Juniper EX4300 Series User Manual

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. EX Series switches use
various types of network cables, including mulmode and single-mode ber-opc cable.
Signal Loss in Mulmode and Single-Mode Fiber-Opc Cable
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. They 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. When light traveling in the ber core radiates into the ber), higher-order mode loss
(HOL) occurs. (Cladding consists of layers of lower-refracve index material in close contact with a core
material of higher refracve index.) Together, these factors reduce the transmission distance of
mulmode ber compared to 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 to mulmode ber, single-
mode ber has a higher bandwidth and can carry signals for longer distances. Single-mode ber is
consequently more expensive than mulmode ber.
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 Cable
An opcal data link funcons correctly provided that 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
transmission. Passive media components such as cables, cable splices, and connectors cause
aenuaon. Although aenuaon is signicantly lower for opcal ber than for other media, it sll
occurs in both mulmode and single-mode transmissions. An ecient opcal data link must transmit
enough light to overcome aenuaon.
Dispersion is the spreading of the signal over me. The following two types of dispersion can aect
signal transmission through an opcal data link:
• Chromac dispersion, which is the spreading of the signal over me caused by the dierent speeds
of light rays
• Modal dispersion, which is the spreading of the signal over me caused by the dierent propagaon
modes in the ber
For mulmode transmission, modal dispersion usually limits the maximum bit rate and link length.
Chromac dispersion or aenuaon is not a factor.
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Juniper EX4300 Series Specifications

General

Product Series	EX4300 Series
Power Consumption	Varies by model and configuration
Virtual Chassis Technology	Up to 10 switches
Software	Junos OS
Ports	24-port and 48-port models
10GBASE SFP+ Ports	Up to 8 ports
40GBASE QSFP+ Ports	2
Uplink Ports	Up to 4 ports
Jumbo Frames	Up to 9216 bytes
Operating Temperature	0°C to 45°C
Relative Humidity	5% to 90% noncondensing
Input Voltage	100 to 240V AC
Power Supply	AC or DC
Power Supply Options	AC or DC
Stacking	Yes
Layer 2 Features	Includes VLAN, STP, RSTP, MSTP, LACP
Layer 3 Features	OSPF, BGP
Management	CLI, Web GUI, SNMP
Security Features	DHCP snooping
QoS	8 queues per port, DSCP
Storage Temperature	-40°C to 70°C