We propose a novel optical ADM node construction which can add or drop a voluntary wavelength in network system. The node is composed of a disk filter that enables the transmission wavelength to be linearly tuned by rotating the disk substrate. When the collimated optical beam with multi-wavelengths transmits the disk filter, only the specific wavelength corresponding the disk filter position transmits, and then the wavelength can be dropped to the opposite fiber, and the rest of the wavelengths are reflected. When a voluntary wavelength corresponding to the disk filter position is added from the fiber of the opposite side, the add function can be achieved. As described above, the Add/Drop function of a voluntary wavelength can be easily realized by using this disk filter. The features of this novel ADM are described, and the optical reflection and transmission characteristics of a dielectric-multi-layer-film are simulated theoretically. The wavelength shift by the inclination of the disk surface is also discussed theoretically. The mechanical stability is examined and the high stability is confirmed. Finally, using this disk filter with collimated optical fibers, the optical Add/Drop performance is demonstrated and the data transmission characteristics for 2.5 Gbps is evaluated experimentally.