Bandwidth increases

Written on 3:20 PM by ooe

The most obvious change that can be made to a PON system is to increase its overall bandwidth. This would allow more bandwidth per customer on average which should mean that the cost per unit of bandwidth will decrease.

The early APON standards specified 155 Mbit/s to a maximum of 32 users. This results in a bandwidth per customer in the order of 5 Mbit/s. Whilst this can be considered a great improvement on current systems, and is symmetrical in nature, in practice this bandwidth is not a great deal and would not be capable of adequately supporting the ‘Triple Play’ of voice, data and video services. Furthermore, VDSL can be configured to give bandwidths in this range and therefore the base specification APON is probably not of tremendous interest.

More recently the APON standard has been extended to allow for 622 Mbit/s downstream and 155 Mbit/s upstream asymmetric bit rates as well as a 622 Mbit/s symmetrical option. These are seen as being of greater value, since with the same 32 way split specification these can deliver in the order of 20 Mbit/s to the user. This is closer to the sorts of bandwidth required for a wider mix of services.

Currently FSAN is considering a 1.25 Gbit/s and even a 2.5 Gbit/s PON option, using new architectures not based on their baseline which was G.983.1. These new PONs may have a use in the telecommunications arena probably only as a feeder/backhaul network for VDSL or other access network systems. The IEEE is also becoming active in this area and will soon specify a 1.25 Gbit/s PON, although details are sketchy at the time of writing this chapter.

Point-to-point Ethernet systems are also becoming more prevalent although the lack of standardisation is hindering the creation of consistent product offerings amongst different vendors. Systems comprising of a head-end and street electronic concentrators are being installed, i.e. in Sweden, where they are providing high speed Internet connections to multiple dwelling unit.