| 摘要 |
PURPOSE:To perform easy and stable optical coherent FSK (frequency shift keying) transmission which is free from the modulating speed by providing an optical switch which switches the output rays of light of two lasers which output the rays of light having fixed wavelengths slightly different from each other in accordance with modulated signals. CONSTITUTION:Lasers 10 and 11 are maintained at a fixed temperature by means of a temperature controller 12 and driven with fixed driving currents by means of laser drive circuits 13 and 14. In addition, the frequencies of the lasers 10 and 11 are respectively maintained at lambda1 and lambda2. An optical switch 15 can output one of the output rays of light of the lasers 10 and 11 after switching in accordance with modulated signals. Accordingly, optical signals outputted from the switch 15 and made incident on an optical fiber 16 become optical frequency shift keying (FSK) signals which shift between the frequencies lambda1 and lambda2 in accordance with the modulated signals. Therefore, stable optical coherent FSK transmission can be performed with a simple circuit, since the transmission characteristics are free from the modulating speed and no complicated control is required. |
