Patent ID: 8401386

Claim:
An optical transmission apparatus comprising: a plurality of wavelength selective switches, each including input ports, a transmission port used to output a wavelength multiplexed light containing input light from the input ports that is switched and multiplexed, and a monitor port used to output a monitored light switched from one of the input ports, so that the input light is monitored; a multiplexer to combine wavelength multiplexed lights output from the transmission ports of the plurality of wavelength selective switches; a monitor to monitor whether a same wavelength of the monitored light output from the monitor port exists in wavelengths of the wavelength multiplexed lights combined by the multiplexer; and a controller to control each of the wavelength selective switches so as to output, from the transmission port, the monitored light switched to the monitor port only when the same wavelength of the monitored light is absent from the wavelengths of the wavelength multiplexed lights combined by the multiplexer prior to receipt of the monitored light, based on a monitor result output by the monitor, and when the monitored light replaces a same wavelength light input to another of the wavelength selective switches.