Uploaded by samadpour

exfo reference-poster cwdm-dwdm1 en

advertisement
CWDM Networks Reference Poster
CWDM/DWDM
Standards
REFERENCE POSTER
CWDM Testing
CWDM Characteristics
• Affordable alternative for bandwidth increase
• Limited maximum distance
• Can be easily overlaid on existing infrastructure
• Typical transmitter output power : 5 dBm
Future of CWDM Networks
Construction/Fiber
Qualification
Test
Test Instrument
Connector cleanliness according
to IEC and IPC standards
Inspection probe with automatic
pass/fail analysis software
ORL measurement
ORL testers, OTDR
Fiber, connector,
splice loss
CWDM OTDR
Channel power and
wavelength check
Channel analyzer,
CWDM-calibrated power meter
Wavelength assignment testing
CWDM OTDR, channel analyzer
Turn-Up and
Provisioning
Maintenance and
Troubleshooting
Future of CWDM Networks: Hybrid Networks or DWDM over CWDM
CWDM WL
1470 nm
1490 nm
1510 nm
1530 nm
1550 nm
1570 nm
1590 nm
1610 nm
• Typical signal power at receiver : > -25 dBm
ITU-T G. 694.2—Spectral Grids for WDM Applications: CWDM Wavelength Grid
• 18 wavelengths defined by ITU-T, though usually only 8 or 16 are used
DWDM WL
• Transmitter drift tolerance: ±6-7 nm
• Channel spacing: 20 nm
• Increase network capacity by replacing a CWDM card by a DWDM card
• Single CWDM channel now supports 8 or 16 wavelengths
Channel Number
Central Wavelength (nm)
1
1271
2
1291
3
1311
4
1331
5
1351
6
1371
7
1391
8
1411
1431
1451
11
1471
12
1491
13
1511
14
1531
15
1551
16
1571
17
1591
18
1611
• No amplification = no noise = no need to measure optical signal-to-noise ratio (OSNR)
Channel analyzer, OSA
Is Your Network CWDM-Ready?
In most CWDM networks, C-band and L-band are used where attenuation is pretty flat with wavelength. If more than
eight wavelengths are required, the S-band must be used where attenuation varies a lot, around the water peak at
1383 nm. Therefore, an appreciation of spectral loss is required. By utilizing an OTDR with four wavelengths including
1383 nm, a simple calculation yields the loss across the whole CWDM range.
• Spectral testing: channel analyzers won’t work. Basic optical spectrum analyzers (OSAs)
without OSNR capabilities can analyze both CWDM and unamplified DWDM wavelengths
without the extra cost of full OSAs. Basic OSAs provide the best fit for the technician to
test DWDM over CWDM.
CWDM Testing with iOLM
0.6
Calculated Fiber Spectral Attenuation
0.5
Attenuation (dB/km)
9
10
Channel wavelength,
power drift testing
Using a multipulse approach to ensure maximum accuracy, the iOLM enables any technician
to test individual CWDM channels at the touch of one button.
Measured Fiber Losses by an OTDR
0.4
A
Pos.
0.3
0,0000
Len.
Link ORL:
0.0
1250
Fiber Attenuation (dB/km)
O-Band
1260-1360
E-Band
1360-1460
2.0
C-Band L-Band
S-Band
1530- 15651460-1530
1565
1625
Water Peak
1.5
1270 1290 1310 1330 1350 1370
1390
1300
1350
1400
1450
1500
Wavelength (nm)
1550
1600
Head-End/CO
40.00
0.5
1
OADM
1530 nm
10
20
30
40
50
60
70
1600
Wavelength (nm)
5,1338
5,0547
10,534
km
Global pass/fail status
19,684 dB
32,50 dB
Pass
3
25.00
1500
5,2818
Connectors are key components that interconnect all network elements. This is why maintaining
them is essential to ensuring that the equipment will operate at maximum performance and
catastrophic network failures will be avoided.
OADM
1550 nm
30.00
ITU-T G.652 Fibre
25,265
1610 nm
Properly inspecting a fiber-optic cable can prevent a slew of problems, saving you time,
money and pains.
45.00
1410 1430
1450 1470 1490
1610
1510 1530 1550 1570 1590
1400
76,4 km
65,962
‘AN OUNCE OF PREVENTION IS WORTH A POUND OF CURE’
2
1300
60,908
Fiber Connector Inspection
CWDM Testing: CWDM OTDR
35.00
1200
55,774
1650
Calculated fiber spectral attenuation from model.
1.0
0.0
50,492
25,227
iOLM
Link loss:
ITU-T G. 652—Characteristics of a Singlemode Fiber and Cable
2.5
25,227
A
0.2
0.1
3.0
81,393 km
B
80
Common Connector Issues
1470 nm
1490 nm
EXFO Headquarters
Tel.: +1 418 683-0211
Toll-free: +1 800 663-3936 (USA and Canada)
Fax: +1 418 683-2170
info@EXFO.com
www.EXFO.com
1510 nm
ITU-T G.695—CWDM Optical Interfaces
Dust/dirt residue
• Provides optical parameter values for physical layer interfaces of CWDM applications
with up to 16 channels and up to 10 Gbit/s
EXFO serves over 2000 customers in more
than 100 countries. To find your local office contact
details, please go to www.EXFO.com/contact.
© 2012 EXFO Inc. All rights reserved. Printed in Canada
1530 nm
20120640
Oily residue
Dirty/damaged connector
Connector Inspection and Maintenance Solutions
FTB-200
12/11
Wet residue
SAP1064097
OTDR trace showing the effects of the 1550 nm wavelength going through different OADMs.
CWDM Testing: Spectral Analysis
Topologies
Connector Cleaning
Supplies
Fiber Inspection
Probe and Display
Fiber Inspection Probe
on FTB Platform
Connector Endface
Analysis Software
• Dry cleaning supplies
• Inspects male and female
connectors
• Uses the platform screen;
no need for additional display
• Delivers clear-cut pass/fail
verdict
• Very secure, no direct eye
exposure to laser radiations
• Stores images for future
reference
• Guarantees a uniform level
of acceptance (IEC and
IPC standards-compliant)
• Wet cleaning supplies
• Cleaning kits
Residential/Subdivisions
Enterprise
• Performs automated image
analysis (when paired with
analysis software)
Cell Tower
Where to Inspect/Clean
The following items should always be on your
inspection/cleaning list:
(R)OADM
• Patch panel (e.g., splitter cabinet)
(R)OADM
Splitter
Head-End/CO
• Test jumpers
OSA trace of a four-CWDM channels.
• Cable connectors
Patch panel inspection.
(R)OADM
DWDM
Backbone
When to Clean
(R)OADM
CWDM MUX/DMUX
CWDM Channel
Add/Drop
CWDM Channel
Add/Drop
The very first step is connector inspection. This applies to all testing phases–construction,
activation and maintenance. Connectors should be cleaned only if the inspection reveals
that they are dirty.
CWDM Channel
Add/Drop
How to Clean a Single Fiber Connector
with a Dry-Cleaning Method
Each customer (enterprise or tower) receives a wavelength via an add/drop multiplexer (OADM).
Scan and watch the video (EXFO.com/Connector2)
Channel power for each CWDM wavelength measured with a channel analyzer.
DWDM Networks Reference Poster
Standards
DWDM Dispersion Testing
Network Topology
• Dispersion is an important phenomenon that must be tested in DWDM networks
to avoid bit errors. The longer the light path, the more dispersion there is.
DWDM Characteristics
• Best approach to maximize fiber capacity
λλ1
1
• EXFO recommends dispersion testing for fiber span longer than 20 km.
• Extensively used in metro, long-haul and ultra-long-haul networks
λλ2
2
T1 Voice
ITU-T G. 694.1—Spectral Grids for WDM Applications: DWDM Frequency Grid
• Defines specific wavelengths (frequencies) allowed for 12.5 GHz, 25 GHz, 50 GHz
and 100 GHz channel spacing
Channel Spacing (GHz)
Allowed Channel
Frequencies (THz)
12.5
193.1 + n*0.0125
25
193.1 + n*0.025
50
193.1 + n*0.05
100
193.1 + n*0.1
Chromatic Dispersion (CD)
λ3
T1/T3 PL
SONET/SDH
ATM
Chromatic dispersion is a pulse broadening that occurs
when different wavelengths of an optical pulse travel at
different velocities in a fiber due to the variation of the fiber
index of refraction with wavelength.
DCM
Ethernet
Ethernet
OADM
OTN/G.709
Bidirectional
Multiwavelength
Optical Amplifier
ESCON
FC
(n is a positive or negative integer including zero)
Wavelength
Services
Polarization Mode Dispersion (PMD)
T0
T
Frequency (GHz)
DCD
WDM
t
PMD is a pulse broadening that occurs when different
polarization modes (fast axis and slow axis) travel at
different velocities due to fiber geometric imperfections or
environmental constraints (heat, mechanical stress on the
fiber like bends, etc.). PMD leads to differential group delay
(DGD).
2.9979 x 108
Wavelength (nm) =
Building Blocks/Components of a WDM Network
DWDM
Multiplexer/Demultiplexer
λ1
λ2
2
Δt
DCM = Dispersion Compensating Module
OADM = Optical Add/Drop Multiplexer
λ3
fast axis
z, t
Channel Spacing Conversion
GHz
200
100
50
25
12.5
nm
1.6
0.8
0.4
0.2
0.1
slow axis
DGD
Optical Transport Network (OTN)
How to Handle High PMD
OAM&P
CO
ITU-T G.650.3—Test Methods for Installed Singlemode Optical Fiber
Cable Links
Transparency
CO
Splice loss, splice location, fiber
uniformity and cable length
OTDR
Polarization mode dispersion
PMD tester
rn
he
Et
2 km
80 km
Scalable Up to 100G
FE
C
80 km
he
rn
et
Core Network
OTN/DWDM
Et
ORL tester
CO
Good section (acceptable)
Bad section (must be replaced)
ITU G.709 defines a stronger forward error correction for OTN, which can result
in up to 6.2 dB improvement in signal-to-noise ratio (SNR).
C
CD tester
Optical return loss
CO
FE
Chromatic dispersion
Frequency
Test Instrument
Attenuation
High
OTDR, OLTS, probes, OSA
Optical channel power changes
due to gain variations
High
OSA
Frequency (or wavelength)
deviation from normal
High
OSA
et
rn
he
Et
10-1
10-2
10-3
10-4
Et
he
rn
et
Impairment
FE
Common Failures in DWDM Networks
Distributed PMD analysis breaks down the measurement results,
effectively pinpointing the high-contributing sections of the link.
C
Traditional PMD measurement techniques provide a total link PMD value
but do not locate which spans are causing the link to fail the test.
10
-6
Medium
PMD tester, distributed PMD tester
Four-wave mixing
Medium
OSA
• Locates the fiber sections that are the main contributors of the total PMD of a link
Amplified spontaneous emission
noise from optical amplifier
Medium
OSA
• Enables to isolate and repair only the worst PMD sections of the fiber cable and allows
the cost-effective upgrade of a fiber network
Chromatic dispersion, CD slope
Medium
CD tester
10-10
Reflection
Medium
OLTS, OTDR, probe
10-11
Laser noise
Medium
OSA
10-12
Interchannel crosstalk
Medium
OSA
10-13
Interferometric crosstalk
Medium
OSA
10-14
10-7
BER
G.709
10-8
10-9
10-15
2
EXFO recommendation
Source: Recommendation ITU-T G. 697. Optical Monitoring for DWDM Systems, Table 1—Optical Impairments.
Uncorrected
10-5
Polarization mode dispersion
High = 10 events per year
Medium = 1 event per year
Integrated Solution
C
OTDR
FE
Link attenuation
1 km
et
Inspection probe
rn
Test Instrument
he
Recommended Tests
Connector endface inspection
FEC
et
Core Network
OTN/DWDM
• Detailed tests should be carried out on a singlemode fiber for proper operation
Et
DWDM Testing
5.86 dB
6.2 dB
3
4
5
6
7
High-contributing PMD section.
8
9
Eb/No
10
11
12
13
14
15
BER vs Eb/No
DWDM Spectral Testing
• Spectral testing with an optical spectrum analyzer (OSA) is key to identifying many
common types of failures in DWDM networks, as shown in the following table:
Importance of OSNR
Definition of Optical Signal-to-Noise Ratio (OSNR)
Lower
Bit Error
Rate
Higher
OSNR
Higher
Quality of
Service
Less Errors
in
Transmission
IEC Method and (R)OADMs
IEC Method and 40G Signals
• IEC method fails for signals that went through (R)OADMs
• IEC method fails for 40G signals
• It leads to an underestimation of the noise level
• It leads to an overestimation of the noise level
-5
CWDM
-40
-10
Signal
-45
OSNR vs. BER Typical Relationship
dBm
dBm
-15
-20
-50
-25
OSNR
1.00E-03
-30
1.00E-05
-35
BER
Channel
analyzer
Measure
wavelength,
power and noise
Standard OSA
DWDM over
CWDM only
OSA without
OSNR
DWDM
Standard or
in-band OSA
1553
1554
1530
1531
Without
ROADMs
Standard OSA
With ROADMs
In-band OSA
10G and below
1.00E-11
Real Noise Level
IEC Noise Level
IEC Noise Level
Real Noise Level
1.00E-13
The Solution: In-Band OSNR
1.00E-15
The simplest case for an OSNR measurement is a single channel, as there is no interference coming from adjacent channels.
Measure
wavelength
and power only
-60
1552
1.00E-09
DWDM over
CWDM
-55
-40
1.00E-07
Noise
Spectral Analysis Product Selection Guide
18
19
20
21
22
23
OSNR (dB)
24
25
26
27
• In-band OSNR method is required to measure 40G signals or signals that went through (R)OADMs
• It consists in measuring the noise level inside the signal band, not out-of-band
DWDM
40G
In-band OSA
Download