This provides an optically transmitting apparatus, an optically transmitting system and an optically transmitting method. This receives an optical signal which is configured in accordance with any one frame format among a plurality of frame formats and includes at least a clock signal and a data signal, and performs an optical-electric/electric-optical conversion on the received optical signal, and extracts the clock signal and the data signal, which correspond to the frame format, from the optical-electric converted signal. This correlates and stores an idle code indicative of a block where the actual data is not communicated and the frame format, reads the idle code from the extracted data signal, identifies the frame format corresponding to the read idle code, and executes a transmitting process in accordance with the identified frame format.