The A410 singlemode attenuator uses controlled bending of the fiber-optic cable to insert 1- to 5-dB loss in a patchcord without causing reflections that may affect high-speed transmission systems, according to the manufacturer. The device can be used to test systems for margin or temporarily adjust receiver power during system setup to prevent
overloads. After setup, it is generally replaced with a permanent fixed attenuator. It works with any 3-mm jacketed patchcord and the attenuation can be checked with a standard fiber-optic power meter. The unit sells for $39.