POLARIZATION NOISE DECREASING CIRCUIT OF BOTDA

摘要

PURPOSE:To lessen the dependence on the polarization of an optical fiber by rotating the plane of polarization of a light source at prescribed angles and adding and averaging the data by orthogonal Brillouin amplified waveforms and the dependence characteristics of a photodetecting system on polarization. CONSTITUTION:Continuous light 11 of the light source 1 is made incident from one end of the optical fiber 10 and the pulse light 12 of the light source 12 is made incident from the other end of the optical fiber 10. A polarization rotating device 3 rotates the angle of the plane of polarization of the pulse light 12 to +45 deg. and -45 deg.. An optical coupler 4 takes the output subjected to Brillouin amplification out of the optical fiber 10. A photodetector 5 receives the output of the optical coupler 4 and a memory 6A stores the output 16 of the photodetector 5 when the angle is rotated +45 deg. by the polarization rotating device 3 and the output 17 of the photodetector 5 when the angle is rotated -45 deg.. A memory 6B stores the data 18 by the dependence characteristic of the photodetecting system on polarization and an adder 8 adds and averages the output 16, the output 17 and the data 18.