A diode laser that operates at high output power levels over very short cycle times, and emits a signal at long wavelengths with very narrow spectral width.A DFB uses diffraction gratings, which act as distributed reflectors, to create the photonic resonance and oscillation in the cavity.This approach improves on the mirrors used in Fabry-Perot and vertical cavity surface-emitting laser (VCSEL) cavities. The high output power level means that the signal can suffer attenuation over longer distances and survive.The short cycle time translates into a very high bit rate.The diffusion grating supports signal emissions at spectral widths under 1 nm, which effectively means that a DFB laser emits a single wavelength. This narrow spectral width is significant in the context of wavelength division multiplexing (WDM). DFB lasers run in the 1300 and 1550 nm regions. As signals at these wavelengths attenuate relatively little, they are preferred for long haul applications. Also,WDM is centered on the 1550 nm window. In total, these characteristics currently make DFB lasers the overwhelming choice of telecommunications carriers and CATV providers, in high speed local loop and long haul wide area network (WAN) applications, where their relatively high cost is justifiable. See also attenuation, bandwidth, diffraction grating, Fabry-Perot laser, laser, laser diode, LED, local loop, spectral width, VCSEL, WAN, wavelength, WDM, and window.