CN112511228A

CN112511228A - Underwater optical communication circuit and communication method

Info

Publication number: CN112511228A
Application number: CN202110122374.0A
Authority: CN
Inventors: 朱秉诚; 陈鹏; 陈志敏; 史弘历
Original assignee: Nanjing Minzhida Technology Co ltd
Current assignee: Nanjing Minzhida Technology Co ltd
Priority date: 2021-01-29
Filing date: 2021-01-29
Publication date: 2021-03-16

Abstract

The invention discloses an underwater optical communication circuit and a communication method, wherein the underwater optical communication circuit comprises: a first optical signal acquisition module; the first optical signal acquisition module comprises a first optical signal acquisition unit for receiving optical signals and an operational amplifier for performing operational amplification on the output of the first optical signal acquisition unit; a second optical signal acquisition module; the second optical signal acquisition module comprises at least one second optical signal acquisition unit for receiving optical signals and an operational amplifier for performing operational amplification on the output of the second optical signal acquisition unit; and the change-over switch is used for realizing high-speed low signal-to-noise ratio communication by the one-way output of the first signal acquisition module or realizing low-speed high signal-to-noise ratio communication by the parallel output of the first signal acquisition module and the second optical signal acquisition module. The circuit of the invention can realize digital/analog communication switching by opening/closing the selector switch, and can realize long-distance voice communication or short-distance high-speed digital communication.

Description

Underwater optical communication circuit and communication method

Technical Field

The invention relates to a low-cost underwater optical communication amplifying circuit capable of switching voice and digital communication at will, and belongs to the technical field of electricity and information.

Background

Underwater communication is an emerging research field at present, however, due to the particularity of media, the traditional radio frequency electromagnetic wave signals are severely attenuated underwater, the penetration force is insufficient, remote communication cannot be supported, and the underwater communication is also affected by intersymbol interference due to multipath fading. Currently, underwater communication is mainly used in underwater communication systems. The underwater acoustic communication system supports remote communication, but has the limitations of narrow system bandwidth, low transmission rate, significant time delay, difficulty in supporting real-time voice communication, and no potential of underwater high-speed digital communication in related systems. Optical communication has a relatively high rate and low delay, and is used for underwater communication in order to overcome the limitation of underwater acoustic communication.

The existing underwater analog optical communication also has the limitations: the signal of the optical signal is weak under water, and the signal-to-noise ratio is low; the one-way communication visual angle is small and is easy to interrupt; bandwidth is difficult to support high rates of digital communications, etc.

Disclosure of Invention

The invention provides a low-cost underwater optical communication circuit and a communication method for solving the problems, and the low-cost underwater optical communication circuit and the communication method can realize high-speed low signal-to-noise ratio/low-custom high signal-to-noise ratio communication switching.

In order to achieve the purpose, the invention adopts the following technical scheme:

an underwater optical communication circuit, comprising:

a first optical signal acquisition module; the first optical signal acquisition module comprises a first optical signal acquisition unit for receiving optical signals and an operational amplifier for performing operational amplification on the output of the first optical signal acquisition unit;

a second optical signal acquisition module; the second optical signal acquisition module comprises at least one second optical signal acquisition unit for receiving optical signals and an operational amplifier for performing operational amplification on the output of the second optical signal acquisition unit;

and the change-over switch is used for realizing high-speed low signal-to-noise ratio communication by the one-way output of the first signal acquisition module or realizing low-speed high signal-to-noise ratio communication by the parallel output of the first signal acquisition module and the second optical signal acquisition module.

When the underwater optical communication method is used for realizing high-speed low signal-to-noise ratio communication, the first signal acquisition module is output in a single way through a selector switch; when the optical fiber communication device is used for realizing low-speed high-signal-to-noise-ratio communication, the first signal acquisition module and the second signal acquisition module are connected in parallel through the selector switch for output.

As the core of the invention, the selector switch can realize the communication mode switching. When the switch is closed, the combination of multiple paths of optical signals is realized, and low-speed high signal-to-noise ratio communication (capable of supporting analog voice communication) is realized; when the switch is opened, the switch is switched to a high-speed low signal-to-noise ratio channel (which can support a high-speed digital channel). The design has the advantages that the communication mode can be switched according to the communication requirement, and the cost is low.

The working principle of the invention is as follows:

n groups of optical signals obtained by N groups of photodiodes are amplified by respective operational amplifiers and then are selected by a selection switch. One path or N paths of optical signals can be selected to enter the adder by changing the state of the selector switch. When the switch is opened, one path of optical signal enters the adder, the signal-to-noise ratio is relatively low, the input impedance of the adder is small, the bandwidth is large, and high-speed low-signal-to-noise-ratio communication can be supported; when the switch is closed, N paths of optical signals enter the adder to be combined, the signal-to-noise ratio is improved, the input impedance of the adder is increased, the bandwidth is reduced, and low-speed high-signal-to-noise-ratio communication can be supported.

Has the advantages that:

1. the invention realizes the switching of the large-bandwidth low signal-to-noise ratio mode and the narrow-bandwidth high signal-to-noise ratio mode of the optical communication amplifier at the same time. When the method is applied to an underwater optical communication scene, the short-distance high-speed digital communication can be ensured, and the transmission of image and video data is realized. When the distance of the receiving and transmitting end becomes far, the high signal-to-noise ratio analog communication of the long distance can be ensured, and the transmission of the voice instruction is realized. One circuit has two communication modes, so that the cost is reduced.

2. The photodiode is arranged to receive optical signals at different angles, acquire omnidirectional information, and is used for resisting shadow fading phenomena widely existing in a wireless optical communication system and avoiding communication interruption caused by blocking of a direct path channel.

Drawings

Fig. 1 is a block diagram of an underwater optical communication circuit provided in an embodiment of the present invention;

FIG. 2 is a block diagram of a signal acquisition module;

fig. 3 is a circuit diagram of an adder built using an operational amplifier with an analog diversity system.

Fig. 4 is a schematic diagram of an operational amplifier.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

Fig. 1 is a system block diagram of an underwater optical communication circuit of the present invention. As shown in fig. 1, the underwater optical communication circuit of the present invention includes:

The first optical signal acquisition unit and the second optical signal acquisition unit can both use light emitting diodes, and an operational amplifier is connected to the output end of the photodiode to form an optical signal acquisition module, which is shown in fig. 2.

And the multipath output optical signals controlled by the selector switch enter the adder, are combined with the multipath optical signals of the first signal acquisition module and the second signal acquisition module which are connected in parallel, and finally enter the signal receiving device for receiving.

To obtain omnidirectional information of the optical signal, the photodiodes of different paths are arranged to receive optical signals at different angles.

Fig. 3 is a circuit diagram of an adder system constructed using an operational amplifier with an analog diversity system. In the figure, IG1, IG2, IG3, and IG4 are photodiodes, and are basic components capable of converting an optical signal into a weak electrical signal. The inverting input ends (port No. 2 in the figure) of U1, U2, U3 and U4 operational amplifiers are respectively connected with the output ends of photodiodes IG1, IG2, IG3 and IG4 and capacitors C1, C3, C5 and C7, the non-inverting input ends (port No. 3 in the figure) are respectively connected with a resistor R6, R7, R12 and R13, and the inverting input ends and the output ends of the four operational amplifiers are respectively connected with each other through a group of parallel resistors and capacitors (R1, C2, R2, C4, R8, C6, R9 and C8); the electric signal enters the inverting input end of the adder U5 through the change-over switch SW after being amplified, the non-inverting input end of the U5 is connected with the resistor R14, the inverting input end and the output end are connected through the resistor R5, and the output end is connected with the VM1 display signal. When the switch is turned on, only one path of signal enters the adder, and the signal is finally output; when the switch is closed, the N paths of signals enter the adder, and the sum of the N paths of signals is finally output.

Fig. 4 is a schematic diagram of a single operational amplifier U with a resistor R connected to the non-inverting input, a resistor Rin and a signal source VG1 connected to the inverting input, a resistor Rf connected between the inverting input and the output, and finally the output signal shown by VM 1. The amplifier input voltage is

Output voltage of

At a same-phase input terminal voltage of

At an inverting input terminal voltage of

. The following equation can be derived from the characteristics of the operational amplifier and the superposition principle:

further, the ratio of the output voltage to the input voltage (actual closed loop gain) can be derived as:

maximum closed loop gain of

The ratio of the actual closed-loop gain to the maximum closed-loop gain is:

it is noted that

Is a monotonically decreasing function, therefore

Is a monotonically decreasing function, therefore when

At an increase, s increases, i.e. the 3dB bandwidth increases. According to the shannon equation, the maximum information rate C transmitted is determined by the following equation:

where W is the bandwidth, S is the average power (watts) of the transmitted signal within the channel, and N is the gaussian noise power (watts) within the channel. As the bandwidth increases, the maximum information rate increases accordingly.

Returning to FIG. 3, when the switch is closed, the M signals are connected in parallel and simultaneously

The M input resistors are connected in parallel and are one M times of the resistance value of the single-path signal, the 3dB bandwidth is reduced relative to the single-path signal when the single-path signal is accessed, the communication speed is reduced, but the signal-to-noise ratio is improved due to the combination of the M paths of signals, and the low-speed high-signal-to-noise ratio communication is supported when the switch is closed; similarly, when the switch is turned on, only one signal enters the adder, the signal-to-noise ratio is relatively reduced, but the input resistance value is increased, so that the system bandwidth is increased, the communication speed is correspondingly increased, and the system supports high-speed low-signal-to-noise ratio communication.

In summary, the effect of switching between the large-bandwidth low snr mode and the narrow-bandwidth high snr mode can be achieved by changing the state of the switch.

Claims

1. An underwater optical communication circuit, comprising:

2. The underwater optical communication circuit of claim 1, further comprising:

and the adder is used for combining the multipath optical signals of the first signal acquisition module and the second signal acquisition module which are connected in parallel.

3. The underwater optical communication circuit of claim 1, further comprising:

and the signal receiving device is used for receiving the optical signals combined by the adder.

4. The undersea optical communication circuit of claim 1 wherein said second optical signal acquisition unit and said first optical signal acquisition unit are configured to receive optical signals at different angles.

5. The underwater optical communication circuit according to any one of claims 1 to 4, wherein the first optical signal acquisition unit is a photodiode, and the operational amplifier is connected to an output end of the photodiode.

6. The underwater optical communication circuit according to any one of claims 1 to 4, wherein the second optical signal acquisition unit is a photodiode, and the output end of the photodiode is connected to the operational amplifier.

7. An underwater optical communication method, characterized in that the underwater optical communication circuit of any one of claims 1 to 6 is used for communication; when the signal acquisition module is used for realizing high-speed low-signal-to-noise-ratio communication, the first signal acquisition module is output in a single path through a selector switch; when the optical fiber communication device is used for realizing low-speed high-signal-to-noise-ratio communication, the first signal acquisition module and the second signal acquisition module are connected in parallel through the selector switch for output.