An optical network system comprising: a plurality of optical signal-processing apparatuses (112a, 112b, 112c, 112d, 112e) disposed on an optical network for modulating a signal light propagating through the optical network by a control light, the optical signal-processing apparatus among of the plurality of optical signal-processing apparatuses (112a, 112b, 112c, 112d, 112e)comprising: an optical modulator (1, 11, 76c, 76d) configured to be disposed in the optical network; and a light source configured to output the control light (Ectj) characterized in that: the optical signal-processing apparatus further comprises a plurality of multipliers (ll8a-ll8k), a first WDM coupler and a second WDM coupler: the plurality of multipliers (ll8a-ll8k) configured to multiply a plurality of carrier wave signals (fjl-fjk) different in frequency and a plurality of control signals (Bjl-Bjk) different in information, and generate a plurality of sub-carrier signals (Bj1 -Bjk(fjk)); the light source configured to modulate drive current by frequency-division multiplexed signal of the sub-carrier signals (Bj1 -Bjk(fjk)), and output the control light (Ectj); the first WDM coupler disposed upstream of the optical modulator (1, 11, 76c, 76d), configured to combine the signal light (Es(j-1)) being a wavelength-division multiplexed light and the control light (Ectj) having information; and the optical modulator (1, 11, 76c, 76d) comprising a nonlinear medium configured to input the signal light (Es(j-1)) and the control light (Ectj) after combining to the nonlinear optical medium, and modulate the signal light (Es(j-l)) according to changes in intensity of the control light (Ectj), in the nonlinear optical medium; the second WDM coupler disposed downstream of the optical modulator (1, 11, 76c, 76d), configured to split off the control light (Ectj) from a modulated signal light (Esj) outputted from the nonlinear optical medium. a plurality of optical signal-processing apparatuses (112a, 112b, 112c, 112d, 112e) disposed on an optical network for modulating a signal light propagating through the optical network by a control light, the optical signal-processing apparatus among of the plurality of optical signal-processing apparatuses (112a, 112b, 112c, 112d, 112e)comprising: an optical modulator (1, 11, 76c, 76d) configured to be disposed in the optical network; and a light source configured to output the control light (Ectj) an optical modulator (1, 11, 76c, 76d) configured to be disposed in the optical network; and a light source configured to output the control light (Ectj) characterized in that: the optical signal-processing apparatus further comprises a plurality of multipliers (ll8a-ll8k), a first WDM coupler and a second WDM coupler: the plurality of multipliers (ll8a-ll8k) configured to multiply a plurality of carrier wave signals (fjl-fjk) different in frequency and a plurality of control signals (Bjl-Bjk) different in information, and generate a plurality of sub-carrier signals (Bj1 -Bjk(fjk)); the light source configured to modulate drive current by frequency-division multiplexed signal of the sub-carrier signals (Bj1 -Bjk(fjk)), and output the control light (Ectj); the first WDM coupler disposed upstream of the optical modulator (1, 11, 76c, 76d), configured to combine the signal light (Es(j-1)) being a wavelength-division multiplexed light and the control light (Ectj) having information; and the optical modulator (1, 11, 76c, 76d) comprising a nonlinear medium configured to input the signal light (Es(j-1)) and the control light (Ectj) after combining to the nonlinear optical medium, and modulate the signal light (Es(j-l)) according to changes in intensity of the control light (Ectj), in the nonlinear optical medium; the plurality of multipliers (ll8a-ll8k) configured to multiply a plurality of carrier wave signals (fjl-fjk) different in frequency and a plurality of control signals (Bjl-Bjk) different in information, and generate a plurality of sub-carrier signals (Bj1 -Bjk(fjk)); the light source configured to modulate drive current by frequency-division multiplexed signal of the sub-carrier signals (Bj1 -Bjk(fjk)), and output the control light (Ectj); the first WDM coupler disposed upstream of the optical modulator (1, 11, 76c, 76d), configured to combine the signal light (Es(j-1)) being a wavelength-division multiplexed light and the control light (Ectj) having information; and the optical modulator (1, 11, 76c, 76d) comprising a nonlinear medium configured to input the signal light (Es(j-1)) and the control light (Ectj) after combining to the nonlinear optical medium, and modulate the signal light (Es(j-l)) according to changes in intensity of the control light (Ectj), in the nonlinear optical medium; the second WDM coupler disposed downstream of the optical modulator (1, 11, 76c, 76d), configured to split off the control light (Ectj) from a modulated signal light (Esj) outputted from the nonlinear optical medium.