Understanding Qfx Series Fiber-Optic Cable Signal Loss, Attenuation, And Dispersion - Juniper QFX5200 Hardware Manual

Table 33: QSFP+ MPO Fiber-Optic Crossover Cable Pinouts
Pin
10
11
12
Understanding QFX Series Fiber-Optic Cable Signal Loss, Attenuation,
and Dispersion
IN THIS SECTION
Signal Loss in Multimode and Single-Mode Fiber-Optic Cables | 79
Attenuation and Dispersion in Fiber-Optic Cable | 80
To determine the power budget and power margin needed for fiber-optic connections, you need to
understand how signal loss, attenuation, and dispersion affect transmission. The QFX Series uses various
types of network cables, including multimode and single-mode fiber-optic cables.
Signal Loss in Multimode and Single-Mode Fiber-Optic Cables
Multimode fiber is large enough in diameter to allow rays of light to reflect internally (bounce off the
walls of the fiber). Interfaces with multimode optics typically use LEDs as light sources. However, LEDs
are not coherent light sources. They spray varying wavelengths of light into the multimode fiber, which
reflect the light at different angles. Light rays travel in jagged lines through a multimode fiber, causing
signal dispersion. When light traveling in the fiber core radiates into the fiber cladding (layers of lower
refractive index material in close contact with a core material of higher refractive index), higher-order
mode loss occurs. Together, these factors reduce the transmission distance of multimode fiber compared
to that of single-mode fiber.
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Pin
3
2
1
79