Ultimate Spatial Resolution Realisation in Optical Frequency Domain Reflectometry with Equal Frequency Resampling

Guo, Zhen; Han, Gaoce; Yan, Jize; Greenwood, David; Marco, James; Yu, Yifei

doi:10.3390/s21144632

Cited by 24 publications

(7 citation statements)

References 28 publications

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“…Conventional zero crossing resampling by auxiliary interferometer is unable to achieve mm-level or μm-level resolution [21]. In our previous study, we proposed an equal frequency resample to suppress such noise for an ultimate theoretical spatial resolution of 12.1 µm [22]. In 𝜙𝜙-OFDR based on differential phase spectrum, the realisation of such a theoretical resolution can be regarded as the baseline, as it makes sure the phase comparison happens at exact the same section during the two-step measurement.…”

Section: Experiments and Resultsmentioning

confidence: 99%

High-resolution Φ-OFDR using phase unwrap and nonlinearity suppression

Guo

Yan

Han

et al. 2023

J. Lightwave Technol.

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Phase-sensitive optical frequency domain reflectometer (𝜙𝜙-OFDR) is investigated to deliver an accurate distributed measurement with high spatial resolution. It is found that random phase noise and quadrant discrimination during phase calculation are the main reasons for the random hopping in 𝜙𝜙-OFDR. By efficiently eliminating random hopping in the phase unwrap and suppressing the laser-induced nonlinear sweep for the theoretical spatial resolution, the proposed 𝜙𝜙-OFDR is proved to be able to decouple the limitation between resolution and accuracy in coherent OFDR (C-OFDR). Distributed strain measurement with 20 mm spatial resolution in 𝜙𝜙-OFDR is obtained and analysed. Measurement with little deviation and uniform sensitivity between applied strain and phase change both validate the efficient noise suppression for extreme resolution measurement. Then the influence of the initial sweep frequency between two times measurements is studied. With a further reduced 800 µm spatial resolution, the proposed 𝜙𝜙-OFDR is able to retain accurate distributed measurement compared to conventional C-OFDR methods. Besides, the computation time of the 𝜙𝜙-OFDR is only 3.2% of the C-OFDR.

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Section: Experiments and Resultsmentioning

confidence: 99%

High-resolution Φ-OFDR using phase unwrap and nonlinearity suppression

Guo

Yan

Han

et al. 2023

J. Lightwave Technol.

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“…where N is the resample point at the equal frequency interval of π; the frequency of resample (F s ) can be expressed as Equation (8).…”

Section: Methodsmentioning

confidence: 99%

“…FSI is based on the Michelson interferometer, and the distance is calculated by the beat frequency caused by the sweeping frequency and phase difference [6,7]. Hence, the precision of FSI in absolute distance measurement will rely much on the tunability of its laser source [8]. However, the hysteric response of piezoelectric (PZT) causes the frequency nonlinear tuning of the external cavity diode laser (ECDL), which makes the phase error of the interferometry signal [9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Phase Unwrapping and Frequency Points Subdivision of the Frequency Sweeping Interferometry Based Absolute Ranging System

Song

Shi

Liu

et al. 2022

Sensors

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Frequency sweeping interferometry (FSI) based absolute distance ranging has high precision and no ranging blind area. It can be used to realize large-scale and non-cooperative target measurement. However, the nonlinear frequency modulation of the laser seriously affects the ranging accuracy. In this manuscript, a measurement method assisted by Hilbert Transform (HT) and Chirp-z Transform (CZT) is proposed, which can realize the phase unwrapping of the beat signal, the length reduction in the delay fiber of auxiliary optical path, and the improvement of the frequency resolution. The narrow-band frequency suitable for HT is further studied. In the experiment, the ranging resolution is 70 μm and the standard deviation is 12.6 μm within a distance of 4005 mm.

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“…Several approaches have been proposed to solve this problem. The first kind of method is frequency sampling by attaching an auxiliary interferometer that generates a clock signal with equal frequency intervals to trigger the data acquisition [27,28]. On the one hand, this method will increase the complexity of the system.…”

Section: Experiments Setupmentioning

confidence: 99%

Enhancing Signal Recognition Accuracy in Delay-Based Optical Reservoir Computing: A Comparative Analysis of Training Algorithms

Zhang,

Luan,

et al. 2024

Electronics

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To improve the accuracy of signal recognition in delay-based optical reservoir computing (RC) systems, this paper proposes the use of nonlinear algorithms at the output layer to replace traditional linear algorithms for training and testing datasets and apply them to the identification of frequency-modulated continuous wave (FMCW) LiDAR signals. This marks the inaugural use of the system for the identification of FMCW LiDAR signals. We elaborate on the fundamental principles of a delay-based optical RC system using an optical-injected distributed feedback laser (DFB) laser and discriminate four FMCW LiDAR signals through this setup. In the output layer, three distinct training algorithms—namely linear regression, support vector machine (SVM), and random forest—were employed to train the optical reservoir. Upon analyzing the experimental results, it was found that regardless of the size of the dataset, the recognition accuracy of the two nonlinear training algorithms was superior to that of the linear regression algorithm. Among the two nonlinear algorithms, the Random Forest algorithm had a higher recognition accuracy than SVM when the sample size was relatively small.

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Ultimate Spatial Resolution Realisation in Optical Frequency Domain Reflectometry with Equal Frequency Resampling

Cited by 24 publications

References 28 publications

High-resolution Φ-OFDR using phase unwrap and nonlinearity suppression

High-resolution Φ-OFDR using phase unwrap and nonlinearity suppression

Phase Unwrapping and Frequency Points Subdivision of the Frequency Sweeping Interferometry Based Absolute Ranging System

Enhancing Signal Recognition Accuracy in Delay-Based Optical Reservoir Computing: A Comparative Analysis of Training Algorithms

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