Multi-wavelength Tunable Laser Array for Nanosecond Optical Packet Switching
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Solution Overview
Problem
Fast tunable lasers are required to fully benefit from optical packet switching in WDM networks, but existing lasers cannot be switched as quickly as a few nanoseconds and maintain a narrow linewidth for optimal coherent receiver operation.
Innovation Solution
A wavelength-tunable optical transmission device with a multi-wavelength array chip comprising DFB laser sources, using optical combiners and a control unit to perform time-offset tuning and sending sequences, allowing for rapid wavelength tuning of laser sources within tens or hundreds of nanoseconds, enabling efficient optical packet transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional tunable lasers are used, then wavelength tuning capability is provided, but the switching speed is too slow (cannot be switched as fast as a few nanoseconds)
Solution Approach 1:
The patent divides the laser system into multiple independent laser sources (e.g., 12 DFB laser sources) arranged in an array. Each laser source can be independently controlled and tuned, allowing parallel operation where one laser transmits while another tunes, thereby achieving fast switching without compromising the stability of the transmitting laser's linewidth.
Solution Approach 2:
The patent implements preliminary tuning action by pre-tuning the wavelength of a laser source before it is selected for transmission. The control unit prepares the next laser source in the sequence by tuning it to the required wavelength in advance, so that when switching is needed, the pre-tuned laser can immediately take over, achieving nanosecond-scale switching speed.
2Speed
If fast tuning is implemented, then switching speed improves, but maintaining narrow linewidth for coherent reception becomes difficult
Solution Approach 1:
By segmenting the laser system into multiple independent sources, the patent allows one laser to maintain stable transmission with narrow linewidth while another laser performs rapid tuning. The transmitting laser's linewidth stability is preserved because it is not undergoing tuning during transmission, resolving the conflict between fast tuning and linewidth precision.
Solution Approach 2:
The patent employs periodic action by alternately selecting different laser sources from the array in a time-offset manner. Each laser source is tuned and then used for transmission during its designated time slot, while other lasers are being tuned in parallel. This periodic switching allows fast tuning cycles without compromising the linewidth stability of the actively transmitting laser.
3Adaptability or versatility
If multiple laser sources are used to span total wavelength range, then wavelength coverage improves, but device complexity increases
Solution Approach 1:
The patent segments the wavelength coverage task across multiple laser sources, each responsible for a portion of the total wavelength range. This segmentation allows the system to achieve broad wavelength coverage (e.g., 32 nm in C band) while keeping each individual laser source relatively simple and well-established in technology.
Solution Approach 2:
The patent merges multiple laser sources into a unified array structure with common control and output coupling. The control unit manages all laser sources through a standardized interface, and optical combiners merge the outputs of multiple lasers into a single transmission path. This merging approach achieves broad wavelength versatility while maintaining manageable system complexity through modular architecture.
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 rapid wavelength tuning of laser sources, optimizing inter-packet intervals and network capacity, while maintaining stable narrow linewidths for coherent receivers, thereby enhancing the efficiency of optical packet switching in WDM networks.
Implementation Method 1
a first optical combiner arranged to guide the optical signals generated by a first subset of the laser sources to a first optical gate
Implementation Method 2
a multi-wavelength array chip including a plurality of laser sources, each laser source being tunable over a respective fine range of wavelengths
Implementation Method 3
the optical modulator is adapted to modulate the optical signals in accordance with a multilevel Quadrature Amplitude Modulation scheme
Data Source
Figure 1~3
AI summary
A wavelength-tunable optical transmission device (1) comprising: a multi-wavelength array chip including a plurality of laser sources (DFB1, ... DFB 12), each laser source being tunable over a respective fine range of wavelengths of the laser source, a first optical combiner (2) arranged to guide the optical signals generated by a first subset of the laser sources to a first optical gate (3), a second optical combiner (4) arranged to guide the optical signals generated by a second subset of the laser sources to a second optical gate (5), and a transmission controller (8) adapted to perform repeatedly a first tuning and sending sequence and a second tuning and sending sequence in a time-offset manner to send optical packets with the first subset of the laser sources and with the second subset of the laser sources at different instants in time on different wavelength channels located within the total range.