Fiber optic transmission system and device

Abstract

The present application relates to a fiber optic transmission system and device. The fiber optic transmission system comprises: an optical frequency comb light source, a first optical splitter, at least two modulation modules, and at least two receivers; the optical frequency comb light source transmits a generated optical frequency comb signal to the first optical splitter; the first optical splitter splits the optical frequency comb signal to obtain a crystal oscillator signal and a light source signal, transmits the crystal oscillator signal to the receivers, and transmits the light source signal to the modulation modules; each modulation module performs signal modulation on the light source signal to obtain a wavelength division multiplexing signal, and transmits the wavelength division multiplexing signal to the corresponding receiver; and the receiver receives and recovers originating data on the basis of the crystal oscillator signal and the wavelength division multiplexing signal.

Description

Optical fiber transmission systems and devices

[0001] Related applications

[0002] This application claims priority to Chinese patent application No. 202311249795.5 filed on September 26, 2023, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of communication technology, and in particular to an optical fiber transmission system and device. Background Art

[0004] Currently, with the penetration of 5G into numerous industries and the widespread adoption of cloud computing in enterprises, global Internet traffic is experiencing explosive growth. Optical communication networks based on traditional single-mode optical fibers are facing an impending capacity crisis. The capacity of a single channel needs to evolve from 100G to 400G, 800G, and even 1.6T. This also means that the bandwidth requirements for electrical / optical devices are becoming increasingly higher. To avoid reliance on high-bandwidth devices, parallel system architectures and multi-dimensional multiplexing technologies are currently commonly used for high-capacity single-fiber optical transmission of the same level. This involves using a single optical frequency comb light source as the transmitter to modulate and multiplex the optical frequency comb carrier signals before transmitting them to the receiver to receive and recover the transmitter data. The receiver then requires an additional local light source to provide a crystal oscillator signal and signal beat frequency close to the frequency of a comb tooth at the transmitter for coherent detection, resulting in higher system costs.

[0005] The above content is only used to assist in understanding the technical solution of this application and does not constitute an admission that the above content is prior art.

[0006] Summary of the Invention

[0007] The main purpose of this application is to provide an optical fiber transmission system and device, which aims to solve the technical problem that an additional local light source is required to provide a crystal oscillator signal for coherent detection during existing optical fiber transmission, resulting in high system costs.

[0008] To achieve the above objectives, the present application provides an optical fiber transmission system, which includes: an optical frequency comb light source, a first optical splitter, at least two modulation modules, and at least two receivers;

[0009] The first optical splitter is connected to the optical frequency comb light source, each modulation module and each receiver respectively, and each receiver is connected to the target transmission device and the corresponding modulation module respectively;

[0010] The optical frequency comb light source is used to transmit the generated optical frequency comb signal to the first optical splitter;

[0011] The first optical splitter is used to split the optical frequency comb signal to obtain a crystal oscillator signal and a light source signal, and transmit the crystal oscillator signal to each of the receivers and transmit the light source signal to each of the modulation modules;

[0012] The modulation module is used to perform signal modulation on the light source signal to obtain a wavelength division multiplexing signal, and transmit the wavelength division multiplexing signal to a corresponding receiver;

[0013] The receiver is used to receive and recover the transmitting end data according to the crystal oscillator signal and the wavelength division multiplexing signal.

[0014] In one embodiment, the modulation module includes: a first wavelength multiplexer, a second wavelength multiplexer, and at least two modulators;

[0015] The first wavelength multiplexer is connected to the first optical splitter and each modulator respectively, and the second wavelength multiplexer is connected to each modulator and the corresponding receiver respectively;

[0016] The first wavelength multiplexer is used to perform wavelength separation on the light source signal to obtain a single-wavelength carrier signal, and transmit the single-wavelength carrier signal to each modulator for signal modulation to obtain a data optical signal;

[0017] The second wavelength multiplexer is used to combine the data optical signals to obtain a wavelength division multiplexing signal, and transmit the wavelength division multiplexing signal to a corresponding receiver.

[0018] In one embodiment, the optical fiber transmission system further comprises: a spatial multiplexer, a space division multiplexing optical fiber, and a spatial demultiplexer;

[0019] The spatial multiplexer is connected to the second wavelength multiplexer and the first optical splitter respectively, and the spatial multiplexer is also connected to the spatial demultiplexer through the spatial division multiplexing optical fiber, and the spatial demultiplexer is connected to each of the receivers;

[0020] The spatial multiplexer is used to multiplex the wavelength division multiplexing signal and the crystal oscillator signal, and transmit the multiplexed wavelength division multiplexing signal and the multiplexed crystal oscillator signal to the spatial demultiplexer through the spatial division multiplexing optical fiber;

[0021] The spatial demultiplexer is used to perform spatial demultiplexing on the multiplexed wavelength division multiplexing signal and the multiplexed crystal oscillator signal, and transmit the spatially demultiplexed wavelength division multiplexing signal and the spatially demultiplexed crystal oscillator signal to each of the receivers.

[0022] In one embodiment, the optical fiber transmission system further comprises: an optical filter and an optical amplifier;

[0023] The optical filter is connected to the spatial demultiplexer and the optical amplifier respectively, and the optical amplifier is connected to each of the receivers;

[0024] The optical filter is used to filter the crystal oscillator signal after the spatial demultiplexing and transmit the filtered crystal oscillator signal to the optical amplifier;

[0025] The optical amplifier is used to amplify the filtered crystal oscillator signal and transmit the amplified crystal oscillator signal to each of the receivers.

[0026] In one embodiment, the optical fiber transmission system further comprises: a second optical splitter;

[0027] Wherein, the second optical splitter is connected to the optical amplifier and each of the receivers respectively;

[0028] The second optical splitter is used to split the amplified crystal oscillator signal to obtain at least two crystal oscillator sub-signals, and transmit the crystal oscillator sub-signals to each of the receivers;

[0029] The receiver is further configured to receive and recover the transmitting end data based on the crystal oscillator signal and the wavelength division multiplexing signal after spatial demultiplexing.

[0030] In one embodiment, the receiver includes: an integrated coherent receiver (ICR) group, an analog-to-digital converter (ADC) group, and a digital signal processor (DSP);

[0031] The ICR group is connected to the first optical splitter, the corresponding modulation module and the ADC group respectively, and the DSP is connected to the ADC group and the target transmission device respectively;

[0032] The ICR group is used to mix the crystal oscillator signal and the wavelength division multiplexing signal to obtain an intermediate frequency signal, and transmit the intermediate frequency signal to the ADC group;

[0033] The ADC group is used to perform analog-to-digital conversion on the intermediate frequency signal to obtain a digital signal, and transmit the digital signal to the DSP;

[0034] The DSP is used to recover the digital signal and obtain the sending end data.

[0035] In one embodiment, the optical fiber transmission system further comprises: at least two third optical splitters and at least two fourth optical splitters;

[0036] The third optical splitter is connected to the corresponding modulation module and the corresponding ICR group respectively, and the fourth optical splitter is connected to the first optical splitter and the corresponding ICR group respectively;

[0037] The third optical splitter is used to split the wavelength division multiplexing signal and transmit the split wavelength division multiplexing signal to the corresponding ICR group;

[0038] The fourth optical splitter is used to split the crystal oscillator signal and transmit the split crystal oscillator signal to the corresponding ICR group.

[0039] In one embodiment, the ICR group includes: a polarization splitter, an optical mixer, and a balanced receiver;

[0040] The polarization splitter is connected to the third optical splitter, the fourth optical splitter and the optical mixer respectively, and the balanced receiver is connected to the optical mixer and the ADC group respectively;

[0041] The polarization separator is used to separate the split crystal oscillator signal and the split wavelength division multiplexing signal to obtain a polarization signal;

[0042] The optical mixer is used to mix the polarization signal and transmit the mixed polarization signal to the balanced receiver;

[0043] The balanced receiver is used to balance the mixed polarization signal to obtain an intermediate frequency signal.

[0044] In one embodiment, the ICR group further includes: a time delay device;

[0045] Wherein, the time delay device is connected to the fourth optical splitter and the polarization separator respectively;

[0046] The time delay device is used to delay the split crystal oscillator signal and transmit the delayed crystal oscillator signal to the polarization separator.

[0047] In addition, to achieve the above-mentioned purpose, the present application also proposes an optical fiber transmission device, which includes the above-mentioned optical fiber transmission system.

[0048] The present application provides an optical fiber transmission system and device, which includes: an optical frequency comb light source, a first optical splitter, at least two modulation modules, and at least two receivers; wherein the first optical splitter is respectively connected to the optical frequency comb light source, each modulation module, and each receiver, and each receiver is respectively connected to a target transmission device and a corresponding modulation module; the optical frequency comb light source is used to transmit a generated optical frequency comb signal to the first optical splitter; the first optical splitter is used to split the optical frequency comb signal to obtain a crystal oscillator signal and a light source signal, and transmit the crystal oscillator signal to each receiver, and transmit the light source signal to each modulation module; the modulation module is used to modulate the light source signal to obtain a wavelength division multiplexing signal, and transmit the wavelength division multiplexing signal to the corresponding receiver; the receiver is used to receive and recover the transmitting end data based on the crystal oscillator signal and the wavelength division multiplexing signal. Since the present application splits the optical frequency comb signal generated by the optical frequency comb light source through the first optical splitter to obtain the crystal oscillator signal and the light source signal, and then transmits the light source signal to each modulation module for signal modulation, and transmits the obtained wavelength division multiplexing signal to each receiver, and at the same time directly transmits the crystal oscillator signal to each receiver, the receiver can receive and recover the transmitting end data according to the crystal oscillator signal and the wavelength division multiplexing signal. Compared with the existing system that requires an additional local light source to provide the crystal oscillator signal, the present application can directly split the optical frequency comb signal generated by the optical frequency comb light source to obtain the crystal oscillator signal, without the need to set up an additional local light source, thereby reducing the system cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] FIG1 is a structural block diagram of a first embodiment of an optical fiber transmission system of the present application;

[0050] FIG2 is a schematic diagram of the optical fiber transmission system of the present application;

[0051] FIG3 is a structural block diagram of a second embodiment of the optical fiber transmission system of the present application;

[0052] FIG4 is a structural block diagram of a third embodiment of the optical fiber transmission system of the present application;

[0053] FIG5 is a connection diagram of a receiver in the third embodiment of the optical fiber transmission system of the present application;

[0054] FIG6 is a schematic diagram of a receiver and a DSP in the optical fiber transmission system of the present application.

[0055] Description of Figure Numbers:

[0056] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0057] It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application.

[0058] The technical solution of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all embodiments obtained by ordinary technicians in this field without making any creative work are within the scope of protection of this application.

[0059] It should be noted that the descriptions of "first" and "second" in the embodiments of this application are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features specified as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions of various embodiments may be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0060] Refer to FIG1 , which is a structural block diagram of a first embodiment of an optical fiber transmission system of the present application.

[0061] As shown in FIG1 , in this embodiment, the optical fiber transmission system includes: an optical frequency comb light source 1, a first optical splitter 2, at least two modulation modules 3, and at least two receivers;

[0062] The first optical splitter 2 is connected to the optical frequency comb light source 1 , each modulation module 3 and each receiver respectively, and each receiver is connected to a target transmission device and a corresponding modulation module 3 respectively.

[0063] It should be noted that the above-mentioned optical fiber transmission system provided in this embodiment can be applied in scenarios where spatial division multiplexing optical fiber communication is realized based on an optical frequency comb light source 1 and self-coherent transceiver. Of course, it can also be used in other optical fiber communication scenarios, and this embodiment does not limit it.

[0064] It is understandable that the above-mentioned optical fiber transmission system may include a transmitting end and a receiving end, wherein the transmitting end may include an optical frequency comb light source 1, a first optical splitter 2 and at least two modulation modules 3. The specific number of modulation modules 3 can be set according to actual conditions. Parallel optical fiber transmission can be achieved through the first optical splitter 2 and multiple modulation modules 3.

[0065] It should be understood that, since this embodiment is based on parallel transmission, the specific number of the above-mentioned receivers can be set according to actual conditions, and one receiver can be connected to one modulation module 3 accordingly.

[0066] Furthermore, the optical frequency comb light source 1 is used to transmit the generated optical frequency comb signal to the first optical splitter 2;

[0067] The first optical splitter 2 is used to split the optical frequency comb signal to obtain a crystal oscillator signal and a light source signal, and transmit the crystal oscillator signal to each of the receivers and transmit the light source signal to each of the modulation modules 3;

[0068] The modulation module 3 is used to modulate the light source signal to obtain a wavelength division multiplexing signal, and transmit the wavelength division multiplexing signal to a corresponding receiver;

[0069] The receiver is used to receive and recover the transmitting end data according to the crystal oscillator signal and the wavelength division multiplexing signal.

[0070] It should also be noted that the optical frequency comb signal generated by the optical frequency comb light source 1 may have M (M>1) comb teeth, each of which may represent a discrete frequency of the optical frequency comb signal. For ease of understanding, reference may be made to FIG2 for illustration. FIG2 is a system schematic diagram of the optical fiber transmission system of the present application. As shown in FIG2 , the optical frequency comb light source 1 (i.e., the optical frequency comb in FIG2 ) may generate an optical frequency comb signal, wherein the comb teeth schematic diagram of the optical frequency comb signal is located above the optical frequency comb, from λ1 to λ M is the wavelength corresponding to each comb tooth of the optical frequency comb signal, and the interval between each comb tooth can be △f.

[0071] It can be understood that the above-mentioned first optical splitter 2 can split the optical frequency comb signal generated by the optical frequency comb light source 1 according to a certain ratio to obtain a number of light source signals corresponding to the number of receivers and a crystal oscillator signal (dashed line in Figure 1). For ease of understanding, the number of receivers can be recorded as n (n>1), and the number of light source signals is also n beams. The number of modulation modules 3 can also be n, that is, the above-mentioned first optical splitter 2 can split the optical frequency comb signal into n+1 beams, and transmit the n beams as light source signals to all modulation modules 3. Each modulation module 3 receives a light source signal as an external light source, and uses the n+1th beam as a crystal oscillator signal, which can be unmodulated or modulated by an ultra-low speed (for example, Kb / s) control signal and then transmitted to each receiver.

[0072] It should be emphasized that in order to enhance the intensity of the optical frequency comb signal, in this embodiment, as shown in FIG2 , a first optical amplifier 101 is further provided between the optical frequency comb light source 1 and the first optical splitter 2. The optical frequency comb signal can be amplified by the first optical amplifier 101 and then transmitted to the first optical splitter 2 for splitting. The first optical amplifier 101 can be a fiber amplifier, or other amplifiers, and this embodiment does not impose any restrictions on this.

[0073] It should be understood that Tx_1, Tx_2, ..., Tx_n in Figure 2 are n modulation modules 3, and the structure within each modulation module 3 can be consistent. In this embodiment, the above-mentioned modulation module 3 can modulate the received RF signal onto the above-mentioned light source signal to obtain a wavelength division multiplexing signal, wherein the RF signal can be obtained by converting the digital signal into an analog signal by the transmitting end (Transmitter, Tx) digital signal processor (Digital Signal Processor, DSP) and the digital-to-analog converter (Digital-to-Analog Converter, DAC), that is, Tx DSP&DACs in Figure 2, and the RF signal is RFs1, RFs2, ..., RFsM in Figure 2.

[0074] It should be noted that the above-mentioned receivers (receiver 1, receiver 2...receiver n in Figure 1) can perform self-coherent detection based on the received crystal oscillator signal and wavelength division multiplexing signal, and then receive and recover the transmitting end data. The above-mentioned transmitting end data can be the user data that the transmitting end needs to transmit, and this specific embodiment is not limited to this.

[0075] In a specific implementation, the optical frequency comb light source 1 can transmit the generated M comb teeth optical frequency comb signals to the first optical splitter 2 after amplification. The first optical splitter 2 splits the optical frequency comb signal into n+1 beams according to a certain ratio, wherein n beams are transmitted to each modulation module 3 respectively as the above-mentioned light source signals, and the n+1th beam is not modulated as the above-mentioned crystal oscillator signal or is modulated by the ultra-low-speed control signal and then transmitted to all receivers. The modulation module 3 transmits the modulated wavelength division multiplexing signal to the corresponding receiver, and then the receiver can perform self-coherence detection based on the crystal oscillator signal and the wavelength division multiplexing signal, thereby receiving and recovering the transmitting end data. Compared with the existing method that requires an additional local light source to generate a crystal oscillator signal, this embodiment can directly use a part of the optical frequency comb signal generated by the optical frequency comb light source 1 as a crystal oscillator signal without the need for an additional local light source, thereby reducing system cost and complexity and facilitating device integration.

[0076] It should also be emphasized that using the same optical frequency comb light source 1 as the crystal oscillator signal of the receiver for self-coherence detection can greatly simplify digital signal processing (no frequency offset).

[0077] Furthermore, in order to realize modulation of the light source signal, as shown in FIG1 , in this embodiment, the modulation module 3 includes: a first wavelength multiplexer, a second wavelength multiplexer and at least two modulators;

[0078] The first wavelength multiplexer is connected to the first optical splitter 2 and each modulator respectively, and the second wavelength multiplexer is connected to each modulator and the corresponding receiver respectively;

[0079] The first wavelength multiplexer is used to perform wavelength separation on the light source signal to obtain a single-wavelength carrier signal, and transmit the single-wavelength carrier signal to each modulator for signal modulation to obtain a data optical signal;

[0080] The second wavelength multiplexer is used to combine the data optical signals to obtain a wavelength division multiplexing signal, and transmit the wavelength division multiplexing signal to a corresponding receiver.

[0081] It should be noted that in this embodiment, multiple modulators can be set in a modulation module 3 to perform independent modulation respectively. The modulator can be a single-bias or double-bias IQ (In-phase and Quadrature) modulator, which can be used to improve bandwidth utilization and transmission capacity, and thus does not require high-bandwidth electro-optical devices. For the convenience of subsequent description, the number of modulators in this embodiment can be recorded as M, that is, modulator 1, modulator 2...modulator M in Figures 1 and 2, and each modulator receives a radio frequency signal, that is, modulator 1 in Figure 2 receives RFs1, modulator 2 receives RFs2, and modulator M receives RFsM.

[0082] It is understandable that since the light source signal of each wavelength needs to be processed differently, the received light source signal can be wavelength-separated by the demultiplexer (De-Multiplexer, De-MUX) in the first wavelength multiplexer to obtain a single-wavelength carrier signal, and the single-wavelength carrier signal is transmitted to the corresponding single-bias or double-bias IQ modulator for modulation. After modulation, each modulator can output the corresponding data optical signal and transmit it to the second wavelength multiplexer.

[0083] It should be understood that in this embodiment, all received data optical signals can be combined into a wavelength division multiplexing signal by the multiplexer (Multiplexer, MUX) in the second wavelength multiplexer, and amplified, that is, amplified by the second optical amplifier 102 in Figure 2, wherein the schematic diagram of the wavelength division multiplexing signal is located in the upper right of the modulation module 3, λ1 to λ M is the wavelength corresponding to each comb tooth of the wavelength division multiplexing signal, and the interval between each comb tooth can be Δf. The above-mentioned second optical amplifier 102 can be a fiber amplifier, and of course it can also be other amplifiers, which is not limited in this embodiment.

[0084] In a specific implementation, at the transmitting end, after receiving the light source signal, the first wavelength multiplexer can perform wavelength separation on the light source signal to obtain M beams of single-wavelength carrier signals, and transmit each single-wavelength carrier signal to the corresponding modulator for modulation. After modulation, each modulator can transmit the obtained data optical signal to the second wavelength multiplexer for merging, and transmit the wavelength division multiplexing signal obtained by each modulation module 3 to the corresponding receiver respectively.

[0085] It should also be emphasized that due to the use of the architecture of this embodiment, when the system needs to be expanded to a new band, the combined transmission of the new and old band signals can be directly achieved through an additional wavelength multiplexer without being affected, thereby improving scalability.

[0086] Furthermore, in order to transmit the wavelength division multiplexing signal and the crystal oscillator signal to the receiver, as shown in FIG1 , in this embodiment, the optical fiber transmission system further includes: a spatial multiplexer 4 , a spatial division multiplexing optical fiber 45 and a spatial demultiplexer 5 ;

[0087] The spatial multiplexer 4 is connected to the second wavelength multiplexer and the first optical splitter 2 respectively, and the spatial multiplexer 4 is also connected to the spatial demultiplexer 5 through the spatial division multiplexing optical fiber 45, and the spatial demultiplexer 5 is connected to each receiver;

[0088] The spatial multiplexer 4 is used to multiplex the wavelength division multiplexing signal and the crystal oscillator signal, and transmit the multiplexed wavelength division multiplexing signal and the multiplexed crystal oscillator signal to the spatial demultiplexer 5 through the spatial division multiplexing optical fiber 45;

[0089] The spatial demultiplexer 5 is used to perform spatial demultiplexing on the multiplexed wavelength division multiplexing signal and the multiplexed crystal oscillator signal, and transmit the spatially demultiplexed wavelength division multiplexing signal and the spatially demultiplexed crystal oscillator signal to each of the receivers.

[0090] It should also be noted that the above-mentioned first optical splitter 2 can transmit the crystal oscillator signal to the spatial multiplexer 4, and at the same time, the second wavelength multiplexer can transmit the wavelength division multiplexing signal to the spatial multiplexer 4. The spatial multiplexer 4 can multiplex the received crystal oscillator signal and each wavelength division multiplexing signal into the spatial division multiplexing optical fiber 45, wherein the spatial division multiplexing optical fiber 45 can be a multi-core single-mode optical fiber, a single-core few-mode optical fiber, a multi-core few-mode optical fiber or an optical fiber bundle composed of single-mode optical fibers. This embodiment can be illustrated using a multi-core single-mode optical fiber. The multi-core single-mode optical fiber has n+1 cores, and the cores are core#1, #2, #n and #n+1 in Figure 2, wherein core#1, #2 and #n in Figure 2 are used to transmit wavelength division multiplexing signals, and #n+1 is used to transmit crystal oscillator signals.

[0091] It can be understood that after passing through the n+1 fiber cores of the multi-core / few-mode optical fiber, it can be transmitted to the spatial demultiplexer 5 to demultiplex the wavelength division multiplexing signal and the crystal oscillator signal to obtain n demultiplexed wavelength division multiplexing signals and 1 demultiplexed crystal oscillator signal.

[0092] It should be emphasized that the above-mentioned spatial multiplexer 4 can be a fan-in fan-out (First-In First-Out, FIFO) device, a mode multiplexer or a combination device, and the spatial demultiplexer 5 can also be a fan-in fan-out (First-In First-Out, FIFO) device, a mode demultiplexer or a combination device. If multi-core single-mode optical fiber is used for transmission, a fan-in fan-out (First-In First-Out, FIFO) device can be used as the above-mentioned spatial multiplexer 4 and spatial demultiplexer 5. If single-core few-mode optical fiber is used for transmission, a mode multiplexer can be used as the above-mentioned spatial multiplexer 4, and a mode demultiplexer can be used as the above-mentioned spatial demultiplexer 5. If multi-core few-mode optical fiber is used for transmission, a combination device of a FIFO device and a mode multiplexer can be used as the above-mentioned spatial multiplexer 4, and a combination device of a FIFO device and a mode demultiplexer can be used as the above-mentioned spatial demultiplexer 5. When a fiber bundle composed of single-mode optical fibers is used for transmission, a parallel optical fiber connector can be used as the above-mentioned spatial multiplexer 4 and spatial demultiplexer 5.

[0093] In a specific implementation, the above-mentioned spatial multiplexer 4 can spatially multiplex the received wavelength division multiplexing signal and crystal oscillator signal, and then transmit them to the wavelength division multiplexing demultiplexer through the n+1 fiber cores of the multi-core / few-mode optical fiber for spatial demultiplexing, and transmit the obtained n spatially demultiplexed wavelength division multiplexing signals and 1 spatially demultiplexed crystal oscillator signal to each receiver, thereby realizing the transmission of the wavelength division multiplexing signal and the crystal oscillator signal to the receiver.

[0094] The optical frequency comb light source 1 of this embodiment can transmit the optical frequency comb signal of the M comb teeth generated after amplification to the first optical splitter 2, and the first optical splitter 2 splits the optical frequency comb signal into n+1 beams according to a certain ratio, wherein the n beams are respectively transmitted to the first wavelength multiplexer in each modulation module 3 as the above-mentioned light source signal, and the n+1th beam is not modulated as the above-mentioned crystal oscillator signal or is modulated by the ultra-low speed control signal and then transmitted to the spatial multiplexer 4. After receiving the light source signal, the first wavelength multiplexer can perform wavelength separation on the light source signal to obtain M beams of single-wavelength carrier signals, and transmit each single-wavelength carrier signal to the corresponding modulator for modulation. After modulation, each modulator can transmit the obtained data optical signal to the second wavelength multiplexer for merging, and transmit the wavelength division multiplexing signal obtained by each modulation module 3 to the space multiplexer 4 respectively. In the multiplexer 4, the spatial multiplexer 4 can spatially multiplex the received wavelength division multiplexing signal and crystal oscillator signal, and then transmit them to the wavelength division multiplexing demultiplexer through the n+1 fiber cores of the multi-core / few-mode optical fiber for spatial demultiplexing, and transmit the obtained n spatially demultiplexed wavelength division multiplexing signals and 1 spatially demultiplexed crystal oscillator signal to each receiver, thereby transmitting the wavelength division multiplexing signal and the crystal oscillator signal to the receiver, and then the receiver can perform self-coherence detection based on the crystal oscillator signal and the wavelength division multiplexing signal, thereby receiving and recovering the transmitting end data. Compared with the existing system that requires an additional local light source to generate a crystal oscillator signal, this embodiment can directly use a part of the optical frequency comb signal generated by the optical frequency comb light source 1 as a crystal oscillator signal without the need to set up an additional local light source, thereby reducing system cost and complexity and making device integration easier.

[0095] Refer to FIG3 , which is a structural block diagram of a second embodiment of the optical fiber transmission system of the present application.

[0096] In order to filter out unnecessary frequency bands in the crystal oscillator signal and retain the frequency bands required by the user, as shown in FIG3 , in this embodiment, the optical fiber transmission system further includes: an optical filter 6 and an optical amplifier;

[0097] The optical filter 6 is connected to the spatial demultiplexer 5 and the optical amplifier respectively, and the optical amplifier is connected to each receiver;

[0098] The optical filter 6 is used to filter the crystal oscillator signal after the spatial demultiplexing and transmit the filtered crystal oscillator signal to the optical amplifier;

[0099] The optical amplifier is used to amplify the filtered crystal oscillator signal and transmit the amplified crystal oscillator signal to each of the receivers.

[0100] It should be noted that the optical filter 6 may be a micro-ring optical filter 6 , or other optical filters 6 , which is not limited in this embodiment.

[0101] It is understandable that the demultiplexed crystal oscillator signal can first be filtered by a micro-ring optical filter 6 with a periodic frequency response. The spacing between the comb teeth of the optical frequency comb after filtering can be N (N>1) times that before filtering. FIG2 shows the case of N=2, that is, the schematic diagrams of the crystal oscillator signal before and after filtering in FIG2 are located below the optical filter 6. The spacing between each comb tooth before entering the optical filter 6 is Δf, and the spacing between each comb tooth after passing through the optical filter 6 is 2Δf.

[0102] It should be emphasized that the user can choose whether to use the optical filter 6 according to actual needs. If there is no need to change the comb tooth interval of the crystal oscillator signal, the optical filter 6 may not be used, thereby reducing the loss of optical power.

[0103] It should be understood that after filtering, the obtained filtered crystal oscillator signal can be transmitted to an optical amplifier for amplification, that is, the third optical amplifier 103 shown in Figure 2. The above-mentioned third optical amplifier 103 can be a fiber amplifier, and of course it can also be other optical amplifiers. This embodiment does not limit this.

[0104] In a specific implementation, the optical filter 6 can filter the demultiplexed crystal oscillator signal, adjust the comb tooth interval to the required comb tooth interval, obtain the filtered crystal oscillator signal, and transmit it to each receiver after amplification by an optical amplifier.

[0105] Furthermore, in order to transmit the crystal oscillator signal to each receiver, as shown in FIG3 , in this embodiment, the optical fiber transmission system further includes: a second optical splitter 7;

[0106] Wherein, the second optical splitter 7 is connected to the optical amplifier and each receiver respectively;

[0107] The second optical splitter 7 is used to split the amplified crystal oscillator signal to obtain at least two crystal oscillator sub-signals, and transmit the crystal oscillator sub-signals to each of the receivers;

[0108] The receiver is further configured to perform optical fiber transmission with the target transmission device according to the crystal oscillator signal and the wavelength division multiplexing signal after spatial demultiplexing.

[0109] It should also be noted that the above-mentioned crystal oscillator sub-signal can be a signal obtained after the crystal oscillator signal is split, and the above-mentioned second splitter 7 can also split the amplified crystal oscillator signal into n beams of crystal oscillator sub-signals according to a certain ratio, and transmit each beam of crystal oscillator sub-signals as a spatial channel to a receiver, so that the receiver can perform self-coherent detection based on the received crystal oscillator sub-signal and the demultiplexed wavelength division multiplexing signal, thereby realizing the reception and recovery of the transmitting end data. The specific ratio is not limited in this embodiment.

[0110] In a specific implementation, the second optical splitter 7 may split the amplified crystal oscillator signal according to a certain ratio, and transmit each obtained crystal oscillator sub-signal to a corresponding receiver.

[0111] It should also be emphasized that to prevent the comb teeth of the local crystal oscillator signal from being superimposed on the baseband signal after the beat of its corresponding received signal spectrum, two wavelength demultiplexers are required before the beat to decompose the signal and select the comb teeth. This coherent detection scheme has two problems: First, the comb tooth frequencies and comb tooth spacing of the optical frequency comb signals at the receiving and transmitting ends cannot be completely aligned, which will introduce frequency offset and require subsequent DSP estimation and compensation. Although the frequency locking method can lock the comb tooth frequency and spacing of the optical frequency comb signal at the receiving end to be consistent with those at the transmitting end, frequency locking introduces additional control circuits, thereby increasing the complexity of the receiver. Second, even if the center frequency of the wavelength demultiplexer is controlled, it will offset the signal center frequency or comb tooth frequency, which will introduce additional performance impairments. In contrast, this embodiment directly uses a portion of the optical frequency comb signal generated by the optical frequency comb light source 1 as a reference signal and selects the comb teeth through the optical filter 6. This can improve the alignment rate of the comb tooth frequency and comb tooth spacing without increasing the complexity of the receiver. At the same time, this embodiment does not require a wavelength demultiplexer at the receiving end, which can reduce performance impairments and further reduce costs.

[0112] In this embodiment, the optical filter 6 can filter the demultiplexed crystal oscillator signal, adjust the comb tooth interval to the required comb tooth interval, obtain the filtered crystal oscillator signal, and amplify it through the optical amplifier and transmit it to the second spectrometer 7. The second spectrometer 7 can split the amplified crystal oscillator signal according to a certain ratio, and transmit each beam of crystal oscillator sub-signals obtained to the corresponding receiver, thereby filtering out unnecessary frequency bands in the crystal oscillator signal.

[0113] As a variant of this embodiment, this embodiment can also directly generate a local crystal oscillator signal through a local light source. There are also two schemes for locally generating the local crystal oscillator signal. One is that the local crystal oscillator signal makes every effort to keep the frequency aligned with the optical frequency comb signal at the transmitting end, and the comb tooth interval is an integer multiple of the transmitting end. The resulting frequency offset can be estimated and compensated in the digital domain at the receiving end; the other is that the frequency and / or phase of the local crystal oscillator signal can be locked to the same as that of the transmitting end by frequency locking or phase locking. In this way, one comb tooth at the transmitting end can be filtered out and sent to the receiving end through optical fiber as a reference carrier frequency for frequency locking or phase locking.

[0114] Refer to FIG4 , which is a structural block diagram of a third embodiment of the optical fiber transmission system of the present application.

[0115] In order to enable the receiver to recover the received optical frequency comb signal, as shown in FIG4 , in this embodiment, the receiver includes: an ICR group, an ADC group, and a DSP;

[0116] The ICR group is respectively connected to the first optical splitter 2, the corresponding modulation module 3 and the ADC group, and the DSP is respectively connected to the ADC group and the target transmission device;

[0117] The ICR group is used to mix the crystal oscillator signal and the wavelength division multiplexing signal to obtain an intermediate frequency signal, and transmit the intermediate frequency signal to the ADC group;

[0118] The ADC group is used to perform analog-to-digital conversion on the intermediate frequency signal to obtain a digital signal, and transmit the digital signal to the DSP;

[0119] The DSP is used to recover the digital signal and obtain the sending end data.

[0120] It should be noted that, as shown in FIG4 , a receiver may include an integrated coherent receiver (ICR) group, an analog to digital converter (ADC) group, and a digital signal processor (DSP). That is, receiver 1 in FIG2 may include ICR group 1, ADC group 1, and DSP; receiver 2 may include ICR group 2, ADC group 2, and DSP; and receiver n may include ICR group n, ADC group n, and DSP.

[0121] It is understandable that the above-mentioned ICR group can mix the crystal oscillator signal and the demultiplexed wavelength division multiplexing signal, and transmit the obtained intermediate frequency signal to the ADC group. The ADC group performs analog-to-digital conversion on the intermediate frequency signal to obtain a digital signal, and then restores the digital signal through DSP to obtain a restored optical frequency comb signal, so as to perform optical fiber transmission based on the restored optical frequency comb signal.

[0122] Further, in order to improve parallelization, as shown in FIG5 , FIG5 is a connection diagram of a receiver in the third embodiment of the optical fiber transmission system of the present application; As shown in FIG5 , the optical fiber transmission system further includes: at least two third optical splitters 8 and at least two fourth optical splitters 9;

[0123] The third optical splitter 8 is connected to the corresponding modulation module 3 and the corresponding ICR group respectively, and the fourth optical splitter 9 is connected to the first optical splitter 2 and the corresponding ICR group respectively;

[0124] The third optical splitter 8 is used to split the wavelength division multiplexing signal and transmit the split wavelength division multiplexing signal to the corresponding ICR group;

[0125] The fourth optical splitter 9 is used to split the crystal oscillator signal and transmit the split crystal oscillator signal to the corresponding ICR group.

[0126] It should be understood that one receiver may correspond to one third optical splitter 8 and one fourth optical splitter 9, and thus in this embodiment, n third optical splitters 8 and n fourth optical splitters 9 may be provided. At the same time, the ICR group in one receiver may consist of K ICRs, and the ADC group in one receiver may consist of K ADCs, that is, the receiver corresponding to each spatial channel consists of K ICRs, K ADCs, and one DSP.

[0127] It should also be noted that, as shown in Figure 5, in this embodiment, the third optical splitter 8 can be connected to the spatial demultiplexer 5, and then the spatial demultiplexer 5 transmits the demultiplexed wavelength division multiplexing signal to the third optical splitter 8 of each receiver. The third optical splitter 8 splits it into K-way split wavelength division multiplexing signals, and transmits each split wavelength division multiplexing signal to the corresponding ICR; the fourth optical splitter 9 can be connected to the second optical splitter 7, and the second optical splitter 7 splits the amplified crystal oscillator signal into n-way crystal oscillator sub-signals, and transmits each crystal oscillator sub-signal to the fourth optical splitter 9 of each receiver. The fourth optical splitter 9 splits it into K-way split crystal oscillator sub-signals, and transmits each split crystal oscillator sub-signal to the corresponding ICR.

[0128] It should also be emphasized that in order to align the polarization state of the crystal oscillator signal with the polarization state of the wavelength division multiplexing signal, as shown in Figure 5, this embodiment is also provided with a polarization controller between the second splitter 7 and the fourth splitter 9. The polarization controller can be used to track and control the polarization of the crystal oscillator signal. Regarding the specific implementation of the polarization controller, this embodiment does not limit it.

[0129] In a specific implementation, the third optical splitter 8 can split the received demultiplexed wavelength multiplexing signal and transmit the split wavelength multiplexing signal to the ICR. At the same time, the fourth optical splitter 9 can split the received crystal oscillator sub-signal and transmit the split crystal oscillator sub-signal to the ICR. Since in this embodiment, an ICR group consists of K ICRs and an ADC group consists of K ADCs, and they are connected through the third optical splitter 8 and the fourth optical splitter 9, parallelization can be further improved.

[0130] Furthermore, in order to recover the received optical frequency comb signal, in this embodiment, the ICR group includes: a polarization splitter, an optical mixer, and a balanced receiver;

[0131] The polarization splitter is connected to the third optical splitter 8, the fourth optical splitter 9 and the optical mixer respectively, and the balanced receiver is connected to the optical mixer and the ADC group respectively;

[0132] The polarization separator is used to separate the split crystal oscillator signal and the split wavelength division multiplexing signal to obtain a polarization signal;

[0133] The optical mixer is used to mix the polarization signal and transmit the mixed polarization signal to the balanced receiver;

[0134] The balanced receiver is used to balance the mixed polarization signal to obtain an intermediate frequency signal.

[0135] For ease of understanding, reference is made to Figure 6 for explanation. Figure 6 is a schematic diagram of a receiver and a DSP in the optical fiber transmission system of the present application, as shown in Figure 6, wherein (a) in Figure 6 is a detailed schematic diagram of the ICR group, the ADC group and the DSP; (b) in Figure 6 is a schematic diagram in which the comb tooth interval of the crystal oscillator signal is kept the same as the optical frequency comb signal interval at the transmitting end; (c) in Figure 6 is a schematic diagram in which the comb tooth interval of the crystal oscillator signal is twice the optical frequency comb signal interval at the transmitting end; and (d) in Figure 6 is a schematic diagram in which the comb tooth interval of the crystal oscillator signal is three times the optical frequency comb signal interval at the transmitting end.

[0136] First, as shown in (a) of Figure 6, in this embodiment, the ICR group within a receiver may be composed of K ICRs, namely ICR1, ICR2, ..., ICRK in Figure 6. The ICR used in this embodiment may be a classic ICR, namely, composed of two polarization splitters, two 90° optical mixers, and four balanced photodiodes (BPDs). At the same time, an adaptive polarization controller may be provided to connect to the local crystal oscillator within the receiver (as shown in Figure 5) to ensure that the received crystal oscillator signal and the received wavelength division multiplexing signal have the same polarization.

[0137] It should be emphasized that this embodiment can also be implemented without an adaptive polarization controller, that is, by combining a polarization coherent receiver with a Stokes vector receiver (SVR) and five balanced receivers. Polarization tracking and compensation can be performed in the digital domain. This embodiment is described using the former solution.

[0138] It should be noted that the above-mentioned two polarization separators can separate the different polarization states in the split crystal oscillator signal and the split wavelength division multiplexing signal, so that each separated signal contains a specific polarization state, thereby obtaining two polarization signals with different polarization states; the polarization signals are then transmitted to two 90° optical mixers respectively. The 90° optical mixers use a 90° phase difference and spot multiplexing technology to separate the input polarization signal into a real part and an imaginary part. One of the 90° optical mixers has a phase difference of 0°, which is used to extract the I signal, and the other processes a signal with a phase difference of 90°, which is used to extract the Q signal, thereby generating the above-mentioned mixed polarization signal; finally, the mixed polarization signal is transmitted to four balanced receivers respectively for balancing, eliminating interference, and obtaining the above-mentioned intermediate frequency signal.

[0139] It is understandable that the intermediate frequency signal is then transmitted to the corresponding ADC for analog-to-digital conversion to obtain a digital signal I X , Q X , I Y and Q Y And transmit the digital signal to DSP, that is, ICR1 in Figure 6 corresponds to I 1X , Q 1X , I 1Y and Q 1Y , ICR2 corresponds to I 2X , Q 2X , I 2Y and Q 2Y , ICRK corresponding to obtain I KX , Q KX , I KY and Q KY , and transmitted to DSP.

[0140] It should be understood that in the DSP, as shown in FIG6 , dispersion can first be eliminated through a dispersion estimation and compensation unit (CD comp in FIG6 ). Then, the sampling rate of the receiving-end ADC is synchronized to the transmitting-end DAC through a clock recovery module (TR), and the sampling phase is optimized to the optimal sampling point. Then, a fast Fourier transform operation (FFT in FIG6 ) is performed to convert the signal into the frequency domain, and a multi-input multi-output equalizer (MIMO in FIG6 ) is used to separate the signals corresponding to different comb frequency bands. Taking the case shown in FIG6 (a) as an example, the signals after detection of the vth channel (v=1, 2, 3, ..., K) are marked as:

[0141] Since the received signal S(t) is related to the comb frequency f of multiple crystal oscillator signals u (u=1,2,3,…,M) beat the frequency simultaneously and then down-convert it to baseband. The detection signal is actually the received signal spectrum S(f) with multiple frequency shift signals S(f+f u). Considering the bandwidth limitation and low-pass filtering of ICR, the spectrum of K-channel baseband signal U recorded by ADC is v (f) can be expressed in matrix form as follows:

[0142] Among them G vX / Y (f) represents the electrical noise of the corresponding v-th signal receiver, while the optical noise is considered to be part of the signal itself that is counted into the receiver. Assuming that the noise is white noise within the receiver bandwidth spectrum, the signal can be recovered using the least-squares method, that is, calculating the generalized / pseudo-inverse matrix H of the frequency domain channel response matrix + (f)=(H H (f)H(f)) - H H (f), where H H (f) is the conjugate transposed matrix of H(f), and then the least squares method is obtained as follows: S est (f) = H + (f)U(f)=S(f)+H(f)G(f), for |f|≤B (Formula 3);

[0143] It can be seen that the restored signal S est (f) is interfered by noise, and the noise may be equalized by the response H + (f) Amplification. In practical applications, the pseudo-inverse channel response matrix can be solved using a special training sequence or by updating the pseudo-inverse channel response matrix coefficients using the least mean square (LMS) adaptive algorithm. By removing all elements with the 'Y' subscript from the vectors or matrices in Equation 2 above, Equation 2 simplifies from the dual-polarization multiplexing case to the single-polarization coherent modulation and detection case.

[0144] It should be emphasized that the pseudo-inverse matrix of the channel frequency response matrix H(f) can be obtained only if the number of ICRs K is not less than the number of crystal oscillator signal teeth, that is, K ≥ M. When the crystal oscillator signal tooth spacing is equal to the transmit optical frequency comb signal tooth spacing, as shown in (b) of Figure 6, the crystal oscillator signal tooth spacing is the same as the transmit optical frequency comb signal tooth spacing; when the crystal oscillator signal tooth spacing is greater than the transmit optical frequency comb signal tooth spacing, as shown in (c) and (d) of Figure 6, the number of crystal oscillator signal tooth spacing is reduced accordingly. In this case, the ICR and ADC bandwidth can be increased accordingly, and the number of ICRs and ADCs can be reduced several times, which can greatly reduce the cost and power consumption of the receiving system while also retaining sufficient flexibility for system upgrades.

[0145] It should be noted that in the scenarios shown in (c) and (d) of FIG6 , each of the signals output after MIMO separates the signals corresponding to different comb frequency bands is a subcarrier modulation (SCM) signal, that is, a signal containing two or more complete adjacent wavelength channels. This depends on the size of the ICR bandwidth B. In (c) and (d) of FIG6 , the MIMO output SCM signals for each channel contain two and three independent signals respectively, although both use a bandwidth B slightly larger than 1.5 times f FSR The receiver ICR, where f FSR = the comb spacing of the received crystal oscillator signal. A demultiplexing module (De-MUX in Figure 6) then further separates the SCM signal's various frequency bands by directly extracting the sampling points of the corresponding frequency bands in the frequency domain. If the demultiplexed signal is not within the baseband frequency portion of the SCM signal, it undergoes a further phase rotation to shift it to baseband.

[0146] After the signals corresponding to each transmit optical frequency comb tooth frequency are frequency-shifted to the baseband and separated, 2×2 MIMO is used to further compensate for residual dispersion, residual modal dispersion (PMD), and residual state of polarization (SOP) rotation. Each baseband signal is then converted to the time domain for carrier phase recovery (CPR) using inverse fast Fourier transform (IFFT). The recovered quadrature amplitude modulation (QAM) signal is then restored to bit data through symbol-to-bit mapping (i.e., the QAM in Figure 6). -1 ), thereby restoring the originating data.

[0147] It should be emphasized that by filtering the periodic frequency of the crystal oscillator signal through the optical filter 6, the number of ICRs in the receiver can be reduced accordingly, thereby reducing power consumption and cost, and retaining sufficient flexibility for system upgrades.

[0148] It's also important to emphasize that, based on the aforementioned DSP processing flow at the receiver, the DSP primarily uses a frequency-domain MIMO equalization algorithm to decompose the baseband signals corresponding to each optical frequency comb tooth. When the comb tooth spacing of the crystal oscillator signal is N times that of the transmit optical frequency comb (N ≥ 2), the frequency-domain MIMO algorithm first decomposes all received signals into multiple signals with n consecutive signal spectra. Each such signal is then decomposed in the frequency domain into an integer number of independent baseband signals. This architecture offers significant flexibility and can be adapted to the transceiver hardware configuration.

[0149] As a variant of this embodiment, this embodiment can splice / segment the system shown in Figure 2 through a combiner / demultiplexer for post-processing. Specifically, several optical frequency comb signals with different bands but the same comb tooth spacing and phase can be generated at the transmitting end. After modulation, they are combined together through a combiner and then transmitted to the receiving end via the spatial division multiplexing optical fiber. The receiving end can process and recover the signals of all wavelength signals of each spatial signal in one receiver as shown in Figure 2, or use a demultiplexer to decompose the wavelength of each spatial signal into several bands, and then process and recover the signals of each band according to the receiver shown in Figures 2 and 6, thereby reducing the complexity of the receiver.

[0150] Furthermore, in order to introduce different delay times so that each ICR receives crystal oscillator signals of different phases during processing, as shown in FIG5 , in this embodiment, the ICR group further includes: a time delay device;

[0151] Wherein, the time delay device is connected to the fourth optical splitter 9 and the polarization separator respectively;

[0152] The time delay device is used to delay the split crystal oscillator signal and transmit the delayed crystal oscillator signal to the polarization separator.

[0153] It is understandable that, as shown in FIG5 , each ICR is connected to a time delay device, namely, time delay device 1, time delay device 2, ..., time delay device K in FIG5 , and DE1, DE2, ..., DE in FIG6 . K The time delay of each time delay device may be different, and the time delay device may be integrated into the third optical splitter 8 or the receiver, which is not limited in this embodiment.

[0154] In a specific implementation, the split crystal oscillator signal can be delayed by a time delay device in each channel and transmitted to each ICR, so that each ICR receives a crystal oscillator signal with a different phase during processing.

[0155] This embodiment can improve the flexibility of the receiving end through the above-mentioned architecture. At the same time, this embodiment can also perform bit restoration processing to recover the data of the sending end.

[0156] To achieve the above objectives, the present application further provides a fiber optic transmission device, comprising the fiber optic transmission system described above. The specific structure of the fiber optic transmission system is described with reference to the above embodiments. Since the present fiber optic transmission device utilizes all the technical solutions of all the above embodiments, it at least possesses all the beneficial effects brought about by the technical solutions of the above embodiments, and therefore will not be further elaborated here.

[0157] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, circuit, article, or system comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, circuit, article, or system. In the absence of further limitations, an element defined by the phrase "comprising a..." does not exclude the presence of other identical elements in the process, circuit, article, or system comprising the element.

[0158] The serial numbers of the above embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0159] The above are merely optional embodiments of the present application and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. An optical fiber transmission system, wherein: The optical fiber transmission system comprises: an optical frequency comb light source, a first optical splitter, at least two modulation modules and at least two receivers; The first optical splitter is respectively connected to the optical frequency comb light source, each modulation module and each receiver, and each receiver is respectively connected to the target transmission device and the corresponding modulation module; The optical frequency comb light source is used to transmit the generated optical frequency comb signal to the first optical splitter; The first optical splitter is used to split the optical frequency comb signal to obtain a crystal oscillator signal and a light source signal, and transmit the crystal oscillator signal to each of the receivers and transmit the light source signal to each of the modulation modules; The modulation module is used to perform signal modulation on the light source signal to obtain a wavelength division multiplexing signal, and transmit the wavelength division multiplexing signal to a corresponding receiver; The receiver is used to receive and recover the transmitting end data according to the crystal oscillator signal and the wavelength division multiplexing signal.

2. The optical fiber transmission system according to claim 1, wherein: The modulation module includes: a first wavelength multiplexer, a second wavelength multiplexer and at least two modulators; The first wavelength multiplexer is connected to the first optical splitter and each modulator respectively, and the second wavelength multiplexer is connected to each modulator and a corresponding receiver respectively; The first wavelength multiplexer is used to perform wavelength separation on the light source signal to obtain a single-wavelength carrier signal, and transmit the single-wavelength carrier signal to each modulator for signal modulation to obtain a data optical signal; The second wavelength multiplexer is used to combine the data optical signals to obtain a wavelength division multiplexed signal, and transmit the wavelength division multiplexed signal to a corresponding receiver.

3. The optical fiber transmission system according to claim 2, wherein: The optical fiber transmission system further comprises: a spatial multiplexer, a space division multiplexing optical fiber and a spatial demultiplexer; The spatial multiplexer is connected to the second wavelength multiplexer and the first optical splitter respectively, the spatial multiplexer is also connected to the spatial demultiplexer through the spatial division multiplexing optical fiber, and the spatial demultiplexer is connected to each of the receivers; The spatial multiplexer is used to multiplex the wavelength division multiplexing signal and the crystal oscillator signal, and transmit the multiplexed wavelength division multiplexing signal and the multiplexed crystal oscillator signal to the spatial demultiplexer through the spatial division multiplexing optical fiber; The spatial demultiplexer is used to demultiplex the multiplexed wavelength division multiplexing signal and the multiplexed crystal oscillator signal. The spatial demultiplexing is performed, and the wavelength division multiplexing signal after the spatial demultiplexing and the crystal oscillator signal after the spatial demultiplexing are transmitted to each of the receivers.

4. The optical fiber transmission system according to claim 3, wherein: The optical fiber transmission system further includes: an optical filter and an optical amplifier; Wherein, the optical filter is connected to the spatial demultiplexer and the optical amplifier respectively, and the optical amplifier is connected to each of the receivers; The optical filter is used to filter the crystal oscillator signal after the spatial demultiplexing, and transmit the filtered crystal oscillator signal to the optical amplifier; The optical amplifier is used to amplify the filtered crystal oscillator signal and transmit the amplified crystal oscillator signal to each of the receivers.

5. The optical fiber transmission system according to claim 4, wherein: The optical fiber transmission system further comprises: a second optical splitter; Wherein, the second optical splitter is connected to the optical amplifier and each of the receivers respectively; The second optical splitter is used to split the amplified crystal oscillator signal to obtain at least two crystal oscillator sub-signals, and transmit the crystal oscillator sub-signals to each of the receivers; The receiver is also used to receive and restore the transmitting end data according to the crystal oscillator signal and the wavelength division multiplexing signal after spatial demultiplexing.

6. The optical fiber transmission system according to any one of claims 1 to 5, wherein: The receiver includes: an integrated coherent receiver (ICR) group, an analog-to-digital converter (ADC) group, and a digital signal processor (DSP); The ICR group is respectively connected to the first optical splitter, the corresponding modulation module and the ADC group, and the DSP is respectively connected to the ADC group and the target transmission device; The ICR group is used to mix the crystal oscillator signal and the wavelength division multiplexing signal to obtain an intermediate frequency signal, and transmit the intermediate frequency signal to the ADC group; The ADC group is used to perform analog-to-digital conversion on the intermediate frequency signal to obtain a digital signal, and transmit the digital signal to the DSP; The DSP is used to recover the digital signal to obtain the sending end data.

7. The optical fiber transmission system according to claim 6, wherein: The optical fiber transmission system further comprises: at least two third optical splitters and at least two fourth optical splitters; Wherein, the third optical splitter is respectively connected to the corresponding modulation module and the corresponding ICR group, and the fourth optical splitter is respectively connected to the first optical splitter and the corresponding ICR group; The third optical splitter is used to split the wavelength division multiplexing signal and transmit the split wavelength division multiplexing signal to the corresponding ICR group; The fourth optical splitter is used to split the crystal oscillator signal and transmit the split crystal oscillator signal to the corresponding ICR group.

8. The optical fiber transmission system according to claim 7, wherein: The ICR group includes: a polarization splitter, an optical mixer and a balanced receiver; Wherein, the polarization separator is connected to the third optical splitter, the fourth optical splitter and the optical mixer respectively, and the balanced receiver is connected to the optical mixer and the ADC group respectively; The polarization separator is used to separate the split crystal oscillator signal and the split wavelength division multiplexing signal to obtain a polarization signal; The optical mixer is used to mix the polarization signal and transmit the mixed polarization signal to the balanced receiver; The balanced receiver is used to balance the mixed polarization signal to obtain an intermediate frequency signal.

9. The optical fiber transmission system according to claim 8, wherein: The ICR group also includes: a delay device; Wherein, the time delay device is connected to the fourth optical splitter and the polarization separator respectively; The time delay device is used to delay the split crystal oscillator signal and transmit the delayed crystal oscillator signal to the polarization separator.

10. An optical fiber transmission device, wherein: The optical fiber transmission device comprises the optical fiber transmission system according to any one of claims 1 to 9.

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