Adjustable Termination Circuit for High Speed Laser Driver Impedance
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Solution Overview
Problem
Current high speed laser drivers for optical communication face challenges in maintaining optimal output impedance stability and bandwidth control due to fixed resistance configurations, which are not suitable at all operating conditions.
Innovation Solution
An adjustable termination circuit is introduced, comprising a power source, offset resistor, operational amplifier, and transistor, allowing for dynamic adjustment of output impedance by generating an offset voltage and current, which sums with the termination resistor impedance to control the total output impedance seen by the semiconductor laser.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed termination resistor is used to match transmission impedance, then signal quality is improved, but output impedance stability and bandwidth control deteriorate
Solution Approach 1:
The patent transforms the static fixed termination resistor into a dynamic adjustable termination circuit. The circuit uses an operational amplifier, transistor, and control voltage to dynamically adjust the termination resistance value, allowing the output impedance to be optimized for different operating conditions while maintaining signal quality and improving stability.
Solution Approach 2:
The patent changes the resistance parameter from a fixed value to a variable value that can be adjusted based on operating conditions. By controlling the transistor's base voltage, the termination resistance can be varied to match different transmission impedances, thereby improving both signal quality and output impedance stability across different operating points.
2Device complexity
If a fixed termination resistor is used, then circuit simplicity is maintained, but bandwidth control and adaptability deteriorate
Solution Approach 1:
The patent introduces dynamic control capability to the termination circuit, enabling bandwidth optimization. The operational amplifier and transistor combination allows the termination resistance to be adjusted dynamically, providing bandwidth control while adding only moderate circuit complexity compared to the fixed resistor approach.
3Ease of manufacture
If a fixed termination resistor is used, then manufacturing simplicity is maintained, but performance optimization under varying operating conditions deteriorates
Solution Approach 1:
The patent enables performance optimization by allowing the termination resistance parameter to change based on operating conditions. The circuit uses standard electronic components (operational amplifier, transistor, resistors) that can be manufactured using conventional processes, while providing the capability to optimize performance across different laser operating points and transmission conditions.
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 provides improved output impedance stability and bandwidth control, enabling optimal performance by dynamically matching the output impedance to the transmission impedance, thus enhancing signal quality and operational range.
Implementation Method 1
The operational amplifier may then be configured to drive such input offset voltage to zero
Implementation Method 2
the operational amplifier is configured to induce the transistor to provide a termination current in response to the input offset voltage at the input of the operational amplifier
Implementation Method 3
one of its inputs is electrically connected in series between the power source and the offset resistor such that the input current provided by the power source to the offset resistor generates an input offset voltage across the inputs of the operational amplifier
Data Source
AI summary
Disclosed is a circuit having a high speed laser driver circuit, a semiconductor laser electrically connected to the high speed laser driver circuit, and an adjustable termination circuit electrically connected between the high speed laser driver circuit and the semiconductor laser, where the adjustable termination circuit is configured to control an output impedance seen by the semiconductor laser as a function of an input current provided to the adjustable termination circuit.