System for pulsed laser data transmission using a receiver capable of recovering the clock.

Abstract

1. 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, optically time-division multiplex the plurality of modulated optical data signals to obtain a multiple optical data signal, and transmit the multiple optical data signal together with an optical clock signal derived from the pulsed laser signal; and an optical receiver including a clock recovery branch that recovers 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 plurality of phase-shifted recovered optical clock signals, configured to receive the multiple optical data signal, and to transmit one of the plurality of modulated optical data signals based on the recovered optical clock signal.

Description

Detailed Description of the Invention

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 142,684, filed January 28, 2021, which is incorporated by reference in its entirety.

[0002] [Field] TECHNICAL FIELD Several system embodiments disclosed herein relate generally to signal transmission, and more specifically to systems for the transmission of high data rate optical signals.

[0003] 〔background〕 Coherent and non-coherent optical transceivers for high data rate transmission, such as 400 Gbps and above, typically utilize digital signal processors (DSPs) that provide one or more of pre- or post-compensation for chromatic dispersion and other channel impairments, multiplexing and demultiplexing, implementation of high-level modulation formats, and / or error correction to enable high rates, such as when using PAM4 (or other modulation).

[0004] The required DSP has a high power consumption, typically 8W for a DSP in a system with a data rate of 400Gbps, or higher for higher data rates. Thus, the required DSP increases the power requirements of a high bit rate system. Furthermore, the multiplexing of multiple data channels and other signal processing on the electrical signal introduces latency into the signal transmission. Furthermore, the DSP has a limited maximum throughput due to electrical processing constraints. Therefore, it is desirable to provide a transmission system that features high data rates without the need for a DSP. As a result, it is desirable to provide a transmission system that reduces power consumption and latency and overcomes electrical bandwidth bottlenecks.

[0005] 〔overview〕 The embodiments disclosed herein relate to systems, apparatus, and methods that enable high data rate optical signals with reduced power consumption and reduced latency. The systems described herein reduce system power requirements and latency for comparable data rate transmissions by utilizing all-optical transmitters and all-optical receivers such that no DSP is required. The all-optical transceiver configuration also reduces computational complexity (as required by a DSP). In some embodiments, the all-optical transmitters and all-optical receivers are provided as an integrated circuit (IC) on a common semiconductor substrate to further reduce power and size requirements.

[0006] To provide an all-optical receiver, a clock (local oscillator) is required at the receiver to be used for the transmitted modulated signal. The disclosed system uses a modulated pulsed laser for data transmission and utilizes periodic pulses as the clock. A clock based on the pulsed laser is transmitted along 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 transmitting data and the other transmitting 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 includes a saturable absorber (SA) configured to recover the transmitted data signal by transmitting the received data pulses when saturated by the clock pulses.

[0007] In some embodiments, optical time division multiplexing (OTDM) is provided for the transmission of multiple data channels. The use of optical multiplexing reduces latency and complexity compared to electrical multiplexing such as DSP. In some embodiments, the systems disclosed herein may be replicated or provided with integrated WDM systems for the transmission of a greater number of channels per fiber optic cable. In some embodiments, single mode fiber optic cables are used in unidirectional operation. In some embodiments, full duplex fiber optic cables are used in bidirectional operation. Furthermore, a dispersion manager is also optically handled at the receiver to compensate for dispersion in the transmission and dispersion that may be caused by saturable absorbers. As mentioned above, the use of an optical dispersion manager reduces the computational complexity of the solution.

[0008] In some embodiments, a system comprises an optical transmitter including a pulsed laser for outputting a pulsed laser signal, the optical transmitter configured to modulate the pulsed laser signal based on a plurality of data signals to form a plurality of modulated optical data signals, optically time division multiplex the plurality of modulated optical data signals to obtain a multiple optical data signal, and transmit the multiple optical data signal along with an optical clock signal derived from the pulsed laser signal; and an optical receiver including a clock recovery branch and a data branch, the clock recovery branch configured to recover and phase shift the optical clock signal into a plurality of phase-shifted recovered optical clock signals, the data branch including a plurality of saturable absorbers (SAs), each SA in optical communication with one of the plurality of phase-shifted recovered optical clock signals and configured to receive the multiple optical data signal and transmit one of the modulated optical data signals received in the multiple optical data signal based on one of the plurality of phase-shifted recovered optical clock signals.

[0009] In some embodiments, the optical clock signal and the multiple optical data signals are transmitted by the optical transmitter in orthogonal transverse modes over a single mode optical fiber cable, hi some embodiments, the optical clock signal and the multiple optical data signals are each transmitted by the optical transmitter over separate cables within a full duplex optical fiber cable.

[0010] In some embodiments, a clock pulse from one of the plurality of phase-shifted recovered optical clock signals saturates a respective SA, thereby causing the respective SA to emit 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 the plurality of phase-shifted extracted optical clock signals phase-shifted recovered optical clock signals. In some embodiments, the optical receiver further includes one or more dispersion managers configured for dispersion compensation of the plurality of modulated optical data signals and the plurality of phase-shifted recovered optical clock signals. In some embodiments, the optical receiver further includes an output component configured to extract the plurality of data signals from each of the plurality of modulated optical data signals. In some embodiments, the pulsed laser is selected from the group consisting of a bulk laser, a quantum well laser, a quantum dot laser, a semiconductor mode-locked laser, and a mode-locked integrated external cavity surface emitting laser. 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. 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 to 16 data signals per wavelength. In some embodiments, the plurality of data signals comprises digital and / or analog signals.

[0012] In some embodiments, a transmission system comprises a first transceiver and a second transceiver, the first transceiver and the second transceiver each comprising an optical transmitter, an optical receiver, and a controller, each of the optical transmitters configured to modulate a pulsed laser signal based on a plurality of data signals to form a plurality of modulated optical data signals, optically time-division multiplex the plurality of modulated optical data signals to obtain a multiplexed optical data signal, and transmit the multiplexed optical data signal together with an optical clock signal derived from the pulsed laser signal;

[0013] Each of the optical receivers includes a clock recovery branch and a data branch, the clock recovery branch configured to recover and phase shift the optical clock signal into a plurality of phase-shifted recovered optical clock signals, and the data branch includes a plurality of saturable absorbers (SAs), each SA configured to be in optical communication with one of the plurality of phase-shifted recovered optical clock signals, receive the multiplexed optical data signal, and transmit one of the modulated optical data signals received in the multiplexed optical data signal based on one of the plurality of phase-shifted recovered optical clock signals.

[0014] In some embodiments, each controller is configured to monitor transceiver performance and perform adjustments of the transmitter and the receiver to optimize the transceiver performance. In some embodiments, monitoring the transceiver performance includes monitoring one or more of a number of bit errors, data throughput, frame loss, or jitter. In some embodiments, each transceiver is formed as an IC on a common semiconductor substrate.

[0015] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. 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.

[0016] BRIEF DESCRIPTION OF THE DRAWINGS Embodiments disclosed herein will now be described, by way of example only, with reference to the accompanying drawings in which:

[0017] FIG. 1A illustrates an optical system for data transmission over a single mode fiber, according to some embodiments.

[0018] FIG. 1B illustrates a transmitter for use with a single mode fiber, according to some embodiments.

[0019] FIG. 1C illustrates an example signal amplitude graph of an optical signal in a transmitter according to some embodiments.

[0020] FIG. 1D illustrates a receiver for use with a single mode fiber, according to some embodiments.

[0021] FIG. 1E illustrates an example signal amplitude graph of an optical signal in a receiver according to some embodiments.

[0022] 1F and 1G show multiple optical transmission systems according to some embodiments.

[0023] FIG. 2A illustrates an optical system for data transmission over full-duplex fiber according to some embodiments.

[0024] FIG. 2B illustrates a transmitter for use with a full duplex fiber according to some embodiments.

[0025] FIG. 2C illustrates a coupler assembly for use with a full duplex fiber, according to some embodiments.

[0026] FIG. 2D illustrates a receiver for use with full duplex fiber according to some embodiments.

[0027] 2E and 2F show multiple optical transmission systems according to some embodiments.

[0028] Detailed Description Aspects of the embodiments relate to systems, apparatus, and methods that enable high data rate optical signals with reduced power consumption, reduced latency, and reduced computational complexity. Figures 1A-1G show an optical system for data transmission, according to some embodiments. As shown in Figure 1A, the optical transmission system 100 includes a transceiver 108-1 and a transceiver 108-2. Each transceiver 108 includes an optical transmitter 110, an optical receiver 140, and a controller 160.

[0029] The transmitter 110-1 is in optical communication with the receiver 140-2 via a single mode fiber optic cable 170-1 for transmitting a unidirectional data signal 102. The transmitter 110-2 is in optical communication with the receiver 140-1 via a single mode fiber optic cable 170-2 for transmitting a unidirectional data signal 104. In some embodiments, a single fiber optic cable 170 may 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 data signals 102 and 104, are also referred to herein as "channels." In some embodiments, each transceiver 108-1 and transceiver 108-2 are provided as integrated circuits (ICs) on a common semiconductor substrate.

[0030] Data signals 102 and 104 are electrical data signals. In some embodiments, data signals 102 and 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 and 104 are analog electrical signals, and the laser pulse repetition rate is equal to or greater than the Nyquist frequency of the analog electrical signals. In some embodiments, data signals 102 and 104 are a combination of digital and analog signals. Although FIGS. 1A-1G show the transmission of two channels (data signals 102-1 and 102-2, and data signals 104-1 and 104-2) in each transmission direction for simplicity, it should be understood that more than two channels may be multiplexed and transmitted by system 100. In some embodiments, 2-16 data signals per wavelength are supported.

[0031] The controller 160 is a computing device as defined herein. As described further below, 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.

[0032] The components of each transmitter 110 are further described with reference to Figure 1B. The components of each transmitter 110 include a pulsed laser 112, a polarization splitter 114, a 3 dB splitter 116, a driver 118, an electro-optic (EO) modulator 120, a variable 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.

[0033] The pulsed laser 112 comprises a source of a pulsed laser signal that can be modulated based on the data signal 102 for optical transmission of 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 λ1. The pulsed laser 112 emits pulses at a periodic repetition rate. In some embodiments, the pulsed laser 112 can be any one 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-100 GHz. In some embodiments, the pulsed laser 112 can support a pulse repetition rate between 100 GHz-400 GHz.

[0034] The polarization splitter 114 splits the pulsed laser signal into orthogonal transverse modes. In the system 100, one mode is used for data transmission and the other mode is used for clock transmission. Data is transmitted on the data branch 113 in the TE (transverse electric) mode and the clock is transmitted on the clock branch 111 in the TM (transverse magnetic) mode, or vice versa (data on TM and clock on TE). In some embodiments, the 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, the polarization splitter 114 splits the pulsed laser signal equally between the two modes. It is expected that both modes may experience the same distortion during transmission without affecting the orthogonality.

[0035] In the data branch 113, the transmitter 112 comprises an OTDM of multiple data signals 102 (or 104). Exemplarily, two data signals 102-1 and 102-2, two drivers 118-1 and 118-2, and two EO modulators 120-1 and 120-2 are shown for simplicity. However, it should be understood that multiple (three or more) data signals can be supported. The 3 dB splitter 116 splits the pulsed transverse mode laser signal based on the number of data signals supported (shown here as two). In some embodiments, each data signal 102 is input to the transmitter 112 via a driver 118. The driver 118 can provide power to the EO modulator 120 and can adjust the electrical signal level of the input data signal 102.

[0036] The EO modulator 120 modulates the output source of a pulsed laser signal based on the input data signal 102. In some embodiments, the EO modulator can include a digital-to-analog converter (DAC) (not shown) for processing an analog electrical input. In some embodiments, the pulse (clock) rate and modulated channel rate are as follows:

[0037] R / (number of channels).

[0038] A number of modulation schemes can be applied, including but not limited to Pulse Amplitude Modulation (PAM) or Quadrature Amplitude Modulation (QAM). The variable phase shifter 122 shifts the modulated (phase shifted) channel (λ 1-MOD , λ1S 2-MOD, SHIFT 1. The phase of the second further channel is shifted to obtain the modulated (phase shifted) channel (denoted as λ1S). As a result, the channel pulses are interleaved when combined at the 3 dB coupler 124. The coupler 124 couples the modulated (phase shifted) channel (λ1S 1-MOD , λ1S 2-MOD, SHIFT ) to produce an OTDM output signal (λ 113 ) of the data branch 113 having a pulse rate of 1 OTDM (denoted as:

[0039] Rx(number of channels).

[0040] FIG. 1C shows the modulated (phase-shifted) channel (λ1S 1-MOD , λ1S 2-MOD, SHIFT ), and the combined OTDM output (λ 1 OTDM ), as well as a clock signal (λ 1 CLOCK 4 shows an example signal amplitude diagram of a 10-bit 10-bit 12-bit 16-bit 18-bit 19-bit 20-bit 21-bit 22-bit 23-bit 24-bit 25-bit 26-bit 27-bit 28-bit 29-bit 30-bit 31-bit 32-bit 33-bit 34-bit 35-bit 36-bit 37-bit 38-bit 39-bit 40-bit 41-bit 42-bit 43-bit 44-bit 45-bit 46-bit 47-bit 48-bit 49-bit 50-bit 51-bit 52-bit 53-bit 54-bit 55-bit 56-bit 57-bit 58-bit 59-bit 60-bit 61-bit 62-bit

[0041] The polarization coupler 126 combines the transverse modes of the data branch 111 and the clock branch 113 to form a polarization coupler 126 called the λ 1OTDM + CLOCK In some embodiments, the pulse shaper 128 forms a quadrature transverse signal carrying the OTDM output and a clock, denoted as λ . 1OTDM + CLOCK The transmitter output 106 is transmitted over the fiber optic cable 170 towards the receiver 140. In some embodiments, the pulse shaper 128 may be connected to a fiber optic cable 170. In some embodiments, the pulse shaper 128 may feed into a WDM multiplexer, as described further below. In some embodiments, the pulse shaping may be performed using a filter bank. In some embodiments, the pulse shaping may be performed using a nested unbalanced Mach-Zehnder interferometer (MZI), a ring resonator, or a combination of an MZI and a ring resonator. The transmitter output 106 is transmitted over the fiber optic cable 170 towards the receiver 140.

[0042] In the transmitter 110 , the controller 160 monitors and controls all components and can provide automatic adjustment of adjustable components such as the phase shifter 122 , the pulse shaper 128 , and the driver 118 .

[0043] The components of each receiver 140 are further described with reference to Figure 1D. Each receiver 140 may include an optical amplifier (OA) 142, a polarization splitter 144, a splitter 146, a polarization / phase controller (PC) 148, a variable 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 receiver 140 may be formed on a common semiconductor substrate as an IC.

[0044] The OA 142 amplifies the signal received from the transmitter 110. In some embodiments, the OA 142 may be connected to a fiber optic cable 170. In some embodiments, the OA 142 may be connected to a WDM demultiplexer, as described further below. In some embodiments, the OA 142 may be a quantum dot semiconductor optical amplifier with low power consumption and minimal crosstalk between different wavelengths. In some embodiments, the driver 145 may provide power to the OA 142.

[0045] OA142(λ 1 OTDM + CLOCK ) is the output of the received signal (λ 1 OTDM + CLOCK ) into orthogonal transverse modes. The data mode (TM or TE as defined in the transmitter) is transmitted on the data branch 141 and the clock mode (TM or TE as defined in the transmitter) is transmitted on the clock recovery branch 143. In some embodiments, the polarization splitter 144 splits the received signal unequally between the two modes. Non-limiting examples of splitting ratios include 90 / 10 and 80 / 20. In some embodiments, the polarization splitter 144 splits the received signal equally between the two modes.

[0046] FIG. 1E shows a composite OTDM signal (here λ 1 ) split in data branch 141. 1 OTDM ), the recovered clock and the phase-shifted clock of clock branch 143 (here denoted as λ 1-CLOCK , λ 1-CLOCK SHIFT), as well as the restored modulated (phase-shifted) channel (here denoted as λS 1-MOD , λ1S 2-MOD, SHIFT 4 shows an example signal amplitude graph of

[0047] In data branch 141, splitter 146-1 splits the OTDM based on the number of channels time division multiplexed by transmitter 110. Thus, each split in data branch 141 is a λ 1 OTDM Similarly, in clock branch 143, splitter 146-2 splits clock signal λ based on the number of channels time-division multiplexed by transmitter 110. 1-CLOCK As above, two OTDM channels and corresponding two clock channels are shown for simplicity, but it should be understood that multiple channels may be demultiplexed.

[0048] In some embodiments, a polarization / phase controller (PC) 148 may be provided to match polarization and correct phase mismatch. Illustratively, multiple PCs 148-1...148-4 may be provided, each on a separate signal or clock branch. Variable phase shifters 150-1 and 150-2 shift the phase of the clock channel so that the clock pulses are timed to coincide with the interleaved channels of the OTDM signal in the data branch 141. Each dispersion manager (DM) 152 may correct dispersion in the optical channel that affected the data signal and / or the clock signal. Illustratively, multiple DMs 152-1...152-4 are provided on separate branches. The DMs 152 may further introduce pre-correction for dispersion introduced by the SAs 154. In some embodiments, the DMs 152 may include chirped Bragg gratings controlled by the temperature controller 153. In some embodiments, the drivers 155 may provide power to the respective SAs 154.

[0049] Each output of the clock branch 143 (here, λ1 CLOCK and λ 1 CLOCK SHIFT 1D ) are fed to a corresponding circulator 156 in the data branch 141. Illustratively, two circulators 156-1, 156-2, two SAs 154-1, 154-2, and two drivers 155-1, and 155-2 are shown corresponding to two multiplexed data channels. In some embodiments, the circulators 156 may be non-reciprocating, one-way, or three-port circulators. In FIG. 1D , the circulators 156 are shown as having a clockwise direction, but it should be understood that the direction used is functional. In use, the clock input is circulated by the SAs 154. In some embodiments, each SA 154 may be any one of a quantum well (QW) semiconductor SA, a quantum dot SA, or a bulk semiconductor SA.

[0050] The clock pulses saturate the SA 154, making it transparent, and thus "release" or "transmit" the current OTDM interleaved channel pulses through the SA 154 corresponding to the pulse period. Thus, at different periods, λ 1 CLOCK saturates SA154-1, and λ 1 CLOCK SHIFT saturates SA 154-2. Each period corresponds to a separate OTDM channel, resulting in a current OTDM channel pulse passing through SA 154. When the clock signal is between pulses (low clock signal), SA 154 does not saturate and therefore blocks the other OTDM channels. In some embodiments, SA 154-1 provides an electrical output for recovered clock 159-1 and SA 154-2 provides an electrical output for recovered clock 159-2.

[0051] The emitted OTDM pulses enter a circulator 156 and are circulated to an output component (OC) 158. Each OC 158 includes the necessary components to convert the emitted optical channels back to an electrical data signal 102. Illustratively, two OCs 158-1 and 158-2 are shown corresponding to two multiplexed data channels. The OCs 158 may include one or more of a photodiode (PD) or photodiode array for optical-to-electrical conversion, a transimpedance amplifier (TIA), a digital-to-analog conversion circuit (DAC), and / or a limiting amplifier (LA).

[0052] In receiver 140, controller 160 monitors and controls all components and may provide automatic adjustment of adjustable components such as phase shifter 150, OA 142, driver 145, driver 155, and DM 152. In some embodiments, controller 160 monitors the performance of transceiver 108 in terms of one or more of bit error count, data throughput, frame loss, jitter, and other parameters. Controller 160 then performs adjustment of adjustable components (in both transmitter 110 and receiver 140) to optimize performance of transceiver 108.

[0053] As shown in FIG. 1F, in some embodiments, multiple systems 100-1, 100-2 through 100-X (where X=N / 2) may be provided in parallel, with each system 100 operating over a separate set of fiber optic cables 170-1 and 170-2. As further shown, each system 100 may include up to four channels of OTDM in each direction (102, 104). In some embodiments, more than four channels may be included. Each of systems 100-1, 100-2, and 100-X may operate using pulsed lasers 112 having the same or different wavelengths, or a combination of these wavelengths.

[0054] As shown in FIG. 1G, in some embodiments, multiple systems 100-1 to 100-X may be provided in parallel with wavelength division multiplexing (WDM) multiplexers 172-1 and 174-2 and demultiplexers 172-2 and 174-1, respectively, operating over a single fiber optic cable 170-1 and 170-2. For operation using WDM, each of the systems 100-1, 100-2 to 100-N uses a respective pulsed laser 112 having a different wavelength. As further shown in FIG. 1G, each system 100 may include up to four channels of OTDM in each direction (102, 104). In some embodiments, more than four channels may be provided.

[0055] 2A-2F show an optical system for bidirectional data transmission over a full-duplex fiber, according to some embodiments. As shown in FIG. 2A, 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 coupler assembly 209, and a controller 260.

[0056] Transmitter 210-1 is in optical communication with receiver 240-2 via full-duplex fiber optic cable 270 for transmitting data signals 102 using a first wavelength (λ1). Transmitter 210-2 is in optical communication with receiver 240-1 via full-duplex fiber optic cable 270 for transmitting data signals 104 using a second wavelength (λ2). In some embodiments, each transceiver 208 is provided as an IC on a common semiconductor substrate.

[0057] 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. Although FIGS. 2A-2F show the transmission of two channels (data signals 102-1 and 102-2 and data signals 104-1 and 104-2) in each transmission direction for simplicity, it should be understood that more than two channels may be transmitted by the system 200. In some embodiments, 2-16 data signals per wavelength are supported.

[0058] Each controller 260 is a computing device as defined herein. As described further below, 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. In some embodiments, coupler assembly 209-1 is in data communication with controller 260-1, and coupler assembly 209-2 is in data communication with controller 260-2.

[0059] The components of each transmitter 210 are further described with reference to FIG. 2B and include the pulsed laser 112, the splitter 214, the 3 dB splitter 116, the driver 118, the EO modulator 120, the variable phase shifter 122, the 3 dB coupler 124, and the pulse shaper 228. In some embodiments, the components of the transmitter 210 are formed on a common semiconductor as an IC. Components numbered similarly to the transmitter 110 are the same components and have the same function in the transmitter 210 and will not be described again.

[0060] Splitter 214 splits the pulsed laser signal into a data branch 213 for preparing an OTDM signal for transmission and a clock branch 211 for clock transmission. In some embodiments, splitter 214 splits the pulsed laser signal intensity unequally between the two branches. Non-limiting examples of splitting ratios include 90 / 10 and 80 / 20. In some embodiments, splitter 214 splits the pulsed laser signal equally between the two branches.

[0061] In the data branch 213, the transmitter 212 provides an OTDM of multiple data signals 102 (or 104). Two data signals 102-1 and 102-2 are shown for simplicity, but it should be understood that multiple data signals can be supported. The functionality of the data branch 213 is the same as in the system 100, and the OTDM output (λ) of the data branch 213 has a pulse rate of Rx (number of channels). 1 OTDM (denoted as

[0062] In some embodiments, the pulse shaper 228-1 is configured to 1 OTDM In some embodiments, the pulse shaper 228-2 shapes and equalizes the pulse height and shape of λ. 1 CLOCK In some embodiments, the pulse shaping may be performed using a filter bank. In some embodiments, the pulse shaping may be performed using nested unbalanced MZIs or ring resonators, or a combination of MZIs and ring resonators.

[0063] 2C, the output of the transmitter 210 is fed to a coupler assembly 209. Each coupler assembly 209 includes a circulator 230 and a coupler 232. The pulse shaper 228-1 is a circulator for circulating a λ 1 OTDM is supplied to the optical circulator 230-1, and the pulse shaper 228-2 supplies λ 1 CLOCKto optical circulator 230-2. In some embodiments, circulator 230 may be a non-reciprocating, one-way, three-port circulator. In FIG. 2C, circulator 230 is shown as having a clockwise orientation, however, it should be understood that the orientation used is functional.

[0064] One of the ports of the circulator 230 is connected to a coupler 232. The coupler 232-1 has an output (Tx) λ 1 OTDM to a first one of the fibers in cable 270, and coupler 232-2 connects output λ 1 CLOCK to a second one of the fibers in the fiber optic cable 270. The input (Rx) clock and OTDM signal λ from the cable 270 2 OTDM and λ 2 CLOCK exits coupler 232 and is directed by circulator 230 to an exit port of circulator 230 that is connected to the inlet of a "same side" receiver 240.

[0065] In the transmitter 210 , the controller 160 monitors and controls all components and can provide automatic adjustment of adjustable components such as the phase shifter 122 , the pulse shaper 228 , and the driver 118 .

[0066] The components of each receiver 140 are further described with reference to FIG. 2D and may include an optical amplifier (OA) 242, a splitter 146, a polarization / phase controller (PC) 148, a variable 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 receiver 240 may be formed on a common semiconductor as an IC. Components numbered similarly to receiver 140 are the same components and comprise the same function in receiver 240 and will not be described again.

[0067] The OA 242-1 amplifies the OTDM signal received from the transmitter 210. The OA 242-2 amplifies the clock signal received from the transmitter 210. Both of the OAs 242 may be connected to the fiber optic cable 270 via the coupler assembly 209. In some embodiments, the OA 242 may be connected to a WDM demultiplexer, as described further below. In some embodiments, the OA 242 may be a quantum dot semiconductor optical amplifier with low power consumption and minimal crosstalk between different wavelengths. In some embodiments, the driver 245 may provide power to the OA 242.

[0068] The output of OA 242-1 is provided to data branch 241, and the output of OA 242-2 is carried on clock branch 243. The function and operation of data branch 241 is the same as data branch 141 described above. The function and operation of clock branch 243 is the same as clock branch 143 described above.

[0069] In the receiver 240, the controller 260 monitors and controls all components and may provide automatic adjustment of adjustable components such as the phase shifter 150, the OA 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 count, data throughput, frame loss, jitter, and other parameters. The controller 260 then performs adjustments of the adjustable components (in both the transmitter 210 and the receiver 240) to optimize the performance of the transceiver 208.

[0070] As shown in FIG. 2E, in some embodiments, multiple systems 200-1, 200-2 to 200-X (where X=N / 2) may be provided to operate in parallel, each via a separate full-duplex fiber optic cable 270-1, 270-2 to 270-X. As further shown, each system 200 may include up to four channels of OTDM in each direction (102, 104). In some embodiments, more than four channels may be provided. Each system 200-1, 200-2...200-X may operate using pulsed lasers 112 having the same wavelength or different wavelengths, or a combination of these wavelengths.

[0071] As shown in FIG. 2F, in some embodiments, multiple systems 200 may be provided in parallel with two WDM multiplexers 272-1 and 272-2 and two demultiplexers 274-1 and 274-2 operating over a full-duplex fiber optic cable 270. For simplicity, only one direction of transmission is shown in FIG. 2F. The OTDM signal is transmitted using WDM pairs 272-1 and 274-1, and the clock signal is transmitted using WDM pairs 272-2 and 274-2. In some embodiments, one OA 242 is placed before the demultiplexer 274-1, and one OA 242 is placed before the demultiplexer 274-2. When operating using WDM, each of the systems 200-1, 200-2... and 200-X uses a pulsed laser 112 having a different wavelength. As further shown, each system 200 may include up to four channels of OTDM. In some embodiments, more than four channels may be provided.

[0072] In the claims or specification of this application, unless otherwise indicated, adjectives such as "substantially" and "about" modifying a condition or related property of a feature or characteristic of an embodiment of the invention are understood to mean that the condition or property is defined within the tolerance permitted for the operation of the embodiment for the application as intended.

[0073] The implementation of the disclosed method and system may include performing or completing certain selected tasks or steps manually, automatically, or a combination thereof. Furthermore, according to the actual instruments and equipment of the preferred embodiments of the disclosed method and system, the selected steps may be implemented by hardware (HW) or by software (SW) on any operating system of any firmware, or a combination thereof. For example, as hardware, the selected steps of the disclosed method and system may be implemented as a chip or circuit. As software or algorithm, the selected steps of the disclosed method and system may be implemented as software instructions executed by a computer using any suitable operating system. In either case, the selected steps of the disclosed method and system may be described as being executed by a data processor, such as a computing platform for executing instructions.

[0074] It should be noted that although the present disclosure is described in terms of computing devices, or computers, any device characterized by a data processor and the ability to execute one or more instructions may optionally be described as a computing device, including, but not limited to, any type of personal computer (PC), a server, a distributed server, a master control unit, a virtual server, a cloud computing platform, a mobile phone, an IP phone, a smart phone, a smart watch, or a PDA (personal digital assistant). Any two or more of such devices in communication with each other may optionally form a "network" or "computer network."

[0075] It is to be understood that when a claim or the specification refers to "a" or "an" element, such reference should not be construed as referring to only one of that element. In the specification and claims of this application, each of the verbs "comprise," "include," and "have," and combinations thereof, are used to indicate an object, i.e., the object of the verb, but not necessarily an exhaustive list of components, elements or portions of the subject matter, or the object of the verb.

[0076] While the present disclosure describes a limited number of embodiments, it will be understood that many variations, modifications, and other applications of such embodiments may be made. It is to be understood that the present disclosure is not limited to the specific embodiments described herein, but rather only by the scope of the appended claims. [Brief description of the drawings]

[0077] [Figure 1A] 1 illustrates an optical system for data transmission over a single mode fiber according to some embodiments. [Figure 1B] 1 illustrates a transmitter for use with a single mode fiber, according to some embodiments. [Figure 1C] 4 illustrates an example signal amplitude graph of an optical signal in a transmitter according to some embodiments. [Figure 1D] 1 illustrates a receiver for use with a single mode fiber according to some embodiments. [Figure 1E] 4 illustrates an example signal amplitude graph of an optical signal in a receiver according to some embodiments. [Figure 1F] 1 illustrates multiple optical transmission systems according to some embodiments. [Figure 1G] 1 illustrates multiple optical transmission systems according to some embodiments. [Figure 2A] 1 illustrates an optical system for data transmission over full-duplex fiber according to some embodiments. [Figure 2B]1 illustrates a transmitter for use with a full duplex fiber according to some embodiments. [Figure 2C] 1 illustrates a coupler assembly for use with a full duplex fiber, according to some embodiments. [Figure 2D] 1 illustrates a receiver for use with full duplex fiber according to some embodiments. [Figure 2E] 1 illustrates multiple optical transmission systems according to some embodiments. [Figure 2F] 1 illustrates multiple optical transmission systems according to some embodiments.

Claims

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

2. 2. The 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 over a single mode optical fiber cable.

3. 2. The system of claim 1, wherein said optical clock signal and said multiple optical data signals are each transmitted by said optical transmitter over separate cables within a full-duplex fiber optic cable.

4. 2. The system of claim 1, wherein a clock pulse from one of the plurality of phase-shifted recovered optical clock signals saturates a respective SA, thereby causing the respective SA to emit a pulse from one of the plurality of modulated optical data signals.

5. 2. The system of claim 1, wherein the receiver clock branch includes a second splitter and a phase shifter for extracting the optical clock signal into the multiple phase-shifted recovered optical clock signals.

6. 10. The system of claim 1, wherein the optical receiver further comprises one or more dispersion managers configured for dispersion compensation of the plurality of modulated optical data signals and the plurality of phase-shifted recovered optical clock signals.

7. 10. The 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. 10. The system of claim 1, wherein the pulsed laser is selected from the group consisting of a bulk laser, a quantum well laser, a quantum dot laser, a semiconductor mode-locked laser, and a mode-locked integrated external cavity surface emitting laser.

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

10. 2. The system of claim 1, wherein the optical receiver includes an optical amplifier (OA) located at an input side of the optical receiver for amplifying the multiplexed optical data signal and the optical clock signal received from the optical transmitter.

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

12. 2. The system of claim 1, wherein the modulation is one of Pulse Amplitude Modulation (PAM) or Quadrature Amplitude Modulation (QAM).

13. The system of claim 1 , wherein the plurality of data signals includes between 2 and 16 data channels.

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

15. A first optical transceiver and a second optical transceiver, each of the first optical transceiver and the second optical transceiver includes an optical transmitter, an optical receiver, and a controller; each said optical transmitter includes a respective pulsed laser for outputting a respective pulsed laser signal, and a respective polarization splitter for splitting said respective pulsed laser signal into a transmitter data branch for preparing a respective multiplexed optical data signal for transmission, and into a respective transmitter clock branch for transmission of a respective optical clock signal; each of the optical transmitters comprises a first optical transceiver and a second optical transceiver configured to modulate a respective one of the pulsed laser signals based on a plurality of data signals to form a respective plurality of modulated optical data signals, optically time-division multiplex (OTDM) the respective plurality of modulated optical data signals to obtain the respective multiplexed optical data signals, and transmit the respective multiplexed optical data signals and the respective optical clock signals derived from the respective pulsed laser signals separately from the respective plurality of modulated optical data signals; each said optical receiver includes a respective receiver clock branch and a respective receiver data branch; each respective receiver clock branch configured to recover and phase shift said respective optical clock signal into a respective plurality of phase-shifted recovered optical clock signals; Each of the receiver data branches includes a plurality of saturable absorbers (SAs); a first SA configured to receive a first one of said first and second optical data signals in optical communication with said first one of said first and second phase-shifted recovered optical clock signals; and a second SA configured to transmit a second one of said first and second modulated optical data signals in optical communication with said first one of said first and second phase-shifted recovered optical clock signals.

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

17. 17. The transmission system of claim 16, wherein monitoring the transceiver performance includes monitoring one or more of a bit error count, a data throughput, a frame loss, or a jitter.

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

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

Images