Optical frequency domain differential phase shift keying in femtosecond-pulse spectral modulation systems

We propose a novel scheme of differential phase shift keying (DPSK) in the optical frequency domain. We take advantage of the intrinsic coherence among spectral elements derived by spectrum slicing a femtosecond optical pulse, introducing differential phase modulation between adjacent spectral elements with a femtosecond-pulse shaper. Detection of the differential phase is achieved by a Mach-Zehnder (MZ) or Sagnac interferometric receiver without requirement of any external phase reference.