The present invention provides an optical signal transmission apparatus for carrying out bi-directional light transmission. The optical signal transmission apparatus includes: a light sending module, for sending an optical main-signal having at least one data width, and receiving an optical sub-signal including a control signal; a light receiving module for receiving the optical main-signal and sending the optical sub-signal; and an optical cable for connecting between the light sending module and the light receiving module, wherein the light sending module comprises a control component which controls the output of the optical main-signal such that the output of the optical main-signal is stopped, when the optical sub-signal, which includes as data the reception status of the optical main-signal, is not being received, or when the reception status of the optical main-signal is indicating non-receiving.