Network IQ Training Manual Chapter 6 - Fibre Testing and Measurement

Network IQ Training ManualChapter 6 - Fibre Testing and Measurement

Optical Fibre Network IQ Training Manual 2

• 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

Fibre Testing and Measurement


Reasons for Testing

• Product Acceptance

• Installation Acceptance

• Accounting System

- Original

- Repairs

- Changes/Upgrades

- Future Reference

• Proof of Final System Specifications


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


Attenuation Testing

Source (transmitter)… • Simulates system source

(LED, LASER, or VCSEL)

• Creates a standard reference for continuity

• Provides stable reference for fibre and component lossMeter (receiver)... • Checks continuity

• Measures total fibre loss (end to end) • Optimizes splice loss

• Identifies active fibre


Attenuation Testing

• Checking with an Attenuation Test set will ensure correct polarity

• fibres can be accidentally placed in wrong ports.


Power Meter/Attenuation Testing

• How much water leaks from the joint/connection?– What do you need to know first?

5 Ltr/min



• Make a reference to know the strength of the source.– Same as 1 Jumper reference for fibre optic testing

7 Ltr/min



• Subtract source power from received power to determine power loss.

– Measured in dB (deciBel)

5 Ltr/min

7 Ltr/min

7-5 = Loss (Attenuation) 2 ltr/min


Attenuation Test Procedures - One Jumper Reference

Step 1

Step 2

Step 3

Power Ok? Press Reference (#1)

Add Jumper 2,Check loss < 0.1 dB

Test System


Attenuation Test Procedures

Three Types of

Reference Set Ups:

IEC 61280-4-1, Method 2; ANSI/TIA/EIA-526-14A, Method B

IEC 61280-4-1, Method 1 ANSI/TIA/EIA-526-14A, Method A

IEC 61280-4-1, Method 3


Summary of Attenuation Testing

Rule of Thumb: Nr. Jumper Reference = 3 – Nr. Patch panels in SystemMore 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).


Mandrel Diameters for Multimode fibre Testing

62.5 µm50 µm

TIA-455-50-B ; IEC 61280-4-1; IEC 61300-3-4 ed 2. 2000

Mandrel diameters in millimeters for 900um fibre. If jacketed cable, subtract cable OD from mandrel diameter

Fibre Core Mandrel diameter50µm 25 mm (22 for 3mm cable)62.5µm 20 mm (17 for 3mm cable)


Link Loss Measurement: Calibration and Test (MM) ReviewOne 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.

-8dBm

Tx REF

0dB

Tx

0.1dB

850 on

850 on

(1)

(1) (2)


The OTDR Allows You to ….

• 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 fibrefrom

one end


Coupler/Splitter

Tested fibre

CONTROLLER CRT or LCDDISPLAY

LASER(S)

DETECTOR

The OTDR-Principle

OTDR uses RADAR principle


OTDR - Standard Trace

LaunchCable

SystemCable

Connector -Patch Panel 1

Connector -Patch Panel 2

OTDR

Time / Distance

Power


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 eventfront connector

reflective eventconnector/

mechanical splice

non-reflective eventfusion splice

non-reflective eventmacro bending

reflective/ non-reflectiveeventfibre end/ break

atte

nu

atio

n (

dB

)

Length of fibre (km)

Length attenuation dB/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 LossIndividual Connector Loss ______ (dB) (EN50173-1 Max: 0.75dB/pr.)

Number of Connector Pairs x ______

Total Connector Loss ______ (dB)


Link Loss Budget CalculationStep 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 Lossfibre 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.


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.

* 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


Cleaning - Connector Cassette for single fibre, MT-RJ and MTP

1) Open door and rotate wheel

2) Slide connector endface across appropriate section


Cleaning - Adapter Tools

1.25 mm Cleaning Stick (10pcs) 2104023-102.5 mm Cleaning Stick (10pcs) 2104065-10Swab with Foam Head (10pcs) 2104067-10MTP Adapter Cleaning Tool 2104466-01Cleaning Cassette 2104359-01 ( for MTP,MTRJ, 1.25 or 2.5mm ferrules)

• 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


Troubleshooting - Visual Fault Locator

Glowing red light is emitted from fibre break or severe bend

• 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)


Troubleshooting Bends: Mode Field Diameter (MFD)The diameter of the optical energy in a SM fibre (SMF28e)

1310nm

MFD = 9.3um

1550nm

MFD = 10.5um


Troubleshooting Bends - Effect of Wavelength in Bends

1550nm

• For The Same Bend More Light Is Lost At 1550nm• Test Suspicious Splices/Connectors At Both Wavelengths

1310nm 1550nm


Effect of Wavelength on Lateral Offset Splice/Connector

Side View

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


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!!!

Documents

Network IQ Training Manual Chapter 6 - Fibre Testing and Measurement