DFB laser (Distributed FeedBack laser)

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

74570c04.qxd 9/11/07 12:19 PM Page 132

• Table H-4: Selected ITU-T H-Series Recommendations
• Table I-1: Frame Relay Implementation Agreements
• Table I-2: Index of Refraction (IOR)
• Table I-3: IPv4 Address Classes
• Table I-4: Selected ITU-T I-Series Recommendations
• Table I-4: Selected ITU-T I-Series Recommendations (continued)
• Table I-5: ITU-T Series Recommendations
• Table J-1: Japanese Digital Hierarchy: J-carrier
• Table L-1: Longitudinal Redundancy Check (LRC)
• Table M-1: International Morse Code
• Table O-1: OSI Reference Model Layers
• Table O-2: G.709 Line Rates and Corresponding SDH/SONET Line Rates
• Table P-1: Evolution of PBX technology
• Table P-2: Military and Aviation Phonetic Alphabet
• Table Q-1: Selected ITU-T Q-Series Recommendations
• Table R-1: Before and After: Bell Operating Companies (BOCs) and Regional Bell Operating
• Table R-1: Before and After: Bell Operating Companies (BOCs) and Regional Bell Operating
• Table R-2: Coaxial Cable Types
• Table S-1: SDTV Scanning Formats
• Table S-2: SONET/SDH Signal Hierarchy
• Table T-1: North American Digital Hierarchy: T-carrier
• Table T-2: TCP/IP Protocol Suite
• Table V-1: Electromagnetic Signal Propagation Velocity (Approximate)
• Table V-2: Vertical Redundancy Check (VRC)
• Table V-3: Selected ITU-T V-Series Recommendations