Tip of the Week:
With many communications companies trying to get fiber to the home (FTTH) or premises (FTTP) as a last mile solution for their customers, the question of what architectures can be used comes up? One solution is passive optical network known as PON. PON is a point to multipoint architecture where each customer has one dedicated fiber branch that travels a short distance to a local hub where other customer’s fibers also terminate. They are combined by a passive splitter/combiner then travel down a single trunk, together, to a central office.
There are three major types of PON (passive optical network) systems that all offer their own set of advantages and disadvantages.
GPON, or Gigabit PON, is the grandchild of APON, which was a PON system built on the ATM protocol. It is the ITU PON standard and uses TDM and encapsulates voice, video, and data separately. The main advantage of this method, is that it is more compatible with legacy TDM equipment currently installed in many COs. The disadvantage is that many layers of encapsulation are needed to make it work and security can be an issue.
EPON, or Ethernet PON is the IEEE standard of PON, and it uses a pure Ethernet method of multiplexing where Ethernet frames are broadcast into the fiber, as in a standard Ethernet network. It uses TDM for upstream data, but downstream the CO equipment broadcasts out frames as they come in. The advantage to this is that most data nowadays starts and ends in the IP format, so it requires less encapsulation. But the disadvantage is that there is no guarantee of speed when many users are on at the same time since the overall network rate is finite and fixed as well as the same security issues as GPON.
WDM PON is a different method of PON that doesn’t use TDM, but Wave Division Multiplexing (WDM) to multiplex the signals. It takes either CWDM or DWDM signals for all the end users and combines them onto a single fiber trunk with a passive field unit multiplexer, and then in the CO, another passive multiplexer separates them out again. This gives each user a dedicated channel, making it easy to customize the speeds and protocols used on the network and vastly increases the security. All user channels are completely independent and very secure. The disadvantage is that the fiber transceivers (DWDM or CWDM) can be more expensive than GPON or EPON.
Pertinent Products/Services:
Telecom Engineering announces new ** WDM PON SYSTEM **
Features include:
- up to 44 dropped channels per trunk
- provide any data rate service to each drop from 100mbps to 10gbps, and future 40Gbps and 100Gbps
- full channel bandwidth available upstream and downstream
- very secure since each WDM channel is dedicated to one customer/drop
- fully transparent to all protocol
- transport Ethernet, GigE, 10GigE, ATM, and/or RF video on any channel
- uses standard CWDM or DWDM transceivers
- passive and reliable field multiplexers that are simple to install and maintain
- extended distances available
- “Planning Fiber Optic Networks”, ISBN 0-07-1499199 available from Amazon.com . Table of contents can be seen here : http://www.TelecomEngineering.com/products/resources/planningfibernetworks.htm ,
- -“Fiber Optic Installer’s Field Manualâ€, ISBN 0-07-135604-5 available from Amazon.com. Table of contents can be seen here http://www.TelecomEngineering.com/products/resources/field-manual.htm
