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23 August 2005 Phase-locking of tiled fiber array using SPGD feedback controller
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We present the laboratory experiments of phase locking of a multi-channel tiled fiber array using a stochastic parallel gradient descent (SPGD) feedback controller demonstrating the compensation effect of the simulating phase-induced distortions based on the model-free optimization of the received signal strength. An all-polarization-maintaining (PM)-fiber optical configuration is used to simplify the free-space transceiver system. The atmospheric aberrations are simulated by a multi-channel integrated optical phase modulator which obtains input control voltages from an array of multi-channel independent sinusoidal signal generators. A similar multi-channel phase modulator which obtains input control voltages from a computer-based SPGD controller is used to compensate the simulating phase distortions. The experimental results show that the constructive interference state is reached through phase locking of the multi-channel tiled fiber array for phase distortions up to 180 hertz for each channel. The update rate of the computer-based SPGD controller is ~16,000 iterations per second. The average compensation bandwidth is about 310 Hz
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Ling Liu and Mikhail A. Vorontsov "Phase-locking of tiled fiber array using SPGD feedback controller", Proc. SPIE 5895, Target-in-the-Loop: Atmospheric Tracking, Imaging, and Compensation II, 58950P (23 August 2005);

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