Five-gigabit/s performance of integrated light sources consisting of λ/4 shifted DFB laser and E-A modulator with S.I. InP BH structure

The device considered was fabricated using a three-step growth procedure and a selective Zn-diffusion process. For the integrated device consisting of a 350-μm-long laser and a 400-μm-long modulator, the 3-dB bandwidth was 8 GHz. The response was fully flat, and the relaxation oscillation resonance of the laser was sufficiently suppressed due to nearly complete electrical isolation between the laser and modulator. The bit error rate (BER) characteristics were measured under 5-Gb/s NRZ pseudorandom modulation, and error-free operation was confirmed. Five-gigabit-per-second transmission experiments were performed using conventional single-mode fiber with zero dispersion at a 1.3-μm wavelength. The modulator of the integrated device was driven by a 5-Gb/s NRZ signal of a (1,0) fixed pattern. The extinction ratio was 6 dB. Output from the modulator was coupled into the single-mode fiber by a lensed fiber. The BER characteristics are shown. Five-gigabit-per-second, 73-km transmission was successfully achieved with no error floor in spite of large (1467-ps/nm) dispersion. The power penalty was 2.7 dB at a BER of 10^-9 after 73-km transmission. However, the estimated power penalty from spectral burdening caused by the α parameter was much smaller than the measured value.