ABSTRACT
We study the role of ultra-broadband infrastructures in reducing the economic recession caused by the 2020 pandemic. We exploit the variation in GDP and employment that happened between 2019 and 2020 as a result of the Covid-19 pandemic outbreak, and we investigate whether UBB investments had an impact on economic resilience. We use micro-level data on UBB exposure in 2019 matched with municipality-level information on local GDP and employment levels based on tax declarations for the period 2019-2020. We address the endogeneity between UBB and local income by exploiting the distance from the closest backbone node of the upstream telecommunication network. We find that exposure to UBB mitigates the negative effect of the pandemic on local employment. One additional year of UBB exposure increases local employment by 1.3 percentage points. The effect is stronger in areas hit more severely by the pandemic, thus confirming the role of advanced broadband infrastructures on the economic resilience from negative shocks.
ABSTRACT
We demonstrate a multistage erbium fiber amplifier seeded by a gain-switched laser diode operating at a wavelength of 1550 nm and a repetition rate of 1 MHz. The pulse energy is 0.5 µJ, and the pulse duration is 40 ps, resulting in a peak power of 11.4 kW. The three-stage all-fiber amplifier system is designed to avoid any spectral distortions induced by gain saturation or nonlinear effects and high levels of amplified spontaneous emission. The output pulses are close to transform limited with a Gaussian pulse envelope.
ABSTRACT
A common issue in fiber-based supercontinuum (SC) generation under continuous-wave pumping is that the spectral width of the resulting source is related to the input power of the pump laser used. An increase of the input pump power leads to an increase of the spectral width obtained at the fiber output, and therefore, the average power spectral density (APSD) over the SC spectrum does not grow according to the input power. For some applications it would be desired to have a fixed spectral width in the SC and to increase the average PSD proportionally to the input pump power. In this paper we demonstrate experimentally that SC generation under continuous-wave (CW) pumping can be spectrally bounded by using a fiber with two zero-dispersion wavelengths (ZDWs). Beyond a certain pump power, the spectral width of the SC source remains fixed, and the APSD of the SC grows with the pump power. In our experiment we generate a reasonably flat, spectrally-bounded SC spanning from 1550 nm to 1700 nm. The spectra l width of the source is shown to be constant between 3 and 6 W of pump power. Over this range, the increase in input power is directly translated in an increase in the output APSD. The experimental results are confirmed by numerical simulations, which also highlight the sensitivity of this configuration to variations in the fiber dispersion curve. We believe that these results open the way for tailoring the spectral width of high-APSD CW SC by adjusting the fiber dispersion.
