An optimal power distribution analysis for an all-optical sampling orthagonal frequency division multiplexing (OFDM) scheme with multiple modulation formats including differential phase shift keyed (DPSK), differential quadrature phase shift keyed (DQPSK), and non-return-to-zero (NRZ) is proposed. The noise tolerances of different modulation formats are analyzed, and the optimal input power ratio between phase and intensity modulation formats for the best overall receiving performance is investigated under unchanged total input power. Moreover, this scheme can seamlessly coexist with the traditional WDM channel.