| 摘要 |
PURPOSE:To enlarge the transmission distance of information by suppressing the optical wavelength fluctuation of a signal light generated at the time of executing an intensity modulation with an optical modulator by changing the oscillation light wavelength of a semiconductor laser light source. CONSTITUTION:An optical output Pout becomes a signal whose intensity is modulated since an internal absorption coefficient of an optical modulator 2 is varied by applying an input signal IN to an electric field type optical modulator 2. In this case, in an optical signal, a wavelength system by a phase modulation simultaneously with an intensity modulation is generated, therefore, it becomes a state that wavelength spectrum broadening is large. In such a state, by generating a differention signal to the input signal IN by a differentiation circuit 3 and superposing it on a semiconductor laser DC bias current Ib, the oscillation wavelength of a semiconductor laser 1 is varied, and a wavelength shift generated by the electric field absorption type optical modulator 2 is offset. In such a manner, the length of an optical fiber which can execute the transmission is enlarged. |
