Temperature-independent hygrometry using micromachined photonic crystal fiber
Document Type
Article
Publication Date
1-1-2018
Abstract
An in-fiber Mach–Zehnder interferometer (MZI) is proposed and experimentally demonstrated for relative humidity (RH) and temperature measurements. The MZI is formed by a grapefruit-shaped photonic crystal fiber (G-PCF) cascaded with a short section of multimode fiber that serves as a mode coupler. To enhance sensitivity to humidity, femtosecond laser micromachining was performed to remove a portion of cladding of the G-PCF to expose its core to the ambient medium. The output interference spectrum is fast Fourier transformed to produce a spatial frequency spectrum that describes the intensity composition of the cladding modes in the MZI. In our investigation, it was observed that the interference dip intensity has a sensitivity of −0.077 dB=% RH to the change of RH in the range of 25%–80% RH, whereas the dip wavelength has a temperature sensitivity of ∼3.3 pm∕°C in the range of 25°C–70°C. In addition, the dip intensity was insensitive to temperature. These characteristics have provided convenience in eliminating temperature cross talk and achieving accurate humidity measurement.
Keywords
Atmospheric humidity, Crystal whiskers, Fibers, Fourier series, Multimode fibers, Nonlinear optics, Temperature measurement
Divisions
PHYSICS
Funders
National Natural Science Foundation of China (NSFC) (61077060, 61205080, 61235005, 61327012, 61405160),National High Technology Research and Development Program 863 (2009AA06Z203),Ministry of Education Project of Science and Technology Innovation (Z08119),Ministry of Science and Technology Project of International Cooperation (2008CR1063),Shaanxi Province Project of Science and Technology Innovation (2008ZDGC-14, 2009ZKC01-19),ShaanXi Young Scientist Star Program (2016KJXX-04),Projects of Scientific Research Plan of ShaanXi Education Department (15JK1751),Northwest University (NWU) Young Scientist Support Program (NJ00089),Fellow of the Royal Geographical Society (RGS) (FP002-2013B),University of Malaya (UM) Research Grant (RG326-15AFR)
Publication Title
Applied Optics
Volume
57
Issue
15
Publisher
Optical Society of America