Abstract: An optically amplified gain control circuit is disclosed, which comprises an optically amplifying medium for amplifying an optical signal, a exciting light coupler for combining exciting light with the optical signal optically amplified by the optically amplifying medium, and a control circuit for controlling an output of the exciting light combined with the optical signal by the exciting light coupler, wherein the optical signal to be amplified is composed of a main signal, an SV signal, and a tone signal which are multiplexed, and wherein the control circuit controls the output of the exciting light corresponding to the tone signal on the preceding stage of the optically amplifying medium and the tone signal on the next stage of the optically amplifying medium so as to control the amplification of the optical signal by the optically amplifying medium.

Abstract: Disclosed is an optical amplifier, comprising: at least one optically amplifying unit having: a forward excitation light source for generating a forward excitation light; a forward excitation light coupler for coupling the forward excitation light with an input optical signal; an optically amplifying medium for amplifying the input optical signal combined with the forward excitation light; a backward excitation light source for generating a backward excitation light; a backward excitation light coupler for coupling the backward excitation light with the amplified optical signal; a first controller for controlling the forward excitation light source to generate the forward excitation light with a power up to a maximum power thereof; and a second controller for controlling the backward excitation light source to generate the backward excitation light in such a way that the backward excitation light compensates gain deficiency as compared with a desired gain of the optical amplifier.

Abstract: In a light amplifier and a light amplifying method, a dummy light (saturated light) source 40 emits dummy light, a directional coupler 11 composes the dummy light with a light signal, and the composite light of the light signal and the dummy light is split into two parts to output a part thereof to a directional coupler 12. One part of the composite light (the light signal and the dummy light) output from the directional coupler 12 is amplified by a light amplifying portion 20, and the dummy light is removed from the composite light thus amplified by a dummy light removing filter 31. A dummy light (saturated light) source control circuit 50 controls the dummy light source 40 so that the light output of the dummy light source 40 is equal to predetermined light output. With this construction, lack of light input power due to reduction in the number of channels of the light signal of a transmission path is compensated by dummy light, thereby preventing over power of the signal light of the remaining wavelength.

Abstract: Disclosed is an optical amplifier, comprising: at least one optically amplifying unit having: a forward excitation light source for generating a forward excitation light; a forward excitation light coupler for coupling the forward excitation light with an input optical signal; an optically amplifying medium for amplifying the input optical signal combined with the forward excitation light; a backward excitation light source for generating a backward excitation light; a backward excitation light coupler for coupling the backward excitation light with the amplified optical signal; a first controller for controlling the forward excitation light source to generate the forward excitation light with a power up to a maximum power thereof; and a second controller for controlling the backward excitation light source to generate the backward excitation light in such a way that the backward excitation light compensates gain deficiency as compared with a desired gain of the optical amplifier.

Abstract: In a light amplifier and a light amplifying method, a dummy light (saturated light) source 40 emits dummy light, a directional coupler 11 composes the dummy light with a light signal, and the composite light of the light signal and the dummy light is split into two parts to output a part thereof to a directional coupler 12. One part of the composite light (the light signal and the dummy light) output from the directional coupler 12 is amplified by a light amplifying portion 20, and the dummy light is removed from the composite light thus amplified by a dummy light removing filter 31. A dummy light (saturated light) source control circuit 50 controls the dummy light source 40 so that the light output of the dummy light source 40 is equal to predetermined light output. With this construction, lack of light input power due to reduction in the number of channels of the light signal of a transmission path is compensated by dummy light, thereby preventing over power of the signal light of the remaining wavelength.

Abstract: An optically amplified gain control circuit is disclosed, which comprises an optically amplifying medium for amplifying an optical signal, a exciting light coupler for combining exciting light with the optical signal optically amplified by the optically amplifying medium, and a control circuit for controlling an output of the exciting light combined with the optical signal by the exciting light coupler, wherein the optical signal to be amplified is composed of a main signal, an SV signal, and a tone signal which are multiplexed, and wherein the control circuit controls the output of the exciting light corresponding to the tone signal on the preceding stage of the optically amplifying medium and the tone signal on the next stage of the optically amplifying medium so as to control the amplification of the optical signal by the optically amplifying medium.