Sensitive Humidity Sensor Based on a Special Dual-Mode Fiber

A novel humidity sensor based on a specially designed polyimide coated dual-mode fiber (DMF) is presented in this paper. The parameters and index profile of the DMF used in the experiments are specially designed to support only two modes, LP01 and LP02, propagating in the fiber at the operational wavelength, and the interference between these two modes produces a polarization-independent transmission spectrum. An in-line Mach–Zehnder interferometer is constructed by splicing a section of DMF between two pieces of standard single-mode fibers and employed in the detection of the surrounding relative humidity (SRH) of the environment. In the experiments, because the volume of the polyimide film coated on the DMF changes with SRH and thus produces the strain imposed on the DMF section, the interference dips in the transmission spectrum shift monotonically with the increasing SRH. According to the previous research, the strain sensitivities of the DMF used in this paper increase significantly when the peak wavelengths approach the critical wavelength. Therefore, in the experimental results observed, the experimental sensitivity is 153.5 pm/%RH in the SRH range of 30%RH–98%RH, which is over ten times larger than the largest sensitivity (15 pm/%RH) of polyimide-coated fiber Bragg grating reported in the literature. The proposed humidity sensor has advantages of robust, low cost, and ease of fabrication, which suits several practical applications in monitoring the SRH, especially when high sensitivity measurement is required.

[1]  K. Grattan,et al.  Design and performance evaluation of polyvinyl alcohol/polyimide coated optical fibre grating-based humidity sensors. , 2013, The Review of scientific instruments.

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

[3]  Mingshun Jiang,et al.  Optical fibre Fabry–Perot relative humidity sensor based on HCPCF and chitosan film , 2016 .

[4]  Changyu Shen,et al.  Polarization-dependent humidity sensor based on an in-fiber Mach-Zehnder interferometer coated with graphene oxide , 2016 .

[5]  Kenneth T. V. Grattan,et al.  Graphene-Oxide-Coated Long-Period Grating-Based Fiber Optic Sensor for Relative Humidity and External Refractive Index , 2018, Journal of Lightwave Technology.

[6]  Sailing He,et al.  An open-cavity Fabry-Perot interferometer with PVA coating for simultaneous measurement of relative humidity and temperature , 2016 .

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

[8]  S. Janssens,et al.  Investigation of polyimide coated fibre Bragg gratings for relative humidity sensing , 2015 .

[9]  Zhi-mei Qi,et al.  Humidity sensor based on power leakage at resonance wavelengths of a hollow core fiber coated with reduced graphene oxide , 2016 .

[10]  Kenneth T. V. Grattan,et al.  Simultaneous Measurement of Strain and Temperature With a Few-Mode Fiber-Based Sensor , 2018, Journal of Lightwave Technology.

[11]  Yuliya Semenova,et al.  Agarose coated spherical micro resonator for humidity measurements. , 2016, Optics express.

[12]  Agarose Filled Fabry–Perot Cavity for Temperature Self-Calibration Humidity Sensing , 2016, IEEE Photonics Technology Letters.

[13]  Xiaopeng Dong,et al.  Intensity detection scheme of sensors based on the modal interference effect of few mode fiber , 2016 .

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

[15]  G. Cohoon,et al.  SMS Fiber Sensor Utilizing a Few-Mode Fiber Exhibits Critical Wavelength Behavior , 2012, IEEE Photonics Technology Letters.

[16]  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.

[17]  Li Han Chen,et al.  A chitosan-coated humidity sensor based on Mach-Zehnder interferometer with waist-enlarged fusion bitapers , 2017 .

[18]  J. Meunier,et al.  Strain and Temperature Sensing Characteristics of Single-Mode–Multimode–Single-Mode Structures , 2009, Journal of Lightwave Technology.

[19]  Kenneth T. V. Grattan,et al.  Evaluation of the Durability and Performance of FBG-Based Sensors for Monitoring Moisture in an Aggressive Gaseous Waste Sewer Environment , 2017, Journal of Lightwave Technology.

[20]  Wei Zhang,et al.  Enhancing the humidity response time of polymer optical fiber Bragg grating by using laser micromachining. , 2015, Optics express.

[21]  Ming-huang Sang,et al.  Optical relative humidity sensor with high sensitivity based on a polyimide-coated symmetrical metal-cladding waveguide. , 2015, Applied optics.