Most fiber-optic attenuators exhibit a relatively high return loss (at least several dozens of decibels), i.e., there is not much light which is reflected back into the input fiber. For some sensitive applications, e.g.
Single mode fiber, short as SMF, is a fiber cable that only allows one mode of light to transmit. Typically, this fiber includes a small light-carrying core of about 9µm diameter. These feature a small modal disp.