Integrated birefringent-biased pressure and temperature sensor system

Abstract

An integrated optical temperature and pressure sensor system that is birefringently biased. A broad band light source is transmitted via a fiber optic cable having a splitter, a collimator and a polarizer to a first birefringent bias element. The first birefringent element has a partially reflective coating to reflect back a portion of the light signal to the first polarizer to yield a first reflective modulated light that consists of temperature information irrespective of external forces. The non-reflected light continues to a second birefringent bias element. The second birefringent crystal provides additional birefringent bias to the light wave before the light wave enters an isotropic pressure sensor media. An external pressure applied to the sensor causes the light to experience stress-induced birefringence. The sensor comprises a highly reflective surface which redirects the light back through the sensor, both bias crystals and the polarizer to yield a second reflective modulated light spectrum. The splitter which directs a combined light spectrum comprising a portion of each reflected light spectrum to an opto-electronic interface where the intensity vs. wavelength signal is extracted by a CPU. The CPU performs a Fourier transform on the signal to reveal a first phase term at a selected frequency that relates to the temperature of the system and a second phase term at a different selected frequency that relates to the temperature of the system and the externally applied pressure on the sensor. Subtracting out the temperature term from the temperature and pressure term provides the pressure value.