WO2026018331A1 - Système de traitement d'analyse - Google Patents

Système de traitement d'analyse

Info

Publication number
WO2026018331A1
WO2026018331A1 PCT/JP2024/025618 JP2024025618W WO2026018331A1 WO 2026018331 A1 WO2026018331 A1 WO 2026018331A1 JP 2024025618 W JP2024025618 W JP 2024025618W WO 2026018331 A1 WO2026018331 A1 WO 2026018331A1
Authority
WO
WIPO (PCT)
Prior art keywords
instantaneous frequency
measured
analysis
light
fluctuations
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/JP2024/025618
Other languages
English (en)
Japanese (ja)
Inventor
達也 岡本
大輔 飯田
優介 古敷谷
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NTT Inc
NTT Inc USA
Original Assignee
Nippon Telegraph and Telephone Corp
NTT Inc USA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nippon Telegraph and Telephone Corp, NTT Inc USA filed Critical Nippon Telegraph and Telephone Corp
Priority to PCT/JP2024/025618 priority Critical patent/WO2026018331A1/fr
Publication of WO2026018331A1 publication Critical patent/WO2026018331A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for

Definitions

  • This disclosure relates to technology for analyzing the spectrum of backscattered light from an object under measurement.
  • OFDR Optical Frequency Domain Reflectometry
  • OFDR optical Frequency Domain Reflectometry
  • spectrogram time-series data
  • Non-Patent Document 1 such OFDRs suffer from degradation of spatial resolution due to fiber noise (e.g., acoustics and fiber vibrations) originating from the environment surrounding the optical fiber, making it impossible to achieve the theoretical spatial resolution. This degradation of spatial resolution limits the measurement distance of the OFDR.
  • fiber noise e.g., acoustics and fiber vibrations
  • the measurement distance is limited not only by noise from the OFDR measuring instrument itself, but also by fiber noise caused by the environment in which the object being measured is located, making it difficult to apply OFDR to field environments.
  • fiber noise accumulates the longer the fiber length, making it difficult to apply it to long-distance measurements (for example, measurements of 100 m or more).
  • the present disclosure aims to provide technology that can compensate for the effects of noise caused by the environment in which the object being measured is placed.
  • the analysis device and method disclosed herein employ a technique that analyzes fluctuations in the instantaneous frequency of intensity at a specific point in the longitudinal direction of the object being measured, and compensates for the fluctuations in instantaneous frequency based on the analysis results.
  • the analysis device of the present disclosure includes: A measuring device that irradiates light onto an object to be measured and measures the intensity distribution of scattered light in the object to be measured analyzes fluctuations in instantaneous frequency of intensity at a predetermined point in the longitudinal direction of the object to be measured; The fluctuation of the instantaneous frequency is compensated for based on the analysis result of the fluctuation of the instantaneous frequency.
  • generating a spectrogram showing the change over time of the instantaneous frequency of the intensity at the predetermined point by short-time Fourier transform obtaining a modulation of the instantaneous frequency that causes the fluctuation from the spectrogram; obtaining a phase modulation of the instantaneous frequency by time-integrating the modulation of the instantaneous frequency; Fluctuations in the instantaneous frequency may be compensated for by multiplying the intensity at the predetermined point by a signal having an opposite phase to the phase modulation.
  • the analysis method of the present disclosure includes: Incidentally, light is incident on an object to be measured, and the intensity distribution of scattered light in the object to be measured is measured; Analyzing the fluctuation of instantaneous frequency of intensity at a predetermined point in the longitudinal direction of the object to be measured; The fluctuation of the instantaneous frequency is compensated for based on the analysis result of the fluctuation of the instantaneous frequency.
  • This disclosure makes it possible to compensate for the effects of noise caused by the environment in which the object being measured is placed.
  • FIG. 1 is a diagram illustrating a configuration of an analysis processing system according to a first embodiment of the present disclosure.
  • FIG. 1 is a diagram illustrating the problem of the present disclosure, showing a spectrum in the absence of fiber noise.
  • FIG. 1 is a diagram illustrating the problem of the present disclosure, showing a spectrum in the presence of fiber noise.
  • FIG. 10 is a diagram illustrating the spread of a spectrum. 10 is a graph illustrating a beat signal. 10 is a graph illustrating a reflected light intensity distribution. 10 is a graph illustrating a beat signal at a reflection point. 1 is a graph illustrating a spectrogram. 1 is a graph illustrating beat frequency modulation. 1 is a graph illustrating phase modulation.
  • the analysis processing system according to the first embodiment includes an OFDR measuring instrument 100 and an analysis device 200.
  • the OFDR measuring instrument 100 measures the spectrum of backscattered light reflected or scattered by an optical fiber under test based on the principle of OFDR (Optical Frequency Domain Reflectometry).
  • the analysis device 200 acquires and analyzes the spectral data obtained by the OFDR measuring instrument 100.
  • the analysis device 200 functions as the analysis device of the present disclosure and can be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network.
  • the tunable light source 2 emits frequency-modulated light.
  • the coupler 3-1 splits the light from the tunable light source 2 into reference light and probe light.
  • the probe light split by the coupler 3-1 is incident on the optical fiber 1 under test via the circulator 4.
  • the optical fiber 1 under test is an example of an "object under test.”
  • the object under test is not limited to optical fibers and may be other optical devices.
  • the coupler 3-2 combines the signal light, which is backscattered light from the optical fiber 1 under test, with the reference light split by the coupler 3-1.
  • the balanced optical receiver 5 receives the interference light combined by the coupler 3-2. This interference light has a beat frequency corresponding to the difference in optical path length between the reference light and the probe light.
  • the AD converter 6 converts the output signal from the balanced optical receiver 5 into a digital signal.
  • the analysis device 200 analyzes the digital signal from the AD converter 6.
  • the analysis principle of the analysis device 200 will be described with reference to Figures 2 to 4.
  • the tunable light source 2 oscillates frequency-swept light whose frequency is swept at a constant sweep rate ⁇ .
  • the optical frequency ⁇ ⁇ t.
  • a spectrum with a sharp peak can be obtained by subjecting the beat signal to a fast Fourier transform (FFT).
  • FFT fast Fourier transform
  • This broadening can be large enough to include multiple peaks corresponding to reflection points in the absence of fiber noise, as shown in Figure 4.
  • Figure 4 shows a case where the spectral broadening is large enough to include N peaks corresponding to delays from t0 to tN in the absence of fiber noise. In other words, in the presence of fiber noise, the theoretical spatial resolution cannot be achieved without any processing.
  • This type of spectral broadening occurs because the period of frequency modulation due to fiber noise is short compared to the measurement time of the beat signal. Specifically, if the time width of the fast Fourier transform is sufficiently shorter than the period of frequency modulation, the spectrum will not broaden even if the instantaneous frequency fluctuates from time to time due to fiber noise. On the other hand, if the time width of the fast Fourier transform is longer than the period of frequency modulation, fluctuations in the instantaneous frequency will broaden the spectrum.
  • the analysis device 200 is used to analyze the instantaneous frequency of the beat signal (fiber noise) through time-frequency analysis such as a short-time Fourier transform, and the spectral broadening is compensated for.
  • the analysis processing system of the present disclosure includes: an analysis device 200; an OFDR measuring device 100 that inputs light into an optical fiber 1 and measures the intensity distribution of scattered light in the optical fiber 1; Equipped with.
  • Figs. 5 to 12 show measurement results obtained when fiber noise is simulated by manually shaking the bundled optical fibers 1 under test. Below, a case where beat signals at reflection points at a predetermined distance are compensated for will be described. However, the technology disclosed herein can be used to compensate for beat signals at reflection points at any distance.
  • FIG 5 shows the beat signal obtained by the OFDR measurement device 100.
  • the OFDR measurement device 100 sends this beat signal to the analysis device 200.
  • the analysis device 200 performs a fast Fourier transform on the beat signal to obtain the reflected light intensity distribution (spectrum). As shown in the reflected light intensity distribution, the spectrum broadens near the reflection point.
  • the analysis device 200 uses a bandpass filter 7 to extract beat signals at reflection points from the reflected light intensity distribution.
  • the bandpass filter 7 may extract beat signals at reflection points depending on the distance range over which fluctuation compensation is performed.
  • the "reflection point” referred to in this disclosure may be a single point or any section including that single point.
  • the "reflection point” is an example of a "predetermined point” in this disclosure.
  • the analysis device 200 uses a short-time Fourier transform to obtain a spectrogram of the beat signal at the reflection point.
  • the short-time Fourier transform generates a spectrogram that shows the change in instantaneous frequency of intensity over time at a specified point.
  • the time width of the window function of the short-time Fourier transform may be set shorter than the speed of frequency fluctuations of the fiber noise (the period of frequency modulation).
  • the bandpass filter 7 may be configured to extract beat signals for each point within a specified distance range, perform a short-time Fourier transform on the multiple beat signals, obtain multiple spectrograms, and then perform the following processing.
  • the analysis device 200 analyzes the beat frequency that gives a peak at each time in the spectrogram obtained by short-time Fourier transform (peak analysis) and calculates the beat frequency modulation due to fiber noise. In other words, the instantaneous frequency modulation that caused the fluctuations is obtained from the spectrogram. As shown in Figure 10, the analysis device 200 time-integrates the beat frequency modulation and calculates the phase modulation due to fiber noise. In other words, by time-integrating the instantaneous frequency modulation, the phase modulation of the instantaneous frequency is obtained. In other words, by integrating the fluctuations in the beat frequency calculated in Figure 9 over time, a graph showing the phase change of the beat signal is obtained.
  • the analysis device 200 obtains a beat signal compensated for fiber noise by multiplying the beat signal at the reflection point shown in Figure 7 by a signal that is in the opposite phase to the phase modulation shown in Figure 10.
  • the beat signal shown in Figure 7 does not undergo any phase processing, and therefore contains phase information of the fiber noise. Therefore, as described above, a beat signal compensated for fiber noise can be obtained by multiplying it by a signal that is in the opposite phase to the phase modulation of the fiber noise obtained by processing involving a short-time Fourier transform.
  • the analysis device 200 performs a fast Fourier transform on the beat signal that has been compensated for fiber noise to obtain a reflected light intensity distribution (spectrum) with the fiber noise removed.
  • a reflected light intensity distribution (spectrum) with the fiber noise removed.
  • the analysis device 200 performs a fast Fourier transform on the beat signal that has been compensated for fiber noise to obtain a reflected light intensity distribution (spectrum) with the fiber noise removed.
  • the reflected light intensity distribution by performing the above processing to compensate for fiber noise, it is possible to obtain sharp peaks with reduced spectral broadening.
  • by compensating for fiber noise using the method of this embodiment it is possible to compensate for degradation in spatial resolution and achieve theoretical spatial resolution. Specifically, it is possible to reduce spectral broadening to approximately 625 ⁇ m (1/160 GHz) for 3 dB fiber noise.
  • OFDR can be applied to long-distance measurements. For example, the position of a break point several kilometers away in an optical fiber line can be measured with mm resolution, which can be used to check the number of free ports on a splitter in a remote closure.
  • the analysis processing system according to the second embodiment includes an OFDR measurement device 101 for performing relative distance measurement OFDR and an analysis device 201.
  • the analysis device 201 functions as the analysis device of the present disclosure and can be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network.
  • the OFDR measuring instrument 101 includes a tunable light source 2, a coupler 3, a circulator 4, a pair of balanced optical receivers 5-1 and 5-2, an AD converter 6, an optical delay device 8, an optical 90-degree hybrid 9, and a pair of low-pass filters 10-1 and 10-2.
  • the analyzing device 201 includes a band-pass filter 7, similar to the analyzing device 200 in the first embodiment.
  • the coupler 3 splits the light from the tunable light source 2 into reference light and probe light.
  • the probe light split by the coupler 3 is input to the optical fiber 1 under test via the circulator 4.
  • the reference light split by the coupler 3 is input to the optical delay device 8.
  • the reference light which has been input to the optical delay device 8 and has its delay adjusted, and the signal light, which is backscattered light from the optical fiber 1 under test, interfere in the optical 90-degree hybrid 9.
  • the optical 90-degree hybrid 9 generates an in-phase component I of a beat signal by combining the reference light and the signal light from the optical fiber 1 under test, and inputs this to the balanced optical receiver 5-1.
  • the optical 90-degree hybrid 9 also generates a quadrature component Q of a beat signal by combining the reference light, which has been phase-shifted by 90 degrees, with the signal light from the optical fiber 1 under test, and inputs this to the balanced optical receiver 5-2.
  • the AD converter 6 converts the output signals from the balanced optical receivers 5-1 and 5-2 into digital signals.
  • the analysis device 201 analyzes the digital signals from the AD converter 6.
  • Non-Patent Document 2 by delaying the reference light using an optical delayer 8, it is possible to measure the reflected light distribution centered on a point based on the amount of delay given to the reference light (see Non-Patent Document 2). Furthermore, by increasing the delay of the reference light, it is possible to overcome the short-distance measurement drawback of OFDR and measure remote points.
  • the analysis device 201 is used to analyze the instantaneous frequency of the beat signal (fiber noise) through time-frequency analysis such as a short-time Fourier transform, and the spectral broadening is compensated for.
  • the analysis device 201 of the present disclosure includes: An OFDR measuring instrument 101, which inputs light into an optical fiber 1 and measures the intensity distribution of scattered light in the optical fiber 1, analyzes fluctuations in the instantaneous frequency of the intensity at a predetermined point in the longitudinal direction of the optical fiber 1, Based on the analysis results of the fluctuations in the instantaneous frequency, the fluctuations in the instantaneous frequency are compensated for.
  • An OFDR measuring instrument 101 which inputs light into an optical fiber 1 and measures the intensity distribution of scattered light in the optical fiber 1, analyzes fluctuations in the instantaneous frequency of the intensity at a predetermined point in the longitudinal direction of the optical fiber 1, Based on the analysis results of the fluctuations in the instantaneous frequency, the fluctuations in the instantaneous frequency are compensated for.
  • the analysis processing system of the present disclosure includes: an analysis device 201; an OFDR measuring device 101 that inputs light into the optical fiber 1 and measures the intensity distribution of scattered light in the optical fiber 1; Equipped with.
  • Fig. 14 to Fig. 21 show measurement results when fiber noise is simulated by shaking the bundled optical fibers 1 to be measured by hand.
  • FIG 14 shows the beat signal obtained by the OFDR measuring instrument 101.
  • the OFDR measuring instrument 101 sends this beat signal to the analyzing device 201.
  • the analyzing device 201 performs a fast Fourier transform on the beat signal to obtain the reflected light intensity distribution (spectrum). As shown in the reflected light intensity distribution, the spectrum broadens near the reflection point.
  • the analysis device 201 uses a bandpass filter 7 to extract beat signals at reflection points from the reflected light intensity distribution.
  • the bandpass filter 7 may extract beat signals at reflection points depending on the distance range over which fluctuation compensation is performed.
  • the "reflection point” referred to in this disclosure may be a single point or any section including that single point.
  • the "reflection point” is an example of a "predetermined point” in this disclosure.
  • the analysis device 201 uses a short-time Fourier transform to acquire a spectrogram of either the I or Q component of the beat signal at the reflection point.
  • the short-time Fourier transform generates a spectrogram that shows the change in instantaneous frequency of intensity over time at a specified point.
  • the time width of the window function of the short-time Fourier transform may be set shorter than the speed of frequency fluctuations of the fiber noise (the frequency modulation period).
  • the analysis device 201 may acquire spectrograms of both the I and Q components, but because the I and Q components of the beat signal at any point extracted by the band-pass filter 7 are only 90 degrees out of phase with each other, the spectrograms will have the same waveform.
  • the objective of the present disclosure can be achieved by simply acquiring a spectrogram of either the I or Q component of the beat signal, as described above.
  • the band-pass filter 7 may extract beat signals for each point within a specified distance range, perform a short-time Fourier transform on the multiple beat signals, acquire multiple spectrograms, and then perform the following processing.
  • the analysis device 201 analyzes the beat frequency that gives a peak at each time of the spectrogram obtained by short-time Fourier transform (peak analysis) and calculates the beat frequency modulation due to fiber noise. In other words, the instantaneous frequency modulation that caused the fluctuations is obtained from the spectrogram. As shown in Figure 19, the analysis device 201 time-integrates the beat frequency modulation and calculates the phase modulation due to fiber noise. In other words, by time-integrating the instantaneous frequency modulation, the phase modulation of the instantaneous frequency is obtained. In other words, by integrating the fluctuations in the beat frequency calculated in Figure 18 over time, a graph showing the phase change of the beat signal is obtained.
  • the analysis device 201 obtains a beat signal compensated for fiber noise by multiplying the beat signal at the reflection point shown in Figure 16 by a signal that is in the opposite phase to the phase modulation shown in Figure 19.
  • the beat signal shown in Figure 16 does not undergo any phase processing, and therefore contains phase information of the fiber noise. Therefore, as described above, a beat signal compensated for fiber noise can be obtained by multiplying it by a signal that is in the opposite phase to the phase modulation of the fiber noise obtained by processing involving a short-time Fourier transform.
  • the analyzer 201 performs a fast Fourier transform on the beat signal after compensating for the fiber noise to obtain a reflected light intensity distribution (spectrum) from which the fiber noise has been removed.
  • a reflected light intensity distribution (spectrum) from which the fiber noise has been removed.
  • the analyzer 201 performs a fast Fourier transform on the beat signal after compensating for the fiber noise to obtain a reflected light intensity distribution (spectrum) from which the fiber noise has been removed.
  • a sharp peak with reduced spectral broadening can be obtained.
  • the spectral broadening can be reduced to approximately 40 ⁇ m (2.5 THz) for 3 dB of fiber noise.
  • OFDR can be applied to long-distance measurements. For example, the position of a break point several kilometers away in an optical fiber line can be measured with mm resolution, which can be used to check the number of free ports on a splitter in a remote closure.
  • step S1 the OFDR measuring device of the analysis processing system measures the beat signal by the method explained in the first and second embodiments, and sends it to the analysis device.
  • step S2 the analyzer performs a fast Fourier transform on the beat signal to obtain the reflected light intensity distribution (spectrum).
  • step S3 the analysis device uses a bandpass filter to extract beat signals at the reflection points from the reflected light intensity distribution.
  • step S5 the analysis device analyzes the beat frequency that gives the peak at each time in the spectrogram obtained by short-time Fourier transform (peak analysis) and calculates the beat frequency modulation due to fiber noise.
  • step S6 the analyzer time-integrates the beat frequency modulation and calculates the phase modulation due to fiber noise.
  • step S7 the analysis device multiplies the beat signal at the reflection point acquired in step S3 by a phase modulation that is the opposite of the phase modulation calculated in step S6, thereby acquiring a beat signal that has been compensated for fiber noise.
  • step S8 the analyzer performs a fast Fourier transform on the beat signal that has been compensated for fiber noise to obtain a reflected light intensity distribution (spectrum) with fiber noise removed.
  • the analysis devices 200, 201 of the present invention can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided over a network.
  • the program of the present disclosure is a program that causes a computer to realize each function of the device of the present disclosure, and is a program that causes a computer to execute each procedure of the method executed by the device of the present disclosure.
  • the technology disclosed herein can be applied to the information and communications industry.
  • Optical fiber to be measured 2 Tunable wavelength light source 3, 3-1, 3-2: Coupler 4: Circulator 5, 5-1, 5-2: Balanced photodetector 6: AD converter 7: Bandpass filter 8: Optical delay device 9: Optical 90-degree hybrid 10-1, 10-2: Lowpass filter 100, 101: OFDR measuring device 200, 201: Analysis device

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
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Abstract

Un dispositif d'analyse (200) de la présente invention analyse la fluctuation d'une fréquence instantanée dont l'intensité est mesurée en un point prédéterminé dans le sens longitudinal d'une fibre optique (1), la fluctuation étant mesurée par un instrument de mesure OFDR (100) qui émet de la lumière vers la fibre optique (1) et mesure la distribution d'intensité de la lumière diffusée dans la fibre optique (1), et compense la fluctuation de la fréquence instantanée sur la base du résultat d'analyse concernant la fluctuation de la fréquence instantanée.
PCT/JP2024/025618 2024-07-17 2024-07-17 Système de traitement d'analyse Pending WO2026018331A1 (fr)

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Application Number Priority Date Filing Date Title
PCT/JP2024/025618 WO2026018331A1 (fr) 2024-07-17 2024-07-17 Système de traitement d'analyse

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/JP2024/025618 WO2026018331A1 (fr) 2024-07-17 2024-07-17 Système de traitement d'analyse

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WO2026018331A1 true WO2026018331A1 (fr) 2026-01-22

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000111312A (ja) * 1998-08-04 2000-04-18 Mitsubishi Heavy Ind Ltd 光周波数線形掃引装置及び光周波数線形掃引装置のための変調補正デ―タ記録装置
US20170307475A1 (en) * 2014-11-16 2017-10-26 DSIT Solutions Ltd. Spectrally efficient optical frequency-domain reflectometry using i/q detection
JP7173357B2 (ja) * 2019-08-16 2022-11-16 日本電信電話株式会社 振動分布測定装置および方法
WO2024069867A1 (fr) * 2022-09-29 2024-04-04 日本電信電話株式会社 Dispositif et procédé d'analyse de déformation ou de température de fibre optique

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000111312A (ja) * 1998-08-04 2000-04-18 Mitsubishi Heavy Ind Ltd 光周波数線形掃引装置及び光周波数線形掃引装置のための変調補正デ―タ記録装置
US20170307475A1 (en) * 2014-11-16 2017-10-26 DSIT Solutions Ltd. Spectrally efficient optical frequency-domain reflectometry using i/q detection
JP7173357B2 (ja) * 2019-08-16 2022-11-16 日本電信電話株式会社 振動分布測定装置および方法
WO2024069867A1 (fr) * 2022-09-29 2024-04-04 日本電信電話株式会社 Dispositif et procédé d'analyse de déformation ou de température de fibre optique

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
OKAMOTO TATSUYA; IIDA DAISUKE; KOSHIKIYA YUSUKE; HONDA NAZUKI: "Deployment Condition Visualization of Aerial Optical Fiber Cable By Distributed Vibration Sensing Based On Optical Frequency Domain Reflectometry", JOURNAL OF LIGHTWAVE TECHNOLOGY, IEEE, USA, vol. 39, no. 21, 27 August 2021 (2021-08-27), USA, pages 6942 - 6951, XP011885509, ISSN: 0733-8724, DOI: 10.1109/JLT.2021.3107855 *

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