| 摘要 |
PURPOSE:To amplify the light with a small noise and a high amplification factor by specifying the coefficient of linear expansion of secondary coating materials of an optical fiber to which a laser active material is added and cooling them to a very low temperature. CONSTITUTION:Signal light is amplified in a single mode optical fiber which is cooled by a cooling thermostat 11 and to which Er is added, and this light passes a condenser lens 3, an isolator 20, and a cut filter 16 and is received by a photodetector 14. At this time, a silicone resin is used as primary coating materials of the optical fiber 6, and thermotropic liquid crystal high polymer materials where macromolecular chains are oriented by extrusion or fluid draw ing are used as secondary coating materials. Since the coefficient of linear expansion of this liquid crystal is reduced in accordance with orientation, it is set to + or -10<-5> <0>C<-1> so that it is approximated to the coefficient of linear expan sion of the optical fiber. Consequently, the occurrence of the microbending loss due to the difference of coefficient of linear expansion is prevented at a very low temperature <=-60 deg.C. Thus, an optical fiber amplifier of high perfor mance where the noise is considerably reduced is obtained. |
