| 摘要 |
PURPOSE:To reduce the polarization dependence of an optical amplification and relay system by providing a polarization modulation means wherein an optical signal which is output from a light source is modulated so as to maintain a linear polarization and the polarization state of the modulated optical signal is changed periodically up to an orthogonal state. CONSTITUTION:An optical signal which is output from a transmission light source 9 by a linear polarization inside a polarization dependence-reduced optical transmission device A at a transmission terminal station is coupled to an external modulator 10 which converts it into an optical data signal by a polarization-preserving optical fiber 12 so as to maintain a polarization state. In addition, it is coupled, by the polarization-preserving optical fiber 12, to a polarization modulator 11 as a polarization modulation means which changes the polarization state of the optical signal up to an orthogonal state at a cycle of 1msec. Them, an optical signal output S1 from the optical transmission device A is amplified, relayed and transmitted by an optical fiber 7 for transmission and by an optical fiber amplifier 8, and an optical signal S2 is input to an optical reception device B. Thereby, even when the polarization state of the optical signal of the light source 9 is changed, the S/N of the optical signal can be made definite. |
