Underwater wireless optical communication large dynamic power range receiving method

Abstract

The invention discloses an underwater wireless optical communication large-dynamic-power-range receiving method. The method comprises the steps that the maximum amplitude and the minimum amplitude of a communication voltage signal are set in a control module when a signal processing module works; output voltage parameters of the adjustable voltage module and the multiplication voltage module are set in the control module in a grading manner according to the variation range of the transmittance of the communication optical signal after passing through the electrochromic glass and the working voltage range of the electrochromic glass; attenuating the communication optical signal by using the electrochromic glass; converting the attenuated communication optical signal into a communication current signal by using a photomultiplier; converting the communication current signal into a communication voltage signal by using a trans-impedance amplifier; measuring the amplitude of the communication voltage signal by using a signal monitoring module; the control module adjusts output voltage parameters of the adjustable voltage module and the multiplication voltage module according to the amplitude of the communication voltage signal, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude, and the signal processing module recovers original communication data.

Description

Technical Field

[0001] The present invention belongs to the technical field of underwater wireless communications, and in particular relates to a large dynamic power range receiving method for underwater wireless optical communications. Background Art

[0002] Underwater communications are crucial for advancing marine informatization. Because electromagnetic waves attenuate significantly when transmitted underwater, common land-based radio communications are unsuitable for underwater applications. Current underwater data transmission relies primarily on fiber-optic and underwater acoustic communications. Fiber-optic communications transmit information via optical cables laid in the ocean, offering high transmission rates. However, deployment is challenging, costly, and lacks maneuverability. Underwater acoustic communications use sound waves as information carriers, transmitting data through acoustic signals in seawater. This method offers high maneuverability and long transmission distances, but due to limitations in acoustic bandwidth, communication rates are typically in the kilobits per second range. In recent years, underwater wireless optical communications have attracted widespread attention in the marine sector due to their high transmission rates, high maneuverability, and low power consumption. This type of communication typically uses visible light as the information carrier, transmitting information wirelessly through light waves transmitted underwater. This communication method is generally used to address the challenge of wirelessly transmitting large amounts of data over short distances underwater. In practical applications, the optical attenuation of seawater varies significantly across different sea areas and can change over time. Furthermore, the transmission distance and pointing accuracy of transmitters and receivers during communications are affected by operational conditions, which can cause variations in the optical signal power entering the receiver. This requires the receiver to have the ability to adjust itself to these fluctuations in optical power.

[0003] In the related art, Chinese invention patent CN112737691B (authorization announcement number) discloses an underwater wireless optical communication receiving method and device based on gain control in the detector. This method uses PMT (PhotoMultiplier Tube) as a signal detection device. By changing the multiplication voltage loaded between the cathode and anode in the PMT, the detection sensitivity of the device is changed, thereby realizing the detection of different optical power signals and increasing the receiving optical power range of the receiving device. This method can improve the dynamic detection range of the receiver to a certain extent, but it cannot identify the saturation problem that may occur on the photosensitive surface of the detector. Under strong light irradiation, there is still a risk of damaging the communication receiver detector. In addition, the change of the multiplication voltage will cause the output waveform of the PMT to change, thereby affecting the communication quality.

[0004] Chinese invention patent 202310133796.7 (application number) discloses an underwater wireless optical communication receiving device and method based on a multi-anode photomultiplier tube. This method uses a multi-anode PMT as a photodetector and increases the device's dynamic range by adding attenuation plates with different transmittances to different photosensitive regions of the multi-anode PMT. However, due to crosstalk between the different photosensitive regions of the multi-anode PMT, the achievable effective dynamic range is limited.

[0005] Chinese invention patent 202310182430.9 (application number) discloses a method and device for underwater wireless optical communication reception based on polymer-dispersed liquid crystals. This method incorporates a polymer-dispersed liquid crystal device into the receiver and controls the operating voltage of the device to vary the optical power entering the photodetector, thereby achieving high-dynamic reception of communication signals. However, this device suffers from high insertion loss for optical signals, is bulky, and has a limited linear adjustable range of optical power, limiting its application in engineering.

[0006] In his paper "Research on Dynamic Control Technology for Underwater High-Speed ​​Blue-Green Laser Communications," Ning Jie of the Beijing University of Posts and Telecommunications proposed a design for dynamic control based on a liquid crystal light valve and PMT gain. This method places an liquid crystal light valve in front of the PMT. Adjusting the PMT gain voltage modulates the detector's sensitivity. Furthermore, by adjusting the voltage of the liquid crystal light valve, the optical power entering the PMT is adjusted using the principle of polarization interferometry. Liquid crystal light valves are generally large, and polarization interferometry limits the receiver's field of view. Therefore, this device is bulky and hinders the ability to increase the receiver's field of view.

[0007] In addition, by adding devices such as mechanical optical attenuators and MEMS (Micro-Electro-Mechanical Systems) optical attenuators to the front end of the detector in the receiver, the light power entering the photodetector can be adjusted by adjusting the transmittance of the attenuator, thereby increasing the dynamic range of the receiver. Mechanical optical attenuators have a simple principle and a large attenuation range, but they are prone to wear, bulky, and have slow response speeds. MEMS optical attenuators replace the traditional mechanical attenuator's drive mechanism with an electrostatic opening and closing bridge or piezoelectric drive, resulting in a smaller size and lower cost, but their attenuation range is not as good as that of traditional mechanical attenuators. Summary of the Invention

[0008] In order to solve the above problems existing in the prior art, the present invention provides a method for receiving underwater wireless optical communications with a large dynamic power range. The technical problem to be solved by the present invention is achieved through the following technical solutions: An embodiment of the present invention provides a large dynamic power range receiving method for underwater wireless optical communication, which is applied to an underwater wireless communication receiving device including electrochromic glass, an adjustable voltage module, a photomultiplier tube, a voltage multiplier module, a transimpedance amplifier, a signal monitoring module, a control module, and a signal processing module. The corresponding method includes: S1. Setting the maximum amplitude and minimum amplitude of the communication voltage signal when the signal processing module is in normal operation in the control module; S2. Setting the output voltage parameters of the adjustable voltage module and the output voltage parameters of the voltage multiplier module in the control module in stages according to the transmittance variation range of the communication optical signal after passing through the electrochromic glass, the operating voltage range of the electrochromic glass, the operating voltage range of the photomultiplier tube, and the selected transimpedance amplifier; S3. Attenuating the received communication optical signal using electrochromic glass to obtain an attenuated communication optical signal; S4, using a photomultiplier tube to convert the attenuated communication light signal into a communication current signal; S5. Converting the communication current signal into a communication voltage signal using a transimpedance amplifier; S6. Measuring the amplitude of the communication voltage signal using a signal monitoring module; S7. The control module adjusts the output voltage parameters of the adjustable voltage module and the voltage multiplier module according to the amplitude of the communication voltage signal, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude; S8. The signal processing module restores the original communication data according to the communication voltage signal between the maximum amplitude and the minimum amplitude.

[0009] Beneficial effects of the present invention: The present invention proposes a method for receiving underwater wireless optical communications with a large dynamic power range. First, an underwater wireless communication receiving device comprising electrochromic glass, an adjustable voltage module, a photomultiplier tube, a voltage multiplier module, a transimpedance amplifier, a signal monitoring module, a control module, and a signal processing module is innovatively proposed. Based on the proposed underwater wireless communication receiving device, a corresponding method for receiving underwater wireless optical communications with a large dynamic power range is further proposed, and the feasibility of the method is verified through experiments. More specifically, the method has the following advantages: (1) Compared with the traditional method of changing the sensitivity of a photomultiplier tube by adjusting the voltage between the anode and cathode, the present invention adds electrochromic glass to the front end of the photomultiplier tube. In addition to adjusting the voltage between the anode and cathode of the photomultiplier tube to change its sensitivity, the transmittance of the communication optical signal can also be changed by adjusting the working voltage of the electrochromic glass, thereby further increasing the receiving optical power range of the receiver.

[0010] (2) The present invention uses electrochromic glass to change the transmittance of the device through an electrical control method, thereby further increasing the dynamic range of the receiver. Compared with traditional mechanical attenuators and MEMS attenuators, this method has higher precision, smaller size, and no wear; compared with polymer dispersed liquid crystals, it has lower insertion loss; compared with liquid crystal light valves, the field of view is not affected, which is conducive to increasing the field of view of the receiver.

[0011] (3) Compared with the traditional underwater wireless optical communication receiving device, the present invention only adds electrochromic glass at the hardware level, and only adds a control module for the working voltage of the photomultiplier tube and a control module for the working voltage of the electrochromic glass at the software level. It has a simple structure, strong portability, and is easy to promote and apply.

[0012] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 1 is a schematic diagram of an underwater wireless communication receiving device provided by an embodiment of the present invention; Figure 2 This is a flow chart of a method for receiving underwater wireless optical communications with a large dynamic power range, provided by an embodiment of the present invention; Figure 3 This is a schematic diagram of an experimental system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0014] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0015] The embodiment of the present invention first proposes a method as follows Figure 1The underwater wireless communication receiving device shown includes electrochromic glass, an adjustable voltage module, a photomultiplier tube, a voltage multiplier module, a transimpedance amplifier, a signal monitoring module, a control module, and a signal processing module. The electrochromic glass is configured to attenuate received communication optical signals, and its operating voltage can be adjusted to change the transmittance of the communication optical signals after passing through the electrochromic glass. The adjustable voltage module is configured to provide an adjustable DC voltage to the electrochromic glass. The photomultiplier tube is configured to convert the communication optical signals attenuated by the electrochromic glass into communication current signals. The voltage multiplier module is configured to provide the multiplication voltage required for the normal operation of the photomultiplier tube and to control the operating voltage between the cathode and anode of the photomultiplier tube. The transimpedance amplifier is configured to convert the communication current signal output by the photomultiplier tube into a communication voltage signal. The signal monitoring module is configured to monitor the amplitude of the communication voltage signal output by the transimpedance amplifier. The control module is configured to control the voltage multiplier module to change the operating voltage applied between the anode and cathode of the photomultiplier tube and the operating voltage applied by the adjustable voltage module to the electrochromic glass based on the output of the signal monitoring module, and to feed back the output of the signal monitoring module, as well as the voltage information of the voltage multiplier module and the adjustable voltage module, to the signal processing module. The signal processing module recovers communication data from the received communication voltage signal.

[0016] It should be noted that electrochromic glass is a type of glass with electrochromic materials added. Under the action of an external electric field, the electrochromic material undergoes a reversible electrochemical reaction, causing the transmittance of the communication light signal after passing through the glass to change. By controlling the voltage loaded on the two electrodes of the electrochromic material, the external electric field can be changed, and thus the transmittance of the electrochromic glass can be changed.

[0017] based on Figure 1 The underwater wireless communication receiving device shown is shown in Figure 2 The embodiment of the present invention further provides a method for receiving underwater wireless optical communication with a large dynamic power range, which specifically includes the following steps: S1. Setting the maximum amplitude and minimum amplitude of the communication voltage signal when the signal processing module is in normal operation in the control module.

[0018] S2. According to the transmittance variation range of the communication optical signal after passing through the electrochromic glass, the operating voltage range of the electrochromic glass, the operating voltage range of the photomultiplier tube, and the selected transimpedance amplifier, the output voltage parameters of the adjustable voltage module and the output voltage parameters of the voltage multiplier module are set in the control module in stages.

[0019] S3. Using the electrochromic glass to attenuate the received communication optical signal to obtain an attenuated communication optical signal.

[0020] S4, using a photomultiplier tube to convert the attenuated communication light signal into a communication current signal; S5, converting the communication current signal into a communication voltage signal using a transimpedance amplifier; S6. Measuring the amplitude of the communication voltage signal using the signal monitoring module; S7. The control module adjusts the output voltage parameters of the adjustable voltage module and the voltage multiplier module according to the amplitude of the communication voltage signal, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude; S8. The signal processing module restores the original communication data according to the communication voltage signal between the maximum amplitude and the minimum amplitude.

[0021] In embodiment S1 of the present invention, the maximum amplitude and minimum amplitude of the communication voltage signal that enable the signal processing module to work normally are set in the control module. The maximum amplitude and minimum amplitude of the communication voltage signal that enable the signal processing module to work normally here refer to the maximum amplitude and minimum amplitude of the communication voltage signal when the communication voltage signal input from the transimpedance amplifier to the signal processing module enables the signal processing module to recover the communication data.

[0022] In embodiment S2 of the present invention, the output voltage parameters of the adjustable voltage module and the voltage multiplier module are set in stages in the control module based on the transmittance variation range of the communication optical signal after passing through the electrochromic glass, the operating voltage range of the electrochromic glass, the operating voltage range of the photomultiplier tube, and the selected transimpedance amplifier. The specific steps include: S2-1. Select parallel light with the same wavelength as the communication optical signal as the light source, and make the parallel light incident vertically on the optical power meter to measure the optical power of the parallel light.

[0023] S2-2. Direct parallel light vertically into the electrochromic glass and measure the transmitted light power using an optical power meter. Based on the operating voltage range of the electrochromic glass, starting from the minimum operating voltage of the electrochromic glass, continuously increase the operating voltage applied to the electrochromic glass at preset step intervals. Each time the operating voltage of the electrochromic glass changes, measure the power value of the transmitted light after it stabilizes. Calculate the transmittance of the electrochromic glass at different operating voltages based on the optical power of the parallel light and the stabilized power value after each change in the operating voltage of the electrochromic glass. The calculation formula can be expressed as: ,in, represents transmittance, It represents the optical power of parallel light measured by S2-1. It represents the stable power value after each change in the working voltage of the electrochromic glass. It can be understood that the transmittance of the electrochromic glass under different working voltages can be obtained through S2-2.

[0024] S2-3, compare the transmittance of the electrochromic glass at different operating voltages to obtain the maximum transmittance and the minimum transmittance of the electrochromic glass, calculate the ratio between the maximum transmittance and the minimum transmittance, and use the ratio as the first ratio; the maximum transmittance and minimum transmittance , which is the variation range of the transmittance of the electrochromic glass, then calculate the first ratio The formula can be expressed as: . S2-4. Use a bit error analyzer to generate a pseudo-random binary sequence, modulate parallel light to produce an analog optical signal, convert the analog optical signal into an analog voltage signal through a photomultiplier tube and a transimpedance amplifier, and input it into the bit error analyzer for bit error rate testing. In S2-4, the random binary sequence and the communication optical signal have the same modulation rate.

[0025] S2-5. Based on the bit error rate test results and the operating voltage range of the photomultiplier tube, obtain the maximum operating voltage applied between the anode and cathode of the photomultiplier tube and the simulated optical power corresponding to the maximum operating voltage, as well as the minimum operating voltage applied between the anode and cathode of the photomultiplier tube and the simulated optical power corresponding to the minimum operating voltage. In embodiment S2-5 of the present invention, based on the bit error rate test results, obtain the maximum operating voltage applied between the anode and cathode of the photomultiplier tube and the simulated optical power corresponding to the maximum operating voltage, as well as the minimum operating voltage applied between the anode and cathode of the photomultiplier tube and the simulated optical power corresponding to the minimum operating voltage, specifically the following steps: S2-5-1. Based on the operating voltage range between the anode and cathode of the photomultiplier tube, starting from the minimum operating voltage, continuously increase the operating voltage applied between the anode and cathode of the photomultiplier tube at a preset step interval. After each increase in the operating voltage applied between the anode and cathode of the photomultiplier tube, control the power of the analog optical signal so that the amplitude of the analog voltage signal is equal to the average of the maximum and minimum amplitudes of the communication voltage signal when the signal processing module is in normal operation, and record the bit error rate measured by the bit error analyzer; S2-5-2. For each bit error rate measured by the bit error analyzer, the execution process includes: determining whether the bit error rate currently measured by the bit error analyzer reaches the bit error rate upper limit required by the underwater wireless communication receiving device; if not, recording the current operating voltage applied between the anode and cathode of the electromultiplier tube and the optical power of the analog optical signal corresponding to the operating voltage; S2-5-3. Select the largest working voltage from all recorded working voltages loaded between the anode and cathode of the photomultiplier tube as the maximum working voltage loaded between the anode and cathode of the photomultiplier tube and record it. Select the smallest working voltage as the minimum working voltage loaded between the anode and cathode of the photomultiplier tube and record it. At the same time, record the simulated light power corresponding to the maximum working voltage as the minimum simulated light power, and the simulated light power corresponding to the minimum working voltage as the maximum simulated light power.

[0026] S2-6, calculate the ratio between the simulated optical power corresponding to the maximum operating voltage and the simulated optical power corresponding to the minimum operating voltage, and use the ratio as the second ratio; calculate the second ratio The formula can be expressed as: , Indicates the simulated optical power corresponding to the maximum operating voltage, Indicates the simulated optical power corresponding to the minimum operating voltage. S2-7, calculating the number of adjustable levels of the electrochromic glass according to the first ratio and the second ratio; calculating the number of adjustable levels of the electrochromic glass The formula is: ,in," ” indicates rounding up.

[0027] S2-8. In the control module, the maximum output voltage parameter of the multiplier voltage module is set to the maximum operating voltage loaded between the anode and cathode of the photomultiplier tube, and the minimum output voltage parameter is set to the minimum operating voltage loaded between the anode and cathode of the photomultiplier tube. Multiple output voltage parameters are set between the minimum operating voltage and the maximum operating voltage according to a preset step interval.

[0028] S2-9, in the control module, according to the adjustable gear number, the second ratio, the maximum transmittance and the minimum transmittance, the transmittance is respectively 、 、 、……、 、 The corresponding voltage sets the output voltage parameters of the adjustable voltage module; is the maximum transmittance, is the minimum transmittance, N The number of gears can be adjusted in steps. b is the second ratio.

[0029] In embodiment S6 of the present invention, the amplitude of the communication voltage signal is measured using a signal monitoring module, including: measuring the communication voltage signal according to a preset sampling period and sampling rate, and taking the maximum amplitude of all communication voltage signals measured within the sampling period as the amplitude of the communication voltage signal measured by the signal monitoring module.

[0030] In embodiment S7 of the present invention, the control module adjusts the output voltage parameters of the adjustable voltage module and the voltage multiplier module according to the amplitude of the communication voltage signal, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude. This is obtained by comparing the amplitude of the communication voltage signal with the maximum amplitude and the minimum amplitude of the communication voltage signal that enable the signal processing module to operate normally in S1, and is divided into the following situations: When the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude, the output voltage parameters of the adjustable voltage module and the multiplying voltage module in the control module are kept unchanged; when the amplitude of the communication voltage signal is greater than the maximum amplitude, the control module reduces the transmittance of the electrochromic glass by changing the output voltage parameters of the adjustable voltage module, and reduces the output voltage of the multiplying voltage module by changing the output voltage parameters of the multiplying voltage module, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude; when the amplitude of the communication voltage signal is less than the minimum amplitude, the control module increases the transmittance of the electrochromic glass by changing the output voltage parameters of the adjustable voltage module, and increases the output voltage of the multiplying voltage module by changing the output voltage parameters of the multiplying voltage module, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude. More specifically: When the amplitude of the communication voltage signal is greater than the maximum amplitude, the control module reduces the transmittance of the electrochromic glass by changing the output voltage parameters of the adjustable voltage module and reducing the output voltage of the multiplying voltage module by changing the output voltage parameters of the multiplying voltage module, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude, including: When the output voltage of the voltage multiplier module is at a preset minimum voltage and the amplitude of the communication voltage signal is greater than the maximum amplitude, the control module reduces the transmittance of the electrochromic glass by one level by changing the output voltage parameters of the adjustable voltage module. At this time, if the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude, the output voltage parameters of the adjustable voltage module and the voltage multiplier module in the control module are kept unchanged. If the amplitude of the communication voltage signal is still greater than the maximum amplitude, the control module reduces the transmittance of the electrochromic glass by another level by changing the output voltage parameters of the adjustable voltage module. At this time, if the amplitude of the communication voltage signal is less than the minimum amplitude, the control module increases the output voltage of the voltage multiplier module by changing the output voltage parameters of the voltage multiplier module, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude.

[0031] When the amplitude of the communication voltage signal is greater than the maximum amplitude, the control module reduces the transmittance of the electrochromic glass by changing the output voltage parameter of the adjustable voltage module, and reduces the output voltage of the multiplying voltage module by changing the output voltage parameter of the multiplying voltage module, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude, and further includes: When the output voltage of the voltage multiplier module is at the preset minimum voltage, the transmittance of the electrochromic glass is the minimum transmittance, and the amplitude of the communication voltage signal is greater than the maximum amplitude, the output voltage parameters of the adjustable voltage module and the voltage multiplier module in the control module are kept unchanged, and the output result of the signal detection module, as well as the voltage information of the voltage multiplier module and the adjustable voltage module are fed back to the signal processing module.

[0032] When the amplitude of the communication voltage signal is less than the minimum amplitude, the control module increases the transmittance of the electrochromic glass by changing the output voltage parameters of the adjustable voltage module and increases the output voltage of the multiplying voltage module by changing the output voltage parameters of the multiplying voltage module, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude, including: When the output voltage of the voltage multiplier module is at a preset maximum voltage and the amplitude of the communication voltage signal is less than the minimum amplitude, the control module increases the transmittance of the electrochromic glass by one level by changing the output voltage parameters of the adjustable voltage module. At this time, if the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude, the output voltage parameters of the adjustable voltage module and the voltage multiplier module in the control module are kept unchanged. If the amplitude of the communication voltage signal is still less than the minimum amplitude, the control module increases the transmittance of the electrochromic glass by another level by changing the output voltage parameters of the adjustable voltage module. At this time, if the amplitude of the communication voltage signal is greater than the maximum amplitude, the control module reduces the output voltage of the voltage multiplier module by changing the output voltage parameters of the voltage multiplier module, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude.

[0033] When the amplitude of the communication voltage signal is less than the minimum amplitude, the control module increases the transmittance of the electrochromic glass by changing the output voltage parameter of the adjustable voltage module and changes the output voltage parameter of the multiplying voltage module to increase the output voltage of the multiplying voltage module, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude, and further includes: When the output voltage of the voltage multiplier module is at the preset maximum voltage, the transmittance of the electrochromic glass is the maximum transmittance, and the amplitude of the communication voltage signal is less than the minimum amplitude, the output voltage parameters of the adjustable voltage module and the voltage multiplier module in the control module are kept unchanged, and the output result of the signal detection module, as well as the voltage information of the voltage multiplier module and the adjustable voltage module are fed back to the signal processing module.

[0034] In the embodiment of the present invention, the control module S7 adjusts the output voltage parameters of the adjustable voltage module and the voltage multiplier module based on the amplitude of the communication voltage signal, so that the amplitude of the communication voltage signal is between the maximum and minimum amplitudes. After each change in the output voltage of the adjustable voltage module and the operating voltage applied to the cathode and anode of the photomultiplier tube by the voltage multiplier module, a certain delay time is reserved before monitoring the amplitude of the communication voltage signal. The lengths of these two delay times are determined by the time required for the transmittance of the electrochromic glass to reach stability after the applied voltage changes, and the time required for the operating state of the cathode and anode of the photomultiplier tube to reach stability after the applied voltage changes, respectively. Furthermore, these two delay times are greater than the sampling period used by the signal monitoring module in S6 to measure the amplitude of the communication voltage signal.

[0035] In the embodiment S8 of the present invention, the signal processing module recovers the original communication data based on the communication voltage signal between the maximum and minimum amplitudes. If the communication voltage signal is not between the maximum and minimum amplitudes, it is determined that the underwater wireless communication receiving device is not functioning properly and communication is terminated.

[0036] In order to verify the effectiveness of the large dynamic power range receiving method for underwater wireless optical communication provided by the embodiment of the present invention, the following experiments were conducted for verification.

[0037] like Figure 3 As shown, the experimental system includes computers 1# and 2#, as well as a first communication device and a second communication device. Computers 1# and 2# are placed above the water surface to simulate two-way communication terminals and are connected to the first and second communication devices via watertight cables 1# and 2#, respectively.

[0038] The first communication device transmits the data to be sent into the water via blue light, receives the green light signal in the water, and recovers the communication data from it. It is composed of a communication control unit 1#, a blue light emitting unit, a green light filter, and the device 1# provided by the present invention. The communication control unit 1# has an Ethernet external interface, controls the blue light emitting unit to send the data to be sent from the network into the water, and receives the green light signal from the water. The blue light emitting unit transmits blue light with a central wavelength of 450nm and a divergence angle of 40° into the water as the communication transmission signal. The green light filter is used to filter out stray light in the water and only receives the green light communication signal with a central wavelength of 520nm. The device 1# provided by the present invention is an underwater wireless communication receiving device made based on the present invention, which is used to convert the high-power range green light signal into a voltage signal and recover the original communication data from it.

[0039] The second communication device transmits the data to be sent into the water via green light, receives the blue light signal in the water, and recovers the communication data from it. It is composed of a communication control unit 2#, a green light emitting unit, a blue light filter, and the device 2# provided by the present invention. The communication control unit 2# has an Ethernet external interface, controls the green light emitting unit to transmit the data to be sent from the network into the water, and receives the blue light signal from the water. The green light emitting unit transmits green light with a central wavelength of 520nm and a divergence angle of 40° into the water as the communication transmission signal. The blue light filter is used to filter out stray light in the water and only receives the blue light communication signal with a central wavelength of 450nm. The device 2# provided by the present invention is an underwater wireless communication receiving device made based on the present invention, which is used to convert the high-power range blue light signal into a voltage signal and recover the original communication data from it.

[0040] For the first communication machine, the modulation rate of the blue light emitting unit is set to 125Mbps. According to the method provided by the present invention, the maximum amplitude and minimum amplitude of the communication voltage signal of the control module in the device 1# provided by the present invention that enable the signal processing module to work normally are set to 1.5V and 0.3V respectively; the working state of the color-changing glass is set to two gears, and the corresponding voltages are 0.1V and 1.5V respectively; the output voltage parameter of the multiplier voltage module is set to be adjustable between 450V and 600V in intervals of 10V.

[0041] For the first communication machine, the modulation rate of the green light emitting unit is set to 125Mbps. According to the method provided by the present invention, the maximum amplitude and minimum amplitude of the communication voltage signal of the control module in the device 2# provided by the present invention that enable the signal processing module to work normally are set to 1.5V and 0.3V respectively; the working state of the color-changing glass is set to two gears, and the corresponding voltages are 0.1V and 1.5V respectively; the output voltage parameter of the voltage multiplier module is set to be adjustable between 450V and 600V in intervals of 10V.

[0042] The above system is used to build a file transfer system based on File Transfer Protocol (FTP) between computer 1# and computer 2#. Figure 3The wireless optical communication link is used for data transmission. The distance between the first communication machine and the second communication machine is changed within the range of 2.2m to 13.2m at intervals of 1m. By changing the distance, the power of the optical signal entering the first communication machine and the second communication machine changes. At each distance position, a compressed file with a file size of 1GB is first transmitted from computer 2# to computer 1#; then a compressed file with a file size of 1GB is transmitted from computer 1# to computer 2#, and the average rate of valid data is recorded. The test results are shown in Table 1. It can be seen that when the distance changes, the communication rate does not change. This shows that when the power of the optical signal entering the first communication machine and the second communication machine changes, the performance of the communication system is not affected, which verifies the effectiveness of the method provided by the present invention.

[0043] Table 1 Test results

[0044] In summary, the present invention proposes a method for receiving underwater wireless optical communications with a large dynamic power range. First, it innovatively proposes an underwater wireless communication receiving device comprising electrochromic glass, an adjustable voltage module, a photomultiplier tube, a voltage multiplier module, a transimpedance amplifier, a signal monitoring module, a control module, and a signal processing module. Based on the proposed underwater wireless communication receiving device, a corresponding method for receiving underwater wireless optical communications with a large dynamic power range is further proposed, and the feasibility of the method is verified through experiments. More specifically, the method has the following advantages: (1) Compared with the traditional method of changing the sensitivity of a photomultiplier tube by adjusting the voltage between the anode and cathode, the present invention adds electrochromic glass to the front end of the photomultiplier tube. In addition to adjusting the voltage between the anode and cathode of the photomultiplier tube to change its sensitivity, the transmittance of the communication optical signal can also be changed by adjusting the working voltage of the electrochromic glass, thereby further increasing the receiving optical power range of the receiver.

[0045] (2) The present invention uses electrochromic glass to change the transmittance of the device through an electrical control method, thereby further increasing the dynamic range of the receiver. Compared with traditional mechanical attenuators and MEMS attenuators, this method has higher precision, smaller size, and no wear; compared with polymer dispersed liquid crystals, it has lower insertion loss; compared with liquid crystal light valves, the field of view is not affected, which is conducive to increasing the field of view of the receiver.

[0046] (3) Compared with the traditional underwater wireless optical communication receiving device, the present invention only adds electrochromic glass at the hardware level, and only adds a control module for the working voltage of the photomultiplier tube and a control module for the working voltage of the electrochromic glass at the software level. It has a simple structure, strong portability, and is easy to promote and apply.

[0047] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0048] Although the present invention is described herein in conjunction with various embodiments, those skilled in the art may understand and implement other variations of the disclosed embodiments by reviewing the specification and accompanying drawings in the process of implementing the claimed invention. In the specification, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple components or steps. The fact that certain measures are described in different embodiments does not mean that these measures cannot be combined to produce good results.

[0049] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for receiving underwater wireless optical communication with a large dynamic power range, characterized in that: Applied to an underwater wireless communication receiving device including electrochromic glass, an adjustable voltage module, a photomultiplier tube, a voltage multiplier module, a transimpedance amplifier, a signal monitoring module, a control module, and a signal processing module, the corresponding method includes: S1. Setting the maximum amplitude and minimum amplitude of the communication voltage signal when the signal processing module is in normal operation in the control module; S2. Setting the output voltage parameters of the adjustable voltage module and the output voltage parameters of the voltage multiplier module in the control module in stages according to the transmittance variation range of the communication optical signal after passing through the electrochromic glass, the operating voltage range of the electrochromic glass, the operating voltage range of the photomultiplier tube, and the selected transimpedance amplifier; S3. Attenuating the received communication optical signal using electrochromic glass to obtain an attenuated communication optical signal; S4, using a photomultiplier tube to convert the attenuated communication light signal into a communication current signal; S5. Converting the communication current signal into a communication voltage signal using a transimpedance amplifier; S6. Measuring the amplitude of the communication voltage signal using a signal monitoring module; S7. The control module adjusts the output voltage parameters of the adjustable voltage module and the voltage multiplier module according to the amplitude of the communication voltage signal, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude; S8. The signal processing module restores the original communication data according to the communication voltage signal between the maximum amplitude and the minimum amplitude.

2. The underwater wireless optical communication large dynamic power range receiving method according to claim 1, characterized in that: In S2, the output voltage parameters of the adjustable voltage module and the voltage multiplier module are set in the control module in different levels according to the transmittance variation range of the communication optical signal after passing through the electrochromic glass, the operating voltage range of the electrochromic glass, and the selected transimpedance amplifier, including: S2-1. Select a parallel light with the same wavelength as the operating wavelength of the communication optical signal as a light source, and vertically direct the parallel light into an optical power meter to measure the optical power of the parallel light; S2-2. Directing the parallel light perpendicularly to the electrochromic glass and measuring the transmitted light power using an optical power meter; starting from the minimum operating voltage of the electrochromic glass, continuously increasing the operating voltage applied to the electrochromic glass at preset step intervals based on the operating voltage range of the electrochromic glass; and measuring the power value of the transmitted light after it stabilizes each time the operating voltage of the electrochromic glass changes; and calculating the transmittance of the electrochromic glass at different operating voltages based on the optical power of the parallel light and the stabilized power value after each change in the operating voltage of the electrochromic glass. S2-3. Comparing the transmittances of the electrochromic glass at different operating voltages to obtain a maximum transmittance and a minimum transmittance of the electrochromic glass, calculating a ratio between the maximum transmittance and the minimum transmittance, and using the ratio as a first ratio; S2-4. Generate a pseudo-random binary sequence using a bit error analyzer, modulate the parallel light to generate an analog optical signal, convert the analog optical signal into an analog voltage signal through a photomultiplier tube and a transimpedance amplifier, and input the analog voltage signal into the bit error analyzer for bit error rate testing; S2-5. Based on the bit error rate test results and the operating voltage range of the photomultiplier tube, obtain the maximum operating voltage applied between the anode and cathode of the photomultiplier tube and the simulated optical power corresponding to the maximum operating voltage, as well as the minimum operating voltage applied between the anode and cathode of the photomultiplier tube and the simulated optical power corresponding to the minimum operating voltage; S2-6. Calculate the ratio between the simulated optical power corresponding to the maximum operating voltage and the simulated optical power corresponding to the minimum operating voltage, and use the ratio as the second ratio; S2-7. Calculating the number of adjustable levels of the electrochromic glass according to the first ratio and the second ratio; S2-8. In the control module, a maximum output voltage parameter of the voltage multiplier module is set to the maximum operating voltage applied between the anode and cathode of the photomultiplier tube, and a minimum output voltage parameter is set to the minimum operating voltage applied between the anode and cathode of the photomultiplier tube, and multiple output voltage parameters are set between the minimum operating voltage and the maximum operating voltage according to a preset step interval; S2-9, in the control module, according to the adjustable number of gears, the second ratio, the maximum transmittance and the minimum transmittance, the transmittance is respectively 、 、 、……、 、 The corresponding voltage sets the output voltage parameters of the adjustable voltage module; is the maximum transmittance, is the minimum transmittance, N The number of gears can be adjusted in steps. b is the second ratio.

3. The underwater wireless optical communication large dynamic power range receiving method according to claim 2, characterized in that: The random binary sequence in S2-4 and the communication optical signal have the same modulation rate.

4. The underwater wireless optical communication large dynamic power range receiving method according to claim 2, characterized in that: In S2-5, based on the bit error rate test results and the operating voltage range of the photomultiplier tube, the maximum operating voltage applied between the anode and cathode of the photomultiplier tube and the simulated optical power corresponding to the maximum operating voltage, as well as the minimum operating voltage applied between the anode and cathode of the photomultiplier tube and the simulated optical power corresponding to the minimum operating voltage are obtained, including: S2-5-1. Based on the operating voltage range of the photomultiplier tube, starting from the minimum operating voltage of the photomultiplier tube, continuously increase the operating voltage applied between the anode and cathode of the photomultiplier tube at a preset step interval. After each increase in the operating voltage applied between the anode and cathode of the photomultiplier tube, control the power of the analog optical signal so that the amplitude of the analog voltage signal is equal to the average of the maximum amplitude and the minimum amplitude of the communication voltage signal when the signal processing module is in normal operation, and record the bit error rate measured by the bit error analyzer; S2-5-2. For each bit error rate measured by the bit error analyzer, the execution process includes: determining whether the bit error rate currently measured by the bit error analyzer reaches the bit error rate upper limit required by the underwater wireless communication receiving device; if not, recording the current operating voltage applied between the anode and cathode of the photomultiplier tube and the optical power of the analog optical signal corresponding to the operating voltage; S2-5-3. Select the largest working voltage from all recorded working voltages loaded between the anode and cathode of the photomultiplier tube as the maximum working voltage loaded between the anode and cathode of the photomultiplier tube and record it, select the smallest working voltage as the minimum working voltage loaded between the anode and cathode of the photomultiplier tube and record it, and at the same time record the simulated light power corresponding to the maximum working voltage and the simulated light power corresponding to the minimum working voltage.

5. The underwater wireless optical communication large dynamic power range receiving method according to claim 1, characterized in that: In S6, the amplitude of the communication voltage signal is measured by using a signal monitoring module, including: The communication voltage signal is measured according to a preset sampling period and sampling rate, and the maximum amplitude of all communication voltage signals measured within the sampling period is used as the amplitude of the communication voltage signal measured by the signal monitoring module.

6. The underwater wireless optical communication large dynamic power range receiving method according to claim 1, characterized in that: In S7, the control module adjusts the output voltage parameters of the adjustable voltage module and the voltage multiplier module according to the amplitude of the communication voltage signal so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude, including: When the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude, the output voltage parameters of the adjustable voltage module and the voltage multiplier module in the control module are kept unchanged; When the amplitude of the communication voltage signal is greater than the maximum amplitude, the control module reduces the transmittance of the electrochromic glass by changing the output voltage parameter of the adjustable voltage module, and reduces the output voltage of the multiplying voltage module by changing the output voltage parameter of the multiplying voltage module, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude; When the amplitude of the communication voltage signal is less than the minimum amplitude, the control module increases the transmittance of the electrochromic glass by changing the output voltage parameters of the adjustable voltage module, and changes the output voltage parameters of the multiplying voltage module to increase the output voltage of the multiplying voltage module, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude.

7. The underwater wireless optical communication large dynamic power range receiving method according to claim 6, characterized in that: When the amplitude of the communication voltage signal is greater than the maximum amplitude, the control module reduces the transmittance of the electrochromic glass by changing the output voltage parameter of the adjustable voltage module and reducing the output voltage of the multiplying voltage module by changing the output voltage parameter of the multiplying voltage module, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude, including: When the output voltage of the voltage multiplier module is at a preset minimum voltage and the amplitude of the communication voltage signal is greater than the maximum amplitude, the control module reduces the transmittance of the electrochromic glass by one level by changing the output voltage parameter of the adjustable voltage module. At this time, if the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude, the output voltage parameters of the adjustable voltage module and the voltage multiplier module in the control module are kept unchanged. If the amplitude of the communication voltage signal is still greater than the maximum amplitude, the control module reduces the transmittance of the electrochromic glass by another level by changing the output voltage parameter of the adjustable voltage module. At this time, if the amplitude of the communication voltage signal is less than the minimum amplitude, the control module increases the output voltage of the voltage multiplier module by changing the output voltage parameter of the voltage multiplier module, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude.

8. The underwater wireless optical communication large dynamic power range receiving method according to claim 6, characterized in that: When the amplitude of the communication voltage signal is greater than the maximum amplitude, the control module reduces the transmittance of the electrochromic glass by changing the output voltage parameter of the adjustable voltage module, and reduces the output voltage of the multiplying voltage module by changing the output voltage parameter of the multiplying voltage module, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude, and further includes: When the output voltage of the voltage multiplier module is at a preset minimum voltage, the transmittance of the electrochromic glass is the minimum transmittance, and the amplitude of the communication voltage signal is greater than the maximum amplitude, the output voltage parameters of the adjustable voltage module and the voltage multiplier module in the control module are kept unchanged, and the output result of the signal detection module, as well as the voltage information of the voltage multiplier module and the adjustable voltage module are fed back to the signal processing module.

9. The underwater wireless optical communication large dynamic power range receiving method according to claim 6, characterized in that: When the amplitude of the communication voltage signal is less than the minimum amplitude, the control module increases the transmittance of the electrochromic glass by changing the output voltage parameter of the adjustable voltage module and changes the output voltage parameter of the multiplying voltage module to increase the output voltage of the multiplying voltage module, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude, including: When the output voltage of the voltage multiplier module is at a preset maximum voltage and the amplitude of the communication voltage signal is less than the minimum amplitude, the control module increases the transmittance of the electrochromic glass by one level by changing the output voltage parameters of the adjustable voltage module. At this time, if the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude, the output voltage parameters of the adjustable voltage module and the voltage multiplier module in the control module are kept unchanged. If the amplitude of the communication voltage signal is still less than the minimum amplitude, the control module increases the transmittance of the electrochromic glass by another level by changing the output voltage parameters of the adjustable voltage module. At this time, if the amplitude of the communication voltage signal is greater than the maximum amplitude, the control module reduces the output voltage of the voltage multiplier module by changing the output voltage parameters of the voltage multiplier module, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude.

10. The underwater wireless optical communication large dynamic power range receiving method according to claim 6, characterized in that: When the amplitude of the communication voltage signal is less than the minimum amplitude, the control module increases the transmittance of the electrochromic glass by changing the output voltage parameter of the adjustable voltage module and changes the output voltage parameter of the multiplying voltage module to increase the output voltage of the multiplying voltage module, so that the amplitude of the communication voltage signal is between the maximum amplitude and the minimum amplitude, and further includes: When the output voltage of the voltage multiplier module is at a preset maximum voltage, the transmittance of the electrochromic glass is at the maximum transmittance, and the amplitude of the communication voltage signal is less than the minimum amplitude, the output voltage parameters of the adjustable voltage module and the voltage multiplier module in the control module are kept unchanged, and the output result of the signal detection module, as well as the voltage information of the voltage multiplier module and the adjustable voltage module are fed back to the signal processing module.

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