Characterization of inter-channel crosstalk in an optical network

1. A system configured to communicatively couple to an optical communications network comprising a plurality of optical data links comprising a plurality of data channels, the system comprising:

one or more processors; and

a memory in communication with the one or more processors, the memory having computer-readable instructions stored thereupon that, when executed by the one or more processors, cause the system to perform operations comprising:

obtaining a time-domain sampled waveform of a selected data channel;

applying a Fourier transform to the time-domain sampled waveform of the selected data channel to generate a frequency-domain waveform of the selected data channel;

obtaining time-domain sampled waveforms of neighboring data channels of the selected data channel;

applying a Fourier transform to the time-domain sampled waveforms of the neighboring data channels of the selected data channel to generate frequency-domain waveforms of the neighboring data channels of the selected data channel;

calculating a noise-to-signal ratio based on the frequency-domain waveforms of the selected data channel and the neighboring data channels of the selected data channel;

based on the calculated noise-to-signal ratio, estimating an optical signal to noise ratio (OSNR) penalty; and

generating a notification of a potential cross-talk issue when the OSNR penalty exceeds a predetermined threshold.

2. The system of claim 1 , wherein homodyne detection is configured to set up a same wavelength for a transmitter and receiver for the selected channel.

3. The system of claim 1 , wherein the time-domain sampled waveforms are generated after analog-to-digital (ADC) sampling of optical signals in the optical communications network.

4. The system of claim 1 , wherein the OSNR penalty is determined based on a scale factor k that is calculated based on a crosstalk waveform equation.

5. The system of claim 1 , wherein the OSNR penalty is determined based on a weighted crosstalk value that is determined by multiplying an interfering signal by a power spectral density of a primary signal.

6. The system of claim 1 , wherein the OSNR penalty is determined at a pre-forward error correction (pre-FEC) bit error rate (BER) threshold.

7. The system of claim 6 , wherein the pre-FEC BER threshold is 1.25E-2.

8. An optical communications network comprising:

a plurality of optical data links comprising a plurality of data channels; and

a system configured to:

turn off neighboring data channels of a target data channel;

obtain a time-domain sampled waveform for the target data channel, wherein the time-domain sampled waveform is generated after analog-to-digital conversion;

apply a Fourier transform to the time-domain sampled waveform for the target data channel to generate a frequency-domain waveform for the target data channel;

turn off the target data channel and turn on neighboring data channels of the target data channel;

obtain time-domain sampled waveforms for the neighboring data channels of the target data channel;

apply a Fourier transform to the time-domain sampled waveforms for the neighboring data channels of the target data channel to generate frequency-domain waveforms for the neighboring data channels of the target data channel;

calculate a noise-to-signal ratio based on the frequency-domain waveforms of the target data channel and the neighboring data channels;

based on the calculated noise-to-signal ratio, estimate an OSNR penalty; and

generate a notification when the OSNR penalty exceeds a predetermined threshold.

9. The optical communications network of claim 8 , wherein the system is further configured to:

determine a weighted crosstalk based on a waveform overlap integral between a crosstalk waveform and the target channel waveform and scaled with a k factor; and

determining that the OSNR penalty exceeds the predetermined threshold based on the weighted crosstalk.

10. The optical communications network of claim 8 , wherein the time-domain sampled waveforms are generated after analog-to-digital (ADC) sampling of optical signals in the optical communications network.

11. The optical communications network of claim 8 , wherein the OSNR penalty is determined based on a scale factor k that is calculated based on a crosstalk waveform equation.

12. The optical communications network of claim 8 , wherein the OSNR penalty is determined based on a weighted crosstalk value that is determined by multiplying an interfering signal by a power spectral density of a primary signal.

13. The optical communications network of claim 8 , wherein the OSNR penalty is determined at a pre-forward error correction (pre-FEC) bit error rate (BER) threshold.

14. The optical communications network of claim 13 , wherein the BER threshold is 1.25E-2.

15. A method implemented on an optical communications network comprising a plurality of optical data links comprising a plurality of data channels, the method comprising:

receiving a time-domain sampled waveform of a selected data channel;

applying a Fourier transform to the time-domain sampled waveform of the selected data channel to generate a frequency-domain waveform of the selected data channel;

receiving time-domain sampled waveforms of neighboring data channels of the selected data channel;

applying a Fourier transform to the time-domain sampled waveforms of the neighboring data channels to generate frequency-domain waveforms of the neighboring data channels;

calculating a noise-to-signal ratio based on the frequency-domain waveforms of the selected data channel and the neighboring data channels;

based on the calculated noise-to-signal ratio, estimating an optical signal to noise ratio (OSNR) penalty; and

generating a notification indicative of a cross-talk issue when the OSNR penalty exceeds a predetermined threshold.

16. The method of claim 15 , further comprising:

turning off neighboring data channels of the selected data channel when accessing the time-domain sampled waveform for the selected data channel; and

turning off the selected data channel and turn on the neighboring data channels when accessing the time-domain sampled waveforms for the neighboring data channels.

17. The method of claim 15 , wherein the OSNR penalty is determined based on a scale factor k that is calculated based on a crosstalk waveform equation.

18. The method of claim 17 , wherein the OSNR penalty is determined based on a weighted crosstalk value that is determined by multiplying an interfering signal by a power spectral density of a primary signal.

19. The method of claim 15 , further comprising wherein the OSNR penalty is determined at a pre-forward error correction (pre-FEC) bit error rate (BER) threshold.

20. The method of claim 15 , wherein homodyne detection is configured to set up a same wavelength for a transmitter and receiver for the selected channel.