Temperature sensor using an optical fiber coupler with a thin film

A temperature sensor was demonstrated and fabricated by coating thermosensitive film around a fiber coupler. Based on the multicladding equivalent method, the coated fiber coupler was simplified to a conventional one. With the high thermo-optical coefficient of organic-inorganic solgel material, a good sensing result was achieved. The range of temperature measured is from -50 to 100 degrees C. The resonant wavelength has a shift of about 25 nm. A sensitivity of 0.17 nm/degrees C is achieved. With the advantages of having a simple structure and being unaffected by the instability of the light source, the proposed fiber coupler temperature sensor will find wide applications.