Temperature-insensitive photonic crystal fiber interferometer for relative humidity sensing without hygroscopic coating

• Published in: Measurement science & technology Vol. 24; no. 10; pp. 105205 - 1-5
• Main Authors: Noor, M Y Mohd, Kassim, N M, Supaat, A S M, Ibrahim, M H, Azmi, A I, Abdullah, A S, Peng, G D
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.10.2013
• Subjects: Crystal fibers; Detection; Humidity; humidity sensing; interferometer; Interferometers; photonic crystal fiber; Photonic crystals; Relative humidity; Sensors; Thin films
• ISSN: 0957-0233; 1361-6501
• DOI: 10.1088/0957-0233/24/10/105205

A novel photonic crystal fiber (PCF) interferometer RH (relative humidity) sensor is proposed and demonstrated in this paper. The sensor is made from a piece of PCF spliced to standard fibers in transmission mode, which has the advantage that it does not require the use of any hygroscopic thin film or layer. In addition, the all-silica nature of the sensing element means the sensor is insensitive to temperature. The sensor has a humidity sensitivity of 60.3 pm %RH over the range of 60-80% RH and 188.3 pm %RH in the region from 80 to 95% RH. A response time around ∼1 s is observed for a ∼2 cm long section of photonic crystal fiber interferometer (PCFI). The sensor exhibits a very low cross temperature sensitivity of around 0.5 pm/°C. The proposed sensor has potential for high humidity monitoring applications, and temperature compensation is not necessary if such a sensor is operated in normal surrounding atmosphere.