A novel high spectral efficiency all-optical sampling orthogonal frequency-division multiplexing (AOS-OFDM) scheme with optical cyclic postfixes (OCPs) inserted is proposed. Ultrashort pulses are used as optical samples and processed by all optical discrete Fourier transformers based on fiber Bragg gratings (FBGs) technique. This scheme includes five subcarrier channels with 20 Gb/s differential quadrature phase-shift keying (DQPSK) modulation of each channel. So, the total bit rate is 100 Gb/s. The spectral efficiency is higher than 1.4. Furthermore, with the help of OCPs, the dispersion tolerance of this 100 Gb/s AOS-OFDM system increases to more than 300 ps/nm, which is much higher than a traditional 100 Gb/s DQPSK system.
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