Pre-emphasis Filter for Optical Transmitter Pulse Narrowing
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Solution Overview
Problem
Conventional optical fiber communication systems face challenges in maintaining pulse width and reducing data-dependent jitter, which can lead to performance issues, especially in receivers without feed-forward equalizers.
Innovation Solution
The design of a pre-converter electrical channel with a pre-emphasis filter that overcompensates to reduce pulse narrowing, maintaining wider pulses and potentially increasing overshoot, thereby improving receiver SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pre-converter electrical channel is designed to minimize data-dependent jitter by clipping the signal, then the horizontal eye opening is maximized, but pulse narrowing occurs which degrades receiver SNR
Solution Approach 1:
The patent applies preliminary anti-action by introducing pre-emphasis filtering before the limiting converter to counteract the pulse narrowing effect. The pre-emphasis filter pre-distorts the signal in advance to compensate for the expected pulse compression that will occur at the receiver, thereby preventing the degradation of receiver SNR while maintaining minimized data-dependent jitter
Solution Approach 2:
The patent changes the electrical signal parameters by applying pre-emphasis filtering that modifies the pulse shape and width. The filter adjusts the signal characteristics (amplitude, width, overshoot) to optimize the balance between minimizing data-dependent jitter and maintaining adequate pulse width for receiver SNR, particularly for non-FFE receivers
2Reliability
If the pre-converter electrical channel maintains wider pulses to improve receiver SNR, then pulse width is preserved, but data-dependent jitter increases which reduces horizontal eye opening
Solution Approach 1:
The patent applies parameter changes by using pre-emphasis filtering to modify the electrical signal characteristics. The filter adjusts pulse width, amplitude, and shape parameters to achieve an optimal balance where receiver SNR is improved through wider pulses while data-dependent jitter remains controlled through the limiting converter's clipping function
3Measurement precision
If conventional wisdom optimizes the pre-converter to minimize data-dependent jitter, then horizontal eye width is maximized, but this approach is insufficient for receivers without feed-forward equalizers
Solution Approach 1:
The patent applies universality by designing a pre-converter electrical channel with pre-emphasis filtering that benefits multiple receiver types. The solution simultaneously improves performance for both FFE receivers (by maintaining minimized data-dependent jitter) and non-FFE receivers (by preserving pulse width and reducing pulse narrowing), making the transmitter compatible and effective across different receiver architectures
Solution Approach 2:
The patent applies preliminary anti-action by pre-compensating for pulse narrowing effects that particularly harm non-FFE receivers. The pre-emphasis filter prepares the signal in advance to counteract the lack of equalization capability in non-FFE receivers, thereby improving their performance without compromising FFE receiver operation
Data Source
AI summary
A transmitter reduces or minimizes pulse narrowing. In one approach, an optical transmitter is designed to transmit data over an optical fiber at a specified data rate using on-off keying. The transmitter includes a pre-converter electrical channel and a limiting E/O converter. The pre-converter electrical channel produces a pre-converter signal that drives the limiting E/O converter. The pre-converter electrical channel is designed to reduce pulse narrowing in the pre-converter signal. In one implementation, the pre-converter electrical channel includes a pre-emphasis filter that is designed to minimize pulse width shrinkage.