An original design of compact and efficient 16-channels demultiplexer integrated in a photonic crystals PhCs slab for dense wavelength demultiplexing near infrared application operating around two wavelengths 1.31 μm and 1.55 μm with an occupied area of 752.25 μm² is proposed in this paper. The demultiplexer is based on a square lattice two-dimensional PhCs quasi square ring resonator (QSRR) for wavelength division multiplexing applications; it consists of two blocks where each one of theme is dedicated to function around one band of wavelengths 1.31 μm or 1.55 μm separated by a wideband demultiplexer. The demultiplexer is of good-quality factor Q that equals 517.6 for a spectral width of 3 nm and 622 for a spectral width 2.5 nm, low crosstalk values between -9 dB and-41 dB were observed in the same block. Furthermore, an extreme low crosstalk values between -27 dB and-288 dB were noted between two different blocks (1.31 μm and 1.55 μm), with high transmission efficiency of about 90%.