Adaptive equalization in coherent fiber optic communication
View Patent ↗An embodiment of the invention is a technique to equalize received samples. A coefficient generator generates filter coefficients using an error vector and input samples. A filter stage generates equalized samples from input samples using the filter coefficients. The received samples are provided by a receiver front end in an optical transmission channel carrying transmitted symbols. Other embodiments are also described.
1. An apparatus comprising:
a coefficient generator to generate filter coefficients using an error vector and input samples; and
a filter stage coupled to the coefficient generator to generate equalized samples from the input samples using the filter coefficients, the input samples being provided by a receiver front end in an optical transmission channel carrying transmitted symbols,
wherein the receiver front end comprises at least a multidimensional rotator to rotate its input signal,
wherein the optical transmission channel operates at a symbol rate of at least 10 Gigabauds.
2. The apparatus of claim 1 , wherein the multidimensional rotator rotates at least one of phase and polarization of its input signal.
3. The apparatus of claim 2 , wherein the multidimensional rotator is adaptively trained according to an optimality criterion.
4. The apparatus of claim 3 , wherein the optimality criterion is the minimization of the receiver mean squared error.
5. The apparatus of claim 3 , wherein the optimality criterion is the minimization of the receiver bit error rate.
6. The apparatus of claim 1 , wherein the receiver front end comprises at least a matched filter.
7. The apparatus of claim 6 , wherein the matched filter is matched to the impairments of the optical channel.
8. The apparatus of claim 6 , wherein the matched filter is matched to at least the chromatic dispersion of the optical channel.
9. The apparatus of claim 6 , wherein the matched filter is matched to at least the polarization mode dispersion of the optical channel.
10. The apparatus of claim 6 , wherein the matched filter is matched to at least the skews of the optical channel.
11. A method comprising:
generating filter coefficients using an error vector and input samples; and
generating equalized samples from the input samples using the filter coefficients, the input samples being provided by a receiver front end in an optical transmission channel carrying transmitted symbols, wherein the receiver front end comprises at least a multidimensional rotator to rotate its input signal, wherein the optical transmission channel operates at a symbol rate of at least 10 Gigabauds.