Abstract: Disclosed is a variable optical attenuator comprising: a transmitting fiber for transmitting light; a receiving fiber for receiving light from the transmitting fiber; an attenuating module provided between the transmitting and receiving fibers for attenuating light and having a transmitting unit, an attenuating unit and a receiving unit; an actuator for driving the attenuating unit; and a substrate supporting the transmitting fiber, the receiving fiber, the attenuating module and the actuator. The attenuating unit is driven offset in a lateral or angular motion to attenuate light. The transmitting, attenuating and receiving units of the attenuating module are formed into one module to obtain simple relative alignment of optical axes.

Abstract: A wet-pipe sprinkler system, method of supplying water to the system, and method of dealing with a leakage of the system are provided, wherein the wet-pipe sprinkler system includes a sprinkler head; a plurality of interconnected pipes for supplying water to the sprinkler head; at least one water supply connected to one end of the pipes; an electric main valve for controlling inflow of water to the pipes; an electric drain valve to drain water from the pipes; a first electrical control circuit in a central control studio which outputs a drain valve opening signal to the electric drain valve and a main valve closing signal to the electric main valve when a leakage is detected, thereby blocking the water from entering the pipes and draining the water from the pipes. Accordingly, a leak may be dealt with promptly, thereby minimizing damage caused by the leakage.