Mulan Lake Experiment Video

On December 29, 2022, the underwater optical communication research and development team of Wuhan Liubo Optoelectronics successfully conducted a multi-point networking underwater wireless optical communication experiment in the Mulan Lake water area of Wuhan City.

Before the experiment, the water quality of Mulan Lake was tested, and the water quality attenuation coefficient was 2.61dB/m. In order to realize multi-point networking communication, the beam angle of the LED emission light source is designed to be 120 °, and the receiving end uses a highly sensitive photomultiplier tube tube (PMT) as a large field of view receiving photodetector, with a receiving field of view angle of about 40 °. During the experiment, underwater optical communication equipment was installed at the lower end of the experimental frame and immersed in the lake water, about 1.5 meters away from the water surface. The upper end of the experimental frame was placed on the ship's side, and the position, distance, and direction of the equipment were controlled by driving the ship. Multiple modes of underwater communication testing were conducted.

(1) Point-to-point underwater wireless optical communication testing

Install blue light equipment with a beam divergence angle of 120 ° on the small boat end, and green light equipment with a receiving angle of 40 ° on the large boat end. Adjust the distance and pointing angle between the equipment by driving the boat (see Figure 1). Experiments have shown that when the central axis of the transmission is deflected to the left or right by 60 degrees, and the optical axis of the receiving end is deflected in the reverse direction by 20 degrees, image and video communication can be carried out normally in both directions. The maximum communication rate is 20Mbps, which means underwater wireless optical communication can still be maintained when the maximum deviation between the transmission and receiving optical axes is 80 degrees. The communication distance reached 13 meters with a water quality attenuation coefficient of 2.61 dB/m. The water quality attenuation coefficient in deep-sea environments is around 0.2dB/m, and the communication distance of this wide-angle communication device can exceed 50 meters in this water quality environment.

The test also verified that the two ships can maintain communication while driving, and verified that wide-angle LED communication devices can carry out mobile optical communication tasks underwater, laying the foundation for optical communication between mobile platforms such as underwater handheld optical communication, underwater robots, and underwater submersibles.

         Figure 1 Experimental scenario of 120 ° beam angle to point mobile optical communication (blue light emission, green light reception)

(2) 1 transmitter and 3 receivers underwater wireless optical communication test

Place the devices into the lake water separately, and use a blue light device with a beam angle of 120 ° to send video data. Three green light devices are placed in the area covered by 120 ° blue light, with a distance of 2-3 meters between the receiving devices, while receiving video data. The experiment proved that three receiving devices can simultaneously receive real-time video from the transmitting end normally (see Figure 2). This experiment verified the feasibility of establishing an underwater LiFi (optical network), making wireless optical communication technology have broad application prospects in underwater.

Figure 2 Underwater optical communication network testing scenario diagram

(3) Full duplex underwater wireless optical communication testing

A blue light device and a green light device were placed in the lake water, and data was transmitted and received in full duplex mode at a large divergence angle of 120 °. Full duplex transmission of images and real-time videos was successfully achieved, and the highest bidirectional communication rate was measured to reach 15Mbps (see Figure 3).

Figure 3 Real time full duplex testing scenario diagram

This experiment completed underwater full duplex communication, mobile optical communication, and one-to-many network communication. This technology product is suitable for underwater exploration, underwater operations of mobile equipment, high-speed data communication between seabed observation instruments and ships, unmanned underwater vehicles, submarines, and other fields.

Wuhan Liubo Optoelectronic Technology Co., Ltd. is a national high-tech enterprise and a small and medium-sized technology enterprise. The company mainly engages in product research and development, manufacturing, and production in the fields of space optical communication, underwater optical communication, high-speed optoelectronic detectors, etc. Its main products have passed ISO9001 quality system certification. The company has been committed to promoting the practical engineering application of underwater wireless optical communication equipment in the past two years, and has developed several new types of underwater wireless optical communication equipment. They have been applied in various scenarios of underwater wireless high-speed data transmission, promoting the development of underwater economic activities in China. The company culture adheres to the spirit of "self-improvement, perseverance, practicality, and innovation", and is committed to becoming an internationally leading provider of mobile optical communication and underwater optical communication equipment manufacturing and services.

Figure 4 Wuhan Liubo Optoelectronics Underwater Optical Communication R&D Team