Wednesday, February 14, 2007

Passive Optical Networks

Don Wade from Nassau Community College on Long Island passed along an interesting article from EE Times today titled “'Last mile may be light-centric” ( The article discusses last mile options for voice, video and data services and references a "Last Mile Options" panel held at the International Solid State Circuits Conference. The panel discussed the advantages and disadvantages of passive optical networks or “PONs”.

A passive optical network (PON) is a point-to-multipoint, fiber to the premises network architecture that uses fiber and wavelength division multiplexing (WDM) to pass multiple signals (typically 32) over a single fiber strand. Point-to-multipoint networks are more efficient that the legacy point-to-point copper networks the phone companies have been installing and maintaining over the years. In addition to using less fiber, PON optical splitters do not require power.

Here is a list of popular PON versionstaken from Wikipedia:

  • APON (ATM Passive Optical Network). This was the first Passive optical network standard. It was used primarily for business applications, and was based on ATM.
  • BPON (Broadband PON) is a standard based on APON. It adds support for WDM, dynamic and higher upstream bandwidth allocation, and survivability. It also created a standard management interface, called OMCI, between the OLT and ONU/ONT, enabling mixed-vendor networks.
  • GPON (Gigabit PON) is an evolution of the BPON standard. It supports higher rates, enhanced security, and choice of Layer 2 protocol (ATM, GEM, Ethernet). In actuality, ATM has not been implemented.
  • EPON (Ethernet PON) is an IEEE/EFM standard for using Ethernet for packet data.

A PON is basically a shared network with an Optical Line Terminal (OLT) in a provider central office feeding a single fiber with multiple signals. Imagine a single fiber running down your street serving 32 homes with voice, video and data services. At your home you have another box called an Optical Network Terminal (ONT) that reads all encrypted packets (all packets are encrypted for security) on the fiber and only accepts ones addressed to you.

The EE Times article discusses current technical plans for cable and telco companies including a brief piece on using wireless for the last mile.


Last mile may be light-centric:

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