Reflective fiber optic temperature sensor using silicon thin film

A novel, high-resolution, high-speed fiber-optic temperature sensor for oceanographic applications

“…Instead of forming an ultrathin silicon film (in the order of hundreds of nanometers) by deposition [6] or radio-frequency sputtering [3], we developed a process to introduce much thicker silicon pieces onto the optical fiber tip. UV curable glue was first attached to the endface of a cleaved optical fiber, then the silicon piece was connected to the fiber end through the UV glue after curing.…”

“…As a result, the sensor is able to offer a very high sampling speed. To date, there is few previous work that used silicon as the sensing elements for temperature measurements [3][4][5][6]. Also, the reported temperature resolution and slow response of these sensors are far from meeting the requirements for the oceanographic applications.…”

“…Also, the reported temperature resolution and slow response of these sensors are far from meeting the requirements for the oceanographic applications. In fact, the broad reflection peaks/dips obtained from the ultra-thin silicon film (less than 1 μm in [3,6]) is disadvantageous in terms of achieving high temperature resolution (only 3°C in [6]). By increasing the thickness of silicon, a thermometer realized by mounting an optical fiber against a silicon waveguide which was fabricated on a microelectro-mechanical system (MEMS) device showed a temperature resolution of 0.064 °C [4].…”

High-resolution and fast-response fiber-optic temperature sensor using silicon Fabry-Pérot cavity

“…In addition, silicon-based temperature sensor also potentially has high speed because of the large thermal diffusivity of silicon, which is comparable to many metals (e.g., aluminum and gold) and more than 60 times larger than fused silica. However, to date, only a few papers have reported on the use of silicon as temperature sensing element [10][11][12][13] and the potential of silicon has not been fully explored for high-resolution and high-speed temperature sensing. In [10], the dependence of the absorption of a silicon film on temperature was used for temperature sensing and the sensor showed relatively low temperature resolution of ± 0.12 °C and a long response time on the order of 1 s. A simpler structure with a thin silicon film (thickness < 1 μm) deposited directly on the fiber end through electron-beam evaporation was demonstrated in [11], with a temperature resolution of only 3 °C.…”

“…In [10], the dependence of the absorption of a silicon film on temperature was used for temperature sensing and the sensor showed relatively low temperature resolution of ± 0.12 °C and a long response time on the order of 1 s. A simpler structure with a thin silicon film (thickness < 1 μm) deposited directly on the fiber end through electron-beam evaporation was demonstrated in [11], with a temperature resolution of only 3 °C. The radio-frequency sputtering was applied in [12] to simplify the deposition process. The resolution was mainly limited by the small thickness of the silicon film that led to broad spectral fringes.…”