Titanium dioxide nanoparticle based optical fiber humidity sensor with linear response and enhanced sensitivity.

An optical fiber humidity sensor employing an in-house scaled TiO2-nanoparticle doped nanostructured thin film as the fiber sensing cladding and evanescent wave absorption is reported. The main objective of the present work is to achieve a throughout-linear sensor response with high sensitivity, possibly over a wide dynamic range using the simplest possible sensor geometry. In order to realize this, first, the nanostructured sensing film is synthesized over a short length of a centrally decladded straight and uniform optical fiber and then a comprehensive experimental investigation is carried out to optimize the design configuration/parameters of the nanostructured sensing film and to achieve the best possible sensor response. Much improved sensitivity of 27.1 mV/%RH is observed for the optimized sensor along with a throughout-linear sensor response over a dynamic range as wide as 24% to 95%RH with an average response time of 0.01 s for humidification and 0.06 s for desiccation. In addition, the sensor exhibits a very good degree of reversibility and repeatability.

[1]  G. A. Parks,et al.  Electrical conductivity of silica gel in the presence of adsorbed water , 1968 .

[2]  Harianto Rahardjo,et al.  Humidity sensing using plastic optical fibers , 2004 .

[3]  A. Gaston,et al.  Evanescent wave optical-fiber sensing (temperature, relative humidity, and pH sensors) , 2003 .

[4]  T. L. Yeo,et al.  Characterisation of a polymer-coated fibre Bragg grating sensor for relative humidity sensing , 2005 .

[5]  Masayuki Morisawa,et al.  A plastic optical fibre sensor for real-time humidity monitoring , 2003 .

[6]  Z. M. Rittersma,et al.  Recent achievements in miniaturised humidity sensors—a review of transduction techniques , 2002 .

[7]  Hiroyuki Sasaki,et al.  A humidity sensor based on a hetero-core optical fiber , 2010 .

[8]  Mohd Nasir Taib,et al.  Extending the range of a fibre-optic relative-humidity sensor , 1997 .

[9]  Kefa Cen,et al.  Low-cost relative humidity sensor based on thermoplastic polyimide-coated fiber Bragg grating , 2007 .

[10]  F. Mitschke.  Fiber-optic sensor for humidity. , 1989, Optics letters.

[11]  Sunil K. Khijwania,et al.  Fiber optic evanescent field absorption sensor with high sensitivity and linear dynamic range , 1998 .

[12]  F. Arregui,et al.  Optical fiber humidity sensor based on a tapered fiber coated with agarose gel , 2000 .

[13]  A. Vijayan,et al.  Optical fibre based humidity sensor using Co-polyaniline clad , 2008 .

[14]  Sunil K. Khijwania,et al.  An evanescent-wave optical fiber relative humidity sensor with enhanced sensitivity , 2005 .

[15]  J. André,et al.  Thermodynamic Properties of Adsorbed Water Molecules and Electrical Conduction in Montmorillonites and Silicas , 1965 .

[16]  Kimihiro Adachi,et al.  A novel fiber-optic gas-sensing configuration using extremely curved optical fibers and an attempt for optical humidity detection , 1998 .

[17]  Harianto Rahardjo,et al.  High relative humidity measurements using gelatin coated long-period grating sensors , 2005 .

[18]  T. L. Yeo,et al.  Fibre-optic sensor technologies for humidity and moisture measurement , 2008 .

[19]  Ignacio R. Matias,et al.  A fibre optic humidity sensor based on a long-period fibre grating coated with a thin film of SiO2 nanospheres , 2009 .

[20]  Sunil K. Khijwania,et al.  Fiber optic evanescent field absorption sensor: Effect of fiber parameters and geometry of the probe , 1999 .

[21]  A. Álvarez-Herrero,et al.  High-sensitivity sensor of low relative humidity based on overlay on side-polished fibers , 2002, Proceedings of IEEE Sensors.

[22]  Min Zhang,et al.  Long-Period Grating Relative Humidity Sensor With Hydrogel Coating , 2007, IEEE Photonics Technology Letters.

[23]  F. Arregui,et al.  Sensitivity optimization of tapered optical fiber humidity sensors by means of tuning the thickness of nanostructured sensitive coatings , 2007 .