Optical Receiver Balancing for Photodetector Response Matching
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Solution Overview
Problem
Optical receivers face challenges in balancing photodetector responsivity and frequency response, leading to inefficiencies in decoding optical signals, particularly due to differences in responsivity and frequency responses between photodetectors.
Innovation Solution
A system with a transimpedance amplifier circuit and controllers that adjust amplifier gain and frequency response to match the responsivity and frequency responses of multiple photodetectors, using transimpedance gain controllers and frequency response controllers to reduce differences and improve common-mode rejection ratio (CMRR) performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple photodetectors are used in parallel to increase bandwidth and improve signal decoding, then the decoding efficiency is improved, but differences in photodetector responsivity and frequency response cause imbalance that degrades common-mode rejection ratio (CMRR) performance
Solution Approach 1:
The patent applies local quality by providing individual transimpedance gain controllers and frequency response controllers for each photodetector channel. These controllers independently adjust the responsivity and frequency response of each photodetector to compensate for manufacturing variations, ensuring that each channel contributes equally to the differential output without degrading CMRR performance
Solution Approach 2:
The patent changes the electrical parameters (transimpedance gain and frequency response) of each photodetector channel dynamically through feedback control. By measuring the actual responsivity and frequency response of each photodetector and adjusting its corresponding controller parameters, the system achieves balanced channel performance while maintaining high decoding efficiency
2Power
If photodetector responsivity is increased to improve signal strength, then the signal decoding capability is improved, but manufacturing variations cause responsivity differences that create channel imbalance and reduce CMRR
Solution Approach 1:
The patent implements feedback control by measuring the actual responsivity of each photodetector and using transimpedance gain controllers to adjust each channel's gain. This feedback mechanism compensates for manufacturing variations, ensuring that all photodetectors contribute equally to the differential output signal, thereby maintaining high signal strength without channel imbalance
Solution Approach 2:
The patent changes the transimpedance gain parameter for each photodetector channel individually based on measured responsivity values. By dynamically adjusting these parameters, the system equalizes the output of all photodetectors despite manufacturing variations, achieving both high signal strength and balanced channel performance
3Power
If the transimpedance amplifier gain is increased to amplify weak signals, then the signal detection capability is improved, but frequency response mismatches between channels are amplified, degrading CMRR performance
Solution Approach 1:
The patent applies local quality by providing individual frequency response controllers for each photodetector channel. These controllers independently adjust the frequency response characteristics of each channel to match a target response, preventing frequency mismatches from degrading CMRR even when high amplification is applied to weak signals
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 balances photodetector responsivity and frequency responses, enhancing the decoding efficiency of optical signals and improving the CMRR performance of optical receivers.
Implementation Method 1
At the optical receivers, the light waves may be decoded into electrical signals
Data Source
AI summary
A method and system, in an optical receiver, includes receiving a first photocurrent from a first photodetector and a second photocurrent from a second photodetector; amplifying the first photocurrent with a first amplifier to provide a first output signal and the second photocurrent with a second amplifier to provide a second output signal; adjusting a frequency response of a first path the first photocurrent and a second path of the second photocurrent; and determining a difference between the adjusted first photocurrent and the adjusted second photocurrent.