Look-up table and digital transmitter based architecture for fiber nonlinearity compensation
View Patent ↗Systems and methods are disclosed to process an optical signal with a pre-processing module to populate a non-linearity compensation look-up table based on a set of predetermined rules in a non-real-time off-line mode; and a transmitter applying said predetermined rules in real-time to multiple channel input data to generate a real-time symbol pattern, searching the look-up table with the real-time symbol pattern to determine a non-linearity compensation output, and modulating the optical signal with the compensation output.
1. A method to process an optical signal, comprising:
generating a symbol pattern in accordance with predetermined rules;
pre-processing the symbol pattern with non-linearity compensation to fill a look-up table in an off-line mode;
applying said predetermined rules to single channel input data for self-phase modulation (SPM) compensation or multiple channel input data for cross-phase modulation (XPM) compensation to generate a real-time symbol pattern;
searching the look-up table with the real-time symbol pattern to determine a non-linearity compensation output;
comparing one or more input symbol patterns with the look-up table to find corresponding optimal output symbols, wherein the optimal output symbols are sent to a digital-to-analog converter (DAC) array, converted to analog signals; and
modulating the optical signal with the compensation output and the analog signals.
2. The method of claim 1 , wherein generating the look-up table comprises:
determining a plurality of combinations of input symbol sequences from multiple channels; and
performing non-linearity processing on the symbol pattern and storing the symbol pattern in the look-up table.
3. The method of claim 1 , wherein the non-linearity compensation comprises back-propagation.
4. The method of claim 1 , wherein the input symbol patterns indicate modulation format and transmitter architecture.
5. The method of claim 1 , wherein the input symbol patterns include single polarization or polarization multiplexing (PolMux) patterns.
6. The method of claim 1 , comprising reorganizing the input symbol patterns to generate a one dimensional symbol pattern searchable in the look-up table.
7. The method of claim 6 , comprising performing non-linearity compensation on the input symbol patterns and saving results in the look-up table.
8. The method of claim 7 , comprising performing non-linearity compensation at a digital transmitter side to ensure availability of error-free original data for processing and search the look-up table.
9. The method of claim 1 , wherein the symbol pattern comprises a one-dimensional symbol pattern or a multi-dimensional symbol pattern.
10. An apparatus to process an optical signal, comprising:
a pre-processing module to populate a non-linearity compensation look-up table based on a set of predetermined rules in a non-real-time off-line mode;
a comparison module configured to compare one or more input symbol patterns with the look-up table to find corresponding optimal output symbols, wherein the optimal output symbols are sent to a digital-to-analog converter (DAC) array, converted to analog signals; and
a transmitter applying said predetermined rules in real-time to multiple channel input data to generate a real-time symbol pattern, searching the look-up table with the real-time symbol pattern to determine a non-linearity compensation output, and modulating the optical signal with the compensation output and the analog signals.
11. The apparatus of claim 10 , wherein the transmitter comprises a single polarization transmitter.
12. The apparatus of claim 11 , wherein the transmitter comprises a PolMux transmitter.
13. The apparatus of claim 10 , comprising an array of in-phase/quadrature (IQ) modulators coupled to the DAC array.
14. The apparatus of claim 13 , comprising:
a laser; and
a PM coupler provide CW light source to the I/Q modulators.
15. The apparatus of claim 10 , wherein the look-up table is generated by determining a plurality of combination of input symbol sequences from multiple channels and performing non-linearity processing on the symbol pattern and storing the symbol pattern in the look-up table.
16. The apparatus of claim 10 , wherein the non-linearity compensation comprises back-propagation.
17. The apparatus of claim 10 , wherein the input symbol patterns relate to a modulation format and a transmitter architecture.
18. The apparatus of claim 10 , wherein the input symbol patterns include single polarization or polarization multiplexing (PolMux) patterns.
19. The method of claim 1 , comprising performing two-times up-sampling of the optical signal by repeating the optical signal twice.
20. The apparatus of claim 10 , comprising an analog to digital converter (ADC) to perform two-times up-sampling of the optical signal by repeating the optical signal twice.