Abstract:In this paper, based on photonic crystal (PC), a coarse-wavelength-mode-division hybrid multiplexer/de-multiplexer is proposed. The coarse wavelength division multiplexing (CWDM) and mode division multiplexing (MDM) can be integrated on a chip of PC. According to coupled mode theory in time, point-defect cavities and wavelength-selective cavities were introduced in the PC to filter the optical wave. According to the lateral coupled mode theory, asymmetric parallel waveguides (APWs) consisted of single-mode waveguides (SMWs) and multi-mode waveguides (MMWs) were introduced in the PC to achieve mode conversion. The finite-difference time-domain (FDTD) method is used for property analysis. The simulation results show that the device achieves the multiplexing/de-multiplexing of four signals, i.e., the 1550 nm TE0 mode, 1570 nm TE0 mode, 1550 nm TE1 mode and 1570 nm TE1 mode. The device exhibits not only a low insertion loss (<0.23 dB) but also low mode crosstalk (<-15.21 dB). It has considerable potential for application in the CWDM-MDM system and great value to improve the capacity of metropolitan area network.