Fiber optic test methods, fiber optic test equipment, and programs
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.
1. An optical fiber test method comprising:
causing a light pulse to be emitted to one end of an optical fiber to be tested;
receiving backscattered light generated by the light pulse;
acquiring a light pulse test waveform of a light intensity of the backscattered light relative to a distance from the one end of the optical fiber to be tested;
calculating a value of a change amount and a randomness value of the light pulse test waveform at a plurality of points, in a longitudinal direction, of the optical fiber to be tested;
comparing the change amount and the randomness value at a plurality of particular points among the plurality of points; and
determining, among the plurality of particular points, a point where the change amount is larger than the randomness value to be a boundary point present in the optical fiber to be tested.
2. The optical fiber test method according to claim 1 , wherein, among the plurality of points, a point where the change amount is greater than a predetermined threshold is defined as a particular point in the plurality of particular points.
3. The optical fiber test method according to claim 1 , wherein the randomness is a dispersion of the light pulse test waveform in a section I from a particular point in the plurality of particular points to the one end side, and
the section I is a value obtained by dividing, to obtain ½, a product of a speed of light c in a vacuum and a width w of the light pulse by a refractive index n of a core of the optical fiber to be tested.
4. An optical fiber test apparatus, comprising:
a light incidence part configured to emit a light pulse to one end of an optical fiber to be tested;
a light reception part configured to receive backscattered light generated by the light pulse; and
an analysis unit configured to
acquire a light pulse test waveform of a light intensity of the backscattered light relative to a distance from the one end of the optical fiber to be tested,
calculate a value of a change amount and a randomness value of the light pulse test waveform at a plurality of points, in a longitudinal direction, of the optical fiber to be tested,
compares the change amount and the randomness value at a plurality of particular points among the plurality of points, and
determines, among the plurality of particular points, a point where the change amount is larger than the randomness value to be a boundary point present in the optical fiber to be tested.
5. The optical fiber test apparatus according to claim 4 , wherein the analysis unit defines a point among the plurality of points where the change amount is greater than a predetermined threshold as a particular point in the plurality of particular points.
6. The optical fiber test apparatus according to claim 4 , wherein the analysis unit determines the dispersion of the light pulse test waveform in a section I from a particular point to the one end side as the randomness, and
the section I is a value obtained by dividing, to obtain ½, a product of a speed of light c in a vacuum and a width w of the light pulse by a refractive index n of a core of the optical fiber to be tested.
7. A non-transitory computer-readable medium having computer-executable instructions that, upon execution of the instructions by a processor of a computer, cause the computer to function as the analysis unit of the optical fiber test apparatus according to claim 4 .