Investigation of Allowed Channel Spacing for Differently Modulated Optical Signals in Combined HDWDM Systems

摘要

In recent years the dramatic increase of demand for transmission capacity is observed and to secure an appropriate quality of service (QoS) level telecommunications services providers must constantly and continuously develop their transmission systems in use [1-4]. Currently, as a study object of many works have been chosen and focused directly on the fibre total transmission capacity increases, and this can happen in a three different ways. The first one, the existing 10 Gbit/s DWDM system upgrade, but in fact it is the substitution of existing system with 40 Gbit/s DWDM system or faster, because the only 10 Gbit/s system components, which can be used in new 40 Gbit/s system, are fibre, boosters and some external modulated lasers, but all transmitter and receiver electrical parts with bandpass filters must be changed to a new one. The second one, channels compaction by location them closer to each other using smaller channel spacing between them, in that way increasing the number of channel in available transmission frequency spectrum [2]. In this case, the total transmission capacity increment is achieved only because of increasing the number of channels, as the individual transmission rate in each channel remains unchanged. And the third way, total transmission capacity increment, using channel compaction with simultaneous increment of individual channel's transmission bit rate.