Optical attenuators are used normally at optical receivers to adjust for the optimum optical input power level to ensure proper operating parameters of the receiver. Both fixed (connectorized) attenuator and variable (step) attenuators are available.
Step attenuators like the Olson OTOA-1000 operate on the principle of putting a “microbend” in the optical cable allowing some light to escape the cladding, resulting in some light loss or attenuation. The OTOT-1000 has a combination of 1, 2, and 4 dB loops that when combined, can provide from 1 to 7 dB of attenuation in standard 3 mm singlemode optical cable at 1310 nm. Other cable or wavelengths may result in different attenuation characteristics.