Directly Modulated Tunable External Cavity Laser Transmitter Optical Sub-Assembly

A compact-size and low-cost tunable external cavity laser transmitter optical sub-assembly with butt-coupled superluminescent diode and polymer Bragg reflector (PBR) is described. The output wavelength of the laser is widely tuned over 16 nm by a heater of the PBR and is finely tuned by a phase of the PBR. The threshold current and output power slope of the laser are 8 mA and 0.117 W/A, respectively, at the temperature of 25∘ C. The directly-modulated tunable laser provides 2.5-Gb/s transmission through a 80-km standard single-mode fiber without an error-flow by controlling the phase power of the PBR and its dispersion power penalty is< 0.7~ dB.