Chapter 1 Fibre Basics Fibre safety rules Keep all food and beverages out of the work area If fibre particles are ingested they can cause internal hemorrhaging Always ID: 560988
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Slide1
Network IQ Training Manual
Chapter
1
– Fibre BasicsSlide2
Fibre safety
rules
Keep
all food and beverages out of the work area. If
fibre
particles are ingested
they
can
cause internal hemorrhaging.
Always
wear safety glasses with side shields to protect your eyes from
fibre
shards
or
splinters. Treat
fibre
optic splinters the same as you would treat glass splinters.
Keep
track of all
fibre
and cable scraps and dispose of them properly. If
available,
work
on black work mats and wear disposable lab aprons to minimize
fibre
particles
on
your clothing.
Fibre
particles on your clothing can later get into food, drinks
, and/or
be ingested by other means
.
Never look directly into the end of
fibre
cables – especially with a microscope – until
you are positive that there is no light source at the other end – having tested it with a power meter. Use a
fibre
optic power meter to make certain the
fibre
is
dark. When using an optical tracer or continuity checker, look at the
fibre
from an angle at least 6 inches away from your eye to determine if the visible light is present
.
Contact lens wearers must not handle their lenses until they have thoroughly washed their
hands and Do
not touch your eyes while working with
fibre
optic systems until your hands have
been thoroughly washed.
Keep
all combustible materials safely away from the curing ovens and fusion
splicers.
When finished with the lab, dispose of all scraps properly. Put all
fibre
scraps in a
properly marked container for disposal.
Thoroughly clean your work area when you are done.Slide3
Safety Precautions
Chemical Safety
Isopropyl Alcohol is Flammable at 12.2°C and can cause irritation to eyes on contact. In case of eye contact. flush eyes with water for at least 15 minutes
Laser Handling Precautions:
Communication System Laser Light is Invisible
Viewing it Directly does not Cause Pain. The Iris of the Eye will not Close Involuntarily as when Viewing a Bright Light. Consequently. Serious Damage to the Retina of the Eye is PossibleShould Accidental Eye Exposure to Laser Light be Suspected. Arrange for an Eye Examination Immediately
If any of Corning's procedural recommendations conflict with your company's safety procedures.
Then
your company's procedures should take precedence
.Slide4
Safety Precautions
Most sources are low-power and no great risk
High power sources might burn the retina with invisible light
Hea
l
thy
Co
r
nea
Damage
Retina DamageSlide5
New Classification of Lasers; IEC 60825
Class
Output description
Health/Safety Issues
Example Sources
Class 2
Emits 400-700nm (visible) light. < 1mW (Continuous)
Blink reaction normally prevents damage.
Many laser pointers.
Unicam CTS laser
Class 2M
Emits 400-700nm (visible) light
Blink reaction normally prevents damage. but can damage if viewed with optical magnifier
Rifle site. laser pointer
Class 3B
315 - 1400nm. <500mW (contin)
400-700nm. <30mJ (pulsed)
May damage eye if viewed directly or reflected light but not likely. Probability low to cause fire.
Industrial. military. medical lasers. Must have key switch and lock
Class 4
> 500mWCan burn skin and damage eye; may ignite materialsIndustrial. military. medical lasers. Must have key switch and lock
Lasers defined in terms of maximum permissible exposure (MPE)
Laser classification is a function of
power (pulsed or continuous)
beam coherence
wavelength
safety containment around beam
More details in reference slidesSlide6
Fibre Handling Precautions
Cleaved glass fibres are sharp and can pierce the skin easily.
Find all pieces of fibre so that they do not cause problems later.
Use tweezers to pick up pieces of the glass fibres and place them on a loop of tape or in a plastic bottle. Dispose of them properly.
Wear gloves when stripping cable.Slide7
Cable
Handling Precautions
Fibre optic cable is
sensitive to excessive pulling
.
bending and crushing forces. Do not bend cable more sharply than the minimum recommended
bend radius
.
Do not apply more
pulling
force to the cable than specified.Crushed. kinked or over-pulled cable.
may be damaged and require replacement of the cable.
Crack!
Rule of Thumb – Minimum Bend Radius
During Installation > 15 x Cable OD
Relaxed > 10 x Cable ODSlide8
Fibre versus Copper
Media
Unrepeatered
Distance
Bandwidth
Voice Channels
(per Cu pair or per fibre)
Typ. Cable Weight
Typ. Cable Diameter
Copper
2.5km
1.5
44
Mbps
(T-1)
24
5200kg/km
(400pair)
60mm(400pair)Fibre100+ km2.5 Gbps +(OC-48)32.000 + 130kg/km (24 fibre)11.6mm(24 fibre)
Fibre cables transmit more information over longer distance
Fibre
provides
1000
x
more
bandwidth
and up to 10
0
x
longer links
Fibre cables are smaller and lighter
Fibre cable with the same
information-carrying capacity (bandwidth) < 1% size. weight of equivalent copper cable Slide9
Fibre Anatomy
Core
:
Carries the light
Cladding
: Keeps the light in the coreCoating : protects the core & claddingCannot separate core from cladding!
125
μ
m
125
μ
m
50
μ
m
or
62.5μm8μmSingle-modeMultimodeSlide10
Fibre Anatomy
in
details
The Core:
is a thin filament made of glass or plastic, measured in
micra ( 1µm = 0,000001m) where the light pass through. The larger the diameter of the core, the more light it can conduct.Cladding: Layer that revests the core. Since it has a refraction index lower than the core, it prevents the light from being refracted, hence allowing the light to reach the reception device.Coating: Plastic layer that revest the skin, protecting the optical
fibre
from mechanical shocks and excess of bending.
Mechanic resistance
fibres
: Fibres
that help to protect the core against impacts and excessive tensions during their installation. They are usually made of a material called kevlar, the same used on bullet-proof vests.Outer Jacket: Is the jacket that covers the optical fibre
.Slide11
Types Of Optical Fibre
Single-mode:
Allows only one mode (ray) of light to travel
through the core
Multimode:
Allows multiple modes (rays) of light to travel
through the coreSlide12
Multimode vs. Singlemode – Total Internal Reflection
125
62.5
125
50
125
9
The physical properties of
singlemode
fibre
offer very low attenuation over distance, which is why
singlemode
fibre
is used to connect cities, campuses and wide area telephone and data networks. Multimode
fibre
cables experience more attenuation, or loss, per the same distance than
singlemode
fibre.Typically Multimode fibre is used within buildings and to connect buildings together in a campus environment. Lastly, plastic optical fibre has the highest attenuation, or loss of light per distance compared to the glass fibre cable types mentioned above. For many applications the maximum distance for plastic fibre cable is less than 10 meters.Slide13
Principle of Operation
-
Index of Refraction
Index of Refraction is abbreviated with the letter n
Speed of Light = 299.792.458 m/s (186.282 miles per sec)
Index of Refraction
1.0
1.0003
1.33
1.46
1.48
Medium
Vacuum
AirWater
CladdingCore
Speed of Light in a Medium
Speed of Light in a VacuumIndex of Refraction (n) =Slide14
Refraction
n
1
sin
1 = n2 sin 2
Refraction law
1
=
Angle
of
incidence2
= angle of refraction
refraction index n2
Interface
Medium 1
refraction
index n1 Medium 2 1 1 2 2 first wavefrontsecond wavefrontLot at the interfaceSlide15
Law of reflection
= ´
Law of reflection
=
Angle
of
incedence
Interface
Medium 1
Medium 2
´
´
= Angle of reflectionIn most cases, refraction and reflection occur simultaneously: Only a portion of the light is reflected thereby and the remainder enters on the other medium (according to the law of refraction).index of refraction n1 index of refracton n2 Lot on the interfaceSlide16
Totalreflexion
Wenn n
1
> n
2
dann existiert ein Einfallswinkel G für den der Brechungswinkel = 90°sin G =n2/n
1
Für Einfallswinkel >
G
tritt die
Totalrelfexion
auf Hinweise
:Soll nur text bleiben
, oder durch Drawings added
Text changedComments
added
G = Grenzwinkel
Grenzfläche
Medium 1 Medium 2 G ´G Brechungsindex n2 Brechungsindex n1
> G
´ =
Lot auf der Grenzfläche
Slide17
Wenn
θ
1
>
θ
G
Totalreflexion
Möwe erscheint hier
Wenn
θ
1
<
θ
G
Brechung
nLuft = 1.0003nWasser = 1.33sin θG = (nLuft/nWasser) θG ≈ 49°θ ´
θ
2
Wirkungsprinzip
θ
G
θ
1
= Einfallswinkel
θ
G
= Grenzwinkel
θ
2
= Brechungswinkel
θ
´ = Ausfallswinkel
Fisch erscheint hier
θ
1
θ
1Slide18
Total Internal Reflection
If
(
n
core
>
n
cladding
) AND
If
critical angle not exceeded.
THEN Total Internal Reflection occurs
=
Slide19
System Performance Parameters
Light sources transmit light through the
fibre
at various
wavelengths
As the light travels down the fibre. attenuation occursAs the light travels down the fibre
.
dispersion
occurs which affects
bandwidthSlide20
System Performance Parameters
WAVELENGTH
is a characteristic of
light that is emitted
from the light sourceand is measured innanometers (nm)
TYPICAL OPERATIONAL WAVELENGTHS
850 nm
(MM)
1300 nm
(MM)
1310 nm
(SM)
1550 nm(SM)Slide21
Attenuation - Definition
•
Attenuation is
measured in
decibels (dB)
decibel (dB) = -10 log (P
out
/P
in
).
Pout = Received Power P
in = Transmitted PowerSlide22
Attenuation Samples
Attenutation
in
Decible
Remaining
power in %0.197.70.295.50.3
93.3
0.4
91.2
0.5
89.10.6
87.70.785.10.883.2
0.981.1179.4 ≈ 80263.1
350.1 ≈ 50439.8531.66
25.1 ≈ 25719.9 ≈ 208
15.8912.61010.0201.0300.1
400.01Performance P in mWPerformance in dBm1 W+30
dBm100 mW+20 dBm10mW+10 dBm5 mW+7
dBm
1 mW
0 dBm500 µW-3 dBm100 µW-10 dBm50 µW-20 dBm10 µW-23 dBm1 µW-30 dBm100 nW-40 dBm10 nW-50 dBm1 nW-60 dBm100 pW-70 dBm10 p W-80 dBm1 pW-90 dBm in dBm = 10lg Slide23
Types of Attenuation
Attenuation - measure of optical power loss.
T
wo Types of Attenuation:
1. Intrinsic 2. Extrinsic
- Absorption - Macrobending
- Scattering
- MicrobendingSlide24
Spectral Attenuation Curve
850
1300/1310
1550
“Windows of Operation”
MM
SM
Water
Peak
1383 nmSlide25
Intrinsic Attenuation – Absorption and Scattering
Absorption
- natural impurities in the
glass absorb light energy.
Scattering
- Light rays interact with glass on the atomic level and are scattered into new pathways that may be lost through the cladding.Slide26
Extrinsic Attenuation
Macrobending
Loss due to large scale bending from
ex
ternal sources
Corning’s new ClearCurve
®
fibres are macrobend resistant through innovative barriers between Core and Cladding
- Single-Mode ClearCurve
- Multimode ClearCurve
(see reference pages for details)Slide27
Extrinsic Attenuation
Microbending
loss due to small scale
distortions
S
mall bend affecting the fibre eg
.
cable ties installed too tight
.Slide28
System Performance Parameters: Dispersion
Dispersion is d
efined as the spreading of a light
pulse as it
travels down a fibre
Bandwidth is d
efined as the amount of information
that a
system can carry such that each pulse of light is
distinguishable by the
receiverSlide29
Dispersion - Modal Dispersion
In multimode fibre. an input pulse travels in different paths. called “modes”
Each ball is a mode
All of the balls start from the same pulse
Modal dispersion only occurs in MM fibreSlide30
Dispersion - Effect on Signal
Affects quality of the transmission
-Bandwidth
1 0 1
1 1 1
logical information
electrical input signal
transmitted optical signal
received optical signal (with dispersion)
electrical output signal
logical information
BIT ERRORSlide31
Optical transmitters
Beam Shape
Source Name
Light beam
Power/ Speed
Relative Cost
Light Bulb
Light not directed or focused. rays travel many directions
Low power (in 1 direction)
Cheap
LED
L
ight
E
mitting
D
iode
Large cone of light. large spectral width
Low power. Max speed 622Mbps
Cheap
LASER
L
ight
A
mplification by
S
timulated
E
mission of
R
adiation
Parallel beams. focused. very small spectral width
High power. very fast 10+Gbps
Expensive
VCSEL
V
ertical
C
avity
S
urface
E
mitting
L
aser
Well focused beam
. small spectral width
Mid power. very fast: 10Gbps
EconomicalSlide32
Optical transmitters - Spot size
The spot-size and the laser launch are factors which affect the fibre-bandwidth.
cladding/125µm
LASER
Tx
VCSEL
LED
Tx
Tx
core/50µm
coatings/250µm
Spot size 4-10µm
Spot size 20-30µm
Spot size > 100 µmSlide33
Pros and Cons Optical
Fibre
vs
Copper
Pros:High bandwidth: Using wavelength division multiplexing allows multiple 100 Tbit / s can be transmitted per fiberLow attenuation, high coverage: Without Optical Amplifier typical 100km, with optical amplifiers from several hundred to one thousand kilometersThe attenuation in the optical waveguide, as opposed to copper conductors independent of the frequency of the transmitted signalGlass is an insulator: Allows Isolation between transmitter and receiver.Immunity to electro-magnetic interferencesNo
signal radiation and thus relative
privacy
Use
in hazardous areas is possible
ConsOver fiber optic cabling no power supply is available. Requires additional copper cablingFiber
optic cable can not be located, if it contains no copper.High requirements in connection technology: Plug wiring, splicingMeasurement consumingThe components are still expensiveSlide34
Summary
Light signal travels in the core of the
fibre
.
This is possible because the cladding IOR is less than the core IOR
(ncore >ncladding)
The light rays travel in paths called modes.
Two types of
fibre
:
Multimode
Single-modeOptical signal loss (attenuation) is measured in dB (deciBel)Attenuation in
fibre caused by:Intrinsic Characteristics: Absorption. ScatteringExternal Characteristics: Macro/Micro- bendsAn optical pulse spreads as it travels through a fibre. Called Dispersion.
Sources/Transmitters used in Fibre SystemsLEDsVCSELsLasersSlide35