Transmission systems are systems in which messages are transmitted between a sending station, the message source, and the receiving station, the message sink.
The functional units of a transmission system also include the source coding, in which the information is reduced and converted into a bit sequence, the line coding, which ensures that the signals are adapted to the properties of the transmission media, the channel coding, with which redundancies are added to the bit stream in the form of check bits, and the modulator, which conditions the digital signal so that it can be transmitted via the transmission channel.
After passing through the transmission path, the message must be reprocessed on the receiving side and transferred to the message sink as unaltered as possible. The receiving side processing includes amplification, decoding and demodulation.
Optical transmission systems
An optical transmission system is generally comparable to a transmission system based on metallic conductors. The signal from the signal source must be adapted to the optical fiber transmission medium. After it has been amplified in the transmitter, it is converted into digital signals in an A/D converter and converted into optical pulses in pulse code mod ulation or pulse duration modulation in the E/O converter. These are coupled into the optical fiber and guided in it through the optical components such as optical switches, optical crossconnects( OXC), optical amplifiers( OA), etc., to the optical receiver.
An O/E converter consisting of phototransistors, PIN diodes or APD diodes generates electrical signals from the light pulses, which it feeds to the receiver. An optical transmission system can further include components for optical signal branching, signal generation and amplification.