fiber optic tests mark ortel sales support eng scte member and supporter
TRANSCRIPT
Fiber Optic Tests
Mark Ortel
Sales Support Eng
SCTE Member and Supporter
© 2010 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION2
Agenda
Fiber Optics Key Concepts– Fiber types and Connectors– Fiber Connections: the good, the bad, and the ugly– Measurement Units
Inspection and Cleaning– Inspect Before You ConnectSM
– Inspect Both Sides– Proactive Inspection– Cleaning Best Practices
Introduction to Fiber Testing
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Fiber Connectors are Everywhere!
Fiber optic connectors are common throughout the network as they
provide the power to add, drop, move, and change the network.
Buildings
Multi-home UnitsResidential
CO/
Headend/
MTSO
Local Convergence Point
Network Access Points
Feeder Cables
Distribution Cables
Drop Cables
Inspection and Cleaning
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Fiber Optic Connector
Ferrule
Cladding
CoreBody
LC CONNECTOR
Body
Houses the ferrule that secures the fiber in place
Ferrule
Thin cylinder where the fiber is mounted and acts as the fiber alignment mechanism
Fiber: Cladding
Glass layer surrounding the core, which prevents the signal in the core from escaping
Fiber: Core
The critical center layer of the fiber; the conduit that light passes through
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Anatomy of Fiber Connectors
Light is transmitted and retained in the CORE of the optical fiber by total internal reflection.
The fiber connector end face has 3 major areas – the core, the cladding and the ferrule.
Particles closer to the core will have more impact than those farther out.
CORE – 9 µm (SM)CORE – 9 µm (SM)
CLADDING – 125 µmCLADDING – 125 µm
FERRULE – 1.25 or 2.5 mmFERRULE – 1.25 or 2.5 mm
Fiber End Face View
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Single Fiber vs. Multi-Fiber Connectors
SINGLE FIBER CONNECTOR MULTI-FIBER CONNECTOR
White ceramic ferrule One fiber per connector Common types include SC,
LC, FC, and ST
Polymer ferrule Multiple fibers in linear array
(for example, 8, 12, 24, 48, and 72) in single connector providing high-density connectivity
Common type is MPO or MTP®
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Common Single Fiber Connectors
FC connector– 2.5 mm ferrule – Screw mechanism with key –
aligned– Legacy – mainly used with single-
mode fibers
ST Connector– 2.5 mm ferrule – Twist-lock mechanism– Legacy – mainly used with
multimode fibers
SC Connector– 2.5 mm ferrule– Push-pull latching mechanism– Most widely used connector today
(LAN/WAN)
LC Connector– 1.25 mm ferrule – Finger latch– Fastest growing connector
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Types of End Faces
PC – Physical Contact APC – Angled Physical Contact
The angle reduces the back-reflection of the connection.
SC - PC SC - APC
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Focus on the Connection
Bulkhead Adapter
Fiber Connector
Alignment Sleeve
Alignment Sleeve
Physical Contact
FiberFerrule
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What Makes a GOOD Fiber Connection?
Perfect Core Alignment
Physical Contact
Pristine Connector Interface
The 3 basic principles that are critical to achieving an efficient fiber
optic connection are “The 3 Ps”:
Core
Cladding
CLEAN
Light Transmitted
Today’s connector design and production techniques have eliminated most of the challenges to achieving core alignment and physical contact.
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What Makes a BAD Fiber Connection?
A single particle mated into the core of a fiber can cause significant back reflection, insertion loss, and even equipment damage.
Today’s connector design and production techniques have eliminated
most of the challenges to achieving core alignment and physical contact.
The remaining challenge is maintaining a pristine end face. As a result,
CONTAMINATION is the No. 1 reason for troubleshooting in optical
networks.
DIRT
Core
Cladding
Back Reflection Insertion LossLight
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Contamination and Signal Performance
FIBER CONTAMINATION AND ITS EFFECT ON SIGNAL PERFORMANCECLEAN CONNECTION
Back Reflection = -67.5 dBTotal Loss = 0.250 dB
1
DIRTY CONNECTION
Back Reflection = -32.5 dBTotal Loss = 3.2 dB
3
CLEAN Connection vs. DIRTY Connection
This OTDR trace illustrates a significant decrease in signal performance when dirty connectors are mated.
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Illustration of Particle Migration
Each time connectors are mated, particles around the core become displaced, causing them to migrate and spread across the fiber surface.
Particles larger than 5 µm usually explode and multiply upon mating.
Large particles can create barriers (air gaps) that prevent physical contact.
Particles smaller than 5 µm tend to embed into the fiber surface creating pits and chips.
11.8µ
15.1µ
10.3µ
Actual fiber end face images of particle migration
Core
Cladding
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Particle Migration and Signal Performance
For each successive mating, actual dB values increase as signal performance decreases
Dirt particles near or on the fiber core significantly affect signal performance
Actual fiber end face images of particle migration
-20
-30
-40
-50
-60
-70
Baseline/Initial
Contamination
1st Mating 2nd Mating 3rd Mating
Signal Performance
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Once embedded debris is removed, pits and chips remain in the fiber.
These pits can also prevent transmission of light, causing back reflection, insertion loss and damage to other network components.
Most connectors are not inspected until the problem is detected… AFTER permanent damage has already occurred.
Mating dirty connectors embeds the debris into the fiber.
Core
Cladding
Back Reflection Insertion LossLight
DIRTPITS(permanent damage)
Mating force of 2.2 lb over 200 um diameter gives 45,000 psi.
Dirt Damages Fiber!
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Types of Contamination
Fiber end faces should be free of any contamination or defects, as shown below:
Common types of contamination and defects include the following:
Dirt Oil Pits & Chips Scratches
Single-mode Fiber
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Contamination Categories
LOOSEMost contamination comes from dry particles that have fallen onto the end face or have been “placed” there during handling
BONDEDMost stubborn particles are held in place with grease, oils, or dried residue from a wet cleaning process
MATEDParticles on the end face of a connector can also become embedded into the glass if mated with another connector
CONTAMINATION MUST BE CLEANED from the end face prior to mating in order to optimize the efficiency of an optical signal or interconnect
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Inspect Before You Connectsm
Follow the simple “INSPECT BEFORE YOU CONNECT” process to ensure
fiber end faces are clean prior to mating connectors.
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Inspect, Clean, Inspect, and Go!
Fiber inspection and cleaning are SIMPLE steps with immense benefits.
44 Connect
■ If the fiber is clean, CONNECT the connector.
NOTE: Be sure to inspect both sides (patch cord “male” and bulkhead “female”) of the fiber interconnect.
22 Clean
■ If the fiber is dirty, use a simple cleaning tool to CLEAN the fiber surface.
11 Inspect
■ Use a probe microscope to INSPECT the fiber.
– If the fiber is dirty, go to Step 2, Clean.
– If the fiber is clean, go to Step 4, Connect.
33 Re-inspect
■ Use a probe microscope to RE-INSPECT (confirm fiber is clean).
– If the fiber is still dirty, repeat Step 2, Clean.
– If the fiber is clean, go to Step 4, Connect.
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Inspect and Clean Both Connectors in Pairs!
Inspecting BOTH sides of the connection is the ONLY WAY to ensure
the connector will be free of contamination and defects.
Patch cords are easy to access and view compared to the fiber inside the bulkhead (or test equipment or network equipment) which are frequently overlooked. The bulkhead side may only be half of the connection, but it is far more likely to be dirty and problematic.
Bulkhead (Female) InspectionPatch Cord (Male) Inspection
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Proactive vs. Reactive Inspection
PROACTIVE INSPECTION:
Visually inspect fiber connectors at every stage of handling BEFORE mating them.
Connectors are much easier to clean prior to mating, before embedding debris into the fiber.
REACTIVE INSPECTION:
Visually inspect fiber connectors AFTER discovering a problem, typically during troubleshooting.
By this time, connectors and other equipment may have suffered permanent damage.
Dirty Fiber PRIOR to MatingFiber AFTER Mating and
Numerous Cleanings
Dirty Fiber PRIOR to
Mating
Fiber AFTER Cleaning
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Benefits of Proactive Inspection
Reduce Network Downtime Active network = satisfied customers
Reduce Troubleshooting Prevent costly truck rolls and service calls
Optimize Signal PerformanceNetwork components operate at
highest level of performance
Prevent Network Damage Ensure longevity of costly network equipment
PROACTIVE INSPECTION is quick and
easy, with indisputable benefits
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Cleaning Best Practices
Many tools exist to clean fiber Many companies have their own “best practices” Dry clean first. If that does not clean, then try wet cleaning. Always finish with dry cleaning!
Light Transmission
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Optical Communications
Communication technology, developed in the 70s, that sends optical signals down hair-thin strands of glass fiber
Transmitter Receiver
Light Rays Fiber
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Optical Fiber Types
Multimode Single-mode
2 Types
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Fiber Types MM
– High attenuation– 850 to 1300 nm transmission wavelengths– Local networks (<2 km)– Limited bandwidth– LAN/Industry
Fiber carries numerous light rays (mode) simultaneously through the fiber.
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Fiber Types SM
– Low attenuation– 1260 to 1660 nm transmission wavelengths– Access/medium/long haul networks (>200 km)– Nearly infinite bandwidth– Telecom/CATV– FTTx – CWDM/DWDM
Fiber carries a single light ray (mode).
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Measurement Units
dBm unit is decibels relative to 1 mW of power dBm is an ABSOLUTE measurement dB is a RELATIVE measurement
Relative Power (dB) =10*Log)(
)(
mWPt
mWPi
0 dBm -3 dBm -20 dBm -40 dBm
1 mW 0.5 mW 0.01 mW 0.0001 mW
Tx
Rx
2 dB
5 dB
1 mW = 0 dBm
1 dBLoss = 8 dB
-8 dBm
Absolute Power (dBm) =10*LogmW
mWPi
1
)(
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Attenuation
Optical power is lost as light travels along fibers– Primarily caused by absorption and scattering– Usually expressed in dB or dB/km.
SourceSource RECEIVERRECEIVER
Pin
(Emitted power)
Pout
(Received power)
Power variation
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Light scattered
Impurities
Absorption and Scattering
Absorption: Light is absorbed due to chemical properties or natural impurities in the glass. Accounts for about 5% of total loss.
Scattering is the loss of a light signal from the fiber core caused by impurities or changes in the index of refraction of the fiber. Accounts for
about 95% of total loss.
Pure Glass=Si O2
Si
SiO O O
Si
Si
O
Si
Cu
O
Imperfections
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Bending Losses
Microbending – Microbending losses are due
to microscopic fiber deformations in the core-cladding interface caused by induced pressure on the glass
Macrobending – Macrobending losses are due
to physical bends in the fiber that are large in relation to fiber diameter
Attenuation due to bending is increases with wavelength (e.g. greater at 1550nm than at 1310nm)
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Spectral Attenuation
1st Window
C-Band 1530 to 1565 nm (3rd window)
L-Band 1565 to 1625nm
E-Band 1360 to 1460nm
O Band 1260-1360 (2nd Window )
S- Band 1460 to 1530nm
U- Band 1625 to 1675 nm
Att
enua
tion
(dB
/km
)
Wavelength (µm)
0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7
OH-absorptionPeak
190 THz50 THz
1
2
0
3
4
5
OH-
OH-
Cut-off wavelength for singlemode fiber
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Loss Process
InputOutput
Impurities
ScatteringLossInjection
Loss
AbsorptionLoss
JunctionLoss
CouplingLoss
Macro or
micro bending
lossScattering
loss
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Sources
Characteristics LEDs Lasers
Output PowerLinearly proportional to drive
currentProportional to current above the
threshold
Current Drive Current: 50 to 100 mA Peak Threshold Current: 5 to 40 mA
Speed Slower Faster
Wavelengths Available 0.66 to 1.65 µm 0.78 to 1.65 µm
Spectral Width Wider (40-190 nm FWHM)Narrower (0.00001 nm to 10 nm
FWHM)
Fiber Type MM SM, MM
Ease of Use Easier Harder
Lifetime Longer Long
Cost Low High
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Detectors
Photodiodes: different spectral characteristics depending on the type of semiconductor different wavelength settings/calibration in power meter
Values for temp = 0°C
Values for temp = 23°C
Si: Silicon
GE: Germanium
InGaAs: Indium Gallium Arsenide
Si GE InGaAs
Meas. Range 600 - 1000 nm 850 - 1550 nm 1000 - 1650 nm
Characteristics Only for MM fibers For general use Recommended for 1625nm
S(A/W)
850 1310 1550 (nm)
GEInGaAs
0.5
1625
Si
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Dynamic Range
Difference between maximum input and minimum sensitivity.
Typical power meter dynamic ranges:– +20 dBm to -70 dBm for Telephony– +30 dBm to -55 dBm for CATV– -20 dBm to -60 dBm for LAN
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Optical Loss Budget
Maximum loss = Minimum power output of source minus minimum acceptable power level of receiver
Minimum loss = Maximum power output of source minus maximum acceptable power level of receiver
Optical Loss Budget:Bmax = Ptmin – Prmin
Bmin = Ptmax -Prmax
Opt
ical
Pow
er L
evel
(dB
m)
Maximum Loss (dB)
Minimum Loss (dB)
Ptmax
Prmax
Ptmin
Prmin
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Optical Loss Budget (Example 1)
1000BASE-LX GBIC– Ptmax = -3 dBm
– Ptmin = -9.5 dBm
– Prmax = -3 dBm
– Prmin = -19 dBm
Questions:– Can you connect one GBIC to
another with only a patchcord?
– How can you ensure that the fiber system does not exceed the maximum loss?
Optical Loss Budget:Bmax = Ptmin – Prmin
Bmin = Ptmax -Prmax
Opt
ical
Pow
er L
evel
(dB
m)
Maximum Loss (dB) = 18.5 dB
Minimum Loss (dB) = 0 dB
Ptmax -3 dBm
Prmax -3 dBm
Ptmin -9.5 dBm
Prmin -19 dBm