is smaller then the optical confinement coefficient length and sectional area of the active layer are the same between the wavelength converting soa 3 and the signal amplifying soa 8 according to embodiment 1 but light with a wavelength having a small differential gain is used as the input signal light ps thus even if light with a large intensity is inputted an increment of the light confined in the active layer is small this can prevent saturation in signal amplification on the other hand even if light with a small intensity is inputted the light is amplified in the signal amplifying soa 8 thus a wide input dynamic range is obtained in the above described optical wavelength converter 1 the respective wavelengths of the input signal light and the direct current light are selected such that the differential gain of the signal amplifying soa 8 at the wavelength of the input signal light is less than the differential gain of the wavelength converting soa 3 at the wavelength of the direct current light therefore even if the input signal light has a large intensity signal deformation can be prevented while the input dynamic range is kept wide fig7 shows data of differential gains relative to wavelengths of the wavelength converting soa and the signal amplifying soa according to embodiment 2 of the present invention fig8 is a flow chart of a procedure of manufacturing an optical wavelength converter according to embodiment 2 an optical wavelength converter according to embodiment 2 has the same components as those of the optical wavelength converter 1 according to embodiment 1 except the signal amplifying soa thus the.