Versatile all-fiber slow-light assisted sensor

Abstract

We present theoretical and experimental results on a slow-light assisted all-fiber configuration that can be used for efficient sensing of a variety of parameters (pressure, displacement...). In particular, we report here a structure that can be transformed into a slow-light assisted displacement sensor capable of sub-micrometric resolution values with a potentially simple intensiometric measurement scheme. The basic element in the structure is a lossy ring resonator tuned close to the critical coupling regime. In this working regime, the resonator transfer function displays extremely high group delay values close to the resonances, and, accordingly, a large sensitivity to additional losses. A mechanic transducer transforms displacement into small additional losses in the ring. This leads to strong variations in the log transmission of the resonances, which are shown to scale with the group index. This scheme shows orders of magnitude sensitivity enhancements over a conventional bending-loss configuration. We believe that this structure can be further developed to provide large sensitivity enhancements to conventional intensiometric fiber sensors.