THREE-FUNCTIONAL SENSOR USING POLARIZATION MAINTAINING FIBER

PURPOSE:To detect temperature, pressure and flow velocity with one optical fiber, by transmitting lights with three kinds of wavelengths to temperature, pressure and flow velocity sensors passing through one polarization maintaining fiber once polarized to detect lights reflected from the sensors. CONSTITUTION:Lights with wavelengths lambda1-lambda3 are sent to a synthesizer 2 from light sources 1a-1c and made incident into a polarization/wavelength separator 3. Then, light with the wavelength lambda1 for temperature detection undergoes P polarization, is passed through a polarization maintaining optical fiber 4 to be incident into a temperature sensor crystal 6 and reflected again to be incident into a separator 3 propagating the fiber 4. Light with the wavelength lambda2 for pressure sensor passes through the fiber 4 and is made incident into the separator 3 reflected on a reflection film 7b passing a 1/8 wavelength plate 7a and an elastic crystal 9. In addition, light with the wavelength lambda3 for flow velocity sensor is reflected with a microlens 5b likewise and enters the separator 3. Respective wavelengths are detected with the separator 3 to detect temperature, pressure and flow velocity. Thus, one polarization maintaining fiber performs three functions making it usefully applicable for medical catheter.