CN118216099A - Dual output coherent light technique - Google Patents

Abstract

The proposed technique allows 1+1 optical protection and can increase the coherent module output optical power by 3dB over similar transmitter (Tx) and receiver (Rx) implementation complexity, as well as allowing integration into existing data center formats.

Description

Dual output coherent light technique

Cross Reference to Related Applications

The present application is a continuation of U.S. patent application 17/848,948, filed 24 at 2022, which claims the benefit of the filing date of U.S. provisional patent application 63/282,416, filed 11 at 2021, 23, the disclosure of which is incorporated herein by reference.

Background

Coherent optical communication technology generally involves modulating the amplitude and phase of light and transmitting information across two polarization states while transporting the information over a fiber optic cable. Coherent optical communication technology offers the potential to utilize more of the available bandwidth of a fiber optic cable or transmission path than competing technologies. Such communications typically utilize a coherent optical receiver. In such receivers, a Local Oscillator (LO) is used to interfere with the transmitted signal, which LO provides an extraction of phase information and is therefore referred to as a coherent receiver.

Coherent optical technology offers as many advantages as possible over other forms of optical transmission such as intensity modulation and direct detection (IM-DD): higher receiver sensitivity, higher Spectral Efficiency (SE), and higher tolerance to various linear optical impairments such as fiber dispersion (CD) and polarization-mode dispersion (PMD). In applications where the state of polarization (SOP) is not maintained during transmission, phase and polarization diversity four-dimensional (4D) vector receivers are typically employed to detect and demodulate the dry modulated signal. 4D refers to the separate in-phase (I) and quadrature (Q) components of the X-polarized signal and the Y-polarized signal (I ⁺、I^-、Q⁺、Q^- for the X-polarized signal, and I ⁺、I^-、Q⁺、Q^- for the Y-polarized signal). A 4D vector receiver is also typically used when the received signal is only a two-dimensional (2D) modulated optical signal, such as a Single Polarization (SP) Quadrature Amplitude Modulated (QAM) signal, or a one-dimensional (1D) modulated signal, such as an SP pulse amplitude modulated (SP-PAM) signal.

Pluggable coherent light technology operates within the boundaries of several design constraints. The first is the link budget challenge when using high bandwidth throughput, e.g., 800Gbps (Gbps or Gb/s denoted "G") or higher, for 1+1 protection applications that send redundant signals on the network. The second is the cost-effective challenge of "break-over" applications in point-to-multipoint networks or applications. Another constraint is the relatively stringent power dissipation requirements, which limit the power consumption of pluggable optical modules. In this regard, module power density generally increases with the demand for higher bandwidth. These and other constraints are factors considered in the design and deployment of modules for this type of technology.

Disclosure of Invention

Aspects of the disclosed technology include methods, systems, and apparatus relating to pluggable coherent optics. For example, the disclosed techniques may include a dual input receiver or a dual output transmitter. In other cases, the disclosed technology may include a pluggable coherent transceiver including one or more of each of a dual input receiver and a dual output transmitter.

For example, one aspect of the disclosed technology may include a dual input receiver including a first polarizing beamsplitter configured to receive a first signal; and a second polarizing beam splitter configured to receive a second signal, wherein the second signal is a replica of the first signal. The first polarizing beam splitter may be configured to split the first signal into a first component and a second component and to provide the first component of the first signal to a first optical coupler of a first 90 degree blend and the second component of the first signal to a second optical coupler of a second 90 degree blend. Further, the second polarizing beam splitter may be configured to split the second signal into two components and provide a first component of the second signal to the first 90 degree hybrid first optical coupler and a second component of the second signal to the second 90 degree hybrid second optical coupler. Further, the first 90 degree hybrid first optical coupler and the second 90 degree hybrid second optical coupler may be coupled to a local oscillator such that the first 90 degree hybrid and the second 90 degree hybrid output phase or polarization information associated with the first signal.

According to this aspect of the disclosed technique, a first 90 degree hybrid first optocoupler outputs a first coupled signal to a third optocoupler, and the third optocoupler outputs a first set of output signals including at least a portion of the output phase or polarization information. Further, the first 90 degree hybrid first optocoupler outputs a second coupled signal to a fourth optocoupler, and the fourth optocoupler outputs a second set of output signals including at least a portion of the output phase or polarization information. In addition, the local oscillator outputs one or more local oscillation signals to the third optical coupler and the fourth optical coupler. Furthermore, the dual input receiver may also include a1 x 4 splitter coupled to the local oscillator.

Further in accordance with this aspect of the disclosed technique, the second 90 degree hybrid second optocoupler outputs a third coupled signal to the fifth optocoupler, and the fifth optocoupler outputs a third set of output signals including at least a portion of the output phase or polarization information. Further, the second 90 degree hybrid second optocoupler outputs a fourth coupled signal to the sixth optocoupler, and the sixth optocoupler outputs a fourth set of output signals including at least a portion of the output phase or polarization information. Further, the local oscillator outputs one or more local oscillation signals to the fifth and sixth optical couplers, and the dual input receiver may further include a1×4 splitter coupled to the local oscillator.

Another aspect of the disclosed technology may include a dual output transmitter. The dual output transmitter includes a plurality of mach-zehnder modulators (MZMs) configured to receive the laser output signals and to each output a raw in-phase component or a raw quadrature component based on the laser output signals; a first polarizing beam combiner coupled to the plurality of MZMs and configured to combine a first raw in-phase component and a first raw quadrature component in the X-polarization plane and the Y-polarization plane to generate a first transmit signal, wherein the first raw in-phase component is based on a first signal generated by a first MZM of the plurality of MZMs and the first raw quadrature component is based on a second signal generated by a second MZM of the plurality of MZMs; and a second polarizing beam combiner coupled to the plurality of MZMs and configured to combine the first complementary in-phase component and the first complementary quadrature component in the X-polarization plane and the Y-polarization plane to generate a second transmit signal, wherein the first complementary in-phase component is based on a third signal generated by a third MZM of the plurality of MZMs and the first complementary quadrature component is based on a fourth signal generated by a fourth MZM of the plurality of MZMs. In addition, the first transmission signal and the second transmission signal contain equivalent information.

In accordance with this aspect of the disclosed technique, a second signal generated by a second MZM of the plurality of MZMs is provided to a first 90 degree phase shifter, and the first 90 degree phase shifter is coupled to a first polarization beam combiner through a first optical coupler. Further, a first 90 degree phase shifter may be coupled to a first MZM of the plurality of MZMs and configured to receive the first signal. Further in accordance with this aspect of the disclosed technique, the first signal is provided to a first optical coupler, and the first optical coupler is coupled to a second polarizing beam combiner.

Further, in accordance with this aspect of the disclosed technique, a fourth signal generated by a fourth MZM of the plurality of MZMs is provided to a second 90 degree phase shifter, and the second 90 degree phase shifter is coupled to the second polarizing beam combiner through a second optical coupler. Further, a second 90 degree phase shifter is coupled to a third MZM of the plurality of MZMs and configured to receive a third signal. Further, the third signal is provided to a second optical coupler, and the second optical coupler is coupled to the first polarizing beam combiner.

Drawings

The drawings are not intended to be drawn to scale. Like reference numbers and designations in the various drawings indicate like elements. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:

FIG. 1 is a schematic diagram of a 1+1 protected metropolitan area (metro) transport system using pluggable 400G-ZR coherent light technology in accordance with aspects of the present disclosure.

Fig. 2 is a schematic diagram of a 1.6Tb/s coherent DR4 optical module design using coherent optical techniques in accordance with aspects of the present disclosure.

Fig. 3 is a schematic diagram of a digital subcarrier based 1.6Tb/s coherent DR4 optical module design in accordance with aspects of the disclosed technique.

Fig. 4 is a schematic diagram of a single-output and single-input coherent transceiver.

Fig. 5 is a schematic diagram of a first example dual output and single input coherent optical transceiver technique in accordance with aspects of the disclosed technique.

Fig. 6 is an enlarged view of a co-polarized and phase diversity receiver.

FIG. 7 illustrates example aspects of performance of aspects of the present disclosure.

Fig. 8 illustrates a dual output, dual input coherent optical transceiver technique in accordance with aspects of the disclosed technique.

Fig. 9 is a schematic diagram of an example 1.6Tb/s coherent DR4 optical module design using dual output, dual input coherent optical techniques in accordance with aspects of the disclosed technique.

FIG. 10 illustrates an example computing system in accordance with aspects of the disclosed technology.

Detailed Description

SUMMARY

The disclosed technology increases the coherent module output optical power by 3dB by using the same laser with similar transmitter (Tx) and receiver (Rx) implementation complexity and allows integration into existing data center architectures. The increase in module output power may be used to increase the supported link loss of an optical transport system requiring 1+1 optical protection, as described further below, and may also be used to increase the cost efficiency and/or performance of coherent optics for point-to-multipoint interrupt applications.

For example, the disclosed technique utilizes a pair of polarizing beamsplitters (or splitters) such that the complementary outputs of a pair of I/Q modulators (one in the X-polarization and the other in the Y-polarization) are used to provide dual outputs of the same coherently modulated optical signal, which effectively doubles the coherent transceiver output power by 3dB without using a 3dB coupler. As another example, dual output and dual input coherent optical transceivers may be implemented using the disclosed techniques. This technique may enable four 400Gb/s or eight 400Gb/s applications while reducing the number of optical components required to enable such applications by, for example, approximately one-half. As another example, the technique allows for implementing a receiver that receives two signals independently without using an additional 3dB coupler (to combine the received signals).

The disclosed techniques may increase the link budget by up to or more than 6dB.

Example System

The following figures illustrate aspects of the disclosed technology. Those of skill in the art will appreciate that the various disclosed components may be electronically coupled by one or more of the disclosed electronics, processors, and computing devices to perform the methods and techniques disclosed herein. For simplicity and clarity, not every electronic or data link is shown.

FIG. 1 is a schematic diagram of a 1+1 protected metropolitan area transport system 100 using pluggable 400G-ZR coherent light technology. Unlike Long Haul (LH) transport networks, which typically use mesh topologies, point-to-point links are often used in metropolitan area networks. As shown in fig. 1, for such point-to-point optical links, 1+1 optical protection (e.g., providing transmission information over separate or protected optical links) may be utilized to minimize the effects of optical fiber link failures.

Shown in fig. 1 is router 110 having ports 111 and 112 and router 195 having ports 191 and 192. Data may be sent from router 110 to router 195 via metropolitan line system 199. The router 110 may be optically connected to a wavelength division multiplexer 120 connected to an optical coupler 130. Optocoupler 130 is connected to Optical Amplifiers (OA) 141 and 142, which OA 141 and 142 are in turn optically connected to 2 by 1 switch 150. The 2 by 1 switch 150 may receive two input signals and output one output signal to a Wavelength Division Multiplexing (WDM) demultiplexer (DeMux), such as WDM DeMux190.WDM DeMux190 can demultiplex the signals it receives into two signals and provide these signals through ports 191 and 192 to router 195. In optical fiber communication, wavelength Division Multiplexing (WDM) is a technique of multiplexing several optical carrier signals onto a single optical fiber by using laser light of different wavelengths or different colors. In some examples, ports 111,112 (or 191, 192) may contain or include transceivers, such as single-output and single-input coherent transceivers, such as those described with respect to fig. 4.

As shown in fig. 1, to achieve 1+1 protection, a 3dB optical coupler splits a wavelength multiplexed optical signal into two paths. One of the two paths may be considered a main signal path and the other path may be considered a protection path. Since a 3dB coupler is required before the optical amplifier, the optical signal to noise ratio (OSNR) of the "transmit" or transmission from router 110 will be reduced by at least 3dB. While this 3dB (or greater) reduction in transmit OSNR may still be manageable for 400G-ZR based metropolitan area systems, at 800G and above, the impact of 3dB or greater reduction on supporting link loss will become proportionally greater. For example, in some cases, the experienced link loss may exceed the required link loss (e.g., 20dB to 16 dB).

Fig. 2 is a schematic diagram of a 1.6Tb/s coherent DR4 optical module design using coherent optical techniques in accordance with aspects of the present disclosure. The splitting capability such as that shown in fig. 2 is not only required in data center networks (such as rack top switch to midblock connections within a data center), but is also useful in mobile front ends as well as in conventional telecommunications and cable access networks.

Shown in fig. 2 is an optical module 299, which optical module 299 may include four coherent transceiver units capable of transmitting and receiving optical signals, such as coherent transceivers 210,220,230, and 240. In some examples, the coherent transceiver may include a separate transmitter (Tx) and receiver (Rx). The total speed of the optical module 299 may be the sum of the coherent transceivers it contains. For example, in FIG. 2, the optical module 299 may have a total speed of 1.6Tb/s, while each coherent transceiver has a speed of 400 Gb/s. A coherent optical transceiver or module may use coherent modulation and may have an electrical interface and an optical interface connected by an optical system, such as by a fiber optic cable.

For a wire-break application such as that shown in fig. 2, the wire-break or fan-out speed is typically four or eight times lower than the optical module speed. Branching may refer to branching or fanout from the entire signal through different optical paths. For example, with coherent light technology, a 1.6Tb/s coherent DR4 optical module would require four sets of 400Gb/s coherent Tx and Rx, while a 3.2Tb/s DR8 optical module would require eight sets of 400Gb/s coherent Tx and Rx. Although not shown in fig. 2 for simplicity, it is difficult to achieve cost effectiveness with this design approach because each set of coherent Tx and Rx requires four optical modulators in addition to four balanced Photodetectors (PD) and transimpedance amplifiers (TIA).

Fig. 3 is a schematic diagram of a digital subcarrier based 1.6Tb/s coherent DR4 optical module design in accordance with aspects of the disclosed technique. Fig. 3 shows an example embodiment of a 1.6Tb/s coherent DR4 optical module design based on digital subcarriers. As shown in fig. 3, data (e.g., data 1 and data 2) may be encoded at different frequencies.

Fig. 3 shows an optical module 399 comprising two 2-subcarrier 800Gb/s coherent transceivers 310 and 320, which coherent transceivers 310 and 320 may be similar to the coherent transceivers described herein. The coherent transceiver 310 may be connected to 3dB optical couplers 331 and 332, while the coherent transceiver 320 may be connected to 3dB optical couplers 333 and 334. The 3dB optical couplers 331-334 may receive one optical signal and transmit two optical signals, and vice versa, receive two optical signals and couple the two signals into one output optical signal. Various paths have been marked with respect to fig. 3. For example, 400G path 1 may include an outgoing signal from 3dB optical coupler 331 and an incoming signal to optical coupler 332.

The digital subcarrier-based embodiment shown in fig. 3 may reduce the required optical components by half by using higher bandwidth components compared to the coherent optical embodiment described with respect to fig. 2. To split the two 800G coherent optical signals modulated by the sub-carriers into four 400G optical signals, 3dB couplers may be introduced at the transmitter and receiver of fig. 3. This may translate into a link budget loss of 6 dB.

Fig. 4 is a schematic diagram of a single-output and single-input coherent transceiver 400. Fig. 4 shows a laser 410 connected to a single output and single input coherent transceiver. The laser 410 is connected to a co-polarized and phase diversity receiver through a Local Oscillator (LO) as part of processing the received signal. Although the laser 410 is shown in a block with other components, it may be located outside of the block, separate from the other components of the coherent transceiver 400. The laser 410 may be any light source including, but not limited to, a laser, a specially designed semiconductor, an incandescent lamp, an electrodeless lamp, or any combination of halogen lamps. As one example, the laser 410 may be a distributed feedback laser. The laser 410 may be electronically controlled to encode signals in pulses or waves of light. The laser 410 may be optically coupled to a modulator.

Laser 410 may be coupled to a Mach-Zehnder modulator (MZM), which is shown in FIG. 4 for simplicity but is not labeled. Each MZM may receive or generate an in-phase (I) component or a quadrature (Q) component of the optical signal generated by laser 410. In addition, each MZM may also receive an "X" or "Y" component or polarization of the emitted light to generate the possibility of in-phase X (Ix), in-phase Y (Iy), quadrature X (Qx), and quadrature Y (Qy). The pi/2 blocks 414,418 introduce a phase difference between the in-phase and quadrature components. As shown in fig. 4, the in-phase and quadrature components have a phase difference of pi/2 (or 90 degrees). The output of the MZM Qx element is input to pi/2 phase rotator 414. Pi/2 phase rotator 414 introduces pi/2 phase differences between the in-phase (Ix) and quadrature (Qx) X components. Similarly, phase rotator 418 introduces a pi/2 phase difference between the in-phase (Iy) and quadrature (Qy) Y components.

The outputs of the MZM and pi/2 boxes are illustratively described as being coupled via crossover points 424,428 and thereafter received at a Polarizing Beam Combiner (PBC) 450. The crossover points 424,428 may each include a 3dB coupler that combines in-phase and quadrature signal components. Thus, the PBC 450 receives in-phase and quadrature components and combines them, and transmits a combined signal. For example, with respect to FIG. 4, PBC 450 combines the Qx and Qy components. The PBC 450 includes a 90 degree polarization rotator that rotates the polarization axis of, for example, X-polarized light onto the y-axis and vice versa. In operation, the PBC 450 is also used to combine the x and y signal components, which may include the same transverse electric mode (TE mode) (or transverse magnetic mode (TM mode)) signals as is practical. TE-to-TM mode (or vice versa) conversion (i.e., polarization conversion) is accomplished within PBC 450. The PBC 450 may be considered as a PBS 450. As will be appreciated by those skilled in the art, a polarizing beam combiner typically performs the function of combining two orthogonal polarizations into a single output signal, while a polarizing beam splitter splits a single input into orthogonal polarization components. Thus, as a practical matter, the same optical path or device may be configured to perform either function.

Receiver 440 may be a co-polarized and phase diversity receiver. Receiver 440 may contain any of the components described below with respect to fig. 6 to allow the receiver to receive an optical signal and convert the optical signal to a digital signal.

Fig. 5 is a schematic diagram of a first example dual output single input coherent optical transceiver or module 500 technique in accordance with aspects of the disclosed technique. Shown in fig. 5 is a laser 510, which may be similar to laser 410, and a receiver 599, which may form an optical module. Receiver 599 may be a co-polarized and phase diversity receiver similar to receiver 440. Laser 510 is optically coupled to several MZMs and, as previously discussed, may be included outside of the box including other elements shown in the figures. As shown in fig. 5, at block 514,518, the outputs of certain MZMs are phase rotated 90 degrees so that there is a pi/2 (or 90 degrees) phase difference between the in-phase and quadrature components. The in-phase and quadrature signals are then combined in 3dB coupler 524,528 with X and Y polarizations (the upper two MZMs for X polarization and the lower two MZMs for Y polarization). PBC 550 may receive in-phase and quadrature y-components, while PBC 560 may receive in-phase and quadrature x-components. PBCs 550,560 include a 90 degree polarization rotator that functions as discussed above. More generally, PBCs 550,560 are used to combine the x and y signal components and each output a transmit signal. Each transmitted signal includes the same information and thus provides the output required for a 1+1 protection scheme.

In contrast to the single-output, single-input coherent transceiver technique shown in fig. 4, in which the in-phase component output by the MZM I/Q modulator is ignored, the coherent transceiver technique of fig. 5 incorporates an additional Polarizing Beam Combiner (PBC) 560 to combine the complementary outputs of the two I/Q modulators, one in the X-polarization and the other in the Y-polarization. Thus, it allows for dual outputs of the same coherent modulated optical signal without using a 3dB coupler, effectively doubling the coherent transceiver output power by 3dB.

Fig. 6 is an enlarged view of the co-polarization and phase diversity receiver 599 of fig. 5. For clarity, not every component may be labeled in FIG. 6.

The receiver 599 may include a Polarizing Beam Splitter (PBS) 502, a1 by 4 splitter 503, a Local Oscillator (LO), 90 degree hybrids 511 and 512, an Optocoupler (OC), a Photodetector (PD) and a transimpedance amplifier (TIA) or a combined PD/TIA, an analog-to-digital converter (ADC), and a Digital Signal Processor (DSP) 520.

PBS502 may receive signals that may be modulated or configured according to a configuration scheme. For example, PBS502 may receive encoded information as an optical signal. PBS502 may split the beam into two orthogonal components. In some examples, PBS502 may be a flat plate beamsplitter or a cube beamsplitter. PBS502 may polarize light into two orthogonal components, such as "X" polarization and "Y" polarization. As used herein, X and Y may represent two orthogonal axes.

The local oscillator may provide (e.g., via a1 by 4 splitter 503) a coherent local reference signal that may propagate to 90 degree hybrids 511 and 512 and may split the x and y polarization components from PBS 502 and the LO. In some examples, blend 511 may obtain an x-related component and blend 512 may obtain a y-related component.

The PD, TIA or PD/TIA may be made of any combination of photodetectors and transimpedance amplifiers. The photodetector may be a semiconductor device that converts light into electrical current. The photodetector may generate a current proportional to the number of photons striking the surface. The photodetector may be used as a sensor for light, since electricity is generated when photons are absorbed in the photodetector. The photodetector may be any device capable of sensing the intensity and/or wavelength of light. The photodetector may be a photodiode or a photosensor. In some examples, a photodetector that is more sensitive to light of a particular wavelength may be selected. In some examples, a photodetector that is more sensitive to green light or only green light may be selected or configured, while another photodetector that is more sensitive to red light or only red light may be configured. The photodetector may also be made of an array of photodetectors. The transimpedance amplifier (TIA) may be a current-to-voltage converter device that may be used to amplify the current output of a photodetector or other photon or light detection device. Thus, the PD/TIA can be used to detect light in both X-polarization and Y-polarization and output a signal for each. As shown in fig. 6, the PD/TIA may be configured to receive signals from 90 degree hybrids 511 and 512. The output of the PD/TIA may be a digital or analog signal.

The signal output from the PD/TIA may be converted by the ADC. The ADC converts the analog signal to a digital signal.

The digital signal processor 520 may receive digital outputs from the ADCs 618-624. Thus, the digital signal processor 520 may be used to extract information encoded in light in a digital format.

Fig. 7 is a schematic diagram of an example 1+1 protection transport system using the proposed dual output and single input coherent light technique (only one direction shown).

Shown in fig. 7 is a system 700, which system 700 may include routers 710 and 790, which may be similar to routers 110 and 195. Each router may contain dual output and single input coherent optical modules, such as module 500 of fig. 5. The system 700 may include multiplexers (Mux) 720 and 721 that may receive multiple input signals and synthesize a single output signal for each input signal in a recoverable manner. For example, as shown in fig. 7, each optical module may provide a signal to each Mux 720 and 721. Mux 720 and 721 may output to optical amplifiers 730 and 731, which optical amplifiers 730 and 731 may be provided to 2 by 1 switch 740. Although a2 by 1 switch is described, other optical switches may be used. An optical amplifier 750 may exist between the switch 740 and the DeMux 780. The switch may provide a signal to DeMux 780, which may be similar to DeMux 190, which DeMux 780 may demultiplex the signals it receives into two signals and provide them to router 790 through module 500.

For example, the dual output single input coherent optical transceiver techniques described herein and shown in fig. 5 and 7 may be used to compensate for transmit OSNR degradation in a 1+1 protection transport system such as that shown in fig. 1. As shown, the redundant output signal is not generated by a separate signal. Instead, it is generated by processing the signal such that the in-phase component is used to enhance the signal output from the optical module. Since each coherent optical module has two outputs carrying substantially the same signal, the 3dB coupler shown in fig. 1 is no longer required to split the original signal for 1+1 protection. The transmit OSNR of fig. 7 may be increased by at least 3dB as compared to the system described with respect to fig. 1.

Fig. 8 illustrates a system 800 that may be used in a dual-output, dual-input coherent optical transceiver technology for a split-line application. For clarity, not every component is labeled with respect to fig. 8 and its components (such as with respect to lasers, MZM, PBC, OC, PD, TIA, ADC, PBS, and DSPs that have been described above with respect to fig. 6).

Similar to fig. 5 and 6, fig. 8 shows a laser connected by a local oscillator to a dual-input polarization and phase diversity coherent receiver 899, and a plurality of MZMs biased in Ix, iy, qx, or Qy, connected via a rotator to a polarization beam combiner to produce a transmit signal, as well as a redundant transmit signal. Receiver 899 may comprise two PBSs that may separate two received signals and be optically connected to a 90 degree hybrid.

In connection with coherent optical modulation techniques, e.g., based on digital subcarriers, the dual-output, dual-input coherent optical transceiver described with respect to fig. 8 is capable of implementing a split-line application of, e.g., four 400Gb/s or eight 400Gb/s while using only half of the optical components compared to the coherent technique shown in fig. 2. The proposed new technology with similar transceiver implementation complexity can increase the link budget by more than 6dB compared to the subcarrier-based design approach shown in fig. 3.

As shown in fig. 8, not only does the transmitter allow dual outputs without requiring an additional 3dB coupler to separate the original signals, but the receiver also allows two independent signals with different center frequencies to be received without requiring an additional 3dB optical coupler to combine the two received signals. As shown in fig. 8, the proposed new transmitter relies on an additional PBC to combine the two otherwise unused complementary signals of the two I/Q modulators for the second output. The proposed receiver receives two independent signals with two complementary inputs mixed at 90 degrees plus an additional PBS. An example implementation of this technique using the proposed dual output and dual input coherent light technique as a 1.6Tb/s coherent DR4 light module design is shown in fig. 9.

Fig. 9 is a schematic diagram of an example 1.6Tb/s coherent DR4 optical module design using a dual output and dual input coherent optical technology system 900. The system 900 may include dual-output and dual-input coherent transceivers 910 and 920, which may be similar to the transceivers described with respect to fig. 8. As shown in FIG. 9, there are four data transmission paths, each operating at 400 Gb/s. As will be appreciated by those skilled in the art, the 3dB coupler is not required in transmissions of the same bandwidth, increasing the optical signal-to-noise ratio of the signals propagating in the system, as compared to fig. 3, which shows a system having the same overall bandwidth.

FIG. 10 is a block diagram 1000 illustrating an example computer system 1010 with which aspects of the disclosure, including the techniques described herein and any components thereof, may be implemented. In certain aspects, the example computer system 1010 may be implemented using hardware or a combination of software and hardware, either in a dedicated server, or integrated into another entity, or distributed across multiple entities. In some examples, the example computer system 1010 may take the form of a digital signal processor, such as the DSP previously discussed. In other examples, an example computing system may include a user computing system or device that interacts with the DSP as previously described.

In general, the computer system 1010 includes at least one processor 1050 for acting upon instructions and one or more memory devices 1070 or caches 1075 for storing instructions and data. The illustrated example computer system 1010 includes one or more processors 1050 that communicate via a bus 1015 with at least one network interface driver controller 1020, a memory device 1070, and any other devices 1080 (e.g., I/O interfaces), the at least one network interface driver controller 1020 having one or more network interface cards 1022 connected to one or more network devices 1024. The network interface card 1022 may have one or more network interface driver ports to communicate with connected devices or components. In general, processor 1050 executes instructions received from memory. The processor 1050 is shown incorporating a cache memory 1075 or directly connected to the cache memory 1075.

In more detail, the processor 1050 may be any logic circuitry that processes instructions (e.g., instructions fetched from the memory device 1070 or cache 1075). In many embodiments, processor 1050 is a microprocessor unit or a special purpose processor. The computer system 1010 may be based on any processor or group of processors capable of operating as described herein. Processor 1050 may be a single-core or multi-core processor. Processor 1050 can be a plurality of processors. In some implementations, the processor 1050 may be configured to run multi-threaded operations. In some implementations, processor 1050 can host one or more virtual machines or containers, along with a hypervisor or container manager for managing the operation of the virtual machines or containers. In such an embodiment, the methods shown and described above or the electronics described above may be implemented within a virtualized or containerized environment provided on the processor 1050 or otherwise operated in conjunction with the processor 1050.

Memory device 1070 may be any device suitable for storing computer readable data. The memory device 1070 may be a device with fixed storage or a device for reading removable storage media. Examples include all forms of non-volatile memory, media, and memory devices; semiconductor memory devices such as EPROM, EEPROM, SDRAM and flash memory devices; and magnetic, magneto-optical disks and optical disks such as CD-ROM, DVD-ROM and Blu-ray disks. The computer system 1010 may have any number of memory devices 1070. In some implementations, the memory device 1070 supports virtualized or containerized memory accessible by virtual machines or container execution environments provided by the computer system 1010.

Cache memory 1075 is typically in the form of computer memory located in close proximity to processor 1050 for fast read times. In some implementations, the cache memory 1075 is part of the processor 1050 or on the same chip as the processor 1050. In some implementations, there are multiple levels of cache 1075, e.g., L2 and L3 cache layers.

The network interface driver controller 1020 manages the exchange of data via a network interface card 1022 (also referred to as a network interface driver port). The network interface driver controller 1020 handles the physical and data link layers of the OSI model for network communications. In some implementations, some tasks of the network interface driver controller are handled by the processor 1050. In some implementations, the network interface driver controller 1020 is part of the processor 1050. In some implementations, the computer system 1010 has a plurality of network interface driver controllers 1020. The network interface driver ports configured in the network interface card 1022 are connection points for physical network links. In some implementations, the network interface driver controller 1020 supports wireless network connections, and the interface ports associated with the network interface cards 1022 are wireless receivers/transmitters. In general, computer system 1010 exchanges data with other network devices 1024 via a physical or wireless link that interfaces with a network interface driver port configured in network interface card 1022. In some implementations, the network interface driver controller 1020 implements a network protocol, such as ethernet.

Other network devices 1024 are connected to computer system 1010 via network interface driver ports included in network interface card 1022. The other network device 1024 may be a peer computing device, a network device, or any other computing device having network functionality. For example, the first network device 1024 may be a network device such as a hub, bridge, switch, or router that connects the computer system 1010 to a data network (such as the internet).

Other devices 1080 may include I/O interfaces, external serial device ports, and any additional coprocessors. For example, the computer system 1010 may include an interface (e.g., a Universal Serial Bus (USB) interface) for connecting an input device (e.g., a keyboard, microphone, mouse, or other pointing device), an output device (e.g., a video display, speaker, or printer), or an additional memory device (e.g., a portable flash drive or external media drive). In some implementations, the computer system 1010 includes additional devices 1080, such as a coprocessor, for example, a math coprocessor may utilize high-precision or complex computations to assist the processor 1050.

Instructions on computer system 1010 may control various components and functions of computer system 1010. For example, the instructions may be executed to perform any of the methods indicated in the disclosure. In some examples, the algorithm may be included as a subset of instructions included on computer system 1010 or otherwise included as part of instructions included on computer system 1010. The instructions may include algorithms to perform any method or subset of methods described within this disclosure.

The user interface on the computer system 1010 may include, for example, inputs, such as a touch screen or buttons, that allow a user to interact with the computer system 1010. A display, such as an LCD, LED, mobile phone display, electronic ink, or other display, may also be included to display information about computer system 1010. The user interface may allow input from a user and output to the user. The communication interface may include hardware and software to enable data communication via standards such as Wi-Fi, bluetooth, infrared, radio waves, and/or other analog and digital communication standards. The communication interface allows the computer system 1010 to be updated and information generated by the computer system 1010 to be shared to other devices. In some examples, the communication interface may send the information stored in the memory to another user device for display, storage, or further analysis.

Aspects of the disclosed technology may include, for example, a dual input polarization and phase diversity receiver. The receiver may include a first polarizing beamsplitter configured to receive a first signal; a second polarizing beamsplitter configured to receive a second signal, wherein the second signal is a redundant replica of the first signal; the first polarizing beam splitter is configured to split the first signal into two components and provide the first component of the first signal to a first 90 degree hybrid first optical coupler and the second component of the first signal to a second 90 degree hybrid second optical coupler; the second polarizing beam splitter is configured to split the second signal into two components and provide a first component of the second signal to the first 90 degree hybrid first optical coupler and a second component of the second signal to the second 90 degree hybrid second optical coupler, and wherein the first 90 degree hybrid first optical coupler and the second 90 degree hybrid second optical coupler are coupled to the local oscillator such that the first 90 degree hybrid and the second 90 degree hybrid output phase or polarization information associated with the first signal. Aspects of the disclosed technology may include an optical transmission system including a dual output transmitter, wherein the system does not use an optical coupler from an optical downstream of a demultiplexer to produce a redundant replica of a signal configured for transmission. The demultiplexer may be a wavelength division multiplexing demultiplexer. The optical transmission system may also include co-polarized and phase diversity receivers. In some examples, the optical transmission system may further include a1 by 4 splitter. The optical transmission system may further comprise a polarizing beam splitter. In some examples, the polarizing beam splitter splits the received signal into a first 90 degree mix and a second 90 degree mix. The two polarizing beamsplitters each include an optical coupler configured to receive a signal from the polarizing beamsplitters.

Aspects of the disclosed technology may include, for example, a dual output transmitter comprising a laser; a plurality of mach-zehnder modulators (MZMs) coupled to the laser, a first optical rotator coupled to a first MZM of the plurality of MZMs, the first optical rotator configured to receive a first portion of the signal and rotate the first portion of the signal by 90 degrees; a second optical rotator coupled to a second MZM of the plurality of MZMs, the second optical rotator configured to receive a second portion of the signal and rotate the second portion of the signal by 90 degrees; a first polarization beam combiner configured to receive first and second orthogonal components of the rotated first and second portions of the signal, the first polarization beam combiner configured to output a first transmit signal, and a second polarization beam combiner configured to receive first and second in-phase components of signals generated from a third and fourth MZM of the plurality of MZMs, the second polarization beam combiner configured to output a second transmit signal; wherein the first transmission signal and the second transmission signal contain equivalent information. The optical transmission system may also be configured such that the system does not use an optical coupler from the optical downstream of the demultiplexer to produce a redundant copy of the signal configured for transmission. The optical transmission system may comprise a demultiplexer, which may be a wavelength division multiplexing demultiplexer. The optical transmission system may also include co-polarized and phase diversity receivers. The optical transmission system may further comprise a1 by 4 splitter. The optical transmission system further comprises a polarizing beam splitter. The optical transmission may include a polarizing beam splitter that may split the received signal into a first 90 degree mix and a second 90 degree mix.

As an example, aspects of the disclosed technology may include an optical transceiver for use in an optical transmission system, wherein the optical transceiver is capable of dual output and dual input. The optical transceiver may include a dual output transmitter and a dual input polarization and phase diversity receiver. The dual output emitter may comprise a laser; a plurality of mach-zehnder modulators (MZMs) optically downstream from the laser, each MZM configured to modulate received light with one of in-phase x, in-phase y, quadrature x, and quadrature y, and output modulated light; at least one optical rotator optically downstream from the plurality of MZMs, the at least one optical rotator configured to receive a signal from only one MZM and configured to rotate the received signal by 90 degrees; a first polarization beam combiner configured to receive in-phase x and quadrature x generated from at least two MZMs of the plurality of MZMs and output a first transmit signal; a second polarization beam combiner configured to receive in-phase x and quadrature x generated from at least two MZMs of the plurality of MZMs and configured to output a second transmit signal; and wherein the first transmit signal and the second transmit signal are copies that are information equivalent to each other. A dual input polarization and phase diversity receiver, and the receiver may include a first polarization beam splitter configured to receive a first received signal; a second polarizing beamsplitter configured to receive a second received signal, wherein the second received signal is a redundant replica of the first received signal; the first polarizing beam splitter is configured to split the first received signal into two components and provide a first component of the first received signal to a first 90 degree hybrid optical coupler and a second component of the first received signal to a second 90 degree hybrid optical coupler; the second polarizing beamsplitter is configured to split the second received signal into two components and to provide a first component of the second received signal to the first 90 degree hybrid optical coupler and a second component of the second received signal to the second 90 degree hybrid optical coupler; and the receiver may be configured to couple to the laser via a local oscillator to recover phase or polarization information via a 1 by 4 module. The optical transmission system does not need to use an optical system to create a redundant copy of the optical signal that is intended to be transmitted. The first polarization beam combiner may be configured to receive in-phase x and quadrature y. The second polarization beam combiner is configured to receive in-phase x and quadrature y. The system may be configured such that the second polarizing beam combiner is configured to receive in-phase x and quadrature y components. The dual output transmitter may be configured such that the transmitter is configured to modulate the in-phase x, in-phase y, quadrature x, and quadrature y components via the MZM, which may be combined in any combination to produce the first transmit signal and the second transmit signal.

Although examples are provided herein with respect to certain speed, bandwidth, and component combinations, those skilled in the art will appreciate that the methods, techniques, and systems described herein may be generalized or scaled across a range of speeds and bandwidths.

While the above examples are given with respect to a particular method of encoding a signal, and are examples, those skilled in the art will appreciate that additional variations and configurations of such a method are possible. Furthermore, the methods and techniques disclosed herein may be combined in various permutations.

Although this disclosure contains many specifics of particular embodiments, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features specific to particular embodiments. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

Similarly, although operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous.

Reference to "or" may be construed as inclusive such that any term described using "or" may indicate any one of a single, more than one, and all of the described terms. The labels "first," "second," "third," etc. do not necessarily imply a sequence of indications and are generally only used to distinguish between the same or similar items or elements.

Various modifications to the embodiments described in the disclosure may be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the claims are not intended to be limited to the embodiments shown herein but are to be accorded the widest scope consistent with the disclosure, principles and novel features disclosed herein.

Claims (18)

1. A dual input receiver, comprising:

a first polarizing beamsplitter configured to receive a first signal; and

A second polarizing beamsplitter configured to receive a second signal, wherein the second signal is a replica of the first signal,

The first polarizing beam splitter is configured to split the first signal into a first component and a second component, and to provide the first component of the first signal to a first 90 degree hybrid first optical coupler, and the second component of the first signal to a second 90 degree hybrid second optical coupler,

The second polarizing beam splitter is configured to split the second signal into two components and provide a first component of the second signal to the first optical coupler of the first 90 degree hybrid and a second component of the second signal to the second optical coupler of the second 90 degree hybrid, and

Wherein the first optical coupler of the first 90 degree hybrid and the second optical coupler of the second 90 degree hybrid are coupled to a local oscillator such that the first 90 degree hybrid and the second 90 degree hybrid output phase or polarization information associated with the first signal.

2. The dual input receiver of claim 1, wherein the first 90 degree hybrid first optocoupler outputs a first coupled signal to a third optocoupler, and the third optocoupler outputs a first set of output signals including at least a portion of output phase or polarization information.

3. The dual input receiver of claim 2, wherein the first 90 degree hybrid first optocoupler outputs a second coupled signal to a fourth optocoupler, and the fourth optocoupler outputs a second set of output signals including at least a portion of the output phase or polarization information.

4. A dual input receiver as claimed in claim 3, wherein the local oscillator outputs one or more local oscillation signals to the third and fourth optocouplers.

5. The dual input receiver of claim 4, further comprising a 1 x 4 splitter coupled to the local oscillator.

6. The dual input receiver of claim 1, wherein the second 90 degree hybrid second optocoupler outputs a third coupled signal to a fifth optocoupler, and the fifth optocoupler outputs a third set of output signals including at least a portion of the output phase or polarization information.

7. The dual input receiver of claim 6, wherein the second 90 degree hybrid second optocoupler outputs a fourth coupled signal to a sixth optocoupler, and the sixth optocoupler outputs a fourth set of output signals including at least a portion of the output phase or polarization information.

8. The dual input receiver of claim 7, wherein the local oscillator outputs one or more local oscillation signals to the fifth optical coupler and the sixth optical coupler.

9. The dual input receiver of claim 8, further comprising a 1 x 4 splitter coupled to the local oscillator.

10. A dual output transmitter, comprising:

A plurality of mach-zehnder modulators (MZMs) configured to receive a laser output signal and to each output a raw in-phase component or a raw quadrature component based on the laser output signal;

a first polarizing beam combiner coupled to the plurality of MZMs and configured to combine a first raw in-phase component and a first raw quadrature component in an X-polarization plane and a Y-polarization plane to generate a first transmit signal, wherein the first raw in-phase component is based on a first signal generated by a first MZM of the plurality of MZMs and the first raw quadrature component is based on a second signal generated by a second MZM of the plurality of MZMs; and

A second polarizing beam combiner coupled to the plurality of MZMs and configured to combine a first complementary in-phase component and a first complementary quadrature component in the X-polarization plane and the Y-polarization plane to produce a second transmit signal, wherein the first complementary in-phase component is based on a third signal generated by a third MZM of the plurality of MZMs and the first complementary quadrature component is based on a fourth signal generated by a fourth MZM of the plurality of MZMs, and

Wherein the first transmit signal and the second transmit signal contain equivalent information.

11. The dual output transmitter of claim 10, wherein the second signal generated by the second MZM of the plurality of MZMs is provided to a first 90 degree phase shifter and the first 90 degree phase shifter is coupled to the first polarization beam combiner through a first optical coupler.

12. The dual-output transmitter of claim 11, wherein the first 90 degree phase shifter is coupled to the first MZM of the plurality of MZMs and configured to receive the first signal.

13. The dual output transmitter of claim 12, wherein the first signal is provided to the first optocoupler.

14. The dual output transmitter of claim 13, wherein the first optical coupler is coupled to the second polarizing beam combiner.

15. The dual output transmitter of claim 10, wherein the fourth signal generated by the fourth MZM of the plurality of MZMs is provided to a second 90 degree phase shifter, and the second 90 degree phase shifter is coupled to the second polarization beam combiner through a second optical coupler.

16. The dual-output transmitter of claim 15, wherein the second 90-degree phase shifter is coupled to the third MZM of the plurality of MZMs and configured to receive the third signal.

17. The dual output transmitter of claim 16, wherein the third signal is provided to the second optocoupler.

18. The dual output transmitter of claim 17, wherein the second optical coupler is coupled to the first polarizing beam combiner.