13-02-2016, 03:21 PM
Types of Fibers I
! Multimode Fiber: Core Diameter 50 or 62.5 μm
Wide core ⇒ Several rays (mode) enter the fiber
Each mode travels a different distance
! Single Mode Fiber: 10-μm core. Lower dispersion.
Reducing Modal Dispersion
Step Index: Index takes a step jump!
Graded Index: Core index decreases parabolically
Types of Fibers II
Dispersion-Shifted Fiber: Zero dispersion at 1310nm
EDFAs/DWDM systems operate at 1550 nm
Special core profile ⇒ zero dispersion at 1550 nm
! Dispersion Flattened Fiber: 3 ps/nm/km 1300-1700nm
Use 1300 nm now and 1550 in future
Low dispersion causes four-wave mixing
⇒ DSF/DFF not used in DWDM systems