System for pulse laser light data transmission with receiver recoverable clock

Abstract

A system comprising an optical transmitter configured to modulate a pulsed laser signal based on a plurality of data signals to form a plurality of modulated optical data signals, to optically time-division multiplex the plurality of modulated optical data signals to obtain a multiplexed optical data signal, and to transmit the multiplexed optical data signal together with an optical clock signal derived from the pulsed laser signal; and an optical receiver comprising a clock recovery branch configured to recover the optical clock signal into a plurality of phase-shifted recovered optical clock signals and a data branch having a plurality of saturable absorbers (SAs), each SA in optical communication with one of the phase-shifted recovered optical clock signals and configured to receive the multiplexed optical data signal and to transmit one of the plurality of modulated optical data signals in accordance with the recovered optical clock signal.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 142,684, filed January 28, 2021, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The various system embodiments disclosed herein generally relate to signal transmission, and more specifically to systems for transmitting high data rate optical signals. Background Technology

[0004] Coherent and incoherent optical transceivers used for high data rate transmissions such as 400 Gbps and above typically employ digital signal processors (DSPs). The DSP provides one or more of the following to achieve such high rates: pre- or post-dispersion compensation, other channel impairments, multiplexing and demultiplexing, implementation of advanced modulation formats, and / or error correction, such as when using PAM4 (or other modulations).

[0005] The required DSPs are power-intensive—typically 8W for a DSP in a 400Gbps data rate system, or even higher for higher data rates, thus increasing the power demands of high-bit-rate systems. Furthermore, multiplexing of multiple data channels and additional signal processing of electrical signals introduce latency into signal transmission. Moreover, DSPs have a limited maximum processing capacity due to limitations in electrical processing. Therefore, it is desirable to provide a transmission system with high data rates without requiring a DSP, thereby reducing power consumption and latency and overcoming the electrical bandwidth bottleneck. Summary of the Invention

[0006] The embodiments disclosed herein relate to systems, apparatus, and methods for implementing high data rate optical signals with reduced power consumption and reduced latency. The systems described herein utilize all-optical transmitters and receivers, thereby eliminating the need for a DSP, which reduces the power requirements and latency of systems transmitting equivalent data rates. The all-optical transmitter-receiver arrangement also reduces computational complexity (such as that required by a DSP). In some embodiments, the all-optical transmitter and receiver are configured as integrated circuits (ICs) sharing a semiconductor substrate to further reduce power and size requirements.

[0007] To set up an all-optical receiver, a clock (local oscillator) used in the modulated signal of the transmission is required at the receiver. The presently disclosed system uses a modulated pulsed laser for data transmission, exploiting periodic pulses as a clock. The clock based on the pulsed laser is transmitted together with the data signal and recovered by the receiver, thereby serving as the required local oscillator. In some embodiments, orthogonal transverse modes are used, one carrying data and the other carrying the clock. In some embodiments, separate data and clock channels are transmitted to the receiver. To enable all-optical demodulation based on the received clock, the receiver advantageously comprises a saturable absorber (SA) configured to transmit the received data pulses when saturated by the clock pulses, thereby recovering the transmitted data signal.

[0008] In some embodiments, optical time-division multiplexing (OTDM) is set up for transmission of the multiple data channels. The use of optical multiplexing reduces latency and complexity compared to electrical multiplexing such as in DSPs. In some embodiments, the presently disclosed system can be repetitive, or can provide an integrated WDM system for transmission of a larger number of channels per optical fiber cable. In some embodiments, single-mode optical fiber cables are used with unidirectional operation. In some embodiments, full-duplex optical fiber cables are used with bidirectional operation. Furthermore, dispersion management is also handled optically in the receiver to compensate for dispersion in the transmission and dispersion that can be caused by the saturable absorber. As mentioned above, the use of dispersion management reduces the computational complexity of the solution.

[0009] In some embodiments, a system comprises: an optical transmitter comprising a pulsed laser for outputting a pulsed laser signal, wherein. The optical transmitter is configured to modulate the pulsed laser signal based on a plurality of data signals to form a plurality of modulated optical data signals, to perform optical time-division multiplexing on the plurality of modulated optical data signals to obtain a multiplexed optical data signal, and to transmit the multiplexed optical data signal together with an optical clock signal derived from the pulsed laser signal; and an optical receiver comprising a clock recovery branch and a data branch, wherein the clock recovery branch is configured to recover the optical clock signal and to phase shift it into a plurality of phase-shifted recovered optical clock signals, wherein the data branch comprises a plurality of SAs, and wherein each SA is in optical communication with one of the plurality of phase-shifted recovered optical clock signals and is configured to receive the multiplexed optical data signal and to transmit one of the modulated optical data signals received in the multiplexed optical data signal according to one of the plurality of phase-shifted recovered optical clock signals.

[0010] In some embodiments, the optical clock signal and the multiplexed optical data signals are transmitted by the optical transmitter in a single mode optical fiber cable in a quadrature transverse mode. In some embodiments, the optical clock signal and the multiplexed optical data signals are transmitted by the optical transmitter over separate cables in a full duplex optical fiber cable, respectively. In some embodiments, wherein a clock pulse from one of the plurality of phase-shifted recovered optical clock signals saturates the respective SA, causing the respective SA to release a pulse from one of the plurality of modulated optical data signals.

[0011] In some embodiments, the clock recovery branch includes a splitter and a phase shifter for extracting the optical clock signal into a plurality of phase-shifted extracted optical clock signals. In some embodiments, the optical receiver further includes one or more dispersion managers configured to perform dispersion correction on the plurality of modulated optical data signals and the plurality of phase-shifted extracted optical clock signals. In some embodiments, the optical receiver further includes an output component configured to extract a plurality of data signals from each of the plurality of modulated optical data signals.

[0012] In some embodiments, the pulsed laser is selected from the group consisting of bulk lasers, quantum well lasers, quantum dot lasers, semiconductor mode-locked lasers, and mode-locked integrated external cavity surface emitting lasers. In some embodiments, the pulsed laser has a pulse repetition rate between 5 GHz and 100 GHz. In some embodiments, the optical receiver includes an optical amplifier (OA). In some embodiments, the OA is a quantum dot semiconductor optical amplifier.

[0013] In some embodiments, the modulation is one of pulse amplitude modulation (PAM) or quadrature amplitude modulation (QAM). In some embodiments, the plurality of data signals includes 2-16 data signals per wavelength. In some embodiments, the plurality of data signals are digital signals and / or analog signals.

[0014] In some embodiments, a transmission system includes a first transceiver and a second transceiver, where each of the first transceiver and the second transceiver includes an optical transmitter, an optical receiver, and a controller, where each optical transmitter is configured to modulate a pulsed laser signal based on a plurality of data signals to form a plurality of modulated optical data signals, to optically time-division multiplex the plurality of modulated optical data signals to obtain a multiplexed optical data signal, and to transmit the multiplexed optical data signal with an optical clock signal derived from the pulsed laser signal, and where each optical receiver includes a clock recovery leg and a data leg, where the clock recovery leg is configured to recover the optical clock signal and phase shift it into a plurality of phase-shifted recovered optical clock signals, where the data leg includes a plurality of SAs, and where each SA is in optical communication with one of the plurality of phase-shifted recovered optical clock signals and is configured to receive the multiplexed optical data signal and transmit one of the modulated optical data signals received in the multiplexed optical data signal according to one of the plurality of phase-shifted recovered optical clock signals.

[0015] In some embodiments, each controller is configured to monitor transceiver performance and to perform adjustments of the transmitter and receiver to optimize transceiver performance. In some embodiments, the monitoring includes monitoring of one or more of bit error rate, data throughput, frame loss, or jitter. In some embodiments, each transceiver is formed on a common semiconductor substrate that is an IC.

[0016] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. BRIEF DESCRIPTION OF DRAWINGS

[0017] Embodiments disclosed herein are described, by way of example only, with reference to the following drawings, in which:

[0018] Figure 1A An optical system for data transmission over a single mode optical fiber is shown in accordance with some embodiments;

[0019] Figure 1B A transmitter for use with a single mode optical fiber is shown in accordance with some embodiments;

[0020] Figure 1C An illustrative signal amplitude plot of optical signals within a transmitter in accordance with some embodiments is shown;

[0021] Figure 1D A receiver for use with a single mode optical fiber is shown in accordance with some embodiments;

[0022] Figure 1EAn illustrative signal amplitude diagram of an optical signal within a receiver is shown in accordance with some embodiments;

[0023] Figure 1F And Figure 1G A plurality of optical transmission systems is shown in accordance with some embodiments;

[0024] Figure 2A An optical system for data transmission over a full duplex fiber is shown in accordance with some embodiments;

[0025] Figure 2B A transmitter for use with a full duplex fiber is shown in accordance with some embodiments;

[0026] Figure 2C A coupling assembly for use with a full duplex fiber is shown in accordance with some embodiments;

[0027] Figure 2D A receiver for use with a full duplex fiber is shown in accordance with some embodiments;

[0028] Figure 2E And Figure 2F A plurality of optical transmission systems is shown in accordance with some embodiments. DETAILED DESCRIPTION

[0029] Various aspects of the embodiments relate to systems, devices, and methods that enable high data rate optical signals with reduced power consumption, reduced latency, and reduced computational complexity. Figures 1A-1G An optical system for data transmission is shown in accordance with some embodiments. As shown in Figure 1A The optical transmission system 100 includes transceivers 108-1 and 108-2. Each transceiver 108 includes an optical transmitter 110, an optical receiver 140, and a controller 160.

[0030] The transmitter 110-1 is in optical communication with the receiver 140-2 over a single mode fiber optic cable 170-1 to transmit a unidirectional data signal 102, and the transmitter 110-2 is in optical communication with the receiver 140-1 over a single mode fiber optic cable 170-2 to transmit a unidirectional data signal 104. In some embodiments, a single fiber optic cable 170 can be used for bidirectional optical communication, such as by using different wavelengths to transmit the data signals 102 and 104. Data signals, such as the signals 102 and 104, are also referred to herein as “channels.” In some embodiments, each transceiver 108-1 and 108-2 is disposed as an integrated circuit (IC) on a shared semiconductor substrate.

[0031] The data signals 102, 104 are electrical data signals. In some embodiments, the data signals 102, 104 are digital signals, and the laser pulse repetition rate is equal to or greater than the digital signal rate. In some embodiments, the data signals 102, 104 are analog electrical signals, and the laser pulse repetition rate is equal to or greater than the Nyquist frequency of the analog electrical signal. In some embodiments, the data signals 102, 104 are a combination of digital and analog signals. For simplicity, Figures 1A-1G Transmission of two channels (data signals 102-1 and 102-2 and data signals 104-1 and 104-2) in each transmission direction is shown, but it will be appreciated that the system 100 can multiplex and transmit more than two channels. In some embodiments, 2-16 data signals per wavelength are supported.

[0032] The controller 160 is a computing device as defined herein. The controller 160-1 is in data communication with the transmitter 110-1 and the receiver 140-1, and the controller 160-2 is in data communication with the transmitter 110-2 and the receiver 140-2 to control each of the transceivers 108-1 and 108-2 for operation of the system 100 as described further below.

[0033] The components of each transmitter 110 are further described with reference to FIG. IB, and include a pulsed laser 112, a polarization splitter 114, a 3 dB splitter 116, a driver 118, an electro-optical (EG) modulator 120, a tunable phase shifter 122, a 3 dB coupler 124, a polarization coupler 126, and a pulse shaper 128. In some embodiments, the components of the transmitter 110 are formed on a common semiconductor as an IC.

[0034] The pulsed laser 112 provides a source pulsed laser signal for optical transmission of the data signal 102 that can be modulated based on the data signal 102. The pulsed laser signal is also used as a clock and transmitted with the modulated data to enable demodulation of the data signal. In some embodiments, the pulsed laser 112 operates at a fixed wavelength denoted here as λΐ. The pulsed laser 112 emits pulses at a periodic repetition frequency. In some embodiments, the pulsed laser 112 can be any of a bulk laser, a quantum well laser, a quantum dot laser, a semiconductor mode-locked laser, a high-power semiconductor laser, or a mode-locked integrated external cavity surface emitting laser. In some embodiments, the pulsed laser 112 can support a pulse repetition rate between 5 GHz and 100 GHz. In some embodiments, the pulsed laser 112 can support a pulse repetition between 100 GHz and 400 GHz.

[0035] Polarization splitter 114 splits the pulsed laser signal into orthogonal transverse modes. In system 100, one mode is used for data transmission and the other mode is used for clock transmission. Data is transmitted in the TE (Transverse Electric) mode on data branch 113 and clock is transmitted in the TM (Transverse Magnetic) mode on clock branch 111, or vice versa (data on TM and clock on TE). In some embodiments, polarization splitter 114 splits the pulsed laser signal intensity unequally between the two modes. Non-limiting examples of splitting ratios include 90 / 10 and 80 / 20. In some embodiments, polarization splitter 114 splits the pulsed laser signal equally between the two modes. Both modes can be expected to suffer the same distortions during transmission, with no impact on orthogonality.

[0036] In data branch 113, transmitter 112 provides OTDM of multiple data signals 102 (or 104). Exemplarily, two data signals 102-1 and 102-2 are shown, along with two drivers 118-1, 118-2 and two EO modulators 120-1, 120-2 for simplicity, but it is understood that multiple (more than two) data signals can be supported. 3dB splitter 116 splits the pulsed transverse mode laser signal according to the number of data signals supported (shown here as two). In some embodiments, each data signal 102 is input into transmitter 112 via a driver 118. Driver 118 can power EO modulator 120 and can adjust the electrical signal level of input data signal 102.

[0037] EO modulator 120 modulates the source pulsed laser signal based on input data signal 102. In some embodiments, EO modulator can include a digital-to-analog converter (DAC) (not shown) for processing analog electrical input. In some embodiments, the pulse (clock) rate, and thus the channel rate modulated by, is: R / (number of channels).

[0038] Various modulation schemes can be applied, including but not limited to pulse amplitude modulation (PAM) or quadrature amplitude modulation (QAM). Tunable phase shifter 122 shifts the phase of the second and other channels to obtain modulated (phase-shifted) channels (indicated as λ 1S1-MOD , λ 1S2-MOD，SHIFT ) such that the channel pulses will be interleaved when combined at 3dB coupler 124. Coupler 124 combines the modulated (phase-shifted) channels (indicated as λ 1S1-MOD , λ 1S2-MOD，SHIFT ) to form an OTDM output signal (indicated as λ 1OTDM ) of data branch 113, which has a pulse rate of: R x (number of channels).

[0039] Figure 1C Modulated (phase-shifted) channels (indicated as λ1S1-MOD , λ 1S2-MOD，SHIFT The combined OTDM output of data branch 113 (indicated by λ) and data branch 113 1OTDM ) and clock signal (indicated by λ) 1-CLOCK (Illustrative signal amplitude diagram)

[0040] Polarization coupler 126 combines the lateral modes of data branch 113 and clock branch 111 to form an orthogonal lateral signal to carry the OTDM output and clock, indicated by λ. 1OTDM+CLOCK In some embodiments, the pulse shaper 128 shapes and equalizes the pulse. 1OTDM+CLOCK The pulse height and shape are configured to form transmitter output 106. In some embodiments, pulse shaper 128 may be coupled to fiber optic cable 170. In some embodiments, pulse shaper 128 may be fed into a WDM multiplexer as further described below. In some embodiments, pulse shaping may be implemented using a filter bank. In some embodiments, pulse shaping may be implemented using nested unbalanced Mach-Zehnder interferometers (MZI), ring resonators, or a combination of MZI and ring resonators. Transmitter output 106 is transmitted toward receiver 140 over fiber optic cable 170.

[0041] In transmitter 110, controller 160 can monitor and control all components and provide automatic adjustment of adjustable components such as phase shifter 122, pulse shaper 128 and driver 118.

[0042] refer to Figure 1D The components of each receiver 140 are further described, and each receiver 140 may include an optical amplifier (OA) 142, a polarization separator 144, a separator 146, a polarization / phase controller (PC) 148, a tunable phase shifter 150, a dispersion manager 152, a saturable absorber (SA) 154, a driver 155, a circulator 156, and an output component 158. In some embodiments, the components of the receiver 140 may be formed as ICs on a common semiconductor substrate.

[0043] OA 142 boosts the signal received from transmitter 110. In some embodiments, OA 142 may be coupled to fiber optic cable 170. In some embodiments, OA 142 may be connected to a WDM demultiplexer as further described below. In some embodiments, OA 142 may be a quantum dot semiconductor optical amplifier with low power consumption and minimal crosstalk between different wavelengths. In some embodiments, driver 145 may power OA 142.

[0044] OA 142(λ 1OTDM+CLOCK) to a polarization splitter 144, which splits the received signal (λ 1OTDM+CLOCK ) into orthogonal transverse modes. The data modes (as defined in the transmitter, TM or TE) are transmitted on a data branch 141, and the clock modes (as defined in the receiver, TM or TE) are transmitted on a clock recovery branch 143. In some embodiments, the polarization splitter 144 splits the received signal unequally between the two modes. Non-limiting examples of split ratios include 90 / 10 and 80 / 20. In some embodiments, the polarization splitter 144 splits the received signal equally between the two modes.

[0045] Figure 1E Illustrative signal amplitude plots are shown for the combined OTDM signal (here denoted λ 1OTDM ) split within the data branch 141, the recovered clock and phase-shifted clock (here denoted λ 1-CLOCK , λ 1-CLOCK SHIFT ) of the clock branch 143, and the recovered modulated (phase-shifted) channels (here denoted λ 1S1-MOD , λ 1S2-MOD，SHIFT ).

[0046] In the data branch 141, a splitter 146-1 splits the OTDM according to the number of channels time-multiplexed by the transmitter 110. Thus, each branch of the data branch 141 carries λ 1OTDM . Similarly, in the clock branch 143, a splitter 146-2 splits the clock signal λ 1-CLOCK according to the number of channels time-multiplexed by the transmitter 110. As noted above, two OTDM channels and corresponding two clock channels are shown for simplicity, but it will be appreciated that multiple channels can be demultiplexed.

[0047] In some embodiments, polarization / phase controllers (PCs) 148 can be provided to match the polarization and correct for phase mismatches. Illustratively, a plurality of PCs 148-1..148-4 are provided, each on a separate signal or clock branch. Tunable phase shifters 150-1 and 150-2 shift the phase of the clock channels so that the clock pulses will be timed to coincide with the interleaved channels of the OTDM signal in the data branch 141. Each dispersion manager (DM) 152 can correct for dispersion in the optical channels that have affected the data and / or clock signals. Illustratively, a plurality of DMs 152-1..152-4 are provided, each on a separate branch. The DMs 152 can also introduce a pre-correction for the dispersion introduced by the SAs 154. In some embodiments, the DMs 152 can comprise chirped Bragg gratings controlled by a temperature controller 153. In some embodiments, drivers 155 can power the respective SAs 154.

[0048] Each output of the clock branch 143, denoted here as λ 1-CLOCK and λ 1-CLOCK SHIFT feeds into a respective circulator 156 in the data branch 141. Exemplarily, two circulators 156-1, 156-2, two SAs 154-1, 154-2, and two drivers 155-1, 155-2 are shown corresponding to two multiplexed data channels. In some embodiments, the circulators 156 can be non-reciprocal, unidirectional, three-port circulators. In Figure 1D the circulators 156 are shown with a clockwise direction, but it should be understood that the direction employed will be functional. In use, the clock input circulates to the SAs 154. In some embodiments, each SA 154 can be any of a quantum well (QW) semiconductor SA, a quantum dot SA, or a bulk semiconductor SA.

[0049] The clock pulse will saturate the SA 154, forcing the SA 154 to be transparent, thereby “releasing” or “transmitting” the current OTDM interleaved channel pulse through the SA 154 corresponding to the pulse period. Thus, λ 1-CLOCK and λ 1-CLOCK SHIFT will saturate the SAs 154-1 and 154-2, respectively, at different time periods, each corresponding to a separate OTDM channel, thereby releasing the current OTDM channel pulse through the SA 154. When the clock signal is between pulses (low clock signal), the SA 154 is not saturated, thereby blocking other OTDM channels. In some embodiments, each SA 154-1 or 154-2 provides an electrical output of each recovered clock 159-1 or 159-2.

[0050] The released OTDM pulse will enter the circulator 156 and will be circulated to an output component (OC) 158. Each OC 158 includes those components necessary to convert the released optical channel back to an electrical data signal 102. Exemplarily, two OCs 158-1, 158-2 are shown corresponding to two multiplexed data channels. The OC 158 can include one or more of a photodiode (PD) or PD array for opto-electric conversion, a trans-impedance amplifier (TIA), a DAC, and / or a limiting amplifier (LA).

[0051] In receiver 140, controller 160 can monitor and control all components and provide automatic adjustment of adjustable components such as phase shifter 150, OA 142, drivers 145, 155, and DM 152. In some embodiments, controller 160 monitors the performance of transceiver 108 based on one or more of parameters such as bit error rate, data throughput, frame loss, jitter, and then performs adjustments to adjustable components (in both transmitter 110 and receiver 140) to optimize transceiver 108 performance.

[0052] like Figure 1F As shown, in some embodiments, multiple systems 100-1, 100-2 to 100-X (where X = N / 2) may be provided in parallel, each system 100 operating on a separate pair of fiber optic cables 170-1 and 170-2. As further shown, each of the systems 100 may provide up to four channels of OTDM in each direction (102, 104). In some embodiments, more than four channels may be provided. Each of the systems 100-1, 100-2, and 100-X may be operated using a pulsed laser 112 having the same wavelength or different wavelengths or combinations of wavelengths.

[0053] like Figure 1G As shown, in some embodiments, multiple systems 100-1 to 100-X can be configured in parallel with wavelength division multiplexing (WDM) multiplexers 172-1 and 174-2 and demultiplexers 172-2 and 174-1, each multiplexer 172-1 and 174-2 operating on its respective single fiber optic cable 170-1 and 170-2. For WDM operation, each of systems 100-1, 100-2...100-N uses a corresponding pulsed laser 112 with a different wavelength. Figure 1G As further illustrated, each of the systems 100 can provide up to four channels of OTDM in each direction (102, 104). In some embodiments, more than four channels can be provided.

[0054] Figures 2A-2F An optical system for bidirectional data transmission over full-duplex optical fiber is illustrated according to some embodiments. For example... Figure 2A As shown, the optical transmission system 200 includes transceivers 208-1 and 208-2. Each transceiver 208 includes an optical transmitter 210, an optical receiver 240, a coupling assembly 209, and a controller 260.

[0055] Transmitter 210-1 is in fiber optic communication with receiver 240-2 over full duplex fiber optic cable 270 to transmit data signal 102 using a first wavelength (λ1), and transmitter 210-2 is in fiber optic communication with receiver 240-1 over full duplex fiber optic cable 270 to transmit data signal 104 using a second wavelength (λ2). In some embodiments, each of transceivers 208 is provided as an IC on a common semiconductor substrate.

[0056] Data signals 102, 104 are electrical data signals. In some embodiments, data signals 102, 104 are digital signals, and the laser pulse repetition rate is equal to or greater than the digital signal rate. In some embodiments, data signals 102, 104 are analog electrical signals, and the laser pulse repetition rate is equal to or greater than the Nyquist frequency of the analog electrical signal. In some embodiments, data signals 102, 104 are a combination of digital and analog signals. For simplicity, Figures 2A-2F Two channels of transmission are shown in each transmission direction (data signals 102-1 and 102-2 and data signals 104-1 and 104-2), but it will be appreciated that system 200 can transmit more than two channels. In some embodiments, 2-16 data signals per wavelength are supported.

[0057] Each controller 260 is a computing device as defined herein. Controller 260-1 is in data communication with transmitter 210-1 and receiver 240-1, and controller 260-2 is in data communication with transmitter 210-2 and receiver 240-2 to control each of transceivers 208-1 and 208-2 for operation of system 200, as further described below. In some embodiments, each of coupling assemblies 209-1, 209-2 is in data communication with its respective controller 260-1, 260-2.

[0058] Reference is made to Figure 2B The components of each transmitter 210 are further described and include pulsed laser 112, splitter 214, 3 dB splitter 116, driver 118, EO modulator 120, tunable phase shifter 122, 3 dB coupler 124, and pulse shaper 228. In some embodiments, the components of transmitter 210 are formed on a common semiconductor as an IC. Components of transmitter 110 of the same reference number are the same components and provide the same functionality in transmitter 210, and are therefore not described again.

[0059] Splitter 214 divides the pulsed laser signal into a data branch 213 for OTDM signal transmission and a clock branch 211 for clock transmission. In some embodiments, splitter 214 divides the pulsed laser signal intensity unequally between the two branches. Non-limiting examples of division ratios include 90 / 10 and 80 / 20. In some embodiments, splitter 214 divides the pulsed laser signal equally between the two branches.

[0060] In data branch 213, transmitter 212 provides OTDM for multiple data signals 102 (or 104). For simplicity, two data signals 102-1 and 102-2 are shown, but it should be understood that multiple data signals can be supported. Data branch 213 functions the same as system 100 and forms the OTDM output (denoted as λ) of data branch 233 with a pulse rate of R × (number of channels). 1OTDM ).

[0061] In some embodiments, the pulse shaper 228-1 shapes and equalizes the pulse. 1OTDM The pulse height and shape. In some embodiments, the pulse shaper 228-2 shapes and equalizes the pulse height and shape. 1-CLOCK The pulse height. In some implementations, pulse shaping can be achieved using filter banks. In some embodiments, pulse shaping can be achieved using nested unbalanced MZIs or ring resonators, or a combination of MZIs and ring resonators.

[0062] like Figure 2C As shown, the output of transmitter 210 is fed into coupling assembly 209. Each coupling assembly 209 includes a circulator 230 and a coupler 232. Pulse shaper 228-1 shapes λ... 1OTDM The pulse is fed to the optical circulator 230-1, and the pulse shaper 288-2 will... 1CLOCK The feed is sent to the optical circulator 230-2. In some embodiments, the circulator 230 may be a non-reciprocating, unidirectional, three-port circulator. Figure 2C In the diagram, the circulator 230 is shown in a clockwise direction, but it should be understood that the direction adopted will be functional.

[0063] One of the ports of circulator 230 is connected to coupler 232. Coupler 232-1 will output (Tx)λ 1OTDM The first optical fiber coupled into cable 270, and coupler 232-2 will output λ 1-CLOCK A second optical fiber is coupled to fiber optic cable 270. Input (Rx) clock and OTDM signal λ. 2OTDM and λ 2-CLOCKFrom the cable 270, away from the coupler 232 and directed by the circulator 230 to an outlet of the circulator 230, which is coupled to an input of the "same-side" receiver 240.

[0064] In the transmitter 210, the controller 160 can monitor and control all components and provide automatic adjustment of adjustable components such as the phase shifter 122, the pulse shaper 228, and the driver 118.

[0065] Reference is made to Figure 2D The components of each receiver 140 are further described and can include an optical amplifier (OA) 242, a splitter 146, a polarization / phase controller (PC) 148, a tunable phase shifter 150, a dispersion manager 152, a saturable absorber 154, a driver 155, a circulator 156, and an output component 158. In some embodiments, the components of the receiver 240 can be formed on a common semiconductor as an IC. The components of the same reference numerals of the receiver 140 are the same components and provide the same functionality in the receiver 240 and are therefore not described again.

[0066] The OA 242-1 boosts the OTDM signal received from the transmitter 210. The OA 242-2 boosts the clock signal received from the transmitter 210. Both OAs 242 can be coupled to the fiber optic cable 270 via the coupling assembly 209. In some embodiments, the OAs 242 can be connected to a WDM demultiplexer as further described below. In some embodiments, the OAs 242 can be quantum dot semiconductor optical amplifiers with low power consumption and minimal crosstalk between different wavelengths. In some embodiments, the driver 245 can power the OAs 242.

[0067] The output of the OA 242-1 is fed to the data branch 241 and the output of the OA 242-2 is transmitted on the clock branch 243. The function and operation of the data branch 241 is the same as the data branch 141 as described above and the function and operation of the clock branch 243 is the same as the clock branch 143 as shown above.

[0068] In the receiver 240, the controller 260 can monitor and control all components and provide automatic adjustment of adjustable components such as the phase shifter 150, the OAs 242, the driver 155, and the DM 152. In some embodiments, the controller 260 monitors the performance of the transceiver 208 in terms of one or more of bit error rate, data throughput, frame loss, jitter, and other parameters and then performs adjustment of the adjustable components (in both the transmitter 210 and the receiver 240) to optimize the transceiver 208 performance.

[0069] As Figure 2EAs shown, in some embodiments, multiple systems 200-1, 200-2 to 200-X (where X = N / 2) can be provided in parallel, each operating on a separate full-duplex fiber optic cable 270-1, 270-2…270-X. As further shown, each system 200 can provide up to four channels of OTDM in each direction (102, 104). In some embodiments, more than four channels can be provided. Each of the systems 200-1, 200-2…200-X can be operated using a pulsed laser 112 having the same wavelength or different wavelengths or combinations of wavelengths.

[0070] like Figure 2F As shown, in some embodiments, multiple systems 200 and dual WDM multiplexers 272-1 and 272-2 and demultiplexers 274-1 and 274-2 operating on full-duplex fiber optic cables 270 can be provided in parallel. For simplicity, in Figure 2F Only one transmission direction is shown. OTDM signals are transmitted using WDM pairs 272-1 and 274-1, and clock signals are transmitted using WDM pairs 272-2 and 274-2. In some embodiments, one OA 242 is positioned before demultiplexer 274-1, and one OA 242 is positioned before demultiplexer 274-2. For WDM operation, each of systems 200-1, 200-2…200-X uses a pulsed laser 112 with a different wavelength. As further shown, each system 200 can provide up to four channels of OTDM. In some embodiments, more than four channels can be provided.

[0071] In the claims or description of this application, unless otherwise stated, adjectives (such as “substantially” and “about”) that modify one or more features of the embodiments of the invention are understood to mean that the condition or feature is defined within an acceptable tolerance range for operation of the embodiments.

[0072] Implementation of the methods and systems of this disclosure may involve manually, automatically, or in combination thereof, performing or completing certain selected tasks or steps. Furthermore, the actual instruments and devices according to preferred embodiments of the methods and systems of this disclosure can implement several selected steps through hardware (HW) or software (SW) on any operating system with any firmware, or through a combination thereof. For example, as hardware, the selected steps of this disclosure can be implemented as chips or circuits. As software or algorithms, the selected steps of this disclosure can be implemented as multiple software instructions executed by a computer using any suitable operating system. In any case, the selected steps of the methods and systems of this disclosure can be described as being executed by a data processor, such as a computing platform for executing multiple instructions.

[0073] Although the present disclosure is described with respect to computing devices or computers, it should be noted that alternatively any device having a data processor and the ability to execute one or more instructions can be described as a computing device, including but not limited to any type of personal computer (PC), server, distributed server, main control unit, virtual server, cloud computing platform, cellular telephone, IP telephone, smart phone, smart watch, or PDA (personal digital assistant). Any two or more such devices in communication with each other can optionally form a "network" or "computer network."

[0074] It should be understood that where the specification states a component, feature, structure, or characteristic "may", "might", "could" or "would" be, include, "include", "include", "include" or "have" one, that there is no present limitation on associated

[0075] While the present disclosure describes a limited number of embodiments, it is understood that numerous modifications, variations, and other applications of the embodiments can be made. The present disclosure is understood to be limited only by the scope of the claims set forth herein.

Claims

1. An optical data transmission system comprising: an optical transceiver comprising an optical transmitter and an optical receiver, wherein the optical transmitter comprises a pulsed laser for outputting a pulsed laser signal, wherein the optical receiver comprises a data branch and a clock branch, and wherein the optical transmitter is configured to modulate the pulsed laser signal based on a plurality of data signals to form a plurality of modulated optical data signals, to optically time-division multiplex (OTDM) the plurality of modulated optical data signals to obtain a multiplexed optical data signal, and to transmit the multiplexed optical data signal and an optical clock signal derived from the pulsed laser signal separately from the plurality of modulated optical data signals; and a polarization splitter splitting the pulsed laser signal into the data branch of the multiplexed optical data signal ready for transmission and a clock branch for transmission of the optical clock signal; wherein the clock branch is configured to recover the optical clock signal and phase shift it into a plurality of phase-shifted recovered optical clock signals; wherein the data branch comprises a plurality of saturable absorbers (SAs); and wherein each saturable absorber (SA) is in optical communication with one of the plurality of phase-shifted recovered optical clock signals and is configured to receive the multiplexed optical data signal and to transmit one of the modulated optical data signals in accordance with one of the plurality of phase-shifted recovered optical clock signals.

2. The optical data transmission system of claim 1, wherein, the optical clock signal and the multiplexed optical data signal are transmitted by the optical transmitter in orthogonal transverse modes on a single mode optical fiber cable.

3. The optical data transmission system of claim 1, wherein, the optical clock signal and the multiplexed optical data signal are both transmitted by the optical transmitter on separate cables in a full duplex optical fiber cable.

4. The optical data transmission system of claim 1, wherein, a clock pulse from one of the plurality of phase-shifted recovered optical clock signals saturates the respective saturable absorber (SA) causing the respective saturable absorber (SA) to release a pulse from one of the plurality of modulated optical data signals.

5. The optical data transmission system of claim 1, wherein, the clock branch comprises a second splitter and a phase shifter for extracting the optical clock signal into a plurality of phase-shifted recovered optical clock signals.

6. The optical data transmission system of claim 1, wherein, the optical receiver further comprises one or more dispersion managers configured to perform dispersion correction on the plurality of modulated optical data signals and the plurality of phase-shifted recovered optical clock signals.

7. The optical data transmission system of claim 1, wherein, the optical receiver further comprises an output component configured to extract the plurality of data signals from each of the plurality of modulated optical data signals.

8. The optical data transmission system of claim 1, wherein, the pulsed laser is selected from the group comprising bulk lasers, quantum well lasers, quantum dot lasers, semiconductor mode-locked lasers, and mode-locked integrated external cavity surface emitting lasers.

9. The optical data transmission system of claim 1, wherein, the pulsed laser has a pulse repetition rate between 5 GHz and 100 GHz.

10. The optical data transmission system of claim 1, wherein, the optical receiver comprises an optical amplifier (OA).

11. The optical data transmission system of claim 10, wherein, the optical amplifier (OA) is a quantum dot semiconductor optical amplifier.

12. The optical data transmission system of claim 1, wherein, the modulation is one of pulse amplitude modulation (PAM) or quadrature amplitude modulation (QAM).

13. The optical data transmission system of claim 1, wherein, the plurality of data signals comprises 2-16 data signals per wavelength.

14. The optical data transmission system of claim 1, wherein, the plurality of data signals comprises digital signals and / or analog signals.

15. A transmission system comprising: a first optical transceiver and a second optical transceiver, wherein each of the first and second optical transceivers includes a respective optical transmitter, a respective optical receiver, and a respective controller, wherein each optical transmitter includes a respective pulsed laser for outputting a respective pulsed laser signal, wherein each optical receiver includes a respective clock leg and a respective data leg, and wherein each optical transmitter is configured to modulate the respective pulsed laser signal based on a plurality of data signals to form a respective plurality of modulated optical data signals, to optically time-division multiplex (OTDM) the respective plurality of modulated optical data signals to obtain a respective multiplexed optical data signal, and to transmit the respective multiplexed optical data signal separately from the respective plurality of modulated optical data signals and a respective optical clock signal derived from the respective pulsed laser signal; and a respective polarization splitter that splits the respective pulsed laser signal into a data leg of the respective multiplexed optical data signal ready for transmission and a respective clock leg for transmission of the respective optical clock signal, wherein each respective clock leg is configured to recover and phase shift the respective optical clock signal into a respective plurality of phase-shifted recovered optical clock signals, wherein each data leg includes a plurality of saturable absorbers (SAs); and wherein each respective saturable absorber (SA) is in optical communication with one of the respective plurality of phase-shifted recovered optical clock signals and is configured to receive the respective multiplexed optical data signal and transmit one of the respective modulated optical data signals in accordance with one of the respective plurality of phase-shifted recovered optical clock signals.

16. The transmission system of claim 15, wherein, Each respective controller is configured to monitor respective transceiver performance and to perform adjustments of the respective optical transmitter and the respective optical receiver in order to optimize the respective transceiver performance.

17. The transmission system of claim 16, wherein, The monitoring includes monitoring of one or more of bit error rate, data throughput, frame loss, or jitter.

18. The transmission system of claim 15, wherein, Each respective transceiver is formed as an integrated circuit on a common semiconductor substrate.

19. The transmission system of claim 15, wherein, The respective optical clock signals and the respective multiplexed optical data signals are each transmitted by the respective optical transmitters on separate cables in a full-duplex fiber optic cable.

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