Conclusion - Lightware UBEX Installation And Network Setup Manual

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2. Video Network Designing
10GBASE-ER Link-loss Calculation
When designing 10GBASE-ER links greater than 30 km (i.e., the cable is not already installed) a cabling
link-loss calculation, which is a simple arithmetic process, is used to make sure the combined loss of the
cabling components in the link does not exceed the 11 dB channel insertion loss allocated for 10GBASE-ER.
The cabling link-loss is calculated by adding the connector and splice loss to the cable loss. The cable
attenuation for the link is calculated by multiplying the link distance by the loss per unit distance specified
for the fiber (e.g., dB/km).
As shown in the table below (scenario 1) given a cable attenuation of 0.225 db/km, the cable attenuation for
a 40 km link is 9 dB (40 km x 0.225 = 9 dB). Assuming 2 dB for singlemode fiber connector and splice losses
the link-loss is 11 dB (9 dB + 2 dB = 11 dB); which is an allowable channel insertion loss for 10GBASE-ER
and would insure that this link can achieve 40 km. A similar calculation can be done for scenario 2 and 3.
Parameter
Channel insertion point
Required attenuation loss
Connector and splice loss
Maximum distance
10GBASE-ER link-loss calculation examples
12 This is the maximum fiber attenuation allowed for standerd single mode fiber at 1550 nm as per IEC 60793-2.
See the table in the Singlemode Fiber section for the details.
INFO: The 10BASE-E channel shall have attenuation between 5 and 11 dB. If required an attenuator can be
added to comply with this specification.
2.3.4. Conclusion
As with previous generations of Ethernet, 10 Gigabit Ethernet requires a network designer to thoroughly
understand the capabilities of his/her fiber infrastructure. With 10GbE new challenges and considerations
have emerged such as the effects of chromatic and polarization mode dispersion on signal integrity. In
addition, decisions may have to be made regarding whether to use singlemode or multimode fiber. This
paper has introduced some basic fiber related concepts and outlined some of the key points to understand
and consider when designing a 10 Gigabit Ethernet network.
DEFINITION: Polarization Mode Dispersion (PMD): Difference in propagation velocity between different optical
polarization states. An optical signal can be represented by two orthogonally polarized components,
each of which will travel at different velocities due to inherent geometric flaws in a length of optical
fiber. Since receivers used in optical communications do not discriminate between different polarization
states, the two delayed polarization components will be mixed at the receiving end. This mainly applies
to singlemode fiber.
Source: https://www.10gea.org/whitepapers/optical-fiber-and-10-gigabit-ethernet/
Scenario 1 Scenario 2
11 dB 11 dB
0.225 dB/km 0.225 dB/km 0.3 dB/km
2 dB 2 dB
40 km 35 km
Installation and Network Setup Guide for UBEX
Scenario 3
11 dB
12
2 dB
30 km
9