| 摘要 |
PURPOSE: To attain long distance transmission even in an optical fiber transmission line with large spectrum spread by moving a central wavelength of a rise part of an optical pulse to a long wavelength side and moving the central wavelength of the fall part to a short wavelength side. CONSTITUTION: This device is provided with an optical waveguide 1 largely applying phase modulation, the optical waveguide 2 small applying the phase modulation and a modulating electrode 3, etc. Then, phases of respective waveguides of a modulator are modulated asymmetrically. That is, the central wavelength of output light is moved to the long wavelength side at the rise part, and further, it is moved to the short wavelength side at the fall part. By wavelength chirping generated by asymmetrically modulating the phase and the effect of the positive spectrum spread of the optical fiber transmission line, since the wavelength becomes long at the rise part of the optical pulse, a propagation speed is delayed relatively, and the propagation speed is quickened relatively at the fall part conversely. Thus, pulse compression occurs in the optical pulse, and a transmittable optical fiber length is improved as a result. |
