Compensation for optical multi-path interference
Systems and methods for optical multi-path interference (MPI) compensation are provided. In an embodiment, a mean MPI signal representing a mean amplitude of the MPI in an input signal is generated and subtracted from a first estimate of transmitted amplitude of the input signal to generate a mean MPI compensated estimate of transmitted amplitude. The mean MPI compensated estimate of transmitted amplitude is sliced to generate a decision of transmitted amplitude of the input signal. The mean MPI signal can be generated using a mean MPI feedback loop or using an iterative feed-forward process. In another embodiment, mean MPI levels corresponding to respective transmitted intensity levels are generated and used to control slice levels of a slicer in order to compensate for MPI.
1. A system for compensating for optical multi-path interference (MPI) in an input signal received over an optical fiber, comprising:
a converter module configured to receive an estimate of a transmitted light intensity of the input signal and to generate a first estimate of a transmitted amplitude of the input signal; and
a slicer configured to receive a mean MPI compensated estimate of the transmitted amplitude of the input signal and to generate a decision of the transmitted amplitude of the input signal, wherein the mean MPI compensated estimate of the transmitted amplitude of the input signal is determined based on the first estimate of the transmitted amplitude of the input signal and a mean MPI signal representative of a mean of the optical MPI.
2. The system of claim 1 , wherein the mean MPI compensated estimate of the transmitted amplitude of the input signal includes the first estimate of the transmitted amplitude of the input signal reduced by the mean MPI signal.
3. The system of claim 1 , further comprising:
an accumulator module configured to receive a difference signal determined based on a difference between the mean MPI compensated estimate of the transmitted amplitude of the input signal and the decision of the transmitted amplitude of the input signal and to generate the mean MPI signal based on the difference signal.
4. The system of claim 3 , further comprising:
a subtractor module, coupled to the accumulator module, configured to subtract the mean MPI signal from the first estimate of the transmitted amplitude of the input signal to generate the mean MPI compensated estimate of the transmitted amplitude of the input signal.
5. The system of claim 3 , further comprising:
a subtractor module, coupled to the slicer, configured to subtract the decision of the transmitted amplitude of the input signal from the mean MPI compensated estimate of the transmitted amplitude of the input signal to generate the difference signal; and
a multiplier, coupled to the subtractor module, configured to multiply the difference signal by a gain factor and to provide the multiplied difference signal to the accumulator module.
6. The system of claim 1 , further comprising:
an equalizer configured to receive the input signal and to generate the estimate of the transmitted light intensity of the input signal.
7. The system of claim 1 , further comprising a decision feedback loop.
8. The system of claim 7 , wherein the decision feedback loop comprises:
a delay module, coupled to the slicer, configured to receive an estimate of the transmitted amplitude of the input signal and to output a delayed estimate of the transmitted amplitude of the input signal; and
a multiplier configured to scale the delayed estimate of the transmitted amplitude of the input signal to generate a scaled delayed estimate of the transmitted amplitude of the input signal.
9. The system of claim 8 , further comprising:
a subtractor module, coupled to the delay module, configured to subtract the scaled delayed estimate from the first estimate of the transmitted amplitude of the input signal.
10. The system of claim 1 , wherein the mean MPI signal is generated based on a difference between the mean MPI compensated estimate of the transmitted amplitude of the input signal and the decision of transmitted amplitude of the input signal.
11. A method for compensating for optical multi-path interference (MPI) in an input signal received over an optical fiber, comprising:
receiving an estimate of a transmitted light intensity of the input signal;
generating a first estimate of a transmitted amplitude of the input signal based on the estimate of the transmitted light intensity of the input signal;
determining a mean MPI compensated estimate of the transmitted amplitude of the input signal based on the first estimate of the transmitted amplitude of the input signal and a mean MPI signal representative of a mean amplitude of the optical MPI; and
generating a decision of the transmitted amplitude of the input signal based on the mean MPI compensated estimate of the transmitted amplitude of the input signal.
12. The method of claim 11 , wherein the mean MPI compensated estimate of the transmitted amplitude of the input signal includes the first estimate of the transmitted amplitude of the input signal reduced by the mean MPI signal.
13. The method of claim 11 , further comprising:
generating the mean MPI signal based on a difference signal determined based on a difference between the mean MPI compensated estimate of the transmitted amplitude of the input signal and the decision of the transmitted amplitude of the input signal.
14. The method of claim 13 , further comprising:
subtracting the mean MPI signal from the first estimate of the transmitted amplitude of the input signal to generate the mean MPI compensated estimate of the transmitted amplitude of the input signal.
15. The method of claim 13 , further comprising:
subtracting the decision of the transmitted amplitude of the input signal from the mean MPI compensated estimate of the transmitted amplitude of the input signal to generate the difference signal; and
multiplying the difference signal by a gain factor.
16. The method of claim 11 , further comprising:
generating the estimate of the transmitted light intensity of the input signal based on the input signal.
17. The method of claim 11 , further comprising:
providing a delayed estimate of the transmitted amplitude of the input signal based on an estimate of the transmitted amplitude of the input signal; and
scaling the delayed estimate of the transmitted amplitude of the input signal to generate a scaled delayed estimate of the transmitted amplitude of the input signal.
18. The method of claim 17 , further comprising:
subtracting the scaled delayed estimate from the first estimate of the transmitted amplitude of the input signal.
19. A system for compensating for optical multi-path interference (MPI) in an input signal received over an optical fiber, comprising:
a converter module configured to generate a first estimate of a transmitted amplitude of the input signal based on a received estimate of a transmitted light intensity of the input signal; and
a slicer configured to generate a decision of the transmitted amplitude of the input signal based on a mean MPI compensated estimate of the first estimate of the transmitted amplitude of the input signal, wherein the mean MPI compensated estimate of the first estimate of the transmitted amplitude of the input signal is determined based on the first estimate of the transmitted amplitude of the input signal and a mean MPI signal representative of a mean of the optical MPI.
20. The system of claim 19 , further comprising a decision feedback loop, the decision feedback loop comprising:
a delay module, coupled to the slicer, configured to receive an estimate of the transmitted amplitude of the input signal and to output a delayed estimate of the transmitted amplitude of the input signal; and
a multiplier configured to scale the delayed estimate of the transmitted amplitude of the input signal to generate a scaled delayed estimate of the transmitted amplitude of the input signal.