Optical pulse testing method and optical pulse testing device

Patent metadata

Field	Value
Publication number	US-11598692-B2
Application number	US-201917413880-A
Country	US
Kind code	B2
Filing date	Dec 3, 2019
Priority date	Dec 17, 2018
Publication date	Mar 7, 2023
Grant date	Mar 7, 2023

Abstract

An object is to provide an optical pulse test method and an optical pulse test device with which it is possible to measure transmission losses of a basic mode and a first higher-order mode at a connection point at which two-mode optical fibers are connected in series, without switching the mode of input test light.An optical pulse test device according to the present invention inputs a test optical pulse in a basic mode (or a first higher-order mode) from one end of an optical fiber under test, the test optical pulse having such a wavelength that the test optical pulse can propagate in the basic mode and the first higher-order mode, measures intensity distributions of a basic mode component and a first higher-order mode component of return light of the test optical pulse relative to the distance from the one end, finds, from the intensity distributions, losses of the basic mode component and the first higher-order mode component of the return light at a desired connection point of the optical fiber under test, and calculates transmission losses of the basic mode and the first higher-order mode at the connection point based on expressions (8) (or expressions (9)).

First claim

The invention claimed is:

1. An optical pulse test method comprising: a first input procedure of inputting a test optical pulse in a basic mode from one end of an optical fiber under test that is obtained by connecting optical fibers of the same type in series, the test optical pulse having such a wavelength that the test optical pulse can propagate through the optical fiber under test in the basic mode and a first higher-order mode; a first measurement procedure of receiving return light that is generated by the test optical pulse input in the first input procedure and measuring intensity distributions of a basic mode component and a first higher-order mode component of the return light relative to the distance from the one end; a first loss calculation procedure of calculating a loss L 1 of the basic mode component and a loss L 2 of the first higher-order mode component of the return light at a connection point at which the optical fibers of the same type constituting the optical fiber under test are connected in series, from the intensity distributions measured in the first measurement procedure; and a first computation procedure of computing a transmission loss L 01 of the basic mode at the connection point and a transmission loss L 11 of the first higher-order mode at the connection point by substituting the losses L 1 and L 2 calculated in the first loss calculation procedure into first expressions that are simultaneous equations obtained from expressions that express the losses L 1 and L 2 , the transmission loss L 01 of the basic mode, and the transmission loss L 11 of the first higher-order mode by using efficiencies of coupling between the modes at the connection point.

2. An optical pulse test method comprising: a second input procedure of inputting a test optical pulse in a first higher-order mode from one end of an optical fiber under test that is obtained by connecting optical fibers of the same type in series, the test optical pulse having such a wavelength that the test optical pulse can propagate through the optical fiber under test in a basic mode and the first higher-order mode; a second measurement procedure of receiving return light that is generated by the test optical pulse input in the second input procedure and measuring intensity distributions of a basic mode component and a first higher-order mode component of the return light relative to the distance from the one end; a second loss calculation procedure of calculating a loss L 3 of the basic mode component and a loss L 4 of the first higher-order mode component of the return light at a connection point at which the optical fibers of the same type constituting the optical fiber under test are connected in series, from the intensity distributions measured in the second measurement procedure; and a second computation procedure of computing a transmission loss L 01 of the basic mode at the connection point and a transmission loss L 11 of the first higher-order mode at the connection point by substituting the losses L 3 and L 4 calculated in the second loss calculation procedure into second expressions that are simultaneous equations obtained from expressions that express the losses L 3 and L 4 , the transmission loss L 01 of the basic mode, and the transmission loss L 11 of the first higher-order mode by using efficiencies of coupling between the modes at the connection point.

3. The optical pulse test method according to claim 1 , wherein the losses L 1 and L 2 , the transmission loss L 01 of the basic mode at the connection point, and the transmission loss L 11 of the first higher-order mode at the connection point are expressed in decibels, and expressions (C1) are used as the first expressions

L

0
⁢
1

=

L
1

2

⁢

L

1
⁢
1

=

L
2

-

L
1

2

.

(
C1
)

4. The optical pulse test method according to claim 2 , wherein the losses L 3 and L 4 , the transmission loss L 01 of the basic mode, and the transmission loss L 11 of the first higher-order mode are expressed in decibels, and expressions (C2) are used as the second expressions

L
11

=

L
4

2

⁢

L
01

=

L
3

-

L
4

2

.

(
C2
)

5. An optical pulse test device comprising: first input means for inputting a test optical pulse in a basic mode from one end of an optical fiber under test that is obtained by connecting optical fibers of the same type in series, the test optical pulse having such a wavelength that the test optical pulse can propagate through the optical fiber under test in the basic mode and a first higher-order mode; first measurement means for receiving return light that is generated by the test optical pulse input by the first input means and measuring intensity distributions of a basic mode component and a first higher-order mode component of the return light relative to the distance from the one end; first loss calculation means for calculating a loss L 1 of the basic mode component and a loss L 2

Assignees

• Nippon Telegraph & Telephone

Inventors

• Nakamura Atsushi
• Okamoto Keiji
• Oshida Hiroyuki

Classifications

• G01M11/3136

  for testing of multiple fibers · CPC title

• G01M11/31

  with a light emitter and a light receiver being disposed at the same side of a fibre or waveguide end-face, e.g. reflectometers · CPC title

• G01M11/3154 Primary

  Details of the opto-mechanical connection, e.g. connector or repeater · CPC title

• G01M11/3109 Primary

  Reflectometers detecting the back-scattered light in the time-domain, e.g. OTDR · CPC title

• G01M11/3145

  Details of the optoelectronics or data analysis · CPC title