Development of Cleanliness Specification for Expanded Beam Connectors Project. End of Project Brief. July 20, 2016

Transcription

1 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 2

3 Development Cleanliness Specification Standards Development IEC Scratch Recognition Task Force MM Expanded Beam - Visual Inspection Criteria IEC TR IEC/TR Expanded beam MM connectors IEC IPC Optical Signal Performance Fiber Optic End-Face Inspection, Phase I, II Sumitomo transceiver study Particles Thickness Project Lens-based transceiver initial study Impact of connector RL on 40G transmission Completed projects Projects in progress New Projects

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. What does a cleanliness specification mean for Mega Data Centers? How clean must an expanded beam connector be to meet optical performance requirements? What is the impact of contamination/scratches on the optical performance of expanded beam connectors? How can Data Center costs (cleaning) be reduced by development of a cleanliness specification that is based on a quantitative approach and is accepted by the industry? Ref: Project Collateral 4

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 5

6 Project Plan & Milestones Task Complete Q1 Q2 Q3 Q4 1. 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,

7 Overview Experimental Measurement Image Processing Multimode Dust Loss Calculations Raytrace based modeling Comparison of Measured and Calculated Loss Conclusions Next Steps 7

8 Goal To quantify the impact dust has on IL on MT12F MM Lens plate (Molex VersaBeam) 8

9 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. 9

10 Cross Section of Mated Lens Plate The 12F lens plate is a collimated lens with an index of refraction of and distance from fiber endface to lens apex 0.53mm. 10

11 Experimental Measurement Flowchart M0 Record initial photos of the DUT and launch cable Mate Record IL De-Mate Add Dust Mn Repeat n = 1 to 5 Record photos of DUT. Clean launch cable if dust is present Mate Record IL De-Mate MC Clean DUT and launch cable Record photos of DUT and launch cable Mate Record IL De-Mate 11

12 Examples of Fine Dust S/N 005 F7 M0 M5 M C

13 Examples of Fine Dust S/N 005 F7 M0 M5 MC 0.42dB 0.76dB Delta IL from M0: +0.34dB 0.42dB

14 Examples of Coarse Dust S/N 08 F1 M0 M5 M C

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 15

16 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 16

17 CR Leveling of Uncontaminated Lens Raw Leveled White banding at edge of lens caused by mismatch in quadratic model to actual shape. Final data used a larger diameter to reduce this effect. 17

18 CR Leveling of Highly Contaminated Lens Raw Leveled Part ID: Process Set 6, Sample 10, M1, Fiber 03 18

19 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 19

20 Example OA: S-008, C, Fiber-01 Leveled Detected Defects OA Rings* *Final data was computed using a pixel based weighting function rather than the earlier OA rings shown here 20

21 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 21

22 Multimode Loss Calculations Overview 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 loss caused by the presence of dust 22

23 Estimate of the Beam Diameter Fiber numerical aperture: NA = 0.2 The lens plate comprises 12 collimating lenses with an index of refraction n = and distance from fiber endface to lens apex L = 0.53 mm Source: JGR MBR5 850 nm (Encircled Flux Launch conditions) Estimated beam diameter d = mm NA = n sinθ d = 2L NA 2L tanθ n 2(0.53 mm)(0.2) = mm 23

24 Multimode Power Transmission Through Dust In 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 P = I da I( x, y) dxdy 0 D( x, y) = 1 where dust is present otherwise The fraction of the power transmitted by a dusty surface is T Dust, MM = I( x, y) D( x, I( x, y) dxdy y) dxdy 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. IL Dust, MM (db) = 10log 10 T Dust, MM Dust Circular Dust Particle Blocks Rays of Light in a Zemax Model 24

25 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]. 2 1 ( r / a) 0 r a I( r, a) = 0 otherwise For this particular data set, the dust data is only valid within a maximum radius r max. This limit is therefore included in the intensity function: 2 1 ( r / a) 0 r min( a,rmax) I( r, a, rmax) = 0 otherwise 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. 25

26 Calculating the Multimode Dust Loss Calculated Intensity Distribution Measured Dust Distribution I(x,y) D(x,y) I(x,y)D(x,y) X = Sum over all pixels T Dust, MM = I( x, y) D( x, I( x, y) dxdy y) dxdy Sum over all pixels White: D(x,y) = 1 (no dust) Black: D(x,y) = 0 (dust) 26

27 Image Processing Raw Leveled Particles Intensity Final X 27

28 Comparison of Raw and Final Images Raw Final Measured Loss = 1.46 db Calculated Loss = 1.04 db In this example, the area obscured by dust is underestimated, therefore the Calculated Loss is lower than the Measured Loss 28

29 Calculated vs. Measured Loss Scale 0 20 db Calculated Loss = Measured Loss x (3σ = 0.009) R 2 = 0.993; 3σ y = 0.38 db 29

30 Calculated vs. Measured Loss: 0 5 and 0 1 db Scale 0 5 db Scale 0 1 db 12 Lenses have an average Measured Dust Loss greater than 0.6 db. The image data for these points are shown in the backup slides. 30

31 Optical modeling Lens with material index of 1.51 Beam size: 0.14mm Graded index 50µm fiber 0.53mm 0.6mm 0.53mm. The lens material has an index of refraction n = 1.51; the numerical aperture (NA) of standard 50 μm graded index fiber is 0.2; and the distance from the fiber endface to the lens apex is L = 0.53 mm. The estimated beam diameter is therefore 2a 2L NA / n = 0.14 mm. 31

32 Overfilled launch vs encircled flux launch Overfilled launch condition can easily be setup in a raytrace based optical modeling system. It can also represented with a quadratic distribution in analytical model. To demonstrate the consistency between OFL and EFL, an standard launch condition for connector insertion loss test specified by IEC , an investigation is launched. 32

33 Launch condition investigation, OFL vs EFL OFL profile at fiber surface EFL profile at fiber surface 50um OFL profile at lens surface EFL profile at lens surface 140um 33

34 Comparison of simulated IL data Simulation is carried out for selected number connectors for insertion loss using both OFL and EFL launch conditions and the results shows high degree of agreement between the two launch conditions. It further legitimize the use of quadratic distribution of intensity for loss calculation in analytical modeling. 15 EFL vs OFL, insertion loss simulation data Insertion loss under EFL condition (db) 10 5 y = x R² = Insertion loss under OFL condition (db) 34

35 Examples of modeled contaminated surface Sample 0011, Fiber 07 Sample 0011, Fiber 10 Sample 008, Fiber Simulated loss: 1.11dB Calculated loss: 1.17dB x m z. r o t c e n n o c e t a l p s n e l 1 f o 1 n o i t a r u g i f n o C m a r g a i D e g a m I Simulated loss: 1.21dB m a r g a i D e g a m I / 5 2 / / 5 2 / 5 s l e x i p x 0 0 2, s r e t e m i l l i M = h t d i W e g a m I s l e x i p x 0 0 2, s r e t e m i l l i M = h t d i W e g a m I m m , : n o t i s o p d l e i F m m , : n o t i s o p d l e i F t t a W x E m 4 8 z 2. r 3 o t, % c 3 e 4 n 8 n. o 2 3 c : e y t c a n e l i p c i s f n f e l t n e c e P t t a W E , % : y c n e i c i f f e t n e c e P. d e r a u q s s r e t e m i l 1 l i M f r o e p 1 s t t n a o w i e t r a r s u t i g n i U f. n 6 o : C e c a f r u S. d e r a u q s s r e t e m i l l i M r e p s t t a w e r a s t i n U. 6 : e c a f r u S Calculated loss: 1.22dB Simulated loss: 1.96dB Calculated loss: 1.99dB Measured loss: 1.70dB Measured loss: 1.38dB Measured loss: 1.88dB 35

36 Calculated vs Simulated Data Excellent correlation between two modeling methods is achieved. 36

37 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 37

38 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. 38

39 A Proposed Cleanliness Specification for Expanded 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 loss The Calculated Loss is compared to an Acceptable Loss Limit to determine whether a dusty lens is a PASS or FAIL 39

40 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 80 th IEC General meeting, Frankfurt, Germany, Oct

41 contacts: David Godlewski Haley Fu Bill Bader

42 Test & Measurement Equipment IL meter: JGR MBR5 850nm (meeting encircled flux specification). FastMT 200 from FiberQA was used to capture lens photos and dust size/location. 42

43 Average Dust Position (Weighted) 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 x I( x, y)[1 D( x, y)] dxdy x C = I( x, y)[1 D( x, y)] dxdy y I( x, y)[1 D( x, y)] dxdy y C = I( x, y)[1 D( x, y)] dxdy 1 if dust is present 0 elsewhere If the denominator is zero (no dust in the beam path) then x C = y C = 0 43

44 A Dust in Motion! B M1 M2 M3 M4 M5 Calc. IL (db) x C (μm) y C (μm) A) An additional piece of dust enters the image Calculated loss increases 0.18 db; x C decreases by 3.9 μm; y C decreases by 3.0 μm B) The dust merges with other dust Calculated loss decreases 0.04 db; x C increases by 2.5 μm; y C remains the same 44

45 Raw and Final Images (1 of 3) Sample 0010, Fiber db db Sample 0010, Fiber db 3.23 db Sample 0010, Fiber db 1.99 db Sample 0008, Fiber db 3.21 db 45

46 Raw and Final Images (2 of 3) Sample 0011, Fiber db 1.17 db Sample 0011, Fiber db 1.22 db Sample 0010, Fiber db 0.84 db Sample 0011, Fiber db 0.70 db 46

47 Raw and Final Images (3 of 3) Sample 0011, Fiber db 0.76 db Sample 0008, Fiber db 1.19 db Sample 0010, Fiber db 0.67 db Sample 0010, Fiber db 0.29 db 47