Mode-dependent loss measurement method and measurement device

Patent metadata

Field	Value
Publication number	US-11022523-B2
Application number	US-201815923062-A
Country	US
Kind code	B2
Filing date	Mar 16, 2018
Priority date	Mar 4, 2016
Publication date	Jun 1, 2021
Grant date	Jun 1, 2021

Abstract

A present embodiment relates to a MDL measurement method and the like including a structure for enabling MDL measurement without increasing a processing load. The present embodiment sequentially executes, for N (≥2) spatial modes, light-input operation of inputting light of a predetermined intensity to an arbitrary spatial mode, and intensity measurement operation of measuring an output light intensity of each of the N spatial modes including the arbitrary spatial mode, to generate a transfer matrix relating to transmission loss in an optical fiber as a measurement target, and determine at least a linear value of MDL per unit fiber length by using each component value of the generated transfer matrix.

First claim

The invention claimed is:

1. A mode-dependent loss measurement method for measuring mode-dependent loss of an optical fiber having a first end and a second end opposite to the first end and enabling optical transmission in N spatial modes between which mutual crosstalk occurs, N being equal to or greater than 2,
the mode-dependent loss measurement method comprising:
repeating, for each respective target spatial mode of the N spatial modes light-input operation and intensity measurement operation to generate a transfer matrix including only transmission loss information in the optical fiber from the first end to the second end, the light-input operation inputting light of a predetermined intensity from the first end of the optical fiber to the respective target spatial mode, the intensity measurement operation measuring an intensity of light in each of the N spatial modes including the respective target spatial mode, the light being outputted from the second end of the optical fiber in response to light-input to the respective target spatial mode; and
determining, as a linear value of mode-dependent loss per unit fiber length, a ratio obtained by dividing a maximum value of matrix elements constituting the transfer matrix by a minimum value of the matrix elements, or a ratio obtained by dividing a maximum value of eigenvalues or singular values of the transfer matrix by a minimum value of the eigenvalues or the singular values.

2. The mode-dependent loss measurement method according to claim 1 , further comprising:
multiplying a common logarithm of the linear value by ten to determine a decibel value of the mode-dependent loss per unit fiber length.

3. The mode-dependent loss measurement method according to claim 1 , wherein
the light-input operation includes
operation of inputting light of an intensity P i , from the first end of the optical fiber having a fiber length L i [unit fiber length], to an i-th (i=1, 2, . . . , N) spatial mode as the target spatial mode out of the N spatial modes,
the intensity measurement operation includes
operation of measuring an intensity of light in each of the N spatial modes in which a light intensity of an j-th (j=1, 2, . . . , N) spatial mode is represented by P ji , [mW], the light being outputted from the second end of the optical fiber in response to light-input to the i-th spatial mode, and
the method repeats the light-input operation and the intensity measurement operation for each of the N spatial modes while changing the target spatial mode, to generate a transfer matrix relating to the transmission loss represented by an expression (1) as follows:

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Assignees

• Sumitomo Electric Industries

Inventors

• Hayashi Tetsuya

Classifications

• G02B6/02014 Primary

  Effective area greater than 60 square microns in the C band, i.e. 1530-1565 nm · CPC title

• G01M11/33

  with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face · CPC title

• G02B6/2808

  using a mixing element which evenly distributes an input signal over a number of outputs · CPC title

• G02B6/02

  Optical fibres with cladding {with or without a coating} · CPC title

• G02B6/42

  Coupling light guides with opto-electronic elements · CPC title