fiber optic training presentation

Fiber Optic Inspection, Cleaning, and Test Methods

Optical Design Manufacturing, Inc.

Agenda

Section 1: Fiber Optic Theory Fiber Construction Multimode and Single Mode Fiber Connectors

Section 2: Inspection and Cleaning According to IEC Standards Inspection Scopes IEC Specification Industry-Accepted Cleaning Methods Using an Inspection Scope

Section 3: Testing Equipment and Methods Review of Fiber Testing Equipment Optical Power and Loss Measurements OTDR Description and Theory Cell Tower Configurations

Section 1: Fiber Optic Theory

Behavior of Light in Material

Cable Construction

Single Mode Fiber

Multimode Fiber

Ferrule and Connector Styles

Section 1.1 Behavior of Light in Material

Wavelength: Color or frequency of the electromagnetic wave (in nanometers)

The Spectrum of Visible and Fiber Optic Wavelengths

Behavior of Light in Material

Index of Refraction (IOR) defines how light travels through a material

IOR compares speed of light in a vacuum to speed of light through another medium

The angle the light will refract (bend) when it hits a new medium is determined using its IOR


Each wavelength refracts at a different angle at the interface between two materials, as seen when white light refracts through a prism

In fiber optics, if the wavelength and IOR of materials are known, light can be made to travel along a set path


Core Material: 9m Single Mode (1/10 the diameter of

human hair) 50 or 62.5m Multimode

Cladding Material: 125m diameter (Single and Multi)

Section 1.2 Cable Construction

Cable Construction

The difference in the index of refraction between the core and cladding materials allows total internal reflection of light.

Section 1.2 Cable Construction

Small aperture: 9m core diameter

Provides higher data rates/bandwidth

Typical wavelengths: 1310 and 1550 nm

Loss per Km (SMF28e):

.35dB @ 1310nm

.20dB @ 1550 nm

Ideal for Backhaul applications due to low modal dispersion and low loss

Requires laser sources and more critical alignment techniques

Used in 90% of cellular installations

Section 1.3 Single Mode Fiber

Single Mode Fiber

Single mode path all photons reach receiver at expected time received signal is virtually identical to input signal

Nearly unlimited bandwidth can be improved further with Wavelength Division Multiplexing Current Technology: 200 gigabit, 80 channels, 1 fiber


Connector color typically dark blue

Cable jacketing color typically yellow for reference cables or patch panel jumpers


Multimode Fiber

Usually used for short distance links such as in buildings and on campuses

Larger aperture for light gathering and simplifying connections 62.5 or 50 m core diameter

Uses less expensive LED and laser sources larger aperture allows for less precise alignment of source and fiber

Typical wavelengths are 850 and 1300 nm

Loss per Km

2.5dB @ 850nm

1dB @ 1300nm

Section 1.4 Multimode Fiber

Multiple paths for light because core is larger than wavelength transmitted

Photons reach receiver at different times: received signal is slightly different than input signal data rate/bandwidth impacted

Modal Dispersion Also called Pulse Spreading or Distortion


Connector color

typically beige

Used in Sprint ALU



Transmission Standards Streaming up to: Cable Jacket Color

OM1 (62.5m core) 10 Gb Ethernet (33m) Orange

OM2 (50m core) 10 Gb Ethernet (82m) Orange

OM3 (50m core) 100 Gb Ethernet (100m) Aqua

OM4 (50m core) 100 Gb Ethernet (150m) Aqua

Multimode Fiber Types

Connectors provide the mechanical fastening of cable ends. Many styles are available; the most common include:

LC 1.25 mm SC 2.5mm ODC 1.25mm

ST 2.5mm FC 2.5mm

Section 1.5 Ferrules and Connector Styles

Connector Styles

Ferrules provide the contact interface at cable ends Polish Connectors (PC) and Ultra Polish Connectors

(UPC) provide a domed profile that helps reduce back reflection

Angled Polish Connectors (APC) provide the domed

profile with an 8 degree angle lowest back reflection available. APC connectors are always green.

Section 1.5 Ferrules and Connector Styles

UPC

APC

Reflected Ray

Section 2: Fiber End Face Inspection, Grading, and Cleaning

Inspection Microscopes

Video Inspection Scopes

Direct View Scopes

IEC 61300-3-35 Criteria

Connector Cleaning Methods

Inspection Procedures

Video Inspection Scopes (USB)

Provide microscopic view of fiber endfaces some models allow technicians to save images to be reported

Inspecting is the ONLY way to know for sure that fiber endfaces are clean Always inspect fibers before making any connection

Section 2.1 Video Inspection Microscopes

Direct View Scopes Avoid Eye Damage on Live Fibers

When viewing an endface close-up, any dirt, debris, or defect will stand out

If this debris blocks light coming from core/cladding area, fiber will not function efficiently

If debris is trapped between mated ferrules, they can be permanently damaged and need to be replaced

Section 2.1 Video Inspection Microscopes

Debris

Core

IEC 61300-3-35

The IEC 61300-3-35 Ed. 1 document is an industry standard for connector endface cleanliness requirements.

AT&T refer to ATT-TP-76461 for inspection and cleaning guidelines

Area of interest relative to the ferrule end face

Section 2.2 IEC 61300-3-35 Criteria

Criteria Table

There are four zones on the fiber endface as outlined in the IEC document. Each zone has been assigned a limit to the amount of debris and/or scratches it may contain. Whether the fiber is single Mode or Multi Mode, PC, UPC, or APC will affect zone size and criteria.

Adhesive Zone

Section 2.2 IEC 61300-3-35 Criteria

Connector Cleaning Methods

Recommended:

3 dry clean

2 wet/dry clean

Section 2.3 Connector Cleaning Methods

Dry clean method: one-click

Dry clean method: cletop

Wet/Dry clean method: SQR pad and pen

Section 2.3 Connector Cleaning Methods

There are three distinct inspection methods allowed by IEC 61300-3-35

1. Manual inspection with a grading overlay

Portable Monitor: No Onboard Storage or Auto Pass/Fail

2. Manual inspection with software

Windows laptop required

3. Automated pass/fail with software

Windows laptop or tablet, Android smartphone or tablet

Inspection Procedures

Section 2.4 Inspection Procedures

1. Manual inspection with a grading overlay

An inspection scope and viewing device

are used with a physical overlay template to show the IEC zones and compare defects.

Generally, images are not saved

Pass/Fail is based on user input and knowledge of IEC standard


2. Manual inspection with software

Software offers grading circles and sample

defects for comparison to IEC standard

Images can be saved using software

Pass/Fail is based on user input and knowledge of IEC standard



3. Automated Pass/Fail with software

Software utilizes an algorithm to identify

IEC zones (according to user settings)

Compares any detected defects to the IEC standard and determines if endface passes or fails

Images can be saved using software

Automated Analysis: Laptop or Tablet



Automated Analysis: Smartphone or Tablet

Wi-Fi Access Device

Section 3: Test Equipment and Methods

Test Equipment Summary

Power Meters

Optical Power and dB Loss Measurement

Light Sources

Referencing Procedures

Troubleshooting Devices

Optical Time Domain Reflectometers

Current Test Procedures

Test Equipment Summary

Optical Power Meter

Measures absolute power, dBm

Measures insertion loss with light source, dB

Light Source

Laser Single Mode Testing

LED Multimode Testing

Visual Fault Locator

Red laser fiber break detector

Live Fiber Identifier

Live traffic/active channel detector

Optical Time Domain Reflectometer

Fault and end-distance location device

Section 3.1 Test Equipment Summary

Optical Power Meters

Measures absolute power and insertion loss on fiber optic cables

Absolute power measured in dBm Insertion loss Measured in dB must first reference the equipment using an

absolute power measurement

Many offer multiple wavelength testing options

Some have onboard save options and USB connectivity

Section 3.2 Power Meters

Ex. RP460 Ex. UPM100

Optical Power (dBm)

milliWatt = .001 Watts

microWatt = .000001 Watts

The absolute power level of light is measured in dBm

The m in dBm designates the value in reference to 1 milliWatt

Section 3.3 Optical Power and dB Loss Measurement

dBm milliWatt power ratio

3 1.995(~2) 1 1.259 0 1 -1 0.794 -3 0.501 (~ )

Optical Power Meters Cont.



dB (Decibel) scale

The dB is a logarithmic unit used to express the ratio between two values of a physical quantity. In this case the ratio between a reference power and a second measured power.

dB conveniently represents very large or very small numbers.

dB Loss

dB loss represents the difference between a reference value and a measured value

It does not indicate the absolute power of a signal

Because this is a loss value it is considered by convention to be non-negative

Ex. A -3dB loss would mean the light level is twice the referenced value (a gain). A 3dB loss means the light level is half the referenced value (a loss).


dB Loss milliWatt power ratio

-3 1.995(~2) -1 1.259 0 1 1 0.794 3 0.501 (~ )


Optical Light Sources

Section 3.4 Light Sources

Two Types: 1. Single Mode Sources

Ex. DLS 355 Usually lasers, most common wavelengths are 1310 and 1550nm

1. Multimode Sources

Ex. DLS 350 Usually LED, most common wavelength 850nm

Section 3.4 Light Sources

Optical light sources shoot light of a specific wavelength down fiber runs.

Used to set a reference on power meter and to test loss along jumpers and trunk cables

Some models offer troubleshooting functions, such as a 2khz tone for fiber identification

User must know output power of light source to use effectively

When combined, the light source and power meter provide the most accurate and industry-accepted standard for insertion loss testing.

Optical Light Sources Cont.

Insertion dB Loss Calibration Procedures (Referencing)

Loopback

Sprint Ericsson

AT&T

Verizon

T-Mobile Ericsson

Sprint Alcatel-Lucent

Point-to-point

Sprint Samsung

Clearwire Samsung

Section 3.5 Referencing Procedures

Light Source

Power Meter Light Source & Power Meter

Point-to-Point Loopback

Loopback

1 Connect the Power Meter, Light Source, LC Duplexed to LC SC yellow single mode paired cable and the loopback module as shown above. Power on both the Power Meter and Light Source. Set both units to desired wavelength. Set the Power Meter to dBm mode.

2 Make sure the Power Meter is reading within the appropriate power level for the light source. If the reading is not within this range, inspect and clean all optical fiber connector endfaces.

3 Hold the appropriate button(s) on the power meter to set the reference on the device. Your power meter should read 0.00dB.


Point-to-Point (P2P; Single Fiber Runs)


1 Connect the Power Meter, Light Source, and LC to SC yellow single mode cable as shown above. Power on both the Power Meter and Light Source. Set both units to desired wavelength. Set the Power Meter to dBm mode.

2 Make sure the Power Meter is reading within the appropriate power level for the light source. If the reading is not within this range, inspect and clean all optical fiber connector endfaces.

3 Hold the appropriate button(s) on the power meter to set the reference on the device. Your power meter should read 0.00dB.

dB Loss Closeout Reporting

Once all loss readings for cellular build have been saved to power meter, plug the device into computer and open report software

Set color code and loss budget to match your build

Dump data from power meter to upload readings to software. Export the readings to Excel to complete the report

Use comment section on Excel sheet to make notes such as Disregard reading

Visual Fault Locator red laser source used for fiber tracing and break detection (if jacket allows). Ex: VF610

Live Fiber Identifier Uses the bend loss effect to create a macro bend and measures power leaked from the fiber Most provide power and tone detection on 2mm or less jacketed fibers

Toning the fiber May be either a standalone unit or a power meter attachment

Section 3.6 Troubleshooting Devices

Troubleshooting Devices

OTDR Optical Time Domain Reflectometer

An OTDR device provides a graphical representation of phenomena that occur between the pulse of light, fiber, splices and connections in the time domain.

Similar to RADAR

The graphical representation known as a Trace provides a picture of an optical link which may include multiple connectors and splices.

OTDRs are most beneficial to long optical links such as backhaul applications up to 200km.

They provide a distance to event (such as a break) that allows maintenance crews to locate and repair the break, minimizing downtime.

OTDRs have limited capabilities on short links with multiple connections due to event and attenuation dead zone limits.

OTDR technicians need to be specially trained to perform tests effectively.

Section 3.7 Optical Time Domain Reflectometers

Ex. OTR 700

OTDR


Trace

A very simple trace example is shown above. Notice the reflective event at the front panel (green arrow) and the reflective event at the end of the link (blue arrow). If the user knows the link should be longer than 17km, the event at the blue arrow can be identified as a break.

1. Reflective event

Reflective events are typically a physical connection or break. The amplitude of the reflective event is measured in dB.

2. Backscatter Backscatter is the slanting horizontal line that represents the Rayleigh reflections inherent in every fiber. These reflections are due to the impurities and physical makeup of the fiber. Backscatter measurements are measured in dB per Kilometer.

3. Non reflective events Non reflective events such as splices and bend loss are displayed as a decrease in backscatter at a single point. This loss is measured in dB.


OTDRs provide loss analysis of individual reflective and non reflective events by measuring the level of backscatter before and after the event and subtracting them from each other. The result is the loss in dB.


Reflective Non-Reflective


OTDRs provide Optical Return Loss (ORL), which represents all of the light reflected back at the source from the entire system.

Light sources cannot function correctly when too much light is reflected back at them. OTDR recognizes when ORL is too high.

ORL is reported in dB. A higher negative number is better. Ex: -50db better than -30db

ORL is predominantly affected by connector profile rather than debris contamination

UPC Typically -40 to -50dB

APC Typically -50 to -60dB

Pulse width and Range

Pulse width is the amount of time the OTDR laser is ON.

Measurements of long distance links (high range) require a larger pulse width to provide the backscatter and reflective events to be measured by the receiver circuit.

Measurements of short range links require short pulse widths which allow shorter

dead zones. OTDRs can still fail even with the shortest pulse width and dead zones available.


Reflective Event Dead Zone is an OTDR specification that represents the minimum length of fiber that must exist between two events.

The average Event Dead Zone is 1 meter.

Connections closer than the specified dead zone will not be detectable or visible.

Attenuation Dead Zone is the distance from the beginning of the event to the events falling edge settling to the backscatter level.

The average Attenuation Dead Zone is 4 meters

Connections closer than the specified dead zone will not give reliable data for measuring connector loss.

Dead Zones Section 3.7 Optical Time Domain Reflectometers

Above: 2 connectors (in blue) are .5m apart in an optical link. If the average event dead zone is 1m, the OTDR will show only one spike in reflectance, which represents both connectors. This can cause issues if the existence of the second connector is not known.

Above: 2 connectors (in blue) are 1.5m apart in an optical link. If the average event dead zone is 1m, the OTDR will display the reflectance of both connectors, but they will appear as if they are merged together.

Dead Zones Cont. Section 3.7 Optical Time Domain Reflectometers

Event Dead Zones

Above: 2 connectors (in blue) are 3m apart in an optical link. If the average attenuation dead zone is 4m, the OTDR will display the reflectance of both connectors, but will not settle to an appropriate backscatter level. OTDR software will only be able to guess the loss of each connector.

Dead Zones Cont. Section 3.7 Optical Time Domain Reflectometers

Attenuation Dead Zones

OTDRs at Short Distances


Even on short distance links and with the shortest possible pulse width, events that are too close together will require guesswork.

Notice in the image at left that the trace does not settle back to backscatter before showing the next reflective event. Without a backscatter level, accurate loss readings are not possible. The attenuation dead zone is too large in this case.

Current Cellular Fiber Optic Installation Architectures

Sprint (2.5 Project Under Way) Samsung

Ericsson

Alcatel-Lucent (ALU

T-Mobile

Clearwire Samsung

AT&T

Verizon

Section 3.7 Current Test Procedures

Sprint Samsung Single Mode Fiber 1550nm Point to Point Test Loss Budget: 3dB System Inspection is required, saving images is not. Record results for pre and post dB loss test

Sprint Ericsson Single Mode 1310nm Loopback Test Loss Budget: 2.6dB (sector) 3dB (system) Inspection is required, saving images is not required 6 Loss readings (Each trunk pair)

Sprint Alcatel-Lucent Multi Mode 850nm Loopback Test Loss Budget: 3dB System Save/report all 30 fibers in Hybriflex cable


T-Mobile Single Mode 1310nm Loopback Test Loss Budget: 2.6dB (sector) 3dB (system) Images of all ends of sector cable must be saved Loss Reading for each trunk pair Save pre-test dB loss of sector cable


AT&T Single Mode Fiber 1310nm Loopback Test Loss Budget: 3dB Save Images of 12 or 18 Trunk Pairs Loss readings must be saved to images in VIS Report : -12 trunk loss and 3 sector loss for 15 readings -or 18 trunk loss and 3 sector loss for 21 readings

Clearwire Samsung Single Mode 1310nm Point to Point Test Loss Budget: 1.5dB Inspection is required; saving images is not required Loss test results must be reported for each fiber in all sector cables

Verizon Single mode 1550/1310nm Loopback Test Loss Budget: 1dB for individual trunk/sectors, 6dB System 18 loss readings pre-test, 3 system loss readings on site (BBU to RRU) Save images before installation: 12 trunk and 6 sector pairs (both sides) for 72 total images

Sprint Samsung

Single Run from Base to RRU 4x5 Bundles per Sector 20 Fibers per Sector

Single Mode 1550


Sprint Ericsson Single Mode 1310

ODC Connectors at Top of Trunk and Bottom of Sector 12 Fibers in Trunk (Paired) Paired Fiber Runs from Base to RRU


Sprint Alcatel-Lucent (ALU) Multi Mode 850

1 Pair from Distribution Box to Each Sector All Connections LC Duplexed 30 Trunk Fibers Total (5 Pairs Per Sector) Single Run from Base to RRU


T-Mobile Modernization Single Mode 1310

ODC Connectors at Top of Trunk and Bottom of Sector 12 Fibers in Trunk (Paired) Paired Fiber Runs from Base to RRU


Clearwire Samsung Single Mode 1310

All Connections LC 24 Trunk Fibers (8 per Sector) Single Run from Base to RRU


AT&T LTE Single Mode 1310

1 Pair from Distribution Box to Each RRU All Connections LC Duplexed 12 or 18 Trunk Fiber Pairs (24 or 36 Total) Paired Run from Base to RRU


Verizon Single Mode 1310

Sector Jumper at Tower Top (3 Pairs) All Connections LC Duplexed 12 Trunk Pairs Sector Jumper at Tower Bottom (3 Pairs) Paired Run from Base to RRU


Verizon Cont.

Pre-test will include saved scoped images (using inspection scope) of ALL ends of ALL fibers in trunk and sector jumper pairs.

Pre-test will include loopback dB loss readings of all trunk and sector pairs

in the following order:

All Trunk Cables (1-12)

All Sector Jumpers to RRU (1-3)

All Sector Jumpers from BBU (1-3)


On-Site testing procedure requires inspection and cleaning of all fiber ends and three loopback dB loss readings representing the entire system (BBU to RRU)

If dB loss reading of any individual jumper or system configuration exceeds parameters in the table at right, an OTDR may be required to perform Optical Return Loss readings.

Pre-Test

Post-Test


Verizon Cont.

OTDR compares averages of backscatter before and after reflective event to give loss at each connector (2-point connector loss)

Total system link loss (2-point method) takes the backscatter level at beginning and end of link to give total loss.


Verizon Cont.

Optical Return Loss Overall light reflected back at source caused by differences in the refractive index

of different media Ex: Light traveling from glass to air OTDR reads light reflected back in dB

Complete ORL reading of system must be 37 dB

OTDR

Continuous Wave

Transmitted Power

Connector

Reflected Power


Verizon Cont.


Verizon Cont. Trace Report


Verizon Cont.

Trace Report

Technical Support

Optical Design Manufacturing, Inc. Phone: 603-524-8350

Email: [email protected] Visit ODMs YouTube Page

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