Low-cost WDM terminal device accommodating plurality of client signal

A WDM-ADM device located in a WDM network, said WDM-ADM device comprising:

• a first compensator that collectively optically compensates dispersion of each wavelength of a first plurality of wavelength division multiplexed optical client signals;
• a transmission amplifier that collectively adjusts levels of said first plurality of wavelength division multiplexed optical client signals;
• an adding unit that receives the first plurality of wavelength division multiplexed optical client signals as a WDM signal, and individually receives at least one other optical client signal provided to the adding unit through at least one transponder, and that adds together the received WDM signal and the individually received at least one other optical client signal;
• a second compensator that receives a wavelength division multiplexed signal comprising a second plurality of optical client signals and a third plurality of optical client signals, and collectively compensates dispersion of the second plurality of optical client signals and the third plurality of optical client signals in the wavelength division multiplexed signal;
• a reception amplifier that collectively adjusts levels of the second plurality of optical client signals and the third plurality of optical client signals in the wavelength division multiplexed signal;
• and
• a dropping unit that receives the wavelength division multiplexed signal comprising the second plurality of optical client signals and the third plurality of optical client signals, drops the second plurality of optical client signals from the third plurality of optical client signals, keeping wavelengths of the second plurality of optical client signals multiplexed together,
• wherein the dropping unit transmits the dropped second plurality of optical client signals to a place which is different from where the third plurality of optical client signals is transmitted, while keeping the wavelengths of the second plurality of optical client signals multiplexed.

An apparatus comprising:

• a dispersion compensator that collectively compensates for dispersion of a first plurality of wavelength division multiplexed optical client signals as a WDM signal;
• an amplifier that collectively adjusts levels of the first plurality of wavelength division multiplexed optical client signals as the WDM signal;
• a multiplexing unit that receives the first plurality of wavelength division multiplexed optical client signals as the WDM signal from the amplifier, and individually receives at least one other optical client signal provided to the multiplexing unit through at least one transponder, and wavelength division multiplexes together the received WDM signal and the individually received at least one other optical client signal, to thereby output a wavelength division multiplexed light which comprises the first plurality of wavelength division multiplexed optical client signals and the individually received at least one other optical client signal;
• and
• a separating unit that receives a wavelength division multiplexed signal comprising a second plurality of optical client signals and a third plurality of optical client signals, separates the second plurality of optical client signals from the third plurality of optical client signals, while keeping wavelengths of the second plurality of optical client signals multiplexed together,
• wherein the separating unit transmits the separated second plurality of optical client signals to a place which is different from where the third plurality of optical client signals is transmitted, while keeping the wavelengths of the second plurality of optical client signals multiplexed.