Response of a PCF-based modal interferometer to lateral stress: Resonant behavior and performance as sensor

- A fiber interferometer with good behavior as lateral stress sensor is presented.
- We provide optimization guidelines of the sensor, concerning the interferometer length and the transmission of its splices.
- Its response under periodic forces is characterized, face to possible applications of the device as vibration monitor.
- Resonances found under periodic forces are well explained by treating the interferometer as an elastic cylinder.
- In nonlinear regime, period doubling and other nonlinear behaviors are also observed.

The performance of a fiber-based modal interferometer as lateral stress sensor has been analyzed, both for static and periodic forces applied on it. The central fiber of the interferometer is a photonic crystal fiber. Forces are applied on it perpendicular to its axis, so that they squeeze it. In static situations, changes in the transmission spectrum of the interferometer are studied as a function of the charges applied. Measurements with several interferometers have been carried out in order to analyze the influence of its length and of its splices' transmission on the device operation, looking for optimization of its linearity and sensibility. The effect of periodic charges, as an emulation of vibrations, has also been studied. The analysis is centered on the frequency dependence of the response. In linear regime (small enough periodic charges), the results obtained are satisfactorily explained by treating the central fiber of the interferometer as a mechanical resonator whose vibration modes coincide with the ones of a cylinder with clamped ends. In nonlinear regime, period doubling and other anharmonic behaviors have been observed.