OPTICAL COMMUNICATION SYSTEM

摘要

PURPOSE: To perform the external modulation of a plane of polarization to eliminate the null point by using a fiber ring laser as a light source and transmitting a polarized signal. CONSTITUTION: When the external modulation is applied to a plane of polarization, a state where a signal is maximized is set by means of a fiber ring laser light source 1. However, the light emitted from the light source 1 is not perfectly non-polarized and includes a polarization component that satisfies a prescribed expression. Therefore, the signal is sometimes minimized. Nevertheless, the strength difference can be extremely reduced down to 1dB between the maximum and minimum signal levels with use of the light source 1. Thus the effect that is given to the modulation of the plane of polarization due to the presence of a null point can be considerably reduced in comparison with the use of a laser diode. As a result, no problem is caused for the plane of polarization as long as a fiber ring laser is used as a light source in an optical communication system that performs the external modulation of the plane of polarization.