Distributed optical fiber sensor based on Raman and Brillouin scattering

A distributed optical fiber sensor based on Raman and Brillouin scattering, comprising:

• a semiconductor Fabary-Perot (FP) cavity pulsed wideband optical fiber laser, a semiconductor external-cavity continuous narrowband optical fiber laser, a wave separator, an electro-optic modulator, an isolator, an Erbium (Er)-doped optical fiber
• amplifier, a bidirectional coupler, an integrated wavelength division multiplexer, a first photoelectric receiving and amplifying module, a second photoelectric receiving and amplifying module, a direct detection system, a narrowband optical fiber transmission grating, a circulator, and a coherence detection module;
• wherein an output terminal of the semiconductor FP cavity pulsed wideband optical fiber laser is connected with an input terminal of the Er-doped optical fiber amplifier;
• an output terminal of the semiconductor external-cavity continuous narrowband optical fiber laser is connected with an input terminal of the wave separator;
• an output terminal of the wave separator is connected successively to the electro-optic modulator which modulates a pulse width of a first signal from the semiconductor external-cavity continuous narrowband optical fiber laser to be the same as a pulse width of a second signal from the semiconductor FP cavity pulsed wideband optical fiber laser, the isolator and another input terminal of the Er-doped optical fiber-amplifier;
• an output terminal of the Er-doped optical fiber amplifier is connected with an input terminal of the bidirectional coupler;
• an output terminal of the bidirectional coupler is connected with a single-mode optical fiber, and another output terminal of the bidirectional coupler is connected with an input terminal of the integrated wavelength division multiplexer;
• two output ports of the integrated wavelength division multiplexer are connected with the direct detection system via the first photoelectric receiving and amplifying module and the second photoelectric receiving and amplifying module, respectively;
• a third output port of the integrated wavelength division multiplexer is connected with an input terminal of the circulator via the narrowband optical fiber transmission grating;
• another input terminal of the circulator is connected with another output terminal of the wave separator, and an output terminal of the circulator is connected with the coherence detection module;
• wherein the narrowband optical fiber transmission grating is an optical fiber grating with central wavelength of 1555.08 nm, spectrum bandwidth of 0.1 nm, attenuation less than 0.3 dB, and isolation higher than 35 dB.