Common mode rejection ratio measurement device for coherent optical receiver, and measurement method

Patent metadata

Field	Value
Publication number	US-10608748-B2
Application number	US-201716080661-A
Country	US
Kind code	B2
Filing date	Feb 23, 2017
Priority date	Feb 29, 2016
Publication date	Mar 31, 2020
Grant date	Mar 31, 2020

Abstract

To provide a method and device capable of easily measuring the CMRR vs. frequency characteristics of an optical receiver. Light having a measurement frequency (ω [hz]) is split into two different paths, and a first optical two-tone signal, which is signal light and has a frequency difference (ω−Δω [hz]), and a second optical two-tone signal, which is local light and has a frequency difference (ω+Δω [hz]), are obtained and input into a coherent receiver to be measured, wherein electrical signals output from the receiver are measured to obtain both the ratio of the intensity of a signal component having the frequency ω−Δω [hz] to the intensity of a signal component having the frequency ω [hz], which corresponds to the CMRR on the signal light side, and the ratio of the intensity of a signal component having the frequency ω+Δω [hz] to the intensity of the signal component having the frequency ω [hz], which corresponds to the CMRR on the local light side.

First claim

The invention claimed is:

1. A common mode rejection ratio measurement device ( 1 ) for a coherent optical receiver at a measurement frequency (ω [Hz]), comprising:
a branch part ( 5 ) that branches light having the measurement frequency (ω [Hz]) from a laser light source ( 3 ) to obtain a first branched light and a second branched light;
a first optical two-tone generator ( 7 ) that receives the first branched light branched by the branch part ( 5 ), and generates a first optical two-tone signal which is a signal light;
a second optical two-tone generator ( 9 ) that receives the second branched light branched by the branch part ( 5 ), and generates a second optical two-tone signal which is locally generated light; and
an electrical signal measurement device ( 13 ) that measures and analyzes an output electrical signal outputted from a coherent optical receiver ( 11 ) that is a subject for measurement of common mode rejection ratio (CMRR); wherein:
the first optical two-tone signal has a frequency difference (ω−Δω [Hz]) that is lower than the measurement frequency;
the second optical two-tone signal has a frequency difference (ω+Δω [Hz]) that is higher than the measurement frequency; and
the electrical signal measurement device ( 13 ) has a function of obtaining the common mode rejection ratio (CMRR) on the signal light side from an intensity ratio of an intensity I ω of an electrical signal corresponding to a frequency ω [Hz] outputted as a differential component of the first optical two-tone signal which is the signal light and the second optical two-tone signal which is a locally generated light, and an intensity I ω−Δω of an electrical signal corresponding to a frequency (ω−Δω [Hz]) of only the first optical two-tone signal which is the signal light;
wherein the method further includes a step of repeatedly changing the measurement frequency, and obtaining a frequency characteristic of the common mode rejection ratio (CMRR) corresponding to frequency range of change.

2. A common mode rejection ratio measurement device for a coherent optical receiver according to claim 1 ,
wherein the electrical signal measurement device ( 13 ) further comprises a function of obtaining the common mode rejection ratio (CMRR) on the locally generated light side from the intensity ratio of the intensity I ω of the electrical signal corresponding to the frequency ω [Hz] outputted as the differential component of the first optical two-tone signal which is the signal light and the second optical two-tone signal which is locally generated light, and the intensity I ω+Δω of an electrical signal corresponding to the frequency difference (ω+Δω [Hz]) of only the second optical two-tone signal which is the locally generated light.

3. A method for obtaining common mode rejection ratio for a coherent optical receiver, including:
a step of branching light having the measurement frequency (ω [Hz]) from a laser light source ( 3 ), and obtaining a first branched light and a second branched light;
a step of receiving the first branched light and generating a first optical two-tone signal which is signal light, this first optical two-tone signal having a frequency difference (ω−Δω [Hz]) that is lower than the measurement frequency;
a step of receiving the second branched light and generating a second optical two-tone signal which is locally generated light, this second optical two-tone signal having a frequency difference (ω+Δω [Hz]) that is higher than the measurement frequency; and
a step of measuring and analyzing a output electrical signal outputted from a coherent optical receiver ( 11 ) that is a subject of measurement of common mode rejection ratio (CMRR), and obtaining the common mode rejection ratio (CMRR) on the signal light side from an intensity ratio of an intensity I ω of an electrical signal corresponding to a frequency ω [Hz] outputted as a differential component of the first optical two-tone signal which is the signal light and the second optical two-tone signal which is locally generated light, and an intensity I ω−Δω of an electrical signal corresponding to a frequency (ω−Δω [Hz]) of only the first optical two-tone signal which is the signal light;
wherein the method further includes a step of repeatedly changing the measurement frequency, and obtaining a frequency characteristic of the common mode rejection ratio (CMRR) corresponding to frequency range of change.

4. A method for obtaining common mode rejection ratio for a coherent optical receiver according to claim 3 , further including:
a step of measuring and analyzing the output electrical signal; and
a step of obtaining the common mode rejection ratio (CMRR) on the locally generated light side from an intensity ratio of an intensity I ω of an electrical signal corresponding to an frequency ω [Hz] outputted as a differential component of the first optical two-tone signal which is the signal light and the second optical two-tone signal which is locally generated light, and an intensity I ω+Δω of an electrical signal corresponding to a frequency (ω+Δω [Hz]) of only the second optical two-tone signal which is the locally generated light.

Assignees

• Nat Inst Inf & Comm Tech

Inventors

• Inagaki Keizo
• Kawanishi Tetsuya
• Kanno Atsushi
• Yamamoto Naokatsu

Classifications

• H04B10/615

  Arrangements affecting the optical part of the receiver · CPC title

• H04B10/616

  Details of the electronic signal processing in coherent optical receivers · CPC title

• H04B10/614

  comprising one or more polarization beam splitters, e.g. polarization multiplexed [PolMux] X-PSK coherent receivers, polarization diversity heterodyne coherent receivers (H04J14/06 takes precedence) · CPC title

• G01M11/02

  Testing optical properties · CPC title

• H04B10/6151 Primary

  comprising a polarization controller at the receiver's input stage · CPC title