Splitters and branches and PON, oh my!

Passive optical networks (PONs) are a great way to provide cost-effective broadband services. But they use a tree topology with splitters, complicating the use of standard optical time domain reflectometry (OTDR). Is there a way to have your own Glinda the good witch watching over your fiber? Now, the answer is yes!
Tom Coburn
Yellow brick road and ruby slippers

Why are PONs cost-effective?

PONs leverage shared infrastructure to reduce costs. Note that there are a variety of flavors of PON, including GPON, XGS-PON, NG PON, etc. They all use a point-to-multipoint (P2MP) fiber architecture with passive optical splitters to reduce the total fiber required. And they use the same fiber for both transmission directions. That’s how they deliver subscriber services at lower costs than direct or point-to-point fiber connections. Specifically, GPON is now the standard way to deliver residential Gigabit services. But what happens if we want to look behind the curtain and see what’s happening on the fiber?

How do service providers usually test and monitor fiber?

With portable OTDR test sets. An OTDR shoots a short pulse of light down the fiber. By monitoring the reflected light over time, the OTDR can show the loss over distance, as well as the locations of any splices and the total length. That’s handy for both verifying a new fiber installation as well as figuring out where the dreaded backhoe dug up and broke a fiber. But a portable OTDR can’t be used in service, and it’s not a resource that can be installed centrally and used on demand. Now Adtran has a horse of a different color.

Innovations like Adtran’s ALM products improve fiber performance by monitoring continuously and non-intrusively. And it works with any fiber technology, regardless of the supplier. Our ALM is like a radar that lets you continuously see what’s going on in your fiber network. Now you get an alarm when the backhoe strikes – rather than waiting for a call from your customer. You can even see fiber degradation due to impairments like stress and water penetration, which can both cause changes in loss.

Sounds great. What’s the problem?

Actually, there are two problems – and we’ve solved them both.

The first is that the presence of multiple branches on the PON tree means multiple reflections at the OTDR. This can mean confusing results at the OTDR.

The second is that an optimal reflection requires the addition of a reflector at each endpoint. That’s an additional cost to buy the reflector and an additional cost to install it. 

OK. So what’s Adtran’s solution?

Adtran’s ALM products have long provided continuous and non-intrusive monitoring of all types of PON networks. Now with our new deep PON assurance (DPA), we can perform this monitoring of PON networks without the need for reflectors. Removing the need for reflectors ensures compatibility with any existing PON network while reducing operational complexity. Eliminating reflectors also means you can save up to 50% of the already low system cost for a 1:32 split ratio. And up to 70% for a 1:64 split!

A complete solution for GPON 

Adtran’s ALM with DPA enables efficient, low-cost and continuous monitoring of PON deployments, without the added cost of reflectors. It’s compatible with existing fiber builds, and any PON technology, so it’s a future-proof solution. Contact Adtran to learn more. And be sure to stay on the yellow brick road.

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