Highly sensitive temperature sensor based on cascaded polymer-microbubble cavities by employing a subtraction between reciprocal thermal responses

A miniature, robust, and highly sensitive optical fiber temperature sensor based on cascaded polymer-microbubble cavities was fabricated by polymer-filling and subsequent heat-curing process. The expansion of polymer cavity results in the compression of microbubble cavity when the sensor is heated. We demodulated the interference spectrum by means of the fast-Fourier transform (FFT) and signal filtering. Since the thermal response of the polymer cavity is positive and that of the microbubble cavity is negative, a high sensitivity of the temperature sensor is achieved by a subtraction between the two reciprocal thermal responses. Experimental results show that the sensitivity of the temperature sensor is as high as 5.013 nm/°C in the measurement range between 20°C and 55°C. Meanwhile, such a sensor has potential for mass production, owing to the simple, nontoxic, and cost-effective process of fabrication.