The upgrade of installed optical lines with large unequal amplifier spans

The important line characteristic that determines cost of the link is the amplifier spacing. Long spans between amplifiers are desirable from the commercial view point even if from the technical view point a realisation of such lines can be not the optimal solution. Maximum distance between amplifiers, which has been studied recently is 120 km. In this paper we examine upgrade of an existing line Novosibirsk-Omsk with several unequal long haul spans of SMF fibres. Total length of this line is 563 km.