Fiber Optic Challenges From a Campus Perspective

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Episode 10: Fiber Optic Closure Specs Explained…

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As with all local area networks dating back to the 1980s, the use of legacy multimode systems has evolved to high-speed Dense Wavelength Division Multiplexing (DWDM single-mode) optical systems. Each of these need to be installed and maintained per stringent requirements which the Network Architecture and Design group performs, administers, and updates, as needed. For physical plant design, installation, and maintenance, the Communications Infrastructure group handles these roles. These groups design, create, build, manage, and document, all fiber circuits as needed.

DWDM equipment being tested by UW staff member (Courtesy of University of Washington)

Due to the size of the campus and high bandwidth needs, the university contracts out duct and cable installations along with related splicing, testing, and emergency restorations. This requires making sure that approved contractors are used, and that their work is in compliance with the university’s practices and documentation requirements.

The UW fiber systems includes a ring around Lake Washington of which they own 2 of the fibers. Due to the low fiber count, this requires the use of DWDM technology to maximize the number of wavelengths as required, which is currently 45. Nodes are located at the University of Washington’s ADS building, the branch campus in Bothell, Bellevue City Hall, the RCECC building in Renton, VCOM in Auburn, King County Data Center within the Sabey Complex, and the UW Router Room within the Westin Building — all of which are secured with locked cabinets.

Other installations throughout the system includes legacy cables with up to 96 single-mode fibers, newer cables with higher count 144, and 288 single-mode fibers. Internally, the use of multimode OM 3 and 4 fibers are used with LC and MTP connectors while most single-mode terminations are with SC/PC and LC connections. While most of the new installations and upgrades use single-mode fibers there is an extensive network of legacy OM-1 multimode fibers still in place. In the data centers these are gradually being upgraded to the higher bandwidth laser optimized OM 3 and OM 4 multimode fibers.

Challenges of operating and maintaining an extensive wide area network along with enterprise operations means a blend of fiber types, manufacturers, and connector styles and polishes. The migration to standardize is an ongoing challenge but one that is being addressed by the implementation of their practices and procedure documentation. It also requires an inventory of test equipment for testing both single-mode and multimode fiber equipment and spans.

UW Network Map (Courtesy University of Washington)

Even with the use of approved contractors, the UW teams must make sure that details including installations are correctly installed with complete documentation and fiber-routing information.

Test requirements and associated documentation is essential, and includes attenuation measurements, OTDR records including splice and distance data, and bi-directional 1310/1550 nm measurements.

Single-mode fiber characterization includes optical return loss (ORL), return loss (RL) chromatic and polarization values for the spans. Test results are provided by contractors on compact disks. Once all measurements are in compliance then the project is approved.

Cable management with a blend of multimode and single-mode terminations. (Courtesy University of Washington)

The University of Washington’s network also provides services throughout Washington state but also to universities in Alaska, Hawaii, and Montana. Like all networks, history repeats itself, and outages can and will occur. While all network designers try to minimize outages through careful planning, outages still occur. Recently one was caused by a construction project involving a contractor boring off site which caused damaged to multiple cables. Fortunately, while the system was ring-protected, if a second cut occurred this would have dropped and isolated thousands of users.

The staff at the UW needs to maintain their network, and provide immediate response for any degradation and or failure. Maintaining staff knowledge of technology, plus having the proper equipment to locate, identify, and resolve, problems is essential. Unlike telephone and cable television operators, which use only single-mode fibers, the UW, like many campuses and organizations, operate a blend of multimode and single-mode systems.

Other types of network that have a blend of fiber types are research facilities, military organizations, hospitals, and factories with massive automation operations. It is easy to overlook these types of organizations but their fiber networks can be quite extensive, and they have implemented fiber optic systems for decades.

This requires additional expertise, training, and equipment. One challenge many network users have from decades of fiber installations is transitioning from hard copy test reports and even floppy disks. Key is to have up-to-date documentation on all fiber links and systems, from legacy multimode to high-speed DWDM single-mode systems.

Keeping pace with technology while addressing bandwidth challenges are a day-to-day challenge for the University of Washington, which only a few decades ago, operating at high speeds at the time of 4 and 10 Mb/s are today transmitting at 100 Gb/s — with no let-up in sight!