Data And Video Frequency Signal Blending Optical Fiber Transmission System

The thesis makes audio frequency signal and video frequency signal FM transmitting 40km through optical fiber to achieve long-distance watch. The experiment uses the video frequency signal of the output of black-white camcorder the signal origin to debug. The system is suitable to use as a long-distance watch within 40km. It may be installed in most places which need to watch. It also can be used in the South and the North for its dynamic scope. It can transmit audio frequency signal and video frequency signal at the same time. If adding power to the transmitter,the watch distance may be extended.The effect of the system is good if transmitting black-white video frequency signal,but ordinary if transmitting color signal.If enhancing the phase and augment of differential calculus, quality will improve.System index: Video frequency input Vp-p=1V (75 load)SNR=46dBVideo frequency output Vp-p=1V (75Q load)SNR=42dBDelicacy of receiver Pr=-30dBmTransmission distance L~40kmFirst I introduce some knowledge about optical fabric and its advantage over cable.Through comparison of different modulation,this paper point out that PFM modulation is a good modulation mode.This paper particularly introduce the characteristic of PFM modulation,formation and elements of transmission system,and the SNR of system.This paper also particularly discuss the frequency modulation transmisson of square wave and the formation and application and it also demonstrate the feasibility of system from technique index,SNR,delicacy of receiver,dynamic scope and linearity characteristic.The experiment use the video frequency signal output by CCD black and white vidicon the signal fountain.I design a long distance video frequency watch system which is the same with scope less than 40km.This paper divide the system into transmission and receiver to demonstrate the formation of system.I design the system according to parameter request,characteristic of parts.The index of modulator is:Center frequency: fc= 18 MHzBiggest deflection of frequency: Afm= 5 MHzThe drive must offer 63mA drive current.In view of the tiptop frequency of modulator.the drive's speed must be very high.The index of preamplifier is: bandwith : 29MHzPr : - 30dbmThe fifth chapter study the modulation.introduce the experimental instrument.and carry through the experiment to check the capability of modulator. Through comparison .1 choose the work condition : Cx=25pF Vr=1V which satisfy the demand and use double frequency demodulator. At last I analyse the capability of SNR and Pr, and confirm the dynamic scope of system.