Large-Scale Multilongitudinal Mode Fiber Laser Sensor Array With Wavelength/Frequency Division Multiplexing

A large-scale multilongitudinal mode fiber laser sensor array is proposed and demonstrated experimentally based on wavelength/frequency division multiplexing and beat frequency demodulation technique. In the proposed hybrid multiplexing sensing system, the frequency division multiplexing is realized by designing n fiber lasers with different cavity lengths, while the wavelength division multiplexing is achieved by incorporating a 1 × m coupler and an m-channel wavelength division demultiplexer. By making the operating wavelength of frequency-multiplexed lasers equal to the central wavelength of each channel in the demultiplexer, the light of each laser is coupled independently to the corresponding channel. Therefore, the multiplexing capability of the multilongitudinal mode fiber laser sensors is greatly improved and the maximum number of multiplexed sensors is m × n theoretically. To verify the proposed wavelength/frequency division multiplexing system, a 4 × 4 multilongitudinal mode fiber laser sensor array was set up and investigated. Experimental results show that there is a low crosstalk between the adjacent channels. The proposed wavelength/frequency hybrid multiplexing technology has the ability to monitor simultaneously a large number of fiber laser sensors.