Polarization Diverse Wavelength Selective Switch Port Isolation
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Solution Overview
Problem
Current optical switching devices, particularly wavelength selective switches (WSS) with dual source configurations, face challenges in port isolation, size, and cost due to increased port numbers and directivity issues, leading to undesired connectivity and multipath interference.
Innovation Solution
An optical switching device with a port selecting module that includes polarizing elements for polarization manipulation, such as birefringent walk-off crystals and Faraday rotators, to selectively direct optical beams along predetermined paths, reducing cross-coupling between ports and allowing reconfigurable port functionality, and a beam confining module for spatial separation and alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of ports in a switching device is increased to manage system demand, then the device can handle more optical signals, but directivity issues become more prominent and undesired connectivity between ports increases
Solution Approach 1:
The patent introduces polarization diversity as an additional dimension to distinguish between different optical paths. By separating signals based on polarization states (horizontal and vertical) and using polarization-specific routing, the device can handle increased port numbers while maintaining port isolation. The polarization beam splitters and polarization-maintaining components create distinct polarization channels that prevent cross-coupling between ports.
Solution Approach 2:
Polarization beam splitters and polarization-maintaining components act as intermediaries that selectively route optical signals based on their polarization states. These intermediary elements ensure that signals from different ports are directed along predetermined paths without interfering with each other, thereby maintaining port isolation even as the number of ports increases.
2Reliability
If isolator arrays are added to input ports to address connectivity issues, then port isolation is improved, but optical loss increases and device size and cost increase
Solution Approach 1:
The patent replaces traditional isolator arrays with a polarization-based switching mechanism. Instead of using isolators that physically block or absorb unwanted signals (causing optical loss), the invention uses polarization beam splitters and polarization-maintaining components to selectively route signals based on their polarization states. This substitution eliminates the need for isolators and reduces optical loss while maintaining port isolation.
Solution Approach 2:
The invention changes the parameter used for signal routing from spatial isolation (requiring isolators) to polarization state discrimination. By manipulating and detecting polarization parameters, the device achieves port isolation without the optical losses associated with isolator arrays. The polarization state becomes the key parameter for controlling signal paths.
3Adaptability or versatility
If beams from two sources are propagated separately in space, then independent routing is achieved, but device size increases and manufacturing cost increases
Solution Approach 1:
The patent merges the optical paths of two sources by using polarization division multiplexing. Instead of providing separate physical paths for each source, the invention combines both sources into a shared optical path, with each source's signals distinguished by their polarization states. This merging reduces device size while maintaining dual source capability through polarization-based routing.
Solution Approach 2:
The patent makes the optical components universal by designing them to handle multiple sources through a single shared path. The polarization beam splitters, polarization-maintaining components, and switching elements are configured to process signals from both sources simultaneously, allowing one set of components to serve multiple functions and reducing the overall device size.
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 solution enhances port isolation, reduces device size and cost, and minimizes interference effects by efficiently coupling optical beams between input and output ports while restricting back-coupling, thereby improving overall device performance.
Implementation Method 1
a polarization separation element for spatially separating an optical beam into two orthogonal polarization components; The polarization separation element preferably includes a birefringent walk-off crystal element
Implementation Method 2
a polarization rotation element for selectively rotating the polarization components with respect to each other. The polarization rotation element preferably includes a Faraday rotator configured to apply a 45° rotation to a polarization component
Data Source
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AI summary
Described herein is a wavelength selective switch (WSS) type optical switching device (1) configured for switching input optical beams from input optical fiber ports (3, 5 and 7) to an output optical fiber port (9). Device (1) includes a wavelength dispersive grism element (13) for spatially dispersing the individual wavelength channels from an input optical beam in the direction of a second axis (y-axis). The optical beams propagate from input ports (3, 5 and 7) in a forward direction and are reflected from a liquid crystal on silicon (LCOS) device (11) in a return direction to output port (9). The input optical beams are transmitted through a port selecting module (21), which provides polarization diversity to device (1) and provides capability to restrict optical beams returning from LCOS device (11) from being coupled back into input ports (3, 5 and 7).