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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
Page 10 of 10Last Updated - 9/10/2007 6:54:00 AM
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