VCSEL Optical Coupling Misalignment to Reduce Back Reflection
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Solution Overview
Problem
Conventional optical communication links face challenges in increasing data throughput due to power budget constraints, as existing low-cost optical coupler designs and source devices struggle to enhance optical signal power and reduce attenuation, leading to destabilization of the optical signal from coherent feedback.
Innovation Solution
The proposed solution involves an optical communication system with a VCSEL, transition lens, and optical medium, where controlled misalignment of the axes, such as angular adjustments or offsets, is used to minimize back reflections, reducing the likelihood of destabilizing feedback by ensuring the reflected optical signal does not return to the VCSEL.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If source signal power is increased to achieve higher data rates, then data throughput is improved, but coherent feedback from reflected optical signals destabilizes the optical signal
Solution Approach 1:
The optical axis of the transition lens is intentionally misaligned relative to the axis connecting the VCSEL and the optical fiber end. This asymmetric arrangement causes reflected optical signals to follow a different path back to the VCSEL, reducing coherent feedback. The misalignment creates angular deviation between the incident and reflected ray paths, preventing the reflected signal from returning coherently to the VCSEL cavity.
Solution Approach 2:
The invention converts the harmful effect of optical reflection into a beneficial outcome by using the reflection path itself to divert the feedback. Instead of trying to eliminate reflection, the misaligned lens arrangement exploits the reflected ray geometry to ensure that reflected signals are redirected away from the VCSEL, transforming the harmful coherent feedback into a harmless or even useful scattering effect.
2Ease of operation
If conventional coaxial alignment is used to maximize coupling efficiency, then coupling tolerance is improved, but reflected optical signals return to the VCSEL causing destabilization
Solution Approach 1:
The patent deliberately introduces asymmetry by misaligning the transition lens optical axis relative to the VCSEL-fiber axis. This asymmetric configuration breaks the symmetry of the optical path, causing reflected rays to return at different angles and positions, thereby reducing coherent feedback while maintaining acceptable coupling efficiency through optimized misalignment parameters.
3Power
If attenuation is decreased to improve signal strength, then data rate capability is improved, but susceptibility to feedback destabilization increases
Solution Approach 1:
The invention converts the potentially harmful reflected optical signals into a beneficial configuration where the reflection paths are geometrically separated from the VCSEL input. By using the misaligned lens to redirect reflected rays away from the VCSEL, the system can operate with lower attenuation while avoiding feedback-induced destabilization, effectively turning the reflection problem into a solution.
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 effectively reduces the destabilizing impact of coherent feedback, enhancing the stability of the optical signal and maintaining reliable data transfers at higher data rates without increasing susceptibility to undesirable feedback.
Implementation Method 1
Due to the difference in the index of refraction of air and the material used to produce the transition lens 20, when the ray 12 reaches the left-facing convex surface of the transition lens 20, the ray 12 is refracted (i.e., redirected).
Implementation Method 2
a remaining portion of the twice redirected optical signal incident at the end face 31, represented by ray 32, is reflected toward transition lens 20
Data Source
AI summary
An optical communication system includes a transceiver with a light source, a transition lens and an optical medium. Each of the light source, the transition lens and the optical medium define a corresponding axis. The light source defines a normal launch axis. The transition lens defines an optical axis. The optical medium defines a longitudinal axis. A relative misalignment from a coaxial alignment of the corresponding axes of at least one the light source, the transition lens and the optical medium is used to reduce a back reflection incident at the light source. Such misalignments can be achieved by one or both of angular adjustments and offsets of the axes.