Something New to Worry About

摘要

RECENTLY, I BECAME AWARE OF A NEW SAFETY ISSUE that may affect fiber installations and cut fiber optic cable repair. It was brought to my attention by a field technician who had been splicing broken long-haul outside plant (OSP) fiber optic cables. He worried that fibers with fiber amplifiers in the link may pose a threat to eye safety. What is a fiber amplifier? Many long-haul links today use two technologies to enhance the information-carrying capacity of the fiber and reduce costs, wavelength division multiplexing (WDM) and fiber amplifiers. WDM technology transmits multiple signals at different wavelengths down the same fiber simultaneously. There is no crosstalk with light, so it is a convenient way to enhance a network's bandwidth. Some carriers simply add more wavelengths to the fibers instead of lighting up dark fibers to add capacity. More wavelengths mean more power transmitted through the fiber, so the power exiting the fiber at the far end is higher than systems using only one wavelength. Although standards exist for more than 100 wavelengths, often only a few of those are actually being used in a link. However, that still means that the optical power from the fiber will be higher than if only one wavelength is used.