Differential delay receiver using cross-polarization interferometer for PolMux-DPSK system

1. A differential delay detection system, comprising:

an optical splitter to split an incoming optical signal between a first path and a second path;

the first path comprising:

a cross-polarization interferometer configured to separately generate polarization independent outputs using split paths and to generate cross-polarization interference outputs;

a polarization demultiplexer configured to combine the polarization independent outputs and the cross-polarization interference outputs from the cross-polarization interferometer with updated coefficients received from the second path to remove the cross-polarization mixed signals; and

the second path comprising:

a training signal receiver configured to compute the updated coefficients and output the updated coefficients to the polarization demultiplexer;

wherein the first and second polarization signal are further split and the cross-polarization interferometer further comprises a polarization controller configured to rotate a split version of the first polarization signal by 90 degrees to form a rotated version of the first polarization signal and a split version of the second polarization signal and the rotated version are cross-coupled with one tap delays to output the cross-polarization interference outputs.

2. The system as recited in claim 1 , wherein the cross-polarization interferometer includes a polarization beam splitter to split a split incoming optical signal into a first polarization signal and a second polarization signal.

3. The system as recited in claim 1 , wherein a split version of the first polarization signal is combined with a one tap delay version of itself and a split version of the second polarization signal is combined with a one tap delay version of itself to provide the polarization independent outputs.

4. The system as recited in claim 1 , wherein the polarization demultiplexer includes multipliers to multiply the updated coefficients with one of the polarization independent outputs and the cross-polarization interference outputs.

5. The system as recited in claim 4 , wherein the polarization demultiplexer includes adders to add product outputs of the multipliers.

6. The system as recited in claim 1 , wherein the incoming signal is modulated using differential phase shift keying (DPSK) and the polarization demultiplexer outputs to a DPSK receiver.

7. A method for differential delay detection, comprising:

splitting an incoming optical signal between a first path and a second path;

in the first path, generating polarization independent outputs and cross-polarization interference outputs using split paths in a cross-polarization interferometer;

polarization demultiplexing the polarization independent outputs and the cross-polarization interference outputs from the cross-polarization interferometer to combine with updated coefficients received from the second path to remove the cross-polarization mixed signals;

in the second path, computing the updated coefficients to output the updated coefficients to the polarization demultiplexer using a training signal receiver;

splitting the incoming optical signal in the first path into a first polarization signal and a second polarization signal;

further splitting the first and second polarization signals;

rotating a split version of the first polarization signal by 90 degrees to form a rotated version of the first polarization signal; and

combining a split version of the first polarization signal with a one tap delay version of itself, and combining a split version of the second polarization signal with a one tap delay version of itself to provide the polarization independent outputs.

8. The method as recited in claim 7 , further comprising cross-coupling a split version of the second polarization signal and the rotated version with one tap delays to output the cross-polarization interference outputs.

9. The method as recited in claim 7 , further comprising:

multiplying the updated coefficients with one of the polarization independent outputs and the cross-polarization interference outputs by the polarization demultiplexer.

10. The method as recited in claim 9 , further comprising: adding product outputs of the multipliers by the polarization demultiplexer.

11. The method as recited in claim 7 , wherein the incoming signal is modulated using differential phase shift keying (DPSK) and the polarization demultiplexer outputs to a DPSK receiver.