Adaptive Equalization for IQ Crosstalk in Optical Transceivers
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Solution Overview
Problem
Existing measurement technologies cannot calculate the characteristic of a transceiver that includes IQ crosstalk across multiple polarized waves, particularly in optical transmission systems using single-mode fibers, where crosstalk between X-polarized and Y-polarized waves cannot be expressed by conventional IQ crosstalk models.
Innovation Solution
A characteristic measurement device and method that uses adaptive equalization and phase conjugate signals to derive inverse characteristics of both the transmitter and receiver, accounting for frequency offsets, enabling compensation for signal waveform distortions across multiple polarized waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multistage MIMO adaptive filter is used to compensate for signal distortion, then the signal distortion caused by IQ characteristics can be compensated, but the calculation efficiency is poor because compensation is dynamically performed for each symbol
Solution Approach 1:
The patent performs equalization processing in advance using an adaptive equalization unit to obtain filter coefficients that represent the combined characteristics of the transmitter and receiver. These pre-calculated coefficients are then used to compensate for signal distortion without requiring dynamic recalculation for each symbol, thereby improving calculation efficiency while maintaining compensation accuracy.
Solution Approach 2:
The patent creates a mathematical model (filter coefficients) that copies the combined characteristics of the transmitter and receiver channels. This model is obtained through equalization processing and is then used to represent and compensate for the channel characteristics, avoiding the need for complex real-time calculations while maintaining accurate distortion compensation.
2Measurement precision
If existing measurement technology is used to evaluate IQ characteristic, then the characteristic within one polarization can be evaluated, but the characteristic including crosstalk between lanes beyond polarization cannot be derived
Solution Approach 1:
The patent uses a polarization multiplexed reception signal that contains information from multiple polarization channels (X and Y polarized waves). By processing this combined signal through adaptive equalization, the system can simultaneously evaluate IQ characteristics within each polarization and derive crosstalk characteristics between different polarization lanes, making the measurement system universal for both intra-polarization and inter-polarization characteristic evaluation.
Solution Approach 2:
The patent introduces a characteristic function derivation unit that acts as an intermediary to process the filter coefficients obtained from equalization. This unit derives the combined characteristics of the transmitter and receiver, including crosstalk between lanes, by analyzing the relationship between input and output signals across multiple polarization channels, enabling comprehensive transceiver characteristic measurement.
Data Source
AI summary
A characteristic measurement device that measures a characteristic between lanes of a transmitter and a receiver connected via an optical fiber transmission path, the characteristic measurement device including an adaptive equalization unit that uses a polarization multiplexed reception signal and a phase conjugate signal of the polarization multiplexed reception signal or a plurality of signals mathematically equivalent to the reception signal and the phase conjugate signal of the reception signal as input signals and performs equalization processing on the input signals, and a characteristic function derivation unit that calculates a first inverse characteristic representing an inverse characteristic of the transmitter and a second inverse characteristic representing an inverse characteristic of the receiver on the basis of a filter coefficient obtained at the time of the equalization processing performed by the adaptive equalization unit and a frequency offset.