Network IQ Training Manual Chapter 6 - Fibre Testing and Measurement

Fibre Testing and Measurement Reasons for Testing Testing Standards Optical Testing Procedures Attenuation Testing Power Meter/Source Reference Mandrel Wrap Optical Time-Domain Reflectometer (OTDR) Link Testing Documentation Troubleshooting

Reasons for Testing Product Acceptance Installation Acceptance Accounting System Original Repairs Changes/Upgrades Future Reference Proof of Final System Specifications More specific items about why testing is necessary fibre optic testing of newly installed systems not only verifies that the system meets it design requirements, but also creates a performance baseline for all future testing and troubleshooting of that system

Testing Standards - Component Requirements TIA/EIA-568 Requirements Connector Pair Loss: ≤ 0.75 dB* Splice Loss of ≤ 0.3 dB Connector reflectance: ≤ -20 dB for MM ≤ -26 dB for SM Optical fibre attenuation Multimode, OM3: ≤ 3.5/1.5 dB/km @ 850/1300nm Single-mode, OS1/OS2 OSP: < 0.5/0.5 dB/km @1310/1550 nm ISO 11801 Amd:2 Requirements (Table 57 & 37) Connector Pair Loss: < 0.75dB 100% < 0.5dB 95% < 0.35dB 50% Splice Loss < 0.3dB Connector reflectance: ≤ -20 dB for MM ≤ -35 dB for SM Optical fibre attenuation Multimode, OM3/OM4: ≤ 3.5/1.5 dB/km @ 850/1300nm Single-mode, OS2: < 0.4/0.4/0.4 dB/km @1310/1383/1550 nm ATTENTION about OS1 and OS2 fibres things are very different between TIA/EIA and ISO/IEC: TIA/EIA 568.C3 (2008) OM4 is not yet included, and on SM the definitions are following: 1.0/1.0 dB/km @1310/1550 nm for OS1/OS2 Inside Plant 0.5/0.5 dB/km @1310/1550 nm for OS1/OS2 Outside Plant While in Amd. 2 ISO/IEC OM4 is included and OS1 remains 1.0/1.0 dB/km @1310/155nm while OS2 is introduced with 0.4/0.4/0.4 dB/km @1310/1383/1550 nm This slide lists out the component specifications for insertion loss, fibre attenuation, and reflectance. Instructors may point out here that factory termination products have better typical performance than field-installed products. Factory-made jumpers typically have connector pair loss of < 0.5 dB. This relatively high specification value allows for the use of field-installable connectors. Note that during link loss testing, a high loss component could easily be hidden – other components in the link with lower loss could compensate for the one high loss event. The maximum splice loss value of 0.3 dB allows for the use of mechanical splices. Fusion splices would typically be held to a tighter value because of the relative ease of obtaining fusion splice loss values below 0.15 dB. Loss values are considered directionally independent. Bi-directional testing should yield the same value for connector, splice, or fibre loss. Connector and splice losses can be considered wavelength independent for field testing purposes. There is a small difference in loss due to MFD issues, but field test equipment is generally not sensitive to note a difference. These values can be viewed as guidelines to ensure quality system components. However, systems with excessive length or a high number of connector pairs can cause the loss budget to be exceeded and prevent transmission for high data rate systems. Alternatively, low data rate systems may be able to withstand higher loss components and still function. Maximum channel loss values for Ethernet and/or fibre channel links should be consulted to determine the maximum allowable loss budget. • 0.3 dB is allowed by TIA/EIA to include the ability to utilize mechanical splices. When fusion splicing -- with pigtail splicing for example – the typical splice loss is < 0.1 dB for that fusion splice, as most fusion splice machines are able to achieve values within that range. * Each Corning Cable System module is factory-tested as one unit, not as individual connector pairs. Module loss is specified at a lower loss than the maximum allowable for two connector pairs would suggest. ** ≤ 3.5/1.5 dB/km @ 850/1300 nm for standard 50/125 fibre ≤ 1.0/0.75 dB/km @ 1310/1550 nm for single-fibre single-mode fibre ≤ 0.5/0.5 dB/km @ 1310/1550 nm for ribbon single-mode fibre Standards today allow testing of multimode systems with LED test sources, even for high speed networks that will utilize VCSELs for data transmission. LED testing should produce conservative test values as systems may see lower loss when a VCSEL is used as the source. • OFSTP-14A defines the category that a source should fall into based on a coupled power ratio. Standards compliant LEDs fit into Category 1.

Source (transmitter)… • Simulates system source (LED, LASER, or VCSEL) Attenuation Testing Source (transmitter)… • Simulates system source (LED, LASER, or VCSEL) • Creates a standard reference for continuity • Provides stable reference for fibre and component loss Meter (receiver)... • Checks continuity • Measures total fibre loss (end to end) • Optimizes splice loss • Identifies active fibre The attenuation test equipment is separated into two types of units, a source and a meter. Explain the function of each. MM systems should be tested with a category 1 source (LED) according to today’s standards. This includes systems expected to run at gigabit/s speeds and above. LED testing should produce conservatively high loss measurements compared to testing with a VCSEL source. AENote 100 compares testing with a LED and VCSEL

Attenuation Testing Checking with an Attenuation Test set will ensure correct polarity fibres can be accidentally placed in wrong ports. Attenuation testing is a 2-sided test and requires access to each end of the system. Loss is not bi-directional, and it does not matter which end of the system that the source is placed. Explain that the source and meter only provide pass/fail results and can not tell the installer what the issue is. Crossed fibres will fail the continuity check as no power will be received. This may happen if the proper components are not placed together (universal module with old PNP trunk)

Power Meter/Attenuation Testing How much water leaks from the joint/connection? What do you need to know first? 5 Ltr/min

Power Meter/Attenuation Testing Make a reference to know the strength of the source. Same as 1 Jumper reference for fibre optic testing 7 Ltr/min

Power Meter/Attenuation Testing Subtract source power from received power to determine power loss. Measured in dB (deciBel) 7 Ltr/min 7-5 = Loss (Attenuation) 2 ltr/min 5 Ltr/min

Attenuation Test Procedures - One Jumper Reference Power Ok? Press Reference (#1) Add Jumper 2, Check loss < 0.1 dB Test System Step 1 Step 2 Step 3

Attenuation Test Procedures IEC 61280-4-1, Method 2; ANSI/TIA/EIA-526-14A, Method B Three Types of Reference Set Ups: IEC 61280-4-1, Method 1 ANSI/TIA/EIA-526-14A, Method A Cover the three possible systems types and the corresponding jumper reference to be used. A patch panel to patch panel system requires a 1-jumper reference, a patch panel to end electronics system requires a 2-jumper reference and link that goes directly into electronics without patch panels at either end requires a 3-jumper reference. The one-jumper reference is the one most often used and is the most conservative. A useful equation for determining the jumper reference is derived by looking at whether the system ends at a patch panel at each end of the system compared to having the last connector plug directly into electronics (no patch cord). 3 - # patch panels = # jumper reference • For the 1-jumper reference, a second jumper is added to the set-up between the first jumper and the meter port. For the 3-jumper reference, the middle jumper is removed prior to system testing. Regardless of which reference method is utilized, two jumpers, one at the source and one at the meter, are used during the actual testing process IEC 61280-4-1, Method 3

Summary of Attenuation Testing Rule of Thumb: Nr. Jumper Reference = 3 – Nr. Patch panels in System More testing scenarios at end in “Reference” section

Multimode Source Characteristics Multimode System-related losses Overfilled or fully filled launch conditions cause light to be carried in the cladding over short distances. (higher-order modes) In order to produce consistent launch conditions, mandrel wrapping is recommended during testing (TIA/EIA-568-B.1). Explain that LEDs have a large spot size < 100 um and will completely fill up the core of multimode fibre. The excess light at the edges of the core and cladding will quickly attenuate and will not appear in the system during actual operation. However it can affect testing as the light may not completely attenuate over the 1 meter of fibre between the source and meter during referencing.

TIA-455-50-B ; IEC 61280-4-1; IEC 61300-3-4 ed 2. 2000 Mandrel Diameters for Multimode fibre Testing 50 µm 62.5 µm Mandrel diameters in millimeters for 900um fibre. If jacketed cable, subtract cable OD from mandrel diameter Fibre Core Mandrel diameter 50µm 25 mm (22 for 3mm cable) 62.5µm 20 mm (17 for 3mm cable) CCS offers mandrels for both fibre types. A special mandrel is not required for LOMMF. Note: CCS mandrels are made to hold 2.9 mm jacketed fibre. A 2.0 cable will not hold in the clasps. The mandrel diameter is larger for 50 um fibre to this fibre’s sensitivity to bending. • These diameters are proper for testing with 3 mm patch cords. The goal is to make the diameter of the fibre itself 20 mm for 62.5/125 µm fibre and 25 mm for 50/125 µm fibre. • The jumper should be wrapped around the mandrel in 5 even wraps without over-wrapping or pulling on the jumper too tightly. 50 µm mandrel part number: OTS-MAN-50 62.5 µm mandrel part number: OTS-MAN-62 Set of 1 each: OTS-COMBO-MAN TIA-455-50-B ; IEC 61280-4-1; IEC 61300-3-4 ed 2. 2000

Link Loss Measurement: Calibration and Test (MM) Review One Jumper Reference IEC 61280-4-1, Method 2 or ANSI/TIA/EIA-526-14A, Method B 1. Connect 1 patch cord from transmitter to receiver (meter) with mandrel wrap and measure the coupled power. 2. „Zero“ the meter: Set the reference for system testing. The receiver now shows the relative loss value to this reference value 3. Separate the patch cord from the receiver and connect a 2nd cord between the first patch cord end and the receiver. Displayed value is the connector pair loss between the patch cords should be <0.1dB 4. Disconnect the 2 jumpers and connect the 2 ends to the link to be tested. The test meter shows the total attenutation from the first to last connector, inclusive, of the link. (1) 850 on 0dB -8dBm Tx REF (1) (2) 850 on 0.1dB Tx

The OTDR Allows You to …. Testing the fibre from one end OTDR measures BACKSCATTER and REFLECTIONS User can see the discontinuities in the fibre Locate the fibre end (break) Locate splices (“events”) Creates a graph of distance versus attenuation Measure splice and connector losses end-to-end loss Reflectance (Optical return loss, ORL) BACKSCATTER levels determine the splice losses, connector losses and other fibre discontinuities Document fibre and archive the data Testing the fibre from one end The OTDR is a secondary test device for the data center. It is listed as a Level II test in TSB-140. Most runs are short in length and the OTDR may not even produce a readable trace. However, the OTDR is the only tool available to measure individual component loss and is useful for troubleshooting. This slide lists what the OTDR can do Discuss how the OTDR is different from an attenuation test. Only one operator is needed, the system length and individual components can be evaluated. Index of refraction (IOR) – This value needs to be entered for the fibre type. This is specified for optical fibre by the manufacturer for each wavelength. The OTDR can measure the time it takes for light to leave the OTDR and return as backscattered light; it can then use the IOR to calculate distance traveled. An OTDR measures the backscatter levels coming back from the fibre after sending out a test pulse. Since backscatter power is a percentage of the power in the transmitted test pulse, the OTDR can determine the changes in transmitted power within the fibre by looking at the difference in backscatter levels. Since the test pulse becomes gradually weaker as it moves down the fibre, the corresponding backscatter also becomes weaker. By comparing the backscatter levels between any two points in a fibre, the OTDR can determine how much light is lost between the two points. This is known as a “two-point loss” measurement. If a splice falls between the two points, then the OTDR measures the amount of light lost in the splice (the “splice loss”). Reflections are much stronger than backscatter -- about 40,000 times more powerful. OTDR detector sometimes cannot actually measure these extremely high power levels, but it does detect the reflections and displays them as being “maxed out” levels. Since reflections only come from the ends of fibres, this means an OTDR can easily detect fibre ends even when the backscatter level is very low. • Backscatter coefficient – fibre specification that gives a baseline for expected amount of backscattered light for each wavelength. Levels above this baseline will appear as a spike on the OTDR screen and represent a reflective event (connector pair or mechanical splice)

OTDR uses RADAR principle The OTDR-Principle CONTROLLER CRT or LCD DISPLAY Coupler/Splitter Tested fibre LASER(S) DETECTOR OTDR uses RADAR principle 49

OTDR - Standard Trace OTDR Launch Cable System Cable Power Time / Distance Launch Cable Connector - Patch Panel 1 System Cable Connector - Patch Panel 2

OTDR: Trace Display and Events Identification trace is a straight line with a falling slope in dB/km if the light pulse passes a location with disturbance w/o media change, a non-reflective event is registered a location with media change (glass-air-glass), a reflective event is registered due to sudden very high back scattered optical power a high drop (>3dB) usually signals a break or the end of the fibre reflective event front connector non-reflective event fusion splice reflective event connector/ mechanical splice Length attenuation dB/km non-reflective event macro bending attenuation (dB) reflective/ non-reflective event fibre end/ break Length of fibre (km)

Link Loss Budget Calculation Step 1: Determine fibre Loss at Operating Wavelength ____ (nm) Cable Length ______ (km) fibre Attenuation (per Standard @ Wavelength) _____ (dB/km) fibre Loss ______ (dB) Step 2: Determine Connection Loss Individual Connector Loss ______ (dB) (EN50173-1 Max: 0.75dB/pr.) Number of Connector Pairs x ______ Total Connector Loss ______ (dB) This and the next slide show students how to determine the expected loss based on the components in the system. Students should understand how to add the loss of components together in the system to determine the maximum loss budget. For example, the loss of each module is 1.3 dB, and one does not add in the loss of the trunk connectors, as these are included in the module loss. Remind students that this loss budget calculation does not supersede the requirements for Ethernet and Fibre Channel. Use the derating tables to verify the loss that the electronics can operate with. The loss of a module includes the loss of both connector pairs that occur at that module.

Link Loss Budget Calculation Step 3: Determine Splice Loss Individual Splice Loss ______ (dB) (EN50173 0.3dB/splice) Number of Splices x ______ Total Splice Loss ______(dB) Step 4: Determine Total System Budget Loss fibre Loss ______(dB) Connector Loss + ______(dB) Splice Loss + ______(dB) Total System Budget Loss* ______(dB) * This is the maximum acceptable loss for the system to have and meet the requirements of the standard. Total loss as calculated here is based upon component loss. A system designer must also consider the protocol running over the passive system to determine what the maximum loss that the electronics can accept.

Testing - Documentation A record that establishes “as built drawings” and can be compared to current conditions when troubleshooting. Consists of Attenuation test results* OTDR traces* Cable / assembly data sheet Route diagrams and footmarks or meter marks* Bill of material* Provides basis for system reconfiguration, upgrades and maintenance. Used for liability protection in the event multiple vendors are involved. To ensure submission of all necessary information, please complete the following Registration Submission Checklist and attach the requested documents: - Cable route diagram or a simple block drawing of the project showing the installed Corning Cable Systems Contract Products - Bill of materials or invoice copy showing Corning Cable Systems’ part numbers , quantity and descriptions of the products that were used for this installation - OTDR Test results - End-to-End-Attenuation Test Results * Required for EWP project registration

Cleaning – Connectors, Fibre Majority of problems in fibre systems are due to dirty components. “Dirt” can mean debris <5μm Only use Isopropyl Alcohol (> 95%) or approved agent for cleaning Canned air / Druckluftdose Lint free wipes The cleaning cassette is rated for 500 cleanings. This is a patented device. The other devices that look similar (the green Cle-Top) do not have a place for pinned connectors to slide into.

Cleaning - Connector Cassette for single fibre, MT-RJ and MTP • It is difficult to clean between the pins of a connector with only a dry wipe and alcohol. Cleaning cassettes are the preferred option for pinned and multi-fibre connectors. 1) Open door and rotate wheel 2) Slide connector endface across appropriate section

Cleaning - Adapter Tools • Adapters and connectors behind the adapters can also attract dust • It is preferable to clean from the front of the panel rather than disturb connectors inside the hardware MTP Adapter Cleaning Tool 1.25 mm Cleaning Stick (10pcs) 2104023-10 2.5 mm Cleaning Stick (10pcs) 2104065-10 Swab with Foam Head (10pcs) 2104067-10 MTP Adapter Cleaning Tool 2104466-01 Cleaning Cassette 2104359-01 ( for MTP,MTRJ, 1.25 or 2.5mm ferrules)

Troubleshooting - Visual Fault Locator Fits all 2.5 mm connector ferrules Red light - visual check or continuity 635 nm Wavelength Visible beyond 3 km Checks for bends and breaks Compatible with UniCam® connector Continuity Test Set (CTS) Visual Fault Locator (VFL) is very useful for identifying tight bends or crimps, faulty connectors, damaged components, bad splices and fibre breaks. It shoots out a red visible laser light, which is visible beyond 3 km. The picture shows a VFL-350. The VFL is included in the rental test sets. VFL-350 • Compact pin design • Output power less than 1 mW • Laser class 2 inch accordance with IEC825-2 Glowing red light is emitted from fibre break or severe bend

Troubleshooting Bends: Mode Field Diameter (MFD) The diameter of the optical energy in a SM fibre (SMF28e) 1310nm 1550nm MFD = 10.5um MFD = 9.3um Themode field diameter refers to the region (usually larger than the core) in which the light travels in a fibre.The MFD is larger at 1550 than at 1310nm. Therefrore...

Troubleshooting Bends - Effect of Wavelength in Bends For The Same Bend More Light Is Lost At 1550nm Test Suspicious Splices/Connectors At Both Wavelengths …. the same bend is more noticeable at 1550 than at 1310. As the light passes through the core it encounters the bend which forces the light into a path exceeding the critical angle (with respect the cladding/core interface) required to maintain the light path inside the core. For the same bend, then, light traveling in the wider MFD at 1550 exceeds the critical angle quicker than it does in the narrow MFD at 1310. If you read a high splice with an OTDR, shoot it at the other wavelength. If the 1550 reading is significantly higher (nearly 2X) than that at 1310, then you probably have a bend in the fibre. Remove the bend and the splice loss will come down to a more acceptable level. Side Note: Realize a slightly higher loss (+0.01 to 0.03dB) may be observed for the 1310 reading above the 1550 reading. This is due to a slight lateral offset of the MFDs after fusion. 1310nm 1550nm 1550nm

Effect of Wavelength on Lateral Offset Splice/Connector Lateral offsets will show different losses at different wavelengths. Short wavelength/Small MFD shows a HIGHER loss. Long wavelength/Large MFD shows a LOWER loss. Directionally independent. Larger overlapping area at longer wavelength = lower loss Cross Section View Side View

Summary Testing provides proof that the system meets the design specifications Type of reference test set-up depends on the system No. Jumper Reference = 3 – No. of Patch Panels in the System Mandrel Wrapping Over short distances light travels in the cladding of the multimode fibre, leading to erratic test results Mandrel wrapping helps in eliminating such errors OTDR measures splice loss, end-to-end loss of the fibre Testing Documentation Troubleshooting Cleaning, Cleaning and Cleaning!!!