Fiber Optic Cable Assemblies Fiber Basics and...

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Transcript of Fiber Optic Cable Assemblies Fiber Basics and...

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Fiber Optic Cable Assemblies

Fiber Basics

and Theory

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Fiber Optic Basics & Terminology

What is a fiber?• A fiber is an optical

waveguide ; a medium for

transferring information in

the form of light across

glass

A fiber is to light what

a hose is to water!!!

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Fiber Optic Benefits:

• Low attenuation (significant savings

on repeaters)

• Small size and weight

• Large bandwidth

• Longer lengths (in excess of 20km)

• Easy to install/maintain

• Enhanced security

• Non-conductive

• All-dielectric designs available

• No EMI/cross talk concerns

•Designed for future high-bandwidth

applications

Optical Parameters - Benefits

Fiber Optic Basics & Terminology

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Optical Parameters - History

• 1880: Alexander Graham Bell invented the Photophone

• 1954: Abraham van Heel demonstrated core-clad technology

• 1958: LASER invented

• 1970: Corning developed the first low loss fiber (<20 dB/km)

• Late 1970s: The first commercial fiber optic systems were deployed

• 1984: First single mode system

• 1987: First dispersion shifted fiber

• 1998: First non-zero dispersion shifted fiber (LEAF fiber)

• 2000: Emergence of Gigabit Ethernet Multimode Fiber

• 2005: Reduced bend radius fiber solutions

• 2010: High bandwidth multimode fiber solutions

Fiber Optic Basics & Terminology

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Optical Parameters -Transmission Sequence

•Information is encoded as electrical signal and converted to optical signal.

•Can be analog or digital.

•Light is transmitted down the fiber.

•Detector receives signal and decoder converts the signal to electrical.

Fiber Optic Basics & Terminology

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Fiber OpticBasics & Terminology

Types of Fiber

Optical Single-mode (OS2)

Core/cladding diameter: 9/125um

Single path/mode through fiber eliminates distortion from overlapping light pulses

Can go a longer distance than multi-mode fiber, but requires a light source with a narrow spectral width, which makes the equipment quite costly

Optical Multi-mode (OM1, OM2, OM3, OM4)

• Core/cladding diameter: 62.5/125um, 50/125um

• Light waves dispersed through numerous paths/modes through fiber

• Able to carry more data than single-mode fiber, but is best for shorter distances because of higher attenuation values and optical dispersion

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Fiber OpticBasics & Terminology

Physical Characteristics of Fiber

Cladding Core

Multimode 140m 100m

Step Index

125m 50m

Multimode 125m 62.5m

Graded Index 140m 100m

Single Mode 125m 8.5m

Step Index 125m 9m

Dispersion

High-Order Mode

Low-Order Mode

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Fiber Type

Core Cladding (µm) Standard

Jacket Color

minEMB (MHz·km) 1G 10G 40G 100G Cost

OM1 62.5/125TIA-492AAAA

IEC 60793-2-10 Orange 200 275 33 $

OM2 50/125TIA-492AAAB

IEC 60793-2-10 Orange 500 550 82 $

OM3Laser optimized

50/125TIA-492AAAC

IEC 60793-2-10 Aqua 2000 800 300 100 100 $$$

OM4Laser optimized

50/125TIA-492AAAD

IEC 60793-2-10Currently

Aqua 4700 1000 550 125 125 $$$$

• ~85% of data center links are 100m or less

Typical Max Reach (m) for 850nm Ethernet

Key factors for choosing a fiber type Current and future data rates, bandwidth needs, reach, cost

Fiber OpticOptical Multi-mode (OM) Fiber

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OM3 and OM4 fiber types are recommended for data centers

Optimized for laser-based 850nm operation with a much higher minimum effective modal bandwidth (EMB) and longer distance capability

Dominant in data centers due to emergence of high data rate stems, such as 10, 40, 100Gigabit Ethernet and 8 and 16 Gigabit Fibre Channel

Cable, connectors, hardware, and electronics are now readily available to support usage of this fiber

Industry has recognized the benefits of this fiber

IEEE 40/100G

Fibre Channel 4/8/16G transmission standards

TIA-568-G3 structured cabling and connectivity standards

Most economical solution due to electronic costs

Data rate scalability ensures support for both legacy and future application needs

Fiber OpticOptical Multi-mode (OM) Fiber

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Multi-mode (M/M) • RL ≤ -45dB

• Usually hole diameter of ≥127um depending on the connector

• Connector color code is typically: Beige or Black

• SMA hole diameter goes to 1500um

Single mode (S/M) • UPC ultra polish

• RL ≤ -55dB

• Usually 125um, 125.5um, or 126um

• Color code typically: Blue

Single mode Angled• APC angled polish

• RL ≤ -65dB

• Color code typically: Green

UPC

Fiber OpticBasics & Terminology

Typical Polish Types

Keeping the endface

clean is critical

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Fiber OpticCable Types

Examples of Loose Tube Buffer and Tight Buffer Constructions

Loose Tube Buffer

Coated Optical Fiber

Tight Buffer

Buffer Layers Applied Directly

Over Fiber Coating

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Zipcord Distribution Loose Tube Breakout

Simplex- Available in 900µm, 1.6mm, 2mm, 2.9mm

Zipcord- Available in 1.6mm, 2mm, 2.9mm

Ribbon Cable- Available in fiber counts of 4, 8, 12, 24

Distribution- Tight buffered 900µm. Available in a variety of fiber counts.

Breakout-Tight buffered fibers enclosed in subunits throughout the cable.

Available in a variety of fiber counts. Subunit sizes range from 1.6mm to

2.9mm.

Outside plant (OSP)- 250µm loose tube construction. Available in a

variety of fiber counts, armored or non-armored.

Fiber OpticCable Types

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Fiber OpticBasics & Terminology

Attenuation

• Measure the decrease in transmitted optical power and is expressed in decibels per kilometer (dB/Km)

Casual Factors:

– Absorption

– Impurities

– Scattering

– Variances in the structure of the fiber

– Micro/Macro Bending

Insertion loss

• The attenuation caused by the insertion of an optical component (i.e. a connector or coupler in an optical transmission system)

Return loss

• Ratio of incidental optical power to the reflected optical power.

The scattering of light in the direction opposite to its original

propagation

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Attenuation is the loss of optical power, measured in

decibels (dB).

ATTENUATION (dB) = -10 log (Powerout/Powerin )

Power is measured in watts (mW or µW).

The negative sign gives attenuation a positive value,

since input power is always greater than output power

for passive optical devices.

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Fiber Optic Basics & Terminology

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Optical Parameters - Attenuation

Absorption: light is absorbed by impurities in the

glass

• Accounts for about 5% of intrinsic attenuation

• Light is absorbed by impurities introduced during

the manufacturing process

Absorption

Fiber Optic Basics & Terminology

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Optical Parameters - Attenuation

Scattering: Technically referred to as Rayleigh

scattering, it accounts for about 95% of intrinsic

attenuation

Fiber Optic Basics & Terminology

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Macro-bendingOptical fiber bends that are much larger and visible.

Typically caused by bending the cable beyond the

specified bend radius. Attenuation is increased by

light escaping through these bends.

Fiber Optic Basics & Terminology

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Micro-bendingSharp microscopic curvatures in optical fiber on the

order of a few micrometers.Typically caused by shrinking of the buffer or poor

cable manufacturing methods.

Fiber Optic Basics & Terminology

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Index of refraction: (‘IOR’ or ‘n’) is a way of

measuring the speed of light in a material:

IOR: Speed of light in a vacuum

Speed of light in the material

Medium IOR or n Speed

Vacuum 1.0000 Faster

Air 1.0003

Water 1.33

Cladding 1.46

Core 1.48 Slower

Optical Parameters - Index of Refraction

Fiber Optic Basics & Terminology

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Optical Parameters - Refraction and Total Internal Reflection

Fiber Optic Basics & Terminology

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Optical Parameters - The Critical Angle

Fiber Optic Basics & Terminology

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455 nm Violet

650 nm Green

750 nm Red

850 nm Short Wavelength lasers/LEDs

1310 nm Long Wavelength Lasers/LEDs

1550 nm Long Wavelength Lasers

Fiber

Optic

Applications

Visible

Spectrum

Higher Frequency

Optical Parameters - The Optical Spectrum

Fiber Optic Basics & Terminology

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Optical Parameters - Operating windows

Fiber Optic Basics & Terminology

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Optical Parameters - Numerical Aperture

In practical terms, the numerical aperture describes the ability of a

fiber to collect light. A larger NA fiber has a larger acceptance

angle which in turn equates to its ability to gather more light.

SIN θ = NA = (n12 –n0

2)½

Fiber Optic Basics & Terminology

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Distance

Optical Parameters - Signal Distortion

Ideal RealisticBad

Fiber Optic Basics & Terminology

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Optical Parameters - Dispersion

Standard single mode fiber dispersion curve

Fiber Optic Basics & Terminology

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Optical Parameters - Bandwidth

Bandwidth:

The information carrying capacity of fiber•MHz are units for analog transmission•Mb/ps are units for digital transmission

•Specifications are displayed in MHz-km; normalized, not linear

•Bandwidth is directly related to dispersion in multimode fiber•High dispersion causes pulses to overlap, limiting transmission rate•Single mode fiber specifies mode field diameter instead

Fiber Optic Basics & Terminology

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Optical Specifications

Notes:

1. Specified attenuation is the maximum for all of the fibers in the cable over the

operating temperature range.

Fiber Optic Basics & Terminology

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Fiber Manufacturing

3 Steps in Fiber Manufacturing

•Laydown (Deposition)

•Consolidation

•Draw

Fiber Optic Basics & Terminology

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Fiber Manufacturing - Deposition

Outside Vapor Deposition Process (OVD)

Fiber Optic Basics & Terminology

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Fiber Manufacturing - Drawing

The speed of the draw determines the

diameter of the glass fiber

Fiber Optic Basics & Terminology

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The National Electric Code - Definitions

• The NEC is advisory in nature

• It must be (and has been) adopted by each state

• Each state adds its own articles to the code

• Always check with LAHJ

• PLENUM (P) — environmental air space (hung ceilings, raised floors, fan

rooms, ducts)

• RISER (R) — openings through which cable goes vertically from floor to

floor

• GENERAL (G) — all other areas

•Note: Non-rated cables must be terminated within 50 feet of entering a

building.

Fiber Optic Basics & Terminology

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Cable Markings: In accordance with NEC Article 770

• OFC Optical Fiber Conductive

• OFN Optical Fiber Non-conductive

• OFCG Optical Fiber Conductive General Purpose

• OFCP Optical Fiber Conductive Plenum

• OFNG Optical Fiber Non-conductive General Purpose

• OFNP Optical Fiber Non-conductive Plenum

• OFCR Optical Fiber Conductive Riser

• OFNR Optical Fiber Non-conductive Riser

• OFN-LS Optical Fiber Non-conductive Low-Smoke

Cable Fire Listings and the NEC

Fiber Optic Basics & Terminology

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(UL) Fire Ratings

UL 910

Test for Flame Propagation and Smoke Density Values

for Electrical and Optical-Fiber Cables Used in Spaces

Transporting Environmental Air

UL 1666

Test for Flame Propagation Height of Electrical and

Optical-Fiber Cables Installed Vertically in Shafts

UL 1581

Vertical Tray Flame Test

Plenum

Riser

General

Fiber Optic Basics & Terminology

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• Safety glasses must be worn at all times when working with bare fiber.

• Laser light can damage your eyes.

• Laser light is not visible - Viewing it directly does not cause pain; the iris of the eye will not close as when viewing a bright light. Consequently, serious damage to the retina of the eye is possible.

• NEVER LOOK INTO THE END OF A FIBER WHICH MAY HAVE A LASER COUPLED TO IT.Should eye exposure to laser light be suspected, arrange for an eye examination immediately.

• Cleaved glass fiber is very sharp and can pierce skin easily. Do not let cut pieces of fiber stick to your clothing or drop in the work area where they can cause injury later. Use tweezers to pick up cut or broken pieces of glass fiber and place them on a loop of tape kept for that purpose only, or place directly into collection bin.

• Good housekeeping is very important when working with optical fiber.

Fiber Optic Safety

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• Isopropyl alcohol is flammable, with a flash point of 12C. Dispose of

contaminated materials in flame-retardant bin only.

• Isopropyl alcohol can cause irritation to eyes on contact. In case of eye contact,

flush with water for at least 15 minutes. Inhaling fumes can induce mild narcosis. In

case of ingestion consult a physician. Use with adequate ventilation.

• Un-cured epoxy adhesives consisting of resin and hardener components may

cause skin irritation or allergic reactions. Prevent all contact with skin or eyes!

If contact occurs, flush immediately with plenty of water. Avoid heat except during

curing. Avoid prolonged inhalation and use adequate ventilation.

Fiber Optic Safety

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ATTENUATION: Where does it occur?

Attenuation occurs in the following components of a

fiber optic system:

FIBER

• along its full length (intrinsic)

• at Macrobends and Microbends (extrinsic)

SPLICES

• at fusion and mechanical splices

CONNECTORS

• at air gaps between mated connectors

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Fiber Optic Basics & Terminology

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CALCULATING A LOSS BUDGETUnderstanding Dynamic Range

Verify end equipment compatibility with system.

-Known as ‘Dynamic Range’

If optical signal is too strong , the receiver floods,

potentially causing long-term damage

If the optical signal is too weak, it cannot be detected once

it reaches the receiver

Look for labels on the back of each piece of equipment for

this information and be sure to adjust the budget accordingly

Fiber Optic Basics & Terminology

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CALCULATING A LOSS BUDGETTo calculate a loss budget for a fiber optic system:

Follow contract specifications first•Contracts often specify maximum allowable losses in the cable, splices, and

connectors. In the absence of such guidelines:

Refer to industry measurement standards (i.e. EIA/TIA 568A, which

allows less than 0.10 dB per fusion splice and less than 0.75 dB per

connector pair)

Refer to cable manufacturer specification sheets (industry standard

fiber performance for multimode is 3.5 dB/km @850nm and 1.0

dB/km @1300nm; singlemode is 0.4 dB/km @1310nm and 0.3

dB/km @1550nm)

Fiber Optic Basics & Terminology

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CALCULATING A LOSS BUDGETCompute for each operating wavelength (850, 1300 nm for multimode and 1310, 1550, 1625 nm for singlemode)

Maximumallowablesystem

attenuation

+Maximumallowable

fiber attenuation

Maximumallowable

attenuation on all splices

Maximumallowable

attenuation on connector pairs

=

+

Fiber attenuation is measured in dB/km, but cables are measured in

feet or meters. The conversion factors for these measurements are

1000 m = 1 km and 3.282 ft = 1 m.

Fiber Optic Basics & Terminology

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Fiber (f iber length) (f iber at tenuat ion) (conversion factor)

_________ ________(f t ) X _________(dB/km) X (1km/3282 f t )

+Splices (# splices) (max at ten/splice)

_________ ___________ X ______________(dB)

+Connectors (# connectors) (max at ten/conn)

_________ ___________ X ______________(dB)

=Total allowed loss budget

CALCULATING A LOSS BUDGETHelpful chart

Fiber Optic Basics & Terminology

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Attenuation Testing

The source contains either a light-emitting diode (LED) for multimode systems, or a

laser for singlemode systems. Note: Some higher-speed MM systems now operate

with laser or laser-like sources

The meter, or detector, receives an optical signal (light) at particular wavelengths

and is calibrated to measure the light at each wavelength.

Optical test sets are sold in various port configurations

System Type Source Operating

Wavelengths

Singlemode LASER

1310nm

1550nm

1625nm

Mult imode LED 850nm

1300nm

Fiber Optic Basics & Terminology

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Test Set-upAccording to EIA/TIA 526, system

testing must be done with 2 patch

cords--one between the source and

system, the other between the meter

and system.

Note: Launch and receive cables are

used to protect the test set in case of

faulty or dirty ends.

The connector at the meter end may

be faulty (and may not be detected).

The launch and receive cables are

essentially removed from the test or

zeroed out during referencing

Fiber Optic Basics & Terminology

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A one-jumper reference: The ‘Patch Panel to Patch Panel’ System

•The method of system operation is identical to the necessary test set-up (two jumpers).

Therefore, the only power needing removed is the coupled power at the source. Use one

jumper to transfer that power to the meter.

•Keep in mind that the loss in the jumper is not significant--it’s the use of the jumper to

connect and/or transfer optical power that matters.

System Test Reference

Fiber Optic Basics & Terminology

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A closer look at the 2-jumper reference

System consists of patching through a panel on one end

and directly connecting to end equipment at the other.

Receive Cable

Fiber Optic Basics & Terminology

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A closer look at the 3-jumper reference

3rd Patch Cord

System consists of directly connecting to end equipment

at both ends of the link.

Fiber Optic Basics & Terminology

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Optical Time Domain Reflectometer (OTDR)

Optical Time Domain Reflectometer

(OTDR): A measurement device that graphically

depicts attenuation over distance by injecting light at

the source and measuring the amount of

backscattered light over time.

An OTDR can also measure attenuation. It is not,

however, the standard for total system attenuation

measurements, as inherent variations in fiber

geometry can render its results imprecise.

Fiber Optic Basics & Terminology

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When is an OTDR useful?

OTDR Applications include:

Continuity testing: quickly verify that cable/system has no breaks

(sometimes called on-the-reel testing)

Troubleshooting: identify location of faults in a system

Documentation: provide the customer with proof of a quality fiber

optic installation and give them reference for future moves, adds,

changes

Connector loss measurements: measure loss across individual

connector pairs, especially at installation

Fiber Optic Basics & Terminology

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Understanding OTDR displays

Fiber Optic Basics & Terminology

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Comparing OTDRs and Optical Test Sets

Function

OTDR

Test Set

Fault Locating

Yes

No

End-to-end

attenuation test

Estimate only

Yes

Connector Pair

testing

Yes

Yes

Length

Measurement

Yes

No

Fiber Optic Basics & Terminology

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There are four types of cleaning methods used for fiber optic connectors:

• Dry cleaning: Cleaning without the use of any solvents.

• Wet cleaning: Optic cleaning with solvents. Typically IPA (isopropyl alcohol).

• Non-Abrasive cleaning: Cleaning without abrasive material touching the fiber optic connector end face. Examples are air dusters or pressured solvent jet used in automated connector cleaners.

• Abrasive cleaning: The popular lint free wipes, reel based Cletop fiber connector cleaners and optic cleaning swabs such as the Cletop sticks are all abrasive cleaning types.

Fiber Optic Cleaning

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Tools and products:

• Air dusters are used to blow loose particles from optical fiber connector end face, or dry up solvent (isopropyl alcohol) residue after a wet cleaning. All air dusters are not the same. Optic grade is more expensive. Air spray is a non-abrasive fiber optic cleaning method.

• Wet/Dry lint-free swabs – used one time only first wet, then dry to remove debris and solvents from the fiber end face.

• Semi-Abrasive Cloth cleaning tools such as the Cletops cleaner and stick style cleaners that advance a lint-free cloth to clean the end face.

Fiber Optic Cleaning

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Tools and products:

• Inspection Scopes are used to view the end face of the optical connector indirectly preventing eye damage and giving a very clear picture of the state of the end face. Will show dirt & debris as well as damage and scratches.

Fiber Optic Inspection