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RM SCTE Webinar: All things Optical / PHY 1

Qualifying and Troubleshooting Cable Broadband PONs

RM SCTE Webinar – All Things Optical / PHY

13-Apr-2017

Michael Scholten, Sr. Product Marketing Mgr, AFL

Presentation Outline

Introduction – Market Drivers for MSO PON Deployment

MSO Passive Optical Network (PON) Architectures

RFoG PON Architecture

GPON / EPON Architecture

Fiber Test Basics

Connector Inspection & Cleaning

Insertion Loss Testing

OTDR Testing

Qualifying and Troubleshooting PONs

What’s Different when Testing a PON?

Out-of-service PON Installation Verification

What’s Unique about Testing a Live (In-service) PON?

Live PON Troubleshooting

Summary and Q & A


Bandwidth demand continues to skyrocket

4K and HDR video coming

Over-the-top (OTT) video

Online all-the-time society

Upstream bandwidth demand challenging

traditional CATV network architecture

(e.g. video upload)

RFoG, node splitting, DOCSIS 3.1 offer near-term solutions

More and more MSOs considering or deploying GPON/EPON architecture

Service Providers looking to converge business and residential networks

PON standards in place to grow bandwidth to 10Gb/s and 40Gb/s

XG-PON / 10GEPON – 10 Gb/s asymmetric

XGS-PON – 10 Gb/s symmetric

NG-PON2 – Up to 4 x 10Gb/s symmetric; Also supports WDM-PON

Market Drivers for MSO PON Deployment

3RM SCTE Webinar: All things Optical / PHY

MSO Network Architectures to Address BW Demand


RFoG PON Architecture

RF over Glass (RFoG) using Optical PON

Optical Distribution Network (ODN) includes:

1) WDM Mux / Demux at headend

2) Optical distribution fiber (feeder fiber)

3) Passive Splitter (or cascaded splitters)

4) Customer Drop Fibers

5Source: Aurora Networks

Headend

R-ONU

ODN

RM SCTE Webinar: All things Optical / PHY

1

23

4

EDFA: Erbium-doped Fiber Amplifier

WDM: Wavelength Division Multiplexer

RPR: Return Path Receiver

R-ONU: RFoG Optical Network Unit

CPE: Customer Premise Equipment

Source: “RFOG_Introduction_SOCAL_SCTE_Dec2014,” Aurora

RFoG Node Expansion using DWDM / CWDM

Use DWDM & CWDM to expand node size (# subscribers served)

DWDM in downstream direction (2-4 downstream s in 1530-1570 nm region)

CWDM in upstream (return path) direction

6

8 x 1:32 = 256 homes

8 x 1:32 = 256 homes

C-band DWDM 1

2C-band DWDM

1590 nm Return

1610 nm Return

1590 nm Return

1610 nm Return

1, 2

EDFA &Power Splitter

1:32Splitter

R-ONU


GPON / EPON Network Architecture

GPON / EPON deliver voice, internet & video to homes

7

ONT

OLT

FDH

Access

Terminal

PON Splitter

Located

at FDH…

…and/or

Access

Terminal

Headend


1490 nm

1550 nm 1310 nm

MDU FTTP PON Architecture

8

MDU Application:

Splitters typically installed in MDU

ground floor

Distributed splitter architecture

possible depending on MDU size

Access points in telecom closets

ONTs installed inside individual

apartments


Fiber Test Basics- Inspection & Cleaning

- Insertion Loss Testing

- OTDR Testing


Importance of Cleaning

#1 Problem: Dirty / Damaged Connectors!

“98% of installers and 80% of network owners reported that issues with

connector contamination were the greatest cause of network failure”


Source: NTT Advanced Technology

B: Cladding

Unacceptable single-mode end-face

Connector End-Face Inspection


Zone Scratches DefectsA: Core

(0 - 25 m)Max 4 3 m None allowed

B: Cladding(25 - 115 m)

No Limit No limit < 2 mMax 5 from 2 - 5 m

None > 5 m

C: Adhesive(115 - 135 m)

No Limit No Limit

D: Contact(135 - 250 m)

No Limit None > 10 m

A: Core

C: Adhesive

D: Contact

IEC 61300-3-35 Pass/Fail Criteria: SM, APCAcceptable single-mode end-face

FOCIS FlexConnector Inspection

Video scope

Note: Pass/fail criteria depends on fiber type, connector type & polish

Contamination

or Pitting

One-Click

Cleaners

Wet and Dry Cleaning


One-Click Cleaners (dry cleaning) Easy, fast & effective; Low cost per clean

Cleans jumper connector ends

Cleans through patch panels

Solution & Wipes (wet cleaning) Effective on stubborn contamination

Use solution which leaves no residue

Wipes or absorbent sticks to dry

Use sticks to clean through bulkheads

Clean both connectors of a mated pair every time you connect!

Ultra

One-Click

Mini

One-Click

Cleaners

Cleaning

Fluid

Tape

Cleaner

Cleaning

Sticks

Fiber Test Basics: Insertion Loss Testing

Why Measure Insertion Loss?

Verify end-to-end link attenuation does not exceed operational loss budget

Ensures acceptable transmission performance when compliant transmitter

is used with a compliant receiver

How to Measure Insertion Loss?

Inject known power level into one end of network

Measure output power level from other end of network

Loss (dB) = Input Power (dBm) – Output Power (dBm)


Power

(dBm)

Distance

? Loss

(dB)

PIN

POUT

Actual

Expected

Fiber Test Basics: Measuring Insertion Loss

Measure Loss using an Optical Light Source + Optical Power Meter

14

1) Set reference

Light Source

Tx

Optical PowerMeter

Rx

TX cord

PIN = -1.0 dBm

Measure PIN and store it

as the 0 dB reference level.

0 dB

RX cord

Connection (two connectors mated

through an adapter)

Tx

Optical PowerMeter

Rx

Light Source

2) Check test cords

TX cord

Allowed insertion loss

depends on connector type.

0.4 dB



15

Measure Loss using an Optical Light Source + Optical Power Meter

RX

Optical Power

Meter Light Source

TX

In this example:

Loss = -1.0 dBm - (-15.7 dBm) = 14.7 dB

POUT = -15.7 dBm

3) Measure link insertion loss

• Measure POUT and calculate IL = PIN – POUT

• Power Meter displays loss in dB relative to stored reference

14.7 dB

LinkPIN = -1.0 dBm



Use Source (OLS) & Power Meter (OPM) to measure loss

Test at operational wavelengths (e.g. 1310, 1490, 1550, 1610)

Or bracket performance by testing at short & long wavelengths

Loss testing done during Construction phase

16

Video Serving Office (VSO)

CustomerPremises

OLT

Feeder

Distribution

DropCWDM

FDF

Feeder Splitter Distribution Drop

20 km reach typical

1490 nm

1310 nm

1550 nm ONT

CATV Video Optional

Outside Plant

FDH

InjectKnownPower

MeasureLoss

MeasureLoss

OLS7

OPM4



An OLS/OPM can only measure end to end loss.

If loss is excessive, how can one determine cause?

17

Power

(dBm)

Distance

? Loss

(dB)

PIN

POUT

Actual

Expected


Fiber Test Basics: OTDR Testing

An OTDR is a one-dimensional optical “radar”:

Injects pulses of light, measures the amplitude and time of flight of

backscattered and reflected light guided back up the fiber

Converts time-of-flight into distance based on speed of light in glass

Plots returned signal level vs. distance

OTDR can measure the loss of fiber sections, as well as the loss and

reflectance of connections, splices, splitters, macrobends or breaks.

18

PIN

POUTFiber

Reflective

Connector

Non-reflective

SpliceReflective

Connector

Reflective

Connector

RM SCTE Webinar: All things Optical / PHY Distance

Relative

Power

(dB)

Unique Challenges when Testing a PON


What’s Unique When Testing a PON?

1) Normal trace up to the splitter

2) Backscatter & reflections from fibers overlap beyond splitter

Unacceptable loss in one drop fiber hidden by backscatter and reflections from

overlapping drop fibers

• Example: 3 dB loss in 1 leg = 0.06 dB in combined backscatter from 32 legs!

Even if fault detected, no way to determine which leg has the problem

3) Splitter appears as high-loss event -- Could be declared as fiber end

20

If OTDR test attempted from the OLT end:

12

3

Conclusion

Test from ONT end to reliably detect

faults in distribution and drop fibers.

1x3

2

Feeder Fiber

Drop Fiber

ONTEnd

OLTEnd


Mind Your Connectors!

FTTx PONs are usually built with angle-polished connectors

Ensures unused (open) splitter ports won’t generate strong reflections which could

disrupt PON operation, especially with 1550 nm video overlay

OTDRs may be built with either 90o SC-UPC or angled SC-APC connectors

SC-UPC more commonly used in non-PON applications

CAUTION: Do not mate UPC connectors to APC connectors!

Mated UPC APC results in excess reflection and loss

Poor OTDR results will be obtained when mismatched connectors mated

Use SC-UPC to SC-APC hybrid jumpers or launch cables as necessary to connect

OTDR with SC-UPC to SC-APC PON connectors

21

SC-UPC SC-APC

Air gap when mating SC-UPC

to SC-APC results in excess

reflection & loss Excess reflection at front panel

Ghost reflection (re-reflection)

Long recovery tail


OTDR Trace Display

Distance

Lo

ss

Out-of-Service PON OTDR Test

22

OLTFeederFiber

DistributionFiber

DropFiber

CWDM

FDF

1490 nm

1310 nm

1550 nm

ONT

FeederSplitterDistributionDrop

Splitter Loss

ConnectorLoss

End-to-End

Loss

CustomerPremises

Outside Plant

TraceNetwork

Reflectionsat Connectors

FDH

Splitter

Video Overlay(Optional)

Headend


OTDR Test Basics: LinkMap Display

Easy to understand LinkMap results

Icon-based representation of tested network

Color-coded event pass/fail reporting

Suggests corrective action for faulty events

Touchscreen event navigation

End-to-end Link Summary

Link Length, Loss, ORL, Attenuation (dB/km)

Event Details

Location, Type, Loss, Reflectance, Cum Loss

PON split ratio for detected splitters

Fiber Section Details

Section Length, Loss, Attenuation (dB/km)

Trace Display

Usually provides AB cursor measurements

23

Today’s OTDRs simplify network interpretation using LinkMap display


http://vector-magz.com/wp-content/uploads/2013/04/pointing-finger-vector.png






OTDR Test Basics: Range / Resolution Tradeoff

OTDR Pulse Width affects trace signal level and event resolution

Multi-pulse acquisition offers high resolution plus high dynamic range

24

Narrow Pulse Width:

Trace “disappears”

into noise floor.

Link

Wider Pulse Width:

Events can be seen

and trace is smooth.

Link

Widest Pulse Width:

Can’t resolve events

Link

Overlapping pulses

hide event


What’s Unique when Testing a Live PON?

One subscriber may lose service while others remain in-service

Network continues to transmit 1310/1610, 1490, and 1550 nm signals

Check downstream PON power levels at out-of-service ONT:

OK: Power at 1490 & 1550 nm wavelengths within expected levels

Dim or Dark: Little or no 1490 and/or 1550 nm power due to upstream fault

Cannot test a live PON using a standard OTDR!

OTDR test at 1310, 1490, or 1550 nm will disrupt service to other customers!

Downstream 1490 or 1550 nm signals interfere with normal OTDR’s receiver

Test in-service PON using a Live PON OTDR which includes:

An OTDR laser at an out-of-band wavelength (e.g. 1625 or 1650 nm)

A filtered detector to reject in-service wavelengths (e.g. 1490, 1550)

25

1260

Down VideoRFoG/PON Wavelengths1290 1330

Up

1480 1500 1550 1560

O - Band E - Band S - Band C-Band L - Band

1360 1460 1530 1565 1625 1675 nm

U - Band

Test

1625 1650

RFoG Up

1610


Live PON Test: Distributed 1:8 + 1:8 Splitters

1) Disconnect Drop cable from ONT

2) Connect Drop cable to OTDR port

3) Initiate OTDR test

4) Live network reported if downstream signal detected

Measure downstream signal level using integrated OPM

5) Initiate 1650 nm out-of-band OTDR troubleshooting

test if downstream signal not detected or too low

26

ONT

FDH

1st 1x8 splitter at FDH 2nd 1x8 splitter at Access Terminal


1

2

3

4

5

PON Testing Summary

MSOs responding to residential and business broadband demand by

deploying Passive Optical Network (PON) architectures

Higher broadband speeds demand lower optical Insertion Loss (IL) and

higher Optical Return Loss (ORL)

Connector inspection and cleaning becoming more critical

End-to-end IL & ORL tests provide go / no-go assessment of both PON

and point-to-point network performance

OTDR testing required to ID root cause of networks failing IL / ORL tests

PON testing requires unique OTDR testing strategy and capabilities

Test upstream from ONT to obtain understandable, actionable results

Ensure OTDR will not inject 1310, 1490, 1550 nm test signals into live PONs

Test in-service PONs using out-of-band wavelength with filtered detector


www.AFLglobal.com

Thank You!Questions?

www.AFLglobal.com


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