Talk:Passive optical network

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[edit] what is passsive

The last I saw some PON gear which works on TDM, they all had a power cable sticking into it. so what exactly is passive about it?

the above comment was by 59.145.141.130 on 2006-06-27T03:12:29 Riick 06:25, 10 March 2007 (UTC)

Answer: The passive part is the optical fiber itself. "PON" is something of a misnomer because any fiber optic transport system has a "passive" piece of it - the fiber itself. "PON" colloquially means a point to multipoint optical transmission system.

the above comment was by 70.250.189.35 on 2006-07-19T23:33:03 Riick 06:25, 10 March 2007 (UTC)

"Passive" refers to the fact that the outside plant (OSP) is unpowered, i.e., in a typical PON, there are no powered nodes OTHER THAN those at either end of the system. Every transmission system requires a powered line driver in the service provider office (aka central office, CO, Head End or Hub) for the downstream transmission, and a powered driver at the customer end for the upstream transmission. However, in most electrical and many optical access systems, there is is some type of powered device in a node OUTSIDE one of these controlled environments to provide regeneration, repeating, splitting, switching and/or multiplexing, or even protocol conversion. This outside plant equipment (OPE) requires dedicated real estate, power, battery backup, and regular maintenance. These are those big green metal boxes you see on your street, near parks, etc. A primary advantage of PON is that the outside plant is entirely passive... just fibers and passive fiber splitters that can be buried or strung on poles and ignored, requiring virtually no maintenance. The network can evolve simply by upgrading the endpoints. This is a huge cost savings, over time.

TDM is simply a service over PON, and is irrelevant to this issue.

the above was Jayshuler's 2006-10-11T12:48:58 edit of 70.250.189.35's comment Riick 06:25, 10 March 2007 (UTC)

This article should not be merged into PON (passive optical networks). FTTP is a network architecture that has two major implementations: PON (including GPON, EPON, GEPON, etc) and Active Ethernet (many naming variations). FTTP should remain the umbrella article, with links into more specific article.

81.2.106.242 06:15, 6 October 2007 (UTC)

[edit] Amount of office equipment?

The introduction currently says, "A PON configuration reduces the amount of fiber and central office equipment required compared with point to point architectures." However, my understanding is that PON does not use less equipment in the central office than active FTTP does. It requires more powerful OLT lasers in the CO. In some (but not all) cases it may be more compatible with legacy equipment already in the CO. But I don't understand why it necessarily requires less equipment in the CO. Please discuss. Riick 09:10, 10 March 2007 (UTC)

It depends if by "point to point" you are refering to the legacy copper architecture, then yes PON requires much less CO equipment than traditional copper. If we are only considering fiber optics, then the concern may be unfounded. FTTP is refering to the name of the grander network architecture, whereas PON is describing the method in which the technology is implemented. PONs are inherent to and exists within FTTP, and therefore the two use the same amount of equipment. FTTP networks use PONs to multiplex service though a single fiber and then split to many end users in order to reduce installation and maintenance costs and to improve reliability. You see, it's difficult to talk about one without mentioning the other.
Now if we're comparing Point to Point PON vs. Point to Multipoint PON, the multipoint scenario described in the BPON standard uses much less CO equipment and fiber originating from the CO. A PON laser is able to serve 32 ONTs instead of just one end device. This significantly reduces not just the fiber equipment in the CO but also the fiber facilities leaving the CO to the point in the field where the signal splits.
It is also true that certain legacy equipment that was installed prior to FTTP and used for other purposes can be reconfigured for current FTTP applications. --Toddyboy711 20:06, 16 May 2007 (UTC)
The above response by Toddyboy711 is well-written, informative, and appreciated. However, my concern has to do with the fact that there are actually three FTTP technologies: PON, direct fiber, and AON. Since standardized terminology has not exactly been a strong-point of the fiber-optic communications industry, I will have to be clear about what I mean. By PON I mean the technology that Toddyboy711 is calling "point-to-multipoint PON". By direct fiber, I mean any technology where each fiber leaving the CO serves one and only one household (one example is what Toddyboy711 calls point-to-point PON). And by AON (also called "Active FTTP"), I mean a technology that is very similar to PON in layout and amount of fiber used (see FTTP#Active_optical_network for details). Unfortunately, both AON and direct fiber are both called point-to-point by the industry, despite the fact that they could hardly be more different from each other. At the time I wrote my original question, I thought this article was incorrectly characterizing AON. Instead I now think that it does not mention AON at all. I will remedy this when I have time, unless someone else gets to it before me. -Riick 08:12, 18 May 2007 (UTC)
(As an intesting sidenote, I believe the reason that AON and direct fiber are both called point-to-point is due to ambiguities in the definition of what a point-to-point network is. Depending on who you ask, a point-to-point network seems to mean (1) a network where each signal only needs one "hop" to reach its destination (as in direct fiber), (2) a network where more than one "hop" may be required but where each "hop" is over a point-to-point link (as for AON), or (3) a network where every node has a direct connection to every other node (as in what a tangle of wires!)) -Riick 08:12, 18 May 2007 (UTC)

[edit] BPON/GPON Bitrates and Equipment

An attempt was made by an unregistered user to include bitrates for PON and GPON. Besides being entirely incorrect, I don't believe it is the purpose of the "PON" article to go into details about each standard. There are other pages with specifics for both BPON and GPON standards. Simply giving a clear and concise definition of what PON means, with minimal mention of equipment and providers seems sufficient.

For the record, bitrates are offered at different service levels depending on the service provider. There are no standard bitrate offerings, and they tend to change quite often even within the same prover. The BPON standard states the total allocated downstream bandwidth of of the shared PON is 622 Mbps and 2.4 Gbps for GPON. Of course a provider can and will oversubscribe the PON. The equipment is NOT the same between the two standards. Moving from BPON to GPON requires both new OLTs and ONTs alike. I don't believe there is any requirement for GPON equipment to be backwards compatible. The only thing that doesn't change are the PON elements themselves (the fiber medium, splitters, distribution hubs, etc.) Toddyboy711 (talk) 21:43, 26 November 2007 (UTC)

Upon further research, BPON and GPON both redirect to PON. This may warrant some mention of speed capability. ITU G.984.1 states GPON is either 1.2 or 2.4 Gbps down. The G.984 page simply links you to the ITU specs. I am indifferent about including this info, as long as it is correct and properly cited. Toddyboy711 (talk) 22:17, 26 November 2007 (UTC)