Is after-installation fiber damage acceptable?
Did you find any damaged fibers after your installation was complete?
It is reasonable to install hundreds of miles of ADSS or OPGW without one damaged fiber (let alone broken fibers). These cables contain either Kevlar (ADSS) or steel (OPGW) and are very strong -- theoretically, you could tow a trailer with this stuff and never damage a fiber.
We're defining "damaged" here as a step increase in attenuation of at least 0.1 dB.
While a step increase of just 0.1 dB is an insignificant amount of loss, it's an indication that something is pinching or stressing the fiber. That small step increase could easily become a break with a change in temperature or cable loading, depending on the cause of the step.
Furthermore, from our failure analysis consulting work, we've seen that certain types of installation damage can leave no external marks on the cable and yet still significantly damage long runs of the plastic (ADSS) or metal (OPGW) buffer tubes that protect the fibers inside the cable. Small changes in temperature and cable loading can cause the appearance (or disappearance) of attenuation steps all along these damaged stretches -- if you have an 'event' on one fiber, it may be a matter of time before you see more point defects on other fibers.
Some utilities and installation contractors have become used to a few damaged fibers during their installations and just shrug it off as "something that happens". That's absolutely wrong! Competent crews installing fiber cable under attentive supervision and following proper procedures routinely install fiber for years with no damaged fibers.
Depending on the circumstances behind a fiber fault, we may recommend an entire reel be replaced even if there's only a fault in one location.
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