A transmission architecture based on dual-core optical fiber and dual-channel free-space optical communication

Abstract

The application relates to the technical field of free space optical communication and optical fiber transmission, and provides a transmission architecture based on a double-core optical fiber and double-channel free space optical communication, which comprises a sending terminal system, a double-core optical fiber transmission section, a double-channel FSO space section and a receiving terminal system. Two optical signals are generated at the sending terminal, coupled into two fiber cores of the double-core optical fiber through a fan-in device and transmitted in parallel, separated through a fan-out device and formed into two free space optical channels through two sets of FSO transmitting optical units respectively; two signals are received by two sets of FSO receiving optical units at the receiving terminal, respectively transmitted into two DSPs through the receiving side fan-in / fan-out and the double-core optical fiber, and based on a link quality index, channel selection backup output and / or maximum ratio combination output are executed. The application realizes parallel transmission of two parallel optical signals carried by the double-core optical fiber in the double-channel FSO space link, and improves the link stability and communication sensitivity of the receiving terminal.

Description

Technical Field

[0001] This invention relates to the field of free-space optical communication and fiber optic transmission integration technology, and more specifically, to a transmission architecture based on dual-core optical fiber and dual-channel free-space optical communication. Background Technology

[0002] Free-space optical communication (FSO) has broad application prospects in scenarios such as high-speed metropolitan area interconnection, emergency communication, UAV / airborne communication, and temporary link construction due to its advantages such as high bandwidth, high speed, strong resistance to electromagnetic interference, and no need for spectrum licensing. However, traditional FSO communication systems mostly use single-channel links, which are susceptible to factors such as atmospheric turbulence, rain and fog attenuation, thermal disturbance, building obstruction, and pointing jitter, resulting in instantaneous link fading, received power fluctuations, increased bit error rate, and even communication interruption, exhibiting transmission instability problems.

[0003] For single-channel FSO systems, when link quality deteriorates, improvements are typically only possible by increasing transmit power, increasing receiver aperture, or optimizing tracking alignment. However, these methods are often limited by device capabilities, system size and power consumption, and deployment conditions, and cannot fundamentally solve the reliability bottleneck of "single link without redundancy." On the other hand, if the receiver only has one signal, it is difficult to obtain combining gain through spatial diversity, thus limiting the improvement of communication sensitivity and anti-fading capability.

[0004] Therefore, a transmission architecture is needed that can provide dual-channel redundancy backup at the physical layer and support dual-channel signal merging at the receiver to improve sensitivity, so as to improve the link stability and reliability of FSO communication in complex environments. Summary of the Invention

[0005] In view of this, the present invention proposes a transmission architecture based on dual-core optical fiber and dual-channel free space optical communication. The link backup is achieved through dual-channel parallel transmission, and channel selection and / or maximum ratio combining (MRC) are performed on the two signals at the receiving end, thereby improving the reliability and receiving sensitivity of FSO communication.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A transmission architecture based on dual-core optical fiber and dual-channel free-space optical communication is characterized by comprising a transmitting terminal system, a dual-core optical fiber transmission segment, a dual-channel FSO space segment, and a receiving terminal system. The transmitting terminal system is used to generate two optical signals and couple the two optical signals into the two cores of the dual-core optical fiber for parallel transmission via a fan-in connector. The dual-core fiber transmission segment is used to carry two parallel optical signals. The dual-channel FSO space segment is used to transmit two optical signals through two sets of FSO transmitting optical units to form two free space optical channels, which are then received by two sets of FSO receiving optical units respectively. The receiving terminal system is used to perform digital signal processing on the two received signals respectively, and to perform channel selection output and / or maximum ratio combining output according to the link quality index.

[0007] Furthermore, the two optical signals are two replica signals of the same service data, used to achieve spatial diversity and redundancy backup.

[0008] Furthermore, the transmitting terminal system includes: The signal transmission module is used to generate two optical signals to be transmitted; Single-mode fiber is used to extract two optical signals separately. A transmit-side fan-in converter is used to couple two single-mode fiber signals to two independent cores of a dual-core fiber, respectively. Dual-core optical fiber is used to enable parallel transmission of two optical signals; The transmit-side fan-out is used to fan out the two signals into two single-mode fiber optic signals respectively; It also includes two sets of free-space optical emission units, which enable the two optical signals to be transmitted to the receiving end via two spatially parallel FSO channels.

[0009] Furthermore, the dual-channel FSO spatial segment includes two sets of transmitting optical units and two sets of receiving optical units, forming a first FSO channel and a second FSO channel respectively; the two spatial channels are spatially separated in terms of emission aperture, emission direction or physical position, so as to reduce the probability that atmospheric disturbances in the same area at the same time will cause deep fading to both channels simultaneously.

[0010] Furthermore, the receiving terminal system includes: Two sets of free-space optical receiving optical units are used to receive optical signals from two FSO channels respectively, and couple them to two single-mode optical fibers respectively; The receiver-side fan-in converter is used to couple two single-mode fiber signals into the two cores of the receiver-side dual-core fiber for parallel transmission. The receiving side uses a dual-core optical fiber to carry two parallel optical signals; The receiver-side fanout is used to output two single-mode fiber optic signals. Two digital signal processing modules are used to recover and evaluate the signals of their respective channels, and output the data signals and corresponding link quality indicators of each channel. And a channel selection and / or maximum ratio merging module, used to perform channel selection output and / or maximum ratio merging output based on the link quality index.

[0011] Furthermore, the operation mode of the channel selection and / or maximum ratio merging module includes: (a) Channel selection: When the link quality index of one of the channels is detected to be lower than the preset threshold or a loss of lock occurs, the output is switched to another channel; (b) Maximum ratio combining: The two signals are weighted and combined based on the link quality indicators of the two channels to obtain a higher equivalent signal-to-noise ratio and receiving sensitivity.

[0012] Furthermore, the channel selection and / or maximum ratio merging module is configured to: perform maximum ratio merging to improve sensitivity when both channels are available; and degrade to single-channel output or channel selection output when the quality index of either channel is continuously below the threshold or loses lock.

[0013] This invention further proposes a transmission method based on dual-core optical fiber and dual-channel free-space optical communication, comprising the following steps: Generates two optical signals; The two optical signals are fanned into the two cores of the dual-core optical fiber for parallel transmission, and then fanned out to form two output optical signals. The two output optical signals are sent through the first free space optical channel and the second free space optical channel, respectively. Two optical signals from the first free space optical channel and the second free space optical channel are received respectively, and the two optical signals are fanned into the two cores of the dual-core optical fiber for parallel transmission and then fanned out to form two received optical signals. Digital signal processing is performed on the two received optical signals to obtain link quality indicators; And based on the link quality indicators, perform channel selection output and / or maximum ratio merging output.

[0014] Furthermore, the maximum ratio merging includes: determining weighting coefficients based on the link quality indicators of the two channels, weighting the two signals, and merging them for output.

[0015] Furthermore, when the link quality index of any channel is detected to be lower than a preset threshold or a loss of lock occurs, the output is switched to another channel.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention first provides physical layer redundancy through dual-channel parallel transmission, allowing communication to be maintained by the other link when the quality of one link deteriorates or is interrupted. Second, the receiver can perform maximum ratio combining (MRC) on the two signals, improving the equivalent signal-to-noise ratio and communication sensitivity when both are available. This simultaneously takes into account both "reliability priority (channel backup switching)" and "sensitivity priority (MRC combining gain)," enhancing the system's robustness to atmospheric disturbances and transient fading. Finally, the invention utilizes dual-core optical fiber to achieve a compact dual-path carrying and transmission structure, facilitating engineering deployment and integration. Attached Figure Description

[0017] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. In the drawings: Figure 1 This is a schematic diagram of the transmission architecture of the present invention based on dual-core optical fiber and dual-channel free-space optical communication; reference numerals: 1—transmit signal module; 2—single-mode optical fiber; 3—transmit-side fan-in; 4—DCF dual-core optical fiber; 5—transmit-side fan-out; 6—first FSO transmitting optical unit; 7—second FSO transmitting optical unit; 8—first FSO channel; 9—second FSO channel; 10—first FSO receiving optical unit; 11—second FSO receiving optical unit; 12—receive-side fan-in; 13—receive-side dual-core optical fiber; 14—receive-side fan-out; 15—first DSP module; 16—second DSP module; 17—channel selection and / or maximum ratio merging module; 18—output data interface. Detailed Implementation

[0018] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] This embodiment provides a transmission architecture based on dual-core optical fiber and dual-channel free-space optical communication (FSO). It is used to improve link reliability and receiver sensitivity in situations where single-channel transmission is unstable due to turbulence, rain, fog, obstruction, or pointing disturbances in the free-space optical link. This is achieved through dual-channel backup and maximum ratio combining (MRC). The system structure includes a transmitting terminal system, a dual-core optical fiber transmission section, a dual-channel FSO space section, and a receiving terminal system; wherein: (1) The transmitting terminal system is used to generate two optical signals and couple the two optical signals into the two cores of the dual-core optical fiber for parallel transmission through the fan-in connector; (2) The dual-core fiber transmission segment is used to carry two parallel optical signals in the fiber segment; (3) The dual-channel FSO space segment is used to transmit two optical signals through two sets of FSO transmitting optical units to form two free space optical channels, which are then received by two sets of FSO receiving optical units respectively; (4) The receiving terminal system is used to perform digital signal processing (DSP) on the two received signals respectively, and to perform channel selection output and / or maximum ratio combining (MRC) output according to the link quality index.

[0020] Transmitter terminal system The transmitting terminal system is used to generate and output two optical signals to be transmitted. The two optical signals generated by the transmitting signal module 1 are led out through single-mode fiber 2 and connected to fan-in connector 3. Fan-in connector 3 is used to couple the two single-mode fiber signals to two independent cores of dual-core fiber 4, thereby realizing the parallel transmission of the two optical signals within the dual-core fiber 4. After transmission through the dual-core fiber 4, the two signals are fanned out by fan-out connector 5 into two single-mode fiber signals, which are then connected to two sets of free-space optical emission optical units 6 and 7, respectively, so that the two optical signals are transmitted to the receiving end through two spatially parallel FSO channels 8 and 9.

[0021] The two optical signals can be two copies of the same service data to achieve spatial diversity and redundancy backup. The modulation format and implementation method of the two optical signals are selected according to the system deployment (e.g., intensity modulation direct detection system or coherent system). However, no matter what modulation method is used, it does not affect the system essence of "dual-core fiber parallel transmission + dual-channel FSO spatial parallel transmission" described in this invention.

[0022] Dual-channel FSO space segment The dual-channel FSO space segment includes two sets of transmitting optical units 6 and 7 and two sets of receiving optical units 10 and 11, forming the first FSO channel (8) and the second FSO channel (9), respectively. The two space channels can form a certain spatial separation in terms of emission aperture, emission direction or physical position, so as to reduce the probability of atmospheric disturbances in the same area at the same time causing deep fading of both channels at the same time, thereby improving reliability.

[0023] In engineering deployment, the transmitting optical unit and the receiving optical unit can adopt an optical horn antenna / telescope transceiver structure to achieve collimation, beam expansion, light collection and coupling of free space beams.

[0024] Receiver terminal system The receiving terminal system is used to receive optical signals from two FSO channels respectively and perform digital signal processing, channel selection, and / or MRC merging output. Two sets of free-space optical receiving optical units 10 and 11 receive the incident optical signals from FSO channels 8 and 9 respectively, and couple them to two single-mode optical fibers respectively. The two single-mode optical fiber signals are connected to the receiving-side fan-in unit 12 and then coupled into the two cores of the receiving-side dual-core optical fiber 13 for parallel transmission. After passing through the receiving-side fan-out unit 14, they are output as two single-mode optical fiber signals, which are then processed by two digital signal processing (DSP) modules 15 and 16 respectively.

[0025] Two DSP modules, 15 and 16, are used to recover and evaluate the signals of their respective channels. The processing flow includes sampling and synchronization, equalization, carrier / phase recovery, and calculation of link quality indicators such as bit error rate or equivalent signal-to-noise ratio, and outputs the data signals and corresponding quality indicators of each channel.

[0026] Channel selection and maximum ratio merging (MRC) Two DSP outputs are input to channel selection and / or maximum ratio merging module 17. This module supports at least one or a combination of the following operating modes: (a) Channel selection (backup): When the link quality index of one of the channels is detected to be lower than the preset threshold or a loss of lock occurs, the output is switched to another channel, thereby maintaining communication continuity when a single channel is fading or interrupted; (b) Maximum Ratio Combining (MRC): Based on the link quality indicators of the two channels, the two signals are weighted and combined to obtain a higher equivalent signal-to-noise ratio and receiver sensitivity.

[0027] In one implementation, the system performs MRC merging to improve sensitivity when both channels are available; when the quality index of either channel remains below the threshold or is lost, it degrades to single-channel output or channel selection output to achieve a balance between reliability and sensitivity. The merged or selected signal is output from the output data interface 18 to subsequent decoding, service processing, or network interface.

[0028] The system modules of this embodiment will be described in detail below: A transmission system based on dual-core optical fiber and dual-channel free-space optical communication includes: The transmitting module is used to generate two optical signals; The transmitter-side fan-in, transmitter-side dual-core optical fiber, and transmitter-side fan-out are configured to couple the two optical signals into the two cores of the transmitter-side dual-core optical fiber for parallel transmission, and the transmitter-side fan-out is configured to fan out the signals from the two cores of the transmitter-side dual-core optical fiber to form two output optical signals. A dual-channel free-space light emission module is used to emit the two output light signals to form a first free-space light channel and a second free-space light channel, respectively. A dual-channel free-space light receiving module is used to receive light signals from the first free-space light channel and the second free-space light channel, respectively. The receiver-side fan-in, receiver-side dual-core optical fiber, and receiver-side fan-out are provided. The receiver-side fan-in is used to couple two received optical signals into the two cores of the receiver-side dual-core optical fiber for parallel transmission. The receiver-side fan-out is used to fan out the signals from the two cores of the receiver-side dual-core optical fiber to form two received optical signals. Two digital signal processing modules are used to perform digital signal processing on the two received optical signals and output link quality indicators respectively. And a channel selection and maximum ratio merging module, used to perform channel selection output and / or maximum ratio merging output on the two signals based on the link quality index.

[0029] In a preferred embodiment, the two optical signals are two replica signals of the same service data, used to achieve redundancy backup and spatial diversity.

[0030] In a preferred embodiment, the fan-in device is used to couple the optical signals of the two single-mode optical fibers into the two independent cores of the dual-core optical fiber, and the fan-out device is used to fan out the signals in the two cores of the dual-core optical fiber into two single-mode optical fiber signals.

[0031] In a preferred embodiment, the dual-channel free-space light emitting module includes two sets of independent emitting optical units, and the dual-channel free-space light receiving module includes two sets of independent receiving optical units, thereby forming a first free-space light channel and a second free-space light channel.

[0032] In a preferred embodiment, the two sets of transmitting optical units and / or the two sets of receiving optical units are spatially separated to reduce the probability of deep fading occurring simultaneously in the two free-space optical channels due to atmospheric disturbances.

[0033] In a preferred embodiment, the two digital signal processing modules output link quality indicators for their respective channels, and the link quality indicators include at least one of signal-to-noise ratio, bit error rate, and error vector amplitude.

[0034] In a preferred embodiment, the channel selection and maximum ratio merging module is configured to switch to another channel when the link quality index of any channel is lower than a preset threshold or when a loss of lock is detected.

[0035] In a preferred embodiment, the channel selection and maximum ratio merging module is configured to: weight the two signals based on the link quality indicators of the two channels and perform maximum ratio merging output.

[0036] Based on the above system structure, this embodiment further proposes a transmission method based on dual-core optical fiber and dual-channel free-space optical communication, the steps of which include: Generates two optical signals; The two optical signals are fanned into the two cores of the dual-core optical fiber for parallel transmission, and then fanned out to form two output optical signals. The two output optical signals are sent through the first free space optical channel and the second free space optical channel, respectively. Two optical signals from the first free space optical channel and the second free space optical channel are received respectively, and the two optical signals are fanned into the two cores of the dual-core optical fiber for parallel transmission and then fanned out to form two received optical signals. Digital signal processing is performed on the two received optical signals to obtain link quality indicators; And based on the link quality indicators, perform channel selection output and / or maximum ratio merging output.

[0037] In a preferred embodiment, after digital signal processing is performed on the two received signals respectively, the link quality index of the two signals is calculated, and channel selection output or maximum ratio merging output is performed based on the link quality index.

[0038] As a preferred embodiment, the maximum ratio merging includes: determining weighting coefficients based on the link quality indicators of the two channels, weighting the two signals, and merging them for output.

[0039] In a preferred embodiment, when the link quality index of any channel is detected to be lower than a preset threshold or a loss of lock occurs, the output is switched to another channel.

[0040] Through the above structure and process, this invention realizes the parallel transmission of two parallel optical signals carried by dual-core optical fibers in a dual-channel FSO space link, and improves link stability and communication sensitivity at the receiving end through channel backup switching and / or MRC merging.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A transmission architecture based on dual-core optical fiber and dual-channel free-space optical communication, characterized in that, This includes a transmitting terminal system, a dual-core fiber optic transmission segment, a dual-channel FSO space segment, and a receiving terminal system; The transmitting terminal system is used to generate two optical signals and couple the two optical signals into the two cores of the dual-core optical fiber for parallel transmission via a fan-in connector. The dual-core fiber transmission segment is used to carry two parallel optical signals. The dual-channel FSO space segment is used to transmit two optical signals through two sets of FSO transmitting optical units to form two free space optical channels, which are then received by two sets of FSO receiving optical units respectively. The receiving terminal system is used to perform digital signal processing on the two received signals respectively, and to perform channel selection output and / or maximum ratio combining output according to the link quality index.

2. The transmission architecture according to claim 1, characterized in that, The two optical signals are two replica signals of the same service data, used to achieve spatial diversity and redundancy backup.

3. The transmission architecture according to claim 1, characterized in that, The transmitting terminal system includes: The signal transmission module is used to generate two optical signals to be transmitted; Single-mode fiber is used to extract two optical signals separately. A transmit-side fan-in converter is used to couple two single-mode fiber signals to two independent cores of a dual-core fiber, respectively. Dual-core optical fiber is used to enable parallel transmission of two optical signals; The transmit-side fan-out is used to fan out the two signals into two single-mode fiber optic signals respectively; It also includes two sets of free-space optical emission units, which enable the two optical signals to be transmitted to the receiving end via two spatially parallel FSO channels.

4. The transmission architecture according to claim 1, characterized in that, The dual-channel FSO spatial segment includes two sets of transmitting optical units and two sets of receiving optical units, forming a first FSO channel and a second FSO channel respectively; the two spatial channels are spatially separated in terms of emission aperture, emission direction or physical position, so as to reduce the probability that atmospheric disturbances in the same area at the same time will cause deep fading to both channels simultaneously.

5. The transmission architecture according to claim 1, characterized in that, The receiving terminal system includes: Two sets of free-space optical receiving optical units are used to receive optical signals from two FSO channels respectively, and couple them to two single-mode optical fibers respectively; The receiver-side fan-in converter is used to couple two single-mode fiber signals into the two cores of the receiver-side dual-core fiber for parallel transmission. The receiving side uses a dual-core optical fiber to carry two parallel optical signals; The receiver-side fanout is used to output two single-mode fiber optic signals. Two digital signal processing modules are used to recover and evaluate the signals of their respective channels, and output the data signals and corresponding link quality indicators of each channel. And a channel selection and / or maximum ratio merging module, used to perform channel selection output and / or maximum ratio merging output based on the link quality index.

6. The transmission architecture according to claim 5, characterized in that, The operation modes of the channel selection and / or maximum ratio merging module include: (a) Channel selection: When the link quality index of one of the channels is detected to be lower than the preset threshold or a loss of lock occurs, the output is switched to another channel; (b) Maximum ratio combining: The two signals are weighted and combined based on the link quality indicators of the two channels to obtain a higher equivalent signal-to-noise ratio and receiving sensitivity.

7. The transmission architecture according to claim 6, characterized in that, The channel selection and / or maximum ratio merging module is configured to perform maximum ratio merging to improve sensitivity when both channels are available; and degrade to single-channel output or channel selection output when the quality index of either channel is continuously below the threshold or loses lock.

8. A transmission method based on dual-core optical fiber and dual-channel free-space optical communication, characterized in that, Includes the following steps: Generates two optical signals; The two optical signals are fanned into the two cores of the dual-core optical fiber for parallel transmission, and then fanned out to form two output optical signals. The two output optical signals are sent through the first free space optical channel and the second free space optical channel, respectively. Two optical signals from the first free space optical channel and the second free space optical channel are received respectively, and the two optical signals are fanned into the two cores of the dual-core optical fiber for parallel transmission and then fanned out to form two received optical signals. Digital signal processing is performed on the two received optical signals to obtain link quality indicators; And based on the link quality indicators, perform channel selection output and / or maximum ratio merging output.

9. The transmission method according to claim 8, characterized in that, The maximum ratio merging includes: determining weighting coefficients based on the link quality indicators of the two channels, weighting the two signals, and merging them for output.

10. The transmission method according to claim 8, characterized in that, When the link quality index of any channel is detected to be lower than the preset threshold or a loss of lock occurs, the output is switched to another channel.

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