Precise cavity length control in fiber optic extrinsic Fabry-Perot interferometers

In this paper, a novel method used for Fabry-Perot cavity length's demodulation in high-speed and large scope measurement was proposed. Principle of the method is based on uniqueness of intensity of multiple wavelengths in the scope of Fabry-Perot vibration. This technique offers flexibility of selecting incident wave length and enhances the scope of demodulation of cavity length, compared with that popular triple wave length demodulation. In experiment, multi-wavelength demodulation is demonstrated for measurement of cavity length varying from 110um to 115um and the strain resolution was higher than 0.1um.

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A High-Speed Demodulation Technology of Fiber Optic Extrinsic Fabry-Perot Interferometric Sensor Based on Coarse Spectrum

Sensors ◽

10.3390/s21196609 ◽

2021 ◽

Vol 21 (19) ◽

pp. 6609

Author(s):

Peng Zhang ◽

Ying Wang ◽

Yuru Chen ◽

Xiaohua Lei ◽

Yi Qi ◽

...

Keyword(s):

Real Time ◽

High Speed ◽

Cavity Length ◽

Fiber Optic ◽

Likelihood Estimation ◽

Time Dynamic ◽

Wavelength Division ◽

Broadband Spectrum ◽

Fabry Perot ◽

Interferometric Sensor

A fast real-time demodulation method based on the coarsely sampled spectrum is proposed for transient signals of fiber optic extrinsic Fabry-Perot interferometers (EFPI) sensors. The feasibility of phase demodulation using a coarse spectrum is theoretically analyzed. Based on the coarse spectrum, fast Fourier transform (FFT) algorithm is used to roughly estimate the cavity length. According to the rough estimation, the maximum likelihood estimation (MLE) algorithm is applied to calculate the cavity length accurately. The dense wavelength division multiplexer (DWDM) is used to split the broadband spectrum into the coarse spectrum, and the high-speed synchronous ADC collects the spectrum. The experimental results show that the system can achieve a real-time dynamic demodulation speed of 50 kHz, a static measurement root mean square error (RMSE) of 0.184 nm, and a maximum absolute and relative error distribution of 15 nm and 0.005% of the measurement cavity length compared with optical spectrum analyzers (OSA).

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A Zero-Cross Detection Algorithm for Cavity-Length Interrogation of Fiber-Optic Fabry–Perot Sensors

Sensors ◽

10.3390/s19183868 ◽

2019 ◽

Vol 19 (18) ◽

pp. 3868

Author(s):

Ma ◽

Song ◽

Huang ◽

Guo ◽

Yuan ◽

...

Keyword(s):

Power Density ◽

Cavity Length ◽

Fiber Optic ◽

Spectral Power ◽

Spectral Power Density ◽

Maximum Error ◽

Detection Algorithm ◽

Slow Variation ◽

Fabry Perot ◽

And Performance

A zero-cross detection algorithm was proposed for the cavity-length interrogation of fiber-optic Fabry–Perot (FP) sensors. The method can avoid the inaccuracy of peak determination in the conventional peak-to-peak method for the cavity-length interrogation of fiber-optic FP sensors caused by the slow variation of the spectral power density in peak neighboring regions. Both simulations and experiments were carried out to investigate the feasibility and performance of the zero-cross detection algorithm. Fiber-optic FP sensors with cavity lengths in the range of 150–1000 μm were successfully interrogated with a maximum error of 0.083 μm.

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Elliptical-Fitting Cavity Length Demodulation Algorithm for Compound Fiber-Optic Fabry-Perot Pressure Sensor with Short Cavity

Acta Optica Sinica ◽

10.3788/aos201939.0606001 ◽

2019 ◽

Vol 39 (6) ◽

pp. 0606001

Author(s):

王伟 Wei Wang ◽

唐瑛 Ying Tang ◽

张雄星 Xiongxing Zhang ◽

陈海滨 Haibin Chen ◽

郭子龙 Zilong Guo ◽

...

Keyword(s):

Pressure Sensor ◽

Cavity Length ◽

Fiber Optic ◽

Fabry Perot

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High-Order Harmonic-Frequency Cross-Correlation Algorithm for Absolute Cavity Length Interrogation of White-Light Fiber-Optic Fabry-Perot Sensors

Journal of Lightwave Technology ◽

10.1109/jlt.2019.2948214 ◽

2020 ◽

Vol 38 (4) ◽

pp. 953-960 ◽

Cited By ~ 2

Author(s):

Haibin Chen ◽

Jie Liu ◽

Xiongxing Zhang ◽

Wei Wang ◽

Zhibo Ma ◽

...

Keyword(s):

White Light ◽

Cross Correlation ◽

Cavity Length ◽

Fiber Optic ◽

High Order ◽

Harmonic Frequency ◽

High Order Harmonic ◽

Correlation Algorithm ◽

Fabry Perot

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Self-correlation algorithm in optical frequency domain for cavity length interrogation of fiber-optic Fabry–Perot sensors

Optik ◽

10.1016/j.ijleo.2020.165822 ◽

2021 ◽

Vol 225 ◽

pp. 165822

Author(s):

Liang He ◽

Amei Zhang ◽

Honglai Yan ◽

Lijuan Ma ◽

Xiyuan Wei ◽

...

Keyword(s):

Frequency Domain ◽

Cavity Length ◽

Fiber Optic ◽

Optical Frequency ◽

Correlation Algorithm ◽

Fabry Perot

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Sensitivity-Enhanced Extrinsic Fabry–Perot Interferometric Fiber-Optic Microcavity Strain Sensor

Sensors ◽

10.3390/s19194097 ◽

2019 ◽

Vol 19 (19) ◽

pp. 4097

Author(s):

Zhibo Ma ◽

Shaolei Cheng ◽

Wanying Kou ◽

Haibin Chen ◽

Wei Wang ◽

...

Keyword(s):

Sensitive Element ◽

Cavity Length ◽

Fiber Optic ◽

Strain Sensor ◽

Single Mode ◽

Glass Capillary ◽

Capillary Length ◽

Uv Curable ◽

Strain Measurements ◽

Fabry Perot

This study presents an extrinsic Fabry–Perot interferometric (EFPI) fiber-optic strain sensor with a very short cavity. The sensor consists of two vertically cut standard single-mode fibers (SMFs) and a glass capillary with a length of several centimeters. The two SMFs penetrate into the glass capillary and are fixed at its two ends with the use of ultraviolet (UV) curable adhesives. Based on the use of the lengthy glass capillary sensitive element, the strain sensitivity can be greatly enhanced. Experiments showed that the microcavity EPFI strain sensor with initial cavity lengths of 20 μm, 30 μm, and 40 μm, and a capillary length of 40 mm, can yield respective cavity length–strain sensitivities of 15.928 nm/με, 25.281 nm/με, and 40.178 nm/με, while its linearity was very close to unity for strain measurements spanning a range in excess of 3500 με. Furthermore, the strain–temperature cross-sensitivity was extremely low.

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Absolute Single Cavity Length Interrogation of Fiber-Optic Compound Fabry–Perot Pressure Sensors Through a White Light Non-Scanning Correlation Method

Sensors ◽

10.3390/s19071628 ◽

2019 ◽

Vol 19 (7) ◽

pp. 1628 ◽

Cited By ~ 4

Author(s):

Zilong Guo ◽

Wentao Lv ◽

Wei Wang ◽

Qingqing Chen ◽

Xiongxing Zhang ◽

...

Keyword(s):

Fourier Transform ◽

White Light ◽

Cavity Length ◽

Fiber Optic ◽

Pressure Sensors ◽

Correlation Method ◽

Air Cavity ◽

Basal Cavity ◽

Fabry Perot ◽

Absolute Length

A white light non-scanning correlation interrogation system was proposed and built to interrogate absolute length of the air cavity of fiber-optic compound Fabry–Perot pressure sensors for the extraction of pressure value. By carefully choosing thickness range and tilt angle of the optical wedge used for cavity length matching, correlation interferometric signal of the basal cavity can be naturally filtered out. Based on peak positioning by Fourier transform, bandpass filtering in frequency domain, inverse Fourier transform back to time domain, envelope fitting and zero fringe finding through a gravity center method, cavity length can be determined with an accuracy of 0.04%. The system was used for the interrogation of a fiber-optic compound Fabry–Perot pressure sensor under different pressures. For a pressure range of 0.1~2.9 Mpa, the linear relationship between the air cavity length and the gas pressure imposed was successfully extracted.

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