2002 - cesnet

During the second half of the year, we tested the Cisco and Pandatel DWDMsystems on the Brno–Olomouc line. The optical fibres on this line are approximately115 km long. At this distance, the impact of chromatic dispersionof the optical fibres does not fully develop, particularly thanks to the appliedtransmission technologies. However, this distance is already beyond reach ofstandard SWDM devices and an optical amplifier must be used.At first, we tested the Cisco 15540 system, with Cisco 15501 optical amplifiers, aswell as with Keopsys optical amplifiers. There were four neighbouring channelsavailable with transponders configurable from Fast Ethernet, through SDH STM-1, STM-4 to STM-16 and Gigabit Ethernet.Cisco ONS 15540EDFAboosterfiber 130 kmEDFAboosterFigure 4.13: Testing configuration – Cisco 15540Cisco ONS 15540We made use of one STM-16 channel for common traffic, one Gigabit Ethernetchannel, which we tested using Schomiti analyzer, and two STM-1 channels forthe testing of bit error rate, using HP 37717 analyzer. The configuration of thisdevice is very user-friendly as it includes the standard Cisco IOS.In the same way, we carried out the testing of the Cisco 15200 system, which issmaller device (available for a reasonable price). We had one Cisco 15252 modularmultiplex at our disposal, together with three single-channel Cisco 15201multiplexes. This solution proved to be fully functional as well. It is convenient,particularly, for channel branching within the course of a line. An advantageof this device is that in the case of any power supply failure, transit channelsremain fully operational. The system configuration is not as user-friendly as inCisco 15540.During the testing of a Pandatel Fomux 3000 DWDM system we used the Keopsysamplifiers, as the manufacturer offers no optical amplifiers. In this case, itwas possible to make a successful use of amplifiers intended for the amplificationof a single channel. However, there were some problems concerning theoutput power regulation of individual cards (SDH and Gigabit Ethernet), whichis why the deployment of this system in the network does not appear to be aperspective option.Another objective was to find out whether it is possible to make use of Keopsysoptical amplifiers intended for single-channel transmissions, together with theDWDM system, with a relatively low number of channels (4 to 8). The resultsconfirmed our expectations and the line was running without any complications,using both types of amplifiers. We may therefore say that the tested sys-60 High-speed National Research Network and its New Applications 2002