| 摘要 |
PURPOSE:To constitute a heterodyne optical communication system at low cost by using one light beam for local oscillation and the other light beam for signal modulation. CONSTITUTION:A zeeman laser 1 outputs clockwise polarized wave light (wavelength: lambda1) and counterclockwise polarized wave light (wavelength: lambda2). Those light beams are passed through a lambda/4 plate (lambda: wavelength) to obtain two orthogonal linear polarized waves. Then, a polarizer 3 is used to separate the two polarized waves; one polarized light is inputted to an external modulator 4 through a mirror 6 to impose phase or frequency modulation. The other polarized light is passed through a mirror 6' and multiplexed by a back mirror 7' with the light modulated by the external modulator 4, and the resulting light is incident on a single-mode constant polarization fiber 5 as a transmission line. The light projected from the single-mode constant polarization fiber 5 is split again by an analyzer 3, the unmodulated polarized light have the 90 deg. polarization direction rotated by a lambda/2 plate 8 so that the plane of polarization is matched with that of the modulated polarized light, and the intensity is increased by an optical amplifier 9; and the light is multiplexed by the half-mirror 7' with the modulated polarized light and the resulting light is incident on a photodetector 10 to perform heterodyne detection. |
