High-Power, Low RIN 1.55-μ m Directly Modulated DFB Lasers for Analog Signal Transmission

We report the demonstration of high-power and low relative intensity noise (RIN) directly modulated distributed feedback lasers at 1.55 μm. We have developed a structure with asymmetrical cladding to reduce internal losses due to the p-doped upper cladding. We obtain an output power of 140 mW at 550 mA and an RIN below -157 dB/Hz in the 0.1-20 GHz range along with a high side-mode suppression ratio (>;55 dB). The modulation bandwidth was larger than 7 GHz. The characteristics of these lasers, namely a high electrical to optical conversion efficiency (0.340 W/A at 350 mA), low noise, high power (98 mW at 350 mA), and linearity, make them the perfect candidates for high gain, high dynamic directly modulated analog links.