Blown Fiber and Jetted Fiber DAS Installations
Apr 13, 2016
Blown Fiber and Jetted Fiber are two new terms we're hearing in wireless networking industry regarding DAS installations. These terms are used to describe the use of compressed air when placing microfiber cable. Both these terms suggest that the microfiber is being pushed or propelled by air through a microduct; However, "air lubrication" would possibly be a more appropriate phrase. Jetted Fibers and Blown Fibers in distributed antenna systems (DAS) help push fiber deeper into the network to increase bandwidth and keep construction costs down to allow for future expansion.
Air is used as a means of reducing friction between the inner wall of the microduct and the microfiber cable jacket. Like when the air is off a puck on an air hockey table, the puck has difficulty overcoming the friction between its surface and the hockey table's surface. Static Friction and Dynamic Friction are the two types of friction the microfiber (or puck) must overcome in order to move forward efficiently.
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Static Friction:
When an object is not in motion, static friction is the existing force between the contact surfaces. Static friction tells us how much force is required to start moving that object.
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Dynamic Friction:
When an object is in motion, dynamic friction is the existing force between the contact surfaces. Dynamic friction tells us how much applied force is required to maintain movement of that object.
The friction is greater when the object is heavier, which means that when the microduct contains more microfiber it must overcome more friction. This friction-issue between the two surfaces can be lessened by lubricants, such as air. Using a lubricant means that friction resistance is not dependent on surface materials but is almost entirely independent on the force between both surfaces. Friction and temperature are still related, and the viscosity of the lubricant is affected by the temperature with lubrication.
Air pressure, pounds or bars per-square-inch (PSI), is more important than air volume, which is generally referred to in CFM (cubic feet per minute). The maximum and ideal pressure to be used is 15 bars (217 PSI) at 35 CFM; while the minimum pressure is 10 bars (145 PSI) at 180 CFM.
There's less likelihood the surface of the microfiber will come into contact with the surface of the microduct when the air pressure is greater. Therefore, the air acts as a lubricant by raising the microfiber away from the microduct's wall. This allows operators to easily push fiber deeper into the network; which means that the fiber goes where it is needed to increase bandwidth to subscribers, and it also keeps construction costs down by allowing for future expansion.
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4 comments
I know distributed antenna system installations can be tricky (particularly for exterior DAS), but this air system sounds like it makes for easier installation and for any additions that need to be made down the road. It kind of reminds me of the old pneumatic tube systems they used back in the day in offices. They’d slap a canister in a tube with a message and send it to whichever department it was “addressed” to.
Excellent explanation of air blown fiber optic cables. I’ve heard how microfibers are used during air blown fiber installation on DAS systems. It reminds me of a plant’s roots stretching out to receive nutrients which in this case, are receiving cell phone signals and boosting them so you have the same signal throughout an area. Perhaps a neural network is a better analogy. Either way, air blown fiber installation looks like an ideal way to boost your DAS. How does air blown fiber work? This explains everything.
I’ve been researching DAS systems for a school paper and I understand they rely on microfiber cables to make sure your wireless network is strong and people can get strong cell phone signals without dropped calls (along with good reception). I had not heard about blown fiber or jetted air, but it sounds like it’s yet another way for DAS to optimize your wireless network.
What a fascinating concept. It sounds like no detail is overlooked when it comes to DAS installation and make sure everything works well to ensure clear calls, no dropped calls, etc. in your facility. I liked the air hockey table analogy because it helped me understand this perfectly. On a side note, does anyone know the percentage of cell phone boosters compared to DAS?