Outside Plant (OSP)

Telephone companies, CATV and the Internet all use lots of fiber optics, virtually all of which is singlemode fiber and most of which is outside buildings. It hangs from poles, is buried underground, pulled through conduit or is even submerged underwater. Most of it goes relatively long distances, from a few hundred feet to hundreds of miles.

Outside plant cables often have very high fiber counts, up to 288 fibers or more. Cable designs are optimized for the application: cables in conduit for pulling tension and resisting moisture, buried cables for resisting moisture and rodent damage, aerial for continuous tension and extreme weather and undersea for resisting moisture penetration. Installation requires special equipment like pullers or plows, and even trailers to carry giant spools of cable.

Long distances mean cables are spliced together, since cables are not manufactured in lengths longer than about 4-5 km (2.5-3 miles), and most splices are by fusion splicing. Connectors (generally SC or LC styles) on factory made pigtails are spliced onto the end of the cable. After installation, every fiber and every splice is tested with an OTDR.

If this sounds expensive, you are right! The installer usually has a temperature controlled van or trailer for splicing and/or a bucket truck. Investments in fusion splicers, OTDRs and other equipment can be quite expensive.

Most outside plant telephone installs are done by the telco themselves, while a small number of large, specialized installers do CATV, utility and municipal work.

November 30, 2011

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