Common-Mode Current Adjustment in High-Speed Optical Receivers
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Solution Overview
Problem
Optical communication systems face signal impairments such as attenuation and noise, leading to distorted signals and increased Bit Error Rate (BER) due to excessive common-mode current in optoelectronic receivers, particularly in high-speed data communication systems using multi-level pulse amplitude modulation formats like PAM4.
Innovation Solution
An optoelectronic receiver is designed with a common-mode adjustment circuit, an analog front-end (AFE), and an eye scan circuit, controlled by a unit that adjusts the common-mode current to maintain it within a predetermined magnitude, using eye scan information to update a common-mode calibration value and tune the circuit to reduce distortions and maintain signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If common-mode current is increased to handle high-speed data communication, then bandwidth and data rate are improved, but signal distortions and Bit Error Rate increase due to excessive common-mode current
Solution Approach 1:
The patent changes the parameter of common-mode current level by introducing a common-mode adjustment circuit that can dynamically adjust the common-mode current to an optimal level, resolving the contradiction between high data rate requirements and signal quality maintenance
Solution Approach 2:
The patent replaces manual or fixed common-mode current adjustment with an automated control system that uses eye scan information and a control unit to dynamically adjust the common-mode current, enabling adaptive optimization for high-speed communication
2Reliability
If common-mode current is reduced to improve signal quality, then Bit Error Rate decreases, but the ability to handle high-speed data communication is compromised
Solution Approach 1:
The patent makes the common-mode current adjustment dynamic rather than static, allowing the system to adapt the common-mode current level in real-time based on signal conditions, enabling both high speed and high reliability to be achieved under different operating conditions
3Device complexity
If fixed common-mode current adjustment is used, then device complexity is reduced, but adaptability to different signal conditions and data rates is limited
Solution Approach 1:
The patent implements a feedback control mechanism where eye scan information is fed back to the control unit, which then adjusts the common-mode current accordingly. This feedback loop enables the system to adapt to different signal conditions and data rates while maintaining manageable complexity through automated control
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
The solution effectively reduces signal distortions and Bit Error Rate (BER) by maintaining the common-mode current at a level that prevents signal processing limitations, enhancing the quality of the differential voltage generated by the AFE and improving overall receiver performance.
Implementation Method 1
A photodetector receives the optical signal and generates an input photocurrent
Data Source
AI summary
Examples described herein relate to a method and a system for removing the common-mode current. The receiver includes a photodetector, a common-mode adjustment circuit, an analog front-end, an eye scan circuit, and a control unit. The photodetector generates an input photocurrent responsive to a received optical signal. The common-mode adjustment circuit generates an adjusted input current based on the input photocurrent. The analog front-end generates a differential voltage based on the adjusted input current. Based on the differential voltage, the eye scan circuit generates an eye scan information defining a first outer eye and a second outer eye in an eye diagram. The control unit tunes the common-mode adjustment circuit based on a relative height metric of a first height of the first outer eye and a second height of the second outer eye to remove a portion of the common-mode current from the input photocurrent.