Hybrid wavelength- and frequency-division multiplexed fiber laser sensor array.

The Letter describes a hybrid multiplexing scheme for a multi-longitudinal-mode fiber laser sensor array by combining wavelength-division multiplexing and frequency-division multiplexing techniques. The proposed multiplexing system consists of many subgroups, each of which has many fiber laser sensors with approximately equal laser-operating wavelengths but different cavity lengths. Each sensor in one subgroup can be interrogated by using frequency-division multiplexing technology because of different sensors with different beat frequencies. For different subgroups, they are characteristic of different laser-operating wavelengths. Each subgroup can be divided into the designed channel by dense wavelength-division multiplexers. At last, a 4×4 sensor multiplexing system was experimentally validated. The strain or temperature applied on each sensor was successfully extracted. The proposed multiplexing system provides a dramatic increase in the number of multiplexed sensors. It greatly reduces the weight, volume, and cost of each sensor and offers a competitive solution for a large-scale monitoring system.