10 Gbit/s-120 km standard fiber transmission employing a novel optical phase-encoded intensity modulation for signal spectrum compression

Recent reports have clarified that a duobinary three-level transmission and an optical duobinary modulation exhibit high chromatic dispersion tolerance at high bit rate, because spectrum bandwidth is much narrower than that of binary intensity modulation (IM). Compared with binary-IM, however, duobinary modulation requires higher amplification linearity for electrical devices, especially high-power modulator drivers, because the multilevel signal is more sensitive to intersymbol interference. This paper proposes the use of an optical phase-encoded intensity modulation as an equivalent scheme for optical duobinary modulation. Employing a separate binary modulation of intensity and phase of the carrier light, signal spectrum compression and resulting large chromatic dispersion tolerance have been observed at 10 Gbit/s.