Optimal Design of Feedback-Interferometric Fiber Laser Sensors

Efficient first-principle simulation with self-consistence of the feedback-interferometric fiber laser sensor has been studied. The feedback-interferometric fiber laser sensor consists of a Distributed Bragg Reflectors/Distributed Feedback (DBR/DFB) fiber laser and an external feedback sensing element. The approach is self-consistent in that it effectively integrates the inter-dependence of the 980-nm pump/1550-nm laser powers and the rate equations of the Er/Yb co-doped fiber laser medium. The 1550-nm laser field is efficiently solved by Coupled Modes Theory (CMT) method while the solutions of the rate equations are obtained with the iterative Newton-Raphson method. Four types of external reflection schemes have been simulated: 1) without reflection at either side; 2) reflection at the pump side; 3) reflection at the remote side; and 4) reflections at both sides of the fiber laser. With the self-consistent simulation, the lasing wavelength and lasing signal power for various reflection schemes are obtained. In this investigation, the procedure to optimize the reflections to achieve optimal sensor sensitivity is demonstrated.