How do you measure whatchamacallit?

The lead story of this special edition of Lightwave mentions a breakfast held by OFS Fitel at the most recent Optical Fiber Communications Conference. There, representatives of the fiber and component manufacturer lamented that the company was having a hard time determining how much fiber it should plan to manufacture, because their estimates of how quickly carriers will run out of capacity were distinctly more aggressive than those of the financial community. One problem they encountered when they tried to rationalize their forecasts with those of Wall Street analysts was that there didn't seem to be any consistency on just what constituted "unused capacity."

Before you can determine if capacity is unused, you have to agree on how you measure capacity in the first place. Is it the amount of lit fiber? The amount of fiber lit and unlit? Do you count fiber used for protection? How about fiber that may be reaching obsolescence?

Then, of course, there's DWDM. Do you count the number of channels currently on each fiber or the numbers that fiber could carry? What if you have systems that could transmit at 10 Gbits/sec but are only operating at 2.5? The question of protection channels appears here as well. And if a carrier has engineered its network to handle peak loads, is capacity "unused" when traffic isn't at peak?

The possible permutations can induce headaches in even the most diligent analyst. Clearly, for the sake of rational discussion between industry and the financial community-not to mention among carriers and their clients and suppliers-some agreement must be reached on what constitutes capacity and whether it is "in use."

The folks at OFS Fitel have attempted to get this ball rolling by offering definitions of three aspects of capacity:

  • Active capacity utilization: total bandwidth demand divided by the sum of capacity of active channels.
  • Channel slot utilization: active channel cards divided by total channel slots installed.
  • Fiber utilization: lit fibers divided by total installed fibers.

The combination of these three factors should provide a ballpark figure for most networks. But is it good enough? I'd be interested in hearing from readers about this question. Until we're all speaking the same language, vendors, carriers, and financiers will continue to talk in circles.

Stephen M. Hardy
Editorial Director and Associate Publisher

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