High-pressure polarimetric sensor using birefringent optical fibers

A 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 a highly birefringent, polarization-preserving optical fiber used as a sensing element. When linearly polarized light is launched into such a fiber at 45° to each of its principal axes of polarization, 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 pressure. The sensing element was configured inside a high-pressure chamber using a specially designed fiber-optic lead-through system. This configuration is very flexible and can be easily altered to fit a specific application. Preliminary tests of the sensor show that its sensitivity is far superior to that of currently used solid-state sensors for high pressure. It can also be adjusted readily to a specified pressure range through an appropriate choice of wavelengths and sensor dimensions. Since it is immune to electromagnetic interference and safe in explosive environments, it is expected to find numerous industrial applications