GPON network. (Equipment Alphion)


    The GPON network is an end-to-end, well-engineered, carrier-class optical network designed to deliver triple-play services (voice, video, and data) from a Central Office to individual businesses or dwellings.

The Alphion GPON network includes:

    ­ AOLT-4000;
    ­ AONTs;
    Splitters;
    Amplifiers;

     The core of the Alphion GPON network is the optical line terminal AOLT-4000 which is available as a fully redundant, multifunction rack-mounted shelf located at the carrier Central Office. The AOLT-4000 system serves as a service provider endpoint, interfacing with the service provider’s broadband network gateway via Ethernet-based network interfaces, and connecting to the ONTs in the subscriber premises via GPON.

Connectors

The primary functions of the AOLT-4000 are to:


    * Securely manage and aggregate traffic between multiple ONTs (AONT-100C and AONT-100) and the uplink Ethernet interfaces.
    * Adapt network traffic between the service provider’s Ethernet and IP-based metropolitan area network and the GPON network.
    * To serve as the central network-element that facilitates management of the GPON network, including the ONTs.


    Data meant for one AONT is therefore 2.488 Gb/s divided by 128, or approximately 20 Mb/sec downstream, and half that or approximately 10 Mb/sec, upstream for a 128-split GPON.

    In the downstream direction, data from the AOLT-4000 is broadcast to all AONTs. However, GPON technology allows for establishing virtual channels (known as GEM ports) between the AOLT and AONT, such that an AONT accepts only traffic received on the virtual channels allocated to it, while filtering out channels not assigned to it. Data meant for an AONT can be protected from being intercepted at other AONTs via a cryptographic encryption mechanism.

    In the upstream direction, the data is time division multiplexed access (TDMA). Each AONT uses its TDMA timeslots to send traffic back up to the AOLT-4000. To manage the slight transit time differences among AONTs at different distances to the AOLT-4000, the AOLT-4000 executes a ranging algorithm to discover which AONTs are connected to the network. The AONT can reply after it is powered up using its serial number as a unique identifier. The ranging process logically equalizes the distances for all of the active AONTs. Then the AOLT-4000 determines the timeslot for each AONT to transmit upstream in terms of the time delay. TDMA transport over the GPON relies on a framing clock on each port’s MAC to provide the clock for frames sent downstream. The clock is recovered and regenerated at the AONT and is used as the source of clock for the upstream data. In this way, the two clocks track each other and cannot drift apart.

    As with copper-based Ethernet networks, the 128 splits can be grouped or aggregated to provision how much bandwidth each AONT is allocated. However, each fiber supports a maximum of 128 timeslots. Once they are all provisioned, the fiber bandwidth is fully allocated.

Connectors