Laser Driver Feedback Current Compensation Circuit
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Solution Overview
Problem
Conventional laser drivers in optical or optoelectronic modules cannot regulate the target optical output power when the feedback current from the monitoring photodiode exceeds their adjustable range, limiting their operational range and accuracy.
Innovation Solution
A circuit and method that utilize a microprocessor and current divider to reduce the feedback current from the monitoring photodiode, keeping it within the adjustable range of the laser driver, allowing the driver to accurately regulate the optical output power even at high feedback currents by enabling a current divider to capture a predetermined amount of DC current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the feedback current from the monitoring photodiode is used directly by the laser driver, then the laser driver can regulate the optical output power within its adjustable range, but when the feedback current exceeds the adjustable range, the laser driver cannot regulate the output power
Solution Approach 1:
The feedback current path is segmented into two branches: one branch goes directly to the laser driver for normal operation, and another branch passes through the current divider circuit to the microprocessor. This segmentation allows the system to handle both normal and high feedback current scenarios simultaneously, extending the adjustable range while maintaining regulation capability.
Solution Approach 2:
The current divider circuit acts as an intermediary between the monitoring photodiode and the microprocessor. It divides the high feedback current into a manageable portion for processing, enabling the microprocessor to calculate compensation values even when the total feedback current exceeds the laser driver's direct adjustable range.
2Adaptability or versatility
If a current divider is introduced to reduce feedback current, then the adjustable range of the laser driver is extended, but the device complexity increases
Solution Approach 1:
The current divider circuit serves multiple functions: it divides the feedback current for microprocessor processing, enables extended range measurement, and works seamlessly with the existing laser driver circuitry. This multi-functionality justifies the added complexity by providing significant operational range extension without requiring completely separate systems.
Solution Approach 2:
The system uses its own feedback current signal to generate the compensation information needed for extended range operation. The microprocessor processes the divided feedback current and automatically calculates the compensation values, making the system self-sufficient and reducing the need for external calibration or additional sensing components.
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 solution extends the adjustable range of laser drivers, enabling them to regulate target optical output power with high accuracy and broad range, even at relatively high feedback currents, thereby overcoming the limitations of conventional drivers.
Implementation Method 1
a monitoring photodiode (MPD) connected to the laser driver. The MPD is configured to provide a current (e.g., a feedback current) representative of or corresponding to the output power of the laser in real time
Implementation Method 2
the microprocessor instructs the current divider to reduce the feedback current (which may be a DC current) by a predetermined amount to keep the feedback current in the adjustable and/or operating range of the laser driver
Data Source
AI summary
A dual-rate power point compensating circuit, comprising a microprocessor and a transmitter optical subsystem assembly (TOSA), wherein the TOSA includes a laser connected to a laser driver, a monitor photodiode (MPD) connected to the laser driver, and a current divider connected to the microprocessor and the MPD. When a feedback current from the MPD exceeds the adjustable and/or operating range of the laser driver, the feedback current is reduced so that it is kept in the adjustable and/or operating range of the laser driver. The laser driver determines the optical output power of the laser from the value of the reduced feedback current. The circuit and method extend the adjustable and/or operating range of a laser driver and enable it to regulate a target optical output power of the laser with a broad testing range and high accuracy when the feedback current is relatively high.