| 摘要 |
PURPOSE:To transmit a high-frequency analog signal of a band over the VHF band with high quality and high stability by converting irradiated light of a semiconductor laser into parallel light, reflecting it on a reflecting plate, collecting the light with a lens and transmitting the light through a multi-mode fiber. CONSTITUTION:An external resonator of a semiconductor laser 23 is constituted by converting the front direction light of the semiconductor laser 23 into parallel light by a lens 30, reflecting it on the reflection plate 29, collecting the light with a lens 30, returning it to the oscillation region of the laser 23 in the same phase as the irradiated light. Light is driven at a drive section 22 in the semiconductor laser device with a bias current having a higher level than the threshold value of the semiconductor laser and a signal current proportional to an analog signal inputted from a terminal 20 and the light is subjected to light intensity modulation. The rear direction light of the laser 23 subjected to light intensity modulation is collected by a lens system 24, made incident on the multi-mode fiber 25, transmitted through the fiber 25, enters a photo diode 26, where the light is converted into an electric signal, amplified (27) and outputted. Thus, the S/N, deterioration in the distortion and its fluctuation due to the prolonged fiber length are eliminated and highly stable and long range transmission is attained. |
