Injection-Locked Laser Array for Lower-Cost Coherent FSO Links
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Solution Overview
Problem
Conventional FSO systems face high costs due to the use of external cavity lasers, require complex hardware for conversion, and are prone to deep fades, making them impractical for widespread implementation, especially in rural areas and short-haul networks.
Innovation Solution
Implement an optical emission array with a parent laser source and multiple child laser emitters that are injection-locked to the parent, using optical distribution branches to connect them, eliminating the need for separate LO sources and reducing hardware complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external cavity lasers are used in conventional FSO systems, then transmission quality is improved, but hardware cost increases significantly
Solution Approach 1:
The patent uses a single high-quality external cavity laser (ECL) as a parent source and creates multiple copies through optical distribution branches to multiple child laser emitters. The child lasers are injection-locked to the parent ECL, copying its high-quality optical properties without requiring each child laser to be a separate ECL, thus reducing hardware cost while maintaining transmission quality.
Solution Approach 2:
The system segments the laser source function into a parent ECL that generates the high-quality optical signal and multiple child lasers that distribute and transmit the signal. This segmentation allows the expensive ECL to be used only once as a parent source, while cheaper child lasers handle the distribution, resolving the cost-quality contradiction.
2Measurement precision
If separate LO sources are used for each receiver, then receiver sensitivity is improved, but hardware complexity increases
Solution Approach 1:
The patent merges the function of multiple local oscillator (LO) sources into a single parent ECL. All child lasers are injection-locked to this single parent source, which serves as the common LO for all receivers. This merging maintains receiver sensitivity through coherent detection while eliminating the need for multiple separate LO sources, thus reducing hardware complexity.
Solution Approach 2:
The parent ECL serves multiple functions simultaneously: it is the optical source for the FSO transmission and the local oscillator for all coherent receivers. This multi-functionality eliminates the need for separate LO sources at each receiver, reducing hardware complexity while maintaining receiver sensitivity through coherent detection.
3Adaptability or versatility
If conventional FSO systems are deployed, then communication coverage is achieved, but susceptibility to deep fades increases
Solution Approach 1:
The injection locking mechanism provides feedback from the parent ECL to each child laser through optical distribution branches. This feedback ensures that all child lasers maintain phase coherence with the parent source, enabling coherent detection at the receivers. The phase-synchronized signals from multiple child lasers can be combined constructively, improving reliability and reducing susceptibility to deep fades while maintaining communication coverage.
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 significantly reduces hardware costs, enhances receiver sensitivity, and improves transmission efficiency by phase-synchronizing child lasers to a high-quality parent source, enabling cost-effective coherent optical systems for complex geographical scenarios.
Implementation Method 1
an optical emission array with a parent laser source and multiple child laser emitters that are injection-locked to the parent, using optical distribution branches to connect them
Data Source
AI summary
An optical emission array includes an optical input portion configured to provide a parent laser source for the optical emission array, and an optical output portion including a plurality of child laser emitters. Each child laser emitter of the plurality of child laser emitters is injection-locked to the parent laser source. The optical emission array further includes at least two optical distribution branches (i) disposed between the optical input portion and the optical output portion, and (ii) optically connecting at least two child laser emitters of the plurality of child laser emitters, respectively, to the parent laser source.