Optical Pre-equalization Circuit Using Symmetry Look-up Tables
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Solution Overview
Problem
Conventional optical multilevel signal pre-equalization circuits face significant challenges in reducing circuit size, leading to increased power consumption and manufacturing costs, particularly due to the need for large FIR filters and look-up tables, which become impractically large as transmission distance and speed increase, limiting the implementation of high-speed optical fiber transmission.
Innovation Solution
The implementation of an optical multilevel signal pre-equalization circuit using a plurality of look-up tables that store middle codes utilizing the symmetry of the signal constellation, combined with operation circuits that perform operations on waveform response components from these look-up tables, allowing for a smaller circuit size and efficient pre-equalization of chromatic dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional FIR filters and look-up tables are used for pre-equalization, then chromatic dispersion compensation is effective, but circuit size becomes impractically large
Solution Approach 1:
The patent divides the pre-equalization circuit into multiple functional blocks: a look-up table storing pre-calculated equalization coefficients, a parallel computation unit that processes multiple signal levels simultaneously, and a separate waveform generation stage. This segmentation allows the circuit to achieve effective chromatic dispersion compensation while keeping each individual block compact, resolving the contradiction between compensation effectiveness and overall circuit size.
Solution Approach 2:
The patent changes the computational parameters by pre-calculating equalization coefficients for multiple signal levels and storing them in a look-up table. Instead of performing complex real-time calculations for each signal level, the system retrieves pre-computed values, dramatically reducing the computational burden and circuit size while maintaining compensation effectiveness.
2Productivity
If transmission distance and speed are increased, then transmission capacity is improved, but circuit size and power consumption increase significantly
Solution Approach 1:
The patent performs preliminary action by pre-calculating equalization coefficients for all possible signal levels before transmission. These pre-computed coefficients are stored in a compact look-up table, allowing the transmitter to handle high transmission distances and speeds without requiring large real-time computation circuits, thus improving transmission capacity while controlling circuit size.
Solution Approach 2:
The patent uses a look-up table that stores copied pre-computed equalization coefficients for multiple signal levels. Instead of independently computing equalization parameters for each signal level during transmission, the system retrieves copied values from the table, reducing computational complexity and circuit size while supporting high transmission capacity.
3Reliability
If conventional pre-equalization circuits are implemented, then chromatic dispersion is compensated, but power consumption increases
Solution Approach 1:
The patent segments the pre-equalization function into a look-up table stage and a simplified retrieval stage. The computationally intensive coefficient calculation is performed once offline and stored, while the online operation only requires table lookup and simple signal processing, dramatically reducing power consumption while maintaining chromatic dispersion compensation effectiveness.
Solution Approach 2:
The patent stores pre-computed equalization coefficients in a look-up table and retrieves them during transmission. This copying approach eliminates the need for continuous complex calculations during high-speed operation, significantly reducing power consumption while maintaining effective chromatic dispersion compensation.
Data Source
AI summary
In order to reduce the circuit size for a chromatic dispersion pre-equalization operation, an optical multilevel signal pre-equalization circuit is provided with: (1) a plurality of look-up tables in which a string of middle codes utilizing a symmetry of a signal constellation of a multilevel code or a string of middle codes represented by polar coordinates is stored in association with a waveform response component; and (2) one or more operation circuits to which the waveform response component corresponding to a multilevel signal to be transmitted is inputted from the plurality of look-up tables, and which outputs a pre-equalized output waveform corresponding to the multilevel signal by operating the waveform response components outputted from different look-up tables.