Optical Timing Alignment via Low-Frequency Clock Phase Shifting
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Solution Overview
Problem
Conventional methods for aligning the timing between optical data modulation and a periodically modulated light source in RZ transmission systems are complex and expensive, and introduce undesirable time jitters due to high-frequency phase shifters and feedback loops.
Innovation Solution
A method using a low-frequency phase shifter to align the timing of data modulation with a periodically modulated light source, accompanied by a phase lock loop to maintain optimal alignment, reduces complexity and jitter by shifting the phase of a lower frequency clock signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-frequency phase shifters are used to align timing between data modulation and light source, then timing alignment is achieved, but device complexity and cost increase significantly
Solution Approach 1:
Instead of shifting the phase of the high-frequency data modulation signal (which is complex and expensive), the invention inverts the approach by shifting the phase of the lower-frequency clock signal that drives the light source. This is achieved by inserting a phase shifter in the clock path rather than the data path, thereby achieving the same timing alignment effect with a simpler and less costly component.
2Adaptability or versatility
If high-frequency phase shifters are used to cover 360 degrees phase shift range, then full timing adjustment is achieved, but insertion loss varies significantly
Solution Approach 1:
The invention transfers the phase shifting operation from the high-frequency data path to the lower-frequency clock path. Since the clock signal operates at a lower frequency, the phase shifter experiences more stable electrical characteristics and less variation in insertion loss across the full 360-degree phase shift range, while still achieving the required timing adjustment when converted back to the data modulation timing.
3Stability of the object's composition
If feedback loop is implemented to lock relative timing, then timing stability is improved, but time jitter is introduced to output signals
Solution Approach 1:
The invention performs the timing alignment action in advance by shifting the clock signal phase before it drives the light source modulation. This preliminary phase adjustment establishes the correct timing relationship between data modulation and light source without requiring continuous feedback-induced dithering, thereby achieving timing stability without introducing the harmful time jitter that would otherwise be generated by feedback loop corrections.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach simplifies the alignment process, reduces costs, and minimizes time jitter in optical data signals, ensuring stable and optimized RZ transmission performance across varying environmental conditions.
Implementation Method 1
Phase adjustment of the first reference clock signal are conducted before the first reference clock signal is provided to the first multiplexer, or phase adjustment of the second reference clock signal are conducted before the second reference clock signal is provided to the second multiplexer, wherein the phase adjustment aligns a timing of data modulated by the data modulator with a periodically modulated light source generated by the clock modulator.
Data Source
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AI summary
A method and system is disclosed for making time alignment for a data transmission system. A first reference clock signal is provided to a first multiplexer coupled to a data modulator through a data driver, and a second reference clock signal is provided to a second multiplexer coupled to a clock modulator through a clock driver. Phase adjustment of the reference clock signal are conducted before the first reference clock signal is provided to the first multiplexer, wherein the phase adjustment aligns a timing of data modulated by the data modulator with a periodically modulated light source generated by the clock modulator.