Overlapping spectrum amplification

Patent metadata

Field	Value
Publication number	US-9998806-B2
Application number	US-201615348430-A
Country	US
Kind code	B2
Filing date	Nov 10, 2016
Priority date	Nov 10, 2016
Publication date	Jun 12, 2018
Grant date	Jun 12, 2018

Abstract

A method for overlapping spectrum amplification includes receiving an optical signal and splitting the optical signal into a first split signal having a first wavelength band and a second split signal having a second wavelength band. The splitting results in a band gap between the first wavelength band and the second wavelength band. The method further includes delaying the first split signal by a threshold period of time relative to the second split signal and combining the first split signal and the second split signal, resulting in a combined signal having the first wavelength band and the second wavelength band without the band gap therebetween. The path difference between the first split signal along the first signal path and the second split signal along the second signal path is within a threshold multipath interference compensation range.

First claim

What is claimed is:

1. A method comprising:
receiving an optical signal having a first wavelength band and a second wavelength band;
splitting the optical signal into a first split signal having the first wavelength band and a second split signal having the second wavelength band, the splitting resulting in a band gap between the first wavelength band and the second wavelength band;
routing the first split signal along a first signal path;
routing the second split signal along a second signal path different than the first signal path;
delaying the first split signal by a threshold period of time relative to the second split signal;
combining the first split signal and the second split signal, resulting in a combined signal having the first wavelength band and the second wavelength band without the band gap therebetween, wherein a path difference between the first split signal along the first signal path and the second split signal along the second signal path is within a threshold multipath interference compensation range;
splitting the combined signal into a first polarized signal and a second polarized signal;
compensating a chromatic dispersion of each polarized signal;
compensating a polarization mode dispersion of the polarized signals by limiting or reducing spreading of the first polarized signal and the second polarized signal; and
compensating a multipath interference between the first polarized signal and the second polarized signal.

2. The method of claim 1 , wherein the first wavelength band and the second wavelength band each comprises overlapping wavelengths that extend into both the first wavelength band and the second wavelength band.

3. The method of claim 1 , wherein the first wavelength band comprises a C-band of wavelengths and the second wavelength band comprises an L-band of wavelengths.

4. The method of claim 1 , further comprising:
amplifying the first split signal by a first gain; and
amplifying the second split signal by a second gain.

5. The method of claim 4 , further comprising:
receiving the first split signal through a first erbium doped fiber configured to amplify the first split signal by the first gain; and
receiving the second split signal through a second erbium doped fiber configured to amplify the second split signal by the second gain.

6. The method of claim 5 , wherein the first erbium doped fiber has a first length and the second erbium doped fiber has a second length, the first length being less than the second length.

7. The method of claim 6 , wherein delaying the first split signal by the threshold period of time comprises receiving the first split signal through a length compensator, the length compensator comprising a single mode optical fiber optically coupled to the first erbium doped fiber and having a third length sized to impart the delay in the first split signal by the threshold period of time relative to the second split signal at the combining of the delayed first split signal and the second split signal.

8. The method of claim 1 , wherein compensating the chromatic dispersion of each polarized signal comprises compensating for a difference in speed of wavelength components of the first polarized signal and the second polarized signal, and wherein compensating the polarization mode dispersion comprises applying a differential delay to synchronize the compensated polarized signals.

9. The method of claim 1 , wherein compensating the multipath interference comprises resolving a time delay between the first polarized signal and the second polarized signal caused by the path difference between the delayed first split signal and the second split signal.

10. An optical system comprising:
a splitter configured to:
receive an optical signal having a first wavelength band and a second wavelength band; and
split the optical signal into a first split signal having the first wavelength band and a second split signal having the second wavelength band, the splitting resulting in a band gap between the first wavelength band and the second wavelength band;

a gap compensator optically coupled to the splitter and configured to delay the first split signal by a threshold period of time relative to the second split signal, wherein the gap compensator comprises:
a first erbium doped fiber optically coupled to the splitter and configured to amplify the first split signal by a first gain;
a single mode fiber optically coupled to the first erbium doped fiber and having a length sized to impart the delay in the first split signal by the threshold period of time; and
a second erbium doped fiber optically coupled to the splitter and configured to amplify the second split signal by a second gain; and

a combiner optically coupled to the gap compensator and configured to combine the delayed first split signal and the second split signal, resulting in a combined signal having the first wavelength band and the second wavelength band without the band gap therebetween, wherein a path difference between the delayed first split signal and the second split signal is within a threshold multipath interference compensation range,
wherein the combined signal has a power determined as:
Signal Out (λ, t )=Signal In (λ, t )*[Filter(λ) 2 *Gain C (λ,Length C /C Light )* T Delay (Length L /C Light −Length C /C Light )+(1−Filter(λ)) 2 *Gain L (λ,Length L /C Light )]

wherein Signal Out (λ, t) is the power of the combined signal, Signal In (λ, t) is the power of the received signal as a function of a given wavelength λ and time t, Filter(λ) is a filter coefficient based on the given wavelength λ, Gain C is a first gain of the first erbium doped fiber, Gain L is a second gain of the second erbium doped fiber, Length C is a length of the first erbium doped fiber, Length L is a length of the second erbium doped fiber, C Light is the speed of light in fiber, and T Delay is the time delay.

11. The optical system of claim 10 , wherein the first wavelength band and the second wavelength band each comprises overlapping wavelengths that extend into both the first wavelength band and the second wavelength band.

12. The optical system of claim 10 , wherein the first wavelength band comprises a C-band of wavelengths and the second wavelength band comprises an L-band of wavelengths.

13. The optical system of claim 10 , further comprising a digital coherent receiver coupled to the combiner, the digital coherent receiver configured to map an optical field of the optical signal into electronic signals corresponding to phase and quadrature field components.

14. The optical system of claim 13 , wherein the digital coherent receiver comprises a polarization splitter configured to receive the combined signal and split the combined signal into a first polarized signal and a second polarized signal.

15. An optical system comprising:
a splitter configured to:
receive an optical signal having a first wavelength band and a second wavelength band; and
split the optical signal into a first split signal having the first wavelength band and a second split signal having the second wavelength band, the splitting resulting in a band gap between the first wavelength band and the second wavelength band;

a gap compensator optically coupled to the splitter and configured to delay the first split signal by a threshold period of time relative to the second split signal;
a combiner optically coupled to the gap compensator and configured to combine the delayed first split signal and the second split signal, resulting in a combined signal having the first wavelength band and the second wave

Assignees

• Google Inc
• Google Llc

Inventors

• Kamalov Valey
• Vusirikala Vijayanand
• Dangui Vinayak

Classifications

• H04B2210/258

  treating each wavelength or wavelength band separately · CPC title

• H04Q11/0062 Primary

  Network aspects · CPC title

• H04B10/2569

  due to polarisation mode dispersion [PMD] · CPC title

• H04Q2011/0088

  Signalling aspects · CPC title

• H04Q11/0005

  Switch and router aspects · CPC title