ABSTRACT
Photonics includes light generation, transmission, modulation, amplification, storage, and detection. It includes both classical and quantum physical concepts. Photonics expands on traditional optics to include a much broader range of frequencies extending from microwave frequencies well into the ultraviolet spectrum. Waveguides, including optical fibers, enable the spatial confinement of a beam in a well-defined volume and the transmission of light from one location to another. The fiber optic has a round cross-section, rather than square. This means that, for a large diameter cable, there can be many different transverse modes corresponding to a single wavelength. The types were perhaps introduced to prevent accidental connection between physical contact and angled physical contact connectors, but both kinds come with both key widths. The width difference is too small to see by eye and is truly an annoyance.
