guide to detecting odn links-20090415-a

8/12/2019 Guide to Detecting ODN Links-20090415-A

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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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HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 3

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
http://www.t-yang.com.cn/ArticleShow.asp?ArticleID=118


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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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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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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


PON power meter PPM-350B (launched by EXFO)


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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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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 Link 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)


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)


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.


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


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 Link 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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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.


MA5680THG850e


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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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