Avalanche Photodiode Temperature Sensing in Optical Transmitter Modules
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Solution Overview
Problem
Existing optical communication systems face challenges in precisely adjusting bias currents for semiconductor laser diodes (LDs) across a wide temperature range without the need for additional temperature sensors, which complicates the design of compact transmitter optical sub-assemblies (TOSAs).
Innovation Solution
A method that utilizes an avalanche photodiode (APD) to monitor the optical power output from the LD, where the APD is set in the same thermal condition as the LD, and by measuring specific photocurrents at different bias levels, the temperature of the LD is determined, allowing for the adjustment of bias currents accordingly, eliminating the need for a temperature sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor is installed within the TOSA to monitor temperature for precise bias current adjustment, then temperature control precision is improved, but device complexity increases due to additional lead terminals
Solution Approach 1:
The APD is designed to perform dual functions: monitoring optical power output and measuring temperature. By utilizing the same component for multiple purposes, the patent eliminates the need for separate temperature sensors and additional lead terminals, thereby reducing device complexity while maintaining measurement precision
Solution Approach 2:
The system uses its own existing components (APD and bias voltage supply) to perform temperature measurement without requiring external temperature sensors. The APD leverages its inherent temperature-dependent characteristics to self-determine the operating temperature, making the system self-sufficient
2Reliability
If additional temperature sensors and lead terminals are added to the TOSA, then temperature monitoring capability is improved, but compactness deteriorates
Solution Approach 1:
The APD serves dual purposes as both an optical power monitor and a temperature sensor. This multi-functionality eliminates the need for additional temperature sensing components and their associated lead terminals, maintaining reliable temperature monitoring while preserving the compact TOSA structure
Solution Approach 2:
The patent combines the temperature measurement function with the existing optical monitoring function by using the same APD component. This merging of functions eliminates redundant components and reduces the overall volume required for the TOSA
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 approach enables precise control of bias currents for LDs across varying temperatures without additional lead terminals, enhancing the compactness and efficiency of TOSAs while maintaining accurate temperature monitoring and optical output parameters.
Implementation Method 1
The APD monitors the amplitude of light output from the LD and generates a photocurrent corresponding to the amplitude
Implementation Method 2
the second bias sets the multiplication factor of the APD greater than the unity
Data Source
AI summary
An optical module capable of monitoring an inner temperature thereof by a simple arrangement is disclosed. The optical module installs an avalanche photodiode (APD). The APD generates the first photocurrent under a bias where the APD shows the multiplication factor thereof M equal to the unity, and the second photocurrent under another bias where the multiplication factor becomes greater than the unity. The operating temperature of the laser diode (LD) may be estimated from a ratio of the first photocurrent to the second photocurrent.