Fourier Analysis Applied on MZI Transmission Spectrum for Refractive Index Measurement

An approach for surrounding refractive index (SRI) measurement is proposed and demonstrated using all fiber Mach-Zehnder interferometer (MZI) formed by fusion splicing a short section of thin-core fiber between two sections of single-mode fibers with lateral offsets. The transmission spectrum of the...

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Bibliographic Details
Published in:IEEE photonics technology letters 2015-03, Vol.27 (6), p.658-660
Main Authors: Fu, Hai-Wei, Yan, Xu, Shao, Min, Li, Huidong, Gao, Hong, Jia, Zhenan, Qiao, Xueguang
Format: Article
Language:English
Subjects:
Cladding
Fibers
Fourier analysis
Fourier transforms
Interference
Inverse
optical fiber applications
optical fiber interference
Optical fiber sensors
Optical fibers
Optical interferometry
Refractive index
Refractivity
Sensors
Temperature measurement
Wavelength measurement
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Summary:An approach for surrounding refractive index (SRI) measurement is proposed and demonstrated using all fiber Mach-Zehnder interferometer (MZI) formed by fusion splicing a short section of thin-core fiber between two sections of single-mode fibers with lateral offsets. The transmission spectrum of the MZI is dominantly formed by the superposition of two cladding modes separately interference with the core mode, which correspond to two frequency components in its fast Fourier transform (FFT) spectrum, respectively. In this letter, the two frequency components are extracted to take the inverse FFT, respectively, thus we can obtain two dual-mode interference (DMI) patterns between the cladding modes and the core mode. As the SRI changes, the shifts of the two DMI patterns with SRI will be observed. Through this way, we can eliminate the influence of multiple interferences and improve the accuracy of the sensor. The approach can also be utilized with other modal interferometric sensors.
ISSN:1041-1135
1941-0174
DOI:10.1109/LPT.2015.2389818