An optical repeater used in an optical submarine cable system is laid on the seabed, and thus, is required to have a small size and low power consumption. Meanwhile, in order to make a capacity of the optical submarine cable system large, an optical repeater capable of amplifying L-band signal light as well as widely used C-band signal light has been studied.
FIG. 6 is a block diagram illustrating a configuration example of an optical repeater 900 related to the present invention. The optical repeater 900 is used in an optical submarine cable system. The optical repeater 900 includes a C-band optical amplifier 91 and an L-band optical amplifier 92. In the present description, the C-band designates a wavelength band of approximately 1530 nm to 1565 nm, and the L-band designates a wavelength band of approximately 1570 nm to 1610 nm.
The C-band optical amplifier 91 includes a control circuit 911, an excitation light source 912, and optical amplification media 913 and 923. The optical amplification media 913 and 923 amplify C-band signal light, with excitation light generated by the excitation light source 912. In order to amplify C-band signal light, four laser diodes (LDs) of a wavelength band of 980 nm are used in the excitation light source 912.
The L-band optical amplifier 92 includes a control circuit 921, an excitation light source 922, and optical amplification media 914 and 924. The optical amplification media 914 and 924 amplify L-band signal light, with excitation light generated by the excitation light source 922. In order to amplify L-band signal light, four lasers of a wavelength band of 1480 nm are used in the excitation light sources 922. Excitation light output from the LDs included in the excitation light sources 912 and 922 excites the optical amplification media 913 and 914 through couplers and multiplexer/demultiplexers.
Signal light of a C-band and an L-band is wavelength-multiplexed and input from an up input (UP IN) in FIG. 6. The input signal light is separated into the C-band and the L-band. The signal light of the C-band is amplified by the optical amplification medium 913, and the signal light of the L-band is amplified by the optical amplification medium 914. The amplified C-band and L-band signal light is wavelength-multiplexed and output from an up output (UP OUT).
Similarly, signal light of a C-band and an L-band input from a down input (DOWN IN) in FIG. 6 is amplified by the optical amplification media 923 and 924. The signal light amplified by the optical amplification media 923 and 924 is output from a down output (DOWN OUT).
Note that in a relation to the present invention, PTLs 1 to 3 describe an optical amplifier including a plurality of optical amplification media.