Patent ID: 6323973
Filing Date: 2001-11-27
Classification: H04B

Abstract:
A method comprising:generating a light signal;amplifying the light signal to a higher output light power;branching the amplified light signal via first and second branch ports into first and second amplified light signals, respectively, the first amplified light signal being sent to a first transmission path through a first output port connected to an end of the first transmission path, the second amplified light signal being sent to a second transmission path through a second output port connected to an end of the second transmission path;judging if an abnormality has occurred in the transmission path, based on a rising signal which passes through said first output port in a direction opposite the first amplified light signal, and judging if an abnormality has occurred in the second transmission path based on a rising signal which passes through the second output port in a direction opposite to the second amplified light signal; andshutting off the first amplified light signal if said judging judges that an abnormality has occurred in the first transmission path, and shutting off the second amplified light signal if said judging judges that an abnormality has occurred in the second transmission path.