Underwater wireless optical communication adaptive transmit-receive system

Abstract

The invention provides an underwater wireless optical communication adaptive transceiving system, which comprises a signal transmitter and a signal receiver, and is characterized in that the signal transmitter comprises a plurality of direct modulation semiconductor lasers and a modulation unit capable of converting digital signals into analog signals for modulation of the semiconductor lasers. The signal receiver comprises a spectroscope, an optical power meter probe and a signal receiver; the signal receiver captures optical signals through the digital signal processing module by using the plurality of optical detectors and converts the optical signals into electric signals, and the electric signals pass through the analog-to-digital converter and are output to the FPGA board card in the form of digital signals. According to the invention, service transmission can be carried out in real time, so that the problem of bandwidth limitation easily occurring when a single channel transmits a high-rate signal is solved, and the overall transmission rate or anti-interference capability of the system is further improved.

Description

Technical Field

[0001] This invention belongs to the field of underwater optical communication, specifically relating to an underwater wireless optical communication adaptive transceiver system. Background Technology

[0002] Underwater channels have a blue-green light "transparent window," and common underwater optical communications typically use one of these wavelengths as the transmission channel. To increase the transmission rate of a single-channel simplex communication system, there are only two methods: changing the modulation and demodulation method or increasing the modulation clock rate. If an excessively high-speed signal is loaded onto a single path, the received signal waveform will often exhibit bandwidth limitation due to the bandwidth constraints at both the transmitting and receiving ends. Summary of the Invention

[0003] An underwater wireless optical communication adaptive transceiver system includes a signal transmitter and a signal receiver, wherein the signal receiver is pre-filtered.

[0004] The signal transmitter has a number of directly modulated semiconductor lasers built in, as well as a modulation unit that can convert digital signals into analog signals for modulation of the semiconductor lasers.

[0005] The signal receiver includes a beam splitter, an optical power meter probe, and a signal receiver;

[0006] The signal receiver has a built-in receiver circuit and FPGA board.

[0007] The receiver circuit is equipped with several photodetectors. The digital signal processing module uses the photodetectors to capture optical signals and convert them into electrical signals. The electrical signals are then converted into digital signals by an analog-to-digital converter and output to the FPGA board.

[0008] The signal transmitter is covered with a light-blocking cloth.

[0009] The entire signal receiver is housed in a black box.

[0010] The photodetector is a silicon photomultiplier tube.

[0011] The semiconductor laser emits laser wavelengths including 405nm, 450nm, 525nm, and 650nm.

[0012] The semiconductor lasers are all loaded onto the laser modulation circuit and controlled by digital signals output from the FPGA.

[0013] The filtering device is a narrowband filter that selects optical signals of a specific waveform from the optical signals.

[0014] The narrowband filter is equipped with an attenuator, which is fixed to the signal receiver by a front shield frame; the attenuator can be a liquid crystal display.

[0015] This invention proposes an underwater laser communication technology based on wavelength division multiplexing, which can transmit services in real time. This alleviates the bandwidth limitation problem that easily occurs when a single channel transmits high-speed signals, and further improves the overall transmission rate or anti-interference capability of the system. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 Schematic diagram of an underwater wireless optical communication adaptive transceiver system;

[0018] Figure 2 Schematic diagram of signal transmission in an underwater wireless optical communication adaptive transceiver system;

[0019] Figure 3 Schematic diagram of an underwater wireless optical communication adaptive transceiver system;

[0020] Figure 4 Receiver circuit diagram;

[0021] Figure 5 Silicon photomultiplier tube front shielding frame;

[0022] Figure 6 Single laser service transmission rate versus received optical power curve;

[0023] Figure 7 Curves of transmission bit error rate versus received optical power in multiplexing mode at different modulation rates;

[0024] Figure 8 Self-regulating mode service transmission rate and received optical power curve. Detailed Implementation

[0025] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0026] Figure 1 A schematic diagram of an underwater wireless optical communication adaptive transceiver system is provided. The system includes a signal transmitter and a signal receiver, with a filter device preceding the signal receiver.

[0027] The signal transmitter incorporates several directly modulated semiconductor lasers and a modulation unit that converts digital signals into analog signals for modulation of the semiconductor lasers. The signal transmitter is covered with a light-shielding cloth. The semiconductor lasers emit laser wavelengths of 405nm, 450nm, 525nm, and 650nm. All semiconductor lasers are connected to a laser modulation circuit and controlled by digital signals output from an FPGA.

[0028] The signal receiver includes a beam splitter, an optical power meter probe, and a signal receiver; the signal receiver integrates receiver circuitry and an FPGA board. The receiver circuitry is equipped with several photodetectors. The digital signal processing module uses these photodetectors to capture optical signals and convert them into electrical signals. The electrical signals are then converted into digital signals by an analog-to-digital converter and output to the FPGA board. The entire signal receiver is housed in a black box.

[0029] Photodetectors can be made of silicon photomultiplier tubes.

[0030] The filtering device is a narrowband filter that selects optical signals of a specific waveform from the optical signals.

[0031] The narrowband filter is equipped with an attenuator, which is fixed to the signal receiver by a front shield frame; the attenuator can be a liquid crystal display.

[0032] Figure 2 A schematic diagram of signal transmission in an underwater wireless optical communication adaptive transceiver system is presented. The input signal is modulated and encoded by a laser modulation circuit, then converted from digital to analog to optical signal. After passing through the underwater channel, the optical signal is captured by a photodetector, specifically a silicon photomultiplier tube, and converted into an electrical signal. The electrical signal is then converted into a digital signal by an analog-to-digital converter and output to the FPGA.

[0033] Example 1.

[0034] To verify the feasibility and technical effectiveness of the technical solution of this invention, an underwater wireless optical communication adaptive transceiver system is provided, such as... Figure 3 As shown, it includes a signal transmitter and a signal receiver; the signal transmitter is covered with a light-shielding cloth, and the signal transmitter has four built-in semiconductor lasers, which produce wavelengths of 405nm, 450nm, 525nm and 650nm respectively. Each semiconductor laser is loaded onto a laser modulation circuit and controlled by a digital signal output by an FPGA.

[0035] In this embodiment, a 1-meter-long water tank is used to construct the underwater optical communication transmission channel. After propagating underwater, the light is scattered into an irregular spot, and the narrowband filter of the signal receiver separates the light of different wavelengths. A silicon photomultiplier tube (MPPC) is used to capture the optical signal and convert it into an electrical signal. Then, the electrical signal is transmitted via an analog-to-digital converter to the pins of the FPGA chip for acquisition.

[0036] In this embodiment, the beam splitter disperses the optical signal to the optical power meter probe at a fixed ratio, facilitating the viewing of real-time optical power.

[0037] The signal receiver uses narrowband filters corresponding to wavelengths of 405nm, 450nm, 525nm, and 650nm, which can separate the corresponding laser beams from the combined laser beam.

[0038] Each narrowband filter is equipped with an attenuator. In this embodiment, the attenuator can be a liquid crystal display (LCD) to control the optical signal intensity of the receiver circuit, facilitating the plotting of curves. It is fixed to the receiver circuit via a front shield frame.

[0039] Figure 4 A schematic diagram of the receiver circuit design is provided;

[0040] Figure 5 A schematic diagram of the front shielding frame structure for a silicon photomultiplier tube is given.

[0041] Figure 6 To illustrate the use of a 1-meter-long water tank to construct an underwater optical communication transmission channel, and the transmission using a single laser channel, it can be seen that the maximum modulation frequency supported by this underwater channel is 25MHz, corresponding to a measured transmission rate of 6.0Mbps.

[0042] By further altering the light intensity of the receiver using a liquid crystal valve, a curve showing the relationship between the communication error rate and the received light intensity can be obtained. For example... Figure 7 When the modulation frequency is 20MHz and the received optical power is 0.55μW, the bit error rate is reduced to 2.103×10⁻⁶, and the service transmission rate reaches 19.21Mbps, which is 3.2 times the maximum service transmission rate using only a single laser channel. The bit error rate increases when the received optical power exceeds a certain value, and the higher the modulation rate, the greater the impact.

[0043] Further tests were conducted on the received optical intensity and corresponding data rate in 20MHz multiplexing mode, 10MHz multiplexing mode, and 20MHz self-adjustment mode. Figure 8 It can be seen that when the optical power is between 0.51 and 0.60 mμW, the optical power of the receiver is in the optimal state. In the self-regulation mode, several channels are transmitting at full rate, and the service transmission rate of the communication system is consistent with the multiplexing mode of the 20MHz modulation clock.

[0044] When the optical power is not in this range, the self-regulating mode switches each channel to half-rate transmission, and the overall speed is reduced to ensure the transmission effect. The system transmission rate is dynamically adjusted between 20MHz multiplexing mode and 10MHz multiplexing mode to continuously maximize the use of channel bandwidth.

Claims

1. An underwater wireless optical communication adaptive transceiver system, characterized in that, It includes a signal transmitter and a signal receiver, wherein the signal receiver is equipped with a filter device in front of it; The signal transmitter has a number of directly modulated semiconductor lasers built in, as well as a modulation unit that can convert digital signals into analog signals for modulation of the semiconductor lasers; The signal receiver includes a beam splitter, an optical power meter probe, and a signal receiver; The signal receiver has a built-in receiver circuit and FPGA board; The receiver circuit is equipped with several photodetectors. The digital signal processing module uses the photodetectors to capture optical signals and convert them into electrical signals. The electrical signals are then converted into digital signals by an analog-to-digital converter and output to the FPGA board.

2. The underwater wireless optical communication adaptive transceiver system according to claim 1, characterized in that, The signal transmitter is covered with a light-blocking cloth.

3. The underwater wireless optical communication adaptive transceiver system according to claim 1, characterized in that, The entire signal receiver is housed in a black box.

4. The underwater wireless optical communication adaptive transceiver system according to claim 1, characterized in that, The photodetector is a silicon photomultiplier tube.

5. The underwater wireless optical communication adaptive transceiver system according to claim 1, characterized in that, The semiconductor laser emits laser wavelengths including 405nm, 450nm, 525nm, and 650nm.

6. The underwater wireless optical communication adaptive transceiver system according to claim 1, characterized in that, The semiconductor lasers are all loaded onto the laser modulation circuit and controlled by digital signals output from the FPGA.

7. The underwater wireless optical communication adaptive transceiver system according to claim 1, characterized in that, The filtering device is a narrowband filter that selects optical signals of a specific waveform from the optical signals.

8. The underwater wireless optical communication adaptive transceiver system according to claim 7, characterized in that, The narrowband filter is equipped with an attenuator, which is fixed to the signal receiver by a front shield frame; the attenuator can be a liquid crystal display.

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