Synchronous merging transmission method and device based on multi-core optical fiber

Abstract

The invention belongs to the technical field of optical fiber communication, and relates to a synchronous merging transmission method and device based on a multi-core optical fiber. The transmission method comprises the steps that N laser beams containing modulated communication signals and reference signals at the same time are emitted, the N laser beams are correspondingly injected into N fiber cores of an N-core optical fiber respectively, and the N laser beams are output after being transmitted through the N-core optical fiber; decoupling a communication signal and a reference signal from each output laser beam, and taking the reference signal corresponding to one laser beam as a benchmarking reference signal; performing frequency mixing and phase discrimination on the reference signals corresponding to the other beams of laser and the benchmarking reference signal independently to obtain error signals; compensating delay differences corresponding to the other fiber cores according to the error signals so as to enable phases of communication signals output by the fiber cores to be aligned; and coherently combining the communication signals after phase alignment. The transmission device comprises a transmitting end, an N-core optical fiber, a receiving end and a delay compensation structure. According to the invention, the delay difference between the fiber cores can be compensated adaptively in real time, and a stable high signal-to-noise ratio transmission effect is realized.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and in particular to a synchronous merging transmission method and device based on multi-core optical fibers. Background Art

[0002] In recent years, the emergence of new network applications such as high-definition video, big data, and super artificial intelligence has driven rapid growth in global internet traffic demand. As the cornerstone of modern communications networks, fiber-optic communication technology has consistently pursued higher communication capacity. According to Shannon's theorem, improving the received signal-to-noise ratio (SNR) is a key approach to increasing communication capacity. However, the nonlinear effects of traditional single-mode optical fiber limit this improvement in effective SNR, resulting in the nonlinear Shannon capacity limit. This objective capacity limit, combined with rapidly growing traffic demand, has created a "capacity crisis" for single-mode optical fiber.

[0003] Against this backdrop, space-division multiplexing (SDM) technology emerged. Its goal is to utilize specialized optical fibers, such as multi-core fiber and few-mode fiber, to enable parallel transmission of multiple channels within a single fiber, thereby exponentially increasing communication capacity. Among the various fiber carriers for SDM, multi-core fiber, with its high isolation between core channels and sophisticated fan-in and fan-out mechanisms, is the easiest option for compatible upgrades from existing single-mode fiber communication systems. While multi-core fiber exhibits inter-core delay variations due to inconsistent propagation constants between cores, its hallmark is its high degree of delay stability. Compared to the typical nanosecond-level delay variations between independent single-mode fibers, the picosecond-level delay variations between cores of multi-core fiber demonstrate its superior stability. This makes multi-core fiber naturally suitable for links requiring synchronous signal transmission. Using different cores of a multi-core fiber to transmit the same signal makes it relatively easy to align the delay and phase of the different signals. Diversity reception and combining of these multiple, synchronously transmitted signals at the receiving end significantly improves the signal-to-noise ratio. However, how to compensate for the delay difference between fiber cores in real time and how to complete the diversity reception and coherent combination of multi-path signals with high quality are currently technical challenges.

[0004] In view of this, it is urgent to propose a synchronous combined transmission method that can compensate for the delay difference between each fiber core in real time and adaptively to achieve a stable high signal-to-noise ratio signal transmission effect. Summary of the Invention

[0005] The present invention proposes a synchronous combining transmission method and device based on multi-core optical fiber, which can compensate for the delay difference between each fiber core in real time and adaptively. After delay compensation, multi-channel synchronous signals can be diversity received and coherently combined to stably improve the signal-to-noise ratio of their signals, achieving a stable high signal-to-noise ratio transmission effect that is difficult to achieve with traditional signal transmission.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a synchronous combined transmission method based on a multi-core optical fiber, comprising the following steps: S10. Emitting N laser beams modulated with a communication signal and a reference signal; S11. N laser beams are injected into the N cores of an N-core optical fiber, and are transmitted through the N-core optical fiber and then output. S12. For each laser beam output, the communication signal and the reference signal are decoupled, and the reference signal corresponding to one laser beam is used as a reference signal for calibration; S13. Mixing and phase-detecting the reference signals corresponding to the other laser beams with the reference signal to obtain error signals proportional to the delay drift between the other fiber cores and the reference core; compensating for the delay differences corresponding to the other fiber cores based on the error signals to align the phases of the communication signals output by each fiber core; S14. Coherently combine the phase-aligned communication signals.

[0007] As a possible implementation method, S13 uses a cascaded motor-driven optical delay line and a piezoelectric ceramic-driven optical delay line to compensate for the delay differences corresponding to other fiber cores.

[0008] As a possible implementation, the delay compensation is less than or equal to 10 ns; the accuracy of the delay compensation is less than 100 fs; and the response speed of the delay compensation is greater than or equal to 100 Hz.

[0009] As a possible implementation method, S11 specifically includes: N laser beams are respectively injected into N cores of an N-core optical fiber through a fan-in; after being transmitted through the N cores, they are simultaneously output through a fan-out.

[0010] In a second aspect, the present invention provides a synchronous merging transmission device based on a multi-core optical fiber, comprising: A transmitting end, configured to transmit N laser beams modulated with both a communication signal and a reference signal; N-core optical fiber, N laser beams are injected into the N cores of the N-core optical fiber respectively, and are output after being transmitted through the N-core optical fiber; At the receiving end, for each laser beam output, the communication signal and the reference signal are decoupled; the reference signal corresponding to one of the laser beams is used as the benchmark reference signal; The delay compensation structure mixes and phase-detects the reference signals corresponding to the other laser beams with the reference signal to obtain error signals proportional to the delay difference drift between the other fiber cores and the reference fiber core; the delay differences corresponding to the other fiber cores are compensated based on the error signals to align the phases of the communication signals output by each fiber core; The receiving end is also used to coherently synthesize the communication signals after phase alignment.

[0011] As a possible implementation, the delay compensation structure includes: N-1 mixers, each mixer receiving a reference signal and a reference signal, and mixing the reference signal and the reference signal to obtain a mixed signal; N-1 phase-locked processing modules, one corresponding to a mixer. Each phase-locked processing module receives a mixed signal and filters and performs phase detection on it to obtain an error feedback signal proportional to the delay difference drift between the corresponding fiber core and the reference fiber core; N-1 delay adjusters, one delay adjuster corresponds to a phase-locked processing module and a wavelength division multiplexer at the receiving end, one delay adjuster receives an error feedback signal output by a phase-locked processing module, and compensates for the delay difference of the corresponding fiber core based on the error feedback signal; N-1 delay adjusters align the phases of the communication signals output by each fiber core.

[0012] In a third aspect, the present invention provides a synchronous combined transmission method based on a multi-core optical fiber, comprising the following steps: S20 emits N laser beams modulated with a communication signal; S21. N laser beams are injected into the N cores of an N-core optical fiber, and are transmitted through the N-core optical fiber and then output. S23. One of the laser beams output is used as the calibration optical signal, and the other laser beams are the optical signals to be calibrated. Delay compensation is performed on each optical signal to be calibrated using a cascaded optical delay line and an adjustable optical delay line to align the phases of the communication signals output from each fiber core. S24. Coherently combine phase-aligned communication signals.

[0013] As a possible implementation, before applying the cascaded optical delay line and the adjustable optical delay line for delay compensation, the synchronous combined transmission method further includes: The length of the optical delay line corresponding to each optical signal to be calibrated is calibrated so that the optical signal outputted from each fiber core is within the delay compensation range of the corresponding adjustable optical delay line after delay compensation by the optical delay line.

[0014] In a fourth aspect, the present invention provides a synchronous merging transmission device based on a multi-core optical fiber, comprising: The transmitting end transmits N laser beams modulated with communication signals; N-core optical fiber, N laser beams are injected into the N cores of the N-core optical fiber respectively, and are output after being transmitted through the N-core optical fiber; A delay compensation structure includes N optical delay lines and N-1 adjustable optical delay lines; one optical delay line serves as a reference optical delay line, and the N-1 optical delay lines serve as optical delay lines to be calibrated; each optical delay line to be calibrated is cascaded with an adjustable optical delay line; the optical signal to be calibrated is delay-compensated via the cascaded optical delay lines to be calibrated and the adjustable optical delay lines, so that the phases of communication signals output by each fiber core are aligned; And the receiving end includes N detectors, which detect the phase-aligned optical signals and output communication signals. The N communication signals are input to the signal synthesizer to achieve coherent synthesis of the phase-aligned communication signals.

[0015] As a possible implementation, the delay adjustment range of the optical delay line is greater than 10 ns, the delay adjustment range of the adjustable optical delay line is less than or equal to 10 ns, and the adjustable optical delay line has an adjustment accuracy less than or equal to 100 fs.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The synchronous merging transmission method and device based on multi-core optical fiber proposed in the present invention merges optical signals of different wavelengths (colors) into the same optical fiber for transmission, and then separates these signals at the receiving end. In this way, the transmission capacity of the optical fiber is significantly improved, and the parallel transmission of multiple signals is realized. The synchronous merging transmission and device based on multi-core optical fiber proposed in the present invention utilizes the stability of the delay difference between the cores of the multi-core optical fiber and the cascade delay compensation structure to achieve large-scale compensation, high-precision compensation, and fast-response compensation for the delay difference between the cores of the multi-core optical fiber, effectively solving the problem of limited signal-to-noise ratio of the optical fiber transmission system. The synchronous merging transmission method and device based on multi-core optical fiber proposed in the present invention complete the coherent combination of each fiber core channel on the basis of high-precision synchronous transmission, which can greatly improve the signal-to-noise ratio of the final received signal, and obtain the excellent effect that the signal-to-noise ratio increases linearly with the number of combined fiber core channels. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings: Figure 1 This is a flow chart of the synchronous merging and transmission method based on multi-core optical fiber provided in the first aspect of the embodiments of the present invention.

[0017] Figure 2 This is a schematic structural diagram of a synchronous merging and transmission device based on multi-core optical fibers provided in the second aspect of an embodiment of the present invention.

[0018] Figure 3 This is a flow chart of a synchronous merging transmission method based on multi-core optical fiber provided in the third aspect of an embodiment of the present invention.

[0019] Figure 4 This is a schematic structural diagram of a synchronous merging transmission device based on multi-core optical fibers provided in the fourth aspect of an embodiment of the present invention.

[0020] Figure 5 This is the combined signal eye diagram of the synchronous combined transmission device based on multi-core optical fiber in an embodiment of the present invention Q 2 Factor results plot.

[0021] Figure 6 This is an eye diagram of a combined signal of a synchronous combined transmission device based on a multi-core optical fiber in an embodiment of the present invention.

[0022] Reference numerals 1-first transmitting end, 10-laser, 11-modulator, 12-communication signal source, 13-reference signal source, 14-wavelength division multiplexer, 15-beam splitter; 2-first N-core optical fiber, 20-fan-in, 21-fiber core, 22-fan-out; 3-first receiving end, 30-wavelength division multiplexer, 31-communication signal detector, 32-reference signal detector, 33-signal coupler, 34-signal receiver; 4-first delay compensation structure, 40-mixer, 41-phase-locked processing module, 42-delay adjuster; 5-second transmitting end, 50-dispersion compensating optical fiber, 51-erbium-doped fiber amplifier, 52-variable optical attenuator; 6- second N-core optical fiber; 7-second delay compensation structure, 70-optical delay line, 71-adjustable optical delay line; 8-second receiving end, 80-signal synthesizer, 81-eye diagrammer; 9-noise injection unit, 90-bandpass filter, 91-optical power meter. DETAILED DESCRIPTION

[0023] To facilitate a clear description of the technical solutions of the embodiments of the present invention, the words "first" and "second" are used in the embodiments of the present invention to distinguish between identical or similar items with substantially the same functions and effects. For example, the first threshold and the second threshold are merely used to distinguish between different thresholds and do not limit their order. Those skilled in the art will understand that the words "first" and "second" do not limit the quantity or execution order, and the words "first" and "second" do not necessarily mean different.

[0024] It should be noted that, in the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the present invention should not be construed as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0025] In the present invention, "at least one" means one or more, and "more" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: the existence of A alone, the existence of A and B at the same time, and the existence of B alone, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. The following at least one item (item) or similar expressions refers to any combination of these items, including any combination of single items (items) or plural items (items). For example, at least one item (item) of a, b or c can mean: a, b, c, the combination of a and b, the combination of a and c, the combination of b and c, or the combination of a, b and c, where a, b, c can be single or plural.

[0026] The embodiments of the present invention aim to provide a synchronous merging transmission method and device based on multi-core optical fiber.

[0027] In the first aspect, the embodiment of the present invention provides a synchronous combined transmission method based on multi-core optical fiber, see Figure 1 , including the following steps: S10. Emitting N laser beams modulated with a communication signal and a reference signal; As an example, a communication signal source and a reference signal source are configured, two lasers are used to emit optical carriers of different wavelengths, and two modulators are used to modulate the communication signal emitted by the communication signal source and the reference signal emitted by the reference signal source onto optical carriers of different wavelengths, respectively. After coupling and splitting, they become N beams of laser light that simultaneously contain modulated communication signals and reference signals.

[0028] S11. N laser beams are injected into the N cores of an N-core optical fiber, and are transmitted through the N-core optical fiber and then output. As a possible implementation method, S11 specifically includes: N laser beams are injected into the N cores of the N-core optical fiber in sequence through the fan-in device; after being transmitted through the N cores, they are output simultaneously through the fan-out device.

[0029] S12. For each laser beam output, the communication signal and the reference signal are decoupled, and the reference signal corresponding to one laser beam is used as a reference signal for calibration; As an example, a communication signal detector and a reference signal detector are used to decouple the communication signal and the reference signal. After decoupling the communication signal and the reference signal, the reference signal corresponding to one of the laser beams is used as a reference signal for alignment.

[0030] S13. Mixing and phase-detecting the reference signals corresponding to the other laser beams with the reference signal to obtain error signals proportional to the delay drift between the other fiber cores and the reference core; compensating for the delay differences corresponding to the other fiber cores based on the error signals to align the phases of the communication signals output by each fiber core; As a possible implementation method, S13 uses a cascaded motor-driven optical delay line and a piezoelectric ceramic-driven optical delay line to compensate for the delay differences corresponding to other fiber cores.

[0031] As a possible implementation, the delay compensation is less than or equal to 10 ns; the accuracy of the delay compensation is less than 100 fs; and the response speed of the delay compensation is greater than or equal to 100 Hz.

[0032] This embodiment can achieve large-scale, high-precision, and fast-response compensation for inter-core delay differences in multi-core optical fibers, effectively solving the problem of limited signal-to-noise ratio in optical fiber transmission systems.

[0033] S14. Coherently combine the phase-aligned communication signals.

[0034] As an example, an electrical coupler is used to perform coherent synthesis on the phase-aligned communication signals, so that the phase-aligned communication signals of each channel are directly added.

[0035] In an ideal case, the signal-to-noise ratio of the combined signal is the sum of the signal-to-noise ratios of the signals in each branch.

[0036] In a second aspect, an embodiment of the present invention provides a synchronous merging transmission device based on a multi-core optical fiber, see Figure 2 , comprising: a first transmitting end 1, a first N-core optical fiber 2, a first receiving end 3 and a first delay compensation structure 4; The first transmitting end 1 is used to transmit N laser beams modulated with a communication signal and a reference signal; See also Figure 2 As an example, the first transmitting end 1 includes two lasers 10, two modulators 11, a communication signal source 12, a reference signal source 13, a wavelength division multiplexer 14, and a beam splitter 15. The two lasers 10 are used to transmit optical carriers of different wavelengths. The two modulators 11 are used to modulate the communication signal emitted by the communication signal source 12 and the reference signal emitted by the reference signal source 13 onto optical carriers of different wavelengths. The two modulators 11 are then coupled by the wavelength division multiplexer 14 and split by the beam splitter 15 into N laser beams modulated with both the communication signal and the reference signal, and then emitted.

[0037] N laser beams are respectively injected into the N cores of the first N-core optical fiber 2 and output after being transmitted through the first N-core optical fiber 2; See also Figure 2 As an example, the first N-core optical fiber 2 includes a fan-in 20, N fiber cores 21 and a fan-out 22. N beams of laser light are respectively injected into the N fiber cores of the first N-core optical fiber through the fan-in 20; after being transmitted through the N fiber cores, they are output simultaneously through the fan-out 22.

[0038] The first receiving end 3 receives the laser output from the first N-core optical fiber 2, and decouples the communication signal and the reference signal for each laser beam output; and uses the reference signal corresponding to one of the laser beams as a benchmark reference signal; See also Figure 2 As an example, the first receiving end 3 includes N wavelength division multiplexers 30, N communication signal detectors 31, N reference signal detectors 32, a signal coupler 33, and a signal receiver 34. Each wavelength division multiplexer 30 is connected to a communication signal detector 31 and a reference signal detector 32 to decouple the communication signal from the reference signal. After decoupling the communication signal and the reference signal, the reference signal corresponding to one of the laser beams is used as a calibration reference signal.

[0039] The first delay compensation structure 4 mixes and phase-detects the reference signals corresponding to the other laser beams with the reference signal to obtain error signals proportional to the delay difference drift between the other fiber cores and the reference fiber core; and compensates the delay differences corresponding to the other fiber cores based on the error signals to align the phases of the communication signals output by the various fiber cores. See also Figure 2 As a possible implementation, the first delay compensation structure 4 includes: N-1 mixers 40, each mixer 40 receives a reference signal and a reference signal, and mixes the reference signal and the reference signal to obtain a mixed signal; N-1 phase-locked processing modules 41, one phase-locked processing module 41 corresponds to one mixer 40, and one phase-locked processing module 41 receives a mixed signal and performs filtering and phase detection on it to obtain an error feedback signal proportional to the delay difference drift between the corresponding fiber core and the reference fiber core; N-1 delay adjusters 42, one delay adjuster 42 corresponds to a phase-locked processing module 41 and a wavelength division multiplexer 30 at the receiving end 3, one delay adjuster 42 receives an error feedback signal output by a phase-locked processing module 41, and performs delay compensation on the delay difference of the corresponding fiber core according to the error feedback signal; the N-1 delay adjusters 42 align the phases of the communication signals output by each fiber core.

[0040] The first receiving end 3 is further used for coherently combining the communication signals after phase alignment.

[0041] In a third aspect, an embodiment of the present invention provides a synchronous combined transmission method based on a multi-core optical fiber, see Figure 3 , including the following steps: S20 emits N laser beams modulated with a communication signal; As an example, a laser is used to transmit an optical carrier, a communication signal source is configured, and a modulator is used to modulate the communication signal emitted by the communication signal source onto the optical carrier generated by the laser to obtain a 10Gbps OOK signal. The signal is then dispersion pre-compensated. The optical power of the dispersion-compensated signal is then adjusted jointly by an erbium-doped fiber amplifier and an adjustable optical attenuator. After beam splitting, N beams of laser light modulated with the communication signal are generated.

[0042] S21. N laser beams are injected into the N cores of an N-core optical fiber, and are transmitted through the N-core optical fiber and then output. As an example, the N-core optical fiber is a 41 km seven-core optical fiber.

[0043] S23. One of the laser beams output is used as the calibration optical signal, and the other laser beams are the optical signals to be calibrated. Delay compensation is performed on each optical signal to be calibrated using a cascaded optical delay line and an adjustable optical delay line to align the phases of the communication signals output from each fiber core. S24. Coherently combine phase-aligned communication signals.

[0044] As a possible implementation, before applying the cascaded optical delay line and the adjustable optical delay line for delay compensation, the synchronous combined transmission method further includes: The length of the optical delay line corresponding to each optical signal to be calibrated is calibrated so that the optical signal outputted from each fiber core is within the delay compensation range of the corresponding adjustable optical delay line after delay compensation by the optical delay line.

[0045] In a fourth aspect, an embodiment of the present invention provides a synchronous merging transmission device based on a multi-core optical fiber, see Figure 4 , comprising: a second transmitting end 5, a second N-core optical fiber 6, a second delay compensation structure 7 and a second receiving end 8; The second transmitting end 5 is used to transmit N laser beams modulated with communication signals; See also Figure 4As an example, the second transmitting end 5 includes a laser 10, a modulator 11, a communication signal source 12, a dispersion-compensating fiber 50, an erbium-doped fiber amplifier 51, an adjustable optical attenuator 52, and a beam splitter 15. The laser 10 is used to transmit an optical carrier, and the modulator 11 is used to modulate the communication signal emitted by the communication signal source 12 onto the optical carrier emitted by the laser. The dispersion-compensating fiber 50 is used to pre-compensate the dispersion of the communication signal. The erbium-doped fiber amplifier 51 and the adjustable optical attenuator 52 are used to jointly adjust the optical power of the dispersion-compensated signal. The beam splitter 15 is used to split the signal after the optical power is adjusted to obtain N beams of laser light modulated with the communication signal.

[0046] N laser beams are respectively injected into the N cores of the second N-core optical fiber 6 and output after being transmitted through the N-core optical fiber; The following is a detailed explanation of this solution using seven-core optical fiber as an example.

[0047] See also Figure 4 As an example, the second N-core optical fiber 6 includes a fan-in 20, seven fiber cores 21 and a fan-out 22. Seven laser beams are respectively injected into the seven fiber cores of the second N-core optical fiber through the fan-in 20; after being transmitted through the seven fiber cores, they are output simultaneously through the fan-out 22.

[0048] The second delay compensation structure 7 includes N optical delay lines 70 and N-1 adjustable optical delay lines 71; wherein, one optical delay line 70 serves as a reference optical delay line, and N-1 optical delay lines 70 serve as optical delay lines to be calibrated; each optical delay line to be calibrated is cascaded with an adjustable optical delay line; the optical signal to be calibrated is delay-compensated via the cascaded optical delay lines to be calibrated and the adjustable optical delay lines, so that the phases of the communication signals output by each fiber core are aligned; See also Figure 4 As an example, the second delay compensation structure 7 includes seven optical delay lines and six adjustable optical delay lines; specifically, a motor-driven optical delay line and a piezoelectric ceramic-driven optical delay line are cascaded to achieve large-scale, high-precision, and fast-response delay compensation.

[0049] In specific implementation, the lengths of the N optical delay lines are different to roughly compensate for the inter-core delay difference of the seven-core optical fiber; the lengths of the N optical delay lines are pre-configured so that the difference between the optical delay lines is within a certain range, and then the adjustable optical delay line is used for precise compensation.

[0050] The second receiving end 8 includes N communication signal detectors 31, which detect the phase-aligned optical signals and output communication signals. The N communication signals are input to the signal synthesizer 80 to achieve coherent synthesis of the phase-aligned communication signals.

[0051] See also Figure 4To demonstrate the signal combining gain, a noise injection unit 9 is added to the synchronous combining transmission device. The noise injection unit 9 includes an erbium-doped fiber amplifier 51, a bandpass filter 90, an adjustable optical attenuator 52, a signal coupler 33, a beam splitter 15, and an optical power meter 91. The erbium-doped fiber amplifier 51 in the noise injection unit 9 generates broadband spontaneous emission noise, which is filtered by the bandpass filter 90. The noise power is then adjusted by the adjustable optical attenuator 52, and finally, after passing through the signal coupler 33 and the beam splitter 15, it enters the corresponding output channels of the second N-core optical fiber 6. The optical power meter 91 is used to monitor the injected noise power. The noise entering each output channel is decohered by the second delay compensation structure 7 and can therefore be regarded as Gaussian white noise.

[0052] As a possible implementation, the delay adjustment range of the optical delay line is greater than 10ns, the delay adjustment range of the adjustable optical delay line is less than or equal to 10ns, and the adjustable optical delay line has an adjustment accuracy of less than or equal to 100fs. In this case, the magnitude of the inter-core delay difference drift is much smaller than the signal symbol period, so there is no need to connect a phase-locked processing module.

[0053] See also Figure 4 , use eye diagram meter 81 to measure eye diagram Q 2 The signal-to-noise ratio is measured by the factor, and the adjustable optical delay line is adjusted based on the measurement result to accurately compensate for the delay of each branch signal and achieve alignment of each branch signal.

[0054] Figure 5 The eye diagram of the received signal when receiving a single fiber core channel and receiving a combined 2 / 4 / 6 fiber core channel. Q 2 The result of the curve of the factor changing with the injected noise power. The results show that when the number of combined channels doubles, the received signal eye diagram Q 2 The factor can be increased by about 3dB, indicating that the received signal-to-noise ratio is doubled, which is in line with the expected effect. Figure 6 The following are the eye diagrams of the received signal under the conditions of single-fiber core channel reception and 2 / 4 / 6-fiber core channel combined reception. It can be clearly seen that as the number of combined channels increases, the signal eye diagram becomes thinner and the signal-to-noise ratio improves.

[0055] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other variations of the disclosed embodiments by reviewing the drawings, the disclosure, and the accompanying drawings. In the specification, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple situations. A single processor or other unit can implement several functions listed in the specification. Certain measures are recorded in different embodiments, but this does not mean that these measures cannot be combined to produce good results.

[0056] Although the present invention has been described with reference to specific features and embodiments thereof, it will be apparent that various modifications and combinations thereof may be made without departing from the spirit and scope of the invention. Accordingly, this specification and drawings are merely illustrative of the present invention and are deemed to cover any and all modifications, variations, combinations or equivalents within the scope of the invention. It will be apparent that various modifications and variations of the present invention may be made by those skilled in the art without departing from the spirit and scope of the invention. Thus, the present invention is intended to include such modifications and variations as fall within the scope of the invention and its equivalents.

Claims

1. A synchronous combined transmission method based on multi-core optical fiber, characterized in that: The steps include: S10. Emitting N laser beams modulated with a communication signal and a reference signal; S11. N laser beams are injected into the N cores of an N-core optical fiber, and are transmitted through the N-core optical fiber and then output. S12. For each laser beam output, the communication signal and the reference signal are decoupled, and the reference signal corresponding to one laser beam is used as a reference signal for calibration; S13. Mixing and phase-detecting the reference signals corresponding to the other laser beams with the reference signal to obtain error signals proportional to the delay drift between the other fiber cores and the reference core; compensating for the delay differences corresponding to the other fiber cores based on the error signals to align the phases of the communication signals output by each fiber core; S14. Coherently combine the phase-aligned communication signals.

2. The synchronous merging transmission method based on multi-core optical fiber according to claim 1, characterized in that: S13 uses a cascaded motor-driven optical delay line and a piezoelectric ceramic-driven optical delay line to compensate for the delay differences corresponding to other fiber cores.

3. The synchronous merging transmission method based on multi-core optical fiber according to claim 1, characterized in that: The delay compensation is less than or equal to 10ns; the accuracy of the delay compensation is less than 100fs; the response speed of the delay compensation is greater than or equal to 100Hz.

4. The synchronous combined transmission method based on multi-core optical fiber according to claim 1, characterized in that: S11 specifically includes: N laser beams are respectively injected into N cores of the N-core optical fiber through the fan-in device; after being transmitted through the N cores, they are simultaneously output through the fan-out device.

5. A synchronous merging transmission device based on multi-core optical fiber, characterized in that: include: A transmitting end, configured to transmit N laser beams modulated with both a communication signal and a reference signal; N-core optical fiber, N laser beams are injected into the N cores of the N-core optical fiber respectively, and are output after being transmitted through the N-core optical fiber; At the receiving end, for each laser beam output, the communication signal and the reference signal are decoupled; the reference signal corresponding to one of the laser beams is used as the benchmark reference signal; The delay compensation structure mixes and phase-detects the reference signals corresponding to the other laser beams with the reference signal to obtain error signals proportional to the delay difference drift between the other fiber cores and the reference fiber core; the delay differences corresponding to the other fiber cores are compensated based on the error signals to align the phases of the communication signals output by each fiber core; The receiving end is also used to coherently synthesize the communication signals after phase alignment.

6. The synchronous merging transmission device based on multi-core optical fiber according to claim 5, characterized in that: The delay compensation structure includes: N-1 mixers, each mixer receiving a reference signal and a reference signal, and mixing the reference signal and the reference signal to obtain a mixed signal; N-1 phase-locked processing modules, one corresponding to a mixer. Each phase-locked processing module receives a mixed signal and filters and performs phase detection on it to obtain an error feedback signal proportional to the delay difference drift between the corresponding fiber core and the reference fiber core; N-1 delay adjusters, one delay adjuster corresponds to a phase-locked processing module and a wavelength division multiplexer at the receiving end, one delay adjuster receives an error feedback signal output by a phase-locked processing module, and compensates for the delay difference of the corresponding fiber core based on the error feedback signal; N-1 delay adjusters align the phases of the communication signals output by each fiber core.

7. A synchronous combined transmission method based on multi-core optical fiber, characterized in that: The steps include: S20 emits N laser beams modulated with a communication signal; S21. N laser beams are injected into the N cores of an N-core optical fiber, and are transmitted through the N-core optical fiber and then output. S23. One of the laser beams output is used as the calibration optical signal, and the other laser beams are the optical signals to be calibrated. Delay compensation is performed on each optical signal to be calibrated using a cascaded optical delay line and an adjustable optical delay line to align the phases of the communication signals output from each fiber core. S24. Coherently combine phase-aligned communication signals.

8. The synchronous combined transmission method based on multi-core optical fiber according to claim 7, characterized in that: Before applying the cascaded optical delay line and the adjustable optical delay line for delay compensation, the synchronous combined transmission method further includes: The length of the optical delay line corresponding to each optical signal to be calibrated is calibrated so that the optical signal outputted from each fiber core is within the delay compensation range of the corresponding adjustable optical delay line after delay compensation by the optical delay line.

9. A synchronous merging transmission device based on multi-core optical fiber, characterized in that: include: The transmitting end transmits N laser beams modulated with communication signals; N-core optical fiber, N laser beams are injected into the N cores of the N-core optical fiber respectively, and are output after being transmitted through the N-core optical fiber; A delay compensation structure includes N optical delay lines and N-1 adjustable optical delay lines; one optical delay line serves as a reference optical delay line, and the N-1 optical delay lines serve as optical delay lines to be calibrated; each optical delay line to be calibrated is cascaded with an adjustable optical delay line; the optical signal to be calibrated is delay-compensated via the cascaded optical delay lines to be calibrated and the adjustable optical delay lines, so that the phases of communication signals output by each fiber core are aligned; And the receiving end includes N detectors, which detect the phase-aligned optical signals and output communication signals. The N communication signals are input to the signal synthesizer to achieve coherent synthesis of the phase-aligned communication signals.

10. The synchronous merging transmission device based on multi-core optical fiber according to claim 9, characterized in that: The delay adjustment range of the optical delay line is greater than 10ns, the delay adjustment range of the adjustable optical delay line is less than or equal to 10ns, and the adjustable optical delay line has an adjustment accuracy less than or equal to 100fs.

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