Ultrahigh-splitting-ratio optical subscriber system for small-capacity services

Abstract

Although optical subscriber loops that provide multimedia services have been developed, attention is now being placed on the provision of systems that especially support small-capacity services, such as plain old telephone services (POTS) and ISDN basic-rate access. The key point is that the systems must be as economical as metallic systems. For this purpose, (a) the optical subscriber unit (OSU) in a central office must be shared by as many optical network units (ONUs) as possible through the use of splitting devices, as shown in Fig. 1, and (b) ONU cost must be reduced. The first point involves increasing the splitting ratio. The second point can be realized by using passive ONUs without light sources, such as reflective/transparent modulators1 (see inset of Fig. 1).