We propose a novel transmitter consisting of a frequency-modulated widely tunable super-structure-grating distributed Bragg reflector (SSG-DBR) laser and an optical filter. The SSG-DBR laser acts as a frequency modulating light source with a constant output power by modulating the reverse bias voltage in the phase control (PC) region. By optically filtering the output light from the frequency-modulated laser, we have demonstrated 60-and 180-km transmissions for 20-and 10-Gb/s nonreturn-to-zero (NRZ) signals, respectively. The power penalty was 2.2 dB after the 180-km transmission of a 10-Gb/s NRZ signal as determined by bit-error-rate measurements. Furthermore, an extended transmission reach was achieved with a wide tuning range without controlling the bias and modulating voltages in the PC region.
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