PURPOSE: To provide the optical signal transmitter with less signal quality deterioration in which mounting labor and time is considerably saved without need of relay amplification or with very small numbers.

CONSTITUTION: A 1st optical signal transmitter 1 is used for the music service of stereo broadcast such as a passenger aircraft. A carrier signal of a prescribed frequency is frequency-modulated by an object signal such as a music signal in a modulator 10 and the modulated signal is sent through a coaxial cable 12 whose characteristic impedance is R(ohms) via an amplifier 11 whose output impedance is R(ohms) and inputted sequentially to m-sets of high input impedance light emitting circuits 13 connecting to the coaxial cable 12, the light emitting circuits 13 convert the modulated signal into a light and it is sent to a receiver.