Absolute Polar Duty-Cycle Division Multiplexing（APDCDM）is a novel multiplexing technology used to reduce the signals’ voltage level in Duty-Cycle Division Multiplexing（DCDM）system.In order to further reduce the number of voltage levels

a novel coding technique called Improved-APDCDM（I-APDCDM）is proposed.The principle of I-APDCDM is first introduced.An optical fiber transmission system based on I-APDCDM is then designed by joint simulation of Optisystem and MATLAB.The effects of transmission distance and extinction ratio of modulator are analyzed.The simulation results show that

comparing with APDCDM

the number of voltage levels of system is reduced by 1and the power of transmitted signal is reduced by A2 Ts/24.Therefore

the I-APDCDM not only reduces the number of voltage levels but also significantly improves the system performance.