Light Sensor Bandwidth via Return System
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Solution Overview
Problem
Light sensors used in communications applications face a challenge in maintaining bandwidth without increasing capacitance, especially when detecting wavelengths longer than 1550 nm, as longer wavelengths require thicker germanium layers which increase capacitance.
Innovation Solution
An optical device with a light sensor and a return system that redirects a portion of the passed light signal back to the sensor, effectively increasing the sensor's length without physical expansion, thereby enhancing bandwidth without increasing capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the germanium layer thickness is increased to detect longer wavelengths, then the light absorption capability is improved, but the capacitance increases which reduces bandwidth
Solution Approach 1:
The patent introduces a temporal dimension by circulating light through the sensor multiple times via a return path, effectively increasing the interaction length without increasing the physical thickness of the germanium layer. This allows enhanced absorption of longer wavelengths while maintaining low capacitance.
Solution Approach 2:
The return system enables continuous circulation of light through the light sensor, allowing the same photons to interact with the germanium medium multiple times. This continuous action increases effective absorption path length without requiring additional material.
2Reliability
If the light sensor length is increased to improve bandwidth, then the light absorption is enhanced, but the capacitance increases which reduces bandwidth
Solution Approach 1:
The patent uses a return path configuration that extends the effective light interaction length in the temporal dimension rather than the spatial dimension. Light travels through the sensor forward and then returns through the same path, effectively doubling the interaction length without increasing sensor capacitance.
Solution Approach 2:
The return system maintains continuous light circulation through the sensor, ensuring that photons repeatedly interact with the germanium medium. This continuous circulation enhances bandwidth by increasing effective path length while keeping the physical sensor dimensions and capacitance constant.
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 allows for improved bandwidth detection of longer wavelengths without increasing the sensor's physical length or capacitance, enhancing the sensor's performance in communications applications.
Implementation Method 1
These light sensors use a light-absorbing medium that absorbs light received at the light sensor
Implementation Method 2
The bandwidth of the light sensor is the range of wavelengths that can effectively be detected by the light sensor
Implementation Method 3
The return system receives the passed light signal from the light sensor and returns at least a portion of the light from the passed light signal back to the light sensor
Data Source
AI summary
The optical device includes a light sensor positioned on a base. The light sensor is configured to receive an input light signal and outputs a passed light signal that includes light from the input light signal. The optical device also includes a return system located on the base. The return system is configured to receive the passed light signal from the light sensor and to return at least a portion of the light from the passed light signal back to the light sensor.