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HUAWEI TECHNOLOGIES CO., LTD.
www.huawei.com
Huawei Confidential
Security Level: Internal2014/5/30
Guide to Detecting ODN Links
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Terminal
Optical distribution network (ODN): provides the optical channel betweenthe OLT and the ONT. The drop cable section is the most arduous in anODN project.
Fiber management point (FMP): test access points when ODN faults arebeing diagnosed.
ODN
FMPFMS
Central office(CO)
FTTH ODN
Feeder opticalcable
Distributionoptical cable
Drop cable
O
LT Optical distribution point Subscriber accesspoint
ONT
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ODN (Continued)Split ratio
Currently, in a GPON system, the largest split ratio is 1:64, but in an EPON system, the
largest split ratio is 1:32. In addition, in an ODN project, only 1-level or 2-level splittingis adopted, and 3-level or multi-level splitting is not recommended.
Case study: Xiaojie is an ODN planning engineer in W site, China. In this site, the 1-level splitting for the GPON port is 1:8, and the 2-level splitting is 1:8, 1:8, and 1:16respectively on three links, as shown in the following figure.
18
116
18
18
Is this ODNnetwork acceptable?
The split ratio is not determinedby the number of connected
devices because opticalattenuation is generated as soon
as the optical splitter isconnected.
For the top link in the left figure,the split ratio is 1:8 x 1:16 =
1:128, which goes beyond thelargest split ratio of 1:64.
Therefore, this ODN network isunacceptable.
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ODN Products
ODF Optical splitter
(rack-mounted )
Optical Splitter(small-sized)
Adapter (FC-FC)
Adapter (SC-SC) Pigtail fiber Patch cord Optical cable
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ODN Products (Continued)
We often see that
the pigtail fiber andthe patch cord are
marked withSC/PC, SC/APC,and FC/PC. What
are their meanings?
Typical connectors
SC
Connector accuracy
FC
LC
PC
APC
UPC
Big square
Round
Small square
Blue (ORL > 45dB)
Green (ORL > 55 dB)
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Contents
Summary
E2E
Chapter 1
Chapter 2
Chapter 3
Chapter 4
ODN and ODN Products
Test Tools and Parameters for ODN Links
ODN Link Test
ODN Service Provisioning Test
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2. Insertion loss
(ODN component)
3. Optical return loss(ORL)
1. Attenuation(optical cable)
PONengineering
Key ODN Parameters
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Attenuation
Attenuation is the loss of optical power as the light travels
down an optical cable.
Optical Fiber Type Average Loss (dB)
G.652D1310 nm (1 km) 0.35
1550 nm (1 km) 0.21
G.657A 1310 nm (1 km) 0.38
1550 nm (1 km) 0.25
)log(10InPower
OutPowerDB
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Insertion Loss
Insertion loss is the ratio of the input optical power of an insertedcomponent to the output optical power of the inserted component, and is
expressed in decibels (dB).
Insertion loss is measured in the same way as attenuation.
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Typical Loss Values of ODN Components
Item Type Average Loss (dB)
Connectionpoint
Quick connector 0.5
Mechanical splicing 0.2
Fuse splicing 0.1
Adapter 0.3
Optical splitter
1:64 (PLC) 20.5
1:32 (PLC) 17
1:16 (PLC) 13.8
1:8 (PLC) 10.6
1:4 (PLC) 7.5
1:2 (FBT) 3.8
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Optical Return Loss (ORL)
ORL (or reflection loss) is the ratio of the reflected light to the incident light, and isexpressed in decibels (dB).
The higher ORL, the better the ODN link is. A high ORL means that the impact of
the reflected light on the light source and the system is small.
The minimum ORL of the line under test is recommended to be 45 dB. In general, different types of connectors have different ORL values. To be specific,
regarding the ORL, PC > 45 dB and APC > 55 dB. In the case of the CATV service,
all ODN nodes must use the connectors of the APC type.
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Tools for Detecting ODN Links
Common test tools
Professional test tools for a PON network
1. Optical power meter and light source
2. OTDR
3. Optical fiber identifier
4. Optical fiber connector cleaner
1. PON power meter
2. OTDR (able to penetrate the optical splitter)
3. Fault locator
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Tools for Detecting ODN Links (Continued)
Calibration wavelength: 850/1300/1310/1550 nm
Detector: Ge, InGaAs
Measurement range: +6 dBm to -60 dBm
Accuracy: 0.25 dBm
Common optical power meter, with the total
optical power displayed
Optical power meter Fujikura OPM1
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Tools for Detecting ODN Links (Continued)
OTDR
(unable to penetrate the optical splitter)Fujikura M200
Display of the loss distribution curve of the
optical fiber
Light (0.9 kg), small, and easy to carry
Multi-mode or single-mode signal
Dynamic range: 26 dB (single-mode), 22 dB
(multi-mode)
Red light to locate faults
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Tools for Detecting ODN Links (Continued)
Optical fiber cleaner
Automatically identifies upstream and
downstream signals and their directions,
without service interruption (test these
two types of signals concurrently)
Live mapping of optical fibers, without
service interruption
Test of signal presence or absence, signal
direction, and power
Hands-free operation via Hold button Three interchangeable adapter heads,
meeting requirements of all adapter
heads in the industry
LFD300(launched by EXFO )
Optical connectorcleaner (launched by
NTT)
Adapter cleaner(launched by NTT)
Non-dust cloth+anhydrous alcohol, a verycost-effective method, also can be used toclean the optical connectors and adapters.
Optical fiber identifier
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Simultaneous measurement of the
optical power of all PON signals,
namely, voice, data, and video signals,
with pass/fail indicator
A pass-through device between the OLT
and the ONT, which does not affect the
service during the test
Test of the burst signals of the ONT,
with pass/fail indicator
Tools for Detecting ODN Links (Continued)
PON power meter PPM-350B (launched by EXFO)
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Tools for Detecting ODN Links (Continued)
OTDR (able to penetrate the optical splitter) MTS6000
(launched by JDSU)
Maximum dynamic range: 50 dBminimum
event dead zone: 0.8 m Ability to test the entire PON network 1310/1490/1550/1625 nm wavelengths Ability to integrate modules or connect to the
optical power meter, visual fault locator, lightsource, high-speed Ethernet port, and USB
Touch screen, and ease of use
Dimensions: 285 mm x 195 mm x 93 mm
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Tools for Detecting ODN Links (Continued)
Fault locatorFLS-240
(launched by EXFO) Ability to generate continuous or pulse
red light and to inject this red light into
the optical fiber (The red light
emanates from a break or micro bend
of the optical fiber.)
Ability to identify breaks or bends of
the optical fiber, faulty connector,
faulty splice, and so on
Detection distance: 5 km
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Contents
Summary
E2E
Chapter 1
Chapter 2
Chapter 3
Chapter 4
ODN and ODN Products
Test Tools and Parameters for ODN Links
ODN Link Test
ODN Service Provisioning Test
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ODN Test
OLT
CO
1: N splitter
Test procedure (recommended)
Step 1:
Step 2:
Step 3:
Step 4:
Step 5:
Link test at the feeder optical
cable section
Total link loss budget
Link test at the distribution opticalcable and drop cable sections
Link test of the optical splitter
Service provisioning
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Step 1: Total Link Loss Budget
Based on the type of the deployed PON network, check each component in an
ODN before a test. The total link loss budget in an ODN covers the following
aspects:
(1) Insertion loss of the optical splitter
(2) Loss from fuse splicing and mechanical splicing
(3) Insertion loss of the connector and adapter
(4) Loss from optical transmission
(5) Extra link loss (generally about 3 dB)If the CATV service is also provisioned, include the following aspects in the
total link loss budget:
(6) WDM loss (loss of each WDM coupler: 0.7 dB to 1.0 dB)
(7) When the 1550 nm wavelength is used for CATV transmission, the link
power budget also needs to cover the following aspects: attenuation of 1550 nm
wavelength (about 0.2 dB/km) and minimum optical power of the CATV
receiver (-8 dBm).
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Attenuation Budget for the ODN Link
Item Unit Single-Mode Optical Fiber
GPON Class B+ EPON PX10 EPON PX20
Optical power
Optical link loss (max.) dB 28 21 26
Optical link loss (min.) dB 13 5 10
GPON optical transceiver: Class B+, 1:64/20 km.EPON optical transceiver: PX10/PX20, 1:32/10 km or 1:16/20 km.
The ODN link is recommended to have a certain attenuation redundancy when anODN is planned.
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Example of Calculating the Total Link Loss Budget
Item Type Average loss (dB)
Connectionpoint
Quick connector < 0.5
Mechanicalsplicing
0.2
Fuse splicing 0.1
Adapter 0.3
Opticalsplitter
1:64PLC 20.5
1:32PLC 17
1:16PLC 13.8
1:8PLC 10.6
1:4PLC 7.5
1:2FBT 3.8
Optical fiber(G.652D)
1310 nm (1 km) 0.35
1550 nm (1 km) 0.21
Optical fiber(G.657A)
1310nm (1 km) 0.38
1550 nm (1 km) 0.25
Attenuation Calculation(ODN Equipment Except Optical Cable)
OCCB FDT Indoor SplitterFAT TB
OLTLegend: ODF
OLT1:2 Splitter
& ODF
ODF &
Splicing OCCBFDT &
1:32 Splitter FAT TB ATB ONT
OLT1:2 Splitter
& ODF
ODF &Splicing OCCB FDT FAT TB ATB ONT
1:32 IndoorSplitter
0.3 0.3+3.8+0.3 0.3+0.1 0.1 0.1+0.3+17+
0.3+0.1
0.1 0.1 0.5+0.3 0.3
Total Loss = 24.3 db
0.3 0.3+3.8+0.3 0.3+0.1 0.1 0.1 0.1 0.1+0.3+17
+0.3+0.1
Total Loss = 24.4 db
0.1 0.5+0.3 0.3
Connector Fuse splicing Mechanical splicing
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Total Link Loss Budget
Dynamic range of the OLT optical receiver
MA5680T
HG850e
1:2 opticalsplitter
1:16 opticalsplitter
HG850e
The strength of the optical signal receivedon this ONT is budgeted to be -7 dB.
The strength of the opticalsignal received on this ONTis budgeted to be -23 dB.
Can services be provisionedconcurrently on these twoONTs if their receive opticalpowers are within the budget?
1. As specified in the protocol, the dynamic range of the OLT optical
receiver is within 15 dB. That is, the difference between the maximumoptical attenuation and the minimum optical attenuation must be within 15dB. If a range exceeds the dynamic range of the OLT optical receiver, thebit error rate (BER) increases, or even certain ONUs go offline.
2. The preceding problems will not occur if you plan an ODN in strictcompliance with the protocol.
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(Optional) Step 2: Test of the Transmit OpticalPower of a PON Port (Continued)
Required tool: optical power meter
Precautions:
1. Prepare a suitable patch cord because the connector type of the PON port is SC/PC,
but the connector type of the optical power meter is usually FC/PC (round).
2. Do use the single-mode patch cord rather than the multi-mode patch cord in a PONnetwork. (The single-mode patch cord is yellow and the multi-mode patch cord is
orange.)
3. After the test, use the anhydrous alcohol or the professional cleaner to clean the
connectors of the patch cord.
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Step 3: Link Test at the Feeder Optical Cable Section (1)
Purpose: to test the link status from the PON port on the OLT to the IN port of theoptical splitter (using the OTDR)
1:32 opticalsplitter
MA5680T HG850e
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Step 3: Link Test at the Feeder Optical Cable Section (2)
Required tool:optical power meter
Precautions:
1. If the OTDR is not available to the field engineers, they can use the optical powermeter to test each node with the adapter. In this manner, only the optical attenuationcan be obtained and the information about the ORL and distance cannot be obtained.
2. When using the optical power meter instead of the OTDR, ensure that a reliable light
source is available on the peer end.
3. The node-by-node test when the optical power meter is used is also applicable to thedistribution optical cable and drop cable sections.
3. Try to perform bidirectional tests.
4. (Mandatory) After the test, use the anhydrous alcohol or the professional cleaner to
clean the connectors of the patch cord.
It is recommended to use the OTDR for thetest and acceptance.
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Step 4: Link Test at the Distribution Optical Cable andDrop Cable Sections
Purpose: to test the link status from the OUT port of the optical splitter to the ONT
(using the OTDR)
1:32 opticalsplitter
MA5680THG850e
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Step 4: Link Test at the Distribution Optical Cable andDrop Cable Sections (Continued)
Required tool: OTDR
Precautions:
1. Most of OTDRs available to the field engineers cannot penetrate the optical splitter;therefore, when you perform a test in the upstream direction from the ONT, the distancedisplayed on the OTDR is the distance between the ONT and the optical splitter.
2. When using the OTDR to perform a test, ensure that the optical fiber is in the blackstate (that is, no light source exists in the optical fiber link). In addition, pay attention toselecting the upstream and downstream wavelengths (1310 nm, 1490 nm, and 1550 nm)
3. Try to perform bidirectional tests.
4. (Mandatory) After the test, use the anhydrous alcohol or the professional cleaner toclean the connectors of the patch cord.
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Step 5: Test of the OUT Ports on the OpticalSplitter
Purpose: to test each OUT port on the optical splitter to ensure that the insertion loss of
the optical splitter complies with the corresponding standards.
1:32 opticalsplitter
MA5680THG850e
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Step 5: Test of the OUT Ports on the Optical Splitter(Continued)
Required tool: optical power meter
Precautions:
1. Prepare suitable patch cords because the connector of the optical splitter is rich in variety.
2. Ensure a reliable light source when using the optical power meter for a test.
3. After a test, clean the connectors and adapters of the patch cords because the connectors ofthe optical splitter need to be often removed and installed in a test.
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Step 6: Identifying of Optical Fibers (Continued)
Purpose: to identify effective optical fibers and rogue ONTs.Required tool: optical fiber identifier or optical power meter
1:32 opticalsplitter
MA5680THG850e
Now I know thepigtail fiber fromthe optical splitter,but how todetermine that thepigtail fiber is notconnected to arogue ONT orother light source?
Devices inthe alwaysactive state
1. In general, the ONT in a PON network cannottransmit optical signals before it is connected to the
network. Therefore, before the ONT connects thenetwork, if the pigtail fiber from the ONT has opticalsignal, it indicates that the rogue ONT or other lightsource exists in the PON network.
2. The optical power meter can be used for a test.
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Contents
Summary
E2E
Chapter 1
Chapter 2
Chapter 3
Chapter 4
ODN and ODN Products
Test Tools and Parameters for ODN Links
ODN Link Test
ODN Service Provisioning Test
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Service Provisioning Test (2)
2. Check whether the actual ODN link loss is within the loss budget.
It can be seen that the differencebetween the budgeted value andthe actual value is 9 dBm, but the
actual value is still within thenormal range of the optical
transceiver. In this case, should Icheck the link?
Case study: In site A, the transmit optical power of the PON port on the OLT is 3dBm and the attenuation budget from the PON port to a certain ONT is 15 dB.Therefore, the receive optical power of the ONT is budgeted to be -12 dBm. Theactual optical power of the ONT, however, is -21 dBm.
Yes, you should check the link. That is
because the optical attenuation isabnormal, which in turn causes other
parameters such as ORL to beabnormal. Eventually, the network
may be unavailable.
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Service Provisioning Test (3)
3. Use the optical power meter to test the ONT to ensure that the
ONT optical transceiver is not in the always active state.
In general, the ONT optical transceiver in a PON network cannot transmit
optical signals before it connects the network. Therefore, if it is detected that
the ONT optical transceiver is in the always active state, replace the ONT or
disable the optical transceiver that is in the always active state.
1:32 opticalsplitter
MA5680THG850e
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Service Provisioning Test (4)
4. Check whether the transmission distance complies with the
PON standards.
GPON optical transceiver: Class B+, 20 km, 1:64
EPON optical transceiver: PX10/PX20, 10 km/1:32 or 20 km/1:16
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