Investigation of Relative Humidity Sensing Using Tapered No-Core Fiber Coated With Graphene Oxide Film

Hua Yang,Yong Qing Fu,Bin Liu,Andrew R Pike,Chaowei Luo,Lichun Ma,Zhen Yi,Sheng-Peng Wan,Xingdao He,Qiang Wu,Juan Liu

doi:10.1109/access.2020.3041507

Abstract

A microfiber interferometer based on a single-mode tapered-no-core single-mode (STNCS) fiber structure coated with a thin layer of graphene oxide (GO) was proposed and demonstrated as a relative humidity (RH) sensor. The STNCS fiber structure has a strong evanescent field, which can sensitively response to changes in the surrounding refractive index. The moisture-sensitive material GO was used to form the film on the no-core fiber by a dip impregnation method. The effects of GO concentration and the tapered waist diameter on RH sensitivity were studied experimentally. The experimental results showed that a thinner waist diameter provides higher RH sensitivity. When the concentration of GO solution is 0.01 mg/mL, the STNCS fiber structure with a waist diameter of 2.9 μm performs better in RH sensing; a high sensitivity of 0.461 nm/%RH in the range of 40-98% was achieved. The sensor has good stability with wavelength fluctuations of ±0.009 nm and ±0.008 nm over 60 mins at RHs of 50% and 80%, respectively. The proposed fiber optic humidity sensor has a high sensitivity over a wide measurement range and offers good stability showing promising potential application in the field of RH sensing.

Highlights

The measurement of relative humidity (RH) is important in the fields of industrial and agricultural production, meteorology, heritage conservation, storage, aerospace, and so on [1]–[3]
Plastic optical fibers coated with hydroxyethyl cellulose [6], a long-period fiber grating coated with a polymer composite film [7], a side-polished fiber coated with TiO2 [8], a photonic crystal fiber coated with agarose and graphene oxide (GO) [9], [10], a no-core fiber (NCF) coated with an agarose-gel film [11], and a small-core fiber coated with poly(ethylene oxide) (PEO) [12]
There is no clear wavelength shift can be observed, indicating that the single-mode tapered-no-core single-mode (STNCS) fiber structure without GO coating is insensitive to RH

Summary

INTRODUCTION

The measurement of relative humidity (RH) is important in the fields of industrial and agricultural production, meteorology, heritage conservation, storage, aerospace, and so on [1]–[3]. Optical fiber sensors coated in a moisture-sensitive film have widely attracted the attention of researchers. H. Yang et al.: Investigation of RH Sensing Using Tapered NCF Coated of graphene and has a larger aspect ratio than other existing moisture-sensitive materials [13]. The effective RI of the GO nano-film changes with the humidity of the surrounding environment, which will result in a change in spectral characteristics of an optical fiber interferometric sensor [15]–[17]. A RH sensor based on a GO coated few-mode fiber MZI shows humidity sensitivity of 0.191 and 0.061 nm/%RH over the RH range of 30-55% and 55-95%, respectively [21]. The proposed optic fiber RH sensor is low cost, flexible, highly sensitive and stable, which implies great potential commercial application in such fields as biomedicine and industrial production

PRINCIPLE AND SIMULATION

RESULTS AND DISCUSSION

CONCLUSION