Determining the optimal communication channels of arbitrary optical systems using integrated photonic processors

Modes of propagation through an optical system are generally defined as the eigensolutions of the wave equation in the system. When propagation occurs through complicated or highly scattering media, however, modes are better identified as the best orthogonal communication channels to send information between sets of input and output apertures. Here we determine the optimal bidirectional orthogonal communication channels through arbitrary and scattering optical systems using photonic processors. The processors consist of meshes of electrically tuneable Mach-Zehnder interferometers in silicon photonics. The meshes can configure themselves based on simple power maximization or minimization algorithms, without external calculations or calibration or any prior knowledge of the optical system. The identification of the communication mode channels corresponds to a singular value decomposition of the entire optical system, autonomously performed by the photonic processors. We observe crosstalk below -30 dB between the optimized channels even in the presence of distorting masks or partial obstructions. In these cases, although the beams bear little resemblance to conventional mode families, they still show orthogonality. These findings offer potential for applications in multimode optical communication systems, promising efficient channel identification, adaptability to dynamic media and robustness against environmental challenges. Self-configuring meshes of integrated Mach-Zehnder interferometers determine the optimal communication channels through unknown optical media, with the resulting modes showing crosstalk below -30 dB.