| 摘要 |
PURPOSE:To improve an S/N ratio by inputting a superhigh-speed optical phase modulating signal transmitted by an optical fiber, to a low Q laser synchronizing oscillator, inputting a light-emitted output optical wave and the superhigh-speed optical phase modulating signal to a photodetector, superposing and detecting them, and fetching a demodulating signal through an integrator. CONSTITUTION:A superhigh-speed optical phase modulated wave signal sent from an optical fiber 1 is inputted to a photodetector 3 from an end face (a) cut at 45 deg. of the optical fiber 1. At the same time, a low Q laser synchronizing oscillator 2 is adjusted to a state that it is immediate before oscillation. A receiving optical wave transfer function Y is adjusted in a complex conjugate relation to an inputted superhigh-speed optical phase modulated wave S. Accordingly, when the superhigh-speed optical phase modulated wave S is inputted to the low Q laser synchronizing oscillator 2, light is emitted under the condition of the optical wave transfer function Y, reflected by the end face (a) of the optical fiber 1, and inputted to the photodetector 3. The photodetector 3 generates a demodulating signal component yS basing on a theory of a matched filter by a multiplier. By fetching this demodulating signal through an integrator 4 of an LPF characteristic, an S/N ratio is improved. |
