It is made possible to accommodate a plurality of services and transmit each of the accommodated services to a corresponding transmission device. An optical transmitter according to an exemplary aspect of the present invention includes sub-carrier adjusting means for outputting sub-carriers to a plurality of output ports according to a control signal; encoding processing means for mapping client data on a plurality of output lanes according to the control signal; a plurality of modulation means for modulating the sub-carriers inputted through the output ports by client data inputted through the output lanes and outputting modulated signals; and control means for generating and outputting the control signal based on transmission information.