Non-linear Jitter Compensation for Optical Transmitters
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Solution Overview
Problem
Optical transmitters face challenges in transmitting high-speed data due to timing jitter, which is exacerbated by non-linear laser characteristics, leading to unpredictable transition timing and reduced transmission speed.
Innovation Solution
A digital jitter compensation circuit is used to detect transitions in the data stream and adjust the level preceding the next transition, either advancing or delaying it to compensate for laser-induced jitter, thereby improving signal quality and enabling higher transmission speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If direct modulation of laser current is used to transmit data, then transmission speed can be increased, but timing jitter increases and reduces signal quality
Solution Approach 1:
The patent applies preliminary action by detecting transitions in the data stream and adjusting the level preceding the next transition before the laser actually transmits the signal. This pre-adjustment compensates for expected laser jitter, ensuring that transitions occur at the correct timing despite the laser's non-linear response characteristics.
Solution Approach 2:
The patent implements feedback by using a jitter compensation circuit that continuously monitors the data stream for transitions and dynamically adjusts the signal level in response to detected transition patterns. This closed-loop approach compensates for laser-induced jitter in real-time, maintaining signal quality at high transmission speeds.
2Speed
If laser operating current and temperature are increased to improve transmission performance, then transmission speed improves, but laser jitter becomes more non-linear and unpredictable
Solution Approach 1:
The patent applies self-service by having the jitter compensation circuit automatically detect transitions and adjust signal levels without requiring external intervention or complex calibration. The system self-regulates to compensate for laser jitter characteristics, reducing the need for manual adjustment while maintaining performance at elevated operating conditions.
3Measurement precision
If settling time of laser response is reduced to prevent jitter, then transition timing accuracy improves, but laser response bandwidth requirements increase
Solution Approach 1:
The patent uses preliminary action to prepare the signal level before the laser transition occurs. By adjusting the level preceding the next transition in advance, the system ensures that the laser has the correct starting condition to achieve accurate transition timing without requiring excessive energy or bandwidth during the actual transition.
Data Source
AI summary
Systems and methods for compensating transitions in a data stream to account for jitter including laser jitter. Transitions in the data stream are delayed or advanced depending on the laser jitter and/or whether the previous transition is a rising or falling transition. The compensation of transitions is non-linear such that compensation applied to a rising transition is not necessarily the same as compensation applied to a falling transition. A history of more than one or more bits or transitions of the data stream can be used to further adjust the compensation of transitions in the data stream. When a transition is detected, the bit following the detected transition is peaked either positively or negatively such that the following transition is accordingly delayed or advanced.