Comparison of the frequency responses of free-running and injection-locked Fabry-Perot laser diodes up to 10 GHz

The Fabry-Perot semiconductor laser is a simple, low-cost device with a wide spectrum of wavelengths that is nowadays used widely in optical access telecommunications networks. However, due to fiber's chromatic dispersion, the transmission distance and the bit rate of directly modulated Fabry-Perot laser links are limited. In this paper we demonstrate the possibility of injection locking a Fabry-Perot laser, which significantly improves the frequency response in some areas of the frequency spectrum with respect to an unlocked Fabry-Perot laser. This makes the injection-locked Fabry-Perot laser very suitable for use in wavelength-division-multiplexed passive optical access networks, because in optical communications, low-cost communication light sources are crucial. In this paper we have experimentally investigated the frequency response of an injection-locked Fabry-Perot laser diode up to frequencies of 10 GHz. The results show an improvement in the frequency response and 3-dB bandwidth of the directly modulated, injection-locked, Fabry-Perot, laser diode in comparison with the free-running mode.