Method and system for removing a pilot tone from an optical signal

Patent metadata

Field	Value
Publication number	US-9705628-B2
Application number	US-201615258661-A
Country	US
Kind code	B2
Filing date	Sep 7, 2016
Priority date	Jan 16, 2015
Publication date	Jul 11, 2017
Grant date	Jul 11, 2017

Abstract

The present applies to digital wavelength converters that convert, independently of the format in which optical data may be encoded, an input waveform at a first wavelength to an output waveform at a second wavelength. When operating in an environment where an input waveform has a pilot tone associated thereto, the method and system of the present disclosure allows for the removal of the pilot tone from the input waveform, and also allows for the addition of another pilot to the output waveform.

First claim

What is claimed is:

1. A transmitter comprising:
a pilot tone processing unit configured to calculate an optical tone addition factor for adding a pilot tone to a digital signal, the optical tone addition factor comprising a pilot tone frequency of the pilot tone and a modulation depth of the pilot tone;
a multiplier configured to multiply the digital signal with the optical tone addition factor;
a digital-to-analog (DAC) converter configured to receive an output from the multiplier; and
an electrical-to-optical (EO) converter configured to receive an output from the DAC and output an optical signal having the pilot tone based on the optical tone addition factor.

2. The transmitter of claim 1 wherein the optical tone addition factor is equal to: 1+m×cos(2πf PT t+Ø), where m is the modulation depth of the pilot tone, f PT is the frequency of the pilot tone, Ø is a phase of the pilot tone, and t is time.

3. The transmitter of claim 1 comprising N multipliers and N DACs, where N is equal to a number of digital signals being processed by the transmitter, wherein each digital signal of the N digital signals is processed by a respective multiplier and DAC prior to being processed by the EO converter.

4. The transmitter of claim 3 wherein the number of digital signals N is based on a signal modulation format used to modulate the digital signals.

5. The transmitter of claim 4 wherein:
for a dual polarization QAM modulation format N=4;
for a single polarization QAM modulation format N=2; and
for an on-off keying (OOK) modulation format N=1.

6. The transmitter of claim 3 wherein the EO converter is configured to generate the optical signal as a function of the N digital signals.

7. The transmitter of claim 1 wherein the modulation depth of the pilot tone is time dependent enabling the pilot tone to be modulated and carry information.

8. The transmitter of claim 1 wherein the pilot tone processing unit is configured to generate the time dependent modulation depth and frequency.

9. The transmitter of claim 1 wherein the modulation depth is less than 0.1.

10. The transmitter of claim 3 wherein:
the frequency and modulation depth is the same for all N digital signals; or
the frequency and modulation depth is the same for K of the N digital signals and different than the frequency and modulation depth of the remaining N-K digital signals.

11. A method for adding a pilot tone to an optical signal, the method comprising:
calculating an optical tone addition factor for adding a pilot tone to a digital signal, the optical tone addition factor comprising a pilot tone frequency of the pilot tone and a modulation depth of the new pilot tone;
multiplying the digital signal with the optical tone addition factor to add the pilot tone to the digital signal;
converting the digital signal with the added pilot tone into an analog signal; and
converting the analog signal from an electrical signal into an optical signal having the pilot tone based on the optical tone addition factor.

12. The method of 11 wherein the optical tone addition factor is equal to: 1+m×cos(2πf PT t+Ø), where m is the modulation depth of the pilot tone, f PT is the frequency of the pilot tone, Øis a phase of the pilot tone, and t is time.

13. The method of claim 11 wherein adding a pilot tone to the optical signal comprises adding a pilot tone to one or more of N digital signals being transmitted by the transmitter.

14. The method of claim 13 wherein a number of digital signals N is based on a signal modulation format used to modulate the digital signals.

15. The method of claim 14 wherein:
for a dual polarization QAM modulation format N=4;
for a single polarization QAM modulation format N=2; and
for an on-off keying (OOK) modulation format N=1.

16. The method of claim 11 wherein converting the analog signal from an electrical signal into an optical signal comprises generating the optical signal as a function of the N digital signals.

17. The method of claim 11 further comprising modulating the modulation depth of the pilot tone over time.

18. The method of claim 11 wherein the modulation depth is less than 0.1.

19. The method of claim 11 further comprising generating the time dependent modulation depth.

20. The method of claim 13 wherein:
the frequency and modulation depth is the same for all N digital signals; or
the frequency and modulation depth is the same for K of the N digital signals and different than the frequency and modulation depth of the remaining N-K digital signals.

Assignees

• Jiang Zhiping
• Zhang Zhuhong
• Tang Xuefeng
• Huawei Tech Co Ltd

Inventors

• Jiang Zhiping
• Zhang Zhuhong
• Tang Xuefeng

Classifications

• H04B10/077

  using a supervisory or additional signal · CPC title

• H04B10/516

  Details of coding or modulation · CPC title

• H04J14/0276 Primary

  using pilot tones · CPC title

• H04B2210/075

  using a pilot tone · CPC title

• H04B10/0775

  Performance monitoring and measurement of transmission parameters · CPC title