LCOS Wavelength-Selective Switch With Curved Ports for Crosstalk Control
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Solution Overview
Problem
Existing wavelength selective switches (WSS) based on Liquid Crystal on Silicon (LCoS) technology face challenges in achieving high isolation between output ports while maintaining a large number of ports due to crosstalk from high diffraction orders, which are difficult to eliminate, affecting system performance.
Innovation Solution
The LCoS-based wavelength selective switch employs a non-linear port arrangement, where output ports are arranged along a curve or combination line such that diffraction orders are symmetric with respect to the input port, ensuring only the primary order enters the designated port, and other crosstalk orders are prevented from entering adjacent ports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If LCoS is used as the switching engine to achieve wavelength selective switching, then the device supports Flex-grid feature and becomes mainstream, but high diffraction orders generate crosstalk that affects system performance
Solution Approach 1:
The patent transitions from a one-dimensional linear array of output ports to a two-dimensional curved array arrangement. By curving the fiber array along an arc with radius R, the patent creates additional spatial dimensions to separate the optical paths of different diffraction orders, allowing high-order diffracted light to be directed away from the output ports while maintaining wavelength selective switching functionality.
Solution Approach 2:
The patent introduces asymmetric positioning of the LCoS panel relative to the curved fiber array. The LCoS panel is positioned at a specific distance and angle from the array center, creating an asymmetric optical path that causes high-order diffraction light to diverge from the output port locations. This asymmetric arrangement breaks the symmetry that would otherwise cause crosstalk between adjacent ports.
2Quantity of substance
If more output ports are added to increase switching capacity, then the device can handle more wavelengths, but isolation between ports deteriorates due to crosstalk
Solution Approach 1:
By arranging output ports along a curve rather than a straight line, the patent utilizes the radial dimension of the curved array to increase port density while maintaining angular separation. This curved geometry allows more ports to be packed into a compact area while the radial distance provides natural isolation, as high-order diffraction angles map to different radial positions on the curved array.
Solution Approach 2:
The patent applies different spatial characteristics to different regions of the fiber array. Ports located at different angular positions on the curved array experience different optical path geometries, with each port having optimized isolation characteristics for its specific location. This local optimization allows high port density while maintaining uniform isolation performance across all ports.
3Device complexity
If linear array arrangement is used for output ports, then the structure is simple, but crosstalk from high diffraction orders cannot be effectively suppressed
Solution Approach 1:
The patent replaces the linear (straight-line) arrangement with a curved (arc-shaped) arrangement of the fiber array. This curvature is specifically designed with radius R such that the optical path length from the LCoS panel to different ports on the curve creates angular separation between different diffraction orders. The curved geometry naturally directs high-order diffracted light away from the output ports while maintaining a relatively simple single-layer structure.
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 arrangement achieves extremely high isolation between output ports and allows for a larger number of ports without increasing insertion loss, meeting the stringent crosstalk performance requirements of modern optical communication systems.
Implementation Method 1
An operating principle of the LCoS lies in that, different voltages are loaded on different pixels (pixel) of the LCoS. Due to a birefrigent effect of a liquid crystal, the different voltages are corresponding to different phase delays. In this way, a structure similar to a blazed grating (Blazed grating) may be formed. Because a diffraction angle of the blazed grating depends on a grating period of the blazed grating, only grating periods corresponding to different locations on the LCoS need to be changed, to control a diffraction angle of incident light
Implementation Method 2
Different voltages are loaded on different pixels (pixel) of the LCoS. Due to a birefrigent effect of a liquid crystal, the different voltages are corresponding to different phase delays
Implementation Method 3
US 2017/0299858 A1 describes a WSS, which includes an LCOS panel and a fiber array with multiple ports. The fiber array includes an input port and multiple output ports. The input port and the multiple output ports are located in a straight line. The LCOS panel may be rotated, and the blazed-grating-like structure on the LCOS panel may be a tilt structure, so that +1-order diffractive light is output from a corresponding port, and other orders of diffractive light bypass ports of the fiber array
Data Source
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AI summary
Embodiments of the present invention disclose a WSS. An output port arrangement solution of an optical fiber array of the WSS is as follows: Centers of output ports are arranged along a curve or along a combination line that includes a line segment, and a straight line connecting centers of any two output ports on the curve or the combination line does not pass through an input port. A light beam received from the input port is diffracted to the output ports through an LCoS panel, and a straight line that all diffraction orders that are generated after the diffraction pass through intersects with the curve or the line segment, and there is only one intersection point. The WSS provided in the embodiments of the present invention can effectively increase a quantity of output ports and improve performance of isolation, and has high practicability.