1. Fiber Optic Testing Optical Educational Seminar Tim Percival EXFO 18 th February 2016 BICSI Breakfast Meeting Lagos, Nigeria

2. AGENDA 1Fiber Optic Basics 2Common Measurements Insertion Loss Optical Return Loss 3Connector Inspection and Cleaning 4OTDR Testing 5Intelligent OTDR’s

3. 3 © 2012 EXFO Inc. All rights reserved. ›Measurement units: dB or dBm? ›Use the dBm unit when talking about the Power Level (an absolute value measured at a specific point in a link) › Example: Power coming out of a transmitter › 1mw = 0dBm, 1uw = -30dBm ›Use the dB unit when talking about the LOSS (a referenced value) › Example: Loss of a fiber section Loss and Power measurement units - Difference between dB and dBm Loss dB Power Remaining % 0100 0.295.5 0.491.2 0.687.7 0.883.2 179.4 263.1 350.1 439.8 531.6 625.1 719.9 815.8 912.6 10 201 300.1 400.01 500.001 Trick to remember: 3dB of loss = 50% of power lost !

4. 4 © 2012 EXFO Inc. All rights reserved. Loss in fiber is wavelength-dependent Fiber Types Optical fiber is normally tested at the same wavelength as the fiber system will be operated Available OTDR wavelengths: 850 nm (MM) 1300 nm (MM) 1310 nm (SM) 1383nm (SM) – Water Peak 1490nm (SM) - PON 1550 nm (SM) 1625 & 1650nm (SM) Water peak Corning SMF-28 SM «G652A_B» Fiber Corning SMF-28 SM «G652D» Fiber Newer G.652D fiber has the water peak at 1383nm significantly reduced. 1310nm and 1550nm remain unaffected. Over 95% of world fiber is G652 family.

5. 5 © 2012 EXFO Inc. All rights reserved. Fiber Optic Cable / Multimode And Single-mode Typical Loss (Attenuation) 1 km Single-mode Fiber Multimode Fiber 1625nm 1310nm 1300nm 850nm 0.22dB 0.35dB 2.50dB 0.50dB 1490nm 1550nm0.20dB 0.22dB

6. 6 © 2012 EXFO Inc. All rights reserved. › Fibers are made of glass consisting of a core and a cladding that will allow propagation of light by total internal refraction. › Total internal refraction is achieved in the fiber by having two different refractive indexes – the core IOR is higher than the cladding IOR Fiber Construction Fiber Cladding The cladding IOR is slightly lower than the core IOR. This will “bend” the light to keep it in the core area. Fiber Core Will act as a “mirror tunnel” for the light propagation. Core IOR > Cladding IOR

7. 7 © 2012 EXFO Inc. All rights reserved. Telecom Fiber Types SinglemodeMultimode 9/125 (µm) Core 50/125 (µm) Cladding Core Cladding 62.5/125 (µm)

8. 8 © 2012 EXFO Inc. All rights reserved.  Decrease in average optical power from the transmitter to the receiver  Link loss determines the maximum distance between a transmitter and a receiver.  Attenuation results from: 1.Fiber Absorption/Scattering 2.Connectors (.3 -.5dB ea typ) 3.Fusion Splices (0.1dB ea typ ) 4.Macrobends  Loss budget assessment  Fiber Loss is wavelength-dependent*  1310nm –.35db/km typ  1550nm –.2db/km typ *Testing must be performed at transmitting wavelengths Attenuation/Fiber Loss

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11. 11 © 2012 EXFO Inc. All rights reserved. i r ir =

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13. 13 © 2012 EXFO Inc. All rights reserved. Macrobend

14. Common Measurements

15. What needs to be tested? Connector Cleanliness Optical power budget (end-to-end loss) Optical power levels at ONT Component insertion loss (IL) ORL and reflectance

16. 16 © 2012 EXFO Inc. All rights reserved. What to look for during the construction? Loss Budget Loss Budget Macrobends Insertion Loss Splice and Connector Insertion Loss Splice and Connector Link ORL Connector cleanliness

17. 17 © 2012 EXFO Inc. All rights reserved. ControlledUncontrolled Connector CleanlinessDistance Launch ConditionsAttenuation Connector MateMacrobends Test ParametersIOR Variables Fusion Splice Bend Connector Pair Crack Fiber End Mechanical Splice Typical Fiber Link Tx Rx

18. 18 © 2012 EXFO Inc. All rights reserved. What is Loss Testing? Optical Loss Testing is a test performed to determine the loss in energy within a device or fiber The Loss is a result of attenuation from absorption, scattering, microbending, macrobending, connectors, splices, and discontinuities in the fiber span or device. insertion loss [dB] = P out [dBm] – P in [dBm] insertion loss [dB] = 5 [dBm] – Pin [dBm]insertion loss [dB] = 5 [dBm] – 1 [dBm]insertion loss [dB] = 5 [dBm] – 1 [dBm] = 4 dB of LOSS!

19. 19 © 2012 EXFO Inc. All rights reserved. Optical Return Loss (ORL)

20. 20 © 2012 EXFO Inc. All rights reserved. ∑ Fresnel Reflection ∑ Backscattering ORL HIGH ORL LOW ORL Optical Return Loss

21. 21 © 2012 EXFO Inc. All rights reserved. ›The faster we transmit, the less we can tolerate Optical Return Loss 01010101010101010101111111111111111111111 Historic “slow” 1GigE Signal 0 1 0 1 0 1 0 Clean Connectors Today’s 10GigE Signal Clean ConnectorsDirty Connectors Typical ORL Thresholds –1GE = 26 dB –10GE = 29 dB –100GE = 31 dB –PON = 32 dB

22. Connector Inspection and Cleaning

23. 23 © 2012 EXFO Inc. All rights reserved. ›Polishing types : ›UPC type ›UPC connectors are “flat” polished ›Most UPC singlemode connectors are blue ›Flat Polished connectors includes: ›PC; SPC; UPC ›-50 to -55db Typical Connectors UPC Connector Flat Polished Connector The ferrule is flat polished

24. 24 © 2012 EXFO Inc. All rights reserved. ›Polishing types: ›APC type ›Most APC connectors are green ›APC is used in single mode applications only ›APC connectors will give a very low reflection (low ORL) ›-60 to -65db Typical Connectors OptiFit Connector APC Connector inside Angle Polished Connector The ferrule is polished with an 8° angle

25. 25 © 2012 EXFO Inc. All rights reserved. !!! Warning !!! Angle Polished Connectors cannot be connected with Flat Polished Connectors! Connectors

26. 26 © 2012 EXFO Inc. All rights reserved. Connector Inspection Connector end face should look like … This …And not like this … Oil Burnt

27. 27 © 2012 EXFO Inc. All rights reserved. Connector inspection ›Connector inspection requires a great amount of judgment ›Should I change/clean this connector or not?

28. 28 © 2012 EXFO Inc. All rights reserved. › FACT : Size and location of defects must be measured down to microns › FACT : It is virtually impossible to qualify a connector against a standard visual inspection Connector Inspection PASS OR FAIL ?

29. 29 © 2012 EXFO Inc. All rights reserved. Criteria are defined in the following standards: ›IEC 61300-3-35 Fiber-Optic Interconnecting Devices and Passive Components— Basic Test and Measurement Procedures http://webstore.iec.ch/ ›IPC 8497-1 Cleaning Methods and Contamination Assessment for Optical Assembly http://www.ipc.org/ These specifications dictate the acceptable quantity, size and location of defects and contamination. Connector Inspection Criteria

30. 30 © 2012 EXFO Inc. All rights reserved. ›A connector endface is divided into multiple zones ›Dimensions will depend on the connector and fiber type IEC 61300-3-35 Connector Inspection Criteria

31. 31 © 2012 EXFO Inc. All rights reserved. Automation can help you comply to IEC and IPC standards if necessary Pass/Fail Analysis Software ›Where are the zones? ›What is the size of each particle? ›How many defects are there? ›Am I exceeding the limits?

32. 32 © 2012 EXFO Inc. All rights reserved. Using an analytical software allows to: ›Guarantee a uniform level of acceptance: ›Between users within an organization ›Between suppliers and customers ›Between contractors and network owners ›Facilitate decision process by removing subjectivity Pass/Fail Analysis Software

33. 33 © 2012 EXFO Inc. All rights reserved. Dry method ›An efficient technique for removing light contaminants ›Often considered the technique of choice in a controlled manufacturing environment where speed and ease of use are important factors Example of dry cleaning supplies: ›Specialized lint free wipes and swabs ›Mechanic cleaning devices Cleaning

34. 34 © 2012 EXFO Inc. All rights reserved. Wet method ›The main purpose of using the wet-solvent approach is to raise dust and contaminants from the connector’s endface to avoid scratching the connector ›The most widely-known solvent in the industry is the 99.9% isopropyl alcohol (IPA), which removes most contaminants Example of wet cleaning supplies: ›Pre-saturated swabs Cleaning

35. 35 © 2012 EXFO Inc. All rights reserved. Combination method (hybrid) ›Combination cleaning is a mix of the wet and dry cleaning methods ›The first step in hybrid cleaning is to clean the connector end-face with a solvent and to dry any remaining residue with either a wipe or a swab Example of combination cleaning supplies: ›Specialized wipes and solvents Cleaning

36. 36 © 2012 EXFO Inc. All rights reserved. Dust/dirt residues transfer: ›If not cleaned properly: Residues will transfer and may create permanent damage when mating Connector Issues Patch Panel After mating: Before mating: Did you know ? Connector A Connector B

37. OTDR Testing

38. 38 © 2012 EXFO Inc. All rights reserved. OTDR – A tool of choice, WHY? It reveals: Total LossOptical return LossFiber Length It is used for: Characterize the link components Highlight a potential problem Locate a fault

39. 39 © 2012 EXFO Inc. All rights reserved. Reflectometry Theory

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44. 44 © 2012 EXFO Inc. All rights reserved. EVENT TABLE

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46. 46 © 2012 EXFO Inc. All rights reserved. OTDR Distance Range Before the OTDR can launch a 2 nd or 3 rd pulse it must wait long enough to allow all the reflections to have returned from the end of the optical fiber. If it launched the 2 nd (or subsequent) pulse too soon then the reflections from multiple pulses would arrive together leading to a meaningless trace. The OTDR can be set to display a specific length of fiber and this setting (Distance Range) also tells the algorithm how long to wait before launching the next pulse. It is important to set the distance range to a value slightly greater than the length of the fiber. End-Face Connector

47. 47 © 2012 EXFO Inc. All rights reserved. OTDR Average Time By the time the primary pulse reaches the end of a relatively long optical fiber, most of its energy has been dissipated. The OTDR records the results of the first pulse then launches another and then another. It ‘averages’ the results of multiple pulse launches to give the operator a clean trace. Typical average times range from 5 seconds to 3 minutes. End-Face Connector

48. 48 © 2012 EXFO Inc. All rights reserved. OTDR Pulse Width Another important parameter is the Pulse Width. Put simply, the longer the LASER stays on the more energy is injected into the fiber and the greater the effective range. It would seem that one would always select a long pulse-width, then. However, a long pulse also generates an equally long reflection. If the LASER stays on for 10 microseconds then the pulse itself will be approximately 2 kilometers long (1.24 miles). Choose a shorter pulse width to separate closely spaced events or a longer pulse width for range.

49. 49 © 2012 EXFO Inc. All rights reserved. Pulse Width

50. 50 © 2012 EXFO Inc. All rights reserved. OTDR -- Basic parameter: Pulse Width Short pulses will give a better resolution but less dynamic range: Long pulses will give a better dynamic range but less resolution: Two connectors 3 meters apart End of link (patch panel) Connectors are « merged » and identified as one event Connectors are measured for distance and marked as separate events 5ns pulse 30ns pulse

51. 51 © 2012 EXFO Inc. All rights reserved. Event dead zone The event or reflective dead zone represents the minimum distance between the beginning of a reflective event and the point where a consecutive reflective event should clearly be recognized. OTDR specifications & limitations It is the distance between: The beginning of the events the -1.5 dB point on the falling edge 1.5 dB Event Dead Zone If a reflective event is outside the Event Dead Zone of the preceding event, it will be localized and the distance will be calculated.

52. 52 © 2012 EXFO Inc. All rights reserved. Attenuation dead zone Dead zone concerns only reflective events The attenuation or non-reflective dead zone is the minimum distance after which a consecutive reflective event and attenuation measurement can be made. OTDR specifications & limitations Attenuation Dead Zone 0.5 dB It is the distance between: The beginning of the events the point on the falling edge where the receiver sees a value around  0.5dB from the normal backscatter trace If a reflective or non-reflective event is outside the Attenuation Dead Zone of the preceding event, it will be localized and measured for loss.

53. 53 © 2010 EXFO Inc. All rights reserved.. 53 © 2012 EXFO Inc. All rights reserved.

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56. 56 © 2012 EXFO Inc. All rights reserved. Launch Test Cable A launch and/or receive fiber allows the OTDR Operator to “see” the entire fiber from start to finish.

57. 57 © 2010 EXFO Inc. All rights reserved.. Can you read this? Traditional OTDR

58. 58 © 2010 EXFO Inc. All rights reserved.. And can you read this? Intelligent OTDR

59. 59 © 2010 EXFO Inc. All rights reserved.. HOW DOES IT WORK A revolution Dynamic multipulse acquistions Intelligent trace analysis Combine all results into a single link view Display clear pass/fail with comprehensive diagnosis

60. 60 © 2010 EXFO Inc. All rights reserved.. 60 © 2012 EXFO Inc. All rights reserved. How it works? In the background What you see! Distance (m) Power (dB) Start

61. 61 © 2010 EXFO Inc. All rights reserved.. What needs to be tested? Connector Cleanliness Optical power budget (end-to-end loss) Optical power levels at ONT Component insertion loss (IL) ORL and reflectance

62. Tim Percival Sales Director EXFO E: tim.percival@exfo.com T: +44 7843 278789 www.EXFO.com