A fast response intrinsic humidity sensor based on an etched singlemode polymer fiber Bragg grating

• A fast response relative humidity sensor system based on etched polymer optical fiber Bragg grating is demonstrated.
• A response time of 4.5 s is observed for a polymer FBG with a cladding diameter of 25 μm.
• The etched POFBG humidity sensor shows an exponential decrease in response time with a decrease in fiber diameter.
• The developed sensor might have potential applications in a range of areas where fast and accurate real time humidity control is required.

A simple, low cost and fast response time intrinsic relative humidity sensor system based on an etched singlemode polymer fiber Bragg (POFBG) is presented in this paper. A macro-bend linear edge filter which converts the humidity induced wavelength shift into an intensity change is used as the interrogation technique. The singlemode POFBG is etched to micro-meters in diameter to improve the response time of the humidity sensor. A response time of 4.5 s is observed for a polymer FBG with a cladding diameter of 25 μm. The overall sensor system sensitivity was 0.23 mV/%RH. The etched POFBG humidity sensor shows anexponential decrease in response time with a decrease in fiber diameter. The developed sensor might have potential applications in a wide range of applications where fast and accurate real time humidity control is required.