High-pressure polarimetric sensor using birefringent optical fibres

A novel fiber-optic high-pressure sensor has been developed for a pressure range up to 200 MPa and for a standard range of temperatures. The sensor is based on the effect of polarization coupling between two orthogonally polarized eigenmodes of the highly birefringent, polarization-preserving optical fiber used as a sensing element. When linearly polarized light, is launched into the fiber at an angle of 45° to each of its principal polarization axis, the output signal (monitored in the direction perpendicular to the direction of the major axis of the polarization state of the light exiting from the fiber) is directly dependent on external high pressure. The sensing element was configured inside a high-pressure chamber using a specially designed, fiber-optic lead-through system. Preliminary tests of the sensor show that its sensitivity is far superior to that of currently used solid-state sensors of high pressure. The author discusses principles, construction, and operation of the sensor and its performance under various conditions, including different pressure and temperature coefficients of the output signal