Wavelength Selective Switch Crosstalk Reduction via LCOS Diffraction
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Solution Overview
Problem
Existing optical communication systems face issues with crosstalk increase due to power balancing in optical signals, leading to reduced port isolation and increased nonlinear transmission costs.
Innovation Solution
A method and apparatus for transmitting optical signals using a wavelength selective switch that involves diffraction processing to deflect crosstalk light outside all output ports, thereby reducing crosstalk values and achieving power balancing by controlling the diffraction directions of signal and crosstalk light using liquid crystal on silicon (LCOS) and grating diffraction equations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the diffraction direction of optical signal is controlled to attenuate signal power, then the signal power can be adjusted to fall within specified range, but high-order diffractive light (crosstalk light) is also deflected and coupled to other output ports, causing crosstalk energy increase and port isolation decrease
Solution Approach 1:
The patent segments the diffraction control into two independent dimensions: the first direction (horizontal) controls signal light diffraction for power adjustment, while the second direction (vertical) controls crosstalk light diffraction for isolation. This segmentation allows independent optimization of signal power and crosstalk suppression without mutual interference.
Solution Approach 2:
The patent introduces a second diffraction direction perpendicular to the first direction. The LCOS device applies different phase modulation patterns in these two dimensions: in the first direction, it diffracts signal light to achieve power attenuation; in the second direction, it diffracts crosstalk light to prevent coupling to other ports. This dimensional separation resolves the contradiction between power control and crosstalk suppression.
2Measurement precision
If liquid crystal on silicon is used to control diffraction direction for power adjustment, then signal power can be precisely controlled, but crosstalk light is simultaneously deflected toward other output ports, reducing port isolation
Solution Approach 1:
The patent segments the LCOS phase modulation into two independent directional controls. The first directional phase modulation achieves precise signal power control through controlled diffraction, while the second directional phase modulation independently suppresses crosstalk by deflecting it away from other ports. This segmentation maintains both precision and reliability simultaneously.
Solution Approach 2:
The patent utilizes the two-dimensional addressable structure of LCOS to apply independent phase modulation in two perpendicular directions. The first direction provides precise power control, while the second direction ensures port isolation by redirecting crosstalk. This dimensional approach allows both precision and reliability to be optimized independently.
3Reliability
If optical signal power is increased to improve signal-to-noise ratio, then receive end signal quality improves, but nonlinear transmission costs increase and power balancing becomes difficult
Solution Approach 1:
The patent extracts the power control function from the signal transmission path by using diffraction-based attenuation in the WSS device. This allows precise power reduction to achieve optimal signal-to-noise ratio while avoiding excessive power levels that would cause nonlinear effects, effectively separating power management from the main transmission path.
Solution Approach 2:
The patent changes the power parameter of optical signals through controlled diffraction attenuation. By adjusting the diffraction angle and efficiency in the first direction, the system can precisely control output power levels to maintain optimal signal-to-noise ratio while preventing nonlinear transmission effects, achieving parameter optimization without harmful side effects.
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 effectively reduces crosstalk values during power balancing, enhancing port isolation and maintaining signal power within specified ranges, thus improving the efficiency of optical communication systems.
Implementation Method 1
performing diffraction processing on an input optical signal obtained from an input port, to obtain signal light and crosstalk light
Implementation Method 2
controlling the diffraction directions of signal and crosstalk light using liquid crystal on silicon (LCOS) and grating diffraction equations
Implementation Method 3
deflecting, in a second direction, a diffraction direction of a part of the crosstalk light or a diffraction direction of all of the crosstalk light, so that the part of the crosstalk light or all of the crosstalk light is output to an area outside all the output ports
Data Source
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AI summary
Embodiments of the present invention provide a method and an apparatus for transmitting an optical signal and a wavelength selective switch. The transmission method includes: performing diffraction processing on an input optical signal, to obtain signal light and crosstalk light. The signal light is output to a target output port in a plurality of output ports. The diffraction processing includes deflecting, in a second direction, a diffraction direction of a part or all of the crosstalk light, so that the part or all of the crosstalk light is output an area outside the output ports.