Linearity optimization of edge filter demodulators in FBGs

A kind of electric circuit is improved to optimize the linearity of edge filter demodulators in FBG .By using a logarithm amplifier and an extraction operation,the linear range of optimized edge filter demodulators has been broadened effectively,and the requirement of optical filter's linear range has been reduced.Theoretical analyses and the simulation results indicated that the linear range of optimized edge filter demodulator's covers the whole transition region of the edge filter,while a strict linearity of the optical filter is not necessary.