Research And Implementation Of FPGA-Based Wireless Optical Communication Modulation Technology

Wireless optical communication using light as a carrier to transmit information can ease the growing tension of the radio frequency spectrum resources with a high bandwidth, low radiation, anti-interference and other characteristics of optical communications. Thus it has been attentioned by both home and abroad and becomes a hot spot of wireless research field.With the development of related technologies, such as life of light-emitting diode prolonged, modulation bandwidth increased, sensitivity photo detectors strengthened and response speed raised, etc., wireless optical communication has a great potential in development and application prospects. In order to improve the spectrum efficiency of wireless optical communication,it can improve the optical power, increase the detection area of the photodetector, select the appropriate laser wavelength for atmospheric window, select the appropriate modulation and demodulation techniques for system and take other methods to achieve.But the laser causes eye damage, improving the optical power blindly is not a good idea, meanwhile increasing the detection area causes the system bandwidth narrowed and efficiency of the system band decreased. Based on the current situation and existing optical devices development, searching appropriate modulation and demodulation techniques to improve the performance of UV communication is particularly important.This paper firstly summarizes the characteristics of the wireless spectrum, elaborates the principles and features of wireless optical communication; in order to improve the performance of the communication system, the paper designs to realize various suitable ultraviolet communication modulation and demodulation techniques included:on-off keying modulation OOK, pulse position modulation PPM, differential pulse position modulation DPPM, digital pulse interval modulation DPIM, double header pulse interval modulation DH-PIM and fixed-length digital pulse interval modulation FDPIM and other modem technologies, and also conducts experiments to test various modulation and demodulation techniques to draw comparison figures of the average optical power, transmission capacity, transmission rate, error rate and other communication performance, after analysis we conclude that a variety of modulation techniques in spectrum utilization and the BER performance need to be further improved; this paper presents that using the3G communications core spread spectrum technology as modulation, designs and implements spread spectrum communication UV experimental system, it is verified by experiments the information spread-encoded after transmission can significantly reduce the error rate, and error rate decreases with the increase of the spread sequence period; Finally, based on the principle of spread spectrum technology and orthogonality of PN code, this paper proposes a multi-user spread spectrum communication based on ultraviolet communication and designs methods to realize, also has a technical summary and outlook.