Photonics Pointers

Michael Reunert

Although a lot of unused fiber sits in the ground, many links in fiber optic networks operate at or near capacity. The importance of each line has increased with the amount of traffic it carries. In many cases, "dark fibers" are no longer available for monitoring because they have been taken over by growing commercial traffic. This means that network operators must often test their fiber while it is carrying live traffic.

Multiple-wavelength optical time-domain reflectometers that test at higher out-of-band wavelengths provide valuable tools for the maintenance of fiber optic networks. They can test active networks anytime without affecting the commercial traffic. The higher wavelengths are also highly effective for spotting bends that can develop into breaks or stress- or temperature-related losses…