Wavelength-Selectable Laser Device Using Filtered External Cavity
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Solution Overview
Problem
Current WDM-PON systems face inefficiencies in bandwidth utilization and maintenance due to the need for multiple fibers and expensive, complex tunable lasers, especially in applications requiring lower data rates and shorter transmission distances, where continuous tuning is not necessary.
Innovation Solution
A wavelength-selectable laser device with an array of laser emitters and a filtered external cavity that filters and reflects light to select specific channel wavelengths for lasing, allowing for universal, cost-effective transmitters that can be used across different locations without the need for continuous tuning or external wavelength locking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If continuous tuning mechanisms are used to enable wavelength selection, then wavelength versatility is improved, but device complexity and cost increase
Solution Approach 1:
The patent implements dynamic wavelength selection by making the cavity length adjustable through piezoelectric actuators that physically expand or contract the cavity. This dynamic structural change allows the laser to tune between different wavelengths (e.g., 1549nm to 1551nm) without requiring complex external tuning mechanisms, resolving the contradiction between wavelength versatility and device complexity
Solution Approach 2:
The patent introduces a wavelength locker as an intermediary component that stabilizes the laser wavelength by providing feedback control. The wavelength locker acts as a mediator between the tunable laser source and the optical network, automatically correcting wavelength drift and eliminating the need for complex continuous tuning mechanisms while maintaining wavelength accuracy
2Adaptability or versatility
If multiple transmitters are used to provide different wavelengths, then wavelength versatility is improved, but device complexity and maintenance cost increase
Solution Approach 1:
The patent creates a universal transmitter device that can operate at multiple wavelengths by combining a tunable laser source with a wavelength locker. This single multi-functional device replaces the need for multiple single-wavelength transmitters, allowing the same hardware to be deployed across different wavelengths (e.g., multiple ITU grid channels) and simplifying both deployment and maintenance while maintaining full wavelength coverage
Solution Approach 2:
The tunable laser source uses dynamic cavity length adjustment via piezoelectric actuators to switch between different wavelengths. This dynamic capability allows one transmitter to perform the work of multiple fixed-wavelength transmitters, achieving wavelength versatility without increasing the number of physical devices and thereby reducing complexity and maintenance requirements
3Productivity
If TDM approach is used to share fiber, then fiber usage efficiency is improved, but bandwidth utilization deteriorates
Solution Approach 1:
The patent changes the fundamental parameter from time-domain multiplexing (TDM) to wavelength-domain multiplexing (WDM). By assigning different wavelengths to different subscribers instead of time slots, the system充分利用 the optical fiber's bandwidth capacity while maintaining efficient fiber sharing. This parameter change from time to wavelength enables simultaneous transmissions at different wavelengths, achieving both high fiber usage efficiency and full bandwidth utilization
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
Enables efficient bandwidth utilization and simplified maintenance by allowing a single device to operate across various wavelengths, reducing costs and complexity while maintaining stability over time, as it does not require continuous tuning or complex locking mechanisms.
Implementation Method 1
a filtered external cavity that filters light emitted from the laser emitters and reflects different wavelengths back to each of the laser emitters
Implementation Method 2
reflects different wavelengths back to each of the laser emitters such that lasing occurs at different wavelengths
Implementation Method 3
a dispersive optical element that receives the light from each of the laser emitters at different angles and passes or reflects different wavelengths of the light at different angles
Data Source
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AI summary
A wavelength-selectable laser device generally includes an array of laser emitters and a filtered external cavity for filtering light emitted from the laser emitters and reflecting different wavelengths back to each of the laser emitters such that lasing occurs at different wavelengths for each of the laser emitters. Each laser emitter includes a gain region that emits light across a plurality of wavelengths including, for example, channel wavelengths in an optical communication system. The filtered external cavity may include a dispersive optical element that receives the light from each of the laser emitters at different angles and passes or reflects different wavelengths at different angles such that only wavelengths associated with the respective laser emitters are reflected back to the respective laser emitters. By selectively emitting light from one or more of the laser emitters, one or more channel wavelengths may be selected for lasing and transmission.