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Annex C (informative) Noise reduction guidelines
This annex is informative only and is not part of this Standard.
C.1 General
The information found in the normative sections of this Standard
describe
telecommunications infrastructures that exhibit immunity to noise
in a typical commercial
building environment. This annex should be used as
a reference in those exceptional cases
where such a typical commercial building env
ironment does not exist, and noise is present
on the telecommunications infrastructure.
The existence of high levels of noise on power branch circuits (in the
form of surges, or
other signals with high frequency content) is an abnormal and
unacceptable condition for
operation of electrical equipment connected to the circuit. Under
such conditions, the typical
approach should be to identify, isolate or eliminate the potential
noise sources on power
branch circuits, or to suppress the noise signals using line
conditioners or surge protection.
In situations where these source
s or signals cannot be removed, the level of expected noise
signal should be determined and compared to the base levels
outlined in this annex to
determine the need for noise coupling reduction.
NOTE - Noise coupling from power br
anch circuits is not the only noise
source that may cause application errors. There are other sources
of noise,
and other factors that may cause errors or delays in applications.
C.2 Commercial building cabling configurations and noise coupling
conditions
The level of coupled noise is determined by:
a) the magnitude, duration and the frequency of noise transients
on the power cable;
b) the configuration of the power wire
s, whether loosely or tightly bundled;
c) the proximity of the cables to grounded metallic surfaces and
grounding conditions;
d) the cabling permanent link or channel length;
e) the coupled length between power and telecommunication cables;
f) the balance of the telecommunications cabling;
g) the separation between the power and telecommunications
cables.
The effect of the coupled noise on network operation is quantified
by the number of
incremental errors caused by exposure to the noise signals that do
not occur in the absence
of that noise. Tests confirmed error free operation under the
following conditions:
a) Separation between power and data lines by a non-metallic
barrier;
b) 500V peak to peak high frequency (EFT) noise signals on Power
cables;
c) Cable Balance LCL of 40 dB up to 30 MHz;
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d) 90m of coupled length between power and data cables;
e) Permanent link length of 90m or channel length of 100m;
f) The use of quality Network Interface Cards (NICs) with adequate
common mode
rejection.
It should be noted that the EFT testing using repetitive 500 V
pulses represents a worst
case condition that is unlikely to be encountered in commercial
office environments. If the
existing or expected noise environment does
not exceed the above conditions, no further
noise reduction considerations or actions are necessary.
C.3 Test configuration
The general test configuration is illustrated in figure 25.
Separation
Sending
Device
Receiving
Device
Load
EFT
Generator
Coupled length
Link length
Telecommunications cable
Power cable
Figure 25 – Test configuration for noise immunity measurements
For packet error rate measurements, the sending device in figure
25 is a packet generator
connected to a 1000BASE-T data switch and the receiving device
is either a PC with a
1000BASE-T NIC card or alternately another 1000BASE-T data
switch. For common mode
and differential mode noise measurements, the
receiving device is a digital oscilloscope.
The noise source on the power cable is Electrical Fast Transient
(EFT) burst generator per
IEC 61000-4-4 with a 5 ns rise time, 50 ns pulse duration, 15
ms bursts, 300 ms burst
period.
C.4 Test results
The test results are summarized in table 17 in a way that provides
the end user with an
indication of the relative effect of different variables on the noise
coupling between power
and telecommunications cables. The variables t
hat were studied include: the effect of pair
balance (LCL) characteristics when tested per TI
A/EIA 568-B.2-1, the effect of 1000BASE-T
network interface cards (NIC) from three different manufacturers,
the effect of different
coupled lengths, link lengths and pair separation distances as
illustrated in figure 25.
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Table 17 – Noise reduction factors under different test variables
Test Variable
Reduction Factor
Effect of cable balance
LCL/TCL > 40 dB from 1 to 30 MHz
1
LCL/TCL > 50 dB from 1 to 30 MHz
0.5
Effect of cable category
Category 5e
1
Category 6
0.5
NIC performance
Good
1
Poor
2
Effect of coupled length near equipment
Length = 90m
1
Length = 10m
1
Length < 2m
0.7
Effect of horizontal link length
Length = 90 m
1
Length = 60 m
0.7
Length = 40 m or less
0.6
Effect of separation distance
Zero (~ 6 mm)
1
1 inch (25 mm)
0.8
2 inch (50 mm)
0.6
3 inch (75 mm)
0.5
6 inch (150 mm)
0.3
Effect of Power Cabling
Unbundled power conductors
1.0
Bundled power conductors
0.7
NOTES
1
The noise reduction factor is the ra
tio of the relative noise immunity
between two different test conditions, as measured using a digital oscilloscope or
using packet error rate measurements.
2
As a reference benchmark (Reduction Factor = 1), a 500V EFT burst
pattern on the power cable (figure 25) is the threshold voltage level for the onset
of
errors under the following conditions:
- 90 meter link length between two 1000BASE-T Ethernet switch ports;
- Zero separation;
≥
10 meter coupling length; and,
- Category 5e cabling.
C.5 Summary
The empirical measurements contained in this
annex provide an indication of the relative
effect of different variables on the noise coupling between adjacent
telecommunications and
power cabling. One or more techniques can be
effective to mitigate the noise coupling from
power line transients. Some techniques that can be considered for
noise mitigation include:
1) qualification of the network interface card (NIC) for noise
immunity;
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2) compliance of cable and connecting hardware to LCL/TCL
recommendations in
TIA/EIA 568-B.2-1;
3) using category 6 cabling;
4) use of bundled or jacketed power conductors;
5) reduce coupled lengths near the equipment;
6) reduce link lengths
7) increase separation distance.
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ANNEX D (informative) Bibliography and references
This annex is informative only and is not part of this Standard.
This annex contains information on the doc
uments that are related to or have been
referenced in this document. Many of the documents are in print
and are distributed and
maintained by national or international standards organizations.
These documents can be
obtained through contact with the associated standards body or
designated representatives.
The applicable electrical code in the United States is the National
Electrical Code.
•
ANSI/ICEA S-80-576-2002 Category 1 & 2 Individually
Unshielded Twisted Pair Indoor
Cables (With Or Without An Overall Shield
) For Use In Communications Wiring Systems
Technical Requirements
•
ANSI/IEEE C2-2001 National Electrical Safety Code
•
ANSI/NFPA 70-1999 National Electrical Code
•
ANSI/TIA/EIA-598-B-2001 Optical Fiber Cable Color-coding
•
ANSI/ICEA S-87-640 - 1999 Standard for Optical Fiber Outside
Plant Communications
Cable
•
ANSI/ICEA S-83-596 - 2001 Standard for Fiber Optic Premises
Distribution Cable
•
ANSI/ICEA S-104-696 - 2001 Standard for Indoor-Outdoor
Optical fiber cable
•
IEC 60825 Safety of Laser Products
•
BICSI Telecommunications Distribution Methods Manual
•
BICSI Cabling Installation Manual
•
BICSI Customer-owned Outside Plant Methods Manual
The organizations listed below can be contacted to obtain reference
information.
ANSI
American National Standards Institute (ANSI)
11 W 42 St.
New York, NY 10032
USA
(212) 642-4900
www.ansi.org
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ASTM
American Society for Testing and Materials (ASTM)
100 Barr Harbor Drive
West Conshohocken, PA 19428-2959
USA
(610) 832-9500
www.astm.org
BICSI
BICSI, A Telecommunications Association
8610 Hidden River Parkway
Tampa, FL 33637-1000
USA
(800) 242-7405
www.bicsi.org
CSA
Canadian Standards Association International (CSA)
178 Rexdale Blvd.
Etobicoke, (Toronto), Ontario
Canada M9W 1R3
(416) 747-4363
www.csa-international.org
EIA
Electronic Industries Alliance (EIA)
2500 Wilson Blvd., Suite 400
Arlington, VA 22201-3836
USA
(703) 907-7500
www.eia.org
FCC
Federal Communications Commission (FCC)
Washington, DC 20554
USA
(301) 725-1585
www.fcc.org
Federal and Military Specifications
National Communications System (NCS)
Technology and Standards Division
701 South Court House Road
Arlington.VA 22204-2198
USA
(703) 607-6200
www.ncs.gov
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ICEA
Insulated Cable Engineers Association, Inc. (ICEA)
PO Box 1568
Carrolton, GA 30112
USA
www.icea.net
IEC
International Electrotechnical Commission (IEC)
Sales Department
PO Box 131
3 rue de Varembe
1211 Geneva 20
Switzerland
+41 22 34 01 50
www.iec.ch
IEEE
The Institute of Electrical and Electronic Engineers, Inc (IEEE)
IEEE Service Center
445 Hoes Ln., PO Box 1331
Piscataway, NJ 08855-1331
USA
(732) 981-0060
www.ieee.org
IPC
The Institute for Interconnecting and Packaging Electronic Circuits
2215 Sanders Rd.
Northbrook, IL 60062-6135
USA
(847) 509-9700
www.ipc.org
ISO
International Organization for Standardization (ISO)
1, Rue de Varembe
Case Postale 56
CH-1211 Geneva 20
Switzerland
+41 22 34 12 40
www.iso.ch
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NEMA
National Electrical Manufacturers Association (NEMA)
1300 N. 17th Street, Suite 1847
Rosslyn, VA 22209
USA
(703) 841-3200
www.nema.org
NFPA
National Fire Protection Association
Batterymarch Park
Quincy, MA 02269
USA
(617) 770-3000
www.nfpa.org
SCTE
Society of Cable Telecommunications Engineers
140 Philips Rd.
Exton, PA 19341-1318
USA
(800) 542-5040
www.scte.org
Telcordia Technologies (formerly Bellcore)
Telcordia Technologies Customer Service
8 Corporate Place Room 3C-183
Piscataway, NJ 08854-4156
USA
(800) 521-2673
www.telcordia.com
TIA
Telecommunications Industry Association (TIA)
2500 Wilson Blvd., Suite 300
Arlington, VA 22201-3836
USA
(703) 907-7700
www.tiaonline.org
UL
Underwriters Laboratories, Inc. (UL)
333 Pfingsten Road
Northbrook, IL 60062
USA
(312) 272-8800
www.ul.com