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Chapter 2Overview of current CATV network p2.7.1 FTTx technologiesFTTx is a series of networking technologies that connect the users and the central officevia optical fibre links. Although the cost of optical fibre is not much different fromcoaxial cable, optical equipment is very expensive. There are two main forms of FTTxtechnology:• FTTC: Fibre-to-the-Curb (FTTC) is also referred as Switched Digital Video (SDV).This technology makes use of fibre optic to connect the headend to Optical NetworkUnits (ONU) ‘at the curb’ and serves small groups of homes (between 8 and 24homes) [67]. Twisted pair and coax cable is used to connect the ONU to individualhomes. Twisted pair supports POTS while coax supports analogue video and newdigital services can be supported by either.While TDM is used at present to multiplex signals for delivery to individual homes,ATM switches will most likely replace the ONU in the near future [67]. Telephony,video and digital services are multiplexed for transport over the FTTC network andare de-multiplexed by the ONUs. The maximum downstream bandwidth supportedby FTTC networks is 51 Mbps using coax cable. Twisted pair can also be used tosupport the same bandwidth if the length is not greater than 500 feet.• FTTH: Fibre-to-the-Home (FTTH). This technology is a point-to-point networkarchitecture that uses only fibre links. The cost of deployment of a FTTH network isconsidered high compared to FTTC and HFC. Many people believe that FTTCtechnology is more cost-effective than FTTH due to maintenance and the largenumber of ONUs. However the opposite is true, [76]. Although FTTH networksavoid the use of ONUs, the high number of laser transceivers used and the cost of thefibre links, which run down to the last mile into each home, makes them a costlysolution. However, the increased bandwidth available to each fibre out of theHeadend might be as high as 155 Mbps (OC-3c), allowing each home to become aservice provider by attaching servers within the subscriber’s premises [67]. FTTH isthe topology that offers the highest capacity due to its all-fibre structure and is anattractive solution for Telco’s. Some Telco’s have already installed FTTH networks,such as Nippon Telegraph and Telephone, (NTT) [122] and Deutsche Telecom [123].2-15