Photonic Network Communications, 1, 65±76 (1999) # 1999 Kluwer Academic Publishers, Boston. Manufactured in The Netherlands. Analysis of Transmission of Sub-Carrier Multiplexed Signals through the Optical Transport Network E. Bravi, F. Casella, E. Iannone Fondazione Ugo Bordoni, Rome, Italy. Ms. Casella is now with WIND. Mr. Iannone is now with Pirelli Cavi e Sistemi, Milano, Italy R. Sabella Ericsson Telecomunicazioni, R&D Division, Rome, Italy Received March 10, 1998; Revised November 13, 1998 Abstract. The transmission of analog SCM signals through the optical layer of the transport network is analyzed and discussed, in order to assess the possibility of exploiting the core network for the transport of video channels, without the need of dedicated communication systems. The utilized analytical model, allowing the transmission performance to be evaluated, is reported. Some performance evaluation results are reported, taking into consideration two relevant network typologies: metropolitan networks and regional networks. The results allow the feasibility of the considered approach to be assessed, considering the available technology. Keywords: optical transport networks, optical access network, transport of SCM signals through optical transport network, external modulation, transport of CATV television 1 Introduction In the last few years the demand for interactive multimedia services and CATV is experiencing a rapid growth and this trend is expected to characterize the next decade: this boosts the need for more capacity and throughput both in the transport and in the access networks. In the transport area, the network must be able to convey high capacity channels over distances from some hundreds up to few thousands kilometers. In the access area wide user bandwidth and effective interactivity between the user and the central of®ce are required. Building large scale-very high capacity networks that are robust against failure and traf®c surges and that will evolve smoothly with time, in pace with user demand, implies a number of dif®cult problems ranging from the need of high speed electronic processing to effective network control and manage- ment. At the state of the art, a large consensus exists on considering optical networking based on Wavelength Division Multiplexing (WDM) the frame- work in which these problems can be solved [1,2]. The research programs carried out by several con- sortia, as the ARPA-funded consortia in the USA [3,4] and the RACE program in Europe [5,6], represent important steps in this direction. Besides the ¯exibility, one of the main advantages provided by multiwavelength optical networks is the transparency. Actually, different degrees of transpar- ency can be de®ned. The simplest case is the transparency to digital signals (independence of bit rate, format and protocol). Then, it is possible to de®ne a transparency to intensity modulated signals (both analog and digital signals can be transmitted through the network). Finally, fully transparency would require that the network is transparent to any optical signal: analog or digital, adopting intensity or angular modulation. Depending on the required transparency degree, different issues arises, regarding, for example, the types of optical devices that can be used in the network. If the access network is considered, one of the most promising solutions is constituted by SCM ®ber networks, providing a powerful and economic solution to assure a large bandwidth to the end user [7]. Both analog and digital signals can be