Superimposed signal detection circuit and optical node equipment

Patent metadata

Field	Value
Publication number	US-9071378-B2
Application number	US-201213447767-A
Country	US
Kind code	B2
Filing date	Apr 16, 2012
Priority date	Jun 27, 2011
Publication date	Jun 30, 2015
Grant date	Jun 30, 2015

Abstract

A superimposed signal detection circuit detects a signal superimposed on an optical signal in a WDM system. The superimposed signal detection circuit includes: an optical filter having wavelength-dependent loss to filter a plurality of optical signals on which a corresponding superimposed signal is superimposed by frequency modulation; a photo detector to convert the plurality of optical signals filtered by the optical filter into an electric signal; and a detector to obtain information indicated by the superimposed signal respectively superimposed on the plurality of optical signals from the electric signal obtained by the photo detector.

First claim

What is claimed is:

1. A superimposed signal detection circuit that detects a signal superimposed on an optical signal in a WDM system, the superimposed signal detection circuit comprising:
an optical filter having wavelength-dependent loss configured to filter a plurality of optical signals on which a corresponding superimposed signal is superimposed by frequency modulation;
a photo detector configured to convert the plurality of optical signals filtered by the optical filter into an electric signal; and
a detector configured to obtain information indicated by the superimposed signal respectively superimposed on the plurality of optical signals from the electric signal obtained by the photo detector, wherein
a transmittance of the optical filter is tilted at and around a center wavelength of respective wavelength channels with respect to wavelength for the respective wavelength channels of at least one of the plurality of optical signals, and
the detector detects a value of the superimposed signal based on a change in power of output light from the optical filter for the respective wavelength channels of at least one of the plurality of optical signals, and
the frequency of the optical signal is modulated according to a value of the superimposed signal and the optical filter is configured to provide different transmittances for respective wavelengths corresponding to frequencies that correspond to respective values of the superimposed signal.

2. The superimposed signal detection circuit according to claim 1 , wherein
a ratio between a free spectral range of the optical filter and a spacing of wavelength channels of the WDM system is expressed by integers.

3. The superimposed signal detection circuit according to claim 1 , wherein
a ratio between a free spectral range of the optical filter and a resolution of a frequency slot width of the WDM system is expressed by integers.

4. The superimposed signal detection circuit according to claim 1 , wherein
a bandwidth of the photo detector is lower than a symbol rate of data signal carried by the optical signal, and higher than half of a modulation rate of the superimposed signal.

5. A superimposed signal detection circuit that detects a signal superimposed on an optical signal in a WDM system, the superimposed signal detection circuit comprising:
an optical filter having wavelength-dependent loss configured to filter a plurality of optical signals on which a corresponding superimposed signal is superimposed by frequency modulation;
a photo detector configured to convert the plurality of optical signals filtered by the optical filter into an electric signal; and
a detector configured to obtain information indicated by the superimposed signal respectively superimposed on the plurality of optical signals from the electric signal obtained by the photo detector, wherein
a transmittance of the optical filter is tilted with respect to wavelength for respective wavelength bands of at least one of the plurality of optical signals, and wherein
the optical filter includes:
a plurality of optical filter elements;
an optical demultiplexer configured to separate a WDM optical signal with respect to wavelength to be guided to the plurality of the optical filter elements, the WDM optical signal including a plurality of optical signals on which corresponding superimposed signal is respectively superimposed by frequency modulation, two or more of the optical filter elements being allocated to each of the optical signals in the WDM optical signal and each of the optical signals being guided to the allocated two or more of the optical filter elements;
a controller configured to control a transmittance of the plurality of optical filter elements; and
an optical combiner configured to combine output optical signals of the plurality of optical filter elements.

6. The superimposed signal detection circuit according to claim 5 , wherein
the controller controls a transmittance of an optical filter element corresponding to a specified wavelength channel in the WDM optical signal to change depending on wavelength, and
the detector detects a superimposed signal superimposed on an optical signal of the specified wavelength channel.

7. Optical node equipment provided in a WDM transmission system, the optical node equipment comprising:
an optical filter having wavelength-dependent loss configured to filter a plurality of optical signals on which a corresponding superimposed signal is superimposed by frequency modulation;
a photo detector configured to convert the plurality of optical signals filtered by the optical filter into an electric signal; and
a detector configured to obtain information indicated by the superimposed signal respectively superimposed on the plurality of optical signals from the electric signal obtained by the photo detector, wherein
a transmittance of the optical filter is tilted at and around a center wavelength of respective wavelength channels with respect to wavelength for the respective wavelength channels of at least one of the plurality of optical signals, and
the detector detects a value of the superimposed signal based on a change in power of output light from the optical filter for the respective wavelength channels of at least one of the plurality of optical signals, and
the frequency of the optical signal is modulated according to a value of the superimposed signal and the optical filter is configured to provide different transmittances for respective wavelengths corresponding to frequencies that correspond to respective values of the superimposed signal.

8. The optical node equipment according to claim 7 , wherein
the optical filter is a wavelength blocker, a wavelength selective switch, a wavelength selective demultiplexer, or a wavelength selective multiplexer.

9. Optical node equipment provided in a WDM transmission system, the optical node equipment comprising:
an optical filter having wavelength-dependent loss configured to filter a plurality of optical signals on which a corresponding superimposed signal is superimposed by frequency modulation;
a photo detector configured to convert the plurality of optical signals filtered by the optical filter into an electric signal; and
a detector configured to obtain information indicated by the superimposed signal respectively superimposed on the plurality of optical signals from the electric signal obtained by the photo detector, wherein
a transmittance of the optical filter is tilted with respect to wavelength for respective wavelength bands of at least one of the plurality of optical signals, and wherein
the optical filter includes:
a plurality of optical filter elements;
an optical demultiplexer configured to separate a WDM optical signal with respect to wavelength to be guided to the plurality of the optical filter elements, the WDM optical signal including a plurality of optical signals on which corresponding superimposed signal is respectively superimposed by frequency modulation, two or more of the optical filter elements being allocated to each of the optical signals in the WDM optical signal and each of the optical signals being guided to the allocated two or more of the optical filter elements;
a controller configured to control a transmittance of the plurality of optical filter elements; and
an optical combiner configured to combine output optical signals of the plurality of optical filter elements.

10. Optical node equipment provided in a WDM transmission system, the optical node equipment comprising:
an optical filter having wavelength-dependent loss configured to filter a plurality of optical signals on which a corresponding superimposed signal is superimposed by

Assignees

• Hoshida Takeshi
• Fujitsu Ltd

Inventors

• Hoshida Takeshi

Classifications

• H04J14/0264

  Multiplex identification or labelling · CPC title

• H04J14/0276

  using pilot tones · CPC title

• H04B2210/074

  using a superposed, over-modulated signal · CPC title

• H04J14/0204

  Broadcast and select arrangements, e.g. with an optical splitter at the input before adding or dropping · CPC title

• H04J14/0258

  Wavelength identification or labelling · CPC title