Abstract
A reflection-type optical variable attenuator comprises: a reflector for reflecting two incident polarized light from a beam displacer back to the beam displacer; a polarization rotation means placed between the beam displacer and the reflector for generating polarization rotation for the light passing through, so as to adjust the amount of attenuation of the output light by controlling the rotation angle of the polarization; and a high density wavelength multiplexing filter is disposed before the beam displacer to form an attenuator with multiplexing function. By serially connecting a plurality of such attenuators and a light circulator and using a current control means to control the amount of attenuation in each attenuator, it is then possible to obtain a high density wavelength multiplexing gain control system.