To a transmission line configuring a network for optical communication; an optical amplifier provided in this transmission line; or an optical transceiver, an optical transponder, or the like that performs optical communication, an optical power attenuator may be provided to adjust an optical power.
Furthermore, as the optical power attenuator, known is one of a reflective type provided with a MEMS (microelectromechanical-system) element that can control a reflection angle of a mirror that reflects a light according to an applied voltage.
The MEMS element used in the optical power attenuator of the reflective type is provided with the mirror, which is pivotably supported via a beam, and is configured to be able to adjust the reflection angle of the light by the mirror by an electrostatic force arising according to the applied voltage (see for example patent literature 1).
Furthermore, as illustrated in FIG. 5, a conventional optical power attenuator 5 is provided with a MEMS element 10 configured as above, a capillary member 22 provided to one end of a two-core optical fiber 20 for inputting/outputting a light, and a lens 30 disposed between the capillary member 22 and the MEMS element 10.
Furthermore, the lens 30 is configured as a collimating lens; it converts an incident light from an IN-side optical fiber 20i among the two-core optical fiber 20 into a collimated light (parallel light), causes this to become incident to the MEMS element 10, and causes a reflected light from the MEMS element 10 to become incident to an OUT-side optical fiber 20o in a path different from an incoming path.
Because of this, the incident light from the IN-side optical fiber 20i is attenuated according to a reflection angle of the light by a mirror in the MEMS element 10, becomes incident to the OUT-side optical fiber 20o, and is transmitted to another optical device via the OUT-side optical fiber 20o. 