An arrangement for controlling the transmission of a light signal is disclosed. The arrangement includes a first fiber optic line for transmitting the light signal and a light receiving unit operatively coupled to the first fiber optic line so that the light signal is received by the light receiving unit. The light receiving unit is operative to refract the light signal so that the light signal is substantially prevented from being transmitted through the light receiving unit if an intensity level of the light signal has a predetermined relationship with an intensity threshold level.