GPON, My Poems

Gigabit Passive Optical Networking (GPON)

Optical fibers have the capacity of 25 Tb Hz of bandwidth, which is almost 1000 times greater than RF (radio frequency) bandwidth.  Light is kept in the fiber core by total internal reflection.  This makes the fiber act as wave-guide.

Optical Fiber is used in Telecommunications as a medium/channel to carry the information.  The information can traverse long-distance as the attenuation of the signal/information is very less which in contrast to the information traversed using RF.

Each Fiber can carry multiple channels using different wavelengths of light, this is called as Wavelength Division Multiplexing (WDM).

total internal reflection in an optical fiber

PON (Passive Optical Networking) is connection from one point to multiple points (P2M) using an optical splitter which is passive ( which does not consume any power) splits the signal into 2,4,8,16,32.. directions.  A PON consists of an OLT (Optical Line Terminal) at the service provider at the central office and  ONU (Optical Network Unit) which is a collection of ONT’s (Optical Network Terminal) at the consumer end.

The word GPON which is Gigabit Passive Optical Networking is evolved from BPON (Bandwidth Passive Optical Networking).  Gigabit is the speed/rate of the information carried on the Fiber i.e., the rate of the information is in GigaHertz….

The data is transmitted from OLT to ONT i.e., in downstream as a broadcast manner but encryption (AES) Advanced Encryption Standards is used to prevent eavesdropping and as TDMA manner from ONT (users) to OLT.

At ONT the light (optical signal) is converted into electrical signal.  Each ONT has many ports like say Ethernet, VOIP, IPTV, etc i.e., a single fiber at the end user provides many services.  It is usually referred as FTTU/FTTH (FTTX) fiber to the user/home.

GPON key technology.

OLT identifies ONT’s using ONU-ID (Identifier) which is 8 bit identifier and it is unique.

ALLOC_ID is a 12-bit number that the OLT assigns to an ONU to identify a traffic-bearing entity that is a recipient of upstream bandwidth allocations within that ONU. This traffic-bearing entity is also called T-CONT.

A Transmission Container (T-CONT) is an ONU object representing a group of logical connections that appear as a single entity for the purpose of upstream bandwidth assignment on the PON.

will keep posting more…

5 Comments to “Gigabit Passive Optical Networking (GPON)”

  1. The wavelength used for video is 1550 nm overlay/IP and voice call is TDM manner. And average bit/unit is 40Mbps. This is not a wireless communication, so for each ONU group we can lay a fiber unlike in wireless (where BW plays a vital role) I suppose. Anyway, if you take the nextgeneration WDM PON, there you could also control the individual data rates for ONT since data is sent through different wavelengths.

    For more info, you may look this paper


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