LCOS Calibration System for Wavelength Selective Switch Alignment
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Solution Overview
Problem
Existing wavelength selective switches face challenges in maintaining stability and thermal shielding, particularly in higher functionality devices, leading to issues with transient port isolation, calibration validity across operating conditions, and variations in switching and attenuation images due to alignment changes.
Innovation Solution
A calibration system that includes a monitor for projecting an optical monitor beam onto a spatial light modulator and detecting the reflected beam to provide a calibration signal, with an active correction unit applying corrections to optical beam trajectories while maintaining a constant switching state, using a reconfigurable spatial light modulator device and wavelength dispersive elements like a grism, and temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the LCOS device is used to readjust and steer the light to overcome alignment changes, then the alignment stability is improved, but transient changes to port isolation occur which are poorly controlled
Solution Approach 1:
The patent implements a feedback control system where a monitor beam detects the actual position of optical beams, and this information is used to generate correction signals that adjust the LCOS device to compensate for alignment drift. This closed-loop feedback mechanism maintains port isolation by continuously correcting alignment changes while preserving stability.
Solution Approach 2:
The patent introduces a monitor beam as an intermediary element that indirectly measures alignment conditions without disrupting the main optical paths. This monitor beam serves as a mediator between the physical alignment state and the control system, enabling precise control of port isolation through the spatial light modulator.
2Stability of the object's composition
If the LCOS device readjusts to overcome alignment changes, then alignment stability is improved, but calibration validity across operating conditions becomes difficult to ensure
Solution Approach 1:
The patent performs preliminary calibration using a monitor beam to establish reference positions of optical beams under various operating conditions before actual switching operations. This pre-calibration creates a baseline that validates the calibration accuracy across different temperatures and alignment states, ensuring measurement precision is maintained.
Solution Approach 2:
The patent systematically varies operating parameters such as temperature and alignment conditions during calibration, and uses the monitor beam to track how beam positions change with these parameters. This allows the system to build a comprehensive calibration model that remains valid across the full range of operating conditions.
3Adaptability or versatility
If alignment changes occur to overcome instability, then adaptability is improved, but significant variations in switching and attenuation images occur causing uncontrolled orders to emerge as port isolation issues
Solution Approach 1:
The monitor beam provides real-time feedback on the positions of switching and attenuation images, allowing the control system to detect when uncontrolled diffraction orders emerge. The feedback loop then adjusts the LCOS device to suppress these unwanted orders while maintaining the necessary alignment adaptability for different switching configurations.
Solution Approach 2:
The patent applies local quality control by selectively adjusting the phase profile of the LCOS device in specific regions to suppress unwanted diffraction orders while maintaining the overall switching functionality. This localized correction ensures that adaptability is preserved for intended operations while port isolation is maintained by eliminating spurious orders.
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 solution dynamically adjusts optical beam alignment to compensate for thermal and mechanical instabilities, ensuring accurate calibration and reduced optical flicker, thereby improving port isolation and stability across various operating conditions.
Implementation Method 1
a spatial light modulator including a plurality of cells, each cell being independently electrically drivable at one of a number of predefined states for, in conjunction with other cells, diffracting the optical beams into at least a zero diffraction order and a higher diffraction order and selectively steering the diffraction orders along predetermined trajectories
Implementation Method 2
a monitor for projecting an optical monitor beam through at least a portion of the wavelength selective switch onto the spatial light modulator and detecting the monitor beam reflected from the spatial light modulator device
Implementation Method 3
The wavelength selective switch preferably includes a wavelength dispersive element for spatially dispersing the optical beams in a dispersion dimension
Data Source
AI summary
Described herein is a calibration system (25) for a wavelength selective switch (1). The switch (1) is adapted for dynamically switching optical beams (5, 7) along respective trajectories between input and output ports disposed in an array (3) using a reconfigurable Liquid crystal on silicon (LCOS) spatial light modulator device (17). The calibration system (25) includes a monitor (27) for projecting an optical monitor beam (29) through at least a portion of the switch (1) onto the LCOS (17) and detecting the monitor beam (29) reflected from the LCOS (17). In response, system (25) provides a calibration signal (33) to an active correction unit (35) for applying a correction to one or more of the trajectories while maintaining a constant switching state in the LCOS (17).