Lab on Fiber: Photopolymer Self-Growing Micro-Cone for Highly Sensitive Temperature and Salinity Detection

A fiber-optic sensor for simultaneously measurement of temperature and salinity of seawater is proposed and demonstrated in this paper. The sensor is fabricated by self-growing a size-controllable UV-photopolymer micro-cone on the fiber facet. The optimal processing process and micro-cone size are obtained through theoretical analysis. This sensor is featured for simple fabrication, low cost and high efficiency, which provides a new lab-on-fiber scheme. And it was experimentally verified that the sensor shows fast responses to both of temperature and salinity of seawater with a high temperature sensitivity of −0.177 nm/°C between 25 °C and 100 °C and a high salinity sensitivity of −0.848 nm/‰ for the salinity range of 3‰ to 12‰. By using the transmission matrix method, simultaneous measurement of temperature and salinity can be realized and the accuracy of sensor detection is verified as well, which enables real-time long-term monitoring of ocean temperature and salinity.