Space-Division Multiplexed Wavelength Selective Switch Architecture
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Solution Overview
Problem
Conventional wavelength selective switches (WSSs) face challenges in scalability and signal quality when handling space division multiplexed signals, particularly due to passband distortion and reduced capacity, especially when dealing with multimode fibers, which limits the number of wavelength channels and overall switch capacity.
Innovation Solution
A reconfigurable, space-division multiplexed wavelength-selective switch architecture that includes an optical input port, a demultiplexer, reconfigurable wavelength-selective optical switches with dispersive and controllable beam steering elements, and optical multiplexers to manage and route wavelength division multiplexed signals across multiple spatial modes, allowing for a higher port count and improved scalability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wavelength selective switches are used to route signals carried by multimode fibers, then the switch can handle wavelength division multiplexed signals, but the different modes propagate differently after entering the free-space optics, leading to passband distortion and reduced switch capacity
Solution Approach 1:
The patent segments the multimode fiber signal into individual mode components using a mode demultiplexer, processes each mode separately through wavelength selective switches, and then recombines them. This segmentation prevents the different modes from interfering with each other in the free-space optics, eliminating passband distortion while maintaining high switch capacity.
Solution Approach 2:
The patent introduces a mode demultiplexer and mode multiplexer as intermediary devices between the multimode fiber and the wavelength selective switch. These intermediaries transform the multimode signal into separate single-mode signals for switching, and then recombine them, acting as a mediator that prevents mode-dependent passband distortion while enabling high-capacity wavelength routing.
2Productivity
If the number of wavelength channels is increased to improve switch capacity, then more channels can be routed, but the spectral guard-bands must be widened to accommodate mode-dependent passband shapes, which reduces the number of available wavelength channels
Solution Approach 1:
By segmenting the multimode signal into separate mode components and processing each mode independently, the patent eliminates mode-dependent passband distortion. This allows wavelength channels to be packed more closely together without requiring widened spectral guard-bands, thereby increasing the number of available wavelength channels and overall switch capacity.
3Device complexity
If spatial modes are kept together in the conventional WSS architecture, then the device structure is simpler, but the beams of different modes have different shapes on the switching plane leading to passband distortion
Solution Approach 1:
The patent segments the combined multimode beam into separate spatial mode components using a mode demultiplexer before they enter the wavelength selective switch. This segmentation ensures that each mode is processed as a distinct entity with its own optimized beam shape on the switching plane, eliminating passband distortion while the overall device structure remains integrated and manageable.
Solution Approach 2:
The patent applies local quality optimization by ensuring that each spatial mode component has its own optimized beam profile and switching characteristics on the LCOS plane. This allows each mode to be switched with optimal passband quality tailored to its specific spatial characteristics, rather than forcing all modes to share a single suboptimal beam shape.
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
The proposed solution enables efficient handling of a large number of modes with high port count, maintaining signal quality and capacity by keeping spatial modes together to prevent interference, thus enhancing the overall performance and capacity of optical switches in telecommunication systems.
Implementation Method 1
a diffractive element to disperse a wavelength division multiplexed (WDM) optical signal received at the input port into a plurality of wavelength components spatially along a first axis
Implementation Method 2
a controllable beam steering element to steer each wavelength component to a selected output port
Data Source
AI summary
We describe a space-division multiplexed (SDM) fibre, reconfigurable, wavelength-selective switch (WSS). The switch comprises a space-division multiplexed (SDM) optical input port to receive a space-division multiplexed (SDM) optical input signal comprising a plurality of space division modes each of said space division modes carrying a respective data signal, wherein each of said space division modes is also wavelength division multiplexed (WDM); an optical space division demultiplexer, coupled to said input port, to split said space-division multiplexed (SDM) optical input signal into a plurality of space division demultiplexed optical signals on separate demultiplexer outputs of said demultiplexer, each said demultiplexer output of said demultiplexer comprising a wavelength division multiplexed one of said plurality of space division modes; a set of reconfigurable wavelength-selective optical switches, each reconfigurable wavelength-selective optical switch having a switch input and a set of N switch outputs, and each including a dispersive element and a controllable beam steering element such that each said reconfigurable wavelength-selective optical switch is reconfigurable to selectively direct different respective wavelengths of a WDM optical signal at said switch input to different selected outputs of said set of N switch outputs, and wherein each said demultiplexer output is coupled to said switch input of a respective one of said set of reconfigurable wavelength-selective optical switches; and a set of optical space division multiplexers, one for each of said N switch outputs, each said optical space division multiplexer having a set of multiplexer inputs and a multiplexer output, to re-multiplex optical signals at said multiplexer inputs into a space-division multiplexed optical output signal at said multiplexer output, and wherein, for each of said set of optical space division multiplexers, each multiplexer input of said set of multiplexer inputs is coupled to said switch output of a different respective one of said set of reconfigurable wavelength-selective optical switches.