We propose and experimentally demonstrate mutual optical format conversion between signals characterized as 10-Gb/s nonreturn-to-zero on-of-keying(NRZ-OOK)and NRZ binary phase-shift keying(BPSK)types.The conversion is based on stimulated Brillouin scattering(SBS)in a single-mode optical fber.An OOK signal is converted into a BPSK signal through optical carrier absorption,for which a SBS loss of30 MHz is used in long-haul transmission.The converted BPSK signal is reverted to an OOK signal with a corresponding SBS gain of 30 MHz for direct detection.The proposed OOK-to-BPSK and BPSK-to-OOK format conversions can be implemented in transmitter and receiver nodes by using a laser source as the Brillouin pump.
An optimal power distribution analysis for an all-optical sampling orthagonal frequency division multiplexing(OFDM)scheme with multiple modulation formats including diferential phase shift keyed(DPSK),diferential 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.
A novel method to improve the phase coherence of optical pulse train with wavelength conversion based on cross-phase modulation and four-wave mixing effects in high nonlinear fiber is proposed.The method is experimentally demonstrated and the phase coherence of the pulse train from the mode-locked fiber laser is greatly improved.The improvement of the pulse quality is characterized in time and frequency domain.
