A node apparatus comprising: a first optical unit for outputting a first optical signal received from a first terminal station and addressed to a second terminal station, and a second optical signal received from the first terminal station and addressed to a third terminal station; and a second optical unit for receiving the first and second optical signals outputted from the first optical unit, optically removing a portion of a spectrum of the first optical signal to generate a fourth optical signal, and passing the second optical signal leaving unchanged to transmit the second and fourth optical signals to the third terminal station, characterized in that the second optical unit comprises: a 3-port wavelength filter for splitting the first and second optical signals outputted from the first optical unit into the first optical signal and the second option signal; a narrowband interleaver for dividing the spectrum of the first optical signal into a plurality of wavelength bands and outputting the first optical signal as the fourth optical signal after removing a portion of each wavelength band of the plurality of wavelength bands of the first optical signal, and a second coupler for combining the second optical signal that was split by the 3-port wavelength filter and the fourth optical signal and transmitting the combined signal to the third terminal station. a first optical unit for outputting a first optical signal received from a first terminal station and addressed to a second terminal station, and a second optical signal received from the first terminal station and addressed to a third terminal station; and a second optical unit for receiving the first and second optical signals outputted from the first optical unit, optically removing a portion of a spectrum of the first optical signal to generate a fourth optical signal, and passing the second optical signal leaving unchanged to transmit the second and fourth optical signals to the third terminal station, characterized in that the second optical unit comprises: a 3-port wavelength filter for splitting the first and second optical signals outputted from the first optical unit into the first optical signal and the second option signal; a narrowband interleaver for dividing the spectrum of the first optical signal into a plurality of wavelength bands and outputting the first optical signal as the fourth optical signal after removing a portion of each wavelength band of the plurality of wavelength bands of the first optical signal, and a second coupler for combining the second optical signal that was split by the 3-port wavelength filter and the fourth optical signal and transmitting the combined signal to the third terminal station. a 3-port wavelength filter for splitting the first and second optical signals outputted from the first optical unit into the first optical signal and the second option signal; a narrowband interleaver for dividing the spectrum of the first optical signal into a plurality of wavelength bands and outputting the first optical signal as the fourth optical signal after removing a portion of each wavelength band of the plurality of wavelength bands of the first optical signal, and a second coupler for combining the second optical signal that was split by the 3-port wavelength filter and the fourth optical signal and transmitting the combined signal to the third terminal station.