David Hashman/Knowledge Works LLC
24 Sep 2010
When considering a FTTH project, people often ask which technology they should use. My initial response is usually a technically savvy, "It depends."
A number of technical FTTH network alternatives are available, and they all have advantages and disadvantages. The challenge is to select the technology that is the most cost-effective match for the customer's current and possible requirements in the future.
The choices generally fall into two categories: passive or active.
Passive optical networks (PONs) have no powered components between the end subscriber and the main distribution point such as a central office or headend.
The key characteristic of PONs is that their fiber networks utilize a point-to-multipoint architecture that looks like a tree structure.
Passive optical splitters are used to divide the signal among multiple subscribers, typically 32 or 64. The fiber between the last splitter and the end subscriber is dedicated to the subscriber, but all other fiber is shared.
The most common types of PONs are Gigabit PON (GPON) and Ethernet PON (EPON). The current ITU-T G.984 GPON standard has an asymmetrical bandwidth capacity of 2.488 Gbps downstream and 1.244 Gbps upstream.
The IEEE 802.3 EPON standard has symmetrical bandwidth capacity of 1 Gbps upstream and downstream. The standards for both PON technologies, however, are now being updated to support 10 Gbps speeds.