PURPOSE: To send plural signals by providing a transmission section and a reception section to the system and providing a dispersion means dispersing light for each prescribed wavelength band and plural units of light receiving element sections receiving an optical signal of each wavelength band subject to dispersion to the reception section.

CONSTITUTION: When a signal S1 from an equipment A is sent to an equipment B and a signal S2 from the equipment B is sent to the equipment A, the signal is set as shown in Figure. That is, the signal S1 from a signal source 11 is given to a transmission reception unit 40, in which the signal is converted into an optical signal whose wavelength is λ1 and sent to a transmission reception unit 50 through an optical fiber 20, received by a light receiving element section via a dispersion means and extracted as the signal S1. On the other hand, the signal S2 from a signal source I2 is given to a transmission reception unit 50, in which the signal is converted into an optical signal whose wavelength is λ2 and sent to a transmission reception unit 40 through the optical fiber 20, received by a light receiving element section via a dispersion means and extracted as the signal S2. Furthermore, it is possible to send plural data in 2-way and the wavelength of the optical signals sent in the fiber is made different.