signal and the optical clock signal, such that each is detected by a different photo -receiver that respectively converts the optical clock signal and optical data signal to electrical form; and wherein the device further comprises: a data processing unit configured to use the electrical form of the detected clock signal as a reference clock signal to process the unit of data from the detected optical data signal.

14. A device according to any of claims 11 to 13, wherein the switching structure is further configured to enable an optical signal received at a destination port from a different node to be directed, in the optical domain, to at least one selected port, from a plurality of selectable ports, for onward transmission over at least one optical path in the optical network to one other node or to a plurality of other nodes.

15. A device according to any of claims 11 to 14, wherein the switching structure is further configured to enable a co-propagated optical data signal and optical clock signal received at a destination port from a different node to be directed, in the optical domain, to at least one selected port, from a plurality of selectable ports, for onward transmission over at least one optical path in the optical network to one other node or to a plurality of other nodes.

16. A device according to any one of claims 4 to 15, wherein the or each switching structure comprises at least one of: a splitter; a combiner; IxN switch; Nxl switch; MxN switch; an arrayed waveguide grating router, AWGR.

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