Research And Realize On Demodulation System Based On The3×3Coupler

From the latter half of the twentienth Century to the present decade, informationtechnology and sensor technology based on optical fiber communication and optical fibersensing technology have achieved great development and promote the grogress of humansociety. Optical fiber communication network has become the optimum transmissionmedium.Optical fiber communication is main content of the information society and worldcommunication construction. In recent years, optical fiber coupler in optical fiber sensorsystem as an important passive devices arouses great interest. At the same time, demodulationof3×3fiber coupler in the communication field caused the wide attention of people. It can beused for signal demodulation of interferometric fiber optic sensors, Fiber Bragg Gratingssensors, fiber-optic laser sensor, fiber-optic hydrophone, optical magnetometers and so on.At First, the paper describes the background and research significance of optical fibresensor and3×3coupler. Secondly, a brief introduction of the basic concepts of optic fiber,modulation technology of optic transmission.And mainly introduces the phase modulation,which leads to the two modulation methods based on phase demodulation.By comparing thetwo modulation methods, demodulation system based on the3×3coupler show theadvantages. Then I introduce detail principle of3×3coupler. Based on the previous work, Iwas derivating principle of3×3coupler strictly on mathematics. Through the technology ofMATLAB of the current cutting-edge, I design demodulation system based on the3×3coupler.In the demodulation process, I theoretically analy the signal changes at every level,and useeach level of the signal waveform to describe the signal changes. The demodulation methodbased on the3×3coupler is stable, reliable, simple, and does not require a modulated lightsource.Finally, the paper introduced the principle and structure of FPGA, the process of FPGAdevelopment, Quartus II software in FPGA. According to demodulation principle based on the3×3coupler, Quartus II can design the corresponding modules of various algorithms.Throughthe simulation result of various modules based on the3×3coupler demodulation system, thefeasibity of achieving demodulation system based on the3×3coupler on FPGA can beproved.It also can ensure demodulation system based on the3×3coupler on FPGA run fastlyand correctly. At the same time the demodulation method in the application of the engineering practice laid theoretical foundation.