The transmission of data in transmission systems with multiplex technology allows a plurality of users to use a transmission medium simultaneously, thereby significantly extending transmission capacity. With the optical wavelength division multiplexing method (abbreviated to WDM) N modulated optical signals in NRZ format (hereafter also referred to as data signals) with the mid-wavelengths (carrier wavelengths) λ1, . . . , λN are combined by a wavelength multiplexer to form a broadband optical WDM signal and transmitted in N channels. The WDM signal is therefore a summated signal consisting of the data signals of the N signals. A wavelength range or frequency range used for the transmission of a data signal is used as the channel.
The polarization multiplexing method is used to double transmission capacity in a predetermined optical transmission channel. With the polarization multiplexing method (abbreviated to POLMUX) two data signals polarized orthogonally in respect of each other are transmitted in an optical channel at a mid-wavelength. The resulting signal is referred to as a polarization multiplex or POLMUX signal. This doubles the transmission capacity of an individual transmission channel. An advantageous method for POLMUX transmission is disclosed in an earlier application with the publication number 10 2004 005718 A1.
By combining both transmission technologies it has been possible to achieve data rates of more than 10 Tbit/s over a distance of more than 300 km (Y. Frignac et al., “Transmission of 256 WDM and polarization division multiplexed channels at 42.7 Gb/s (10.2 Tb/s capacity) over 300 km of TeraLight™ fiber”, in Proc. OFC 2002, Paper FC5).