Orientation-dependant inclinometer based on intermodal coupling of two-LP-modes in a polarization-maintaining photonic crystal fiber.

A reflective optic-fiber orientation-dependant inclinometer, in which a short piece of polarization-maintaining photonic crystal fiber (PM-PCF) is spliced with a lead-in single mode fiber (SMF) without any offset, is proposed and experimentally demonstrated. The hollow holes within the PM-PCF are partly collapsed due to the directional arc-heating splicing and couple two linearly polarized (LP) modes into the downstream PM-PCF. Then two LP-modes are reflected at the end face of PM-PCF and recoupled back into the lead-in SMF again via the collapsed splicing cross section. A well-defined interference pattern is obtained as the result of polarized modes interference. Both orientation and sensitivity of bending is determined unambiguously with this compact PM-PCF configuration.