GEPON Fiber Deployment Application Note Revision 1.0

Application Notes - UTSI-NJTC- GEPON Fiber Deployment Application NoteRevision 1.2September 10th, 2007

UT Starcom Inc.

New Jersey Technical Center,

33, Wood Avenue South,

Iselin, NJ, 08830

1 Introduction

UTStarcoms BBS Series of Optical Line Terminals (OLT) provides a direct optical interface to the Ethernet/IP network core. Together with UTStarcoms Optical Network Unit (ONU), it completes the end-to-end optical last mile with up to 1 Gbps of bandwidth to residential and business customers. Combining the economic benefits of Ethernet Passive Optical Network (GEPON) with built-in L2/L3 switching and routing functionalities, the BBS is an optimal transport platform for bandwidth-intensive triple play services.

2 Scope

This document provides considerations for fiber deployments in a GEPON Network. It outlines the different components of a GEPON network, the optical budget associated with them and the various testing considerations for the components being deployed.

It is intended to help with pre installation optical network planning and testing for GEPON networks. It can also be used for post installation physical network related maintenance. It is assumed that the user of this document has access to an Optical time domain reflecto meter (OTDR) to carry out the various measurements described here.

3 Audience

This documented is intended for UTStarcom GEPON customers, Sales engineering and field support engineers.

4 GEPON Network PlanningGEPON Network Planning consists of identifying the following:

1. Total Optical Link budget verification

2. Optical Link characterization

3. Splitter and Splice Characterization

4. End to End loss and Back-reflection Testing

5. OTL/ONU Power On

4.1 Total optical loss budget

First step is to calculate the total optical loss budget and verify that it is within the loss budget of the UTStarcom PON being deployed.

4.1.1 UTStarcom PON budget

RangeWorst CaseReceiver Saturation

OLT TX Power+2 to +7dBm3.5dBm

OLT RX Sensitivity-30dBm-30dBm-10 dBm

ONU TX Power-1 to +3 dBm-1 dBm

ONU RX Sensitivity-25.5 dBm-25.5 dBm-3 dBm

4.1.2 Typical Network components optical power budget

Network Components

Item DescriptionAttenuation UnitsNotes

1. Fiber Optic cable @ 1310 nm0.33db/kmG.652C fibers, such as SMF-28e

@ 1490 nm0.21db/kmG.652C fibers, such as SMF-28e

@ 1550 nm0.19db/kmG.652C fibers, such as SMF-28e

Insertion Loss

2. Fiber splice0.1dbSplice Losses should be below 0.1dB

3. SC connector0.4db

4. 1x2 splitter3.5dbTypical value, please confirm with vendor

5. 1x4 splitter7.4dbTypical value, please confirm with vendor

6. 1x8 splitter11dbTypical value, please confirm with vendor

7. 1x16 splitter14.3dbTypical value, please confirm with vendor

8. 1x3217.8dbTypical value, please confirm with vendor

9. Downstream Path Penalty1.5db

10. Upstream Path Penalty2db

Figure 1 gives a typical GEPON installation identifying the various components and the considerations for optical power budget

4.2 Optical Link Characterization

In this step Fiber loss and attenuation should be measured to ensure that it meets the specifications. This should be measured from OLT to Splitter and from Splitter to ONU before splicing. This should be done for each wavelength (1310nm, 1490nm and 1550nm) as the loss varies with the wavelength and is higher for higher wavelength.

This measurement enables us to identify any potential problem in the fiber deployment like macro-bends. Macro-bends will cause extra signal loss. It may be cause by several factors including tight tie wraps or sharp bend angles.

4.3 Splitter and splicing loss and back-reflection characterization

This should be done after splicing to ensure that splitter meets the specifications.

Back-reflection of coupler ports should be 35 dB or better, as per ITU-T G.983.1

4.4 End to End loss and Back-reflection Testing and Characterization

This is done between OLT end and the ONU end, bidirectional and for all three wavelengths (1310,1490 and 1550nm). One should ensure that the end to end loss is within the optical power budget of UTStarcom PON equipment as indicated above. Please note that The total loss should be less then the total optical power budget but more then the receiver saturation threshold as identifies in Table 1. This test will verify that:

Back-reflection measurement is OK: Telcordia sets an objective of -40 dB, but this assumes that all components are newly installed and that all of them respect the latest Telcordia recommendations. Generally speaking though, a value in the -30 to -35 dB range is sufficient. Values less than -30 dB should trigger corrective action.

Splice losses should be below 0.1 dB4.5 OTL/ONU Power On

The last step is to verify the OLT power received at the ONU end ot verify that it is greater then the receiver sensitivity and less then the saturation threshold.

Below is a sample calculation for the GEPON network identified above. It assumed the worst case Scenario for OLT and Transmit power. LINK LOSS Calculations

EDFA-ROOLT-ONUONU-OLT

forwardDownUp

155014901310nm

Input Power3NANAdbm

Transmit Power293.5-1dbm

Receiver Sensitivity-9-30-25.5dbm

Range382929db

Cable Loss

Feeder (C.O. - LCP)Km.WavelengthAttenuation ( db/km) G.652C fibers, such as SMF-28e

013100.330db

14900.2100db

15500.190

Dist. ( LCP-NAP-Drop)Km.WavelengthAttenuation ( db/km)

513100.331.65db

14900.211.05db

15500.190.95

Connector Pair Loss

#Insertion Loss (db)

C.O. (OLT-ODF)10.40.40.40.4db

LCP00.4000db

NAP00.4000db

EDFA / WDM Mux20.40.80.80.8db

Subs premise10.40.40.40.4db

Splice Loss

#Loss (db)

100.1111db

Overlay+Mux

WDM MUX110.60.60.60.6db

Power Split11x81111db

Splitter Loss

Location#TypeSplitter Loss (db)

LCP & NAP1x23.5000db

11x47.47.47.47.4db

1x811000db

11x1614.314.314.314.3db

1x3217.8000db

Allowance for Hydrogen Agingdb

Power Penalties111db

LINK LOSS: down / upstream37.8526.9527.55db

RX Signal Power: ONU / OLT-34.85-23.45-28.55db

System Margin: donw / up0.152.051.45db

4.6 UTStarcom best practicesHere is a list of best practices complied from our experience with current customer base.

1. It is recommended that customer go through the 5 step process described above as part of the installation process. These steps would help in network planning and identifying any potential problem up front thus reducing costly maintenance later on.

2. It is recommended that customers use splitters verified by us. In case third party equipment it is important to verify that they fall within the optical budget.

3. It is recommended that only UTStarcom supplied GEPON SFP be used. No other SFPs are recommended at this time.

4. Common Mistakes to avoid:

a. Failure to do proper power budget calculation. Budgeting with no or very less margins can cause random problems that are difficult and costly to pinpoint and fix post installation.

b. Sharp Fiber bends: Fiber bends increase losses. These losses increase with the wavelength. Fiber should not be bent beyond its bent radius. This is around 30mm for PON case. Thus care should be taken to prevent bends, especially at the access points (Connectors/splitters).c. Micro-bends: Micro bends are cause by too tight cable ties and add to optical power loss. Simple solution like using Velcro can alleviate this problem.

5. We recommend the following instruments for this installation planning and check. These equipments are also available for rent by major optical fiber companies like corning (http://www.corningcablesystems.com/web/corp/engserv.nsf/ehtml/eqrent )a. OTDRb. Variable F/b Digital attenuatorc. Fiber cleaning kit.d. Power Meter 4.7 Illustration of Splitter wiring

Following example shows undesirable fiber bend at the splitter and possible solution for the same.

This bend problem can be solved by doing the wiring and arrangement in the following manner. Consider a fiber comes in at the top page number 1

Then this fiber goes to splitter and exits with 12 wires.

Every page has 6 entry and 6 exits

Then suppose at page 2 three fibers are fused

Fusion is done inside the page where it is clamp using the connector jack on the top of page.

In this case, wiring should be as shown here to avoid potential sharp bend on the fibers.

4.8 Useful LinksCorning engineering services and technical literaturehttp://www.corningcablesystems.com/web/corp/engserv.nsf/ehtml/engser

Fiber Optic Cable

1:4 Splitter

LCP

OLT

Fiber Optic Cable

EMBED Unknown

ONU

1

8

1

2

3

4

1:16 Splitter

NAP

ODF

Legend:

SC connector

Fiber splice

Optical junction box

EDFA / WDM Mux

Subs premise

Total link loss budget

Link Characterization

Splitter & Splice Characterization

End to End Loss and Back-reflection

Figure 1

Potentially sharp bend due to entry and exit

Potentially sharp bend due to entry and exit

Splitter

Potential Sharp Bend due to entry and exist

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