Laser-self-mixing interferometric fiber strain sensor

A new fiber strain sensor based on the Laser-Self-Mixing effect in Distributed Feedback Laser diodes is presented. Compared with existing fiber strain sensors based on Fiber Bragg Gratings, that are sensitive to local strain, our device achieves comparable sensitivity (~ 1 μe) distributed along the whole fiber length and requires a much simpler electronics . The sensor is based on the interferometric principle of the laser-self-mixing in the moderate feedback regime, whereby the fiber strain results in a variation of the optical path-length seen by the radiation reflected by the end facet of the fiber itself. Increasing or decreasing strain recognition is directly provided by the sign of the sawtooth-like fringes derivative.