Nonlinear spatially resolved interferometer for characterizing optical properties of deployed telecommunication cables

Patent metadata

Field	Value
Publication number	US-10193620-B2
Application number	US-201815953473-A
Country	US
Kind code	B2
Filing date	Apr 15, 2018
Priority date	Apr 21, 2016
Publication date	Jan 29, 2019
Grant date	Jan 29, 2019

Abstract

Using pump-probe measurements on multi-span optical links may result in the determination of one or more of the following: 1) wavelength-dependent power profile and gain evolution along the optical link; 2) wavelength-dependent dispersion map; and 3) location of regions of high polarization-dependent loss (PDL) and polarization-mode dispersion (PMD). Such measurements may be a useful diagnostic for maintenance and upgrade activities on deployed cables as well as for commissioning new cables.

First claim

What is claimed is:

1. A method for measuring physical properties of optical signals as a function of wavelength and as a function of location in an optical link, the method comprising:
generating a first modulated optical carrier at a first wavelength, the first modulated optical carrier carrying pump pulses;
generating a second modulated optical carrier at a second wavelength that differs from the first wavelength, the second modulated optical carrier carrying pilot pulses and carrying probe pulses;
transmitting the first modulated optical carrier and the second modulated optical carrier on an optical fiber over the optical link, the optical link comprising multiple spans connected by one or more optical amplifiers, such that a probe pulse of the probe pulses is spatially overlapped in the optical fiber with a pump pulse of the pump pulses within at least one interaction region in the optical link;
performing a measurement on the probe pulse beyond an end of the optical fiber to measure optical properties of the probe pulse relative to a coherent reference, wherein the coherent reference includes a component of at least one of the pilot pulses, the component being coherent to the probe pulse; and
calculating physical properties of the pump pulse from the measurement on the probe pulse,
wherein the pilot pulses are arranged to be not spatially overlapped in the optical fiber with any of the pump pulses, or the pilot pulses are arranged so that any interaction between the pilot pulses and any of the pump pulses introduces a negligible error or a deterministic-yet-correctable error in measurement of the optical properties.

2. The method as recited in claim 1 , wherein the coherent reference includes a coherent component of an advance pilot pulse of the pilot pulses in advance of the probe pulse and a coherent component of a following pilot pulse of the pilot pulses following the probe pulse, and wherein performing the measurement on the probe pulse beyond the end of the optical fiber to measure optical properties of the probe pulse relative to the coherent reference comprises using the advance pilot pulse and the following pilot pulse to estimate and correct differences between transmit and receive laser sources.

3. The method as recited in claim 1 , further comprising adjusting a time delay between the pump pulse and the probe pulse.

4. The method as recited in claim 1 , wherein the calculated physical properties of the pump pulse include a polarization state of the pump pulse within a particular span of the optical link or within the interaction region.

5. The method as recited in claim 1 , further comprising determining a cumulative dispersion within each span along the optical link from the calculated physical properties of the pump pulse.

6. The method as recited in claim 1 , wherein the calculated physical properties of the pump pulse include a power of the pump pulse at the first wavelength at the one or more interaction regions.

7. The method as recited in claim 1 , wherein generating the first modulated optical carrier comprises modulating an in-service channel at the first wavelength to carry the pump pulses.

8. The method as recited in claim 1 , further comprising pre-distorting the pump pulses to have a desired temporal dependence at the one or more interaction regions.

9. The method as recited in claim 1 , further comprising repeating the method with the pump pulse in varying polarization states or with the probe pulse in varying polarization states, or with both the pump pulse and the probe pulse in varying polarization states.

10. The method as recited in claim 9 , further comprising averaging the measurement on the probe pulse for the varying polarization states to obtain an averaged measurement, wherein calculating physical properties of the pump pulse from the measurement on the probe pulse comprises calculating the physical properties of the pump pulse from the averaged measurement.

11. The method as recited in claim 1 , further comprising repeating the method with the probe pulse in varying non-collinear polarization states, and the calculated physical properties of the pump pulse include a polarization state of the pump pulse within a particular span of the optical link.

12. The method as recited in claim 1 , further comprising repeating the method with different separations between the first wavelength and the second wavelength and with different interaction regions, and estimating a polarization mode dispersion (PMD) of the optical link from the calculated physical properties of the pump pulse.

13. The method as recited in claim 1 , further comprising repeating the method with the pump pulse in varying polarization states, determining a first polarization state that maximizes the common mode phase and a second polarization state that minimizes the common mode phase, and estimating an accumulated polarization dependent loss at the interaction region as the difference between the first polarization state and the second polarization state.

14. A monitoring system for an optical link, the monitoring system comprising:
a first transmitter to generate a first modulated optical carrier at a first wavelength, the first modulated optical carrier carrying pump pulses;
a second transmitter to generate a second modulated optical carrier at a second wavelength that differs from the first wavelength, the second modulated optical carrier carrying pilot pulses and carrying probe pulses;
the first transmitter to transmit the first modulated optical carrier on an optical fiber over the optical link and the second transmitter to transmit the second modulated optical carrier on the optical fiber over the optical link, the optical link comprising multiple spans connected by one or more optical amplifiers, such that a probe pulse of the probe pulses is spatially overlapped in the optical fiber with a pump pulse of the pump pulses within at least one interaction region in the optical link;
a coherent receiver to perform a measurement on the probe pulse beyond an end of the optical fiber to measure optical properties of the probe pulse relative to a coherent reference, wherein the coherent reference includes a component of at least one of the pilot pulses, the component being coherent to the probe pulse; and
a processor to calculate physical properties of the pump pulse from the measurement on the probe pulse,
wherein the pilot pulses are arranged to be not spatially overlapped in the optical fiber with any of the pump pulses, or the pilot pulses are arranged so that any interaction between the pilot pulses and any of the pump pulses introduces a negligible error or a deterministic-yet-correctable error in measurement of the optical properties.

15. The monitoring system as recited in claim 14 , wherein the calculated physical properties of the pump pulse include a power of the pump pulse at the first wavelength at the one or more interaction regions.

16. The monitoring system as recited in claim 14 , wherein the first transmitter is to generate the first modulated optical carrier by modulating an in-service channel at the first wavelength to carry the pump pulses.

17. The monitoring system as recited in claim 14 , wherein the first transmitter is a first coherent transmitter, the second transmitter is a second coherent transmitter, and the second coherent transmitter is synchronized to the first coherent transmitter.

18. The monitoring system as recited in claim 14 , wherein the coherent reference includes a coherent component of an advance pilot pulse of the pi

Assignees

• Shiner Andrew D
• Reimer Michael Andrew
• Osullivan Maurice
• Borowiec Andrzej
• Ciena Corp

Inventors

• Shiner Andrew D
• Reimer Michael Andrew
• O'Sullivan Maurice
• Borowiec Andrzej

Classifications

• G01M11/335 Primary

  using two or more input wavelengths · CPC title

• H04B10/0795

  Performance monitoring; Measurement of transmission parameters · CPC title

• G01M11/39

  in which light is projected from both sides of the fiber or waveguide end-face · CPC title

• G01M11/31

  with a light emitter and a light receiver being disposed at the same side of a fibre or waveguide end-face, e.g. reflectometers · CPC title

• G01M11/336

  by measuring polarization mode dispersion [PMD] · CPC title