Aiming at low energy efficiency and high complexity of high-level modulation in DCO-OFDM(DC-biased optical OFDM) system, subcarrier index power modulated (Subcarrier Index-Power Modulated, SIPM) layered asymmetric clipped optical OFDM(LACO-OFDM) is proposed. The proposed transmission technology adopts low order constellation mapping formats 8-PSK and QPSK for high and low power subcarriers respectively, and combines LACO technology, which effectively avoids the reductions of energy efficiency of OFDM system caused by DC bias and increases the signal transmission bit rate. The simulation results show that SIPM-LACO-OFDM improves the energy efficiency without reducing the spectral efficiency, and has better BER performance and nonlinear tolerance performance. Compared with the traditional SIPM-OOFDM system, the received optical power penalties in SIPM-LACO-OFDM is ~1.8 dB over 25 km IMDD SSMF PON system.