The phase-shaped binary transmission (PSBT): a new technique to transmit for beyond the chromatic dispersion limit

This paper is an introduction to phase-shaped binary transmissions (PSBT), which allow to bridge more than 200 km in the linear regime over standard dispersive fibres. It also explains why duobinary transmissions did bridge up to 243 km. The spectral compression induced by the duobinary coding is not able to explain the impressive results obtained during recent experiments of optical phase-coded duobinary transmissions. We showed that the /spl Pi/ phase shift occurring in each "O" neighbouring a "1" allows the energy of the pulse over a longer distance in the "1" bit-time to be kept. This result has been confirmed analytically and numerically. The value of the optimal phase shift may vary depending on the rise- and fall-times of the phase modulation. We have named phase-shaped binary transmission (PSBT) on this principle.