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arxiv: 1907.07675 · v1 · pith:VHSKEIYMnew · submitted 2019-07-17 · 📡 eess.SP · cs.SY· eess.SY

Distributed vibration sensing based on forward transmission and coherent detection

Yaxi Yan , Changjian Guo , Xiong Wu , Ziqi Lin , Xian Zhou , Faisal Nadeem Khan , Alan Pak Tao Lau , Chao Lu This is my paper

Pith reviewed 2026-05-24 20:25 UTC · model grok-4.3

classification 📡 eess.SP cs.SYeess.SY
keywords distributed vibration sensingforward transmissioncoherent detectionloop-back configurationlong-haul fiberspatial resolutionphase trackinghigh frequency vibration
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The pith

Forward transmission in a loop-back fiber pair with coherent detection localizes vibrations to under 50 m over 1008 km.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper proposes and demonstrates a distributed vibration sensing system that uses forward transmission through a pair of looped-back multi-span fibers and homodyne coherent detection. Phase and state-of-polarization fluctuations caused by vibrations are retrieved, with localization achieved by tracking phase changes along the two fibers. This approach provides high signal-to-noise ratio and allows detection of high-frequency vibrations over ultra-long distances, as shown by experiments achieving over 50 dB SNR and localizing 400 Hz, 1 kHz, and 10 kHz vibrations with less than 50 m resolution across 1008 km of fiber. A sympathetic reader would care because such long-range sensing could support monitoring of extensive fiber networks for faults.

Core claim

By deploying a pair of multi-span optical fibers in a loop-back configuration and using homodyne coherent detection, the phase and SOP fluctuations from vibrations are retrieved while localization is realized by tracking the phase changes along the two fibers, resulting in more than 50 dB sensing SNR and localization of vibrations at frequencies up to 10 kHz with spatial resolution less than 50 m over 1008 km.

What carries the argument

The loop-back configuration of two fibers connected at the far end, with phase tracking along both fibers to localize the vibration point.

Load-bearing premise

Phase changes along the fibers can be attributed mainly to the target vibration rather than to accumulated amplifier noise, nonlinearities, or polarization effects over the full 1008 km distance.

What would settle it

Observation of phase noise levels from EDFAs or nonlinear effects that exceed the vibration-induced phase shift at distances near 1000 km, leading to failed localization.

Figures

Figures reproduced from arXiv: 1907.07675 by Alan Pak Tao Lau, Changjian Guo, Chao Lu, Faisal Nadeem Khan, Xian Zhou, Xiong Wu, Yaxi Yan, Ziqi Lin.

Figure 1
Figure 1. Figure 1: Schematic diagram of the location principle. [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: (a) The configuration of the proposed system; (b) picture of the 1008 km fiber link. PZT: [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: (a), (c), (e) Amplitudes of signals with frequencies of 400 Hz, 1 kHz and 10 kHz during [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: (a), (c), (e) Phase gradient curves of the signals with frequencies of 400 Hz, 1 kHz and [PITH_FULL_IMAGE:figures/full_fig_p006_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: (a) Stable sinusoidal vibration signal. The voltage applied to the PZT is tuned from 1 V [PITH_FULL_IMAGE:figures/full_fig_p007_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: (a) Spectra for different vibration frequencies. Phase information demodulated from the [PITH_FULL_IMAGE:figures/full_fig_p007_6.png] view at source ↗
read the original abstract

A novel ultra-long distributed vibration sensing (DVS) system using forward transmission and coherent detection is proposed and experimentally demonstrated. In the proposed scheme, a pair of multi-span optical fibers are deployed for sensing, and a loop-back configuration is used by connecting the two fibers at the far end. The homodyne coherent detection is used to retrieve the phase and state-of-polarization (SOP) fluctuations caused by a vibration while the localization of the vibration is realized by tracking the phase changes along the two fibers. The proposed scheme has the advantage of high signal-to-noise ratio (SNR) and ultra-long sensing range due to the nature of forward transmission and coherent detection. In addition, using forward rather than backward scattering allows detection of high frequency vibration signal over a long sensing range. More than 50dB sensing SNR can be obtained after long-haul transmission. Meanwhile, localization of 400 Hz, 1 kHz and 10 kHz vibrations has been experimentally demonstrated with a spatial resolution of less than 50 m over a total of 1008 km sensing fiber. The sensing length can be further extended to even trans-oceanic distances using more fiber spans and erbium-doped fiber amplifiers (EDFAs), making it a promising candidate for proactive fault detection and localization in long-haul and ultra-long-haul fiber links.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

3 major / 1 minor

Summary. The manuscript proposes and experimentally demonstrates a novel ultra-long distributed vibration sensing (DVS) system based on forward transmission in a loop-back configuration of two multi-span fibers, using homodyne coherent detection to retrieve phase and SOP fluctuations. Vibration localization is achieved by tracking phase changes along the two fibers. The central claims are >50 dB sensing SNR after long-haul transmission and experimental localization of 400 Hz, 1 kHz, and 10 kHz vibrations with <50 m spatial resolution over a total of 1008 km sensing fiber, with potential extension to trans-oceanic distances using EDFAs.

Significance. If the experimental results hold, the forward-transmission coherent approach would represent a meaningful advance for high-frequency vibration sensing over ultra-long ranges, addressing limitations of backscattering-based methods and enabling applications in proactive fault detection for long-haul fiber links. The loop-back dual-fiber phase tracking is a conceptually simple localization strategy that could be impactful if noise sources are adequately controlled.

major comments (3)
  1. [Abstract] Abstract: The claims of experimental localization with <50 m resolution and >50 dB SNR over 1008 km are stated without reference to any data tables, figures, error bars, processing details, or controls, making independent verification of the central outcomes impossible from the provided text.
  2. [Abstract] Abstract (localization method): The assertion that phase changes tracked along the two fibers can be attributed to the target vibration and localized accurately lacks any quantitative bound, simulation, or measurement addressing accumulated ASE noise from EDFAs, Kerr nonlinear phase shifts, or residual SOP fluctuations over 1008 km; this directly undermines the SNR and resolution claims given the stress-test concern.
  3. [Abstract] Abstract: No description is given of the specific digital signal processing steps, local-oscillator power, or phase-extraction algorithm used in the homodyne coherent receiver, which are load-bearing for reproducing the reported >50 dB SNR after long-haul transmission.
minor comments (1)
  1. [Abstract] The abstract refers to 'a pair of multi-span optical fibers' and 'more fiber spans and EDFAs' without specifying the exact number of spans, span lengths, or EDFA placement used in the 1008 km experiment.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the constructive comments. We address each major comment below.

read point-by-point responses

  1. Referee: [Abstract] Abstract: The claims of experimental localization with <50 m resolution and >50 dB SNR over 1008 km are stated without reference to any data tables, figures, error bars, processing details, or controls, making independent verification of the central outcomes impossible from the provided text.

    Authors: Abstracts are concise summaries and do not include direct references to figures or tables. The supporting experimental results, including SNR measurements exceeding 50 dB, localization with less than 50 m resolution for 400 Hz, 1 kHz and 10 kHz vibrations over 1008 km, along with figures, error bars, and processing details, are provided in the main text and figures of the manuscript. revision: no

  2. Referee: [Abstract] Abstract (localization method): The assertion that phase changes tracked along the two fibers can be attributed to the target vibration and localized accurately lacks any quantitative bound, simulation, or measurement addressing accumulated ASE noise from EDFAs, Kerr nonlinear phase shifts, or residual SOP fluctuations over 1008 km; this directly undermines the SNR and resolution claims given the stress-test concern.

    Authors: The manuscript provides experimental evidence that vibration-induced phase changes are tracked and localized using the dual-fiber loop-back configuration after 1008 km transmission with EDFAs. The achieved SNR >50 dB indicates that ASE, Kerr nonlinearities and SOP fluctuations are sufficiently mitigated. We can add further quantitative noise analysis or simulations in revision if specific requirements are outlined. revision: partial

  3. Referee: [Abstract] Abstract: No description is given of the specific digital signal processing steps, local-oscillator power, or phase-extraction algorithm used in the homodyne coherent receiver, which are load-bearing for reproducing the reported >50 dB SNR after long-haul transmission.

    Authors: The abstract summarizes the overall approach. The digital signal processing steps, local-oscillator power, and phase-extraction algorithm for the homodyne coherent receiver are described in the Experimental Setup and Signal Processing sections of the full manuscript. revision: no

Circularity Check

0 steps flagged

No circularity: experimental demonstration with no derivations or fitted predictions

full rationale

The paper is an experimental demonstration of a DVS system using forward transmission and coherent detection over 1008 km fiber. It reports measured SNR >50 dB and localization of vibrations at 400 Hz, 1 kHz, and 10 kHz with <50 m resolution. No equations, derivations, parameter fitting, or predictions are present in the provided text. The localization method is described as tracking phase changes along the two fibers in loop-back, but this is presented as a direct experimental procedure without any self-referential modeling or reduction to inputs. No self-citations are invoked as load-bearing for any uniqueness theorem or ansatz. The result is self-contained against external benchmarks via direct measurement.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The paper introduces no new free parameters, axioms beyond standard optical fiber and coherent detection assumptions, or invented entities; the contribution is an experimental configuration of established techniques.

axioms (1)
  • domain assumption Standard assumptions of coherent optical detection and low-loss fiber transmission hold over multi-span links with EDFAs.
    Invoked implicitly when claiming high SNR after long-haul transmission and phase retrieval via homodyne detection.

pith-pipeline@v0.9.0 · 5791 in / 1228 out tokens · 26743 ms · 2026-05-24T20:25:18.778095+00:00 · methodology

discussion (0)

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Reference graph

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