January/February/March 2020 I 41
Though somewhat oversimpli-
fied, Figure 7 can be a useful over-
view in describing a blown fiber
system and its major components.
OUTSIDE PLANT
FIBER APPLICATIONS
With any optical fiber installa tion,
the most time-consuming part is
laying the fiber pathway. In an OSP
burial application, there is usually
trenching for the conduit that must
be done prior to the fiber installation.
Depending on the length of the conduit,
handholes or pull points must
be established. Prior to installing this
pathway, considerations have to be
made for the amount of the fiber
to be installed along with room for
expansion should it be needed in the
future. If multiple fibers are to be
installed, it is critical to size the conduits
correctly. Once the conduit
pathway is installed, either the
conventional cabling or blown
fiber method can be used.
In many instances, a blown fiber
system can often eliminate the need
or reduce the amount of conduit
required, along with not having to
subdivide conduits with any type of
innerduct which is commonly done
when installing fiber conventionally.
Whether using conventional cabling
or blown fiber, it shall meet NEC
and National Fire Protection Association
(NFPA) codes for cabling rating
when entering a building, and if the
outside plant fiber installed does not,
then a transition would be required.
When an outdoor rated fiber cable
enters a building, it should be terminated/
spliced, either through a wall
or flooring, to an indoor-type fiber
Steel Manufacturing Plant Site Case Study: Blown
Fiber System — OSP and Inside Building Example
Within the industrial market, the amount of equipment and production
machinery that continues to move to “smart intelligence” / “smart manufacturing”
and becoming part of the internet of things (IoT) is growing
every day. This requires advanced networks and sensors to communicate
with each other and automate. Most manufacturing plants are 24 / 7
operations and have little to no time for lengthy shutdowns. A blown
fiber infrastructure allows the installation of new and/or additional fiber
(once the initial backbone of tube cables are installed) with little to no
disruption or need for shutdowns.
This steel manufacturing facility in Michigan needed to create two
fiber optic paths to a brand-new building. Each path required 24 strands
of fiber. The two redundant fiber pathways were approximately 4,800
feet long. The plant requested comparative costs for installing 24 strands
of fiber. The fiber would be installed using a combination of cable trays
and J-hooks running through production areas inside and outside of the
buildings. A conventional 24 strand armored fiber optic cable would have
been installed directly in the cable tray or J-hooks. Comparatively, for
the blown fiber solution, tube cable with spare tubes would be installed in
the same cable tray or J-hooks, as well as creating a pathway for future
add-ons. The blown fiber pathway would utilize a 19-tube cable with
TDUs installed along the pathway at strategic locations that act as “on &
off ramps” for future needs. The blown fiber solution was approximately
30% more expensive for the initial installation. However, after requiring
just two additional runs of fiber optic cable that utilized existing spare
tubes within the tube cable vs. pulling additional conventional fiber optic
cable, the plant saw an overall cost savings using blown fiber. The installing
contractor quoted out each additional fiber cable installation using
a conventional fiber cable vs. blown fiber.
Here is an example of the cost-comparison for adding one new fiber
cable within the same pathway. 2,200 feet of conventional fiber would
be pulled through existing cable tray and/or J-hooks requiring a minimum
of four installers. Total conventional fiber installation would take
approximately three weeks with an approximate cost of $27,000.
Vs. Blown fiber solution. The contractor would simply add a new
24-strand fiber bundle utilizing one of the spare 17 tubes available. Using
the blowing equipment, the fiber bundle would be installed end-to-end
in less than 20 minutes requiring just two installers. Total installation
time was less than two days at an approximate cost of $6,700.
Finally, after just the second need to add fiber, the blown fiber solution
proved to be overall less expensive than a conventional fiber installation
and still provided 15 additional pathways for future expansion. Over
the next 3 years, the plant required over a dozen additional fiber cable
runs, all with similar savings.