The present document defines the physical layer interface to be applied to the SB and TB reference points of the reference configurations of the Broadband Integrated Services Digital Network (B-ISDN) cell based User-Network Interface (UNI) at 155 520 kbit/s and 622 080 kbit/s. It addresses separately the Physical Media Dependant (PMD) and Transmission Convergence (TC) sublayers used at these interfaces, and addresses also the implementation of UNI
related physical layer OAM functions.
The selection of the physical medium for the interfaces at the SB and TB reference points should take into account that optical fibre is agreed as the preferred medium to be used to cable customer equipment. However, in order to allow the use of existing cabling of customer equipment, other transmission media (e.g. twisted pairs and coaxial cables) should not be precluded. Also, implementations should allow terminal interchangeability.
The present document reflects in its structure and content the desire to take care of such early configurations and introduces a degree of freedom when choosing a physical medium at the physical layer.