Optical Receiver Equalization Using Unified Complex Impulse Responses
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Solution Overview
Problem
Existing adaptive equalization circuits for optical communication lack compatibility and commonality in tap coefficients, leading to increased tap convergence and circuit scale, and fail to collectively compensate for device imperfections in transmitters and receivers when subcarrier signals are used.
Innovation Solution
A signal processing method and apparatus that performs complex signal processing on polarized waves, including convolution, imaginary unit multiplication, and phase rotation to compensate for frequency and wavelength dispersion, while separating real and imaginary components for accurate equalization without increasing circuit scale.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional adaptive equalization circuits are used for subcarrier-modulated signals, then device imperfections in transmitter and receiver cannot be collectively compensated for, but the patent provides a unified compensation method that handles both wavelength dispersion and device imperfections simultaneously
Solution Approach 1:
The patent creates a unified equalization circuit that can handle both conventional single-carrier signals and subcarrier-modulated signals through a common signal processing flow. The key is using a single complex impulse response for wavelength dispersion compensation that works for both signal types, eliminating the need for separate processing paths while maintaining compensation accuracy for device imperfections.
2Reliability
If separate adaptive equalization circuits are used for different signal types, then compensation accuracy may be maintained, but the circuit scale and tap convergence increase
Solution Approach 1:
The patent merges the wavelength dispersion compensation function and device imperfection compensation function into a single adaptive equalization circuit. By using one complex impulse response instead of separate real and imaginary impulse responses, the circuit scale is reduced while maintaining the ability to compensate for both types of impairments simultaneously through unified tap coefficient adaptation.
3Reliability
If multiple impulse responses are used for different compensation functions, then comprehensive compensation is achieved, but the number of taps and processing complexity increase
Solution Approach 1:
The patent changes the parameter representation from separate real and imaginary impulse responses to a single complex impulse response. This parameter transformation reduces the number of taps needed while maintaining comprehensive compensation capabilities, as the complex impulse response can simultaneously represent both wavelength dispersion characteristics and device imperfection characteristics through its magnitude and phase components.
Data Source
AI summary
A receiver convolves an impulse response for compensating for frequency characteristics and a complex impulse response for wavelength dispersion compensation with each of a real component and an imaginary component of each polarized wave of a reception signal. For each polarized wave, the receiver performs complex signal processing of multiplying the imaginary component by the imaginary unit, then branching the resulting component, and adding one imaginary component to the real component. For each polarized wave, the receiver uses, as input signals, the real component and the imaginary component of each polarized wave after complex signal processing and the phase conjugates of them. For each polarized wave, the receiver adds a signal obtained by a process in which each of the real component and the imaginary component of each polarized wave is multiplied by a complex impulse response, the resulting components are added, and a phase rotation is applied and a signal obtained by a process in which each of the phase conjugate of the real component and the phase conjugate of the imaginary component of each polarized wave is multiplied by a complex impulse response, the resulting components are added, and an opposite phase rotation is applied, and adds a transmission data bias correction signal.