Multichannel polarization control for polarization multiplexed optical transport networks
View Patent ↗A system and method are provided for calibrating orthogonal polarity in a multichannel optical transport network (OTN) receiver. The method accepts a composite signal and separates the polarization of the signal into a pair of 2 n -phase shift keying (2 n -PSK) modulated input signals via Ix and Qx optical signal paths, where n≧1. Likewise, a pair of 2 p -PSK modulated input signals are accepted via Iy and Qy optical signal paths where p≧1. Polarization-adjusted I′x, Q′x, I′y, and Q′y signals are generated. An average magnitude is compared to either 2× the absolute magnitude of (I′x and Q′x), or 2× the absolute magnitude of (I′y and Q′y). The average magnitude value can be used that is either 2× (a predetermined peak signal amplitude), or the sum of the absolute magnitudes of (I′x and Q′x) and (I′y and Q′y). The polarization-adjusted I′x, Q′x, I′y, and Q′y signals are modified until the magnitude comparison is about zero.
1. A method for calibrating orthogonal polarity in a multichannel optical transport network (OTN) receiver, the method comprising;
accepting a pair of 2 n -phase shift keying (2 n -PSK) modulated input signals via Ix and Qx optical signal paths, where n≧1;
accepting a pair of 2 p -PSK modulated input signals via Iy and Qy optical signal paths where p≧1;
generating polarization-adjusted I′x, Q′x, and Q′y signals;
comparing an average magnitude to a magnitude selected from a group consisting of 2× the absolute magnitude of (I′x and Q′x) and 2× the absolute magnitude of (I′y and Q′y); and,
modifying the polarization-adjusted I′x, Q′x, I′y, and Q′y signals until the magnitude comparison is about zero.
2. The method of claim 1 wherein generating polarization-adjusted I′x, Q′x, I′y, and Q′y signals includes generating polarization-adjusted I′x, Q′x, I′y, and Q′y optical signals; and,
wherein comparing the average magnitude includes comparing average magnitude optical signals to a magnitude selected from a group consisting of 2× the absolute magnitude of (I′x and Q′x) optical signals and 2× the absolute magnitude of (I′y and Q′y) optical signals.
3. The method of claim 1 further comprising:
envelope detecting the Ix, Qx, Iy, and Qy optical signals to supply Ix, Qx, Iy, and Qy electrical signal amplitudes;
wherein, generating polarization-adjusted I′x, Q′x, I′y, and Q′y signals includes generating polarization-adjusted I′x, Q′x, I′y, and Q′y electrical signals; and,
wherein comparing the average magnitude includes comparing average magnitude electrical signals to a magnitude selected from a group consisting of 2× the absolute magnitude of (I′x and Q′x) electrical signals and 2× the absolute magnitude of (I′y and Q′y) electrical signals.
4. A system for calibrating orthogonal polarity in a multichannel optical transport network (OTN) receiver, the system comprising:
a polarization adjustment circuit (PAC) having an input to accept a pair of 2 n -phase shift keying (2 n -PSK) modulated input signals via Ix and Qx optical signal paths, where n≧1, an input to accept a pair of 2 p -PSK modulated input signals via Iy and Qy optical signal paths where p≧1, and an output to supply polarization-adjusted I′x, Q′x, I′y, and Q′y signals;
a magnitude measurement circuit (MMC) having an input to accept the polarization-adjusted I′x, Q′x, I′y, and Q′y signals, the MMC comparing an average magnitude to a magnitude selected from a group consisting of 2× the absolute magnitude of (I′x and Q′x) and 2× the absolute magnitude of (I′y and Q′y), and supplying a magnitude comparison measurement signal; and,
wherein the PAC accepts the magnitude comparison measurement signal and modifies the polarization-adjusted I′x, Q′x, I′y, and Q′y signals until the magnitude comparison measurement is about zero.
5. The method of claim 4 wherein the PAC accepts I′x, Q′x, I′y, and Q′y optical signals and supplies polarization-adjusted I′x, Q′x, I′y, and Q′y optical signals; and,
wherein the MMC compares average magnitude optical signals to a magnitude selected from a group consisting of 2× the absolute magnitude of (I′x and Q′x) optical signals and 2× the absolute magnitude of (I′y and Q′y) optical signals.
6. The system of claim 4 further comprising:
an envelope detector having an input to accept Ix, Qx, Iy, and Qy optical signals and an output to supply Ix, Qx, Iy, and Qy electrical signal amplitudes;
wherein the PAC accepts Ix, Qx, Iy, and Qy electrical signal amplitudes and supplies polarization-adjusted I′x, Q′x, I′y, and Q′y electrical signals; and,
wherein the MMC compares average magnitude electrical signals to a magnitude selected from a group consisting of 2× the absolute magnitude of (I′x and Q′x) electrical signals and 2× the absolute magnitude of (I′y and Q′y) electrical signals.