A large field of view angle diversity receiver for underwater wireless optical communication

Abstract

This invention relates to a large field-of-view diversity receiver for underwater wireless optical communication, belonging to the field of underwater optical communication technology. It includes a top lens-detector module pointing vertically towards the zenith and four surrounding side lens-detector modules. The four side modules are evenly distributed along the circumference and have a uniform tilt angle relative to the zenith direction, causing the spatial fields of view of each module to partially overlap, thus synthesizing a large composite field of view. Each module consists of a defocused condenser lens and a photodetector. This invention avoids the trade-off between gain and field of view limitation of traditional single-lens receivers, relaxing communication alignment requirements while retaining the high-speed transmission advantage of small-area detectors. Combined with a signal combining algorithm, it can effectively combat underwater signal fading, making it suitable for underwater wireless optical communication systems.

Claims

1. A wide field-of-view diversity receiver for underwater wireless optical communication, comprising a centrally located top lens-detector module and four surrounding side lens-detector modules, characterized in that: The top lens-detector module points vertically towards the zenith, and the four side lens-detector modules are evenly distributed around the top lens-detector module along the circumference. The azimuth angles of the four side lens-detector modules are 0°, 90°, 180° and 270°, respectively. The four side lens-detector modules have a uniform tilt angle relative to the zenith direction. The fields of view of each lens-detector module partially overlap in space, thus jointly synthesizing a large field of view.

2. A large field-of-view diversity receiver for underwater wireless optical communication according to claim 1, characterized in that: The top lens-detector module and the four side lens-detector modules each consist of a condenser lens and a photodetector, and the photodetector in each module is located on the optical axis of its corresponding condenser lens.

3. A large field-of-view diversity receiver for underwater wireless optical communication according to claim 2, characterized in that: In each of the lens-detector modules, the axial distance between the photodetector and the condenser lens is set to be less than the focal length of the condenser lens, so that the module is in a defocused state, so that the incident light forms a defocused spot of finite size on the plane of the photodetector.

4. A large field-of-view diversity receiver for underwater wireless optical communication according to claim 3, characterized in that: The axial distance between the photodetector and the focusing lens is set to 15 mm.

5. A large field-of-view diversity receiver for underwater wireless optical communication according to claim 1, characterized in that: The tilt angle of the four side lens-detector modules relative to the zenith direction is set to 50° to synthesize a uniform composite field of view greater than 120° in all 360° omnidirectional angle range.

6. A large field-of-view diversity receiver for underwater wireless optical communication according to any one of claims 1 to 5, characterized in that: The receiver also includes a signal processing unit, which is communicatively connected to the five lens-detector modules. The signal processing unit is used to synchronize the electrical signals converted from each lens-detector module and combine the signals from multiple branches using a maximum ratio combining algorithm to maximize the signal-to-noise ratio at the receiver.

7. A large field-of-view diversity receiver for underwater wireless optical communication according to claim 6, characterized in that: The signal processing unit is also equipped with a Volterra nonlinear equalizer, which is used to equalize the single composite signal formed by the maximum ratio combining algorithm to reduce the nonlinear distortion caused by optoelectronic devices and underwater channels.

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