A Low-Cost FDM System for Multi-Longitudinal Mode Fiber Laser Sensor Array

A low-cost and real-time frequency division multiplexing system is proposed based on multi-longitudinal mode fiber laser sensor array and beat signal demodulation technology. The lasers have staggered cavity lengths with corresponding mode spacing. Beat signals of the longitudinal modes of each laser in the array are detected by a common detector. A relationship is worked out between the maximum multiplexing number of the sensors and maximum detectable frequency. A multiplexing array with four laser sensors is investigated experimentally and its potential application for strain measurement is also demonstrated. In the proposed multiplexing system, only one common photodetector and a commercial frequency analyzer are used to monitor all sensors simultaneously, which greatly decreases the cost of the system and makes it more competitive in large-scale monitoring field.