From ISDN to ATM: fibre in the loop, an evolving scenario

Compatibility between several different optical transmission techniques is revealed, provided that the frame structure and system equipment are specified according to various organizational constraints. Standardization can proceed without reference to the time compression multiplex (TCM). Similarly, by judiciously organizing exchange equipment (OLT) and user equipment (ONU) functions, network interfaces and optical transmission can evolve separately and broadband services can be accommodated progressively. The multispeed frame principle remains the cornerstone of the system given its suitability for matching equipment to applications and to different categories of user. It is also a good basis for future standardization in that it affords a high degree of openness in the definition of specifications. Economic parity of the optical systems in fiber-to-the-home (FTTH) distribution is contingent on the development of new and integrated optical components.