Polarization Monitoring via Stokes Vector Conversion
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Solution Overview
Problem
Current methods for estimating polarization changes in optical links, such as adaptive equalization, are inaccurate due to noise enhancement and limited update rates, especially when faced with high-velocity rotations and coexisting polarization-dependent losses.
Innovation Solution
An apparatus and method that insert pilot signals into transmission signals, convert them from the Jones space to the Stokes space, and estimate polarization changes using Stokes vectors to accurately monitor velocity changes in optical links, even in complex scenarios with rotation of state of polarization and polarization-dependent loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If adaptive equalization coefficients are used to estimate polarization change, then the estimation process is simple, but the measurement precision is poor due to noise enhancement and coefficients not being strictly equal to inverse of transmission link
Solution Approach 1:
The patent introduces pilot signals as an intermediary element to directly measure polarization changes. These pilot signals are inserted into the transmission signal and their Stokes vectors are used to calculate the actual polarization change, serving as a mediator between the transmitted and received signals to obtain accurate polarization information without relying on adaptive equalization coefficients
Solution Approach 2:
The patent replaces the indirect estimation method using adaptive equalization coefficients with a direct measurement method using Stokes vectors of pilot signals. This substitution transitions from a complex adaptive filtering approach to a simpler and more accurate vector-based calculation approach
2Speed
If adaptive equalization update rate is increased to track high-velocity rotation of state of polarization, then the tracking speed improves, but the device complexity and computational load increase
Solution Approach 1:
The patent performs preliminary action by inserting pilot signals into the transmission signal before transmission. These pilot signals carry polarization information that can be directly extracted at the receiver, eliminating the need for continuous high-rate adaptive equalization updates to track polarization changes
3Device complexity
If simple adaptive equalization coefficients are used to estimate polarization change, then the calculation is simple, but the reliability is poor when rotation of state of polarization and polarization-dependent loss coexist
Solution Approach 1:
The patent uses Stokes vectors of pilot signals as an intermediary to directly measure polarization changes, providing reliable information that is independent of the complexity of polarization transformations including both rotation and polarization-dependent loss effects in the transmission link
Data Source
AI summary
An apparatus and method to monitor a polarization change by inserting pilot signals in a transmission signal and converting the pilot signals in the receiving signal from a Jones space into a Stokes space. A velocity of a polarization change of the optical link is estimated by using the Stokes vectors of the pilot signals, thereby directly and accurately estimating the polarization change of the optical link. Moreover, estimation of the velocity of the polarization may be applicable where rotation of state of polarization and polarization-dependent loss coexist in an optical link.