Photonic generation of ultrawideband signals based on a gain-switched semiconductor laser with optical feedback

A simple photonic approach to generate ultrawideband (UWB) pulse signals utilizing a gain-switched semiconductor laser with optical feedback is proposed and demonstrated. The RF spectrum of the generated chaotic UWB signals has a -10 dB bandwidth of 9 GHz and central frequency of 6.6 GHz (fractional bandwidth of 155%), which is consistent with the Federal Communications Commission indoor mask. The central frequency and -10 dB bandwidth can be tuned by adjusting the bias current and feedback strength of the semiconductor laser. After transmission through a 30 km single-mode fiber, the spectrum shape of the chaotic UWB signals is almost unaffected by the chromatic dispersion of the fiber.