Open AccessNovel Knob-integrated fiber Bragg grating sensor with polyvinyl alcohol coating for simultaneous relative humidity and temperature measurement
Author(s) -
Guofeng Yan,
Yanhong Liang,
El-Hang Lee,
Sailing He
Publication year - 2015
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.23.015624
Subject(s) - materials science , fiber bragg grating , cladding (metalworking) , optics , coating , optical fiber , relative humidity , refractive index , fiber optic sensor , long period fiber grating , polyvinyl alcohol , grating , temperature measurement , wavelength , optoelectronics , plastic optical fiber , fiber , composite material , physics , quantum mechanics , thermodynamics
A novel high performance optical fiber sensor for simultaneous measurement of relative humidity (RH) and temperature based on our newly designed knob-integrated fiber Bragg grating (FBG) is proposed and experimentally demonstrated. The knob-shaped taper followed by an FBG works as a multifunctional joint that not only excites the cladding modes but also recouples the cladding modes reflected by the FBG back into the leading single mode fiber. Polyvinyl alcohol (PVA) film is plated on the fiber surface by dip-coating technique as a humidity-to-refractive index (RI) transducer, and affects the intensity of reflected cladding modes by way of evanescent fields. By monitoring the intensity and wavelength of the reflected cladding modes, the RH and temperature variance can be determined simultaneously. Experimental results show an RH sensitivity of up to 1.2 dB/%RH within an RH range of 30-95%, which is significantly better than previously reported values. And the temperature sensitivity of 8.2 pm/°Ccould be achieved in the temperature range of 25-60°C. A fast and reversible time response has also been demonstrated, enabling to pick up a humidity change as fast as 630 ms. The capability of simultaneous measurement of RH and temperature, the fast response, the reusability and the simple fabrication process make this structure a highly promising sensor for real-time practical RH monitoring applications.