Disclosed herein is a wavelength division multiplexing device. The wavelength division multiplexing device includes a first optical circulator and a Fiber Bragg Grating (FBG). The first optical circulator has a first plurality of ports. The FBG is connected to one of the first plurality of ports of the first optical circulator to reflect or transmit some of the wavelength channels of an optical signal input to the first optical circulator. The FBG is a phase-sampled grating. In the phase-sampled grating, the refractive index of an optical fiber core is modulated by a predetermined chirp in a grating period and a predetermined chirp in a sampling period, and the chirps in the grating period and the sampling period are set to allow dispersion values of all wavelength channels, which are reflected in the FBG, to have a linear function relationship with wavelengths.