cleanliness specification for expanded beam connectors...

Development of Cleanliness

Specification for Expanded Beam

Connectors Project

End of Project Brief

July 20 , 2016

2

Project Members• Tatiana Berdinskikh

• Tom Coughlin

• Michael Kadar-Kallen, Mike Gurreri

• Christine Chen

• Ken Toyama, Mark Marino

• Doug Wilson

• Tom Mitcheltree

• Kevin Chaloupka, George Megason

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Development Cleanliness SpecificationStandards Development

2002 2010 2015

Fiber Optic End-Face Inspection, Phase I , II

Sumitomo transceiver study

Particles Thickness Project

Expanded beam MM connectors

Impact of connector RL on 40G transmissionLens-based

transceiver initial study

Optical Signal Performance

IPC-8497-1

IEC 61300-3-35

IEC/TR 62572-4

IEC 62627-05-TRIEC Scratch Recognition Task Force

Completed projects

Projects in progress

New Projects

MM Expanded Beam - Visual Inspection Criteria

4

Cleanliness Specification for Expanded Beam Connectors 10+ years of iNEMI research on the impact of contamination on fiber optic connector performance provides a quantitative approach to developing the first-ever industry cleanliness specification for expanded beam connectors.

Photos above (clockwise from top left): Molex expanded beam connector; US Conec PRIZM LT Connector; US Conec MXC connector with PRIZM MT ferrules.

• WhatdoesacleanlinessspecificationmeanforMegaDataCenters?

• How“clean”mustanexpandedbeamconnectorbetomeetopticalperformancerequirements?

• Whatistheimpactofcontamination/scratchesontheopticalperformanceofexpandedbeamconnectors?

• HowcanDataCentercosts(cleaning)bereducedbydevelopmentofacleanlinessspecificationthatisbasedonaquantitativeapproachandisacceptedbytheindustry?

Ref: Project Collateral

5

Development of Cleanliness Specification for Expanded Beam Connectors Project

Project Background• To date, no formal inspection contamination criteria have

been adopted by the industry for any expanded beam connector. This project is being organized to develop recommendations for visual inspection criteria for expanded beam connectors based on experimental and modeling data.

Project Objectives:• Investigate the impact of contamination on optical

performance (transmitted power) of expanded beam optical connectors- Completed

• Develop a cleanliness specification for expanded beam connectors from the results of the investigation of impact contamination and defects- Further Development is required

6

Project Plan & Milestones

Task Complete Q1 Q2 Q3 Q41. Empirical MMF IL data on PRIZM®-LT

2.Empirical MMF IL data on MT jumpers

3.Data review, contamination modeling

4. White paper development

5. Present the results to IEC, SC86B, WG4 & WG6

6. End of project webinar

Current Status: -2 different sets of experimental data, 2 different modeling approaches-Good correlation between experimental and modeling data-New metric (calculated insertion loss) was developed -Paper published by Optical Interconnects conference (San Diego, CA, May 9-11, 2016)-Paper accepted: IWCS 2016 Int’l Cable & Connectivity Symposium (Providence, RI, Oct 2-5, 2016)-Project Webinar- July, 2016

7

Overview• Experimental Measurement• Image Processing• Multimode Dust Loss Calculations• Raytrace based modeling• Comparison of Measured and Calculated Loss• Conclusions• Next Steps

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Goal• To quantify the impact dust has on IL on MT12F MM Lens

plate (Molex VersaBeam)

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Materials• Sample size: Eight 12F lens plates (in MTP connector)

terminated using standard MM 50/125um graded index ribbon fiber.

• Arizona road dust was applied only to the recessed lenses.

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Cross Section of Mated Lens Plate• The 12F lens plate is a collimated lens with an index of

refraction of 1.512 and distance from fiber endface to lens apex 0.53mm.

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Experimental Measurement Flowchart

Record initial photos of the DUT and

launch cable

MateRecord ILDe-Mate

Add Dust

Record photos of DUT. Clean launch cable if

dust is present

Clean DUT and launch

cable

Record photos of DUT and launch cable

M0

MC

MnRepeat

n = 1 to 5



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Examples of Fine Dust – S/N 005 – F7

M0

M5

MC

12

13

Examples of Fine Dust – S/N 005 – F7

M5M0 MC

0.42dB 0.42dB0.76dB

Delta IL from M0: +0.34dB

13

14

Examples of Coarse Dust – S/N 08 – F1

M0

M5

MC

14

15

Image Acquisition and Processing

• FastMT used to collect images at various points in the data collection process, along with IL data

• Images were collected using backlighting to improve defect detection

• Lens specific processing developed• Weighted Occluded area was

computed for each image, using new method that computes weighting at each pixel location

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FastMT Lens Processing

• Converted image to Contrast Ratio (CR) space for improved threshold and detection

• CR is calculated by dividing the raw image by an estimate of the background computed adaptively or using analytic function.

• CR is independent of system gain terms:–Exposure, LED intensity, and camera gain

• CR improved defect detection accuracy

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CR Leveling of Uncontaminated Lens

LeveledRaw

Whitebandingatedgeoflenscausedbymismatchinquadraticmodeltoactualshape.Finaldatausedalargerdiametertoreducethiseffect.

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CR Leveling of Highly Contaminated Lens

LeveledRaw

PartID:ProcessSet6,Sample10,M1,Fiber03

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Occluded Area Processing

• Computed Quadratic Weighted Percent OA using:– Weight(r) =1-(r/Max Radius)^2– QWpOA= Sum of (Weight(r) * Occluded Area (r)) over all r

• Max Radius set to 70 um, max value of r=65 um (to avoid edge of lens artifacts)

• Weighting function computed at each pixel location (previous version used set of annular rings for an approximation of the weighted OA)

• Later data sets (not shown in this presentation) used:• Max Radius:75 um• Max value of r: 70 um

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Example OA: S-008, C, Fiber-01

Leveled Detected Defects OARings*

*Final datawascomputed usingapixel basedweighting functionratherthantheearlierOAringsshownhere

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Image Acquisition and Processing Summary

• Images were processed using FastMT processing with modifications to add new pixel based Occluded Area weighting

• Quadratic model used to level the intensity within the image before performing defect detection (Contrast Ratio method).

• Processed Images and computed weighted OA for eight samples of 12-lens MT’s, seven steps (C, M0, M1-5)

• Reduced OA to mean of the five cases (M1-M5) for total of 96 data points (8 samples x12 lenses)

• Defect pixel maps supplied as inputs to the modeling and loss calculations

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Multimode Loss CalculationsOverview

The multimode dust loss* is calculated based on two inputs:• The distribution of dust particles: D(x,y)• The distribution of light: I(x,y)This Calculated Loss is in strongly correlated with the Measured Loss. The Calculated Loss is nearly identical to the Simulated Loss determined by optical modeling.

*The “dust loss” is the additional losscaused by the presence of dust

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Estimate of the Beam Diameter

• Fiber numerical aperture: NA = 0.2• The lens plate comprises 12 collimating lenses with an index of

refraction n = 1.512 and distance from fiber endface to lens apex L = 0.53 mm

• Source: JGR MBR5 SLED @ 850 nm (Encircled Flux Launch conditions)

• Estimated beam diameter d = 0.140 mm

mm 0.140512.1

)2.0)(mm 0.53(2

NA2tan2

==

⋅≈≈

nLLd θ

θsinNA ⋅= n

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Multimode Power Transmission Through DustIn the absence of dust, the power in a beam of light is the integral of the intensity distribution over a surface that is perpendicular to the optical axis.

We define the dust transmissivity as

The fraction of the power transmitted by a dusty surface is

In a low-loss multimode system, all of the power that is transmitted through the dusty surface is coupled into the receiving fiber or detector.

∫∫∫∫ =⋅= dxdyyxIdAIP ),(

⎩⎨⎧

=otherwise1

present isdust where0),( yxD

∫∫∫∫=

dxdyyxI

dxdyyxDyxIT

),(

),(),(MM Dust,

MM Dust,10MM Dust, log10(dB)IL T−=

CircularDustParticleBlocksRaysofLightinaZemaxModel

Dust

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Multimode Intensity Distribution

The intensity distribution at the lens surface is approximated by a quadratic function of radius [cf. This is the distribution at the endface of a graded-index multimode fiber with overfilled launch (OFL) conditions].

For this particular data set, the dust data is only valid within a maximum radius rmax. This limit is therefore included in the intensity function:

Note that the launch conditions for the experiment meet encircled flux launch (EFL) conditions. A quadratic function is a reasonable, simple approximation to the actual intensity distribution.

( )⎩⎨⎧ ≤≤−

=otherwise00/1),(

2 arararI

( )⎩⎨⎧ ≤≤−

=otherwise0

)min(0/1),,( max2

maxa,rrarrarI

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Calculating the Multimode Dust Loss

I(x,y) D(x,y) I(x,y)D(x,y)

∫∫∫∫=

dxdyyxI

dxdyyxDyxIT

),(

),(),(MM Dust,

SumoverallpixelsSumoverallpixels

X =

White: D(x,y)=1(nodust)Black:D(x,y)=0(dust)

Calculated IntensityDistribution

Measured DustDistribution

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Image ProcessingRaw Leveled Particles

Intensity Final

X

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Comparison of “Raw” and “Final” ImagesRaw Final

Inthisexample, theareaobscuredbydust isunderestimated, thereforetheCalculatedLoss is lowerthantheMeasured Loss

Measured Loss=1.46dB Calculated Loss=1.04dB

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Calculated vs. Measured Loss

Calculated Loss=Measured Loss x0.768(3σ =0.009)R2 =0.993;3σy =0.38dB

Scale0– 20dB

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Calculated vs. Measured Loss: 0 – 5 and 0 – 1 dBScale0– 5 dB

12Lenses haveanaverageMeasuredDustLossgreaterthan0.6dB.The image dataforthese pointsareshowninthe “backup”slides.

Scale0– 1dB

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Optical modeling

.The lensmaterial hasanindexofrefractionn = 1.51;thenumerical aperture(NA)ofstandard50μmgraded indexfiber is0.2;andthedistance fromthefiberendface tothe lensapex isL = 0.53 mm.Theestimated beamdiameter istherefore2a ≈2L⋅NA/n =0.14 mm.

X

Y

Z

Gradedindex50µmfiber

Lenswithmaterialindexof1.51

0.53mm 0.6mm 0.53mm

Beamsize:0.14mm

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Overfilled launch vs encircled flux launch

Overfilled launchcondition caneasily besetup inaraytracebased opticalmodelingsystem. Itcanalsorepresented withaquadratic distribution inanalyticalmodel. Todemonstrate theconsistency betweenOFLandEFL,anstandard launchcondition forconnector insertion loss testspecified byIEC61280-4-1,aninvestigation is launched.

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Launch condition investigation, OFL vs EFL

OFLprofileatlenssurface EFLprofileatlenssurface

140um

50um

OFLprofileatfibersurface EFLprofileatfibersurface

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Comparison of simulated IL data

Simulation iscarriedoutforselected numberconnectors forinsertion loss usingbothOFLandEFLlaunchconditions andtheresults showshighdegreeofagreement between thetwolaunchconditions. Itfurther legitimize theuse ofquadraticdistribution ofintensity forlosscalculation inanalytical modeling.

y=0.9778x+0.0144R²=0.99992

0

5

10

15

0 5 10 15

Insertionlossund

erEF

Lcon

ditio

n(dB)

InsertionlossunderOFLcondition(dB)

EFLvsOFL, insertionlosssimulationdata

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Examples of modeled contaminated surface

0.0000

13.1175

26.2349

39.3524

52.4699

65.5874

78.7048

91.8223

104.9398

118.0572

131.1747

lens plate connector.zmxConfiguration 1 of 1

Image Diagram

5/25/2016Image Width = 0.2000 Millimeters, 200 x 200 pixelsField position: 0.0000, 0.0000 mmPercent efficiency: 33.367%, 3.337E-001 WattsSurface: 6. Units are watts per Millimeters squared.

0.0000

13.1174

26.2349

39.3523

52.4697

65.5872

78.7046

91.8220

104.9395

118.0569

131.1743


Image Diagram


0.0000

11.3685

22.7369

34.1054

45.4739

56.8424

68.2108

79.5793

90.9478

102.3162

113.6847


Image Diagram


Sample0011,Fiber07 Sample0011,Fiber10 Sample008,Fiber2

Simulated loss:1.11dBCalculated loss: 1.17dBMeasured loss:1.70dB



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Calculated vs Simulated Data

Excellent correlation between twomodeling methods isachieved.

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Summary• An analytical method of calculating loss under contaminated

conditions was shown to be nearly identical to an optical simulation using OFL or EFL launch conditions, and agrees reasonably well with experimental data.

• The analytical calculation requires a knowledge of the intensity distribution and a measurement of the dust distribution.

• In many cases, the simple quadratic intensity function presented here may provide acceptable results, in which case only a single parameter is needed: the diameter of the intensity distribution at the contaminated surface.

• This calculation can be easily incorporated into existing connector inspection equipment, which can use this information to generate both a pass/fail message and an estimate loss

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Conclusions• A simple analytical calculation is used to estimate the dust loss of

an expanded beam connector.

• Calculation of a single value, proven to be related to a key optical property of the link, is an ideal foundation for cleanliness specification for lens devices.

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A Proposed Cleanliness Specification forExpanded Beam Connectors

The cleanliness of a lensed surface is quantified by:• Specifying the intensity distribution at the lensed surface• Measuring the distribution of dust on this surface• Calculating the lossThe Calculated Loss is compared to an Acceptable Loss Limitto determine whether a dusty lens is a “PASS” or “FAIL”

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Next steps• Development of Cleanliness inspection criteria for expanded beam

connectors- Phase II• Additional data collection and analysis for different types of

expanded beam connectors• Collaboration with the standards bodies

• iNEMI research can be used as a baseline for the development of inspection criteria for expanded beam connectors

• Present the iNEMI research to IEC, 86B, WG4 members at 80th

IEC General meeting, Frankfurt, Germany, Oct 10-14

www.inemi.orgEmailcontacts:DavidGodlewski

[email protected]

[email protected]

[email protected]

42

Test & Measurement Equipment• IL meter: JGR MBR5 SLED @ 850nm (meeting encircled flux

specification).• FastMT 200 from FiberQA was used to capture lens photos

and dust size/location.

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From one measurement to the next, dust may move or may be added to or removed from the sample.• Calculate the “center of mass” of the dust distribution• Weight the dust data by the intensity distribution

If the denominator is zero (no dust in the beam path) thenxC = yC = 0

∫∫∫∫

−

−⋅=

dxdyyxDyxI

dxdyyxDyxIxxC )],(1)[,(

)],(1)[,(

∫∫∫∫

−

−⋅=

dxdyyxDyxI

dxdyyxDyxIyyC )],(1)[,(

)],(1)[,(

Average Dust Position (Weighted)

1ifdust ispresent0elsewhere

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M11.043.0

12.9

Dust in Motion!A B

Calc. IL(dB)xC (μm)yC (μm)

M21.22-0.99.9

M31.24-0.810.2

M41.201.7

10.3

M51.191.5

10.6

A) Anadditional piece ofdustentersthe image• Calculated loss increases 0.18dB;xC decreases by3.9μm;yC decreases by3.0μm

B) Thedustmergeswithotherdust• Calculated loss decreases 0.04dB;xC increases by2.5μm;yC remains thesame

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Raw and Final Images (1 of 3)Sample 0010,Fiber07

17.55dB13.68dBSample 0010,Fiber06

4.19dB3.23dB

Sample 0008,Fiber014.54dB3.21dB


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Raw and Final Images (2 of 3)Sample 0011,Fiber10

1.38dB1.22dBSample 0011,Fiber07

1.67dB1.17dB



47

Raw and Final Images (3 of 3)





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