MEMS Mirror Dither Amplitude Adjustment for Optical Switch Coupling
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Solution Overview
Problem
Existing optical systems employing MEMS mirror arrays for coupling light between input and output fibers face challenges in parameter variations among mirrors, requiring a method to set dither amplitude based on individual MEMS characteristics for optimal coupling.
Innovation Solution
The method involves adjusting the dither amplitude of MEMS mirrors in optical switches using digital-to-analog (DAC) settings stored in memory, determining the dither amplitude by fitting signal values to a polynomial corresponding to the position of output ports and calculating the slope to achieve nominal peak coupling, allowing for individual tuning of each mirror.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed dither amplitude is used for all MEMS mirrors, then the control system is simple, but parameter variations from mirror to mirror result in suboptimal coupling efficiency
Solution Approach 1:
The patent implements individual dither amplitude tuning for each MEMS mirror based on its specific coupling characteristics. The system measures the coupling efficiency for each mirror and assigns a customized dither amplitude, making the control parameters local to each mirror rather than uniform across the array. This resolves the contradiction by accepting increased control complexity to achieve optimal coupling efficiency for each individual mirror.
Solution Approach 2:
The system dynamically adjusts the dither amplitude parameter for each MEMS mirror based on measured coupling characteristics. By changing the dither amplitude parameter individually for each mirror, the system optimizes coupling efficiency despite manufacturing variations. This approach transforms a fixed parameter system into a variable parameter system that adapts to each mirror's specific properties.
2Reliability
If dither amplitude is increased to ensure sufficient dither signal for servo control, then servo control performance improves, but unwanted disturbance to the optical path increases
Solution Approach 1:
The patent determines individual dither amplitudes for each MEMS mirror based on its specific coupling characteristics and position. Mirrors with better coupling efficiency receive smaller dither amplitudes, while those with poorer coupling receive larger amplitudes. This local optimization ensures sufficient servo control performance for each mirror without unnecessarily increasing optical disturbance across the entire system.
Solution Approach 2:
The system applies dither amplitudes that are sufficient but not excessive for each individual mirror's needs. By measuring coupling efficiency first, the system determines the minimum necessary dither amplitude for reliable servo control, avoiding the harm of excessive dither while ensuring adequate control performance. This partial action approach optimizes the balance between control reliability and optical disturbance.
Data Source
AI summary
Methods for adjusting dither amplitude for MEMS mirrors in optical switches and optical switches employing such a method are disclosed. A dither amplitude of one or more MEMS mirrors may be adjusted in an optical switch having an input port, and an array of one or more MEMS mirrors that can be selectively optically coupled to one or more of N≧3 optical input/output (I/O) ports. The MEMS mirrors are aligned mirrors to achieve nominal peak coupling at each of the N collimators. Digital-to-analog (DAC) settings for positioning mirrors in an open control loop as a function of the selected collimator are stored to a non-volatile memory. The DAC settings are used to determine a dither amplitude DITHER(x) for one of the MEMS mirrors positioned to couple optical signals to an output port at a position x. The optical switch apparatus may comprise N≧3 optical input/output (I/O) ports, an array of one or more MEMS mirrors that can selectively reflect one or more spectral channels to one or more of the N ports, and a servo-control assembly in communication with said one or more of the MEMS mirrors. The servo control assembly includes memory containing digital-to-analog converter (DAC) settings for positioning each mirror in an open control loop as a function of a port position x. The servo control assembly is programmed to adjust dither amplitude of one or more of the MEMS mirrors using the stored DAC settings.