Polarimetric fibre-optic strain gauge using two-mode highly birefringent fibres

Abstract

Possible strategies of practical fibre-optic strain gauges using polarimetric and polarization sensitive intermodal interferometric responses in different types of two-mode highly birefringent (Hi-Bi) fibres are discussed. Using general Mueller - Stokes polarization analysis practical expressions for the single-mode polarimetric and two-mode interferometric responses are briefly derived and the corresponding visibilities are obtained. A special attention is paid to the influence of temperature in both regimes of operation, including the cross-sensitivity effect. While a temperature compensated solution by means of a splice is used in the single-mode polarimeter, a simultaneous strain-and-temperature measurement is suggested in the bimodal case. The appropriate conditions for such a two-parameter measurement are considered in detail.