2002 - cesnet

particularly based on the fact that optical amplifiers were necessary for the deploymentof some lines exceeding 80 km (particularly the Gigabit Ethernet).In January and early February, negotiations were held with Keopsys concerningthe testing of their EDFA amplifiers in the CESNET2 network. Our aim wasto test the possible operation without any in-line device (also referred to as“nothing-in-line” or “repeaterless line”). This mode makes the maintenance ofthe operated line much easier, and it also represents an interesting and technicallynovel method. In parallel, we carried out research in the area of 10GE andits possible deployment. In the second half of February, we managed to arrangetesting days of EDFA technology with Keopsys.The brief technical outcome of the testing is given below:• EDFA amplifier can be deployed as a booster within CESNET’s opticallines, for distances up to 188 km, without any notable increase in the biterror rate. The attenuation limit of a fibre span using an 18 dBm booster is46 dB.• The line with the length given above may be used – in configuration with abooster – both with the POS 2.5 Gbps technology and with the Gigabit Ethernetbased on the long reach modules. All technologies must make use ofthe wavelength of 1,550 nm.• In combination with an EDFA booster, it is also possible to make use ofpre-amplifier. In this combination, it is possible to compensate attenuationof the line up to 60 dB, corresponding to approximately 230 km of an opticalfibre. However, it is always necessary in this configuration to insert anoptical ASE filter behind the preamplifier in order to cut off an excessivequantum noise spectra which is originated in a physical function of EDFAand as such is any time present.• The experiments also included testing a Raman amplifier, which makes itpossible to cover an additional attenuation of 15 dB, thus enabling the spanof a total distance up to 290 km in combination with other amplifiers (EDFAbooster on the input, EDFA preamplifier on the output).The testing proved the functionality of the EDFA technology. Immediately afterwards,we ordered three EDFA boosters with a saturation output power of21 dBm – two for the routine operation of the Prague–Pardubice line and onefor the laboratory, serving for the purpose of further experiments and as abackup.In collaboration with the network operation centre, we installed both amplifiersin the line mentioned above. The installation was without any complicationsand the saturated output power was adjusted at 19 dBm. According to thenetwork monitoring, the function appears to be free of problems, without anyincrease in the bit error rate of the transmitted Gigabit Ethernet frames.High-speed National Research Network and its New Applications 200257