Network Router User Manual

16
T1 FIBER OPTIC LINE EXTENDER/SIMULATOR
Appendix: Fiber Optic Planning
Guidelines
A.1 Introduction
Designing a fiber optic link means considering two main physical limitations:
System attenuation and fiber optic dispersion.
Attenuation results when properties of the fiber optic link reduce the intensity of
the fiber optic signals. Dispersion occurs in high-speed links and causes
degradation of fiber optic signals, disabling the receiver that would interpret them
correctly.
The analysis of the planned fiber optic link is a two-step process. First, you must
calculate the attenuation of the complete system to ensure that the units can cope
with the losses of the link. Then, you must enter the intended distance between the
units into the operation diagram (see Figure A-2). (Make sure the distance is
confirmed by the calculation above.) These calculations are explained in
Section A.2.
When you calculate the maximum range, keep in mind that extremely short
cabling can be problematic, too. Avoid receiver overload conditions for proper
data transmission.
For wavelength/multiplexing (WDM) equipped units, you must perform the
calculations for each wavelength independently (twice total). You must operate the
WDM-equipped counterparts within the restrictions defined by both resulting
operation diagrams.
Please observe that the optical power budget stated in the documentation of a
WDM-equipped unit is valid for the transmitted wavelength only. The optical
power budget for the received wavelength can be found in the documentation of
the counterpart unit.