Attenuators are passive components used to limit the optical power in a link. They can also be used to improve the return loss. The attenuating element is a doped fibre. Attenuators are available in two versions: Plug-in adapter type (female/male) and in-line (patchcord ). The latter is available with or without connectors. The attenuator to connect to a fibre (in-line) is fitted in a termination box or panel.