DISTRIBUTED BRILLOUIN SENSOR SYSTEM BASED ON DFB LASERS USING OFFSET LOCKING

摘要

A distributed Brillouin sensor system is provided. The system has two distributed feedback (DFB) lasers, which are locked at the Brillouin frequency of the optical fiber through offset locking method by coupler splitting into two parts. The split parts are sent to two photodiodes, the outputs of which are sent to a mixer. A PID controller means follows the mixer and a current controller follows the PID controller. The lasers have a wavelength of 1550nm. The PID controller locks the frequency difference. An optical delay line is used to produce the frequency tuning of the two DFB lasers around the Brillouin frequency of the optical fibers. The lock-in amplifier is used to keep the DC level of the optical modulator at minimum.