Large Area Corning LEAF Reduced Slope Negative Lucent Dispersion TrueWave RS Corning LS Attenuation Dispersion Dispersion DCF = Dispersion Standard single-mode fiber Compensation Attenuation (SMF; e.g., SMF 28) Non-zero Fiber dispersion shifted (generic fiber) fiber (NZDSF) Note: Zero-dispersion fiber cannot be used for Dispersion- WDM applications shifted fiber Zero-OH fiber (DSF) eliminates the 1385 nm water peak Wavelength (nm) Cross Index Light Input Output Figure 2-17 Section Profile Pulse Pulse Behavior of the rays as they travel down Multi- the fiber. Stepped- index Multi- Graded- index Single- Stepped- index Chapter 2 2.1.5 Single-Mode Fibers As noted, single-mode fibers are designed SO that only one mode propagates. Here the information transmission capacity is limited by the phenomenon of chromatic dispersion, which, as discussed previously, is a result of the wavelength-dependant velocities of propagation in the fiber material. Con- ventional single-mode fibers (known by the siglum SMF-28) have their min- imum chromatic dispersion (that is, their maximum transmission capacity) near 1.31 um. Conventional single-mode fibers are classified as either matched- cladding or depressed-cladding designs. In the former type, the cladding has the same index of refraction from the core-cladding interface to the outer surface of the fiber. In the latter type, there are two layers of cladding mate- rial. The index of refraction of the inner cladding, which is adjacent to the fiber core, is lower than that of the outer cladding (typically undoped silica). Single-mode fibers are characterized by the mode field diameter (MFD) and by the cutoff wavelength. The MFD is a measure of the width of the guided optical power's intensity distribution in the core and cladding. Typ- ical values for the MFD are in the 10.0-um range. The cutoff wavelength is the wavelength below which a single-mode fiber propagates more than one mode and above which only a single (fundamental) mode can operate. DSF is designed so that the wavelength 