Juniper MX10004 - MX10004 Fiber-Optic Cable Signal Loss, Attenuation, and Dispersion

MX10004 Fiber-Opc Cable Signal Loss, Aenuaon, and Dispersion
IN THIS SECTION
Signal Loss in Mulmode and Single-Mode Fiber-Opc Cables | 97
Aenuaon and Dispersion in Fiber-Opc Cables | 97
To determine the power budget and power margin needed for ber-opc connecons, you need to
understand how signal loss, aenuaon, and dispersion aect transmission. The MX10004 router uses
various types of network cables, including mulmode and single-mode ber-opc cables.
Signal Loss in Mulmode and Single-Mode Fiber-Opc Cables
Mulmode ber is large enough in diameter to allow rays of light to reect internally (bounce o the
walls of the ber). Interfaces with mulmode opcs typically use LEDs as light sources. However, LEDs
are not coherent light sources.
LEDs spray varying wavelengths of light into the mulmode ber, which reects the light at dierent
angles. Light rays travel in jagged lines through a mulmode ber, causing signal dispersion. Fiber
cladding consists of layers of lower-refracve index material in close contact with a core material of
higher-refracve index. When light traveling in the ber core radiates into the ber cladding, higher-
order mode loss occurs. Together, these factors reduce the transmission distance of mulmode ber
compared with that of single-mode ber.
Single-mode ber is so small in diameter that rays of light reect internally through one layer only.
Interfaces with single-mode opcs use lasers as light sources. Lasers generate a single wavelength of
light, which travels in a straight line through the single-mode ber. Compared with mulmode ber,
single-mode ber has a higher bandwidth and can carry signals for longer distances. It is consequently
more expensive.
For informaon about the maximum transmission distance and supported wavelength range for the
types of single-mode and mulmode ber-opc cables that are connected to the MX Series, see the
Juniper Networks Hardware Compability Tool. Exceeding the maximum transmission distances can
result in signicant signal loss, which causes unreliable transmission.
Aenuaon and Dispersion in Fiber-Opc Cables
An opcal data link funcons correctly if the modulated light reaching the receiver has enough power to
be demodulated correctly.
Aenuaon is the reducon in strength of the light signal during
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