Relative humidity sensor based on small up-tapered photonic crystal fiber Mach–Zehnder interferometer

Abstract In this paper, a new in-line mode Mach–Zehnder interferometer (MZI) based on photonic crystal fiber (PCF) coated with graphene quantum dots (GQDs) and polyvinyl alcohol (PVA) film for relative humidity (RH) sensing was designed. The MZI was formed by splicing a section of PCF between two sections of single mode fiber (SMF) with two up-tapers. The two up-tapers acted as mode splitter/combiner and were made by fusion tapering technique. The Mach–Zehnder interferometer (MZI) incorporated inter modal interference between core mode and cladding modes of the PCF. The refractive index (RI) and volume of GQDs-PVA film will decrease and expansion with the increase of RH, respectively. By measuring the wavelength shift of the interference pattern, RH measurement could be achieved. Before RH measurement, the external RI was tested experimentally to verify that the interference spectrum shifted to right with the increase of refractive index (RI), and the sensitivity was up to 343.7 nm/RIU. In addition, the RH sensing properties with the different thickness of GQDs-PVA film (2.48 μm, 3.72 μm, 4.45 μm, 5.96 μm, 7.42 μm, 8.17 μm) were also investigated experimentally, and the corresponding sensitivity were -0.0901 nm/%RH, −0.0797 nm/%RH, -0.0337 nm/%RH, 0.0586 nm/%RH, 0.0539 nm/%RH, 0.0313 nm/%RH, respectively. The measurement result revealed that different film thickness had different sensitivity and spectrum movement direction. Meanwhile, the sensor had the advantages of simple structure, small size, high sensitivity and low cost. What’s more, the sensor also presents good stability and reversibility of the sensor.

[1]  Limin Tong,et al.  Fiber optic relative humidity sensor based on the tilted fiber Bragg grating coated with graphene oxide , 2016 .

[2]  Xueguang Qiao,et al.  A relative humidity sensing probe based on etched thin-core fiber coated with polyvinyl alcohol , 2015 .

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

[4]  H. Tsai,et al.  High sensitivity of taper-based Mach-Zehnder interferometer embedded in a thinned optical fiber for refractive index sensing. , 2011, Applied optics.

[5]  Yong Zhao,et al.  Simultaneous Measurement of RI and Temperature Based on a Composite Interferometer , 2016, IEEE Photonics Technology Letters.

[6]  Yong Zhao,et al.  One-Step Synthesis of Au/SnO2/RGO Nanocomposites and Their VOC Sensing Properties , 2018, IEEE Transactions on Nanotechnology.

[7]  Tobias Rossmann,et al.  Spectral shift response of optical whispering-gallery modes due to water vapor adsorption and desorption , 2010 .

[8]  Francisco J. Arregui,et al.  Optical fiber humidity sensor based on surface plasmon resonance in the infra-red region , 2009 .

[9]  Yong Zhao,et al.  Applications and developments of on-chip biochemical sensors based on optofluidic photonic crystal cavities. , 2017, Lab on a chip.

[10]  S. Fardindoost,et al.  A new approach to flexible humidity sensors using graphene quantum dots , 2017 .

[11]  W. Peng,et al.  Strain and temperature discrimination by using temperature-independent FPI and FBG , 2018 .

[12]  Long Jin,et al.  High-birefringence microfiber Sagnac interferometer based humidity sensor , 2016 .

[13]  C. R. Biazoli,et al.  Characterisation of a Nafion film by optical fibre Fabry–Perot interferometry for humidity sensing , 2014 .

[14]  S. Buontempo,et al.  Radiation hard humidity sensors for high energy physics applications using polymide-coated Fiber Bragg Gratings sensors , 2011, 2011 IEEE SENSORS Proceedings.

[15]  Manoj M. Varma,et al.  Highly Sensitive Carbon Nanotubes Coated Etched Fiber Bragg Grating Sensor for Humidity Sensing , 2014, IEEE Sensors Journal.

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

[17]  Yunjiang Rao,et al.  Miniature interferometric humidity sensors based on silica/polymer microfiber knot resonators , 2011 .

[18]  Kay Schuster,et al.  Photonic crystal fiber interferometer coated with a PAH/PAA nanolayer as humidity sensor , 2017 .

[19]  Yong Zhao,et al.  Review of salinity measurement technology based on optical fiber sensor , 2018 .

[20]  A. Stefani,et al.  Temperature insensitive hysteresis free highly sensitive polymer optical fiber Bragg grating humidity sensor. , 2016, Optics express.

[21]  Jesús M. Corres,et al.  Recent Developments in Fiber Optics Humidity Sensors , 2017, Sensors.

[22]  Yong Zhao,et al.  Theoretical analysis of high-sensitive seawater temperature and salinity measurement based on C-type micro-structured fiber , 2018 .

[23]  Yong Zhao,et al.  Review on the graphene based optical fiber chemical and biological sensors , 2016 .

[24]  P. Kim,et al.  Dirac charge dynamics in graphene by infrared spectroscopy , 2008, 0807.3780.

[25]  D. Webb,et al.  Humidity responsivity of poly(methyl methacrylate)-based optical fiber Bragg grating sensors. , 2014, Optics letters.

[26]  Jianquan Yao,et al.  Low-temperature-sensitive relative humidity sensor based on tapered square no-core fiber coated with SiO 2 nanoparticles , 2016 .