Network Cable And Transceiver Planning; Understanding Fiber-Optic Cable Signal Loss, Attenuation, And Dispersion; Signal Loss In Multimode And Single-Mode Fiber-Optic Cable; Attenuation And Dispersion In Fiber-Optic Cable - Juniper M320 Hardware Manual

CHAPTER 12

Network Cable and Transceiver Planning

Understanding Fiber-Optic Cable Signal Loss, Attenuation, and Dispersion

Signal Loss in Multimode and Single-Mode Fiber-Optic Cable

Attenuation and Dispersion in Fiber-Optic Cable

Copyright © 2015, Juniper Networks, Inc.
Understanding Fiber-Optic Cable Signal Loss, Attenuation, and Dispersion on page 111
Calculating Power Budget and Power Margin for Fiber-Optic Cables on page 112
This topic describes signal loss, attenuation, and dispersion in fiber-optic cable. For
information about calculating power budget and power margin for fiber-optic cable, see
"Calculating Power Budget and Power Margin for Fiber-Optic Cables" on page 112
Supported Network Interface Standards by Transceiver for ACX, M, MX, and T Series Routers
or Supported Network Interface Standards by Transceiver for PTX Series Routers.
Signal Loss in Multimode and Single-Mode Fiber-Optic Cable on page 111
Attenuation and Dispersion in Fiber-Optic Cable on page 111
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 sources. They spray varying wavelengths
of light into the multimode fiber, which reflects 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, higher-order mode loss (HOL)
results. Together these factors limit the transmission distance of multimode fiber
compared with single-mode fiber.
Single-mode fiber is so small in diameter that rays of light can reflect internally through
one layer only. Interfaces with single-mode optics use lasers as light sources. Lasers
generate a single wavelength of light, which travels in a straight line through the
single-mode fiber. Compared with multimode fiber, single-mode fiber has higher
bandwidth and can carry signals for longer distances.
Exceeding the maximum transmission distances can result in significant signal loss, which
causes unreliable transmission.
Correct functioning of an optical data link depends on modulated light reaching the
receiver with enough power to be demodulated correctly. Attenuation is the reduction in
and
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