Signal Loss In Multimode And Single-Mode Fiber-Optic Cable For The Srx5400 Firewall; Attenuation And Dispersion In Fiber-Optic Cable For The Srx5400 Firewall - Juniper SRX5400 Hardware Manual

Table 41: Cable and Wire Specifications for Routing Engine Management and Alarm Interfaces
Port Cable Specification
Routing Engine RS-232 (EIA-232) serial
console or cable
auxiliary
interface
Routing Engine Category 5 cable or
Ethernet equivalent suitable for
interface 100Base-T operation
Signal Loss in Multimode and Single-Mode Fiber-Optic Cable for the
SRX5400 Firewall
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. LEDs are not
coherent sources, however. 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 to 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. It is consequently
more expensive.
Attenuation and Dispersion in Fiber-Optic Cable for the SRX5400
Firewall
Correct functioning of an optical data link depends on modulated light reaching the receiver with
enough power to be demodulated correctly.
Cable/Wire Supplied
One 6-ft (1.83-m) length
with RJ-45/DB-9
connectors
One 15-ft (4.57-m) length
with RJ-45/RJ-45
connectors
Attenuation is the reduction in power of the light signal as it
Maximum Routing Engine
Length Receptacle
6 ft (1.83 m) RJ-45 socket
328 ft (100 m) RJ-45
autosensing
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