Optical Injection-Locked Laser for Low-Cost Coherent Access
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Solution Overview
Problem
Conventional coherent optical access networks face challenges due to the high cost and complexity of deploying advanced laser sources, particularly in the access network environment, where long-haul technologies are over-engineered and expensive, necessitating a cost-effective solution for providing high-quality laser sources to end users.
Innovation Solution
The implementation of Coherent Optical Injection Locking (COIL) technology, which utilizes a secondary laser locked to a primary optical source, optimizing the frequency response and threshold current of the secondary laser through rate-equation models and direct modulation techniques, enabling a lower-cost, high-performance laser source for coherent optical access networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If long-haul coherent optical technologies are implemented in access networks, then data rate and reach requirements are met, but system cost and complexity increase significantly
Solution Approach 1:
The patent uses a low-cost Fabry-Perot laser diode as a copy/clone of the expensive external cavity laser by injecting the ECL output into the FPLD cavity. This creates a 'laser clone' that replicates the narrow linewidth and phase coherence properties of the master laser while using inexpensive semiconductor laser technology, thereby reducing device complexity and cost while maintaining coherent transmission capabilities
Solution Approach 2:
The invention replaces expensive, complex external cavity lasers with cheap Fabry-Perot laser diodes that can be mass-produced. The FPLD serves as a disposable or replaceable component that provides the same functional output as the master laser, significantly reducing the cost per transceiver in the access network while maintaining the required performance for high-speed data transmission
2Reliability
If external cavity lasers are deployed throughout the access network, then high-performance laser sources are available, but material cost increases prohibitively
Solution Approach 1:
The patent merges the master laser (ECL) and slave laser (FPLD) into a single coherent system where the FPLD is injection-locked by the ECL. This combining allows the system to achieve the reliability and quality of the expensive ECL while using the inexpensive FPLD as the actual light source, dramatically reducing material cost while maintaining laser source quality through the injection locking mechanism
Solution Approach 2:
The injection-locked FPLD acts as an intermediary between the expensive ECL and the optical fiber transmission medium. It translates the high-quality coherent signal from the ECL into a format suitable for cost-effective mass production and deployment, serving as a mediator that preserves signal quality while reducing the need for expensive laser components throughout the network
3Ease of manufacture
If Fabry-Perot laser diodes are used instead of external cavity lasers, then cost is reduced, but laser source quality and performance decrease
Solution Approach 1:
The injection locking mechanism provides optical feedback from the master ECL to the slave FPLD, forcing the FPLD to oscillate at the same frequency and phase as the ECL. This feedback mechanism overrides the inherent quality limitations of the FPLD, enabling it to produce high-quality coherent light despite its simple, low-cost construction, thus resolving the contradiction between ease of manufacture and laser source quality
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
COIL technology significantly reduces the material cost of laser sources in access networks by transforming lower-quality secondary lasers into high-performance ones, enhancing modulation bandwidth and frequency response, thus supporting high-speed data transmission while maintaining cost-effectiveness.
Implementation Method 1
COIL operates on the principle that a secondary semiconductor laser (e.g., a downstream laser source) may be locked to frequency and phase of an externally-injected primary optical source (e.g., an upstream laser source). Through this COIL technique, the secondary laser source, which may be of considerably lower-cost and lower-quality laser (e.g., a Fabry-Perot laser diode (FPLD)) than the primary optical source (e.g., an external cavity laser (ECL)), may be effectively turned into a high-performance narrow linewidth laser by injecting light from the high quality primary optical source into the cavity of the lower quality secondary laser.
Data Source
AI summary
An injection locking laser source is provided for an optical communications system. The injection locking laser source includes a laser cavity configured to receive an externally injected low linewidth primary light source. The laser cavity includes a cavity length, a cavity facet reflectivity, and a cavity quality factor. The injection locking laser source further includes an emitting region configured to output a secondary light source injection locked to the externally injected low linewidth primary light source at a stable detuning frequency based on a photon number, a steady-state phase, and a carrier number of the primary light source injected into the cavity.