Nortel Networks 10292FA - Manual (Page 27)

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Installation and Networking Guidelines for Optical Routing
Chapter 2
Calculating transmission distance
This chapter will help you determine the maximum transmission distance for your
CWDM network configuration.
This chapter includes the following topics:
• “About transmission distance and optical link budget” next
• “Point-to-point transmission distance” on page 29
• “Mesh ring transmission distance” on page 30
• “Hub and spoke transmission distance” on page 33
About transmission distance and optical link budget
By calculating the optical link budget, you can determine a link’s transmission
distance, or the amount of usable signal strength between the point where it
originates and the point where it terminates. The loss budget, or optical link
budget, is the amount of optical power launched into a system that is expected to
be lost through various mechanisms acting on the system, such as the absorption
of light by molecules in an optical fiber. Factors that affect transmission distance
include:
• fiber optic cable attenuation (typically 0.25 dB - 0.3 dB per kilometer)
• network devices the signal passes through
• connectors
• repair margin (user-determined)
Note: Insertion loss budget values for the optical routing system CWDM
OADM and CWDM OMUX include connector loss.