Ultra-Sensitive Fiber-Optic Temperature Sensor Consisting of Cascaded Liquid-Air Cavities Based on Vernier Effect

A temperature sensor consisting of cascaded liquid-air cavities based on Vernier effect was proposed. The cascaded liquid-air cavities were fabricated simply by partially filling a section of silica capillary tube (SCT) with dimethyl silicone oil (DSO). One opening of the SCT was spliced to the single mode fiber, and the other opening was sealed by the UV glue. The Vernier effect could be generated when the optical paths of liquid-air cavities are close to each other. More importantly, as the lengths of the two cavities change synchronously and complementarily along with the thermal shift of the liquid-air interface, the sensitivity of the sensor can be further improved by about 1.7 times on the basis of ordinary Vernier effect. The actual temperature sensitivity of the proposed sensor around 35 °C reaches as high as 39.21 nm/ °C, which makes the sensor more competitive in medical and pharmaceutical fields.