Friday, July 21, 2017

Overriding Issues with a Fiber Overbuild

What to Know: Fiber Overbuilds

As original fiber routes are now coming due on their life expectancy, we've found out a lot about how cables age in their environments. That discussion alone could fill multiple blogs and whitepapers. The improvements in optical fiber design are pushing back the cabled fiber retirement age past 40 years. But, what if you need to bite the bullet and overbuild an existing route to maintain your QoS?

The cost of new excavation or boring can be detrimental to your balance sheets, so what can you offer them? Cable jetting in an override application can be a feather in  your cap, but you should proceed carefully before going down this route. Here are some things to consider.

Duct Depending

A thorough inspection of the quality of the existing pathway should be conducted. If the duct integrity is good, and it can hold pressure, you should have good results. A good pressure test alone may not guarantee success, however.

Going the Distance

Don't count on the claims of your cable blowing equipment to get you there. Due to the additional air chamber in your Y-Block, there is more potential for air to leak out of even the best system. The parachute style carrier used for overrides isn't as effective at sealing the air in front of the cable, which will slow you down as well. Not to mention the added friction of the cable running against what's inside the duct, try not to be overzealous with distance claims.

If your runs are 1000 - 2000 feet, and you have good duct integrity, you should see success. The equipment manufacturers will still make no guarantee as every job is different.

How did the first cable go in?

If you know the existing cable was blown in originally over longer spans, you could be up for a significant override challenge. Since cable blowers push the cable through a pressurized duct, a cable may not lay flat inside the duct towards the end of the run. Picture a wet noodle with peaks and valleys. If a cable was pulled in, it should be laying flat. Ultimately you would want a cable to be laying flat at the bottom for you, but that doesn't always work out.

Microduct First

You can pressurize a microduct and send it through your existing pathway if the room allows for it. We have run simulations of this at our Collegeville facility for customers interested in trying this method. This will also insure that the cable could easily be reclaimed and the pathway re-used if necessary.

Go Smaller

New microduct cable technologies are pushing the envelope on how many optical fibers you can cram into a space. Do not expect this trend to change. The most recent development from AFL is their LM200-Series OSP Microcore cable that is the smallest thing yet to be Telcordia GR-20 compliant. That being said, it's not the product you'd want to lead with in a greenfield. But this is your answer if you originally wanted to go with a 432 fiber count, and you could only get 96 strand using traditional microduct cable. Fair warning: your splicers may throw objects at you for specifying 72f per tube cables.

Get a Guru

Comstar, as well as our suppliers, have experience assisting with overrides in the past. We all want your job to run smoothly, and we are glad when we can champion another success story. We would certainly like to offer our advice and expertise along the way.

The costs for override installations certainly justify themselves, but it may not work for every situation. If you've already done an override, we would love to hear about the pitfalls and successes of the project. If you're considering an override, please don't hesitate to contact us to see how we might be of service to you or your contractor.