Abstract: In order to satisfy the demand of short reach optical communication system with low cost for higher rate, an optical fiber transmission system was proposed based on intensity modulation and direct detection(IM/DD) polarization division multiplexing 4 order pulse amplitude modulation(PDM-PAM4). The system's structure is simple. By utilizing the effective digital signal processing(DSP) algorithm, including the station of polarization(SOP) estimation, mixed polarization beat interference(MPBI) elimination and adaptive multiple-input multiple-output(MIMO) filter based on least mean square(LMS) algorithm, its stablity and reliablity can be realized. Finally in the Matlab and VPI software joint simulation platform, a 224 Gbit/s PDM-PAM4 system was simulated and analyzed in detail.

Key words: polarization division multiplexing, intensity modulation and direct detection, 4 order pulse amplitude modulation, short reach optical communication