Testing Optical Fiber Links In Premises Networks

Testing Optical Fiber Links
In Premises Networks
Horizontal
Segment
B
A
Patch
Cord
Backbone
Segment
A
B
A
B
A
B
Optical Fiber Link
Testing Optical Fiber Links in Premises Networks — November 2001
1
Outline
•
•
•
•
•
•
Definitions — Segments, links, and channels
Polarity — Establishing continuity
Parameters — What should I test?
Standards — Which should I use?
Test Equipment — What do I need?
Test Procedures
–
–
–
–
Light source and power meter
Certification test set
OTDR
Troubleshooting
Testing Optical Fiber Links in Premises Networks — November 2001
2
Segments, Links,
and Channels
(TIA/EIA-568-B)
Testing Optical Fiber Links in Premises Networks — November 2001
3
(Duplex) Link Segment
Adapter
Connector
Splice
Optical
Fiber
Port
or
Jack
Port
Patch panel (in a crossconnect) or outlet (at the
work area)
Testing Optical Fiber Links in Premises Networks — November 2001
Patch panel
4
Horizontal and Backbone Link Segments
Horizontal
Segment
PC
Telecom
Outlet
Work Area
Backbone
Segment
Horizontal
Cross-connect
Splices
Telecom Room
Main
Cross-connect
Network
Equipment
Equipment Room
Testing Optical Fiber Links in Premises Networks — November 2001
5
Link
Link
Rx
Tx
PC
Telecom
Outlet
Work Area
Horizontal
Cross-connect
Splices
Telecom Room
Tx
Rx
Main
Cross-connect
Network
Equipment
Equipment Room
Testing Optical Fiber Links in Premises Networks — November 2001
6
Channel
Channel
Link
Rx
Tx
PC
Telecom
Outlet
Work Area
Horizontal
Cross-connect
Splices
Telecom Room
Tx
Rx
Main
Cross-connect
Network
Equipment
Equipment Room
Testing Optical Fiber Links in Premises Networks — November 2001
7
Do You Certify Links or Channels?
• Patch cords contribute negligible fiber loss.
• Using the proper (one reference jumper)
method, link attenuation measurements
include the loss of the near-end and far-end
connections.
• Therefore you always certify links (not
channels) in premises fiber optic networks
Testing Optical Fiber Links in Premises Networks — November 2001
8
Polarity
(TIA/EIA-568-B)
Testing Optical Fiber Links in Premises Networks — November 2001
9
Polarity Rules
1. Simplex adapters in patch panels and outlets
must be alternately labeled “A” and “B”
2. Duplex connectors, adapters, plugs and
jacks must have a defined “A” and “B” side.
3. Link segments and duplex patch cords must
connect A to B and B to A.
Testing Optical Fiber Links in Premises Networks — November 2001
10
Simplex Connectors and Adapters
Transceiver
Simplex
patch cords
A
Rx
Link Segment
Tx
B
B
A
A
B
Patch Panel
Patch Panel
Duplex Connectors and Adapters
Transceiver
A
Rx
Tx
B
A
B
Duplex
patch cord
Link Segment
B
B
A
A
A
B
Patch Panel
Testing Optical Fiber Links in Premises Networks — November 2001
Patch Panel
11
Maintaining Simplex Connector Polarity
By Labeling
Fibers are connected
straight-through
(1 to 1, 2 to 2, etc.)
12-fiber cable
Patch panels
(top view)
Label
B A B A B A B A B A B A
Label
A B A B A B A B A B A B
Fiber
1
Fiber
1
2
3
4
5
6
7
8
9 10 11 12
Testing Optical Fiber Links in Premises Networks — November 2001
2
3
4
5
6
7
Patch Panel
8
9 10 11 12
12
Maintaining Simplex Connector Polarity
By Reverse-Pair Positioning
Fibers in each pair
are reversed
(1 to 2, 2 to 1, etc.)
12-fiber cable
Patch panels
(top view)
Label
B A B A B A B A B A B A
Label
B A B A B A B A B A B A
Fiber
1
Fiber
2
2
3
4
5
6
7
8
9 10 11 12
1
Swap
Testing Optical Fiber Links in Premises Networks — November 2001
4
3
Swap
6
5
Swap
8
7 10 9 12 11
Swap
Patch Panel
Swap
Swap
13
Duplex Connectors
(Same as simplex connector reverse-pair positioning)
Fibers in each pair are
reversed in order to
connect opposite sides in
corresponding connectors.
12-fiber cable
Patch panels
(top view)
Side
BA BA BA B A B A B A
Side
BA BA BA BA
Fiber
1 2
3 4
5 6
Fiber
2 1
4 3
6 5
Port
1
2
3
Port
1
2
3
7 8 9 10 11 12
4
5
6
Testing Optical Fiber Links in Premises Networks — November 2001
BA
BA
8 7 10 9 12 11
4
5
6
14
Polarity Example — MT-RJ Link
Horizontal segment
Equipment
Tx
Rx
A
B
B
Outlet
A
B
Cross-connect
A
B
A
Backbone segment
A
B
B
A
Patch cord
B
B
A
A
Patch cord
Equipment
Tx
Cross-connect
B
B
A
Rx
A
B
A
B
A
Plug/
Duplex Connector
Jack/
Duplex Adapter
(rear view)
(front view)
B
A
Testing Optical Fiber Links in Premises Networks — November 2001
B
A
Patch cord
15
Input and Outputs
When looking at the end-face of any duplex fiber optic plug
with tab up, or the front of any jack with keyway up, the
output is on the left and the input is on the right.
MT-RJ Jack or Panel Port
MT-RJ Plug
(Front view, with keyway up)
(Front view, with key up)
B
(jack output)
A
(jack input)
A
(plug output)
Testing Optical Fiber Links in Premises Networks — November 2001
B
(plug input)
16
Parameters
Testing Optical Fiber Links in Premises Networks — November 2001
17
Typical Fiber Optic Field Measurements
• Link Certification
–
–
–
–
Polarity
Insertion loss
Length
OTDR trace (very useful but not required)
• Troubleshooting
–
–
–
–
Equipment output power
Link insertion loss
Link continuity (flash light or red laser)
Link fault-locating (red laser or OTDR)
Testing Optical Fiber Links in Premises Networks — November 2001
18
What Is Not Typically Measured in the Field
• Bandwidth — not impacted by installation
practices (but very important fiber spec.)
• Optical Return Loss — (reflection) does not
significantly impact current generation LAN
transceivers (but this may change in the future
with 10X Gigabit Ethernet).
• Cross-talk — not a problem in premises fiber
networks!
Testing Optical Fiber Links in Premises Networks — November 2001
19
Power and Insertion Loss —
What You Really Need to Know
• Power is normally expressed in dBm:
PdBm = “dB relative to one milliwatt” = 10 log10 (Pwatts /1 mW)
• Insertion loss or Attenuation in dB is the difference
between input and output power, when both powers are
expressed in dBm.
• Attenuation specifications of optical fiber are often
expressed in dB/km.
• The insertion loss of passive components, such as
optical fibers and connectors, is always positive.
Testing Optical Fiber Links in Premises Networks — November 2001
20
Visualizing dB loss:
PIN = 1
POUT
1
0.79
0.5
0.1
Loss = 0 dB
1 dB
3 dB
10 dB
0.01
20 dB
Each additional 10 dB of loss means output is reduced by an
additional factor of 10, so 30 dB è 0.001, 40 dB è 0.0001 etc.
Testing Optical Fiber Links in Premises Networks — November 2001
21
Fiber Insertion Loss Example
PIN = - 20 dBm
POUT = - 23 dBm
1 km of optical fiber
Insertion Loss
= PIN - POUT
= -20 dBm - (-23) dBm
= 3 dB
Attenuation
= 3 dB/km.
Testing Optical Fiber Links in Premises Networks — November 2001
22
Connection Insertion Loss Example
PIN = - 20 dBm
POUT = - 20.75 dBm
Optical Fiber Connection
(mated connector pair)
Insertion Loss
= PIN - POUT
= -20 dBm - (-20.75) dBm
= 0.75 dB
Testing Optical Fiber Links in Premises Networks — November 2001
23
Standards
Testing Optical Fiber Links in Premises Networks — November 2001
24
Fiberoptic Standards
• There are two types of fiber optic standards:
Cabling Standards
Application Standards
such as:
such as:
TIA/EIA-568-B* (N. America)
ISO 11801 (International)
EN 50173 (European)
10Base-FL
100Base-FX
FDDI
ATM
Fibre Channel
1000Base-SX and LX
* Replaced TIA/EIA-568-A in 2001.
Testing Optical Fiber Links in Premises Networks — November 2001
25
Fiber Optic Standards (cont.)
• Cabling standards specify:
–
–
–
–
Maximum attenuation per km of fiber
Maximum insertion loss per connection
Maximum insertion loss per splice
Maximum length for link segments and links
• Application standards specify:
– Minimum fiber bandwidth
– Maximum end-to-end link attenuation
– Maximum link length
Testing Optical Fiber Links in Premises Networks — November 2001
26
TIA/EIA-568-B Backbone Rules
• Max dB/connection (mated pair) :
• Max dB/splice (fusion or mechanical) :
• Multimode:
– Max. Length*:
– Test wavelengths
– Test direction:
0.75 dB
0.30 dB
2 km
850 and 1300 nm
at least one
• Singlemode:
– Max. Length*:
– Test wavelengths:
– Test direction:
*
**
3 km **
1310 and 1550 nm
at least one
Other limits apply for defined sections of backbone segments
Singlemode fiber links > 3 km can of course exist, but are
considered “outside the scope” of TIA-568-B
Testing Optical Fiber Links in Premises Networks — November 2001
27
TIA/EIA-568-B Backbone Rules — Fiber Loss
Optical fiber
cable type
Wavelength
(nm)
850
Maximum Attenuation
(dB/km)
3.5
1300
1.5
850
3.5
1300
1.5
Singlemode
inside plant
1310
1.0
1550
1.0
Singlemode
outside plant
1310
0.5
1550
0.5
50/125 µ m
(multimode)
62.5/125 µ m
(multimode)
Testing Optical Fiber Links in Premises Networks — November 2001
28
TIA/EIA-568-B Backbone Rules (Example)
0.75 dB
0.75 dB
Patch cord
0.30 dB
0.75 dB
Patch
cord
500 m
Maximum IL = 500 m x 3.5 dB/km + 3 x 0.75 dB + 0.3 dB
= 1.75 dB + 2.25 dB + 0.3 dB
= 4.3 dB
Testing Optical Fiber Links in Premises Networks — November 2001
29
TIA/EIA-568-B Horizontal Rules
• Total insertion loss
• Total insertion loss with a
consolidation point
• Length:
2.0 dB
2.75 dB
90 m
SIMPLE !
Testing Optical Fiber Links in Premises Networks — November 2001
30
(Some) Application Rules
(From Table E.1, TIA/EIA-568-B.1)
Application
WaveLength
(nm)
Maximum Supportable Distance
(m)
62.5 µ m
50 µ m
Singlemode
Maximum Channel Attenuation
(dB)
62.5 µ m
50 µ m
Singlemode
10BASE-FL
850
2000
NST
12.5
7.8
NST
Token Ring 4/16
850
2000
NST
13.0
8.3
NST
100 VG-AnyLAN
1300
850
2000
500
NST
-
7.0
7.5
2.3
2.8
NST
-
100BASE-FX
(Fast Ethernet)
1300
2000
NST
11.0
6.3
NST
FDDI (low cost)
1300
500
NST
7.0
2.3
NST
FDDI (original)
1300
2000
40 k
11.0
6.3
10 to 32
50
155
155
622
622
1300
1300
850
1300
850
3000
2000
1000
500
300
15 k
15 k
15 k
-
10.0
10.0
7.2
6.0
4.0
5.3
5.3
7.2
1.3
4.0
7 to 12
7 to 12
7 to 12
-
266
266
1062
1062
1300
850
850
1300
1500
700
300
-
1500
200
500
-
10 k
10 k
6.0
12.0
4.0
-
5.5
12.0
4.0
6 to 14
6 to 14
1000BASE-SX
(Gigabit Ethernet)
850
220
550
-
3.2
3.9
-
1000BASE-LX
(Gigabit Ethernet)
1300
550
550
5k
4.0
3.5
4.7
ATM
Fibre
Channel
“NST” = non-standard, that is not supported by TIA/EIA-568-B, but converters may allow use on standard media
Testing Optical Fiber Links in Premises Networks — November 2001
(NOT SO SIMPLE)
31
Which standard(s) should I use?
• In general, every optical fiber link must meet the
requirements of TIA/EIA-568-B and those of the
application(s) it must support.
• TIA/EIA-568-B requirements ensure workmanship and component quality.
• Application standards ensure system operation.
Testing Optical Fiber Links in Premises Networks — November 2001
32
Test Equipment
Testing Optical Fiber Links in Premises Networks — November 2001
33
Basic Test Kit
• LED light source and Optical Power Meter
– Dual wavelength LED source required to measure insertion loss on
multimode links at 850 and 1300 nm
– Also can measure insertion loss on singlemode links at 1300 nm
– Power meter can also measure equipment output power.
– Noyes OLS 1-Dual + OPM 4 or 5 optical power meters
• Microscope
– Inspect fiber optic connector polish and cleanliness
– At least 200x recommended
– Noyes OFS 300 optical scope; VFS1 video scope
• Flashlight
– Trace multimode fibers (check for continuity)
– Not useful on singlemode fiber
Testing Optical Fiber Links in Premises Networks — November 2001
34
Additional Test Equipment
• Certification Test Set
–
–
–
–
Measures loss and length of duplex fiber links.
Provides PASS/FAIL results based on standards
Faster than a standard light source/power meter.
Noyes T410 for multimode and T420 for singlemode
• OTDR (Optical Time-Domain Reflectometer)
– Only way to measure loss and reflectance of “events” (connections,
splices, faults).
– Only practical way to fault locate buried or hidden cables.
– Can generate “baseline traces” to help resolve call-backs and for
later troubleshooting.
– Should not be used in place of a certification test set, or light source
and power meter, for link certification.
– Noyes M600 multimode, singlemode, and “quad” models
Testing Optical Fiber Links in Premises Networks — November 2001
35
Additional Test Equipment (cont.)
• Visual Fault Identifier (VFI)
– Operates at about 650 nm; visible (red) laser source
– Short-range fault locator (to several hundred meters)
• Locate breaks and bends in multimode patch cords and cables
• Locate bends (singlemode only)
– Can trace multimode fibers to about 2 km and singlemode fibers to
about 5 km.
– Noyes HiLite and VFI 2
• 1310/1550 nm Laser Source
– Used with standard optical power meter to certify singlemode links at
1310 and 1550 nm.
– Noyes OLS 2-Dual
Testing Optical Fiber Links in Premises Networks — November 2001
36
Test Procedures
Testing Optical Fiber Links in Premises Networks — November 2001
37
Three Keys to Measuring
Insertion Loss Accurately
1. Use a light source that meets TIA requirements
– Multimode — 850/1300 nm LED with a mandrel wrap
on the transmit jumper.
– Singlemode — 1310*/1550 nm laser
2. Use clean, high-quality test jumpers
– Same fiber type as the link you are testing
(50 µm, 62.5 µm, or singlemode).
– Durable connectors (many insertions/day)
– Keep your test jumper connectors clean!
3. Use the one reference jumper method
* You can also use a 1300 nm LED with a singlemode transmit jumper.
Testing Optical Fiber Links in Premises Networks — November 2001
38
Three Basic Steps In Making
an Insertion Loss Measurement
1. Set the reference for each test wavelength
– Use one jumper method
2. Check your jumpers
– Use an adapter to connect transmit and receive jumpers
– Do NOT remove transmit jumper from light source
– Acceptable loss is about 0.4 dB for one connection …
but this depends on connector type
3. Measure link insertion loss
– Save results in the power meter so they can be
transferred to a PC for archiving and printing.
Testing Optical Fiber Links in Premises Networks — November 2001
39
One Reference Jumper Method
Mandrel (for LED sources)
Tx jumper
Adapter
Tx jumper
Tx
Rx
Rx jumper
Tx
0 dB
Light Source Optical Power
Meter
1) Set reference
Rx
0.4 dB
Light Source
Optical Power
Meter
2) Check jumpers
Testing Optical Fiber Links in Premises Networks — November 2001
40
3) Measure insertion loss
Horizontal
Patch Panel
B
-20 dBm
Outlet
A
Tx
Light Source
Horizontal
Segment
A
B
B
A
Splice
Main
Patch Panel -22 dBm
A
B
Backbone
Segment
Loss at the test
wavelength is 2 dB
Testing Optical Fiber Links in Premises Networks — November 2001
Rx
2 dB
Optical Power
Meter
41
Using a Certification Test Set
• Same basic steps as the light source and
power meter procedure.
• But MUCH FASTER since links are tested
two fibers and two wavelengths at at time.
• Certification test sets also measure length.
• Therefore they can calculate PASS/FAIL
results based on TIA-568-B or application
standards.
Testing Optical Fiber Links in Premises Networks — November 2001
42
One Reference Jumper Method
Mandrels (for LED sources)
Main
Tx Jumper
Rx
Remote
Tx Jumper
Tx
Rx
Tx
Adapters
Main
Rx Jumper
Rx
Rx
Tx
0.4 dBm
0 dBm
Main Unit
Tx
Remote
Rx Jumper
Remote Unit
1) Set reference
Main Unit
Remote Unit
2) Check jumpers
Testing Optical Fiber Links in Premises Networks — November 2001
43
3) Certify (Loss + Length)
-23 dBm
Outlet
-20 dBm
B
Horizontal
Patch Panel
A
Rx
Tx
3 dB 2
240 m
PASS
Horizontal
Segment
A
B
B
A
Main
Patch Panel
Splice
-20 dBm
-22 dBm
A
B
Backbone
Segment
Rx
Tx
At the test wavelength, loss on
the “red” fiber is 2 dB while loss
on the “green” fiber is 3 dB
Main Unit
Testing Optical Fiber Links in Premises Networks — November 2001
Remote Unit
44
Using an OTDR
To Generate a Baseline Trace
• You must use a launch cable to measure the loss of the
near-end connection.
• You must use a receive cable to measure the loss of the
far-end connection.
• Both cables must use the same type fiber (50 µm, 62.5 µ m,
or singlemode) as the link under test.
• For testing links under 2 km, both cables should be about
75 to 100 m long.
• Set wavelength, pulse width, distance range, number of
averages, etc. manually, or use automatic setup features of
your OTDR.
Testing Optical Fiber Links in Premises Networks — November 2001
45
Using an OTDR
(to generate a baseline trace)
Work Area
Outlet
Horizontal
Patch Panel
B
A
B
A
B
A
Horizontal
Segment
MM
Launch
Cable
(Fiber Box)
Main
Patch Panel
Splice
A
B
Backbone
Segment
SM
Receive
Cable
(Fiber box)
OTDR
Testing Optical Fiber Links in Premises Networks — November 2001
46
Reading an OTDR Trace
Link Length
(≈ 130 m)
Curser A
Cursor B
0
One Connection
(Loss ≈ 0.4 dB)
-1
One Connection
(Loss ≈ 0.4 dB)
Relative
Power
(dB)
-2
Two Connections
(Loss ≈ 0.8 dB)
-3
Splice
(Loss ≈ 0.1 dB)
Launch
Cable
-4
Horiz.
Seg.
Backbone
Segment
Link Loss
(≈ 2.1 dB)
Trace
Rcv.
Cable
-5
0
50
100
150
200
250
Distance (m)
Testing Optical Fiber Links in Premises Networks — November 2001
47
Troubleshooting a failed fiber link
• Measure equipment output power.
• Verify connectivity using a visual fault
identifier (also called a VFI or red laser).
• Fault-locate using an OTDR:
– Generate a trace.
– Look for breaks, or events with excessive loss
– Compare with baseline trace if available
Testing Optical Fiber Links in Premises Networks — November 2001
48
Example Fault:
(Fiber break)
Rx
Tx
PC
Telecom
Outlet
Work Area
Link Failure
Alarm !
Horizontal
Cross-connect
Telecom Room
Tx
Broken fiber
Rx
Main
Cross-connect
Network
Equipment
Equipment Room
Testing Optical Fiber Links in Premises Networks — November 2001
49
- 8 dBm
Optical
Power Meter
(OPM)
Measure Transmitter
Output Level
(Using an Optical
Power Meter)
Rx
Tx
PC
Telecom
Outlet
Work Area
Horizontal
Cross-connect
Telecom Room
Equipment output level
look okay.
Tx
Rx
Main
Cross-connect
Network
Equipment
Equipment Room
Testing Optical Fiber Links in Premises Networks — November 2001
50
Verify Connectivity
(Using a VFI or “red laser”)
PC
Telecom
Outlet
Work Area
Horizontal
Cross-connect
Telecom Room
Visual Fault
Identifier
(VFI)
The VFI cannot locate
the fiber break because it
is inside a conduit but it
confirms there is a break
because no light is seen
at link output.
Testing Optical Fiber Links in Premises Networks — November 2001
Main
Cross-connect
Network
Equipment
Equipment Room
51
Fault-Locate
Work Area
PC
(Using an OTDR)
Horizontal
Cross-connect
Telecom
Outlet
Telecom Room
Receive Cable
MM
Main
Cross-connect
Launch
Cable
Network
Equipment
Equipment Room
OTDR
Testing Optical Fiber Links in Premises Networks — November 2001
52
OTDR Trace Showing Break at 120 m
A
Distance to fault
(≈ 120 m)
B
0
-1
Fault !
Baseline
Trace
-2
Relative
Power
(dB)
-3
New Trace
-4
-5
0
50
100
150
200
250
Distance (m)
Testing Optical Fiber Links in Premises Networks — November 2001
53
Light sources for testing multimode links
• To measure attenuation on 50 or 62.5 µm
multimode fiber links, TIA-568-B requires the use
of an overfilled light source, such as an LED, with a
mandrel-wrap on the transmit jumper.
• VCSEL and laser sources do not meet TIA-568-B
requirements.
Mandrel-wrap
850 nm VCSEL
1300 nm Laser
850/1300 nm LED
Testing Optical Fiber Links in Premises Networks — November 2001
ü
54
LED Source without Mandrel Wrap
LED source with no mode filter
High-loss modes
will not pass through
bends or connectors.
Core
Cladding
“Standard” modes
“High-loss” modes
Testing Optical Fiber Links in Premises Networks — November 2001
55
LED Source with Mandrel Wrap
LED source with mandrel wrap
Core
Cladding
A mandrel-wrapped
LED source provides
the correct modes for
insertion loss testing.
Testing Optical Fiber Links in Premises Networks — November 2001
56
TIA-568-B Mandrel Wrap Specifications
TIA-568-B requirement is to wrap the Tx jumper 5 times
around a mandrel (rod) with the following diameter:
Diameter (D)
Fiber Type
50 µ m
62.5 µ m
Bare Fiber
25 mm (1.0 in)
20 mm (0.8 in)
3 mm Jacket
22 mm (0.9 in)
17 mm (0.7 in)
D
5 wraps
Tx jumper
Mandrel
Testing Optical Fiber Links in Premises Networks — November 2001
57
Example: Testing a 50 µ m 1000Base SX Link
Without a Mandrel Wrap
50 µm Link
- 21 dBm
B
A
B
A
A
B
A
B
-25 dBm
Rx
Tx
850 nm
LED Source
4.0 dB
Measured loss at 850 nm
is 4.0 dB, 0.1 dB over
1000Base SX limits.
Testing Optical Fiber Links in Premises Networks — November 2001
Optical Power
Meter
58
Example: Testing a 50 µ m 1000Base SX Link
With a Mandrel Wrap
50 µm Link
- 23 dBm
B
A
B
A
A
B
A
B
-26.1 dBm
Rx
Tx
850 nm
LED Source
3.1 dB
Actual loss at 850 nm
is 3.1 dB, 0.8 dB under
1000Base SX limits.
Testing Optical Fiber Links in Premises Networks — November 2001
Optical Power
Meter
59
Questions?
www.noyes-fiber.com
800-321-5298
Testing Optical Fiber Links in Premises Networks — November 2001
60
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