Abstract: An optical fiber measurement system is presented. The optical fiber measurement system includes a light incident circuit which makes a probe light incident on one end of an optical fiber and makes a secondary probe light and a pump light as an optical pulse incident on the other end of the optical fiber; a light receiver which measures a light intensity of arbitrary one propagation mode in the probe light propagating through the optical fiber; and a control calculation device which sets a propagation mode of the probe light, the secondary probe light, and the pump light, an optical frequency difference of the secondary probe light, and an optical frequency difference of the pump light with respect to the light incident circuit, and calculates loss and crosstalk at each point in a longitudinal direction of the optical fiber from the light intensity measured by the light receiver.

Abstract: The present invention has an object to provide a mode field diameter measurement method enabling easily measuring a mode field diameter in an optical fiber, which is capable of propagating a fundamental mode (LP01 mode) and a first higher order mode (LP11 mode), without using a mode multiplexer, and a measurement device of the mode field diameter measurement method. In a mode field diameter measurement method according to the present invention, an intensity ratio between an LP01 mode and an LP11 mode output from an optical fiber to be tested is changed, a mode field diameter is measured by a variable aperture (VA) method for each intensity ratio, and each mode field diameter is calculated.

Abstract: In order to achieve the above object, a signal processing method according to the present disclosure includes: a calculation step of calculating a phase change at each of points on a medium from a phase of a reflected signal generated by a pulse signal transmitted to the medium, at each of predetermined times; a phase connection step of performing phase connection processing, at each of the predetermined times, on the phase change at each of the points calculated in the calculation step; and a correction step of detecting an outlier using a phase change at each of the points at the same time at which the phase connection processing is performed in the phase connection step, and correcting the outlier, at each of the predetermined times.

Abstract: The present disclosure generates an optical spectrogram, representing a temporal change in frequency characteristics, using a plurality of spectral data measured by an OFDR measurement instrument at different times, and filters the optical spectrogram in both a time direction and a frequency direction.

Abstract: The present disclosure relates to a signal processing device that: acquires a signal obtained by repeatedly injecting a plurality of light pulses with different optical frequencies into an optical fiber, and by performing distributed acoustic sensing-phase (DAS-P); calculates a phase change, caused by vibration applied to a section of the optical fiber, using the acquired signal; removes, from the calculated phase change, a component regarding a repetition period of the same optical frequency of the plurality of light pulses; and calculates the vibration applied to the section of the optical fiber, using a phase change obtained by removing the component regarding the period.

Abstract: The present disclosure provides an underground facility position contrast system S, which includes: a scattered light intensity distribution measurement device 1 for measuring, when an earthquake vibration is applied to an optical fiber F laid underground, a change over time in a scattered light intensity distribution in a longitudinal direction of the optical fiber F; and an underground facility position contrast device 2 for measuring a change over time in a distortion response distribution in the longitudinal direction of the optical fiber F based on the change over time in the scattered light intensity distribution in the longitudinal direction of the optical fiber F, estimating an underground facility state of the optical fiber F based on the change over time in the distortion response distribution in the longitudinal direction of the optical fiber F, and associating the underground facility position of the optical fiber F with a longitudinal distance of the optical fiber F.

Abstract: An object of the present invention is to provide an optical fiber testing apparatus and an optical fiber testing method capable of measuring distance dependency of inter-core crosstalk of a non-coupled multicore fiber at the time of the bidirectional transmission. An optical fiber testing apparatus (301) according to the present invention includes a measurement device (10) which inputs an optical pulse from one end (A) of a non-coupled multicore fiber (50) to one core of the non-coupled multicore fiber (50), and measures a first light intensity of backscattered light output from the one core at one end (A), and inputs a light pulse from one end (A) of the non-coupled multi-core fiber (50) to another core, and measures a second light intensity of the backscattered light output from the one core at one end (A); and a calculator (20) which calculates, from the first light intensity and the second light intensity, inter-core crosstalk distance dependency when bidirectional transmission is performed.

Abstract: A determination device 301 is a determination device that categorizes an installation environment of an optical cable 21, and includes a feature extraction unit 212 that extracts a feature vector at each position of the optical cable 21 from a vibration distribution in a longitudinal direction of the optical cable 21, a calculation unit 219 that calculates a discriminant function at each position of the optical cable 21 from the feature vector and a weight vector corresponding to the installation environment, in need of categorization, of the optical cable 21, and a determination unit 220 that compares the discriminant function with teacher signals representing two states and designates a state of the nearer of the teacher signals as a state of the optical cable 21, at each position of the optical cable 21.

Abstract: An object of the present invention is to provide an optical fiber testing device and an optical fiber testing method capable of acquiring both unidirectional crosstalk and bidirectional crosstalk of an uncoupled multicore fiber in a short time and with a little man-hour.

Abstract: Objects of the present invention are to provide a snow accumulation estimating system and a method for estimating a snow accumulation which enable a snow accumulation to be remotely measured accurately and economically. A snow accumulation estimating system 301 according to the present invention includes: an optical fiber 50 that receives vibration from a random point on snow; a vibration measuring instrument 11 that measures the vibration received by the optical fiber 50 as a distribution in a longitudinal direction of the optical fiber 50; and an analysis processing unit 12 that has, as accumulated data, a relationship between a snow accumulation and the vibration received by the optical fiber 50, compares the distribution measured as measurement data by the vibration measuring instrument 11 with the accumulated data, and estimates a snow accumulation at the random point.

Abstract: The present disclosure aims to reduce a strain of an observed waveform caused by a difference in proportional constant between responses of different optical frequencies of probe light resulting from vibration in a phase OTDR that uses different optical frequencies.

Abstract: An object of the present invention is to provide an optical transmission line test apparatus and a test method capable of measuring a cumulative crosstalk of an optical transmission line in which a plurality of uncoupled multi-core fibers are connected in series from one end side with an OTDR. An optical transmission line test apparatus 301 according to the present invention measures a cumulative crosstalk of an optical transmission line 50 in which a plurality of uncoupled multi-core fibers 50-i are connected in series.

Abstract: In order to achieve the above object, the present invention individually inputs light pulses to a first core and a second core at one end of a non-coupled multicore fiber having a connection portion, and individually acquires OTDR waveforms regarding the first core and the second core, calculates ratios between backscattering intensity regarding the first core and backscattering intensity regarding the second core, at at least two points including one point on one end side with respect to the connection portion and one point on another end side with respect to the connection portion, based on the acquired OTDR waveforms, and calculates a ratio between the calculated ratio on the one end side and the calculated ratio on the another end side.

Abstract: The present disclosure includes a light injecting unit that injects a frequency-swept probe light into one end of an optical fiber targeted for measurement, injects a pump light into the other end of the optical fiber targeted for measurement, with respect to the probe light, and thereby amplifies the probe light in the optical fiber targeted for measurement, a light receiving unit that receives a multiplexed light obtained by multiplexing a local light with the probe light, an interference waveform measurement unit that measures an interference waveform between the probe light and the local light, a fundamental mode time waveform analysis unit that acquires a fundamental mode time waveform of the probe light, based on the interference waveform, and a control calculation unit that calculates losses and crosstalk at loss and crosstalk occurrence points of the optical fiber targeted for measurement, based on the fundamental mode time waveform.

Abstract: The present disclosure relates to a method for measuring inter-core crosstalk of an optical fiber having a plurality of cores, the method including: injecting light into one core of the optical fiber; converting light emitted from each of the cores provided in the optical fiber into parallel light with an angle difference; measuring an intensity distribution of an interference waveform of the parallel light; independently obtaining an interference component between the one core and any core, different from the one core, provided in the optical fiber and a DC component other than the interference component using the interference waveform of the parallel light; and obtaining crosstalk from the one core to any core, different from the one core, using the interference component and the DC component.

Abstract: A device according to the present disclosure: acquires a group delay time difference between eigenmodes, at a specific wavelength, in a coupled two-core fiber; acquires spatial mode dispersion between the eigenmodes, at the specific wavelength, in the coupled two-core fiber; and calculates an average power coupling coefficient between cores, at the specific wavelength, within an entire length of the coupled two-core fiber by using the group delay time difference, the spatial mode dispersion, and a length of the coupled two-core fiber.

Abstract: A signal processing method executed by a signal processing device, includes performing a phase connection process on a position in a space and a phase value at each of a plurality of times, performing outlier correction of a phase value for each position in the space in a predetermined direction of the space at a predetermined time among the plurality of times based on a result of the phase connection process, and correcting a phase value at a time other than the predetermined time for each of correction target positions among positions in the space.

Abstract: The present disclosure relates to a vibration measuring instrument that repeatedly injects a plurality of light pulses with different optical frequencies into an optical fiber, and performs distributed acoustic sensing-phase (DAS-P). In the vibration measuring instrument, light pulses having a waveform with a spectral side lobe smaller than a side lobe of a rectangular wave are used as the plurality of light pulses.

Abstract: An object of the present invention is to provide a sensing system, a sensing method, and an analyzing device using OFDR in which a sensing range of strain/temperature is less likely to be limited by a frequency sweep width. In the sensing method using OFDR, the sensing system according to the present invention employs sequential update, per measurement by one frequency sweep of the probe light, for setting the reference spectrum to the spectrum of an immediately preceding measurement, by which a spectral shift between an n-th measurement and an (n?1)th measurement is obtained, and the spectral shifts individually obtained between the measurements are integrated.

Abstract: An object is to provide an optical fiber test method and an optical fiber test device capable of acquiring a maximum loss of a higher-order mode at a connection point of an optical fiber transmission line through which a plurality of modes propagate.