A communication device including: a dummy light source for generating dummy light; a setting means for setting first and second wavelengths (λ1, λ2) being selected from wavelengths of light included in the dummy light, and first and second transmission powers being selected, according to a first communication status of the communication device, from a plurality of transmission powers set in advance, the first communication status indicating that a transmission status of the communication device is normal or abnormal; an acquiring means for acquiring light of the first wavelength (λ1) and light of the second wavelength (λ2), from the dummy light, wherein the light of the first wavelength (λ1) and the light of the second wavelength (λ2) do not overlap each other on a time axis; an adjustment means for adjusting power of the acquired light of the first wavelength (λ1) and power of the acquired light of the second wavelength (λ2) to the first transmission power and the second transmission power, respectively, in such a manner that an average of the first and second transmission powers is zero; a generating means for generating information-transmitting dummy light of two consecutive bits by combining the light of the first wavelength (λ1) with the first transmission power and the light of the second wavelength (λ2) with the second transmission power; and a multiplexing means for transmitting multiplexed light to another communication device, the multiplexed light being achieved by multiplexing the information-transmitting dummy light with communication light serving as light for a predetermined communication in such a way as not to overlap each other on a time axis. a dummy light source for generating dummy light; a setting means for setting first and second wavelengths (λ1, λ2) being selected from wavelengths of light included in the dummy light, and first and second transmission powers being selected, according to a first communication status of the communication device, from a plurality of transmission powers set in advance, the first communication status indicating that a transmission status of the communication device is normal or abnormal; an acquiring means for acquiring light of the first wavelength (λ1) and light of the second wavelength (λ2), from the dummy light, wherein the light of the first wavelength (λ1) and the light of the second wavelength (λ2) do not overlap each other on a time axis; an adjustment means for adjusting power of the acquired light of the first wavelength (λ1) and power of the acquired light of the second wavelength (λ2) to the first transmission power and the second transmission power, respectively, in such a manner that an average of the first and second transmission powers is zero; a generating means for generating information-transmitting dummy light of two consecutive bits by combining the light of the first wavelength (λ1) with the first transmission power and the light of the second wavelength (λ2) with the second transmission power; and a multiplexing means for transmitting multiplexed light to another communication device, the multiplexed light being achieved by multiplexing the information-transmitting dummy light with communication light serving as light for a predetermined communication in such a way as not to overlap each other on a time axis. <EOS>