Investigation of Low-Cost Interrogation Technique Based on Modulated Distributed Feedback Laser

In this paper a new low-cost fiber Bragg grating (FBG) interrogation technique for static applications is demonstrated. The idea is based on the multiplication between the FBG reflectivity profile and the emission of a sawtooth modulated distributed feedback (DFB) laser source. The variation of the FBG wavelength generates a modification in the shape, in time domain, of the reflected light signal. The concept has been proven, using simulation, to cover FBG wavelength shift up to 1.7 nm. Experimental validation was performed for FBG temperature ranging from 6 °C to 50 °C (equivalently 440 pm) with a modulation frequency of 1 kHz. Sensitivity higher than 3.5 mV/pm is achieved in all circumstances with an estimated resolution of 8 pm.