Optical fibers, as well as transmitters and receivers for optical communications, are described. With regard to transmitting components, a distinction is made between three types (I, II, III) of semiconductor lasers. In type I (very low Mesa structure), the strip width is approx. 20 mu m, and in type II (proton bombarded laser), it is between 3 mu m and 7 mu m. Due to the narrow strip width of type II, its features are improved with respect to laser type I. Laser type III is a double heterostructure diode of InGaAsP on InP substrate with an emission wavelength of 1300 nm. For the use of laser diodes in optical waveguides, a transmitter unit was developed.