A fiber in a haystack, Databases are becoming critical to locating fiber optics in the outside plant. The challenge is making sure the right people have access

It's 1997 and more than 35 million fiber miles have been deployed worldwide. But just where is the fiber and how is it all interconnected? The need for easy access to this information has resulted in a proliferation of fiber database software. The advantages and disadvantages of the different types of available databases depend on the kind of information stored in a fiber optic outside plant database and on who needs the data on a regular basis.

Changing colors There are two different sets of data in the fiber optic OSP: physical plant routing and placement, and fiber routing within the cables and splices. Most fiber optic OSP databases focus on fiber routing.

Fiber is identified in a cable by the color of the fiber as well as the color of the tube or bundle. There are typically 12 color-coded fibers and as many as 24 color-coded tubes, bundles, slots or ribbons.

When fiber cables were only deployed point-to-point, splicing fibers together was straightforward. Each fiber was spliced to the identical fiber in the next cable.

In recent years fiber has been deployed in loop, feeder and distribution applications. In these applications, the number of fibers in one cable does not usually coincide with the number of fibers in the next. Typically, two or more cables are spliced into one cable. In that case, duplicating fiber identifiers in the smaller count cables is inevitable, as is splicing one color fiber to another color in a different cable.

As traffic is routed from one cable to the next, the fiber and tube through which the traffic is carried have changing identifiers. A 48-fiber cable may leave a central office and be split into two 24-fiber cables at the first splice point. The fiber identification in the two 24-fiber cables is identical.

Typically, the first 24 fibers in the 48-fiber cable would match up to the fibers in one of the two 24-fiber cables. The problem occurs with the splicing of the last 24 fibers from the original cable to the 24 fibers in the second of the two smaller cables. The second set of 24 fibers in the 48-fiber cable are not identified in the same manner as in the second 24-fiber cable. Although the fiber colors are maintained, there is a mismatch in tube color-a relatively simple mismatch.

As cables and fibers are spliced hundreds of time, however, it's not hard to imagine the complexity of color combinations. Often, both fiber and tube identification eventually are changed across a single transmission path.

It must be here somewhere Another complicating factor-one that is often overlooked-has to do with the physical placement of cable splice enclosures, excess cable and other physical layer components. Where the plant is actually placed often has little similarity to the engineering layout issued to the field.

The OSP is a dynamic environment completely out of any person's or company's individual control. It sometimes seems that the design supplied by OSP engineering always places splice enclosures under concrete or in a creek-or that the planned cable route cuts through the corners of fences.

Construction crews invariably change some of the designed locations of the splice enclosures for practical considerations. The problem is in documenting these changes so that maintenance organizations can find them at a later time.

It is important to know the actual location of splice enclosures and cable routing to accommodate other companies that will want to place cable or pipe in the same right-of-way-and to support future OSP upgrades and emergency restoration.

Most recently, global positioning systems have been used to specify the physical location of OSP components.

GPS coordinates are an excellent option. All other reference points-including roads, trees, railroads and poles-will change in time. And although marker poles are an obvious choice, they are easy targets for vandals.

Having fiber routing data in an accurate, easy-to-access format is important for fiber reconfiguration or emergency restoration. For reconfiguration, it is of the utmost importance that the OSP technician know which fiber has live traffic and which is available for new traffic. In an emergency restoration, minutes are money. The crew needs to know in what order fibers should be spliced to restore service to the most critical customers first.

As mentioned earlier, however, the fiber and bundle identification may have very little similarity to the identification of the fiber with the same traffic in the CO. A fiber optic database is critical to properly identifying specific fibers as well as the precise location of the fiber optic OSP.

Departmental roles A fiber transmission system is usually designed by a transmission engineering organization. That organization is concerned with link loss budget, attenuation, number of splices, chromatic dispersion and any other transmission-related properties. Many engineering design groups only see the OSP as a line on a schematic drawing connecting transmission and switching equipment.

Because the transmission engineering staff members typically have computer and software expertise, they are often assigned to maintain the database. Unfortunately, these are not typically the people who need to constantly access the data contained in the OSP database.

It is the OSP engineering and construction organization that designs the actual routing of cable and placement of equipment such as splice enclosures and excess cable. Although the transmission engineering organization is usually the best suited for database system management, the OSP engineering group is the better organization to input the initial data into the database.

There are also times when information contained in these databases is of crucial importance to OSP engineers. Knowing the placement of cable, location of enclosures and location of the rights of way are obviously important in re-engineering old plant or placing new cable.

The group that is most in need of the information contained in a fiber optic OSP database, however, is the OSP maintenance organization. These are the people responsible for keeping the OSP up and running for its budgeted 20-year lifetime and for keeping the fiber optic system operational through rain, sleet and snow. Unfortunately, they are frequently the least computer-literate.

A distributed database To ensure that changes are funneled through a single point, most of the database products available today are centralized. The problem with this approach is that the database is either unavailable or difficult to access by those who need it most-the OSP maintenance organizations (Table 1).

A distributed, easily accessible database system would be ideal for getting the data where it belongs: to the people in the trenches. The issue here is the cost of maintaining duplicate databases and providing simple access to the requested data.

Of utmost importance is a database system that stores the data in a distributed system but is maintained from a centralized point (Figure 1). The centralized database server should be updated and maintained by a restricted number of personnel, and a system should be in place that allows OSP maintenance and construction personnel to forward physical plant changes in writing to the database maintenance organization.

Once the new data is entered, the distributed data centers should be automatically updated by the centralized server.

The distributed databases should be easily accessible for data queries by the field personnel associated with each coverage area. The centralized server should also be accessible by "clients" in order to access information companywide. The information should be presented in an graphical format on a geographic-based display.

The most effective preventive maintenance is always performed on the physical layer of any system. As consumer demands for bandwidth due to Internet and broadband data increase, fiber will dominate the physical layer of the telecom OSP. It is imperative that we keep accurate records of this fiber infrastructure.

John Chamberlain is General Manager for Norscan in Conover, N.C.