Measurement of Brillouin gain spectrum of an optical fiber using direct frequency modulation of a laser diode

Summary form only given. Brillouin gain spectrum measurement for optical fibers offers an efficient means of distributed strain or temperature sensing. Although there are several sensing schemes of good performance, they appear expensive for commercial application. What makes them expensive is the requirement for narrow-linewidth pump and probe lightwaves with a precisely controlled frequency difference. Typically, a frequency difference of 10 GHz with a precision of 1 MHz is required. We present a novel simple scheme for measuring the Brillouin gain spectrum of optical fibers. In the scheme, we generate the pump and probe lightwaves using direct modulation of a laser diode. This simple scheme would enable a cost-effective sensing system.