Optical Time Domain Reflectrometry The Smart Way

Transcription

1 Optical Time Domain Reflectrometry The Smart Way Christian Schillab Product Manager Media Test Fluke Networks Europe Member British Standards Institute Working Group TCT 7/-/1 & CENELEC TC215 WG1 PTH und PTT

2 Optical Time Domain Recflectrometry The Smart Way The discussion on whether OTDRs are the right tools to test new installations for compliance is fueled by common practices which try to balance simplicity with achieving relevant test results. In This presentation, we describe new methods and procedures which deliver highly accurate and repeatable results and, at the same time, significantly reduce the overall testing time.

3 Agenda OTDRs have a point of view Normative requirements Comparison of methods Using a loop to accelerate the test Smart support for loop testing Cost comparisons for the different methods

4 Fiber Optic Test Methods Standard Tier-1 Methods TIA-568-C Tier-2 ISO AMD.1 / ISO/IEC BASIC Test Regime LSPM: Light Source & Power Meter EXTENDED Test Regime OTDR: Optical Time Domain Reflectometer The two methods are complimentary! OTDR based method does not replace the LSPM based solution Both methods have advantages and limitations

5 From The Archive. BICSI 2012 The next 6 slides are from a 2012 presentation

6 OTDR s Have Multiple Points of View db db 0.33 db 0.32 db db db

7 Causes for Directivity Potential causes for different results depending on the direction 1. Two fibers are different Diameter Back Scatter Index NA. Numerical Aperture Major difference in IR Index of Refraction 2. Damaged fiber end faces Glass is chipped off

8 Bi Directional Averaging The averaging can be performed manually or by an advanced results management software

9 Can We Quantify Directivity? No standard defines how to calculate it but it is simple ISO/IEC defines no maximum allowed directivity

10 How to Quantify Directivity Delta of measured loss from End-1 and End-2 divided by Δ (-0.23 and 0.41) / 2 = 0.64 / 2 = 0.3dB Δ (0.44 and ) / 2 = 0.64 / 2 = 0.3dB In this example: Prior to averaging the result will be over stated by 0.30dB in one and understated by 0.3dB in the other directions NOTE: The overall loss is not suffering from directivity Only if launch and receive fiber exhibit no directivity if tested without a link

11 Common Practices Voice of the Customer... In EMEA a majority of text in SOWs (Standards Of Work) specify a bi-directional test but not the use of a tail fiber If use of a tail fiber is specified a match with the launch fiber is typically not mentioned as a requirement

12 Bi-Directional OTDR Tests Without a Tail Fiber 0.15 db 0.28 db 0.20 db Question: Can we trust the results? Is the total loss = 0.48dB? Answer: A bi-directional test without the use of a tail fiber test is the best way. to PASS non compliant or to FAIL compliant links

13 we re-measure the link the correct way A. We retest the link using a launch fiber plus a tail fiber Can we trust the results? Is the total loss = 0.48dB? B. We use Bi-Directional averaging to get the ultimate information and we observe.. End 1 End 2 1. The result should have been a FAIL 2. Overall loss was wrong by 43% We observe 3. Connector loss was wrong by 62% and 87%

14 First Embedded Last Overall Loss Technicians Required Testing Time Accuracy of Methods Compared Launch Fiber Tail Fiber Connections Launch n/ 1 x Launch & Tail Uni- Directional a / 2 x Launch n/ 1 2x Bi- a Excellent / Hi Relevane Directional Launch & Tail 2 2x Poor / Hi Uncertainty n/a not available

15 Alternative Methode using a Loop Launch A Loopback Tail B 1. Tests A and B fiber simultaneously 2. In a second step from the other direction 3. The individual segments need to be identified in the trace

16 Alternative Method Using a Loop A B Launc h Loopback Tail A B Nn,mn,m

17 Pros & Cons of Loop Testing A B PROs Total time for trace acquisition time is halved For Launch & Tail Fiber the number of mating's is halved Use of multiple Loop Fibers allow a single technician to walk less often to the other end CONs Each trace needs to be saved two times after identifying Fiber A and then Fiber B Extensive cursor setting and saving results multiple times is a common source of error Fiber A from End1 Fiber B from End1 Fiber A from End2 Fiber B from End2

18 Concept of Smart Loop Testing The OTDR automatically identifies Fiber A and B for both both test From End 1 From End 2 The OTDR saves 4 test results in one pass The OTDR automatically learns the correct lengths of Launch / Loop / Tail Fibers

19 Test Results Navigation Tap to toggle between fibers A and B Tap to toggle between Ends 1 and 2 The loopback fiber is always End 2

20 Pros & Cons of Smart Loop Testing A B PROs Total time for trace acquisition time is halved For Launch & Tail Fiber the number of mating's is halved Use of multiple Loop Fibers allow a single technician to walk less often to the other end CONs Each trace needs to be saved two times after identifying Fiber A and then Fiber B Extensive cursor setting and saving results multiple times is a common source of error Fiber A from End1 Fiber B from End1 Fiber A from End2 Fiber B from End2

21 Smart Loop Testing / 2 Technicians Comparing testing for 6 links (12 fibers) The time saving is a minimum of 50%

22 Smart Loop Testing / 1 Technician 3 remote loop are used to reduce the number of walks to the other end The time saving is typically > 33%

23 Cost Saving Calculation Find copy at danahertm.box.com/slcal

24 Cost Saving Calculation / Example 1 Smart Loop versus no loop 2 Technicians Cost Saving 50% Find copy at danahertm.box.com/slcal

25 Cost Saving Calculation / Example 2 Smart Loop versus Dumb loop 1 Technician 6 loop fibers are used Cost Saving 39% Find copy at danahertm.box.com/slcal

26 Conclusions

27 Thank You! for Your Attention I would be happy to answer an further question christian.schillab@flukenetworks.com