Adaptive optics Classical communication Degrees of freedom (mechanics) Digital signal processing Eigenvalue and eigenfunctions Eigenvalues and eigenfunctions Entangled photons Entanglement distribution Equalizers Estimation Estimation methods MIMO systems Mean square error Mode-dependent gain Mode-dependent loss Multi-cores Network-based Neural networks No-cloning theorem Optical coupling Optical couplings Optical fiber communication Optical fibers Optical polarization Optical receivers Optical signal to noise ratio Optical-fiber communication Photon pairs Photons Quantum channel