Digital sensor based on multicavity fiber interferometers

Abstract

Vernier effect systems with more than two reflectors or coupled-ring resonators are highly attractive for sensing applications, since one can have better control of tailoring their transmission response as compared to traditional single-cavity structures. Here, we propose and provide a prescription for designing a digital Vernier sensor that can be built from three off-the-shelf fiber Bragg gratings. The proposed sensor employs a tapered fiber in one of the cavities as a sensing head and senses changes in the form of discrete (digital) wavelength jumps of resonant modes. We show that the sensitivity, detection limit, and dynamic range of the sensor can be predictably controlled by careful selection of cavity lengths. As an example, we show by simulations that the detection limit of the proposed sensor reaches 10 6, which is eight times more than the previously proposed digital sensor based upon coupled-ring resonators.