Low Temperature Cross-Sensitivity Humidity Sensor Based on a U-Shaped Microfiber Interferometer

A simple and sensitive optical fiber relative humidity (RH) sensor is proposed and demonstrated in this paper. The optical microfiber inter-mode interferometer is fabricated by tapering PM-elliptical core fiber down to micrometer scale in diameter, the coupling mainly occurs between the LP01 and LP11 modes. The microfiber interferometer (MFI) is fixed as U-shape, making it conveniently to measure. The RH changes are determined from the wavelength shift of the interference pattern induced by the evanescent-field interaction. Experimental results show that MFI with a thinner diameter of $4.7~\mu \text{m}$ offers the best RH sensitivity of 114.7 pm/RHU (per relative humidity unit) ranging from 30% to 90% and good linearity between wavelength and RH. The temperature response has also been experimentally studied, and the temperature sensitivity is 7.6 pm/°C from 30 °C to 90 °C, which indicates that this microfiber device possesses a low temperature cross sensitivity. The proposed RH sensor does not need any functional coating, with advantages of compact size and simple fabrication procedure, which make it attractive for several applications.

[1]  Hamzah Arof,et al.  A Study of Relative Humidity Fiber-Optic Sensors , 2015, IEEE Sensors Journal.

[2]  Minghong Yang,et al.  Optical fiber relative-humidity sensor with evaporated dielectric coatings on fiber end-face , 2014 .

[3]  Sailing He,et al.  Novel Knob-integrated fiber Bragg grating sensor with polyvinyl alcohol coating for simultaneous relative humidity and temperature measurement. , 2015, Optics express.

[4]  Sailing He,et al.  Low-cost high-performance fiber-optic pH sensor based on thin-core fiber modal interferometer. , 2009, Optics express.

[5]  Long Jin,et al.  Temperature-Insensitive Humidity Sensor Based on a Silica Fiber Taper Interferometer , 2013, IEEE Photonics Technology Letters.

[6]  Xinyong Dong,et al.  Refractive Index and Temperature Sensor Based on Double-Pass M–Z Interferometer With an FBG , 2014, IEEE Photonics Technology Letters.

[7]  Qida Zhao,et al.  Relative Humidity Sensor Based on Tilted Fiber Bragg Grating With Polyvinyl Alcohol Coating , 2009, IEEE Photonics Technology Letters.

[8]  S. Lacroix,et al.  Tapered-fiber interferometric wavelength response: the achromatic fringe. , 1988, Optics letters.

[9]  Lei Zhang,et al.  Micro/nanofiber optical sensors , 2011 .

[10]  Long Jin,et al.  Bending effect on modal interference in a fiber taper and sensitivity enhancement for refractive index measurement. , 2013, Optics express.

[11]  Xueguang Qiao,et al.  An In-Fiber Mach–Zehnder Interferometer Based on Arc-Induced Tapers for High Sensitivity Humidity Sensing , 2013, IEEE Sensors Journal.

[12]  Jun Zhang,et al.  Tungsten disulfide (WS2) based all-fiber-optic humidity sensor. , 2016, Optics express.

[13]  Li Han Chen,et al.  Sensitivity-enhanced Michelson interferometric humidity sensor with waist-enlarged fiber bitaper , 2014 .

[14]  P. Rastogi,et al.  Relative humidity sensor with optical fiber Bragg gratings. , 2002, Optics letters.

[15]  B. Guan,et al.  High-sensitivity DNA biosensor based on optical fiber taper interferometer coated with conjugated polymer tentacle. , 2015, Optics express.

[16]  L. Alwis,et al.  Analysis of Polyimide-Coated Optical Fiber Long-Period Grating-Based Relative Humidity Sensor , 2013, IEEE Sensors Journal.

[17]  Fauzan Ahmad,et al.  Study of a fiber optic humidity sensor based on agarose gel , 2014 .

[18]  Xueguang Qiao,et al.  An Optical Fiber Fabry–Perot Interferometer Sensor for Simultaneous Measurement of Relative Humidity and Temperature , 2014, IEEE Sensors Journal.

[19]  Jing Zhang,et al.  A fiber Fabry–Perot interferometer based on a PVA coating for humidity measurement , 2013 .

[20]  C. Cordeiro,et al.  Analysis of immersed silica optical microfiber knot resonator and its application as a moisture sensor. , 2014, Applied optics.

[21]  Changyuan Yu,et al.  A simple fiber-optic humidity sensor based on extrinsic Fabry–Perot cavity constructed by cellulose acetate butyrate film , 2013 .

[22]  Minghong Yang,et al.  Novel polyimide coated fiber Bragg grating sensing network for relative humidity measurements. , 2016, Optics express.

[23]  Bai-Ou Guan,et al.  Microfiber Bragg Grating Hydrogen Sensors , 2014, 2014 Asia Communications and Photonics Conference (ACP).

[24]  H. A. Rafaie,et al.  Optical Fiber Relative Humidity Sensor Based on Inline Mach–Zehnder Interferometer With ZnO Nanowires Coating , 2016, IEEE Sensors Journal.

[25]  Kaiming Zhou,et al.  Toward a New Generation of Photonic Humidity Sensors , 2014, Sensors.

[26]  Y. Gong,et al.  Polyimide-coated fiber Bragg grating for relative humidity sensing , 2015 .