Abstract: There is provided a transmission apparatus including: generators to generate optical signals having wavelengths included in a predetermined band, the wavelengths being variable; a transmitter to multiplex the optical signals and transmit the optical signals to another transmission apparatus; a memory; and a processor coupled to the memory and the processor to: monitor reception quality of an optical signal for monitoring received by the another transmission apparatus while changing a wavelength of the optical signal for monitoring which is generated by the generators, determine a first wavelength of a first optical signal having a longest wavelength and a second wavelength of a second optical signal having a shortest wavelength, based on the reception quality monitored, determine a wavelength of an optical signal except for the first and second optical signals, based on the first second wavelengths, and control the wavelength generated by the generators, based on the wavelength determined.

Abstract: An optical transmitter includes an optical isolator that includes a Faraday rotator transmitting light output from a light source, and has a first state in which the light is transmitted through the optical isolator when a first magnetic field is applied to the Faraday rotator, and a second state in which the amount of the light transmitted through the optical isolator is less than that in the first state when a second magnetic field different from the first magnetic field is applied to the Faraday rotator; a junction to which an optical transmission medium into which the light output from the optical isolator is input is connected; a magnetic-field generator that selectively applies the first magnetic field or the second magnetic field to the Faraday rotator; and a switching unit that switches the magnetic-field generator to the second state when the optical transmission medium is not connected to the junction.