Shared Wavelength Locker with Periodic Filter for DWDM
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Solution Overview
Problem
Conventional wavelength division multiplexing (WDM) transmitter arrays face challenges in efficient and cost-effective wavelength locking, especially as the number of transmitters increases, leading to higher complexity and cost, and limited reach due to manufacturing variations and temperature effects.
Innovation Solution
A shared periodic transmission filter, such as an etalon, is used for wavelength locker operations and spectral shaping of optical transmitter signals, enabling wavelength stability and longer reach for directly modulated lasers (DMLs) in DWDM networks through quadrature detection techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wavelength locker is used for each laser in discrete transmitters, then wavelength stability is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines multiple wavelength locking functions into a single shared wavelength locker that serves multiple lasers simultaneously. This is achieved by implementing a common feedback system that monitors and adjusts the wavelengths of multiple laser sources using shared optical components and control electronics, thereby reducing device complexity and cost while maintaining wavelength stability across all transmitters.
Solution Approach 2:
The wavelength locker is designed to perform multiple functions by serving as a universal locking mechanism for all laser transmitters in the array. The system uses a common reference cavity and feedback control that can accommodate multiple laser wavelengths, allowing a single device to provide wavelength stabilization across the entire transmitter array rather than requiring dedicated lockers for each laser.
2Length of moving object
If extensive engineering is done on lasers to extend reach, then transmission reach is improved, but transmitter cost increases
Solution Approach 1:
The patent introduces an external periodic transmission filter as an intermediary component that extends transmission reach without requiring complex modifications to the laser itself. The filter acts as a mediator that shapes the optical spectrum and enables longer reach by filtering out unwanted frequency components, while the simple feedback mechanism adjusts laser wavelength to maintain alignment with the filter's transmission peak, keeping transmitter cost low.
Solution Approach 2:
The system extends transmission reach by dynamically adjusting the laser operating wavelength parameter to align with the transmission peak of the external periodic filter. This parameter change approach allows the system to optimize for longer reach by operating at the filter's peak transmission wavelength, rather than requiring extensive laser engineering, thereby maintaining cost-effectiveness.
3Ease of manufacture
If directly modulated lasers are used for inexpensive transmitters, then transmitter cost is reduced, but transmission reach becomes short
Solution Approach 1:
The patent applies feedback control to inexpensive directly modulated lasers by implementing a wavelength locker that monitors the laser output wavelength and provides corrective feedback to maintain alignment with the transmission filter's peak. This feedback mechanism compensates for the inherent wavelength instability of low-cost DMLs, enabling them to achieve extended transmission reach without requiring expensive laser engineering, thus maintaining cost-effectiveness while improving reach.
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 reduces dispersion by aligning the adiabatic logical one position with the spectral transmission peak, minimizing transient chirp and adiabatic chirp, thereby enhancing the performance and reach of DML-based transmitters while maintaining cost-effectiveness.
Implementation Method 1
A shared periodic transmission filter (e.g., an etalon) is used for wavelength locker operations and for spectrally shaping optical transmitter signals
Implementation Method 2
One approach to provide wavelength locking has been to employ a feedback system to compare actual laser output wavelength to the target laser output wavelength
Implementation Method 3
The processor is also configured to perform wavelength locking based on a quadrature detection technique that aligns an adiabatic logical one position of a modulated transmission signal with a spectral transmission peak of the period transmission filter
Data Source
AI summary
An apparatus comprising a plurality of optical transmitters and a wavelength locker shared by the plurality of optical transmitters. A periodic transmission filter used for wavelength locker operations is in a network communication path and shapes optical transmissions from the plurality of optical transmitters to a network. An apparatus comprising at least one processor configured to receive a pre-filter signal corresponding to part of an optical signal comprising a pilot tone and to receive a post-filter signal corresponding to a part of the optical signal that passes through a period transmission filter, wherein a filtered part of the optical signal is directed into a network. The processor is also configured to perform wavelength locking based on a quadrature detection technique that aligns an adiabatic logical one position of a modulated transmission signal with a spectral transmission peak of the period transmission filter.