Dual-output coherent optical technology

Abstract

The proposed technology enables 1+1 optical protection and can improve coherent module output optical power by 3 dB for similar transmitter (Tx) and receiver (Rx) implementation complexity, as well as enabling integration into existing data center formats.

Description

Background Art

[0001] Cross - reference to Related Applications This application is a continuation of U.S. Patent Application No. 17 / 848,948, filed on Jun. 24, 2022, which claims the benefit of the filing date of U.S. Provisional Patent Application No. 63 / 282,416, filed on Nov. 23, 2021, the disclosure of which is incorporated herein by reference.

[0002] Background Coherent optical communication technology typically involves modulating the amplitude and phase of light and transmitting in two polarization states when transporting information via an optical fiber cable. Coherent optical communication technology offers the possibility of utilizing more of the available bandwidth or transmission path of an optical fiber cable than competing technologies. Such communication typically utilizes a coherent optical receiver. In such a receiver, the transmitted signal interferes with the use of a local oscillator (LO), referred to as a coherent receiver, to extract phase information.

[0003] Compared to other forms of optical transmission such as intensity modulation direct detection (IM - DD), coherent optical technology offers numerous advantages. Advantages include high receiver sensitivity, high spectral efficiency (SE), and high tolerance to various linear optical impairments such as fiber chromatic dispersion (CD) and polarization mode dispersion (PMD). In applications where the state of polarization (SOP) is not maintained during transmission, a phase - polarization diversity four - dimensional (4D) vector receiver is typically employed to detect and demodulate the coherently 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 - , and the I for the Y - polarized signal + , I - , Q + , Q -)。The 4D vector receiver is also typically used when the received signal is simply a two-dimensional (2D) modulated optical signal such as a single-polarization (SP) quadrature amplitude modulation (QAM) signal, or a one-dimensional (1D) modulated signal such as an SP pulse amplitude modulation (SP-PAM) signal.

[0004] The pluggable coherent optical technology functions within the boundaries of several design constraints. The first constraint is the link budget issue when using a high bandwidth throughput, such as 800 Gbps (denoted as "G", Gbps or Gb / s) and above in 1+1 protection applications where redundant signals are transmitted in the network. The second constraint is the cost-effectiveness issue in "breakout" applications in point-to-multi-point networks or applications. Another constraint is the relatively tight power loss requirement, which limits the power consumption of the pluggable optical module. In this regard, the module power density has typically been increasing with the growing demand for bandwidth. These, as well as other constraints, are factors to be considered during the module design and deployment of this type of technology. SUMMARY OF THE INVENTION

[0005] Summary Aspects of the disclosed technology include methods, systems, and apparatuses related to pluggable coherent optics. For example, the disclosed technology can include a dual-input receiver or a dual-output transmitter. In other cases, the disclosed technology can include a pluggable coherent transceiver that includes one or more of each of the dual-input receiver and the dual-output transmitter.

[0006] For example, aspects of the disclosed technology can include a dual-input receiver comprising a first polarization beam splitter configured to receive a first signal and a second polarization beam splitter configured to receive a second signal, where the second signal is a replica of the first signal. The first polarization beam splitter can be configured to split the first signal into a first component and a second component and provide the first component of the first signal to a first optical coupler of a first 90-degree hybrid and the second component of the first signal to a second optical coupler of a second 90-degree hybrid. Additionally, the second polarization beam splitter can be configured to split the second signal into two components and provide the first component of the second signal to the first optical coupler of the first 90-degree hybrid and the second component of the second signal to the second optical coupler of the second 90-degree hybrid. Further, the first and second optical couplers of the first and second 90-degree hybrids can be coupled to a local oscillator such that the first and second 90-degree hybrids output phase or polarization information associated with the first signal.

[0007] According to this aspect of the disclosed technology, the first optical coupler of the first 90-degree hybrid outputs a first coupling signal to a third optical coupler, and the third optical coupler outputs a first set of output signals including at least a portion of the output phase or polarization information. Further, the first optical coupler of the first 90-degree hybrid outputs a second coupling signal to a fourth optical coupler, and the fourth optical coupler outputs a second set of output signals including at least a portion of the output phase or polarization information. Additionally, the local oscillator outputs one or more local oscillator signals to the third optical coupler and to the fourth optical coupler. Further, the dual-input receiver can also include a 1×4 splitter coupled to the local oscillator.

[0008] According to this essential aspect of the disclosed technology, the second optical coupler of the second 90-degree hybrid outputs a third coupling signal to a fifth optical coupler, and the fifth optical coupler outputs a third set of output signals including at least a part of the output phase or polarization information. Additionally, the second optical coupler of the second 90-degree hybrid outputs a fourth coupling signal to a sixth optical coupler, and the sixth optical coupler outputs a fourth set of output signals including at least a part of the output phase or polarization information. Moreover, the local oscillator outputs one or more local oscillation signals to the fifth optical coupler and to the sixth optical coupler, and the dual-input receiver can also include a 1×4 splitter coupled to the local oscillator.

[0009] Another aspect of the disclosed technology can include a dual-output transmitter. The dual-output transmitter receives a laser output signal and, based on the laser output signal, includes a plurality of Mach-Zehnder modulators (MZMs) configured to output the original in-phase component and the original quadrature component respectively, and a first polarization beam combiner coupled to the plurality of MZMs and configured to combine the first original in-phase component and the first original quadrature component in the X polarization plane and the Y polarization plane to create a first transmission signal, where in the first transmission signal, the first original in-phase component is based on a first signal generated by a first MZM among the plurality of MZMs and the first original quadrature component is based on a second signal generated by a second MZM among the plurality of MZMs; and a second polarization 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 create a second transmission signal, where in the second transmission signal, the first complementary in-phase component is based on a third signal generated by a third MZM among the plurality of MZMs and the first complementary quadrature component is based on a fourth signal generated by a fourth MZM among the plurality of MZMs. Additionally, the first transmission signal and the second transmission signal contain equivalent information.

[0010] According to the present aspect of the disclosed technology, the second signal generated by the second MZM among the plurality of MZMs is provided to the first 90-degree phase shifter, and the first 90-degree phase shifter is coupled to the first polarization beam combiner through the first optical coupler. Furthermore, the first 90-degree phase shifter can be coupled to the first MZM among the plurality of MZMs and configured to receive the first signal. According to the present aspect of the disclosed technology, the first signal is provided to the first optical coupler, and the first optical coupler is coupled to the second polarization beam combiner.

[0011] According to the present aspect of the disclosed technology, the fourth signal generated by the fourth MZM among the plurality of MZMs is provided to the second 90-degree phase shifter, and the second 90-degree phase shifter is coupled to the second polarization beam combiner through the second optical coupler. In addition, the second 90-degree phase shifter can be coupled to the third MZM among the plurality of MZMs and configured to receive the third signal. Furthermore, the third signal is provided to the second optical coupler, and the second optical coupler is coupled to the first polarization beam combiner.

[0012] The accompanying drawings are not intended to be drawn to scale. In the various drawings, the same reference numerals and notations refer to the same elements. For clarity purposes, not all components are labeled in all the drawings.

Brief Description of the Drawings

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Mode for Carrying Out the Invention

[0014] Detailed Description Overview The disclosed technology improves the coherent module output optical power by 3 dB by using the same laser with similar transmitter (Tx) and receiver (Rx) implementation complexities, enabling integration into existing data center architectures. The increase in module optical power can be used to increase the link loss supported in optical transport systems that require 1+1 optical protection, as will be described in more detail below, and can also be used to improve the cost-effectiveness and / or performance of coherent optical systems in point-to-multi-point breakout applications.

[0015] For example, in the disclosed technology, to achieve dual outputs of the same coherently modulated optical signal, a pair of polarization beam combiners (or splitters) are utilized such that the complementary outputs of a pair of I / Q modulators, one with X polarization and the other with Y polarization, are used, effectively doubling the coherent transceiver output power without using a 3 dB coupler. As another example, dual output and dual input coherent optical transceivers can be implemented using the disclosed technology. The present technology can enable four 400 Gb / s or eight 400 Gb / s applications while reducing the number of optical components required for such applications by, for example, approximately half. As another example, the present technology enables an implementation of a receiver that independently receives two signals without using an additional 3 dB coupler (for combining the received signals).

[0016] The disclosed technology can improve the link budget by 6 dB or more. Exemplary system The following drawings illustrate aspects of the disclosed technology. Those skilled in the art will understand that the various disclosed components can be electronically coupled by one or more of the disclosed electronic devices, processors, and computing devices to implement the methods and techniques disclosed herein. For the sake of brevity and clarity, not all electronic devices or data links are shown.

[0017] FIG. 1 is a schematic diagram of a 1+1 protection metro transport system 100 using pluggable 400G-ZR coherent optical technology. Different from long-haul (LH) transport networks where a mesh topology is typically used, point-to-point links are often used in metro networks. In such point-to-point optical links, as shown in FIG. 1, 1+1 optical protection (e.g., providing transmission information on a separate or protection optical link) can be utilized to minimize the impact of fiber link failures.

[0018] FIG. 1 shows a router 110 with ports 111 and 112, and a router 195 with ports 191 and 192. Data can be transmitted from router 110 to router 195 via a metro line system 199. Router 110 can be optically connected using a wavelength division multiplexer 120 connected to an optical coupler 130. Optical coupler 130 is connected to optical amplifiers (OAs) 141 and 142, which are optically connected to a 2×1 switch 150. The 2×1 switch 150 can receive two input signals and output one output signal towards a wavelength division multiplexing (WDM) demultiplexer (DeMux) such as a WDM DeMux 190. The WDM DeMux 190 can demultiplex the received signal into two signals and provide these signals to router 195 through ports 191 and 192. In optical fiber communication, wavelength division multiplexing (WDM) is a technique for multiplexing several optical carrier signals onto a single optical fiber by using different wavelengths or colors of laser light. In some examples, ports 111, 112 (or 191, 192) can have or include a transceiver such as a single-output single-input coherent transceiver as described with respect to FIG. 4.

[0019] As shown in FIG. 1, to enable 1+1 protection, a 3dB optical coupler splits the wavelength-multiplexed optical signal into two paths. One of these two paths can be considered the primary signal path, and the other can be considered the protection path. Due to the requirement for a 3dB coupler prior to the optical amplifier, the optical signal-to-noise ratio (OSNR) of the optical signal “launched” or transmitted from router 110 is reduced by at least 3dB. Such a 3dB (or more) reduction in the launched OSNR is still manageable in a 400G-ZR-based metro system, but the impact of a reduction of more than 3dB in the supported link loss becomes proportionally larger at 800G and higher speeds. For example, in one case, the experienced link loss may be greater than required (e.g., 20dB to 16dB).

[0020] Figure 2 is a schematic diagram of a 1.6 Tb / s coherent DR4 optical module design using coherent optical technology according to an aspect of the present disclosure. The breakout function as shown in Figure 2 is not only required in data center networks, such as from the top of the rack switch in the data center to the intermediate block connection, but also useful in mobile fronthaul and conventional telephone communication and cable access networks.

[0021] Figure 2 depicts an optical module 299 that can 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 can include an independent transmitter (Tx) and receiver (Rx). The overall speed of the optical module 299 can be the sum of the coherent transceivers it includes. For example, in Figure 2, the optical module 299 can have an overall speed of 1.6 Tb / s, while each coherent transceiver has a speed of 400 Gb / s. The coherent optical transceiver or module can use coherent modulation and can have an electrical interface and an optical interface for connection through an optical system, such as through an optical fiber cable.

[0022] In breakout applications such as those illustrated in Figure 2, the breakout or fanout speed is typically one-fourth or one-eighth of the optical module speed. Breakout can refer to breaking out or fanning out the entire signal through different optical paths. For example, in coherent optical technology, a 1.6Tb / s coherent DR4 optical module requires four sets of 400Gb / s coherent Tx and Rx, while a 3.2Tb / s DR8 optical module requires eight sets of 400Gb / s coherent Tx and Rx. Although not illustrated in Figure 2 for simplicity, in addition to four balanced optical detectors (PDs) and transimpedance amplifiers (TIAs), each set of coherent Tx and Rx may require four optical modulators, so it may be difficult to achieve cost-effectiveness with this design method.

[0023] Figure 3 is a schematic diagram of a digital subcarrier-based 1.6Tb / s coherent DR4 optical module design according to an aspect of the disclosed technology. Figure 3 shows an exemplary implementation of a digital subcarrier-based 1.6Tb / s coherent DR4 optical module design. As illustrated in Figure 3, data (e.g., Data 1 and Data 2) can be encoded at different frequencies.

[0024] Figure 3 illustrates an optical module 399 that includes two 2-subcarrier 800Gb / s coherent transceivers 310 and 320 that may be similar to the coherent transceivers described herein. Coherent transceiver 310 can be connected to 3dB optical couplers 331 and 332, while coherent transceiver 320 can be connected to 3dB optical couplers 333 and 334. The 3dB optical couplers 331 - 334 can receive one optical signal and transmit two optical signals, or vice versa, receive two optical signals and combine them into one output optical signal. Various paths are labeled with respect to Figure 3. For example, the 400G path 1 can include the outward signal from the 3dB optical coupler 331 and the inward signal to the optical coupler 332.

[0025] Compared with the coherent optical implementation form described with respect to FIG. 2, the digital subcarrier-based implementation form shown in FIG. 3 can reduce the required optical components by half through the use of higher bandwidth components. To break out two 800G coherent optical signals modulated by subcarriers into four 400G optical signals, a 3dB coupler can be introduced into both the transmitter and receiver in FIG. 3. This can be converted into a link budget loss of 6dB.

[0026] FIG. 4 is a schematic diagram of a single-output single-input coherent transceiver 400. FIG. 4 illustrates a laser 410 connected to a single-output single-input coherent transceiver. The laser 410 is connected to a common polarization and phase diversity receiver through a local oscillator (LO) as part of the processing of the received signal. The laser 410 is shown within a block together with other components, but may be arranged outside the block separately from other components of the coherent transceiver 400. The laser 410 can be any light source and includes, without limitation, any combination of lasers, specially designed semiconductors, incandescent bulbs, electrodeless lamps, or halogen lamps. As an example, the laser 410 can be a distributed feedback laser. The laser 410 can be electronically controlled to encode signals in optical pulses or light waves. The laser 410 can be optically coupled to a modulator.

[0027] Laser 410 can be coupled to a Mach-Zehnder modulator (MZM) that is shown in FIG. 4 but not labeled for simplicity. Each MZM can receive or generate the in-phase (I) component or the quadrature (Q) component of the optical signal generated by laser 410. Furthermore, each MZM can also receive the "X" or "Y" component or the polarization of the transmitted light and generate the probabilities of in-phase x (Ix), in-phase y (Iy), quadrature x (Qx), and quadrature y (Qy). The π / 2 blocks 414, 418 introduce a phase difference between the in-phase component and the quadrature component. As shown in FIG. 4, the in-phase component and the quadrature component have a π / 2 (i.e., 90-degree) phase difference. The output of the MZM Qx element is the input to the π / 2 phase rotator 414. The π / 2 phase rotator 414 introduces a π / 2 phase difference between the in-phase (Ix) and quadrature (Qx) X components. Similarly, the phase rotator 418 introduces a π / 2 phase difference between the in-phase (Iy) and quadrature (Qy) Y components.

[0028] The outputs of the MZM and π / 2 blocks are illustratively depicted as being combined via crossover points 424, 428 and then received by a polarization beam combiner (PBC) 450. The crossover points 424, 428 can each include a 3 dB coupler that combines in-phase and quadrature signal components. Thus, the PBC 450 receives and combines the in-phase and quadrature components and transmits the combined signal. For example, with respect to FIG. 4, the PBC 450 combines the Qx component and the Qy component. The PBC 450 includes, for example, a 90-degree polarization rotator that rotates the polarization axis of the X-polarized light to the y-axis or vice versa. In operation, the PBC 450 also functions to combine the x signal component and the y signal component, which can, in practice, include the same transverse electric field mode (TE mode) (or transverse magnetic field mode (TM mode)) signal. The conversion from the TE to the TM mode (or vice versa), i.e., the polarization conversion, is performed within the PBC 450. The PBC 450 can be considered as a PBS 450. As would be recognized by one of ordinary skill in the art, a polarization beam combiner generally performs the function of combining two orthogonal polarizations into a single output signal, while a polarization beam splitter splits a single input into orthogonal polarization components. Thus, in practice, the same optical circuit or device can be configured to perform either function.

[0029] The receiver 440 can be a common polarization and phase diversity receiver. The receiver 440 can include any of the components described with respect to FIG. 6 below such that the receiver can receive an optical signal and convert it to a digital signal.

[0030] Figure 5 is a schematic diagram of a first exemplary dual-output single-input coherent optical transceiver or module 500 technology according to an aspect of the disclosed technology. Figure 5 shows a laser 510 that may be similar to laser 410, and a receiver 599 that can form an optical module. Receiver 599 can be a common polarization and phase diversity receiver similar to receiver 440. Laser 510 is optically coupled to several MZMs and may be included outside the block, including other elements shown in the drawing, as previously discussed. As shown in Figure 5, the output of certain MZMs is phase rotated by 90 degrees in blocks 514, 518 so that a phase difference of π / 2 (i.e., 90 degrees) can be created between the in-phase and quadrature components. Thereafter, the in-phase and quadrature signals are combined in 3dB couplers 524, 528 in both X and Y polarizations (the upper two MZMs are for X polarization and the lower two MZMs are for Y polarization). PBC 550 can receive the in-phase and quadrature y components, while PBC 560 can receive the in-phase and quadrature x components. PBCs 550, 560 include 90-degree polarization rotators that function as discussed above. More generally, PBCs 550, 560 function to combine the x and y signal components and output transmission signals respectively. Since each transmission signal contains the same information, it provides the output required for a 1+1 protection scheme.

[0031] Compared to the single-output single-input coherent transceiver technology shown in Figure 4, where the in-phase component output by the MZM I / Q modulator is ignored, the coherent transceiver technology of Figure 5 introduces an additional polarization beam combiner (PBC) 560 to combine the complementary outputs of two I / Q modulators, one in X polarization and the other in Y polarization. This enables a dual output of the same coherently modulated optical signal without using a 3dB coupler, effectively doubling the coherent transceiver output power by 3dB.

[0032] Figure 6 is an enlarged view of the common polarization and phase diversity receiver 599 of Figure 5. For clarity, not all parts in Figure 6 are labeled.

[0033] The receiver 599 can include a polarization beam splitter (PBS) 502, a 1×4 splitter 503, a local oscillator (LO), 90-degree hybrids 511 and 512, an optical coupler (OC), an optical detector (PD) and a trans-impedance amplifier (TIA), or a combined PD / TIA, an analog-to-digital converter (ADC), and a digital signal processor (DSP) 520.

[0034] The PBS 502 can receive a signal that can be modulated or set according to a setting scheme. For example, the PBS 502 can receive encoded information as an optical signal. The PBS 502 can split an optical beam into two orthogonal components. In some examples, the PBS 502 can be a plate-type beam splitter or a cube-type beam splitter. The PBS 502 can polarize light into two orthogonal components such as "X" polarization and "Y" polarization. As used herein, X and Y can represent two orthogonal axes.

[0035] The local oscillator can provide a coherent and local reference signal that can propagate to the 90-degree hybrids 511 and 512 (e.g., via the 1×4 splitter 503), and can separate the x-polarization component and the y-polarization component from the PBS 502 and the LO. In some examples, the hybrid 511 can obtain an x-related component, and the hybrid 512 can obtain a y-related component.

[0036] A PD, TIA, or PD / TIA can be made from any combination of a photodetector and a transimpedance amplifier. The photodetector can be a semiconductor device that converts light into current. The photodetector can generate a current proportional to the number of photons impinging on its surface. When photons are absorbed by the photodetector and electricity is generated, the photodetector can act as a sensor for light. The photodetector can be any device that can sense the intensity and / or wavelength of light. The photodetector can be a photodiode or a photosensor. In some examples, the photodetector can be selected or configured to be more sensitive to a particular wavelength of light. In some examples, the photodetector can be selected or configured to be more sensitive to green light, or to have sensitivity only to green light, while another photodetector can be configured to be more sensitive to red light, or to have sensitivity only to red light. The photodetector can also be made from an array of photodetectors. A transimpedance amplifier (TIA) can be a current-voltage conversion device that can be used to amplify the current output of a photodetector or other photon or light sensing device. Thus, a PD / TIA can be used to detect both X-polarized and Y-polarized light and output their respective signals. As shown in FIG. 6, the PD / TIA can be configured to receive signals from 90-degree hybrids 511 and 512. The output of the PD / TIA can be a digital or analog signal.

[0037] The signal output from the PD / TIA can be converted by an ADC. The ADC converts an analog signal into a digital signal.

[0038] The digital signal processor 520 can receive a digital output from the ADCs 618 - 624. Thus, the digital signal processor 520 can be used to extract information encoded as light in digital format.

[0039] FIG. 7 is a schematic diagram of an exemplary 1+1 protection transport system using the proposed dual output single input coherent optical technology (showing only one direction).

[0040] FIG. 7 illustrates a system 700 that can include routers 710 and 790, which may be similar to routers 110 and 195. Each router can include a dual output single input coherent optical module such as module 500 of FIG. 5. System 700 can include multiplexers (Mux) 720 and 721 that receive multiple input signals and combine them in a way that can recover a single output signal for each input signal. For example, as shown in FIG. 7, each optical module can provide one signal to each of Muxes 720 and 721. Muxes 720 and 721 can output to optical amplifiers 730 and 731, which can be provided to a 2×1 switch 740. Although a 2×1 switch is described, other optical switches can be used. Optical amplifier 750 can be present between switch 740 and DeMux 780. The switch can provide the signal to a DeMux 780, which may be similar to DeMux 190, and this DeMux can demultiplex the received signal into two signals and provide them to router 790 through module 500.

[0041] The dual output single input coherent optical transceiver technology described herein and illustrated in FIGS. 5 and 7 can be used to compensate for the reduction in transmitted OSNR in a 1+1 protection transport system such as that shown in FIG. 1. As shown, redundant output signals are not generated by splitting the signal. Rather, redundant output signals are generated by processing the signal such that the in-phase component is used to boost the signal output from the optical module. Since each coherent optical module has two outputs that carry essentially the same signal, the 3dB coupler of FIG. 1 is no longer needed to split the original signal for 1+1 protection. The transmitted OSNR of FIG. 7 can be improved by at least 3dB compared to the system described with respect to FIG. 1.

[0042] FIG. 8 illustrates a system 800 that is a dual-output dual-input coherent optical transceiver technology that can be used for breakout applications. For clarity, not all components are labeled with respect to FIG. 8 and its components, such as the lasers, MZMs, PBCs, OCs, PDs, TIAs, ADCs, PBSs, and DSPs described above with respect to FIGS. 6, etc.

[0043] FIG. 8, similar to FIGS. 5 and 6, illustrates a laser connected to a dual-input polarization and phase diversity coherent receiver 899 through a local oscillator, and a plurality of MZMs biased to Ix, Iy, Qx, or Qy, some of which are connected to a polarization beam combiner via a rotor to create a transmission signal and a redundant transmission signal. The receiver 899 can split two received signals and can include two PBSs optically connected to a 90-degree hybrid.

[0044] The dual-output dual-input coherent optical transceiver described with respect to FIG. 8, for example, in combination with digital subcarrier-based coherent optical modulation technology, can enable, for example, four 400 Gb / s, or eight 400 Gb / s breakout applications, using only half as many optical components compared to the coherent technique shown in FIG. 2. The proposed novel technique can improve the link budget by more than 6 dB with a similar transceiver implementation complexity compared to the subcarrier-based design method shown in FIG. 3.

[0045] As shown in Fig. 8, the transmitter enables dual output without the need for an additional 3dB coupler to split the original signal, and the receiver also enables the reception of two independent signals with different center frequencies without the need for 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 its two signals into complementary signals that would otherwise be unused by two I / Q modulators for a second output. The proposed receiver utilizes an additional PBS in addition to the two complementary inputs of two 90-degree hybrids to receive two independent signals. An exemplary implementation of this technology is shown in Fig. 9 as a 1.6Tb / s coherent DR4 optical module design using the proposed dual-output dual-input coherent optical technology.

[0046] Fig. 9 is a schematic diagram of an exemplary 1.6Tb / s coherent DR4 optical module design using system 900, which is a dual-output dual-input coherent optical technology. System 900 can include dual-output dual-input coherent transceivers 910 and 920, which can 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. Comparing with Fig. 3 that illustrates a system with the same overall bandwidth, those skilled in the art will understand that no 3dB coupler is required for transmission with the same bandwidth, and the optical signal-to-noise ratio of the signals propagating within the system is increased.

[0047] FIG. 10 is a block diagram 1000 illustrating an exemplary computer system 1010 capable of implementing aspects of the present disclosure, including the techniques described herein, and any components thereof. In some aspects, the exemplary computer system 1010 can be implemented using hardware, or a combination of software and hardware, either integrated on a dedicated server, or integrated with or distributed among multiple entities. In some examples, the exemplary computer system 1010 can take the form of a digital signal processor, such as the DSP discussed above. In other examples, the exemplary computing system can include a user computing system or device that interacts with the DSP discussed above.

[0048] Generally overviewing, the computer system 1010 includes at least one processor 1050 for executing actions according to instructions, and one or more memory devices 1070 or caches 1075 for storing instructions and data. The illustrated exemplary computer system 1010 includes at least one network interface driver controller 1020 that communicates via a bus 1015 and includes one or more processors 1050, with one or more network interface cards 1022 that connect to one or more network devices 1024, memory devices 1070, and any other devices 1080, such as an I / O interface. The network interface card 1022 can have one or more network interface driver ports for communicating with the connected devices or components. Generally, the processor 1050 executes instructions received from memory. The illustrated processor 1050 incorporates or is directly connected to a cache memory 1075.

[0049] More specifically, the processor 1050 can be any logic circuitry that processes instructions fetched from, for example, the memory device 1070 or the cache 1075. In many embodiments, the processor 1050 is a microprocessor unit or a special purpose processor. The computer system 1010 can be based on any processor or set of processors that can operate as described herein. The processor 1050 can be a single-core or multi-core processor. The processor 1050 can be multiple processors. In some implementations, the processor 1050 can be configured to execute multi-threaded operations. In some implementations, the processor 1050 can host one or more virtual machines or containers, in conjunction with a hypervisor or container manager for managing the operation of the virtual machines or containers. In such implementations, the methods or the electronic devices shown and described above can be implemented within a virtualized or containerized environment provided by the processor 1050, or can operate in relation to the processor 1050.

[0050] The memory device 1070 can be any device suitable for storing computer-readable data. The memory device 1070 can be a device with a fixed storage device or a device for reading removable storage media. Examples include any form of non-volatile memory, media, and memory devices, semiconductor memory devices such as EPROM, EEPROM, SDRAM, and flash memory devices, as well as magnetic disks, magneto-optical disks, and optical disks such as CD-ROM, DVD-ROM, and Blu-ray (registered trademark) disks. The computer system 1010 can have any number of memory devices 1070. In some implementations, the memory device 1070 supports virtualized or containerized memory that is accessible by a virtual machine or container execution environment provided by the computer system 1010.

[0051] The cache memory 1075 is in the form of computer memory generally placed very close to the processor 1050 for fast read time. 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, such as L2 and L3 cache layers.

[0052] The network interface driver controller 1020 manages data exchange via the network interface card 1022 (also referred to as the network interface driver port). The network interface driver controller 1020 handles the physical layer and data link layer of the OSI model for network communication. In some implementations, part of the task of the network interface driver controller is 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 multiple network interface driver controllers 1020. The network interface driver port set in the network interface card 1022 is a connection point for the physical network link. In some implementations, the network interface driver controller 1020 supports a wireless network connection and the interface port associated with the network interface card 1022 is a wireless receiver / transmitter. Generally, the computer system 1010 exchanges data with other network devices 1024 via a physical link or wireless link that interfaces with the network interface driver port set in the network interface card 1022. In some implementations, the network interface driver controller 1020 implements network protocols such as Ethernet (registered trademark).

[0053] Other network devices 1024 are connected to the computer system 1010 via network interface driver ports included in the network interface card 1022. The other network devices 1024 may be peer computing devices, network devices, or any other computing device with network capabilities. For example, the first network device 1024 may be a network device such as a hub, bridge, switch, or router that connects the computing system 1010 to a data network such as the Internet.

[0054] The other device 1080 may include an I / O interface, an external serial device port, 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 an additional device 1080 such as a coprocessor, and for example, a math coprocessor can assist the processor 1050 with high-precision or complex calculations.

[0055] The instructions of the computer system 1010 can control various components and functions of the computer system 1010. For example, the instructions can be executed to perform any of the methods shown in this disclosure. In some examples, an algorithm can be included as a subset of the instructions included in the computer system 1010, or as part of the instructions. The instructions can include an algorithm for performing any of the methods or subsets of methods described in this disclosure.

[0056] The user interface of computer system 1010 can include an input that enables a user to interact with the computer system 1010, such as a touch screen or buttons, for example. The display can also include an LCD, LED, cellular phone display, electronic ink, or other display for displaying information about the computer system 1010. The user interface can enable both input from the user and output to the user. The communication interface includes hardware and software and can enable data communication according to standards such as Wi-Fi, Bluetooth®, infrared, radio waves, and / or other analog and digital communication standards. The communication interface enables the computer system 1010 to be updated and enables information generated by the computer system 1010 to be shared with other devices. In some examples, the communication interface can transmit information stored in memory to another user device for display, storage, or further analysis.

[0057] Aspects of the disclosed technology can include, for example, a dual-input polarization and phase diversity receiver. The receiver can include a first polarization beam splitter configured to receive a first signal and a second polarization beam splitter configured to receive a second signal, where the second signal is a redundant copy of the first signal. The first polarization beam splitter can be configured to split the first signal into two components, providing the first component of the first signal to a first optical coupler of a first 90-degree hybrid and the second component of the first signal to a second optical coupler of a second 90-degree hybrid. The second polarization beam splitter can be configured to split the second signal into two components, providing the first component of the second signal to the first optical coupler of the first 90-degree hybrid and the second component of the second signal to the second optical coupler of the second 90-degree hybrid. The first and second optical couplers of the first and second 90-degree hybrids are coupled to a local oscillator such that the first and second 90-degree hybrids output phase or polarization information associated with the first signal. Aspects of the disclosed technology can include an optical transmission system including a dual-output transmitter, where the system does not use an optically downstream optical coupler from a demultiplexer to create a redundant copy of a signal configured for transmission. The demultiplexer can be a wavelength division multiplexing demultiplexer. The optical transmission system can further include a common polarization and phase diversity receiver. In some examples, the optical transmission system can further include a 1×4 splitter. The optical transmission system can further include a polarization beam splitter. In some examples, the polarization beam splitter splits a received signal between a first 90-degree hybrid and a second 90-degree hybrid. Both polarization beam splitters each include an optical coupler configured to receive a signal from the polarization beam splitter.

[0058] Aspects of the disclosed technology can include, for example, a dual-output transmitter. The transmitter includes 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 being configured to receive a first portion of a 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 being 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 being configured to output a first transmission signal, a second polarization beam combiner configured to receive first and second in-phase components of a signal generated from a third MZM and a fourth MZM of the plurality of MZMs, the second polarization beam combiner being configured to output a second transmission signal, and the first transmission signal and the second transmission signal contain equivalent information. The optical transmission system can be further configured such that the system does not use an optical coupler optically downstream from a demultiplexer to create a redundant copy of the signal configured for transmission. The optical transmission system can include a demultiplexer that can be a wavelength division multiplexing demultiplexer. The optical transmission system can further include a common polarization and phase diversity receiver. The optical transmission system can further include a 1×4 splitter. The optical transmission system can further include a polarization beam splitter. The optical transmission can include a polarization beam splitter that can split a received signal into a first 90-degree hybrid and a second 90-degree hybrid.

[0059] As an example, the disclosed technical aspects can include an optical transceiver for use in an optical transmission system, and the optical transceiver can be capable of dual output and dual input. The optical transceiver can include a dual-output transmitter as well as a dual-input polarization and phase diversity receiver. The dual-output transmitter includes a laser and a plurality of Mach-Zehnder modulators (MZMs) optically downstream from the laser, each MZM being configured to modulate received light with one of in-phase x, in-phase y, quadrature x, and quadrature y and output the modulated light; at least one optical rotator optically downstream from the plurality of MZMs, the at least one optical rotator being configured to receive a signal from only one MZM and 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 of the plurality of MZMs and output a first transmission signal; and a second polarization beam combiner configured to receive in-phase x and quadrature x generated from at least two of the plurality of MZMs and output a second transmission signal, where the first transmission signal and the second transmission signal are equivalent replicas with respect to information with each other.A dual-input polarization and phase diversity receiver, the receiver can comprise a first polarization beam splitter configured to receive a first received signal and a second polarization beam splitter configured to receive a second received signal, where the second received signal is a redundant replica of the first received signal. The first polarization beam splitter is configured to split the first received signal into two components and provide the first component of the first received signal to a first 90-degree hybrid optical coupler and the second component of the first received signal to a second 90-degree hybrid optical coupler. The second polarization beam splitter is configured to split the second received signal into two components and provide the first component of the second received signal to the first 90-degree hybrid optical coupler and the second component of the second received signal to the second 90-degree hybrid optical coupler. The receiver can be configured to be coupled to a laser via a local oscillator to recover phase or polarization information via a 1×4 module. The optical transmission system does not need to use an optical system to create a redundant replica of the optical signal intended to be transmitted. The first polarization beam combiner can 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 can be configured such that the second polarization beam combiner is configured to receive an in-phase x component and a quadrature y component. The dual-output transmitter can be configured such that the transmitter can modulate the in-phase x, in-phase y, quadrature x, and quadrature y components in any combination to create a first transmission signal and a second transmission signal via an MZM.

[0060] Examples are provided herein with respect to specific speeds, bandwidths, and combinations of components, but those skilled in the art will appreciate that the methods, techniques, and systems described herein can be generalized or scaled over a range of speeds and bandwidths.

[0061] The above examples are given with respect to a particular way of encoding signals and are examples, but those skilled in the art will understand and appreciate that further variations and settings of such methods are possible. In addition, the methods and techniques disclosed herein can be combined in various permutations.

[0062] This disclosure includes many specific implementation details, but these should not be construed as limitations on the scope of the claimed subject matter, but rather as descriptions of features specific to particular implementations. Some features described in the context of separate implementations herein can also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation can also be implemented separately in multiple implementations or in any suitable sub-combination. Moreover, features may be described as acting in some combinations, and may even initially be claimed as such, but one or more features from the claimed combination may, in some instances, be deleted from the combination, and the claimed combination may be directed to a sub-combination or a variation of a sub-combination.

[0063] Similarly, operations are depicted in the drawings in a particular order, but this should not be construed as a requirement that such operations be performed in the particular order shown, or sequentially, or that all of the illustrated operations be performed, in order to achieve the desired result. In certain circumstances, multitasking and parallel processing may be advantageous.

[0064] The phrase "or, or, or (or)" can be interpreted as inclusive, such that any term described using "or, or, or" indicates one, two or more, and all of the terms being described. Labels such as "first," "second," "third," etc. do not necessarily indicate order and are generally used merely to distinguish similar or like items or elements.

[0065] Various changes to the implementations described in this disclosure may be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other implementations without departing from the spirit or scope of the disclosure. Therefore, the claims are not intended to be limited to the implementations shown herein, but are to follow the broadest scope consistent with the disclosure, the principles, and the novel features disclosed herein.

Claims

1. A dual-input receiver, comprising: a first polarization beam splitter configured to receive a first signal; a second polarization beam splitter configured to receive a second signal, wherein the second signal is a replica of the first signal; and the first polarization beam splitter is configured to split the first signal into a first component and a second component, and provide the first component of the first signal to a first optical coupler of a first 90-degree hybrid and the second component of the first signal to a second optical coupler of a second 90-degree hybrid; the second polarization beam splitter is configured to split the second signal into two components, and provide the first component of the second signal to the first optical coupler of the first 90-degree hybrid and the second component of the second signal to the second optical coupler of the second 90-degree hybrid; a dual-input receiver, wherein the first and second 90-degree hybrids are coupled to a local oscillator so as to output phase or polarization information associated with the first signal through the first and second optical couplers of the first and second 90-degree hybrids.

2. The dual-input receiver according to claim 1, wherein the first optical coupler of the first 90-degree hybrid outputs a first coupling signal to a third optical coupler, and the third optical coupler outputs a first set of output signals including at least a part of the output phase or polarization information.

3. The dual-input receiver according to claim 2, wherein the first optical coupler of the first 90-degree hybrid outputs a second coupling signal to a fourth optical coupler, and the fourth optical coupler outputs a second set of output signals including at least a part of the output phase or polarization information.

4. The dual-input receiver according to claim 3, wherein the local oscillator outputs one or more local oscillation signals to the third optical coupler and the fourth optical coupler.

5. The dual-input receiver according to claim 4, further comprising a 1×4 splitter coupled to the local oscillator.

6. The second optical coupler of the second 90-degree hybrid outputs a third coupling signal to a fifth optical coupler, and the fifth optical coupler outputs a third set of output signals including at least a part of the output phase or polarization information. The dual-input receiver according to any one of claims 2 to 4.

7. The second optical coupler of the second 90-degree hybrid outputs a fourth coupling signal to a sixth optical coupler, and the sixth optical coupler outputs a fourth set of output signals including at least a part of the output phase or polarization information. The dual-input receiver according to claim 6.

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

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

10. A dual-output transmitter, Receives a laser output signal, and based on the laser output signal, a plurality of Mach-Zehnder modulators (MZMs) each set to output an original in-phase component or an original quadrature component, A first polarization beam combiner coupled to the plurality of MZMs and configured to combine a first original in-phase component and a first original quadrature component in the X polarization plane and the Y polarization plane to create a first transmission signal. In the first transmission signal, the first original in-phase component is based on a first signal generated by a first MZM among the plurality of MZMs, and the first original quadrature component is based on a second signal generated by a second MZM among the plurality of MZMs. The first polarization beam combiner, A second polarization 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 create a second transmission signal. In the second transmission signal, the first complementary in-phase component is based on a third signal generated by a third MZM among the plurality of MZMs, and the first complementary quadrature component is based on a fourth signal generated by a fourth MZM among the plurality of MZMs. The second polarization beam combiner A dual-output transmitter comprising the first transmission signal and the second transmission signal containing equivalent information.

11. The dual-output transmitter according to claim 10, wherein the second signal generated by the second MZM among 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 according to claim 11, wherein the first optical coupler is coupled to the first MZM among the plurality of MZMs and is set to receive the first signal.

13. The dual-output transmitter according to claim 12, wherein the first signal is provided to the first optical coupler.

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

15. The dual-output transmitter according to any one of claims 10 to 14, wherein the fourth signal generated by the fourth MZM among 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 according to claim 15, wherein the second 90-degree phase shifter is coupled to the third MZM among the plurality of MZMs and is set to receive the third signal.

17. The dual-output transmitter according to claim 16, wherein the third signal is provided to the second optical coupler.

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

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