| 摘要 |
PURPOSE:To obtain the optical heterodyne communication system which can make stable signal reception with a high sensitivity by using a negative frequency component suppression type optical light receiving device and subjecting one of the two outputs thereof to a frequency conversion and then executing multiplication. CONSTITUTION:The output of an optical signal transmitting device 1 is bisected. The one light is modulated by an optical modulator 2 and the other light receives the conversion of the frequency of light by an optical frequency converter 3. The light subjected to the frequency conversion by this optical frequency converter 3 is multiplexed with the light modulated by an optical coupler 42 and transmits in an optical fiber 5, from which the light is multiplexed with the light from a local emitting light source 6 by an optical coupler 43. The multiplexed light is subjected to the heterodyne detection by the image rejection type optical light receiving device 14 which is a part of the optical light receiving device 100. Namely, the signal 16 is multiplied by the output of the oscillator 18 and the output of this multiplier 17 is passed through a low-pass filter 19. This output and the signal 15 are multiplied by a multiplier 11 and the output thereof is passed through a low-pass filter 12, by which a base band signal 13 is obtd. The phase noises of the light of the optical signal transmitting device 1 and the local emitting light source 6 are offset by the receiving device 100 and the stable optical light receiving device having the high sensitivity is obtd. |
