Some trends in optical communications

Some materials such as chalcogenide glasses have large refractive indices and are suitable in fabrication of optical fibers and planar waveguides for wavelength conversion, using cross-phase modulation and signal regeneration, based on self-phase modulation.The supercontinuum as a result of the nonlinear interaction of ultrafast pulses of one color with a transparent material division is a series of white-light pulses, applicable in dense wavelength division multiplexing (DWDM). Owing to nonlinear effects in optical fiber two DFB lasers can be used to produce a beat signal with predefined channel frequencies and spacings. Cooling the atoms to the lowest quantum state they become coherent and demonstrate effects familiar to optical effects (atomtronics). Free-space optics demonstrates its come-back for local-access bridges to fiber backbones and specific applications.