Optical Receiver Calibration Feedback Circuit
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Solution Overview
Problem
Existing optical receivers face challenges in calibrating and centering the current-to-voltage converter due to variations in the average DC level of optical signals, leading to instability and increased complexity, cost, and power consumption, particularly in tracking changes and preventing loading of the current-to-voltage converter output.
Innovation Solution
An optical receiver with a front-end circuit and a feedback circuit that includes a digital slicer, integrator, digital-to-analog converter, and voltage-controlled current source, which determines and stores a calibration value during a calibration mode to adjust the bias point of the front-end circuit, allowing for stable operation and reduced complexity by eliminating the need for additional switches and capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an RC filter is used to obtain Vref from the output voltage, then the reference voltage can be obtained, but the optical signal must be DC balanced and additional bandwidth constraints are imposed
Solution Approach 1:
The patent implements a feedback circuit that continuously monitors the output voltage and adjusts the biasing of the current-to-voltage converter accordingly. This feedback mechanism eliminates the need for DC-balanced codes by dynamically compensating for DC level variations, allowing flexible signal encoding while maintaining stable reference voltage operation
Solution Approach 2:
The patent changes the operating parameters of the current-to-voltage converter by dynamically adjusting its biasing point based on the detected DC level. This parameter adjustment allows the system to adapt to varying optical signal conditions without requiring DC-balanced encoding or imposing bandwidth constraints on the reference voltage generation
2Measurement precision
If periodic calibration is performed with Vref stored on a capacitor, then the reference voltage can be maintained, but leakage current from the capacitor and inability to scale on-chip capacitor increases complexity and power consumption
Solution Approach 1:
The patent implements a self-adjusting feedback circuit that automatically monitors and corrects DC level variations in real-time. This self-service mechanism eliminates the need for external capacitors and periodic calibration procedures, reducing device complexity and power consumption while maintaining continuous reference voltage stability
Solution Approach 2:
The continuous feedback mechanism replaces periodic calibration by continuously monitoring the output voltage and adjusting the converter biasing accordingly. This eliminates the need for capacitor-based storage and periodic re-calibration, reducing complexity and power consumption while maintaining stable operation
3Reliability
If additional switches and capacitors are added to prevent loading of the current-to-voltage converter output, then the converter can be protected, but the cost, power consumption and complexity increase
Solution Approach 1:
The feedback circuit directly monitors the output voltage and adjusts the converter biasing to maintain stable operation without requiring additional switches or capacitors. This approach protects the converter output through intelligent control rather than through additional protective components, reducing complexity and power consumption
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 enables efficient calibration and centering of the optical receiver, reducing power consumption and complexity while maintaining stability and accuracy in tracking changes in the optical signal, thereby improving the overall performance and reducing latency.
Implementation Method 1
an optical signal is received by a photodiode, which generates current
Implementation Method 2
current that is amplified by a current-to-voltage converter
Data Source
AI summary
An optical receiver is described. This optical receiver includes a digital feedback circuit that biases a front-end circuit, which receives an optical signal, so that an analog electrical signal output by the front-end circuit is calibrated relative to a reference voltage corresponding to a decision threshold of a digital slicer in the optical receiver. In particular, during a calibration mode the feedback circuit may determine and store a calibration value that calibrates the analog electrical signal relative to the reference voltage. Then, during a normal operating mode, the feedback circuit may output a current corresponding to the stored calibration value that specifies a bias point of the front-end circuit.