The Implementation And Improvement Of High-speed Solar-blind Ultraviolet Video Communication System

The solar-blind ultraviolet(UV)communication system,taking ultraviolet light with a wavelengths of 200 to 280 nm as communication carrier,is a new free-space optical communication system.Due to its advantages of fine confidentiality,strong anti-interference ability,low intercepton rate,and the capability of working at all-time and all-directions via non-line-of-sight(NLOS)links.It has been paid close attention by many technical staffs in internal and external.Based on the detailed discussion of the UV communication channel model,the influence from different weather on UV's transmittance are simulated.Then,the solar-blind UV communication system,using OOK modulation,is designed based on the FPGA.It chooses UV light emitting diode(LED)as the light source in the transmitter,PIN photodiode as the detector in the receiver.The system works with the communication speed of 1.92Mbit/s,when the communication distance is 4 meters.In addition,to speed up the communication rate of the system,quantum-cutting fluorescent glass was used to realize photon number multiplication and wavelength conversion.Schemes for improving the sensitivity of the receiving end were proposed from two perspectives: energy conversion efficiency and quantum conversion efficiency.From the viewpoint of energy conversion efficiency,a detection device based on a wavelengthconverted was designed.The fluorescent glasses absorbs the solar-blind UV lights with a wavelength of 265 nm and stimulates visible lights with the wavelength of 380-780 nm.The sensitivity of the Siphotodiode to visible light is about 10 times of that to the solar-blind UV lights.From the perspective of quantum conversion efficiency,a detection device based on quantum-cutting photomultiplier tube photon amplification is designed.Since the quantum-cutting fluorescent glass absorbs one solar-blind ultraviolet photon,it can excite 2-3 long-wavelength photons(wavelengths are generally in the range of 600 nm to 1100 nm).The photomultiplier tube belongs to the active detector device.Its response current is proportional to the number of photons,and its sensitivity to visible lights,or infrared lights,is much higher than that of solar-blind UV light.According to the design scheme,the receiving end of the solar-blind UV communication system is improved.The experimental test results show that the two schemes can improve the detection sensitivity of the blind UV light in different degrees,so that the magnification of the amplifier circuit can be reduced,and the communication speed of the system can be increased.When the two schemes are used for detection,the system communication speed can be increased to 2.1 Mbit/s and 2.3 Mbit/s,respectively.