An adaptive optical switching method based on FPGA platform in space optical communication

Abstract

The present invention discloses an adaptive optical switching method based on FPGA platform in space optical communication. The present invention adopts dual wavelengths λ1,λ ’ 1 for communication, λ1 is the signal light, which is used to carry the “payload”, λ ’ 1 is the beacon light, whose primary function is to carry a "header" to establish and route space links. It can also provide feedback on the quality of the atmospheric channel, thereby adjusting the rate, routing path, and even the modulation format of the λ1 signal. The relay node allocates paths for light with different functions and sources, some of which enter the electronic control system (FPGA) and some directly enter the optical switch for transmission. This helps improve communication efficiency and resolve problems such as wavelength conflicts and the impact of atmospheric turbulence. This invention solves the problems of automatic routing and adaptive selection of channels, rates, and modulation formats in star networks and cascaded star networks.

Description

Technical Field

[0001] This patent belongs to an optical switching method in the field of space optical communication, specifically to an adaptive optical switching method based on an FPGA platform in space optical communication. Background Art

[0002] Free-space optical communication is an emerging technology that uses lasers as carrier waves to transmit data, audio, video, and other information through the atmosphere or space. Its advantages include high bandwidth, high directivity, and concentrated energy, and it has been widely used in military, aerospace, and civilian applications.

[0003] Free-space optical communication is a technology that combines wireless communication with fiber-optic communication. Compared to fiber-optic communication, it offers advantages such as high freedom, flexible applications, and low cost. Compared to wireless communication, it offers advantages such as high bandwidth, frequency freedom, energy concentration, and good directionality.

[0004] Space optical communication is still in the research stage, and network establishment is relatively lagging. In addition, the variable conditions of atmospheric channels require space optical communication networks to perform real-time routing switching and changes in signal rate and modulation format.

[0005] There are currently no practical and effective solutions to the channel blockage and atmospheric turbulence problems faced by space optical communication networks, and the focus is mainly on improving the communication quality of point-to-point links. Summary of the Invention

[0006] To address issues such as obstruction, channel crosstalk, and turbulence that may arise in space optical communication networks, this paper proposes an adaptive multi-wavelength optical switching method for atmospheric channels. Based on an FPGA platform and a dual-wavelength solution, this method enables adaptive adjustment of the optical network when atmospheric conditions suddenly change. This allows each node's signal transmission rate, modulation format, and routing to be updated in real time to adapt to the ever-changing atmospheric environment, thereby forming a more mature space optical communication network.

[0007] The technical solutions of the present invention are as follows:

[0008] The optical network includes at least one relay node and at least two service nodes, wherein the two service nodes are respectively recorded as a starting service node and a target service node; the optical switching method between the starting service node and the target service node includes the following steps:

[0009] 1) The originating service node sends a beacon optical signal λ1 to a relay node. The current relay node demodulates and routes the received beacon optical signal λ1 and sends it to the target service node.

[0010] 2) The target service node configures the signal rate or service type according to the received beacon light replica signal, and then returns the current beacon light replica signal to the starting service node through the current relay node;

[0011] 3) The starting service node analyzes the error according to the replica signal of the current beacon light. If the error does not exceed the preset threshold, the starting service node adjusts the signal light λ according to the error. ’ 1 channel or rate, the starting service node transmits its own signal light ’ 1 is sent to the target service node through the current relay node, where the current relay node directly uses the optical switch to transmit the signal light of the starting service node to the target service node. ’ 1. Forward to the target service node; if the bit error exceeds the preset threshold, determine whether there are different relay nodes in the optical network;

[0012] 4) If there are different relay nodes in the optical network, repeat 1)-3), and the starting service node sends signals to the target service node through different relay nodes until the bit error does not exceed the preset threshold or traverses the relay nodes in the optical network; otherwise, reduce the link signal rate of the starting service node.

[0013] In the above 2), the relay node first demodulates the received beacon light signal λ1 to obtain demodulation information, then performs routing transformation according to the demodulation information to obtain a replica signal of the beacon light, and finally sends the replica signal of the beacon light to the target service node.

[0014] The relay node includes an optical antenna, an APT module, a circulator, a coupler, a bandpass filter, a demultiplexer, a data transceiver and analysis module, and an optical switch;

[0015] Multiple optical antennas are connected to the APT module. Each optical antenna is connected to the first port (a) of the corresponding circulator. The second port (b) of the circulator is connected to the input end of the optical switch and the input port of the data transceiver and analysis module respectively after passing through the corresponding demultiplexer. The communication port of the data transceiver and analysis module is connected to the control port of the optical switch. The third port (c) of the circulator and the output port of the data transceiver and analysis module are connected to the output port of the optical switch through the corresponding coupler. A bandpass filter is also provided between the output port of the data transceiver and analysis module and the coupler. An erbium-doped fiber amplifier is also provided between the output port of the optical switch and the coupler.

[0016] The service node includes an optical antenna, an APT module, a circulator, a bandpass filter and a data transceiver and analysis module; multiple optical antennas are connected to the APT module, each optical antenna is connected to the first port (a) of the corresponding circulator, the second port (b) of the circulator is connected to the input port of the data transceiver and analysis module after passing through the corresponding erbium-doped fiber amplifier, and the output port of the data transceiver and analysis module is connected to the third port (c) of the circulator after passing through the erbium-doped fiber amplifier and the bandpass filter.

[0017] The optical antenna is a transmissive or reflective antenna.

[0018] The beneficial effects of the present invention are:

[0019] The present invention solves the problem of automatic routing and adaptive selection of channels, rates and modulation formats in star networks and cascaded star networks.

[0020] The present invention is applicable to various star-shaped space optical networks, and can realize the establishment of routing links and adaptive signal parameter adjustment in complex atmospheric environments. It has no problem in building small and medium-sized space networks in the context of a relatively abundant number of C-band and future L-band channels, and can realize a low-power, high-speed, and flexible space optical communication link network. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the star communication network link.

[0022] Figure 2 A schematic diagram of the relay node structure.

[0023] Figure 3 A schematic diagram of the structure of a business node.

[0024] Figure 4 This is a business timing diagram.

[0025] Figure 5 A schematic diagram of an actual usage scenario. DETAILED DESCRIPTION

[0026] The details of the present invention are described below with reference to the accompanying drawings.

[0027] The optical network includes at least one relay node and at least two service nodes (i.e., terminal nodes), wherein two of the service nodes are respectively recorded as a starting service node and a target service node; Figure 1 Figure 1 is a schematic diagram of network nodes, where A, B, C, D, E, and F are service nodes, responsible for data generation, demodulation, and reception; X and Y are relay nodes, responsible for path building and signal amplification. Each service node has two operating wavelengths: λ1 and λ ’1. For example, if node A wants to communicate with node E, it will first start with λ ’ 1 modulates and sends header information, including routing information, signal rate, and signal type. Upon reaching relay node X or Y, it is received by X / Y, which then parses the routing information and switches the optical switch. The original data is then forwarded to E, where it receives and configures the receiving end accordingly, such as rate matching and service type matching. The data is then sent back to X along the original path at λ1. Returning, it eliminates the need for optical-to-electrical conversion and directly enters the optical switch back to point A. Point A compares the received data with the transmitted data to estimate the quality of the atmospheric channel. It then makes appropriate rate and path adjustments, such as reducing the speed or rerouting the signal from A->Y->E.

[0028] Figure 1 The number of service nodes and relay nodes in the system is not fixed and can be increased or decreased according to actual needs. Of course, it is also necessary to consider whether the hardware configuration can meet the requirements, that is, the number of IN / OUT ports of the optical switch and the electronic control system, and the number of transceiver modules.

[0029] The optical switching method between the starting service node and the target service node includes the following steps:

[0030] 1) The originating service node sends a beacon optical signal λ1 to a relay node. The relay node demodulates and routes the received beacon optical signal λ1 and sends it to the target service node. Specifically, the relay node first demodulates the received beacon optical signal λ1 to obtain demodulation information, then performs routing transformation based on the demodulation information to obtain a replica signal of the beacon light, and finally sends the replica signal of the beacon light to the target service node.

[0031] 2) The target service node configures the signal rate or service type according to the received beacon light replica signal, and then returns the current beacon light replica signal to the starting service node through the current relay node;

[0032] 3) The starting service node analyzes the error according to the replica signal of the current beacon light. If the error does not exceed the preset threshold, the starting service node adjusts the signal light λ according to the error. ’ 1 channel or rate or modulation format, the starting service node transmits its own signal light ’ 1 is sent to the target service node through the current relay node, where the current relay node directly uses the optical switch to transmit the signal light of the starting service node to the target service node. ’ 1 is forwarded to the target service node; that is, the signal light λ of the starting service node ’ 1. Demodulation without optoelectronic conversion. If the bit error exceeds the preset threshold, it is determined whether there are different relay nodes in the optical network.

[0033] 4) If there are different relay nodes in the optical network, repeat 1)-3), and the starting service node sends a signal to the target service node through different relay nodes until the bit error does not exceed the preset threshold or traverses the relay nodes in the optical network. After traversing the relay nodes in the optical network, it means that the bit error obtained by the starting service node based on the analysis after all relay nodes return exceeds the preset threshold, and the rate of the starting service node needs to be reduced; otherwise, that is, the bit error obtained by the starting service node based on the analysis after all relay nodes return exceeds the preset threshold, it means that the atmospheric channel environment of the link is relatively harsh, and the link signal rate and modulation format of the starting service node are reduced.

[0034] The main working principle of the present invention is: if a service node A wants to establish a link with a service node D, it first searches the routing table, confirms the corresponding header information, and modulates the corresponding routing information into the λ ’ 1. The beacon light is output from the optical module of node A, amplified by the pre-Edge fiber amplifier (EDFA), output by the collimator, and received by the optical antenna at point B. After passing through the wavelength demultiplexer at point X, it is received by the FPGA at point X, where the routing information is unpacked and the optical switch is controlled to switch the corresponding channels to align with point D (the end point). X transmits the beacon light λ ’ After regeneration, the signal is sent to point D via an optical switch. At point D, it is received by an optical antenna, decompressed, and its corresponding main signal rate, signal type, encoding format, and other information is unpacked. It is then forwarded back to point A along the original path. (Note that the return path through point X is no longer received, but is instead sent to point A via a wavelength selective coupler and circulator. This step minimizes the number of optical regenerations, saving time and preserving as much information as possible about the atmospheric channel.) Point A compares and counts the bit errors in the received beacon signal with the transmitted signal. Finally, based on the number of bit errors, it adjusts the parameters of the next signal light, λ1, such as the signal rate and modulation format. If the number of bit errors is too high, the beacon signal is recoded according to the routing table, selecting an alternative path to reach point D, avoiding this channel with poor atmospheric conditions.

[0035] In short, point A first emits a beacon light λ ’ 1. The purpose is to open up the optical path of signal light λ1, that is, "bridge", so that point A receives λ ’ 1 and then analyze the bit errors and adjust the parameters of the signal light λ1 to cope with or avoid the current atmospheric channel, ultimately achieving the goal of successful communication.

[0036] The relay node includes an optical antenna, an APT (acquisition, alignment, tracking) module, a circulator, a coupler, a bandpass filter, a demultiplexer, a data transceiver and analysis module (FPGA), and an optical switch;

[0037] Multiple optical antennas are connected to an APT (acquisition, alignment, and tracking) module. Each optical antenna is connected to the first port (a) of a corresponding circulator. The second port (b) of the circulator is connected to the input port of an optical switch and the input port of a data transceiver and analysis module (FPGA) through a corresponding demultiplexer. The communication port of the data transceiver and analysis module (FPGA) is connected to the control port of the optical switch. The third port (c) of the circulator and the output port of the data transceiver and analysis module (FPGA) are connected to the output port of the optical switch through corresponding couplers. A bandpass filter is also provided between the output port of the data transceiver and analysis module (FPGA) and the coupler. An erbium-doped fiber amplifier is also provided between the output port of the optical switch and the coupler.

[0038] Relay nodes can process beacon light and signal light differently: they receive beacon light and directly route and amplify signal light, avoiding repeated demodulation of the signal light and expediting link establishment. Each optical antenna is aligned with a fixed node. In the relay node, the optical signal is first aligned by the ATP module, then coupled into the optical fiber via the optical antenna. It then passes through a circulator, which uses a single optical antenna for both the RX and TX ends, saving ports. The optical signal entering the circulator is split into two paths after passing through a demultiplexer: one for beacon light and the other for signal light. The beacon light is received by the SFP optical module integrated in the FPGA, analyzed, and then sent via the serial port to the optical switch to change the routing channel. The FPGA then forwards the beacon light signal to the target service node. To ensure wavelength consistency, a bandpass filter is required. The target service node also demodulates the corresponding information and performs the corresponding configuration.

[0039] After passing through the coupler, the signal light is directly forwarded to the optical switch for forwarding and amplified by the erbium-doped fiber amplifier at the switch's output. The coupler couples the optical signal from the FPGA with the optical signal from the optical switch, allowing them to share a common optical antenna for transmission.

[0040] Figure 2 This is the internal structure diagram of the relay node. It should be noted that the number of its optical antennas is Figure 1 There is no need to pursue matching, because it can be increased or decreased according to actual needs and hardware conditions. Figure 2 There are three windows in the diagram, oriented towards service nodes A, B, and C, indicating that connections can be made to these three endpoints. After receiving the optical signal from the optical antenna, it first passes through a circulator, where the demultiplexer selects the wavelength. The beacon wavelength is then transmitted directly to the optical module connected to the FPGA for routing signal analysis. The module then outputs the corresponding control signal to the optical switch via the UART serial port to establish the path. Simultaneously, the received signal is forwarded to the corresponding window. The forwarded optical signal then passes through a circulator and is coupled into the atmospheric channel by the optical antenna.

[0041] Figure 2 The electronic control system is mainly undertaken by FPGA. For performance and cost considerations, Xilinx V7 series chips can be selected. SFP+ modules can be selected as external optical modules, which can achieve 5G, 10G, 25G, 40G and other speed communication. If necessary, capacity can be expanded through WDM wavelength division.

[0042] Figure 2 and Figure 3 The RX / TX modules are mainly implemented by FPGA's GTP / GTX / GTH and other high-speed serial communication IP cores and SFP+ optical modules. The optical signal rate is regulated by regulating the IP core serial rate. By integrating multiple optical modules, connections with different windows are achieved, realizing directional signal propagation.

[0043] Figure 2 The optical switching module in this system is primarily implemented through optical switches. The switch matrix establishes optical pathways between different input and output ports based on instructions. This approach utilizes a MEMS optical switch matrix. Currently, mainstream commercial optical switches include those based on mechanical galvanometers, MEMS, and SOA, with speeds ranging from nanoseconds to milliseconds. Different types of optical switch matrices can be selected based on actual needs.

[0044] The service node includes an optical antenna, an APT module, a circulator, a bandpass filter, a coupler, a demultiplexer, and a data transceiver and analysis module; multiple optical antennas are connected to the APT (acquisition, alignment, tracking) module, each optical antenna is connected to the first port (a) of the corresponding circulator, the second port (b) of the circulator is connected to the first input port of the data transceiver and analysis module (FPGA) after passing through the corresponding erbium-doped fiber amplifier, and the first output port of the data transceiver and analysis module (FPGA) is connected to the third port (c) of the circulator after passing through the erbium-doped fiber amplifier and the bandpass filter. In a specific implementation, the second input port of the data transceiver and analysis module is connected to the third input port of the data transceiver and analysis module through the demultiplexer and the second port (b) of another circulator after passing through the erbium-doped fiber amplifier, and the second output port and the third output port of the data transceiver and analysis module are connected to the third port (c) of another circulator through the coupler after passing through the corresponding erbium-doped fiber amplifier and the bandpass filter.

[0045] Figure 3 The following is a schematic diagram of the service node structure (taking node A as an example). The signal source and control system are handled by FPGA. There are two optical antenna windows aligned with X / Y respectively. Of course, two windows are not necessary. Depending on the actual situation, you can sacrifice some link selectivity and set only one window. TX1 / RX1 transmits / receives through the bandpass filter λ ’1 beacon light, and the other two transceiver ports send and receive λ1 wavelength signal light. The functions of the demultiplexer and circulator are the same. Figure 2 The relay nodes are the same and will not be described again here.

[0046] Taking into account the issues of volume, weight and cost, optical antennas can consider using transmissive types such as Kepler and Galilean types or reflective types such as Gregorian and Cassegrain types, and the size of the visible space can be adjusted accordingly.

[0047] The APT (capture, alignment, and tracking) module primarily consists of a CCD camera, a fine-tracking galvanometer, a coarse-aiming galvanometer, a beacon laser, a servo motor, and a main control system. The CCD camera captures and locates the light spot, the galvanometer adjusts the orientation of the optical antenna, and the beacon laser provides alignment. The APT modules of the master and slave nodes track each other's beacon light in real time, enabling dynamic alignment of the master and slave optical antennas and ensuring link reliability.

[0048] Figure 4 This is a schematic diagram of the link service timing. First, λ is sent ’ 1 beacon light, after receiving, analysis and routing path establishment, then sends the signal light of λ1.

[0049] The devices and materials used in this invention are mature or commercially available, with high feasibility and simple structure. This invention can address the complex link conditions, inability to optimize signal parameters, and inability to reestablish links encountered in space optical communication networks. It can also serve as an alternative communication solution in space optical communications.

[0050] The beacon and signal wavelengths used by each service node (A, B, C, etc.) mentioned in this invention are identical. However, wavelength expansion can be implemented to address network complexity, resolving wavelength congestion and improving node throughput. Accordingly, the optical switching equipment in relay nodes can be replaced with a more flexible wavelength selector (WSS).

[0051] The relay nodes (X, Y) mentioned in the present invention are not given the function of service nodes, ie uplink and downlink signal optical data flows, but can be supplemented with functions as needed, and the function expansion is not complicated.

[0052] Figure 5 The figure is a schematic diagram of actual use scenarios. A mobile flying platform can be used as a relay node, which can cover the location of business nodes over a large area. The business nodes can be land-based or sea-based platforms without restrictions. Accordingly, this system can also be used to build satellite communication links.

[0053] At the same time, the advantage of space optical communication lies not only in the present invention but also in its flexible configuration. As long as it is aligned, there is no need to build an optical fiber link. Therefore, it can be applied to disaster relief scenarios, complex mountainous scenarios, etc. to provide high-bandwidth data communication.

[0054] The above is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Any slight changes or substitutions made by any technicians related to this technical field within the technical scope stated in this application should be covered by the protection scope of the present application.

Claims

1. An adaptive optical switching method based on an FPGA platform in space optical communication, wherein the optical network includes at least one relay node and at least two service nodes, wherein the two service nodes are respectively recorded as a starting service node and a target service node; characterized in that: The optical switching method between the starting service node and the target service node comprises the following steps: 1) The originating service node sends a beacon optical signal λ1 to a relay node. The current relay node demodulates and routes the received beacon optical signal λ1 and sends it to the target service node. 2) The target service node configures the signal rate or service type based on the received beacon light replica signal, and then returns the current beacon light replica signal to the starting service node through the current relay node; 3) The starting service node analyzes the bit error based on the replica signal of the current beacon light. If the bit error does not exceed the preset threshold, the starting service node adjusts the signal light λ according to the bit error. ’ 1 channel or rate, the starting service node transmits its own signal light ’ 1 is sent to the target service node through the current relay node, where the current relay node directly uses the optical switch to transmit the signal light of the starting service node to the target service node. ’ 1. Forward to the target service node; if the bit error exceeds the preset threshold, determine whether there are different relay nodes in the optical network; 4) If there are different relay nodes in the optical network, repeat 1)-3) and the starting service node sends the signal to the target service node through different relay nodes until the bit error does not exceed the preset threshold or traverses the relay nodes in the optical network; otherwise, reduce the link signal rate of the starting service node.

2. The adaptive optical switching method based on FPGA platform in spatial optical communication according to claim 1, characterized in that: In the above 2), the relay node first demodulates the received beacon light signal λ1 to obtain demodulation information, then performs routing transformation according to the demodulation information to obtain a replica signal of the beacon light, and finally sends the replica signal of the beacon light to the target service node.

3. The adaptive optical switching method based on FPGA platform in spatial optical communication according to claim 1, characterized in that: The relay node includes an optical antenna, an APT module, a circulator, a coupler, a bandpass filter, a demultiplexer, a data transceiver and analysis module, and an optical switch; Multiple optical antennas are connected to the APT module. Each optical antenna is connected to the first port (a) of the corresponding circulator. The second port (b) of the circulator is connected to the input port of the optical switch and the input port of the data transceiver and analysis module respectively after passing through the corresponding demultiplexer. The communication port of the data transceiver and analysis module is connected to the control port of the optical switch. The third port (c) of the circulator and the output port of the data transceiver and analysis module are connected to the output port of the optical switch through the corresponding coupler. A bandpass filter is also provided between the output port of the data transceiver and analysis module and the coupler. An erbium-doped fiber amplifier is also provided between the output port of the optical switch and the coupler.

4. The adaptive optical switching method based on FPGA platform in spatial optical communication according to claim 1, characterized in that: The service node includes an optical antenna, an APT module, a circulator, a bandpass filter and a data transceiver and analysis module; multiple optical antennas are connected to the APT module, each optical antenna is connected to the first port (a) of the corresponding circulator, the second port (b) of the circulator is connected to the input port of the data transceiver and analysis module after passing through the corresponding erbium-doped fiber amplifier, and the output port of the data transceiver and analysis module is connected to the third port (c) of the circulator after passing through the erbium-doped fiber amplifier and the bandpass filter.

5. The adaptive optical switching method based on FPGA platform in spatial optical communication according to claim 3, characterized in that: The optical antenna is a transmissive or reflective antenna.

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