Method and device for determining whether a configuration of an optical transmission interface has to be adjusted

Patent metadata

Field	Value
Publication number	US-9455781-B2
Application number	US-201314381368-A
Country	US
Kind code	B2
Filing date	Feb 20, 2013
Priority date	Feb 28, 2012
Publication date	Sep 27, 2016
Grant date	Sep 27, 2016

Abstract

A method for determining whether a configuration of an optical transmission interface of a first device has to be adjusted for transmitting an optical signal to a second device via an optical band-pass filter, the second device including an optical reception interface configured to enable receiving optical signals output by said optical band-pass filter and transmitted by the first device on a carrier wavelength when the carrier wavelength is in the passband of the optical band-pass filter. A monitoring device performs: obtaining an information representative of a time drift between successive symbols of an optical signal received by the second device, from the first device, via the optical band-pass filter; and determining whether the configuration of the optical transmission interface of the first device has to be adjusted, on the basis of the information representative of the time drift.

First claim

The invention claimed is:

1. A method for determining whether a configuration of an optical transmission interface of a first device has to be adjusted for transmitting an optical signal to a second device, the method comprising a monitoring device performing:
receiving, from the second device, information representative of instants at which extremes of signal strength are detected by the second device in at least two successive symbols of the optical signal received by the second device from the first device,
wherein the optical signal is transmitted by the first device to the second device via an optical band-pass filter, the second device includes an optical reception interface configured to receive optical signals output by said optical band-pass filter and transmitted by the first device on a carrier frequency when said carrier frequency is in the passband of the optical band-pass filter;
determining at least one time period between said instants at which the extremes of signal strength are detected in the at least two successive symbols of the optical signal;
obtaining information representative of a time drift on the basis of the determined at least one time period, said time drift being due to a frequency shift between the carrier frequency and a nominal frequency of the optical pass-band filter, the information representative of the time drift being obtained by checking whether the at least one time period decreases compared with a reference time period duration, remains stable compared with a reference time period duration, or increases compared with a reference time period duration;
determining whether the configuration of the optical transmission interface of the first device has to be adjusted, on the basis of the information representative of the time drift; and
adjusting said configuration when the time drift exhibits a time period increase between the extremes of signal strength.

2. The method according to claim 1 , wherein the second device performs oversampling of the at least two successive symbols of the optical signal received by the second device, from the first device, via the optical band-pass filter.

3. The method according to claim 1 , wherein the first device successively transmits plural copies of each symbol of the at least two successive symbols, said symbols having the same duration, each copy of each symbol being delayed from the immediately preceding copy of said symbol, if any, by a submultiple of the duration of the symbols duration,
wherein the second device performs, for each symbol, sampling of the plural copies of said symbol in the optical signal received by the second device from the first device via the optical band-pass filter, and
wherein the second device performs detecting detects, for each symbol, at least one extreme of signal strength among the plural copies of said symbol.

4. The method according to claim 1 , wherein the first device successively transmits plural copies of the at least two successive symbols, said symbols having the same duration,
wherein the second device performs sampling operations on the plural copies in the optical signal received by the second device from the first device via the optical band-pass filter, each sampling operation for one copy among the plural copies being delayed compared to the sampling operation of the immediately preceding copy among the plural copies by a submultiple of the duration of the symbols, and
wherein the second device detects, for each symbol, at least one extreme of signal strength among the plural copies of said symbol.

5. The method according to claim 3 , wherein the monitoring device receives from the second device information indicating, among a sequence of the plural copies of one symbol among the at least two successive symbols, an index of a copy among the plural copies containing an extreme of signal strength detected by the second device.

6. The method according to claim 1 , wherein said extremes are signal strength maximum values for each symbol of the at least two successive symbols.

7. The method according to claim 1 , wherein the monitoring device further performs:
detecting that no information has been received from the second device during a predetermined time period for obtaining the information representative of the time drift; and
requesting the first device to transmit to the second device at least another symbol via the optical band-pass filter.

8. A method for determining whether a configuration of an optical transmission interface of a first device has to be adjusted for transmitting an optical signal to a second device, the method comprising a monitoring device performing:
receiving, from the second device, information representing that a control voltage of an oscillator of a clock recovery unit driving an analogue-to-digital converter of the second device transiently varies when the second device receives the optical signal from the first device,
wherein the optical signal is transmitted by the first device to the second device via an optical band-pass filter, the second device includes an optical reception interface configured to receive optical signals output by said optical band-pass filter and transmitted by the first device on a carrier frequency when said carrier frequency is in the passband of the optical band-pass filter;
obtaining information representative of a time drift on the basis of transient variations in the control voltage of the oscillator of the clock recovery unit, said time drift being due to a frequency shift between the carrier frequency and a nominal frequency of the optical pass-band filter, the information of the time drift being obtained by checking whether the transient variations in the control voltage decrease as a function of time, remain stable as a function of time, or increase as a function of time;
determining whether the configuration of the optical transmission interface of the first device has to be adjusted, on the basis of the information representative of the time drift; and
adjusting said configuration when the time drift is indicative of an increase or a decrease in the transient variations in the control voltage as a function of time, according to whether the increase or respectively the decrease corresponds to the carrier frequency going away from the nominal frequency of the optical pass-band filter.

9. The method according to claim 8 , wherein the monitoring device further performs:
detecting that no information has been received from the second device during a predetermined time period for obtaining the information representative of the time drift; and
requesting the first device to transmit to the second device at least another symbol via the optical band-pass filter.

10. The method according to claim 1 , wherein the monitoring device performs, before obtaining the information representative of the time drift:
obtaining information representative of a signal temporal shape of one symbol of the optical signal, which is received by the second device from the first device via the optical band-pass filter before said at least two successive symbols;
determining whether the configuration of the optical transmission interface of the first device has to be adjusted, on the basis of said information representative of the signal temporal shape by checking whether said signal temporal shape exhibits a frequency shift compared to a predetermined signal shape; and
adjusting said configuration when the signal temporal shape exhibits the frequency shift.

11. The method according to claim 1 , wherein the monitoring device performs, before obtaining the information representative of the time drift:
obtaining information

Assignees

• Mitsubishi Electric Corp

Inventors

• Froc Gwillerm
• Weppe Olivier

Classifications

• H04J14/0221

  Power control, e.g. to keep the total optical power constant · CPC title

• H04B10/0795 Primary

  Performance monitoring; Measurement of transmission parameters · CPC title

• H04B10/2507

  for the reduction or elimination of distortion or dispersion · CPC title

• H04J14/02216

  by gain equalization · CPC title

• H04Q11/0062

  Network aspects · CPC title