| 摘要 |
PURPOSE:To immediately attain restoration when a light emitting element breaks down by controlling a polarization beam splitter which selectively allows a laser beam from plural laser elements to pass through or reflect, and switching the light emitting state of the laser elements. CONSTITUTION:A polarization beam splitter 22 of an exciting light source 12 selectively allows the laser beam from each semiconductor laser 16a and 16b to pass through or reflect according to the polarizing direction of the laser beam. Moreover, control circuits 24 and 24b for driving emission are connected to each semiconductor laser 16a and 16b, and when one semiconductor laser 16a breaks down and doesn't emit a light, a detection signal is outputted from the control circuit 24a, and the other control circuit 24b allows the semiconductor laser 16b to emit the light in response to the detection signal. The laser beam is allowed to pass through a lens 20b, reflected by the polarization splitter 22, guided through a lens 20c to an optical fiber 26, and guided through an optical coupler 14 to an optical fiber amplifying element 10. At that time, a time lag can be reduced, and a signal light can be immediately and normally amplified. |
