A 2-Gbit/s optical FSK heterodyne transmission experiment using a 1520-nm DFB laser transmitter

Optical FSK transmission at 2 Gbit/s using a directly modulated DFB laser at 1520-nm wavelength is reported. A receiver sensitivity of \bar{P} = -36.7 dBm ( \eta\bar{P} = -39.2 dBm) at 10 -9 BER was achieved for transmission over 101 km of single-mode fiber with no additional penalty attributable to the fiber. The effect of the nonlinear phase of the transmitter FM response, and the system performance for discriminator demodulation, including the impact of laser phase noise, is analyzed and compared with experimental results.