Underwater Wireless Optical Communication Receiving Method and Apparatus Based on Polymer Dispersed Liquid Crystals

Abstract

This invention discloses an underwater wireless optical communication receiving method and apparatus based on polymer-dispersed liquid crystal, relating to the field of underwater wireless communication technology. The method includes: collecting and receiving optical signals; perpendicularly incident the optical signals onto the optical surface of a polymer-dispersed liquid crystal device and allowing them to pass through; transmitting the optical signals through an interference optical filter; detecting the optical signals and converting them into voltage signals; analyzing the amplitude of the voltage signals to form a control voltage; applying the control voltage to the polymer-dispersed liquid crystal device to control the transmittance of the optical signals; and decoding the voltage signals to obtain communication data information. This invention achieves adjustment of the dynamic range of the wireless optical communication receiver by adjusting the voltage across the polymer-dispersed liquid crystal device. It features a simple structure, low complexity, fast adjustment response, and ease of widespread application. Compared with traditional liquid crystal attenuator methods, this invention eliminates the need for polarizers at both ends of the liquid crystal material, resulting in lower insertion loss and a larger field of view for optical signal reception.

Description

Technical Field

[0001] This invention belongs to the field of underwater wireless communication technology, and particularly relates to an underwater wireless optical communication receiving method and apparatus based on polymer-dispersed liquid crystal. Background Technology

[0002] In recent years, underwater wireless optical communication using blue-green light as the information carrier has attracted widespread attention both domestically and internationally due to its outstanding advantages such as high transmission rate, low latency, light weight, and low power consumption. Currently, combining this communication device with an underwater mobile platform to solve the problem of high-speed wireless data transmission in underwater special engineering applications has attracted widespread attention in the field of marine engineering and has become an important development direction in the field of marine communications.

[0003] In practical engineering applications, the transmission distance and water quality of the transmission link in a wireless optical communication system vary depending on the operating environment, leading to variations in the energy of the optical signal reaching the receiver. When the optical signal power is low, the receiver needs high detection sensitivity; when the receiver power is high, it needs to be able to adapt to these variations. Otherwise, if the power of the communication optical signal exceeds the rated operating range of the photodetector in the receiver, it may affect the accuracy of optical signal detection or even damage the photodetector. Therefore, to adapt to engineering applications, underwater wireless optical communication receivers need to have a large optical power reception range.

[0004] Chinese invention patent CN112737691A discloses an underwater wireless optical communication receiving method and device based on gain control within a detector. The method includes: S1: converting the received communication optical signal into a communication current signal using a photomultiplier tube; S2: converting the communication current signal into a communication voltage signal; S3: generating a DC voltage based on the communication voltage signal and using the DC voltage to control the internal gain of the photomultiplier tube, thereby controlling the amplitude of the communication voltage signal and increasing the received optical power range of the receiving device; wherein the communication voltage signal serves as the electrical signal for subsequent processing by the receiving device. This invention achieves the detection of signals with different optical power by controlling the internal gain of the photomultiplier tube with a DC voltage, increasing the received optical power range of the receiving device, and enabling rapid response to signals with different optical power.

[0005] The method proposed in the above invention can improve the dynamic detection range of the receiver to some extent, but it cannot identify potential saturation problems on the photosensitive surface of the detector. Under strong light, there is still a risk of damaging the communication receiver's detector.

[0006] In his paper "Research on Dynamic Control Technology in Underwater High-Speed ​​Blue-Green Laser Communication," Ning Jie of Beijing University of Posts and Telecommunications proposed another method to increase the received optical power range of underwater communication receivers. The specific method involves placing a variable attenuator in front of the photodetector inside the receiver. By adjusting the transmittance of the variable attenuator, the optical power reaching the photodetector is adjusted, allowing the detector to operate at its optimal state. Commonly used variable attenuators include mechanical optical attenuators, MEMS optical attenuators, and liquid crystal optical attenuators. Among them, a mechanical optical attenuator is generally an optical attenuator with different transmittance at different positions on its optical surface. During operation, changing the incident position of the received optical signal on the attenuator alters the optical power transmitted to the photodetector.

[0007] The methods described above are simple in principle and have a large attenuation range, but they are prone to wear, bulky, and have slow response speeds. MEMS-type optical attenuators replace the bulky stepper motors of traditional mechanical attenuators with electrostatic switching bridges, piezoelectric drives, etc., resulting in smaller size and lower cost, but their attenuation range is not as wide as traditional mechanical attenuators. Liquid crystal-type optical attenuators typically incorporate liquid crystal material between two polarizers with orthogonal or perpendicular polarization directions. Utilizing the optical anisotropy of liquid crystals, when an electric field is applied, the liquid crystal molecules reorient along the electric field direction, causing a change in transmission characteristics, thereby attenuating the optical power. The magnitude of the attenuation is related to the electric field strength applied to the liquid crystal. This type of attenuator is quite sensitive to the incident angle of the light wave, thus limiting the field of view of the receiving device, and the insertion loss of the device is relatively large. Summary of the Invention

[0008] The purpose of this invention is to provide an underwater wireless optical communication receiving method and device based on polymer-dispersed liquid crystal, which adjusts the dynamic range of the wireless optical communication receiver by adjusting the voltage across the polymer-dispersed liquid crystal device.

[0009] The objective of this invention can be achieved through the following technical solutions:

[0010] In a first aspect, embodiments of this application provide an underwater wireless optical communication receiving method based on polymer-dispersed liquid crystals, comprising the following steps:

[0011] S1: Collects and receives optical signals;

[0012] S2: The optical signal is incident perpendicularly onto the optical surface of the polymer-dispersed liquid crystal device and transmitted through it;

[0013] S3: Transmit the optical signal through an interference optical filter;

[0014] S4: Detect the transmitted light signal and convert the light signal into a voltage signal;

[0015] S5: Analyze the amplitude of the voltage signal to generate a control voltage;

[0016] S6: Apply the control voltage to the polymer-dispersed liquid crystal device to control the transmittance of the light signal;

[0017] S7: Decode the voltage signal to obtain communication data information.

[0018] As a preferred embodiment of the present invention, the polymer-dispersed liquid crystal device is voltage-controlled, and the scattering intensity distribution of perpendicularly incident light after passing through the polymer-dispersed liquid crystal device is controlled by changing the voltage between the electrodes.

[0019] As a preferred embodiment of the present invention, the optical surface of the interference optical filter is parallel to the optical surface of the polymer-dispersed liquid crystal device, and the transmission wavelength of the perpendicularly incident light is the same as the wavelength of the optical signal.

[0020] In a preferred embodiment of the present invention, in step S5, when the amplitude of the voltage signal is greater than the maximum value of the working voltage, the control voltage is reduced; when the amplitude of the voltage signal is less than the minimum value of the working voltage, the control voltage is increased; and when the amplitude of the voltage signal is within the range of the working voltage, the control voltage is kept constant.

[0021] As a preferred technical solution of the present invention, a decision circuit is used to recover the communication data information from the voltage signal.

[0022] Secondly, embodiments of this application provide an underwater wireless optical communication receiving device based on polymer-dispersed liquid crystal, comprising: a signal receiving module, a polymer-dispersed liquid crystal device, an interferometric optical filter, a photodetector, a transmittance control module, and a signal processing module connected in sequence.

[0023] The signal receiving module is used to collect and receive optical signals;

[0024] The polymer-dispersed liquid crystal device is used to control the scattering intensity distribution of vertically incident light after passing through the polymer-dispersed liquid crystal device by changing the voltage between the electrodes; it includes two glass plates coated with transparent conductive electrodes, and polymer-dispersed liquid crystal injected between the glass plates.

[0025] The interference optical filter is used to match the transmission wavelength of the vertically incident light with the spectrum of the optical signal so that the two wavelengths are the same; its optical surface is parallel to the optical surface of the polymer-dispersed liquid crystal device.

[0026] The photodetector is used to convert the optical signal into a voltage signal.

[0027] The transmittance control module is used to analyze the amplitude of the voltage signal and generate a control voltage.

[0028] The signal processing module is used to decode the voltage signal to obtain communication data information.

[0029] As a preferred embodiment of the present invention, the transmittance control module and the signal processing module are constructed using FPGA and FPGA peripheral hardware circuits.

[0030] As a preferred embodiment of the present invention, the signal processing module uses equalization and filtering methods to shape and process the voltage signal; and recovers the communication data information through clock extraction, decision circuit and decoding circuit.

[0031] As a preferred embodiment of the present invention, smart dimming glass is selected as the polymer-dispersed liquid crystal device; and a photomultiplier tube device is selected as the photodetector.

[0032] The beneficial effects of this invention are as follows:

[0033] (1) The present invention achieves the adjustment of the dynamic range of the wireless optical communication receiver by adjusting the voltage across the polymer dispersed liquid crystal device.

[0034] (2) The present invention has a simple structure, low complexity, fast adjustment response, and is easy to promote and apply.

[0035] (3) Compared with the traditional liquid crystal attenuator method, the present invention does not require adding polarizers at both ends of the liquid crystal material, resulting in low device insertion loss and a large field of view for receiving optical signals. Attached Figure Description

[0036] To better understand and implement this application, the technical solution is described in detail below with reference to the accompanying drawings.

[0037] Figure 1 A flowchart illustrating the steps of an underwater wireless optical communication receiving method based on polymer-dispersed liquid crystal, provided in this application embodiment;

[0038] Figure 2 This is a schematic diagram illustrating the working principle of the polymer-dispersed liquid crystal device provided in the embodiments of this application;

[0039] Figure 3 This is a schematic diagram illustrating the working principle of the interferometric optical filter provided in the embodiments of this application;

[0040] Figure 4 A schematic diagram of an underwater wireless optical communication receiving device based on polymer-dispersed liquid crystal is provided for an embodiment of this application;

[0041] Figure 5 A schematic diagram of a simulation experimental device for an underwater wireless optical communication receiving method based on polymer-dispersed liquid crystal, provided for an embodiment of this application;

[0042] Figure 6 A flowchart illustrating the steps of an underwater wireless optical communication receiving method based on an underwater wireless optical communication receiving device, as provided in this application embodiment;

[0043] Icons: 1-Receiver module; 2-Polymer-dispersed liquid crystal device; 3-Interferometric optical filter; 4-Photodetector; 5-Transmittance control module; 6-Signal processing module. Detailed Implementation

[0044] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, exemplary embodiments will be described in detail below, examples of which are illustrated in the accompanying drawings. In the following description relating to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of methods and systems consistent with some aspects of this application as detailed in the appended claims.

[0045] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. As used in this application and the appended claims, the singular forms "a," "an," "the," and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0046] The following detailed description of the specific implementation methods, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided in detail.

[0047] Example 1

[0048] like Figure 1 As shown, this embodiment of the invention provides an underwater wireless optical communication receiving method based on polymer-dispersed liquid crystals, specifically including the following steps:

[0049] S101: Collects and receives optical signals;

[0050] S102: The optical signal is incident perpendicularly onto the optical surface of the polymer-dispersed liquid crystal device and transmitted through it;

[0051] S103: Transmits optical signals through an interference optical filter;

[0052] S104: Detects the transmitted light signal and converts the light signal into a voltage signal;

[0053] S105: Analyze the amplitude of the voltage signal to generate the control voltage;

[0054] S106: Apply a control voltage to the polymer-dispersed liquid crystal device to control the transmittance of the light signal;

[0055] S107: Decodes the voltage signal to obtain communication data information.

[0056] Specifically, this invention utilizes an optical receiving module to receive an optical signal, and then uses a voltage-controlled polymer-dispersed liquid crystal device to process the optical signal received in step S101, so that the optical signal is incident perpendicularly on the optical surface of the polymer-dispersed liquid crystal device and passes through the optical surface; then, an interference optical filter is used to make the optical signal in step S102 pass through the optical surface of the interference optical filter; a photodetector is used to detect the transmitted optical signal in step S103, so that the optical signal is converted into a voltage signal; then, a transmittance control module is used to analyze the amplitude of the voltage signal in step S104, thereby forming a control voltage; the control voltage formed in step S105 is applied to the polymer-dispersed liquid crystal device in step S102 to control the transmittance of the optical signal; finally, the voltage signal is decoded to obtain communication data information.

[0057] In this embodiment of the invention, the optical signal is also called the communication optical signal, and the voltage signal is also called the communication voltage signal.

[0058] In one embodiment of the present invention, the polymer-dispersed liquid crystal device includes two glass plates coated with transparent conductive electrodes, and polymer-dispersed liquid crystal injected between the glass plates.

[0059] In another embodiment of the present invention, the polymer-dispersed liquid crystal device is voltage-controlled, and the scattering intensity distribution of perpendicularly incident light after passing through the polymer-dispersed liquid crystal device is controlled by changing the voltage between the electrodes.

[0060] Specifically, the polymer-dispersed liquid crystal device consists of two glass plates coated with transparent conductive electrodes, and polymer-dispersed liquid crystal injected between the glass plates. This structure controls the scattering intensity distribution of perpendicularly incident light after passing through the polymer-dispersed liquid crystal device by changing the voltage between the electrodes.

[0061] In one embodiment of the present invention, the optical surface of the interference optical filter is parallel to the optical surface of the polymer-dispersed liquid crystal device, and the transmission wavelength of the perpendicularly incident light is the same as the wavelength of the optical signal.

[0062] Specifically, the function of polymer-dispersed liquid crystals is to control the distribution of light emission angles. When the light emission angles are relatively dispersed, the transmittance of light passing through the interference filter will change significantly. Therefore, when the optical surfaces of the interference optical filter and the polymer-dispersed liquid crystal device are parallel, as much normally incident light signal as possible will pass through the optical surfaces.

[0063] Furthermore, because the transmission wavelength of perpendicularly incident light through an interference optical filter is equal to the wavelength of the optical signal, allowing a consistent optical signal to pass through, it also allows more normally incident light signals to pass through the optical surface. If the incident angle of the optical signal entering the interference filter increases, the power of the transmitted light will decrease because the central transmission wavelength of the interference filter changes.

[0064] In one embodiment of the present invention, in step S105, when the amplitude of the voltage signal is greater than the maximum value of the working voltage, the control voltage is reduced; when the amplitude of the voltage signal is less than the minimum value of the working voltage, the control voltage is increased; when the amplitude of the voltage signal is within the range of the working voltage, the control voltage is kept constant.

[0065] Specifically, when the voltage applied to the polymer-dispersed liquid crystal is high, the incident angle of more transmitted light relative to the interference filter is relatively small, resulting in a higher transmitted light signal power and a larger voltage signal amplitude after photoelectric conversion. Conversely, when the voltage applied to the polymer-dispersed liquid crystal is low, the incident angle of more transmitted light relative to the interference filter is relatively large, resulting in a lower transmitted light signal power and a smaller voltage signal amplitude after photoelectric conversion.

[0066] In one embodiment of the present invention, in step S104, a photodetector is used to detect the optical signal.

[0067] Specifically, the principle of a photodetector is to convert light signals into electrical signals. Photodetectors have wide applications in various fields of military and national economy. In the visible or near-infrared band, they are mainly used for radiation measurement and detection, industrial automatic control, photometric measurement, etc.; in the infrared band, they are mainly used for missile guidance, infrared thermal imaging, infrared remote sensing, etc.

[0068] In this embodiment of the invention, a photodetector is used to convert communication optical signals into communication voltage signals.

[0069] The following section will explain the working principle of the underwater wireless optical communication receiving method based on polymer-dispersed liquid crystals.

[0070] Polymer-dispersed liquid crystals are formed by dispersing liquid crystals in the form of microparticles within a polymer matrix using a certain method. The liquid crystal microparticles are separated from each other, while the polymer forms a continuous phase.

[0071] like Figure 2 As shown in the figure, the present invention provides the working principle of a polymer-dispersed liquid crystal device. The working principle is as follows: polymer-dispersed liquid crystal is injected between two glass plates coated with transparent conductive electrodes, and through a processing method, it is formed into a film, thereby obtaining a simple optical device.

[0072] When no external electric field is applied, liquid crystal particles with positive dielectric anisotropy are randomly distributed in the polymer material, and all liquid crystal particles are in a free orientation state. At this time, because the refractive index of the liquid crystal is mismatched with that of the polymer, the particles scatter light strongly, and the optical device appears opaque or semi-transparent milky white, with low transmittance of vertical light signals.

[0073] When an external electric field is applied, due to the positive dielectric anisotropy, the director of the liquid crystal particles will align along the direction of the external electric field. If the refractive index of the liquid crystal matches the refractive index of the polymer, light can pass through.

[0074] Obviously, the degree of scattering of incident light by polymer-dispersed liquid crystal devices will vary depending on the applied electric field strength. Therefore, when different DC voltages are applied to the two ends of a polymer-dispersed liquid crystal device, the attenuation of the light signal in the incident direction will be different.

[0075] like Figure 3 As shown, this embodiment of the invention provides the working principle of an interferometric optical filter. Its working principle is as follows: Interferometric optical filters are manufactured based on the principle of multi-beam interference and are generally composed of multiple optical thin films. Their optical path working principle can be explained by multi-beam interference within a single-layer film. For example... Figure 3 As shown, when the incident light undergoes multiple reflections and refractions between "surface 1#" and "surface 2#", the phase delay δ between two adjacent light rays can be expressed by formula (1):

[0076] , formula (1)

[0077] , formula (2)

[0078] In formula (2) n and n 1 represents the refractive index inside and outside the optical thin film, respectively. β 0 and β These are the angle of incidence and the angle of refraction, respectively; in formula (1) λLet λ be the wavelength of the light wave, and h be the distance between "surface 1#" and "surface 2#". The light field after passing through the optical thin film... E He Guangqiang I Respectively expressed as:

[0079] , formula (3)

[0080] , formula (4)

[0081] In formula (3) E 0 and δ 0 represents the amplitude and phase of the incident light. t 1 and t 2 is the Fresnel projection coefficient. r 1 and r 2 is the Fresnel reflectance coefficient. l It can take any integer value. j It is an imaginary number.

[0082] Therefore, the wavelength of the transmitted light signal changes depending on the angle of the incident light. Generally, the larger the angle of incident light, the smaller the operating wavelength of the transmission center of the interference optical filter. Consequently, the scattered light generated after the beam passes through the polymer-dispersed liquid crystal device, because its wavelength is generally in the blue-green light band and its incident angle when entering the interference filter is relatively large, generally makes it difficult to pass through. This can further improve the power detection range of the receiving system.

[0083] See Figure 2 and Figure 3 Combining the working principles of polymer-dispersed liquid crystal devices and interference optical filters, this invention can adjust the transmittance of the optical system by changing the control voltage of the polymer-dispersed liquid crystal device, thereby achieving automatic adaptation to the power of underwater wireless optical communication signals.

[0084] This invention adjusts the dynamic range of a wireless optical communication receiver by regulating the voltage across a polymer-dispersed liquid crystal device. The device provided by this invention has a simple structure, low complexity, fast adjustment response, and is easy to promote and apply.

[0085] The underwater wireless optical communication receiving method and device based on polymer-dispersed liquid crystal provided by this invention, compared with the traditional liquid crystal attenuator method, does not require adding polarizers at both ends of the liquid crystal material, and has the beneficial effects of low device insertion loss and large receiving field of view of optical signal.

[0086] Example 2

[0087] like Figure 4As shown, this embodiment of the invention provides an underwater wireless optical communication receiving device based on polymer-dispersed liquid crystal, comprising: a signal receiving module 1, a polymer-dispersed liquid crystal device 2, an interference optical filter 3, a photodetector 4, a transmittance control module 5, and a signal processing module 6 connected in sequence.

[0088] Signal receiving module 1: Used to collect and receive optical signals;

[0089] Polymer-dispersed liquid crystal device 2: used to control the scattering intensity distribution of vertically incident light after passing through the polymer-dispersed liquid crystal device 2 by changing the voltage between the electrodes; it includes two glass plates coated with transparent conductive electrodes, and polymer-dispersed liquid crystal injected between the glass plates.

[0090] Interference optical filter 3: used to match the transmission wavelength of perpendicularly incident light with the spectrum of the optical signal; its optical surface is parallel to the optical surface of the polymer-dispersed liquid crystal device 2;

[0091] Photodetector 4: Used to convert optical signals into voltage signals;

[0092] Transmittance control module 5; used to analyze the amplitude of the voltage signal and generate a control voltage;

[0093] Signal processing module 6 is used to decode voltage signals to obtain communication data information.

[0094] In this embodiment of the invention, regarding the transmittance control module 5, when the voltage signal amplitude is greater than the maximum value of the working voltage, the control voltage is reduced; when the voltage signal amplitude is less than the minimum value of the working voltage, the control voltage is increased; when the voltage signal amplitude is within the working voltage range, the control voltage is kept constant.

[0095] In one embodiment of the present invention, optionally, the transmittance control module 5 and the signal processing module 6 are constructed using an FPGA and its peripheral hardware circuitry. An FPGA is also known as a Field-Programmable Gate Array.

[0096] In this embodiment of the invention, the FPGA adopts the concept of a Logic Cell Array (LCA), which internally includes three parts: Configurable Logic Blocks (CLBs), Input Output Blocks (IOBs), and interconnects. Field-Programmable Gate Arrays (FPGAs) are programmable devices, and compared to traditional logic circuits and gate arrays (such as PALs, GALs, and CPLDs), FPGAs have a different structure. FPGAs utilize small lookup tables (16×1 RAM) to implement combinational logic. Each lookup table is connected to the input of a D flip-flop, which then drives other logic circuits or I / O. This constitutes a basic logic cell module that can implement both combinational and sequential logic functions. These modules are interconnected or connected to I / O modules via metal interconnects. The logic of an FPGA is implemented by loading programming data into its internal static memory cells. The values ​​stored in the memory cells determine the logic function of the logic cells and the connection methods between modules or between modules and I / O, and ultimately determine the functions that the FPGA can implement. FPGAs allow unlimited programming.

[0097] In this embodiment of the invention, the FPGA chip has the characteristics of improving system integration and reliability, and can be reused repeatedly and used flexibly.

[0098] In one embodiment of the present invention, the signal processing module 6 uses equalization and filtering methods to shape and process the voltage signal; and recovers the communication data information through clock extraction, decision circuit and decoding circuit.

[0099] In an embodiment of the present invention, the receiving module 1 can be a corresponding module in a current underwater communication receiver; the signal processing module 6 can be a corresponding module in a current underwater communication receiver, mainly using equalization and filtering methods to shape and process the communication voltage signal, and finally recovering the information of the transmitting end through clock extraction, decision circuit and decoding circuit.

[0100] In one embodiment of the present invention, smart dimming glass is selected as polymer-dispersed liquid crystal device 2; and photomultiplier tube device is selected as photodetector 4.

[0101] Specifically, smart dimming glass consists of two layers of glass with a liquid crystal film (commonly known as a dimming film, LC film) sandwiched between them. The liquid crystal film is covered by a PVB film in the center, and then bonded together in an autoclave or a conventional one-step furnace under high temperature and pressure. In this embodiment of the invention, smart dimming glass not only has privacy protection functions but also possesses all the application characteristics of safety glass.

[0102] The working principle of smart dimming glass is as follows: When the power is turned off, the liquid crystal molecules inside the electronically controlled dimming glass will be irregularly dispersed, and the electronically controlled glass will appear to be transparent but not transparent; when the power is turned on, the liquid crystal molecules inside will be neatly arranged, and light can pass through freely, and the dimming glass will instantly become transparent.

[0103] Based on the characteristics and working principle of the aforementioned smart dimming glass, in this embodiment of the invention, combined with... Figure 2 Intelligent dimming glass can accurately reflect the different states of microparticle liquid crystals when no electric field is applied and when an electric field is applied.

[0104] A photomultiplier tube (PMT) is a vacuum electronic device that converts weak light signals into electrical signals. PMTs are used in optical measuring instruments and spectroscopic analysis instruments, where they can measure extremely weak radiant power at wavelengths of 200–1200 nanometers in low-energy photometry and spectroscopy.

[0105] The working principle of a photomultiplier tube (PMT) is as follows: Based on the external photoelectric effect, secondary electron emission, and electron optics theories, the PMT combines high gain, low noise, high frequency response, and a large signal receiving area. It is a photosensitive vacuum electronic device with extremely high sensitivity and ultrafast time response, capable of operating in the ultraviolet, visible, and near-infrared spectral regions. Solar-blind ultraviolet PMTs are insensitive to visible light and near-ultraviolet spectral radiation outside the solar-blind ultraviolet region, and feature low noise (dark current less than 1 nA), fast response, and a large receiving area.

[0106] In this embodiment of the invention, combining the characteristics and working principle of the photomultiplier tube described above, the photomultiplier tube can quickly and accurately convert optical signals that match the spectrum into electrical signals.

[0107] The underwater wireless optical communication receiver based on polymer-dispersed liquid crystal provided in this invention adjusts the dynamic range of the wireless optical communication receiver by regulating the voltage across the polymer-dispersed liquid crystal device 2. It features a simple structure, low complexity, fast adjustment response, and ease of widespread application. Compared to traditional liquid crystal attenuator methods, it eliminates the need for polarizers at both ends of the liquid crystal material, resulting in lower insertion loss and a larger field of view for receiving optical signals.

[0108] Example 3

[0109] Furthermore, the present invention provides a simulation experiment based on the above-described underwater wireless optical communication receiving method and apparatus based on polymer-dispersed liquid crystals, the specific details of which are as follows:

[0110] like Figure 5As shown in the figure, this embodiment of the invention provides a simulation experimental device for an underwater wireless optical communication receiving method based on polymer-dispersed liquid crystals, as illustrated in the figure:

[0111] First, a pseudo-random binary sequence (PRBS) is generated using a bit error rate analyzer to simulate communication data. This PRBS sequence is then used to control the optical signal output by the blue-green optical communication transmitter. The modulation format of the optical signal is on-off keying (OOK): when the PRBS sequence is logic "1", the communication transmitter outputs an optical signal; when the PRBS sequence is logic "0", the communication transmitter does not output an optical signal. Therefore, the presence or absence of an optical signal can characterize the communication data. In this embodiment, the light source used is a blue light band laser diode with a center wavelength of 450nm and a linewidth of 10nm. The electrical signal output by the bit error rate analyzer is converted into an optical signal through direct modulation. This optical signal serves as the communication optical signal that the optical communication receiver needs to receive.

[0112] Then, the communication optical signal passes through a water tank and an adjustable attenuator before reaching the optical communication receiver. The water tank simulates the transmission of light in water, and the adjustable attenuator simulates the power variation of the optical signal arriving at the optical communication receiver.

[0113] Finally, the optical communication receiver performs photoelectric detection on the communication optical signal, uses a decision circuit to recover the original communication data information, i.e., logic "1" and logic "0", from the voltage signal after photoelectric conversion, and then uses a bit error rate meter to compare the received logic data with the transmitted logic data one by one to test the bit error rate of the communication system.

[0114] The optical communication receiver is the underwater wireless optical communication receiving device described in the above embodiment, comprising: a receiving module 1, a polymer dispersed liquid crystal device 2, an interference optical filter 3, a photodetector 4, a transmittance control module 5, and a signal processing module 6.

[0115] The underwater wireless optical communication receiving device described above has been described in detail in Embodiment 2 of the present invention, so it will not be repeated here.

[0116] like Figure 6 As shown, the present invention is based on the above. Figure 5 The underwater wireless optical communication receiving device shown provides an underwater wireless optical communication receiving method, which specifically includes the following steps:

[0117] S601: Receiver module 1 receives optical signals passing through the water tank and the variable attenuator;

[0118] S602: The light signal from step S601 is vertically irradiated onto the surface of the polymer-dispersed liquid crystal device 2 and transmitted through;

[0119] In this embodiment, commonly used smart dimming glass is selected as the polymer-dispersed liquid crystal device 2.

[0120] S603: The light signal in step S602 is transmitted through by using the interference optical filter 3, and the optical surface of the interference optical filter 3 is parallel to the optical surface of the polymer dispersed liquid crystal device 2.

[0121] In this embodiment, the interference optical filter 3 has a center transmission wavelength of 450nm and a bandwidth of 30nm for vertically incident light, which can match the wavelength of communication light.

[0122] S604: Use photodetector 4 to detect the light signal projected in step S603 and convert it into a voltage signal;

[0123] In this embodiment, a photomultiplier tube is used as the photodetector 4.

[0124] S605: The transmittance control module 5 monitors the amplitude of the voltage signal output in step S604 and forms a control voltage.

[0125] In this embodiment, when the voltage signal amplitude is greater than the maximum value of the communication operating voltage, the control voltage is reduced; when the voltage signal amplitude is less than the minimum value of the communication operating voltage, the control voltage is increased; when the voltage signal amplitude is within the range of the communication operating voltage, the control voltage remains unchanged.

[0126] In this embodiment, the transmittance control module 5 is built using an FPGA and its peripheral hardware circuitry.

[0127] S606: Apply the control voltage generated in step S605 to the polymer-dispersed liquid crystal device 2;

[0128] S607: Signal processing module 6 uses a decision circuit to recover the original communication data information from the voltage signal after photoelectric conversion.

[0129] In the specific experiment, the signal rate output by the bit error rate analyzer was set to 20 Mbps, and the input voltage of the signal processing module 6 was set to 0.8V~1.5V, which is the rated operating range of the optical communication receiver. The optical power reaching the optical communication receiver was controlled by a variable attenuator. The bit error rate was calculated in 1-minute intervals. After a large number of tests, the test results are shown in Table 1 below:

[0130]

[0131] Table 1. Simulation Experiment Test Results

[0132] As shown in Table 1, a high-dynamic-range underwater wireless optical communication receiving method based on polymer-dispersed liquid crystals enables the optical communication receiver to adapt to different optical powers, including optical signal power variations within the range of 0.003mW to 0.03mW, with a power adaptive range of 10dB. This experimental result verifies the effectiveness of the invention and provides strong evidence for its practical application.

[0133] It should be noted that, in this document, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0134] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional modules is merely an example. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. The functional modules in the embodiments can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module. The integrated modules can be implemented in hardware or as software functional modules. Furthermore, the specific names of the functional modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0135] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0136] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0137] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. An underwater wireless optical communication receiving device based on polymer-dispersed liquid crystal, characterized in that: include: The signal receiving module, polymer-dispersed liquid crystal device, interference optical filter, photodetector, transmittance control module, and signal processing module are connected in sequence via communication. The signal receiving module is used to collect and receive optical signals; The polymer-dispersed liquid crystal device is used to control the scattering intensity distribution of vertically incident light after passing through the polymer-dispersed liquid crystal device by changing the voltage between the electrodes; it includes two glass plates coated with transparent conductive electrodes, and polymer-dispersed liquid crystal injected between the glass plates. The interference optical filter is used to match the transmission wavelength of the vertically incident light with the spectrum of the optical signal so that the two wavelengths are the same; its optical surface is parallel to the optical surface of the polymer-dispersed liquid crystal device. The photodetector is used to convert the optical signal into a voltage signal. The transmittance control module is used to analyze the amplitude of the voltage signal and generate a control voltage. The signal processing module is used to decode the voltage signal to obtain communication data information. Intelligent dimming glass is selected as the polymer-dispersed liquid crystal device; a photomultiplier tube is selected as the photodetector. The specific method employed by the device includes the following steps: S1: Collects and receives optical signals; S2: The optical signal is incident perpendicularly onto the optical surface of the polymer-dispersed liquid crystal device and transmitted through it; S3: Transmit the optical signal through an interference optical filter; S4: Detect the transmitted light signal and convert the light signal into a voltage signal; S5: Analyze the amplitude of the voltage signal to generate a control voltage; S6: Apply the control voltage to the polymer-dispersed liquid crystal device to control the transmittance of the light signal; S7: Decode the voltage signal to obtain communication data information; The polymer-dispersed liquid crystal device is voltage-controlled, and the scattering intensity distribution of perpendicularly incident light after passing through the polymer-dispersed liquid crystal device is controlled by changing the voltage between the electrodes. The optical surface of the interference optical filter is parallel to the optical surface of the polymer-dispersed liquid crystal device, and the transmission wavelength of the perpendicularly incident light is the same as the wavelength of the optical signal.

2. The underwater wireless optical communication receiving device based on polymer-dispersed liquid crystal according to claim 1, characterized in that: In step S5, when the amplitude of the voltage signal is greater than the maximum value of the operating voltage, the control voltage is reduced; when the amplitude of the voltage signal is less than the minimum value of the operating voltage, the control voltage is increased; when the amplitude of the voltage signal is within the range of the operating voltage, the control voltage is kept constant.

3. The underwater wireless optical communication receiving device based on polymer-dispersed liquid crystal according to claim 1, characterized in that: The transmittance control module and the signal processing module are built using FPGA and FPGA peripheral hardware circuits.

4. The underwater wireless optical communication receiving device based on polymer-dispersed liquid crystal according to claim 1, characterized in that: The signal processing module uses equalization and filtering methods to shape and process the voltage signal; and recovers the communication data information through clock extraction, decision circuit, and decoding circuit.

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