Nippon Telegraph and Telephone Corporation

Ntt Corporation

Tomokazu Oda

Daisuke Iida

Atsushi Nakamura

Hiroyuki Oshida

Tetsuya Manabe

Kunihiro Toge

Hiroshi Takahashi

Nazuki Honda

Yusuke Koshikiya

Yoshifumi Wakisaka

Tatsuya Okamoto

Yuto Sagae

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. The optical fiber test device according to the present invention includes: a light source unitthat allows probe light L, which has a tunable wavelength and is continuous light, to enter one end Tof an optical fiber in a fundamental mode and allows pulsed pump light L, which is shifted to a high frequency side by a frequency at which a Brillouin interaction occurs with respect to the probe light L, to enter the other end Tof the optical fiber in a higher-order mode as a measurement target; and an analysis unitthat acquires, from a light intensity of the probe light Lamplified by the pump light L, a time waveform of an amplification component, calculates a connection loss of the pump light Lat a connection point from a ratio of the amplification components before and after the connection point, acquires a wavelength dependency of the connection loss, detects a maximum value of the connection loss from the wavelength dependency of the connection loss, and sets the maximum value as a maximum loss of the higher-order mode at the connection point.

Optical fiber test method and optical fiber test equipment

An object of the present invention is to provide a Brillouin gain spectrum distribution measuring method and apparatus capable of measuring a BGS, having a line width narrower than usual, in a distributed manner in the longitudinal direction of an optical fiber under test. This measuring apparatus prepares pump light in which a pulse is added to continuous light and probe light of continuous light in which a frequency is shifted from the pump light, makes the probe light incident on one end of the FUT and the pump light incident on the other end, and obtains a time waveform of a component amplified by the pump light pulse of a probe light intensity amplified by the pump light. This measuring apparatus changes an optical frequency difference between the pump light and the probe light, and obtains a time waveform for each optical frequency difference. This measuring apparatus obtains a BGS distribution of the FUT from these time waveforms.

Brillouin gain spectrum distribution measurement method and equipment

An object of the present disclosure is to provide a power coupling coefficient measurement method and a power coupling coefficient measurement device capable of inexpensively and easily measuring a power coupling coefficient. The power coupling coefficient measurement method according to the present disclosure is a power coupling coefficient measurement method for measuring a power coupling coefficient of a multi-core fiber in order to achieve the aforementioned object, and includes: inputting a test light pulse from one end of the multi-core fiber to any one of cores; receiving backscattered light of the core to which the test light pulse is input or any one of the other cores; measuring an intensity distribution of the backscattered light with respect to a distance from the one end of the multi-core fiber; and calculating the power coupling coefficient from the intensity distribution of the backscattered light.

Power coupling coefficient measuring method and power coupling coefficient measuring device

An object of the present disclosure is to provide a few-mode fiber testing method and a few-mode fiber testing device capable of acquiring a loss and inter-mode crosstalk for each mode at a connection point of a few-mode fiber by measurement only from one end of FUT. The few-mode fiber testing method according to the present disclosure includes receiving a test light pulse in a basic mode from one end of an optical fiber under test that is connected in series with few-mode fibers of the same type, measuring an intensity distribution relating to a distance from the one end of backward Brillouin scattering light generated by receiving a test light pulse, obtaining a transmittance of the backward Brillouin scattering light at a connection point of the optical fiber under test from the measured intensity distribution, and calculating a connection loss of the basic mode from the transmittance, calculating a ratio of an axial deviation amount to a mode field radius of the optical fiber under test at the connection point from the calculated connection loss, and calculating a connection loss of a higher-order mode and inter-mode crosstalk between different modes from the calculated ratio.

Several mode fiber test method and several mode fiber test device

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.

Optical fiber measurement system, optical fiber measurement method, control arithmetic device, and program

An optical fiber testing method is presented for measuring the change amount for the wave number k of a Brillouin Frequency Shift ν in stimulated Brillouin scattering generated in the same acoustic mode with respect to each target propagation mode. In this way, the ratio of the change amount measured at each propagation mode is acquired as the group delay ratio between the modes.

Optical fiber evaluation method and optical fiber evaluation apparatus

A light intensity distribution measurement apparatus is presented that is capable of accurately measuring the intensity of light in each mode at each position of an optical fiber through which light is propagated in a plurality of modes. With the light intensity distribution measurement apparatus, a gain coefficient matrix is acquired in advance, which is constituted by Brillouin gain coefficients of propagation modes with predetermined optical frequency differences measured using a reference optical fiber that exhibits the same properties as a measurement-target optical fiber and that does not cause mode coupling, and the intensity distribution of light in each propagation mode in a lengthwise direction of the measurement-target optical fiber is calculated based on the gain coefficient matrix and a difference in light intensity before and after Brillouin amplification of the probe light emitted in a predetermined propagation mode at a predetermined optical frequency difference measured using the measurement-target optical fiber.

Light intensity distribution measurement method and light intensity distribution measurement device

An object of the present disclosure is to provide a method and an apparatus for acquiring curvature and torsion using an inexpensive sensor medium. Disclosed is a measurement apparatus including a fiber ribbon including a plurality of coated fibers arranged in parallel, a strain measurement unit that measures strain amounts of the plurality of coated fibers, and an arithmetic processing unit that calculates curvature and torsion of the fiber ribbon using a strain amount of a coated fiber arranged in a middle portion of the plurality of coated fibers and a strain amount of a coated fiber arranged in a marginal portion of the plurality of coated fibers.

Measuring device and measuring method using tape core wire

This disclosure describes inputting pulsated pump light in a fundamental mode or a first higher-order mode into one end of an optical fiber under test constructed by connecting two optical fibers in series; inputting probe light having an optical frequency difference within a Brillouin frequency shift range with respect to the pump light into the other end of the optical fiber under test in the fundamental mode or the first higher-order mode; measuring a Brillouin gain distribution related to a distance of transmitted light intensity of probe light output from the one end into which the pump light was input; and calculating each inter-modal coupling efficiency at the connection point of the optical fiber under test.

Optical fiber test method and optical fiber test device

An optical fiber loss measurement device includes a unit configured to input pump light at a first frequency in a predetermined mode to a measurement target optical fiber in which a plurality of modes propagate from a first end, and input probe light at a second frequency to which a Brillouin frequency shift is applied to a second end, a Brillouin gain acquisition unit configured to measure an intensity of light output from the first end to acquire Brillouin gains in a longitudinal direction of the measurement target optical fiber using a BOTDA method, and a unit configured to measure a loss in the predetermined mode of the measurement target optical fiber, and the probe light is in a mode in which an electric field distribution in a cross section of the measurement target optical fiber is axisymmetric.

Optical fiber loss measurement device and optical fiber loss measurement method

An environmental property measurement apparatus includes a unit configured to receive probe light in a desired mode from one end of a measurement optical fiber, a unit configured to receive, from the other end of the measurement optical fiber, a light pulse in the desired mode as a pump light pulse with respect to the probe light, the light pulse having a frequency difference corresponding to a Brillouin frequency shift of the measurement optical fiber relative to the probe light on a high frequency side, and a unit configured to receive second probe light having the frequency difference corresponding to the Brillouin frequency shift of the measurement optical fiber relative to the probe light on a low frequency side from the other end of the measurement optical fiber, the second probe light being probe light with respect to the probe light in another mode different from the desired mode.

Environmental characteristic measurement device and environmental characteristic measurement method

An optical test system capable of accurately measuring a loss of each mode at each position of an optical fiber which propagates a plurality of modes is provided. An optical fiber loss measuring apparatus for measuring using an OTDR technique includes a crosstalk suppressing light input unit that inputs light of a different mode different from the predetermined mode, the different mode causing crosstalk to the probe light, to the target optical fiber to be measured through the near end as crosstalk suppressing light at a second frequency obtained by giving a frequency that is equivalent to a Brillouin frequency shift of the predetermined mode to a first frequency, a light separating unit that removes light of the second frequency from light that is output from the target optical fiber to be measured through the near end to separate light of the first frequency, and a propagation mode loss measuring unit that measures an intensity of the separated light to measure a loss of each propagation mode at each position of the target optical fiber to be measured.

Optical device loss measurement apparatus, and optical device loss measurement method

An object is to provide a propagation property analyzing apparatus that can alleviate the influence of an error caused by crosstalk, and accurately evaluate a few-mode optical fiber that multiplexes a plurality of modes, in a distributional and non-destructive manner. Provided is a propagation property analyzing apparatus that analyzes propagation properties of a few-mode optical fiber that multiplexes a plurality of modes, which is an optical fiber under test, in a lengthwise direction thereof, through Brillouin time domain analysis, the propagation property analyzing apparatus including: means for inputting probe light in a desired mode from a distal end of the optical fiber under test; means for inputting a light pulse that is in the desired mode and that has a frequency difference equivalent to a Brillouin frequency shift in the desired mode, relative to the probe light, from a proximal end of the optical fiber under test, as pump light corresponding to the probe light; and means for inputting a light pulse that is in another mode different from the desired mode and that has a frequency difference equivalent to a Brillouin frequency shift in the other mode, relative to the probe light, as secondary probe light corresponding to the probe light, from the proximal end of the optical fiber under test.

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Musashino, Japan

Tomokazu Oda