The optical line terminal is the central office-based hardware that sits between the carrier's metro optical network and the homes hooked up to fiber connections. The OLT configuration varies depending on the vendor and the number of homes being served.
OLTs are sold as shelves, which house line cards, and are mounted in racks. A rack is seven feet tall and contains 42 rack units of vertical space. If a carrier deploys a GPON OLT shelf that measures 14 rack units, it can house three such shelves in a rack.
An OLT shelf usually supports between 1,000 and 2,000 homes. Hitachi Telecom (USA) Inc. 's OLT shelf, for example, supports 32 PON interfaces. Since each PON can be split up to 32 homes, the OLT shelf supports up to 1,024 homes.
In urban areas, central offices naturally tend to serve a higher number of homes. Verizon Communications Inc. (NYSE: VZ) typically serves 15,000 to 20,000 customers from each urban central office. In more rural areas, 1,000 to 2,000 homes per central office is more common.
An optical network terminal sits at the customer's home and can support a variety of features including streaming video, RF video, and TDM services. Some vendors such as Zhone Technologies Inc. (Nasdaq: ZHNE) have even tried to differentiate on features such as the ONTs' power source. (See Zhone Debuts Line-Powered ONT.)
GPON equipment in general is a fiercely competitive market since there are only a few carriers doing massive rollouts. That has led some vendors such as Calix Inc. (NYSE: CALX) and Occam Networks Inc. (Nasdaq: OCNW) to focus exclusively on Tier 2 and Tier 3 carriers rather than spend resources courting a Verizon or an AT&T. (See Calix Ships 200,000 ONTs and Calix Adds MDU ONTs.)
As far as Tier 1 carriers go, previous PON-equipment winners like Alcatel-Lucent (NYSE: ALU) have locked up sizable shares of the GPON rollouts. Surprising newcomer Ericsson AB (Nasdaq: ERIC), however, managed to land a lead supplier roll at AT&T Inc. (NYSE: T) thanks to its acquisition of Entrisphere. (See Ericsson Buys Entrisphere and AT&T Picks GPON Players.)
Adtran Inc. (Nasdaq: ADTN) is another recent latecomer looking to deploy in the Tier 1 space. (See Adtran Adds GPON.)
Among smaller vendors, Pannaway Networks is throwing its name into the ring through its acquisition of TelStrat International 's access division. (See Pannaway Goes After Calix.)
Thanks to the lack of progress with GPON interoperability standards, carriers typically purchase ONTs and OLTs together as a set. In table 1 below, we’ve listed the ONT vendors and their basic ONT product lines, and indicated the basic sets of features that they offer. In table 2, we've listed the OLT vendors along with the main product line they sell in that category.
Since vendors commonly sell ONTs and OLTs as a single system, some of the companies listed have the same product name for both types of gear.
Table 1: ONTs
|Vendor||Product Line||SFUs||MDUs||IPTV||RF Video||POTS Ports||Gigabit Ethernet|
|Cambridge Industries Group|
|* NSN has ceased development of this product line. It is still available but will no longer be improved upon.|
Table 2: OLTs
|Enablence (Wave 7)|
|*NSN has ceased development of this product line. It is still available but will no longer be improved upon.|
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