ATM and broadband PONs. APONs were the first ATM-based PONs and provide voice and data, but not video, services. They offer speeds of 155 to 622 Mbits per second downstream and 155 Mbps upstream, and support 16 or 32 nodes and dynamic upstream bandwidth allocation. APON deployment is phasing out as carriers move to broadband PON systems, which can handle video.
BPON technology is an APON extension that moved the wavelength for sending data and audio from 1,550 to 1,490 nanometers, thereby opening up the 1,550-nm band for video, explained Dave Cleary, vice president of advanced technology at Optical Solutions, a PON equipment manufacturer.
Transceiver improvements have provided the increased power and sensitivity required for handling video without significant added cost.
Michael Howard, an analyst with Infonetics Research, estimated that 75 percent of PON systems in the US, where most telecommunications carriers already use ATM, are BPON based.
Ethernet PONs. EPONs support data rates of 1.244 Gbps in each direction shared among 16 to 256 nodes. The EFMA's Easley predicted next-generation EPON equipment will support data rates up to 10 Gbps. EPONs are based on the IEEE 802.3ah—Ethernet in the First Mile—standard.
The main attraction of Ethernet in PONs is that most companies already use the technology in their corporate networks, said Easley.
Howard estimated that 75 percent of PON systems in Asia, where most telecommunications carriers don't use ATM, are Ethernet based.
Gigabit PON. GPON supports data rates of 622 Mbps to 2.488 Gbps downstream and up to 2.488 Gbps upstream, shared by 16 to 128 nodes. The higher speeds enable carriers to split the bandwidth to serve a greater number of nodes than APONs or BPONs.
According to Howard, industry observers see GPON as the successor to BPON because it is faster and flexible, supporting ATM, Ethernet, and TDM on the same network.
With GPON, all services are mapped onto the PON using either ATM or GEM, a variant of Sonet's (synchronous optical network's) generic framing procedure. GEM lets a GPON link carry both Ethernet and TDM traffic and also adds QoS and recovery capabilities.
Carriers are deploying GPONs throughout the world. Two major GPON equipment manufacturers are FlexLight and Optical Solutions.