(9) End-Face Inspection -...

Fiber ConnectorEnd-Face

InspectionProject

Dr. Tatiana Berdinskikh,Celestica International

Celestica-iNEMITechnology Forum

May 15, 2007

1

PresentationPresentation Outline Outline

• Introduction

• Highlights of Fiber Optic Performance Project

• The Fiber Connector End-Face Inspection Project

– Experimental Methodology

– The Influence of Contamination on Optical Performance

– Particle and Occluded Area Analysis using Images

– Gaussian Weighted % Occluded Area Analysis

– Inspection Criteria

– Evolution of Particle Center Position ( ESD effect)

• Further Research/ Phase 2 of the Project

• Conclusions

2

IntroductionIntroduction

• Fiber optic connector end-face cleaning recognized as anecessity

• Well known that contamination results in degradedperformance, but existing company specific standardslacked scientific basis

• iNEMI (International Electronics Manufacturing Initiative)research to develop a cleanliness specification for fiberoptic connectors

– Based on correlation with optical performance metrics

– Insertion Loss (IL) and Return Loss (RL) for this study

• Research used in the development of IPC-8497-1 “CleaningMethods and Contamination Assessment of OpticalAssembly” standard.

3

Projects/Background of the InitiativeProjects/Background of the Initiative

• Fiber Optic Signal Performance Project was organized

in 2002 to determine the effects of various anomalies

on the performance of a fiber optic signal

• A follow-on project, Fiber Connector End-Face

Inspection, was launched in 2004.

• Phase II of the End-Face Inspection Project was

launched in March 2007

– Project Chair: Tatiana Berdinskikh, Celestica, Inc.

– Project Co-Chair: Heather Tkalec, Alcatel-Lucent

4

Fiber Optic Signal Performance ProjectFiber Optic Signal Performance Project

5

35

40

45

50

55

60

65

D44

D54

D55

D56

D57

D601

D614

D621

D625

D30

D262

D320

D45

D603

D604

D613

D615

D616

D617

D626

D050

D728

D323

Connector Number

Launch cable & DUTs defects-free

Launch cable defects-free, CUTs S/N D44 to D320 scratches applied to the

caldding area, DUTs S/n D45 to D323 scratches applied to the fiber MFD

Graph shows impact of scratches on Return Loss- Most scratches in this study have minor impact on Return Loss


Published by Journal of SMTA, 2003

6

a) Particles on Ferrule and Cladding Area

00.20.40.60.8

11.2

JSC

1

JSC

3

JSC

5

LS

C4

TS

C152

TS

C153

Conn. ID

IL (

dB

)

B-IL(1550)

B-IL (1310)

A-IL(1550)

A- IL (1310)

b) Particles on Ferrule and Cladding

0

20

40

60

80

JSC

1

JSC

3

JSC

5

LS

C4

TS

C152

TS

C153

Conn. ID

RL

(dB

)

B- RL (1550)

B- RL (1310)

A RL (1550)

A RL (1310)

•IL-1550nm/1310nm(clean)=0.24/0.25dB;

•IL-1550nm/1310nm(contaminated)=0.92/1.07dB;

•RL-1550nm/1310nm (clean)=57.3/55.5dB;

•RL-1550/1310nm(contaminated)=56.5dB/55.6dB

Particle ison thecladdinglayer

Published by Journal of SMTA, 2003


The impact of Carbon Particles

7

Factors Affecting Optical PerformanceFactors Affecting Optical Performance

Delta IL vs Distance from Core

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 5 10 15 20 25 30 35 40 45 50

Distance From Core (micron)

Delt

a IL

Delta IL

Published by APEX 2004

Delta RL vs Distance From Core

-50

-40

-30

-20

-10

0

10

0 5 10 15 20 25 30 35 40 45 50

Distance from Core (micron)

Delt

a R

L

Delta RL

The zone of 25 μm diameter was identified as the critical zone in terms

of the contamination influence on optical signal performance

8


)cos21()cos2( 21

2

2

2

121

2

2

2

1 rrrrrrrrR ++++=

hnnn

nnr

nn

nnr 2

12

122

20

201

4,, =

+=

+=

no non1

dn2, High index layer

due to polishing

= dn

RdBRL14

cos12log10)(

Connection/contactlayer

Particles trapped in between two end-faces result in the air gap

Published by APEX 2005

9

Experimental Block DiagramExperimental Block Diagram

10

Cleaning and Measurement MethodsCleaning and Measurement Methods

• Total of > 550 experimental points including IL, RL and fiberscopicimages for the test cable and reference cable before and aftercontamination

• All DUTs and reference connectors cleaned

– Cleaning cassette (Cletop or Optipop)

• End-face inspected and images were saved

– Westover Scientific Probe 1 and FiberChek™ software

• Interferometer data (radius of curvature, apex offset and fiber undercut)were recorded for each DUT and reference

– Norland interferometer (NC-3000).

• IL and RL were measured

– Agilent 8164A

• Measured the number of particles, size, and locations on and measuredOccluded Area

– FiberQA™ software from PVI Systems

11

IL & RL Measurement DiagramIL & RL Measurement Diagram

Return Loss (dB)= 10 log (Pincident/ Preflected)=P0-P2-1.0

Note: During return loss test, the DUT jumper must be terminated by bending.

Insertion Loss (dB)= 10 log (Pincident/ Pout)=P0-P1

12

Clean Fiber

Area near thecore, d<25um

Cladding,25um<d<120um

Epoxy Ring Zone,120um<d<130um

ContactDiameter

130um<d<250um

Ferrule Diameter

250um<d<400um

Zone Definitions for Fiber Surface AnalysisZone Definitions for Fiber Surface Analysis

13

FC01-5th Mating Reference

CableInitial IL: 0.04dB

Initial RL: 54dBIL after contamination: 0.04dB

RL after contamination: 55dB

Passed: Within 3 Standard Deviations of Clean Fiber

3 x Standard Deviation of IL: 0.02dB

3 x Standard Deviation of RL: 3dB

FC Connectors - FC01 5th MatingFC Connectors - FC01 5th Mating

14

FC04- 2nd mating Reference Cable

Initial IL: 0.13dB

Initial RL: 54dB

IL after contamination: 0.26dB


Failed: Not Within 3 Standard Deviations of Clean Fiber


3 x Standard Deviation of RL: 1.4dB

FC Connectors - FC04 2nd MatingFC Connectors - FC04 2nd Mating

15

LC07-1st Mating Reference Cable T07

Initial IL: 0.11dB

Initial RL: 53dB





Passed: Within 3 Standard Deviations of Clean Fiber

LC Connectors - LC07 1st MatingLC Connectors - LC07 1st Mating

16

LC07-3rd mating Reference cable T07

Initial IL: 0.11dB

Initial RL: 53dB






LC Connectors - LC07 3rd MatingLC Connectors - LC07 3rd Mating

17

Initial IL: 0.11dB

Initial RL: 53dB



LC07- 5th mating Reference Cable T07


3 x Standard Deviation of RL: 1 dB


LC Connectors - LC07 5th MatingLC Connectors - LC07 5th Mating

18

Particle Detection OverlaysParticle Detection Overlays

Raw Cropped Image Detected Particle Overlay

• The raw image (left) was processed to detect and quantify the

particles on the surface, shown in overlay (right).

• Scratch processing was disabled for purposes of this analysis.

Over 270 images were processed using FiberQA

19

Labeled Detected Particles with

5 μm annular rings. (Black area is

ferrule and grey is fiber.)

Raw image for LC07-WD-5M

taken with Westover Microscope

Occluded Area OverlayOccluded Area Overlay

20

Incremental occluded area vs radius

Occluded Area GraphsOccluded Area Graphs

Cumulative occluded area vs radius

Data for connector LC07

21

Normalized Occluded AreaNormalized Occluded Area

• Occluded area within each ringis normalized by the area of thatring

• Plotted as percentage ofincremental area

• This was first attempt atnormalizing data that lead toweighting by intensitydistribution vs radius

• Sample LC 07:

–Before mating core clean

–1st mating 1.4% occluded

–2nd mating 11.6% occluded

–4th mating 32.9% occluded

–delta IL=0.46dB and deltaRL=24dB) over the mating cycles

22

Gaussian Weighting FactorGaussian Weighting Factor

• Dr. Sun-Yuan Huang of Intel, suggested a valuable

improvement that takes into account the Gaussian distribution of

the fundamental mode of the fiber.

• The intensity distribution of fundamental fiber mode is expressedas I0 exp(-2r2/ f

2), where I0 is the peak intensity, r is the radial

position and f is the mode-field radius of fiber mode.

• To account the effect of intensity profile on the insertion loss weintroduce the Gaussian weighting factor = exp(-2r2/ f

2).

• The Gaussian weighted % occluded area is defined as

where ai is the size of particle at ith ring, i is the

Gaussian weighting factor for the ith ring, and Ai is

the area of the ith ring. For i = 0 it denotes the

initial circle.

100(%)

0

0 •=N

ii

N

ii

A

a

f

23

Fiber Intensity DistributionFiber Intensity Distribution

13.5%

2 f

I(r) = Io exp(-2r2/ f2)

Mode field diameter of SMF-28 is 9.2 mm at 1310 nm and 10.4 mm at 1550 nm.

24

Delta IL Delta IL vsvs Gaussian Weighted % Occluded Area Gaussian Weighted % Occluded Area

The Delta IL for the worst-case defects and scratches based

on inspection criteria is less than 0.03 dB

25

Inspection Criteria for SMF End-faceInspection Criteria for SMF End-face

anynone > 10 microns130 to 250

microns2 — Contact Zone

anyany120 to 130

micronsAdhesive Zone

none > 3 microns

any < 2 microns

5 from 2 - 5 microns

none > 5 microns

25 to 120

microns1b — Cladding Zone

nonenone0 to 25

microns 1a — Core Zone

Scratches (width)Defects (diameter)DiameterZone/Description

Allowable Defects and Scratches

26

Receptacles ModulesReceptacles Modules

Distance from core (um)

Published by Photonics North 2005 conference

27

ESD Effects From CleaningESD Effects From Cleaning

• The increased accumulation of particles near the core

during a series of mating/de-mating operations was

investigated. One cause for this accumulation was ESD

(electrostatic discharge) effects from cleaning. Methods to

prevent this phenomenon were studied.

The paper “Accumulation of Particles Near the Core during

Repetitive Fiber Connector Matings and De-matings” was

presented at NFOEC 2007, Anaheim, March 2007

28

ESD EffectESD Effect

Electrostatic charges generated from cleaning process with cleaning cassette,Type 1 for standard and non-standard connector samples.

Humidity is 28%, room temperature is 24C.

Sample preparation

29

Particle Center EquationParticle Center Equation

• The dust particle distribution on the connector end faces can bedescribed by a single parameter Rc, which is called the center ofparticles.

Where ri and ai are the ith particle radial position and area, respectively. N is the total number ofparticles included in the Rc calculation.When formula is applied to the occluded area, ai is then the total particle area within the ith

annular region.

=N

i

N

ii

c

a

ar

R

0

0

(1)

30

Particle Center vs. MatingParticle Center vs. Mating

Evolution of Particle Center Position for Experiment 1, 2, 11, 16, and 18

Exp 1 and 2 show a dramatic decrease in Rc during repeated matings.

Radius decreases with increasing matings

0

50

100

150

200

250

300

0 1 2 3 4 5

Number of Mating Cycles

Rc

(u

m)

Exp1

Exp2

Exp11

Exp16

Exp18

31

y = 166.18x

R2 = 0.9073

0

25

50

75

100

125

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Charge (nC)

Mo

vin

g S

pe

ed

(um

/ma

te)

Correlation of Rc Speed to ChargeCorrelation of Rc Speed to Charge

• Based on the fact that the electrostatic force F is proportional to the

amount of charge Q, we describe their relationship by F = b*Q, where b is

the constant depending on the geometrical configuration and the electrical

property of dust particles.

F=m*dV/dt (1)

Vc=c*Q (2)

c=b* t/m, c=166 m/mate/nC (3)

Particle center moving speed versus charge

32

Leading the IndustryLeading the Industry

Collaboration with TIA, IEC and IPC• The Project is collaborating with International Electrotechnical

Committee (IEC), Telecommunications Industry Association (TIA)and IPC to develop a cleanliness standard.

iNEMI presentations:• OMI conference, Ottawa, Apr-29-May 1, 2003

• IEC meeting, Montreal, Quebec, Canada, Oct 6-13, 2003 (presented by T.Berdinskikh, Celestica)

• APEX2004, Anaheim, California, Feb 19-Feb 26, 2004

• IEC meeting, Locarno, Switzerland, Apr, 04 (presented by T. Mitcheltree,Cisco)

• IEC meeting, Warsaw, Poland, Sep, 04 (presented by R. Manning, Tyco)• APEX2005, Anaheim, California, Feb, 05

• IEC meeting, Charlotte, NC, Apr, 05 (presented by R. Manning, Tyco)• A draft of IPC-8497-01 “ Cleaning Methods and Contamination Assessment for Optical

Assembly” has been submitted to IPC (June, 04)

• OFC2006, Anaheim, California, Feb, 06

• IEC meeting, Quebec City, Canada, Oct, 06 ( presented by T. Berdinskikh andHeather Tkalec)

• OFC/NFOEC 2007, Anaheim, Califirnia, March, 07

33

Fiber Connector End-Face Project, Phase IIFiber Connector End-Face Project, Phase II

• The Fiber Connector End-Face Inspection Project waslaunched in March 2007

– Face-to-face meeting was held at NFOEC conference, March26, 2007 (Anaheim, CA)

– The project team already developed the Statement of Work

• Further Research:

– Development a cleanliness specification for multimode (MM)fiber, MTP connectors and receptacle type devices

– Measure the particles thickness in order to correlate the RLchanges with the size of the air gap

– Correlate the changes of IL & RL of contaminated connectorswith the signal integrity (Bit Error Rate)

34

Sample MT Endface DataSample MT Endface Data

Clean DUT Contaminated DUT (Arizona Road Dust)

Zone A – 25 micron

Core – 10 micron

611-23 Ref – 604B DUT; F6 D1 IL (dB) RL (dB)

average (10X) 0.098 69.4

std deviation 0.013 0.7

average + 3X std dev 0.137 67.4

0.430 33.4

clean

Contaminated

US Conec Research

35

ConclusionsConclusions

• The iNEMI team conducted experiments to compare the effects ofspecific contamination on the optical performance of fiber opticconnectors

• The zone of 25 μm diameter was identified as critical zone in terms of thecontamination influence on optical signal performance for all types ofinvestigated connectors

• Developed empirical model between IL and the Gaussian Weighted %Occluded Area

• In 60% of all examined LC and MU connectors, a series of five repeatedmatings/demating operations resulted in an increase of IL of 0.5 to 1.1dB due to particle movement from the ferrule and cladding areastowards the core

• Electrostatic charge force was one of the mechanisms responsible forthe particle accumulation, re-distribution and their movement in the corearea during repetitive connector mating and de-mating cycles

36

ConclusionsConclusions

• The iNEMI project team successfully completed 2 projects: theFiber Optic Signal Performance ( 2002-2004) and the FiberConnector End- Face Inspection, Phase I ( 2004-2007). A newproject (Phase II) launched in March, 07

• The iNEMI research was used as a baseline for the developmentof IPC-84-97-1 “ Cleaning Methods and contaminationAssessment for Optical Assembly’

• A project team delivered 10 papers published by industrialmagazines and International optic conferences

• Further research is required on a development of the cleanlinessspecification for MM connectors, MT- ferrule connectors andreceptacle modules

37

Project participants, 2004-2007Project participants, 2004-2007

• Tatiana Berdinskikh, Celestica

• Jose Garcia, JDS Uniphase

• Steve Lytle, Westover Scientific

• Randy Manning, Tyco Electronics

• David Fisher, Tyco Electronics

• Brian J. Roche, Cisco Systems

• Tom Mitcheltree, Cisco Systems

• Mike Hughes, USConec

• Thomas Ronan, Aerotech

• Heather Tkalec, Alcatel

• Frank (Yi) Zhang, Avanex

• Denis Gignac, Nortel Networks

• Doug Wilson, PVI Systems

• Dr. Chip Kilmer, Sagitta

• Dr. Sun-Yuan Huang, Intel

• Carla Gleason, ExceLight CommunicationsInc/ Sumitomo Electric

• Harvey Stone, Microcare

• John Culbert, Megladon Mfg

• Yutaka Sadohara, Sumitomo Electric

38

Past participants, 2002-2004Past participants, 2002-2004

• Tatiana Berdinskikh, N. Albeanu Celestica

• Jennifer Nguyen, Solectron

• Yves Pradieu, Solectron-Iphotonics

• Randy Manning, Tyco Electronics

• Dave Silmser/Heather Tkalec, Alcatel

• Tom Mitcheltree, Cisco Systems

• Thomas Ronan, Ingrid Levy, Aerotech

• Frank (Yi) Zhang, Avanex

• Denis Gignac, Nortel Networks

• Carla Gleason, ExceLight CommunicationsInc/ Sumitomo Electric

• Les Aseere, Sanmina

• Matt Brown, USCONEC

• Steve Lytle, Westover Scientific

• Susan Grant, Corning

• Arnaud Nicolas, FCI

• Mark Vogel, Trace Labs

• David Horat, Diamond

www.inemi.org

Email contact:

Tatiana Berdinskikh

[email protected]

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