In this paper, we demonstrate the use of photonic crystal (PC) directional couplers to separate light of wavelengths at 1.31 and 1.55 μm. The PC structure consists of InAlGaAs nanorods arranged in hexagonal lattice. The simulation of our device is implemented by the finite-difference time-domain method. The devices are fabricated by e-beam lithography and conventional photolithography. We use the strong inverse method (SIM) of e-beam lithography to make the pattern smoother. The measurement results confirm that 1.31/1.55-μm wavelength splitter can be realized in PC structures formed by nanorods.