Fig. 3: Experimental implementation of the orbital angular momentum (OAM)-coded signal generation and Fourier optics convolution. | Communications Physics

Fig. 3: Experimental implementation of the orbital angular momentum (OAM)-coded signal generation and Fourier optics convolution.

From: Multiplexed orbital angular momentum beams demultiplexing using hybrid optical-electronic convolutional neural network

Fig. 3

a Laboratory experiment setup. A laser source with a 1500 nm wavelength is coupled, expanded, and projected onto the first spatial light modulator (SLM) loaded with computer-generated combined fork phase grating patterns, generating OAM-coded beams with desired topological charges. After being reflected by the second SLM, which is loaded with the atmospheric turbulence phase masks, the turbulence-affected OAM-coded beams complete the Fourier optics convolution via pixel-wise multiplications with pre-trained kernels loaded on the digital micromirror device (DMD), which is placed at the focal plane. The spatially-frequency-filtered components are inverse Fourier transformed after passing through the second lens and captured by the camera as electronic output to the electronic max-pooling layer and two fully connected layers. FL Fourier lens. A scale bar of length 25.4 mm is drawn. b Experimental setup scheme. FC fiber coupler, BE beam expander, BS beam splitter, P pinhole, L lens.

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