Injection-Locked Laser Diode for Optical Beat Interference Reduction
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Solution Overview
Problem
Current fiber communication networks face challenges in increasing bandwidth and minimizing capital and operational expenditures, particularly due to limitations in receiver sensitivity and scalability of WDM technology, especially in legacy fiber environments, and suffer from optical beat interference (OBI) when multiple services coexist.
Innovation Solution
The system employs an optical circulator to collect a seed source spanning a wavelength range and directs it to a laser diode, which outputs a signal primarily within that range, using injection locking and external modulation to minimize OBI, allowing for simultaneous upstream communications from multiple devices without dedicated wavelengths, and uses a filter to separate seed sources and downstream signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If WDM technology is used to increase network capacity, then bandwidth is improved, but receiver sensitivity deteriorates
Solution Approach 1:
The patent changes the operating parameters by using coherent detection instead of direct detection, and by employing advanced modulation formats (QPSK, 16-QAM, 64-QAM) to improve spectral efficiency and receiver sensitivity while maintaining high network capacity through WDM
2Measurement precision
If coherent technology is used to improve receiver sensitivity, then receiver sensitivity is improved, but system complexity increases
Solution Approach 1:
The patent segments the coherent detection system into separate functional blocks: optical circulator for signal routing, laser diode for coherent light generation, external modulator for signal modulation, and filter for wavelength selection. This modular segmentation reduces system complexity by making each component's function clear and manageable
3Adaptability or versatility
If multiple services coexist in the network, then network versatility is improved, but optical beat interference increases
Solution Approach 1:
The patent introduces an optical circulator as an intermediary device that manages signal routing between different services and wavelength channels. This intermediary prevents direct interaction between competing signals, thereby reducing optical beat interference while allowing multiple services to coexist
Solution Approach 2:
The patent extracts and separates signals of different wavelengths using filters and the optical circulator, isolating each service's signal path. This separation removes the harmful interaction between simultaneous signals from different services, eliminating optical beat interference
4Reliability
If dedicated wavelengths are assigned to each device, then communication reliability is improved, but device complexity increases
Solution Approach 1:
The patent makes the laser diode universal by enabling it to operate at multiple wavelengths through coherent detection and external modulation. Instead of requiring dedicated wavelength-specific laser diodes for each device, a single laser diode can be tuned to different wavelengths, reducing device complexity while maintaining reliable communication
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 receiver sensitivity, reduces OBI, and allows for efficient use of existing fiber infrastructure by enabling simultaneous and coherent upstream communications across multiple services, thereby increasing network capacity and reducing costs.
Implementation Method 1
an optical circulator configured to collect a seed source spanning a wavelength range and direct the seed source to a laser diode
Implementation Method 2
the laser diode configured to output a signal including primarily the wavelength range based on collecting the seed source at the laser diode
Implementation Method 3
an external modulator configured to modulate the signal output by the laser diode, where the optical circulator is further configured to collect the modulated signal
Implementation Method 4
uses a filter to separate seed sources and downstream signals
Data Source
AI summary
Methods, systems, and devices for network communications to reduce optical beat interference (OBI) in upstream communications are described. For example, a fiber node may provide a seed source to injection lock upstream laser diodes. Therefore, upstream communications from each injection locked laser diode may primarily include the wavelength associated with each seed source. The seed sources may be unique to each end device and configured to minimize OBI. That is, the upstream laser diodes may be generic, but the collected seed source may enable upstream communications at varying wavelengths. The end device may provide upstream communications by externally modulating a signal generated by the injection locked laser diode.