PON or AON: Fiber is the Way to Go

By Jeremy Barndt, Sr. Project Consultant, JBA Consulting Engineers

Audiovisual_Jeremy Barndt

There has been much debate and discussion in recent months about looking to the future for the structured cabling infrastructure of a building.  In years past the obvious choice was providing fiber from the core switch in the data center or MDF to telecommunication rooms or IDF’s around the facility then running copper category cabling to the device location or work station.  This solution while still viable isn’t necessarily the obvious choice any longer.

With Passive Optical LAN and Active Optical LANs latest offerings fiber is a more viable solution and for the forward looking IT professionals it may be the only choice.  For the purposes of this article when we talk about fiber optic cabling we will refer toSingle Mode Optical Fiber (SMOF).  We do understand that Multi-Mode Optical Fiber is out there and viable but it is essentially an improved copper cable that doesn’t use copper.  With the cost competitiveness between SMOF and MMOF electronics the cost per unit of data is arguably less expensive using SMOF but that debate is for another article.

SMOF offers multiple benefits over copper including bandwidth, distance limitation and space requirements.

Distance Limitation

Category cabling is limited to a total channel length of one hundred (100) meters or three hundred twenty five (325) feet.  This is the standard that is accepted by the industry worldwide.  The channel length includes five (5) meters or sixteen (16) feet of patch cable on each end which shortens the field cabling to a maximum of ninety (90) meters or two hundred ninety-two (292) feet.

SMOF has not practical distance limitation in a campus environment.  100 Gb/s over a single core of SMOF can be achieved over distances of over thirty (30) kilometers or over eighteen (18) miles.  Achieving 100 Gb/s is very expensive currently but electronic costs are dropping continually.

Bandwidth

Category 6a cabling supports 500 MHz, SMOF supports in excess of 100 Terahertz.  The total available bandwidth of SMOF has not yet been exceeded, it’s as close to future proof as you can get in a technology setting.

Space Requirements

With category cable you are required to have TR spaces or IDF’s so the maximum field cabling is less than the ninety meter distance limitation as discussed previously.  Each room requires dedicated air conditioning, fire protection, UPS power and security measures.  With SMOF the number of rooms can be eliminated or greatly reduced.  In larger campus environments its prudent to provide dedicated TR or IDF spaces for each building or larger areas but there is no specific requirement, it’s an owner choice.  Each space is going to be roughly ten by ten or one hundred square feet.  BICSI standards say that a space is required for each ten thousand (10,000) square feet.  For a building of one hundred thousand (100,000) square feet ten (10) spaces would be required.  A typical hotel room is five hundred (500) square feet or less and averages $125 per night.  That means it would generate $0.25 per square foot.  The ten (10) spaces would be at least one thousand (1,000) square feet.  Every day this is a potential revenue loss of over $90,000 per year, most hotels earn more than $0.25 per square foot and the potential revenue loss is much greater.

There are two options when deploying fiber to the room or work space, AON or PON.  The major factors that contribute to this decision are cost, redundancy, maintenance/operation, bandwidth and structured cabling.

Cost is a bit tricky to deal with because there are so many factors to consider.  Owner discount is a big factor, manufacturer deal is another factor as is how to compare two competing technologies.  Our experience has shown that for a given size hotel the cost of electronics is generally the deciding factor.

AON electronics can be purchased with full redundancy using dual GBIC or mini BIC fiber connections and can be redundant across the entire deployment.  PON does not offer redundancy.

AON setup, maintenance and operation uses the same syntax, protocols and programming languages that copper switches do.  There is nothing new to learn.  Programmers and technicians are very easy to find.  PON offers very simple setup, there is very little maintenance and operation is transparent once setup because it’s passive.  There are compatibility issues with both systems.  Neither supports a full analog or digital phone system.  PON can support edge devices that are analog but will require an IP head end and specific protocols to support the phone features.  AON only supports IP phones.

AON offers a backbone of up to 100 Gb/s to each distribution switch and up to 10 Gb/s to the edge device.  Each port could offer 10 Gb/s to the device.  PON uses shared resources and allocates bandwidth dynamically across the share.  This allows high demand ports to get full bandwidth while other ports are not using bandwidth.  One port supports up to 10 Gb/s but like your home internet speed when everyone gets home at 5:30 after work, you don’t get the full potential.

AON and PON can be supported on the same infrastructure.  This means you can switch from one technology to the other at refresh periods but this needs to be planned so the switch will be painless.

Fiber is for the forward thinking.  It supports the technology needs of today and is the clear path for the technology of tomorrow.  We like to think we design with the future in mind, even if we don’t know exactly what it holds.  Good luck and choose wisely.