Nippon Telegraph and Telephone Corporation

Ntt Corporation

Nazuki Honda

Daisuke Iida

Yusuke Koshikiya

Hiroyuki Oshida

Atsushi Nakamura

Tatsuya Okamoto

Tomokazu Oda

Yoshifumi Wakisaka

Kazutaka Noto

Keiji Okamoto

A cable test system, an analysis apparatus, a cable test method, and a program are capable of recognizing a sag section of an overhead cable without sending a worker to a site. In some implementations, the cable test system includes an optical fiber vibration distribution measurement apparatus that acquires a vibration distribution waveform of an overhead optical fiber cable to be tested. The vibration distribution waveform being represented in a time domain and a distance domain in a longitudinal direction. The analysis apparatus that calculates a propagation speed of vibrations propagating through the overhead optical fiber cable from the vibration distribution waveform and detects, as a cable sag section, a section of the overhead optical fiber cable in which the propagation speed is equal to or lower than a threshold value.

Overhead optical cable test system and method

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

A vibration detection apparatus is presented which can avoid occurrence of a point where detection sensitivity deteriorates in vibration detection of a scattered light intensity monitor according to optical frequency multiplexing. A multi-dimensional space having as many dimensions as the number of frequencies to be used, causes scattered light intensity change at each optical frequency to correspond to each axis, plots a scattered light signal as a vector on the space, performs linear approximation passing through an origin on the space having a plurality of plotted vector points as original data, and performs vibration detection using a direction vector of an approximate straight line obtained as a result of the approximation.

Vibration detection device and vibration detection method

The present disclosure relates to a frequency modulation amount measuring device that measures an optical spectral shift of scattered light at a position in an optical transmission line, and calculates a frequency modulation amount at the position, using the measured optical spectral shift.

Devices and methods for measuring the amount of frequency modulation

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

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.

Mode field diameter measuring method and mode field diameter measuring 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

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.

Technique for analyzing a spectrum of backscattered light in an optical fiber

An object of the present invention is to provide an immersion detection system and an immersion detection method capable of eliminating module replacement in the occurrence of immersion and simplifying system management. An immersion detection system according to the present invention includes: an immersion detection sensor having two optical fibers connected in series such that end faces of the two optical fibers abut on each other with a predetermined gap; an optical measurer that causes test light with a plurality of wavelengths to enter an optical transmission line having a plurality of the immersion detection sensors connected in series with optical fibers and measures a return loss of the test light at the immersion detection sensor for each of the wavelengths and for each of the immersion detection sensors; and a determiner that averages, for each of the immersion detection sensors, the return losses for the wavelengths and performs threshold determination on the presence or absence of immersion.

Inundation detection system and inundation detection method

An object of the present invention is to provide an optical fiber test method, an optical fiber test apparatus, and a program, capable of detecting a boundary of an optical fiber line facility regardless of a change in a noise amount. A change amount (a differential value) of an OTDR waveform increases toward a distal end due to noise effects, making it difficult to determine a boundary of the optical fiber using the change amount. Therefore, in the present invention, a dispersion of the OTDR waveform, which increases toward a distal end due to noise effects, is also used to determine the boundary of the optical fiber. In other words, in the present invention, the noise amount is expressed by the dispersion, and the dispersion is compared with the change amount such as a differential value as a threshold, to determine the boundary of the optical fiber. For this reason, when noise increases, the threshold increases together with an increase in the change amount, and therefore, the boundary of the optical fiber can be determined regardless of noise.

Fiber optic test methods, fiber optic test equipment, and programs

An object of the present invention is to provide an optical pulse test apparatus and an optical pulse test method that are capable of determining a change in state of an optical fiber connection portion without the need for reference and without being affected by changes in gap interval before and after the change in state. The optical pulse test apparatus according to the present invention is configured to perform an OTDR measurement by using test optical pulses having spectral widths of from several nm to several hundred nm arranged at intervals of several ten nm to several hundred nm, calculate a reflection peak value caused by the Fresnel reflection at the connection portion from the obtained OTDR waveform, and determine a state such as water immersion of the optical fiber connection portion based on the value.

Optical pulse testing device and optical pulse testing method

An object is to provide an optical fiber route search method, an optical fiber route search device, and a program that can efficiently confirm a path of an optical fiber that is installed over a long distance or across a large range. The optical fiber route search method according to the present invention carries out optical measurement that performs distributed measurement of the state of an optical fiber while applying a disturbance to the optical fiber in a portion in which wires of the optical fiber are parallel to each other, branch out, or intersect with each other (a proximity portion), and determines that the position in which the number of singularities (peaks or intensity fluctuations) fluctuates (becomes plural) is the position of the proximity portion from a distribution diagram obtained through the optical measurement.

Optical fiber route search method, optical fiber route search device and program

An object of the present disclosure is to realize water immersion detection that does not require a replacement module, and does not cause any optical loss. The present disclosure relates to a device configured to measure guided acoustic wave Brillouin scattering in a measurement target optical fiber, and detect water immersion of the measurement target optical fiber based on a characteristic around a peak of the guided acoustic wave Brillouin scattering.

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Musashino, Japan

Nazuki Honda