Optical Module Stray Light Shielding for Photodetector Noise Reduction
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Solution Overview
Problem
Existing optical modules suffer from stray light interference, which deteriorates the photosensitivity of photodetectors due to unaddressed back stray light and light diffraction from optical elements, leading to signal noise and errors in optical communications.
Innovation Solution
The optical module incorporates a stray light reducing unit, including light absorbers or scatterers on inner package surfaces and a first stray light shield at the rear of the laser light source, combined with optical branching and photodetecting elements to block and absorb stray light, thereby preventing its entry into photodetectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If optical elements are used to guide light from the laser light source, then light transmission is achieved, but the optical elements generate stray light that may be diffracted into the photodiode
Solution Approach 1:
The patent extracts the stray light blocking function from the optical guidance path by introducing dedicated stray light shields positioned around optical elements. These shields are separate from the light-guiding optical elements themselves, allowing the optical elements to perform their guidance function while the shields independently intercept stray light generated by these elements before it can diffract into the photodiode.
2Object-affected harmful factors
If multiple stray light shields and light absorbers are added to the package, then stray light is effectively blocked, but the device complexity increases
Solution Approach 1:
The patent designs stray light shields that serve multiple functions: blocking back stray light from the laser light source, blocking front stray light, and preventing stray light from optical elements. By making these shields multi-functional, the patent reduces the need for separate components for each function, thereby managing device complexity while achieving comprehensive stray light suppression.
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 significantly reduces stray light interference, enhancing the signal-to-noise ratio and maintaining the photosensitivity of photodetectors, as demonstrated by the comparative examples showing decreased stray light intensity received by photodetectors in the optical module.
Implementation Method 1
The stray light reducing unit is a light absorber or light scatterer formed in at least a part of an inner surface of the package
Implementation Method 2
The stray light reducing unit is a light absorber or light scatterer formed in at least a part of an inner surface of the package
Implementation Method 3
the optical element is an MMI (Multi-mode interference) coupler
Implementation Method 4
a photodetector for receiving light output from the laser light source
Data Source
AI summary
An optical module 10 has a laser light source 20, optical branching means 24 for receiving laser light from the laser light source 20, making a part of the laser light pass through the optical branching means and branching a remaining part of the laser light; a photodetecting portion 30P receiving the remaining part of the laser light branched from the optical branching means 24 and a package 11 holding therein the laser light source 20, the optical branching means 24 and the photodetecting portion 30P, the package 11 having stray light reducing means 200, 201 and 202 provided therein to reduce stray light generated inside the package.