Wavelength Selective Switch Port Isolation via Polarization
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Solution Overview
Problem
Wavelength selective switches in optical communication networks experience undesirable optical coupling between input and output ports, leading to issues of diversity and isolation.
Innovation Solution
An optical arrangement comprising a port array, dispersion element, focusing element, and programmable phase modulator, which uses a walkoff crystal, composite half-wave plates, polarizer, and Faraday rotator to spatially separate and direct optical beams based on polarization states, preventing coupling between ports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a wavelength selective switch is used to enable reconfigurable wavelength-dependent switching, then service deployment speed and network rerouting capability are improved, but optical coupling between input and output ports increases causing undesirable diversity and isolation issues
Solution Approach 1:
A polarization-maintaining optical isolator is introduced as an intermediary component between the input and output ports of the wavelength selective switch. The isolator contains a Faraday rotator that rotates the polarization state of light by 45 degrees in each direction, creating non-reciprocal optical paths that prevent unwanted optical coupling between ports while allowing the wavelength selective switching function to operate effectively
Solution Approach 2:
The polarization state of optical signals is changed as they pass through the isolator. The Faraday rotator modifies the polarization parameter of the light, rotating it by 45 degrees in the forward direction and preventing the reverse propagation, thereby changing the optical parameters to achieve port isolation while maintaining switching functionality
2Reliability
If optical coupling between ports is reduced to improve isolation, then port diversity and isolation are improved, but device complexity increases due to additional optical components
Solution Approach 1:
The polarization-maintaining optical isolator serves multiple functions simultaneously: it provides port isolation to prevent optical coupling, maintains polarization states for efficient wavelength selective switching, and protects the input ports from back-reflections. This multi-functionality achieves high port isolation without proportionally increasing device complexity
Solution Approach 2:
The optical isolator acts as a compact intermediary device that integrates the Faraday rotator and polarization-maintaining optics into a single component. This intermediary structure provides the necessary isolation function while minimizing the increase in overall device complexity through integrated design
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 achieves directional coupling and high isolation between ports, reducing optical loss and enhancing the reconfigurability of wavelength selective switches, thereby improving network performance and reducing capital and operating expenses.
Implementation Method 1
at least one walkoff crystal for spatially separating the optical beams received from any of the ports in optical port array into first and second optical components being arranged in first and second polarization states, respectively
Implementation Method 2
The Faraday rotator and the second composite half-wave plate rotate the spatially separated optical beams received from the optical input port via the polarizer into the first polarization state and rotate the spatially separated optical beams received from the plurality of optical output ports into the second orthogonal polarization state
Implementation Method 3
a polarizer for transmitting optical energy in the second polarization state but not the first polarization state
Implementation Method 4
The dispersion element receives the optical beam from the at least one optical input after traversing the optical arrangement and spatially separates the optical beam into a plurality of wavelength components
Implementation Method 5
The focusing element focuses the plurality of wavelength components
Data Source
AI summary
An optical device includes an optical port array, an optical arrangement, a dispersion element, a focusing element and a programmable optical phase modulator. The optical port array has at least one optical input port for receiving an optical beam and a plurality of optical output ports. The optical arrangement allows optical coupling between the input port and each of the output ports and prevents optical coupling between any one of the plurality of optical output ports and any other of the plurality of optical output ports. The dispersion element receives the optical beam from the input port after traversing the optical arrangement and spatially separates the optical beam into a plurality of wavelength components. The focusing element focuses the plurality of wavelength components. The programmable optical phase modulator receives the focused plurality of wavelength components and steers them to a selected one of the optical outputs.