Dual-mode fiber-optic interferometer: a novel design.

We describe a simple and novel single-arm two-mode fiber interferometer in which the directional couplers and the fiber-grating couplers are replaced with microbends caused by point mechanical squeezing. The interferometer works with incident light in the LP02 mode. While the input microbend couples the LP02 mode to the LP21 mode, the output microbend behaves as an attenuator that is sensitive to the orientation of LP02 –LP21 interference intensity field inside the fiber. The application of this device for measuring the core–cladding refractive-index difference and as an interferometric temperature sensor between 20 and 400 °C is demonstrated.