Optical Transmitter Pre-Emphasis Control via In-Band Power Error Feedback
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Solution Overview
Problem
High data rate optical networks face challenges in accurately setting serializer/deserializer (SerDes) pre-emphasis parameters due to varying interconnect properties of photonic elements, leading to difficulties in in-factory calibration and distortion correction.
Innovation Solution
An optical transmitter module coupled with an electrical serializer/deserializer and a controller, which includes an electrical detector that sends power error signals to the controller to generate a correction control signal, allowing the SerDes to adjust pre-emphasis parameters dynamically and compensate for signal power fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pre-emphasis parameters are set manually in factory calibration, then manufacturing precision can be maintained for known interconnect properties, but the system cannot adapt to varying photonic element properties from different vendors and generations
Solution Approach 1:
The patent implements an automatic calibration system that measures the actual frequency response of the optical transmitter using test signals and detectors, then uses this feedback to automatically adjust pre-emphasis parameters. This closed-loop feedback mechanism eliminates the need for manual factory calibration while adapting to specific photonic element characteristics, thereby resolving the contradiction between adaptability and manufacturing precision.
Solution Approach 2:
The system performs self-calibration by automatically measuring its own frequency response and adjusting its pre-emphasis parameters without external intervention. The optical transmitter uses its own detectors and control logic to characterize its interconnect properties and optimize performance, enabling the system to serve itself rather than requiring manual calibration for each photonic element variant.
2Adaptability or versatility
If automatic pre-emphasis optimization is implemented, then adaptability to different photonic elements is improved, but device complexity increases due to additional control mechanisms
Solution Approach 1:
The control module serves multiple functions: it generates test signals for calibration, detects frequency response using the existing detectors, processes measurement data, and adjusts pre-emphasis parameters. By making the control module multi-functional rather than adding separate dedicated circuits for each function, the patent achieves automatic adaptation while minimizing the increase in device complexity.
Solution Approach 2:
The patent combines the calibration functionality with the existing operational components of the optical transmitter. The same detectors used for signal monitoring are utilized for frequency response measurement during calibration, and the control module integrates both calibration control and operational control functions. This merging approach achieves automatic adaptation without duplicating components, thereby limiting complexity increase.
3Reliability
If continuous optimization is performed to compensate for temperature and temporal effects, then signal integrity is maintained, but loss of time occurs due to ongoing calibration processes
Solution Approach 1:
The patent implements calibration at periodic intervals rather than continuously. Calibration is performed at port turn-up, after reset, and at scheduled maintenance intervals, rather than constantly adjusting parameters. This periodic approach maintains signal integrity by compensating for temperature and temporal effects at critical moments while avoiding the time loss associated with continuous optimization processes.
Data Source
AI summary
In some embodiments, an apparatus includes an optical transmitter module that can be electrically coupled to an electrical serializer/deserializer and a controller. The optical transmitter module can include an electrical detector that can receive an in-band signal. The electrical detector can send to the controller a first power error signal and a second power error signal based on the in-band signal. The controller can send a correction control signal to the electrical serializer/deserializer based on the first power error signal and the second power error signal such that the electrical serializer/deserializer sends a pre-emphasized signal to the optical transmitter module based on the correction control signal. In such embodiments, the first power error signal, the second power signal and the correction control signal are out-of-band signals.