Passive optical networks and method of configuring transmission wavelengths therein

Patent metadata

Field	Value
Publication number	US-9917671-B2
Application number	US-201214399873-A
Country	US
Kind code	B2
Filing date	Jun 8, 2012
Priority date	May 14, 2012
Publication date	Mar 13, 2018
Grant date	Mar 13, 2018

Abstract

A method of configuring transmission wavelengths in a passive optical network comprising a wavelength selective routing element between first and second locations. The method comprises: at a first location: a. iteratively generating and transmitting a first optical signal at different ones of a plurality of wavelengths until a second optical signal is received at the first location; and then b. ceasing transmission of the first optical signal and then recommencing transmission of the first optical signal at the wavelength being transmitted when the second optical signal was received; and at a second location, remote from the first location: c. waiting until the first optical signal is received at the second location; d. iteratively generating and transmitting the second optical signal at different ones of a plurality of wavelengths until the first optical signal is no longer received at the second location; and e. maintaining generation and transmission of the second optical signal at the wavelength being transmitted when the first optical signal was no longer received.

First claim

The invention claimed is:

1. A method of configuring transmission wavelengths in a passive optical network comprising a wavelength selective routing element between first and second locations, the method comprising:
at the first location:
a. selecting a correct wavelength for transmitting a first optical signal from the first location to the second location by iteratively generating and transmitting the first optical signal at different ones of a plurality of wavelengths until a second optical signal is received at the first location; and then
b. ceasing transmission of the first optical signal for a first time period and then recommencing transmission of the first optical signal at the said selected correct wavelength being transmitted when the second optical signal was received;

and at the second location, remote from the first location:
c. waiting until the first optical signal is received at the second location;
d. selecting a correct wavelength for transmitting a second optical signal from the second location to the first location by iteratively generating and transmitting the second optical signal at different ones of a plurality, N, of wavelengths until the first optical signal is no longer received at the second; and
e. maintaining generation and transmission of the second optical signal at the said selected correct wavelength being transmitted when the first optical signal was no longer received.

2. A method as claimed in claim 1 , wherein in a. the first optical signal is transmitted at each said wavelength for a time period, T 1 , and wherein T 1 is greater than a total time period required to select the correct wavelength for transmitting the second optical signal from the second location to the first location by iteratively generating and transmitting the second optical signal at the different ones of the plurality, N, of wavelengths until the first optical signal is no longer received at the second location.

3. A method as claimed in claim 1 , wherein in a. the first optical signal is iteratively generated and transmitted until a first alarm signal having a first alarm state is received at the first location, indicating that the second optical signal is received, c. comprises waiting until a second alarm signal having a first alarm state is received at the second location, indicating that the first optical signal is received, and in d. the second optical signal is iteratively generated and transmitted until the second alarm signal having a second alarm state is received at the second location, indicating that the first optical signal is no longer received.

4. A method as claimed in claim 3 , wherein each of the first and second alarm signals is a loss of signal alarm signal, and wherein the first alarm state is a loss of signal alarm OFF state and the second alarm state is a loss of signal alarm ON state.

5. A passive optical network comprising:
a first optical network element provided at a first location, the first optical network element comprising a first optical transmitter arranged to generate and transmit a first optical signal, a first controller and first optical receiver apparatus arranged to receive a second optical signal,

wherein the first controller is arranged to:
a. control the first optical transmitter to select a correct wavelength for transmitting a first optical signal from the first location to the second location by iteratively generating and transmitting the first optical signal at different ones of a plurality of wavelengths until the second optical signal is received; and then
b. control the first optical transmitter to cease transmission of the first optical signal for a first time period and then recommence transmission of the first optical at the said selected correct wavelength being transmitted when the second optical signal was received;
a second optical network element provided at a second location, remote from the first location, the second optical network element comprising a second optical transmitter arranged to generate and transmit the second optical signal, a second controller and second optical receiver apparatus arranged to receive the first optical signal,

wherein the second controller is arranged to:
c. wait until the first optical signal is received;
d. then control the second optical transmitter to select a correct wavelength for transmitting the second optical signal from the second location to the first location by iteratively generating and transmitting the second optical signal at different ones of a plurality, N, of wavelengths until the first optical signal is no longer received; and then
e. control the second optical transmitter to maintain generation and transmission of the second optical signal at the said selected correct wavelength being transmitted when the first optical signal was no longer received;

and
a remote node provided at a third location, between the first and second locations, the remote node comprising a wavelength selective routing element.

6. A passive optical network as claimed in claim 5 , wherein the first controller is arranged to control the first optical transmitter to generate and transmit the first optical signal at each said wavelength for a time period, T 1 , wherein T 1 is greater than a total time period required to select the correct wavelength for transmitting the second optical signal from the second location to the first location by iteratively generating and transmitting the second optical signal at the different ones of the plurality, N, of wavelengths until the first optical signal is no longer received at the second location.

7. A passive optical network as claimed in claim 5 , wherein the first optical receiver apparatus comprises a first alarm apparatus arranged to transmit a first alarm signal to the first controller indicative that the second optical signal is received, and the second optical receiver apparatus comprises a second alarm apparatus arranged to transmit a second alarm signal to the second controller, the second alarm signal having a first alarm state indicative that the first optical signal is not received and having a second alarm state indicative that the first optical signal is received.

8. A passive optical network as claimed in claim 7 , wherein each of the first and second alarm apparatus is a loss of signal alarm apparatus, and wherein each alarm signal has a loss of signal alarm ON state indicative that the respective optical signal is not received and each alarm signal has a loss of signal alarm OFF state indicative that the respective optical signal is received.

9. A passive optical network as claimed in claim 5 , wherein the first optical network element is an optical network termination and the second optical network element is an optical line termination.

10. A non-transitory data carrier having computer readable instructions embodied therein, the computer readable instructions comprising instructions that, when executed by a processor, cause the processor to perform a method of configuring transmission wavelengths in a passive optical network comprising a wavelength selective routing element between first and second locations, the method comprising:
at the first location:
a. selecting a correct wavelength for transmitting a first optical signal from the first location to the second location by iteratively generating and transmitting the first optical signal at different ones of a plurality of wavelengths until a second optical signal is received at the first location; and then
b. ceasing transmission of the first optical signal for a first time period and then recommencing transmission of the first optical signal at the said selected correct wavelength

Assignees

• Stracca Stefano
• Giorgi Luca
• Ponzini Filippo
• Ericsson Telefon Ab L M

Inventors

• Stracca Stefano
• Giorgi Luca
• Ponzini Filippo

Classifications

• H04J14/023 Primary

  in WDM passive optical networks [WDM-PON] · CPC title

• H04J14/025

  using one wavelength per ONU, e.g. for transmissions from-ONU-to-OLT or from-ONU-to-ONU · CPC title

• H04J14/0282

  WDM tree architectures · CPC title

• H04J14/0246 Primary

  using one wavelength per ONU · CPC title

• H04B10/572

  Wavelength control · CPC title