| The main research content of this paper is optical fiber humidity sensors.In this paper,we proposed two kinds of humidity-sensitive films and two new interferometric structures.In this paper,a fiber-optic Mach-Zehnder interferometer(MZI)humidity sensor,composed of a pair of waist-enlarged bi-tapers and Carboxy-methyl cellulose(CMC)coating,is proposed.The proposed sensor is linearly responsive to relative humidity(RH)within the humidity range from 70 %RH to 85 %RH,with a maximum sensitivity of-0.8578 dB/%RH with coating thickness of 6.8 ?m.More importantly,humidity sensitivity can be improved by changing the thickness of the CMC film.In this paper,a Michelson interferometer configuration based on thin core fiber(TCF)is presented.The Michelson interferometer(MI)is fabricated by splicing one end of a short segment TCF with a single mode fiber and melting the other end of TCF into a rounded tip.The sensor registered high sensitivity with the RI range of 1.3321 to 1.3823 through wavelength and intensity modification.A carbon nanotubes(CNTs)deposited the Michelson interferometer configuration for refractive index(RI)sensing is presented.The high RI of the CNTs deposited on the surface of the TCF modifies the sensing scheme to that intensity variations.A polyvinyl alcohol(PVA),PVA/CNT,Chitosan were coated on TCF as a relative humidity(RH)sensor,respectively.CNTs makes the sensing scheme enhance intensity variations.In this paper,an optical fiber senor based on Mach-Zehnder interferometer(MZI)is proposed and experimentally demonstrated for the measurement of temperature and refractive index(RI)simultaneously.This structure is composed of a pair of sphericalshape structures and an embedded taper,where the spherical-shape structure excites highorder cladding modes and the taper enhances the penetration depth of evanescent field.Experimental results show that a matrix can be used to achieve the simultaneous measurement of the temperature and RI. |
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