Optical systems with diversity detection

1. A method of processing a received optical signal from an optic fiber, the received optical signal carrying user information, the method comprising:

splitting by way of a splitter the received optical signal based on polarization into a fist optical signal and a second optical signal;

converting the first optical signal into a corresponding first electrical signal;

converting the second optical signal into a corresponding second electrical signal;

applying radio frequency detection to the first electrical signal to generate a third electrical signal;

applying radio frequency detection to the second electrical signal to generate a fourth electrical signal;

combining the third electrical signal and the fourth electrical signal to form a fifth electrical signal that carries the user information;

low-pass-filtering the fifth electrical signal to generate a filtered fifth electrical signal;

amplifying the filtered fifth electrical signal to generate an amplified fifth electrical signal; and

processing the amplified fifth electrical signal to align polarizations of the received optical signal with a principal axis of the splitter;

wherein the first optical signal and the second optical signal are aligned with the principal states of polarization of the optic fiber.

2. The method of claim 1 wherein processing the amplified fifth electrical signal is performed by way of a control algorithm to generate control instructions to align the polarizations of the received optical signal with the principal axis of the splitter.

3. The method of claim 1 wherein applying radio frequency detection to the first electrical signal to generate the third electrical signal further comprises:

generating a sixth electrical signal; and

mixing the sixth electrical signal with the first electrical signal.

4. The method of claim 3 wherein applying radio frequency detection to the second electrical signal to generate the fourth electrical signal further comprises:

shifting a phase of the sixth electrical signal; and

mixing the sixth electrical signal with the second electrical signal.

5. The method of claim 1 wherein applying radio frequency detection to the first electrical signal to generate the third electrical signal further comprises:

applying a band pass filter to the first electrical signal; and

applying a square law detector to the first electrical signal.

6. The method of claim 1 wherein applying radio frequency detection to the second electrical signal to generate the fourth electrical signal further comprises;

applying a bandpass filter to the second electrical signal; and

applying a square law detector to the second electrical signal.

7. The method of claim 1 wherein the received optical signal is sub-carrier modulated.

8. A receiver system for processing a received optical signal from an optic fiber, the received optical signal carrying user information, the receiver system comprising:

a splitter configured to split the received optical signal based on polarization into a first optical signal and a second optical signal;

a polarization controller connected to the splitter and configured to align polarizations of the received optical signal with a principal axis of the splitter;

a first converter connected to the splitter and configured to convert the first optical signal into a corresponding first electrical signal;

a second converter connected to the splitter and configured to convert the second optical signal into a corresponding second electrical signal;

a detection system connected to the first converter and the second converter and configured to apply radio frequency detection to the first electrical signal to generate a third electrical signal, apply radio frequency detection to the second electrical signal to generate a fourth electrical signal, and combine the third electrical signal and the fourth electrical signal to form a fifth electrical signal that caries the user information; and

a feedback loop coupled with the detection system to low-pass-filter the fifth electrical signal to generate a filtered fifth electrical signal, amplify the filtered fifth electrical signal to generate an amplified fifth electrical signal, and process the amplified fifth electrical signal to control the polarization controller:

wherein the first optical signal and the second optical signal are aligned with the principal states of polarization of the optic fiber.

9. The receiver system of claim 8 wherein the polarization controller is configured to align the polarizations of the received optical signal based on control instructions from a control algorithm of the feedback loop that processes the amplified fifth electrical signal.

10. The receiver system of claim 8 wherein the detection system is configured to generate a sixth electrical signal and mix the sixth electrical signal with the first electrical signal.

11. The receiver system of claim 10 wherein the detection system is configured to shift a phase of the sixth electrical signal and mix the sixth electrical signal with the second electrical signal.

12. The receiver system of claim 8 wherein the detection system is configured to apply a bandpass filter to the first electrical signal and apply a square law detector to the first electrical signal.

13. The receiver system of claim 8 wherein the detection system is configured to apply a bandpass filter to the second electrical signal and apply a square law detector to the second electrical signal.

14. The receiver system of claim 8 wherein the received optical signal is sub-carrier modulated.