CN110932778A - Underwater remote photon counting communication system and method - Google Patents

Underwater remote photon counting communication system and method Download PDF

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Publication number
CN110932778A
CN110932778A CN201911124501.XA CN201911124501A CN110932778A CN 110932778 A CN110932778 A CN 110932778A CN 201911124501 A CN201911124501 A CN 201911124501A CN 110932778 A CN110932778 A CN 110932778A
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China
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communication
detector
tracking
light
pointing mechanism
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张亮
闻冠华
黄骏
王建宇
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Shanghai Institute of Technical Physics of CAS
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Shanghai Institute of Technical Physics of CAS
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B10/00Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/11Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B10/00Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50Transmitters
    • H04B10/501Structural aspects
    • H04B10/503Laser transmitters
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B10/00Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50Transmitters
    • H04B10/508Pulse generation, e.g. generation of solitons
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B10/00Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50Transmitters
    • H04B10/516Details of coding or modulation
    • H04B10/524Pulse modulation
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B10/00Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/60Receivers
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B13/00Transmission systems characterised by the medium used for transmission, not provided for in groups H04B3/00 - H04B11/00
    • H04B13/02Transmission systems in which the medium consists of the earth or a large mass of water thereon, e.g. earth telegraphy

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Electromagnetism (AREA)
  • Optics & Photonics (AREA)
  • Optical Communication System (AREA)

Abstract

The invention discloses an underwater long-distance photon counting communication system and method. The system consists of a watertight shell with a glass window and an internal communication unit, the capture tracking technology and the single photon detection communication technology are combined, the communication light is simultaneously used as beacon light, and the directional optical communication method is realized by reducing the communication divergence angle and improving the communication sensitivity. Compared with the conventional omnidirectional optical communication, the underwater communication method can greatly improve the underwater communication distance, and is particularly suitable for long-distance high-speed communication and networking among deep-sea underwater detection nodes.

Description

Underwater remote photon counting communication system and method
Technical Field
The invention relates to a laser communication technology, in particular to an underwater photon counting communication system and method, which can be applied to deep-sea underwater remote communication.
Background art:
the ocean accounts for about 71% of the earth's surface area, with an average water depth of about 3795 meters. The vast ocean has novel energy sources such as tide, wind power, sunlight, geothermal heat and the like, and also has important resources such as marine organisms, petroleum, natural gas, rare metal mineral reserves and the like, and has huge scientific exploration value and industrial economic benefit. The ocean information system is a key technology for ocean resource development and utilization, and various large ocean information system construction projects such as an European seabed observation data network (EMODNET), a Japanese earthquake and tsunami seabed detection network (DONET), a American digital ocean Internet of things and the like are introduced internationally.
The reliable communication means is a core link in a marine information system, and the current underwater communication technology is mainly divided into four types, namely optical fiber wired communication, electromagnetic wave wireless communication, underwater sound wireless communication and light wave wireless communication. In the aspect of wireless communication, electromagnetic wave communication is large in size, high in power, low in communication speed and short in communication distance, and is only suitable for one-way instruction type data transmission. The underwater acoustic communication technology is mature, can be transmitted for dozens of kilometers underwater, but has the communication speed of only kbps, prolonged transmission time, heavy volume and large power consumption. The underwater wireless optical communication utilizes blue-green laser to transmit information, has higher channel transmission transmittance, can achieve the highest communication speed and extremely low communication delay, and has wide prospect in the aspects of underwater sensor networking, underwater diver communication, underwater robot operation and underwater high-speed communication. The existing underwater wireless optical communication is mainly omnidirectional communication, and a conventional detector is adopted, so that the communication sensitivity is low. Although systems can reach Gbps, the transmission distance is only a few m, and the system is not suitable for long-distance node networking. The farthest communication distance realized by the existing underwater optical communication system does not exceed 250m, and the application range of optical communication is limited.
The photon counting communication technology has been successfully tested and verified in the field of deep space communication, can realize the communication sensitivity of sub-photons/bits, and is an effective technology for solving high-speed data transmission in an ultra-large loss link. The signal loss of underwater remote optical communication is very large, and the communication distance can be greatly improved by applying a photon counting communication technology.
The invention content is as follows:
the invention aims to solve the problem that the conventional underwater optical communication is short in communication distance, combine a photon counting communication technology with a capturing and tracking technology, realize a high-sensitivity communication system and method based on a narrow signal divergence angle, and greatly improve the communication distance compared with the conventional omnidirectional optical communication.
The structure of the system is shown in the attached figure 1, and the system comprises a watertight shell 1, a tracking and pointing mechanism 2, a turning mirror assembly 3, an optical receiving antenna 4, a color separation sheet 5, a light separation sheet 6, a communication laser 7, a single photon detector 8, a high-sensitivity area array detector 9 and control electronics 10.
The watertight shell 1 is provided with a light-transmitting glass window, and the glass window is opposite to the tracking and pointing mechanism 2; the tracking and pointing mechanism 2 is a two-dimensional pointing mirror mechanism; the optical receiving antenna 4 is a transmissive or reflective optical focusing element; the communication laser 7 adopts a blue-green wave band, and the wavelength is 400nm to 532 nm; the light splitting sheet 6 divides the communication signals into two paths, and the intensity proportion of the two paths of signals can be adjusted; the high-sensitivity area array detector 9 adopts a CMOS or CCD detector.
The other components are sealed in the shell by the watertight shell 1, and received signal light passes through a glass window of the watertight shell 1, then is projected by the tracking and pointing mechanism 2, the turning mirror component 3, the optical receiving antenna 4 and the color separation sheet 5, and then respectively enters the single photon detector 8 and the high-sensitivity area array detector 9 by the light separation sheet 6 according to a certain proportion. The emission signal light is emitted by the communication laser 7, reflected by the color separation sheet 5, and emitted to the outside of the system after passing through other components. The control electronics 10 is electrically connected with the tracking and pointing mechanism 2, the single photon detector 8 and the high-sensitivity area array detector 9.
The communication scheme of the system is as follows:
communication needs to take place between the two described systems, named A, B. The two system communication lasers 7 have different wavelengths, and the communication light of the opposite side is respectively introduced into the single photon detector 8 and the high-sensitivity area array detector 9 through the wavelength selection of the color separation sheet 5.
When communication starts, the system A controls the tracking pointing mechanism 2 to deflect, and transmits a communication signal to the position near the position B to perform small-range scanning. And the system B also controls the tracking and pointing mechanism 2 to deflect, aligns the view field of the high-sensitivity area array detector 9 with the system A, and records the angle information of the tracking and pointing mechanism 2 at the moment to position the tracking and pointing mechanism when the detector detects a signal from the opposite side. At this time, the communication signals emitted by the A, B can be detected by the opposite high-sensitivity detector 9, and form closed-loop control with the tracking and pointing mechanism 2, so that the signal light spots are stabilized to the center of the detector field of view. At this time, the signal light enters the single photon detector 8.
The information transmitting terminal adopts a pulse position modulation and serial cascade channel coding method. The single photon detector 8 at the receiving end converts the single photon level light pulse into an electrical signal, sends the electrical signal to the control electronics 10, and decodes and demodulates the electrical signal according to the agreed coding and modulation method to restore the original data.
The invention has the following beneficial effects:
and a photon counting communication system of a single photon detector is adopted, so that the communication sensitivity is greatly improved. And a directional communication mode based on a narrow laser divergence angle and a tracking system is adopted, so that the emission gain is improved. The combination of the two can improve the communication distance to more than 500m compared with the conventional omnidirectional wireless optical communication.
Description of the drawings:
fig. 1 is a schematic diagram of the system.
Reference numbers in the figures: the device comprises a watertight shell 1, a tracking and pointing mechanism 2, a turning mirror assembly 3, an optical receiving antenna 4, a color separation sheet 5, a light separation sheet 6, a communication laser 7, a single photon detector 8, a high-sensitivity area array detector 9 and control electronics 10. The dashed line in fig. 1 is the light path.
The specific implementation mode is as follows:
the following describes embodiments of the present invention in further detail with reference to the accompanying drawings. Taking a deep sea underwater long-distance communication as an example, the communication needs to be carried out between two terminals, and each terminal needs to be provided with the system. The terminal distance is 500m, and the communication speed is 1 Mbps.
The two terminals may be designated A, B and have substantially identical parameters except for different transmit and receive wavelengths.
A terminal A:
the wavelength of the transmitted communication light is 490nm, and the receiving wavelength is 450 nm. The diameter of a glass window of the watertight shell 1 is 60mm, an organic glass material is adopted, and a metal shell is made of a titanium alloy material; the tracking and pointing mechanism 2 adopts a permanent magnet synchronous motor as an actuating mechanism, the swing range is +/-15 degrees, and the optical deflection angle of +/-30 degrees can be realized; the turning mirror assembly 3 adopts a 45-degree plane mirror, and the length of a short shaft is more than 50 mm; the optical receiving antenna 4 adopts a lens, the aperture of the lens is 50mm, and the focal length is 100 mm; the dichroic filter 5 realizes 490nm reflection and 450nm transmission; the beam splitter 6 divides the 450nm light into two beams, and the intensity ratio is 1: 1; the emission wavelength of the communication laser 7 is 490nm, a 980nm semiconductor laser is adopted for pumping, ytterbium-doped optical fiber is adopted for amplification, and then frequency doubling crystals are adopted for conversion to 490 nm; the single photon detector 8 adopts a silicon-based Geiger mode APD, a unit detector or a four-quadrant detector can be selected, and the detection dead time is less than 50 ns; the high-sensitivity area array detector 9 adopts a CMOS area array detector, the array scale is not less than 256x256, a 4-T process is adopted, and the dark current is less than 3 e-/fps. The divergence angle of the communication signal of the terminal A is 5mrad, the receiving field of view is 1 degree, and the transmitting laser power is 3W.
And a terminal B:
the wavelength of the transmitted communication light is 450nm, and the receiving wavelength is 490 nm. The watertight shell 1, the tracking and pointing mechanism 2, the turning mirror assembly 3 and the optical receiving antenna 4 are the same as the terminal A; the dichroic filter 5 realizes 450nm reflection and 490nm transmission; the beam splitter 6 splits 490nm light into two beams, with an intensity ratio of 1: 1; the communication laser 7 emits light with the wavelength of 450nm, adopts a 900nm semiconductor laser for pumping, adopts ytterbium-doped optical fiber for amplification, and adopts a frequency doubling crystal to convert the wavelength to 450 nm; the single photon detector 8 and the high-sensitivity area array detector 9 are the same as the terminal A. The communication signal divergence angle of the terminal B is 5mrad, the signal light receiving field of view is 1 degree, and the emitted laser power is 3W.
The communication method comprises the following steps:
1) a laser link is first established. The terminal A is used as an initiator, and according to the approximate position area of an opposite side provided by an installation platform (such as a submersible), the uncertainty is less than 10 degrees, the tracking and pointing mechanism 2 is used for deflecting and emitting communication light, the uncertain area of the terminal B is scanned in a large range, and the scanning can adopt rectangular or spiral scanning; the detection view field of the area array detector 9 of the terminal B is larger than 10 degrees, and the terminal B can be directly aligned to the terminal A; when the signal light of the terminal A sweeps the position of the terminal B, the area array detector of the terminal B can output a light spot effective signal and the position of the light spot effective signal, the terminal B calculates the deflection angle distance between the position of the light spot and the ideal position, controls the tracking and pointing mechanism 2 to compensate the corresponding angle and points the signal light to the terminal A; the terminal A also detects the signal light of the terminal B, and controls the tracking and pointing mechanism 2 to lead the signal light to the vicinity of the ideal position of the detector according to the light spot position of the area array detector 9, so that the signal light is stably pointed to the terminal B; the terminals A, B track each other's signal light to complete the link establishment.
2) Data is transmitted and received. Terminal A, B may be used as both a sender and receiver of data and may have full duplex communication capabilities. Take terminal a transmission and terminal B reception as examples. The terminal A carries out serial cascade 16-PPM coding on binary data to be transmitted, channel coding and modulation are realized, an electric signal is generated to control a communication laser 7 to generate light pulse, the pulse width is less than 10ns, and the effective information transmitted by a single pulse is 2 bits; the number of single pulse photons received by the single photon detector 8 of the terminal B is more than 3 on average, electric pulses are generated after the photons are detected, the rising edges of the electric pulses correspond to signal position information, and communication information is extracted by adopting a serial cascade 16-PPM decoding method.

Claims (2)

1. The utility model provides a long-range photon counts communication system under water, includes watertight casing (1), trails directional mechanism (2), replicator mirror subassembly (3), optical reception antenna (4), color separation piece (5), beam splitter (6), communication laser instrument (7), single photon detector (8), high sensitivity area array detector (9), control electronics (10), its characterized in that:
the watertight shell (1) is provided with a light-transmitting glass window, and the glass window is opposite to the tracking and pointing mechanism (2); the tracking and pointing mechanism (2) is a two-dimensional pointing mirror mechanism; the optical receiving antenna (4) is a transmissive or reflective optical focusing element; the communication laser (7) adopts a blue-green wave band, and the wavelength is 400nm to 532 nm; the light splitting sheet (6) divides the communication signals into two paths, and the intensity proportion of the two paths of signals can be adjusted; the high-sensitivity area array detector (9) adopts a CMOS or CCD detector;
the watertight housing (1) seals other components in the housing, received signal light is reflected or projected through a glass window of the watertight housing (1), then is transmitted to the single photon detector (8) and the high-sensitivity area array detector (9) through the light splitting sheet (6) according to a set proportion, and transmitted signal light is emitted by the communication laser (7), reflected through the light splitting sheet (5) and transmitted to the outside of the system through other components. The control electronics (10) are electrically connected with the tracking and pointing mechanism (2), the single-photon detector (8) and the high-sensitivity area array detector (9).
2. An underwater remote photon counting communication method based on the underwater remote photon counting communication system of claim 1, characterized by comprising the following steps:
1) communication needs to be carried out between two underwater remote photon counting communication systems, which are named A, B respectively; the wavelengths of the two system communication lasers (7) are different, and the communication light of the opposite side is respectively introduced into the single photon detector (8) and the high-sensitivity area array detector (9) through the wavelength selection of the color separation sheet (5);
2) when communication starts, the A system controls the tracking pointing mechanism (2) to deflect, transmits a communication signal to the vicinity of the B position and performs small-range scanning. The system B also controls the deflection of the tracking and pointing mechanism (2), aligns the view field of the high-sensitivity area array detector (9) with the system A, and records the angle information of the tracking and pointing mechanism (2) at the moment and positions the tracking and pointing mechanism when the detector detects a signal from the opposite side; at the moment, the communication signals emitted by the A, B can be detected by a high-sensitivity detector (9) of the opposite side, closed-loop control is formed by the communication signals and the tracking and pointing mechanism (2), the signal light spots are stabilized to the center of the view field of the detector, and at the moment, the signal light enters the single-photon detector (8);
3) the information transmitting end adopts a pulse position modulation and serial cascade channel coding method, a single photon detector (8) at the receiving end converts single photon level light pulse into an electric signal, the electric signal is sent to a control electronics (10), decoding and demodulation are carried out according to an agreed coding and modulation mode, and original data are recovered.
CN201911124501.XA 2019-11-18 2019-11-18 Underwater remote photon counting communication system and method Pending CN110932778A (en)

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Publication number Priority date Publication date Assignee Title
CN114301530A (en) * 2021-12-31 2022-04-08 长春理工大学 Dynamic capturing and tracking device for underwater wireless optical communication link

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CN114301530B (en) * 2021-12-31 2023-05-05 长春理工大学 Dynamic capturing and tracking device of underwater wireless optical communication link

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