Optical Receiver Offset Voltage Correction via Variable Gain
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Solution Overview
Problem
Conventional optical receivers face challenges in accurately monitoring optical input levels with small signal strengths due to non-linearity issues and offset voltages, which affect the accuracy of the monitoring process.
Innovation Solution
The optical receiver incorporates a photodiode, a current-to-voltage converter with variable gain, and a correction unit that generates and subtracts multiple voltage signals to eliminate offset voltages, ensuring accurate monitoring across a wide dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional voltage follower with a differential amplifier is used to monitor optical input levels, then the circuit structure is simple, but the monitoring accuracy deteriorates when the optical input level is small due to non-linearity and offset voltage
Solution Approach 1:
The patent segments the current-to-voltage conversion process into two parallel paths: one path uses a fixed conversion gain for standard operation, while the other path uses a variable conversion gain that can be adjusted based on the optical input level. This segmentation allows the system to optimize measurement accuracy for different signal conditions without requiring a completely different circuit architecture.
Solution Approach 2:
The patent introduces a dynamic element by making the conversion gain variable rather than fixed. The variable conversion gain can be adjusted in real-time based on the optical input level, allowing the monitoring circuit to adapt to different signal conditions and maintain high accuracy across a wide dynamic range, particularly for small optical input levels.
2Measurement precision
If a diode is inserted in the output of the differential amplifier to shift the output positively, then the output linearity is improved, but the input voltage remains very small close to the input offset voltage, making accurate monitoring difficult
Solution Approach 1:
The patent changes the conversion gain parameter dynamically based on the optical input level. By adjusting the conversion gain rather than relying on fixed offset compensation, the system can maintain high measurement accuracy for small optical input levels without being limited by the differential amplifier's input offset voltage.
3Measurement precision
If a fixed conversion gain is used in the current-to-voltage converter, then the circuit is simple, but the monitoring accuracy deteriorates for small optical input levels due to offset voltage
Solution Approach 1:
The patent segments the conversion process into multiple paths with different conversion gains. One path handles standard optical input levels with a fixed conversion gain, while another path handles small optical input levels with a variable conversion gain, allowing accurate monitoring across the full dynamic range.
Solution Approach 2:
The patent makes the conversion gain dynamic by introducing a variable conversion gain that can be adjusted based on the optical input level. This dynamic adjustment allows the system to optimize measurement accuracy for different signal conditions, particularly for small optical input levels where fixed gain converters fail.
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 configuration effectively eliminates offset voltages, allowing for precise monitoring of optical input levels even at low signal strengths, enhancing the accuracy and reliability of the monitoring process.
Implementation Method 1
a photodiode generates a current by receiving an optical input signal
Data Source
AI summary
The present invention provides an optical receiver able to monitor the level of the optical input signal in accurate even when the level is quite small. The optical receiver comprises a photodiode to generate a photocurrent Ipd, a current mirror circuit to reflect the photocurrent into a mirrored current Imon, a current-to-voltage converter to convert the mirrored current Imon to a voltage signal, switch to connect/cut the current mirror circuit with the current-to-voltage converter, and a correction unit for subtracting a signal when the switch is connected from a signal when the switch is cut.