Abstract: An optical transmission module, an optical data link, and an optical transmission system achieving a simplified matching circuit and a bias circuit with higher power efficiency. An optical transmission module including a first line, one end of which is connected to a high-frequency signal input unit and the other end of which is connected to a termination unit; a second line, one end of which is connected to an electrical-optical conversion unit and the other end of which is connected to a power supply connection unit of a DC power supply; and a coupling portion at which the first line is electromagnetically coupled to the second line. In the second line, a signal input from the high-frequency signal input unit is propagated only to the electrical-optical conversion unit due to an attenuation relationship between coupling characteristics and isolation characteristics of the first line and the second line.