Propagation characteristic analysis device and propagation characteristic analysis method

Patent metadata

Field	Value
Publication number	US-11378489-B2
Application number	US-201916975821-A
Country	US
Kind code	B2
Filing date	Feb 26, 2019
Priority date	Feb 28, 2018
Publication date	Jul 5, 2022
Grant date	Jul 5, 2022

Abstract

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.

First claim

The invention claimed is:

1. 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 comprising:
means for inputting probe light in a desired mode from one end of the optical fiber under test;
first optical frequency control means for outputting pump light having a frequency difference equivalent to a Brillouin frequency shift in the desired mode, relative to the probe light;
first light pulse formation means for forming light pulses from the probe light;
second optical frequency control means for outputting second probe light having a frequency difference equivalent to a Brillouin frequency shift in an other mode different from the desired mode, relative to the probe light;
second light pulse formation means for forming light pulses from the second probe light; and
mode selection and multiplexing/demultiplexing means for inputting, from an other end of the optical fiber under test, the light pulses of the probe light in the desired mode and the light pulses of the second probe light in the other mode respectively.

2. The propagation property analyzing apparatus according to claim 1 , wherein the mode selection and multiplexing/demultiplexing means separates a component in the desired mode and a component in the other mode from the probe light that propagates through the optical fiber under test and is output from the other end, and receives the components; and
wherein the propagation property analyzing apparatus further comprises analyzing means for analyzing, in a time domain, Brillouin gain spectra observed for each of components in the respective modes obtained by the mode selection and multiplexing/demultiplexing means, wherein the analyzing means obtains the propagation properties of the few-mode optical fiber at a given point of the optical fiber under test, based on the Brillouin gain spectra for each of components in the respective modes.

3. The propagation property analyzing apparatus according to claim 2 , wherein the analyzing means calculates a mode coupling ratio of the few-mode optical fiber based on a Brillouin gain intensity ratio of the Brillouin gain spectra observed for each of components in the respective modes obtained at the same frequency.

4. The propagation property analyzing apparatus according to claim 1 , wherein the second light pulse formation means stops a pulse output at incident time t 1 of the light pulses of the pump light.

5. The propagation property analyzing apparatus according to claim 2 , wherein the second light pulse formation means stops a pulse output at incident time t 1 of the light pulses of the pump light.

6. A propagation property analyzing method for analyzing 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 method comprising the steps of: inputting probe light in a desired mode from one end of the optical fiber under test;
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 an other end of the optical fiber under test, as pump light corresponding to the probe light; and
inputting a light pulse that is in an other 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 other end of the optical fiber under test.

Assignees

• Nippon Telegraph & Telephone

Inventors

• Takahashi Hiroshi
• Oda Tomokazu
• Toge Kunihiro
• Manabe Tetsuya

Classifications

• H04J14/04

  Mode multiplex systems · CPC title

• G01M11/0285 Primary

  by measuring material or chromatic transmission properties (G01M11/0292 takes precedence) · CPC title

• H04B10/073 Primary

  using an out-of-service signal (H04B10/071 takes precedence) · CPC title

• G01M11/39

  in which light is projected from both sides of the fiber or waveguide end-face · CPC title

• H04B10/2581

  Multimode transmission · CPC title