An optical add/drop multiplexer includes a first optical coupler receiving an optical signal including a plurality of multiplexed wavelengths, a wavelength blocker receiving the optical signal from the first optical coupler, and blocking at least one wavelength of the plurality of multiplexed wavelengths, a first wavelength selective switch, having one input port receiving the outputted optical signal from the first optical coupler and a plurality of output ports, demultiplexing a plurality of arbitrarily selected multiplexed wavelengths from the received optical signal, a second wavelength selective switch, having a plurality of input ports, each input port receiving a different optical signal and one output port, multiplexing a plurality of arbitrarily selected wavelength signals on the plurality of input ports, and a second optical coupler receiving the optical signal output from the wavelength blocker and multiplexed wavelength signal from the second wavelength selective switch.