The transmission of a data signal (DS) in the form of data packets takes place by means of angular modulation, preferably two or three stage difference phase modulation. The header (HEAD) is transmitted by means of polarization modulation. An additional channel formed in this way is also available for the transmission of additional information. To separate the header (HEAD), the multiplex signal (DHS) is aligned in a specific polarization level, so that the header can be separated without any problem. A new header can be added without having to convert the data signal into an electrical signal beforehand.