Title :
LPG-Based PVA Coated Sensor for Relative Humidity Measurement
Author :
Venugopalan, T. ; Yeo, Teck L. ; Sun, Tong ; Grattan, Kenneth T V
Author_Institution :
Sch. of Eng. & Math. Sci., City Univ., London
fDate :
7/1/2008 12:00:00 AM
Abstract :
A long period grating (LPG) coated with polyvinyl alcohol has been developed and evaluated through exposure to a range of relative humidity (RH) levels (from 33%RH to 97%RH). The conditions for the creation of the sensor probes are described and the response of the device in terms of changes in the resonance loss of several of the spectral loss bands has been monitored. In order to make comparative measurements, a noncoated LPG was exposed to various known refractive index (RI) conditions and the grating response was monitored, analyzed and the results evaluated. This is then related to the change in RH when the sensor is exposed to various RH levels, as the coating RI changes, leading to the change in resonance loss. The PVA coated LPG sensor is showing a relatively fast response time of ~ 80 s to reach 97%RH from 33%RH and inducing ~ 2 dB change in transmission of resonance loss band.
Keywords :
diffraction gratings; fibre optic sensors; humidity sensors; optical fibre losses; polymer films; refractive index; PVA coated sensor; grating response; long period grating; polyvinyl alcohol; refractive index; relative humidity measurement; resonance loss; sensor probes; spectral loss bands; Coatings; Condition monitoring; Delay; Gratings; Humidity measurement; Lead; Probes; Refractive index; Resonance; Sensor phenomena and characterization; Humidity; long period grating (LPG); optical fiber; polyvinyl alcohol (PVA); sensors;
Journal_Title :
Sensors Journal, IEEE
DOI :
10.1109/JSEN.2008.926524
