The present invention provides a method for controlling the light emitter and the optical modulator bias method. The optical transmitter comprising: a signal generator configured to generate data based on input driving signal; an optical modulator configured to intensity of light having an output voltage in response to the applied voltage is changed - light intensity characteristics and is configured to generate the drive signal corresponding to an optical signal; multiplier, which is configured with the drive signal from the electric signal obtained by multiplying the optical signal; and a control unit, which is configured to controlling the bias voltage of the optical modulator based on an output of the multiplier.

The present invention relates to a wavelength dispersion compensation design method of any link that includes a plurality of nodes including a plurality of spans and the add / drop function extracted from the optical network (N1, N4), 2 invention There is an example diagram of the applied optical network. All residual dispersion range of each path that reaches each node, so as to be within the allowable residual dispersion range set as the transmission enabling condition for all paths of the link, the chromatic dispersion compensator provided in each path by configuring to set the chromatic dispersion compensation amount, common to point-to-point transmission systems and ring configuration system, and can be performed formulated wavelength dispersion compensation amount optimization.