Laser Diode Control Circuit Extinction Ratio Feedback
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Solution Overview
Problem
The output light density versus input current characteristic curve of laser diodes in optical communication systems varies with aging or temperature changes, leading to degraded data quality and throughput without proper current control.
Innovation Solution
A laser diode control circuit with a feedback control loop that includes a driver circuit, DC component remover, conversion and filter circuits, rectifiers, a reference signal generator, and a comparator to adjust the driving signal amplitude based on detected light, maintaining the extinction ratio and improving signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If proper control of input current is implemented, then data quality and throughput are maintained, but device complexity increases due to additional control circuits
Solution Approach 1:
The patent implements a feedback control mechanism where the optical detection circuit monitors the light output from the laser diode and feeds this information back through the rectifier and comparator circuits to automatically adjust the driving signal amplitude, thereby maintaining data quality without manual intervention
Solution Approach 2:
The control circuit automatically compensates for L-I curve variations caused by aging or temperature changes by using the feedback from the optical detection circuit, enabling the system to self-correct and maintain optimal performance without external control
2Stability of the object's composition
If feedback control loop with rectifiers is added, then extinction ratio is maintained over temperature and aging, but device complexity increases
Solution Approach 1:
The feedback control loop continuously monitors the optical output and adjusts the driving signal to compensate for drift in the extinction ratio caused by temperature changes and aging, maintaining stable performance over time
Solution Approach 2:
The rectifier circuits convert the optical signal parameters into electrical signals that can be processed by the comparator, enabling automatic adjustment of the driving signal parameters to maintain extinction ratio stability
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 maintains the extinction ratio of the laser diode over temperature and aging changes, enhancing the signal quality and data transmission in optical communication systems.
Implementation Method 1
a detected signal generated by an optical detection circuit and proportional to an amount of light generated by the laser diode
Implementation Method 2
a first rectifier arranged to operably rectify the first filtered signal to generate a first rectified signal; a second rectifier arranged to operably rectify the second filtered signal to generate a second rectified signal
Data Source
AI summary
A laser diode control circuit includes: a LD driver circuit for driving a laser diode; a direct current component remover circuit for generating a feedback signal based on a detected signal; a first conversion and filter circuit for generating a first filtered signal based on the feedback signal; a first rectifier for rectifying the first filtered signal to generate a first rectified signal; a reference signal generator for generating a reference signal; a second conversion and filter circuit for generating a second filtered signal based on the reference signal; a second rectifier for rectifying the second filtered signal to generate a second rectified signal; a rectified signals processing circuit for generating a processed signal based on the first and second rectified signals; and a comparator for generating a comparison signal based on the processed signal.