Research on the Distributed Optical Fiber Measurement and the Data Processing

The sigma delta modulator has been designed as an A/D convertor to finish high resolution distributed optical fiber measurement system. Due to the slow temperature change, the input signal x(t) is seen as a corresponding rational number according to the precision desire, the output data stream has periodic characteristic based on Gray´s result. So the analog signal x = 1/T Sigma_i=0 ^T-1y(i) = ((P - K)/T)V and is calculated in a period T that has a high precision. Further more, when input signal x(t) = a/b has a common factor, the calculating period T can be reduced effectively by autocorrelation analysis so calculation time is reduced. The circuit using CPLD and DSP is not complex to design sigma delta A/D convertor, and the data processing can be controlled and adjusted. So it fit the demand of precision and speed of measurement system