Mode Conversion for Optical Isolation Using HCG Lens
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Solution Overview
Problem
High-speed optical communication systems face challenges in achieving sufficient coupling efficiency due to eye safety requirements, leading to increased relative intensity noise (RIN) and modulation extinction ratios, particularly at data communication speeds of 25 Gbps or higher.
Innovation Solution
The use of a planar high-contrast grating (HCG) lens to convert optical modes into a mode-isolating intensity profile, spatially isolating higher-order modes and reducing the coupling of reflected optical energy back into the optical signal source, thereby mitigating RIN.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If optical coupling is implemented with low coupling efficiency to meet eye safety requirements, then eye safety is improved, but relative intensity noise and modulation extinction ratios worsen
Solution Approach 1:
The patent introduces a mode converter as an intermediary optical element between the laser source and the optical fiber. This mode converter transforms the fundamental optical mode into higher-order modes, which are then spatially filtered by an aperture to block reflected light from returning to the laser, thereby improving signal quality while maintaining eye safety compliance
Solution Approach 2:
The patent utilizes spatial dimensionality by converting optical modes to create a specific intensity profile where energy is distributed away from the central axis. This dimensional transformation allows the aperture to effectively block reflected light paths while preserving forward-propagating signal energy, resolving the contradiction between safety and signal quality
2Reliability
If higher coupling efficiency is implemented to mitigate receiver noise, then signal quality is improved, but eye safety requirements are violated
Solution Approach 1:
The patent converts the harmful effect of reflected optical energy back into the laser source by using mode conversion and spatial filtering. The aperture blocks the reflected higher-order modes, and this blocked energy is effectively converted into a beneficial effect by preventing RIN generation, thereby improving signal quality without compromising eye safety
3Reliability
If mode conversion is implemented to spatially isolate higher-order modes, then reflected light coupling is reduced, but device complexity increases
Solution Approach 1:
The patent changes the optical mode parameters (from fundamental mode to higher-order modes) using a mode converter, which creates a specific intensity profile. This parameter transformation enables spatial isolation of modes that can be filtered by a simple aperture, achieving noise mitigation without requiring complex active control systems
Solution Approach 2:
The patent segments the optical energy distribution by creating distinct spatial regions through mode conversion. The intensity profile separates signal energy from reflected light paths, allowing simple geometric filtering by an aperture without requiring complex adaptive optics or active feedback mechanisms
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 enhances coupling efficiency and reduces RIN, allowing for effective high-speed optical communication systems by isolating optical energy away from the aperture, thus improving signal quality and noise mitigation.
Implementation Method 1
The use of a planar high-contrast grating (HCG) lens to convert optical modes into a mode-isolating intensity profile
Implementation Method 2
The use of a planar high-contrast grating (HCG) lens to convert optical modes into a mode-isolating intensity profile
Implementation Method 3
The converted optical signal is focused to the optical element via the substantially planar HCG lens
Data Source
AI summary
An optical coupling system includes an optical signal source to provide an optical signal from an aperture. The system also includes a substantially planar high-contrast grating (HCG) lens to convert an optical mode of the optical signal to provide a converted optical signal having a mode-isolating intensity profile. The system further includes an optical element to receive the converted optical signal. The optical signal source and the substantially planar HCG lens can be arranged to substantially mitigate coupling of a reflected optical signal associated with the converted optical signal that is reflected from the optical element to the aperture of the optical signal source based on a reflected mode-isolating intensity profile.