The expansion capability of the channel number in the optical demultiplexer using two cascaded photopolymer volume gratings is reported. It could be accomplished by designing of two gratings with different spectral range. As a result of the experiment, a 0.4-nm-spaced 130-channel demultiplexer with the channel uniformity of 3.5dB, the 3 dB-bandwidth of 0.12 nm, and the channel crosstalk of - 20 dB is experimentally demonstrated.