Study Of Advanced Optical Frequency-sweeping And Frequency Chirp Control

Optical frequency-swept laser(OFSL)has a fast frequency sweeping speed and a wide sweeping span compared to traditional electric frequency-swept laser(EFSL),so it has been widely used in optical communication,optical sensing and optical imaging.The broadened sweeping span can be obtained by single sideband(SSB)modulation.However,RF signal is limited in the speed and bandwidth due to the electronic bottleneck.It becomes difficult to promote the performance of fiber sweeping in modulation.In this work,all-optical signal processing is used to help achieve high performance OFSL.This paper proposes the use of recirculating frequency shifter(RFS)to obtain broadened OFSL.We take SSB modulator as frequency shifter unit and get broadened sweeping span of OFSL at high-order sideband of a comb produced by RFS.And ~11.44-GHz optical frequency sweeping is experimentally achieved with the radio frequency(RF)sweeping span of only 200 MHz,corresponds to 57-times broadening.Meanwhile,as the similarity between sweeping signal and chirp,we use the method of frequency chirp magnification to enhance the strain and temperature sensitivity of FBG sensor.The measured sensitivity enhancements for the strain and temperature are both about 14 times at idler-14 by modulating the pump with pulses to increase the peak power and induce OPA.At last,we propose another way to produce supercontinuum.