The present invention relates to a multiplex conversion unit for multiplexing and demultiplexing digital signals between a plurality of low-speed transmission paths and a plurality of high-speed transmission paths in a digital communication network.
The technique described in "Design of Digital Network Transmission Facilities" by Teranishi and Kitamura, The Denki Tsusin Kyokai, Aug. 10, 1984, is known as a conventional multiplex conversion unit for multiplexing and demultiplexing digital signals between a plurality of low-speed transmission paths and a plurality of high-speed transmission paths in a digital communication network.
FIG. 10 shows a configuration of a typical multiplex conversion unit.
As shown in FIG. 10, a multiplex conversion unit 40 comprises a plurality of low-speed interface sections 43 for interfacing with a plurality of low speed transmission paths 41, a high-speed interface section 45 for interfacing with a high-speed transmission path 42, and an add/drop multiplex (ADM) section 44 for multiplexing and demultiplexing between low-speed signals input/output by the low-speed interface sections 43 and the high-speed signals input/output by the high-speed interface section 45.
In recent years, various types of networks have been suggested including the point-to-point (or terminal MUX, hereinafter referred to as "TM"), add/drop chain (or linear ADM, hereinafter referred to as "LADM") and the "ring" using a plurality of multiplex conversion units.
In the case where a multiplex conversion unit of the same configuration is used for all types of networks, however, component parts (such as a switch) having functions not necessary for a given type of network may be incorporated in a multiplex conversion unit for an increased cost of the multiplex conversion unit.