Recommendations for Broadband Passive Optical Networks (B-PON) and Gigabit Capable Passive Optical Networks (G-PON) are now reaching maturity in ITU-T. Many vendors are offering conformance with the B-PON series of standards and products with G-PON conformance are emerging. These systems typically operate over a maximum 20 km, 32-way split optical distribution network. The capacity of B-PON ranges from 155/155 Mbit/s symmetrical to 1240/620 Mbit/s asymmetrical transmission. G-PON extends this capacity to 2.4/2.4 Gbit/s and allows more efficient transmission of Ethernet. This paper presents an update on the status of standards on passive optical networks systems with emphasis on recent developments in Q.2/15 of ITU-T.
This paper describes how an experimental full services access network has been constructed at BT Labs and presents views on how its performance could be improved to meet the reliability and traffic loading requirements expected in real applications such as fiber to the business and fiber to the cabinet. The experimental network included: asynchronous transfer mode (ATM) switch, an ATM passive optical network (PON), very high speed digital subscriber loop (VDSL) customer drop and ATM forum 25 Mbit/s customer network. The design and realization of the VDSL customer drop, the signaling system and the interfaces between the system elements formed a major part of the design and construction work at BT Labs. The ability to cope with varying service demand and achieving the necessary quality of service are important requirements for roll-out systems. This paper describes how these requirements could be met in the design of future proprietary equipment.
In upgrading the access network to be broadband capable, re- use of existing infrastructure is essential to manage the risk associated with this development. FTTCab (fiber to the cabinet) has been proposed as an architecture that can make this development economic to provide 12 Mbit/s to the customer and 2 Mbit/s back into the network. The FTTCab architecture uses an optical fiber overlay to an active node sited at the primary cross-connect point (PCP) in the copper access network. Frequency multiplexing allows the copper pair infrastructure to be re-used without changing the existing narrowband services. FTTCab is at the mid-point of a range of access topologies with respect to the siting of the DSL (digital subscriber loop) technology. The DSL modem can be sited at the home, curb, cabinet, or in the exchange to suit a range of distance/capacity requirements. This enables a simple revolution of the current network to FTTCab, and allows the architecture to be flexed to satisfy particular business needs.
The future widescale deployment of broadband multiservice networks is dependent on an acceptable commercial relationship being achieved between new service revenues, operating cost savings and the network capital investment required. A new generation of broadband access networks is envisaged which is capable of both broadband and narrowband transmission, and can provide both broadcast and interactive services over a much larger coverage area than copper pair yet makes good use of existing copper pair infrastructure. To ensure that such networks emerge practically and are economically viable, requirements must be agreed and a wide market established. The aims of this paper are to draw attention to the benefits of networks with broadband and narrowband capability, to discuss the benefits of co- operation on requirements and to describe what has so far been achieved in the standards bodies.
This paper reports on the investigation of the traffic throughput performance of passive optical networks using both time division multiplexing (TDM) and asynchronous transfer mode (ATM) transmission techniques. In particular discrete event computer simulation techniques are utilized to study the performance of these networks under asymmetric traffic loading conditions. The performance characteristics obtained demonstrate the degradation of the network traffic throughput using TDM, whereas ATM transmission proves resilient to even high levels of asymmetric traffic loading on the passive optical network.
This paper builds upon earlier work concerned with high definition television (HDTV) transmission for application in the future optical fibre local telephone network. The HDTV signal is introduced by reference to the NHK system originating in Japan and the HD-MAC system supported in Europe. Both digital and analogue intensity modulation schemes for HDTV transmission on single mode fibre are then assessed in relation to transmission bandwidth, receiver signal to noise ratio, multiplexing capabilities, terminal complexity and cost. The practical implementation of a high speed pulse code modulated (P04) HDTV single mode fibre transmission system is then discussed. Details of the implementation of a sub-carrier frequency modulation (SCFM) system are then followed by a description of the practical realisation of a novel wideband pulse frequency modulation (PFM) system again for HDTV transmission on single mode fibre. Modification of this latter system for square wave frequency modulation (SWFM) is then discussed. Finally performance data on the aforementioned systems are presented and compared in order to determine specific trade-offs associated with these modulation techniques for optical fibre HDTV transmission.