All fiber strain sensor based on the Laser-Self-Mixing effect

A new fiber strain sensor is presented based on the laser-self-mixing (LSM) effect in distributed feedback laser diodes (DFB). Compared to existing fiber strain sensors based on fiber Bragg gratings (FBG), our device achieves comparable sensitivity (~1 muepsiv) requiring much simpler electronics. In the moderate feedback regime, sawtooth-like fringes are observed in the optical power emitted by a standard single-mode optical fiber (SMF) pigtailed to a 1550 nm DBF laser, directly monitored by the internal photodiode. The sign of the fast slope of the fringes allows for identification of increasing or decreasing strain. The system is all-fiber and does not require the costly interrogation electronics of FBG sensors.