encircledflux fols webinar
TRANSCRIPT
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The need for Encircled Flux,
real or imaginary?
AdrianYoung
Fluke NetworksDecember 13th, 2012
Version 1.7
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Fiber Optics LAN Section
Overview:
Part of the Telecommunications IndustryAssociation (www.tiaonline.org)
Formed 198 years ago
Mission: to educate users about the benefits of
deploying fiber in customer-owned networks
FOLS provides vendor-neutral information
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Fiber Optics LAN Section
Current Members 3M
AFL/Noyes FiberSystems
Berk-Tek, a NexansCompany
Corning
CommScope Draka Communications
Fluke Networks General Cable
Leviton
OFS
Ortronics/legrand
Sumitomo ElectricLightwave
Superior Essex
TE Connectivity
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Fiber Optics LAN Section
Recent Webinars Available on Demand
Preventing Network Failures by thoroughly Cleaning &
Testing FO Connectors
Tier 1 and Tier 2 Testing: Trouble Shooting &
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Visit www.fols.orgor our channel on BrightTalk
Webinars are eligible for CEC credit for up to two
years after they are first broadcast.
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Whats the issue
Mandrels are they needed?
Review of standards
Coupled Power Ratio
Test methods
Mode controllers
In this webinar
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Encircled Flux (EF) is the final piece in the puzzle toreducing measurement uncertainty in the field
Reducing multimode uncertainty
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Even today folks are not using mandrels to control the launch
The issue Launch control
Multimode Source 1Power Meter 1
Multimode Source 1Power Meter 1
No mandrel, reading may be pessimistic
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Mandrels
Mode is from the Latin for path/way
So Multimode is Multiple Paths/Ways
Higher and lower order modes found in sources
Higher modes are less stable
Lower modes are more stable
Need to remove those higher order modes
And that is what the mandrel does
Helps reduce measurement differences between different
sources
The issue Launch control
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Make an optical loss measurement
Using reference grade connectors
Better than 0.10 dB on the test reference cords
With a mandrel at the source
The issue Launch control
Multimode
Source 1
Power Meter 1
Do not use Bend
Insensitive Fiber TestReference Cords
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Make another optical loss measurement
Using the same reference grade connectors
Better than 0.10 dB on the test reference cords
With the same mandrel at the source
But using a different source
The issue Launch control
Multimode
Source 2
Power Meter 1
Do not use Bend
Insensitive Fiber TestReference Cords
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Diagrams shown to visualize the issue as best as possible
Launch at source is different
Source 1Over filled
Source 2Under filled
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Only the power meter is calibrated to traceable standards
The optical source has no traceable calibration
Thats why there is a standard to specify the sourceoutput, Encircled Flux
Traceable calibration
Traceablecalibration
No traceablecalibration
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Attempted to limit variation
Specified something called
Coupled Power Ratio
For Multimode measurements, a Category 1 light sourcewas required (850 nm example here)
Lets look at how that was determined
ANSI/TIA-526-14-A (2003)
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Coupled Power Ratio
1.
If testing a 50/125 !m fiber optical link, you would connectthe source and meter together using a 50/125 !m cord
2. After allowing the source to stabilize, record the receivedpower in dBm
Multimode SourcePower Meter
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Coupled Power Ratio
3.
Insert a singlemode cord and record the received poweragain
4. The difference in power received defines the category of
light source (850 nm example below)
30 mm loop actsas a mode filter
TIA requirement for multimode
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CPR assessment shortfall
Source 1Over filled
Source 2Under filled
CPR compares power in center to total power.
It cant provide assessment of mode power distribution in the outer radiiwhich is critical to obtain good agreement with different test instruments.
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EF assessment improvement
Source 1Over filled
Source 2Under filled
EF specifies power throughout core using multiple control radii.
EF provides tight tolerance on mode power distribution in the outer radiienabling improved agreement between EF-compliant test instruments.
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Some believe the source should be a VCSEL
Reasoning
Use the same source type as the active equipment
Problem
The optical loss limits in IEEE 802.3 are based on test equipment
using LEDs, same for ANSI/TIA and ISO/IEC
VCSELs are under filled results in optimistic readings
Launch condition varies greatly from source to source
What Category is a VCSEL source?
VCSEL alert
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Using the CPR method shown previously as found in ANSI/TIA-526-14-A
A VCSEL is somewhere between Category 3 & 4
Dont use a VCSEL unless you are specifically told to do so
Some vendors will not warrant a cabling system if a VCSELsource is used to test
VCSEL alert
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Replaced with ANSI/TIA-526-14-B (Oct 2010)
Also known as IEC 61280-4-1 edition 2,
Replaces Coupled Power Ratio with Encircled Flux
ANSI/TIA-526-14-B titled:
Optical Power Loss Measurements of Installed Multimode Fiber
Cable Plant
IEC 61280-4-1 edition 2, titled:
Fibre-Optic Communications Subsystem Test Procedure
Part 4-1: Installed cable plant- Multimode attenuation measurement
ANSI/TIA-526-14-A
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Was considered adequate for the time (2003)
Test limits getting tighter
1000BASE-SX (2.6 dB over OM1)
10GBASE-SR (2.6 dB over OM3)
Consultants tightening loss budgets
Manufacturers tightening loss budgets
ISO/IEC 14763-3 (2006) changed to MPD
Modal Power Distribution
Tighter than CPR
Now also adopting Encircled Flux to replace MPD
ANSI/TIA-526-14-A
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Titled:
Generic Telecommunications Cabling for Customer Premises
Addendum 2, General Updates
Published August 2012
New application limits
40GBASE-SR4 (100 m, 1.9 dB over OM3)
40GBASE-SR4 (150 m, 1.5 dB over OM4)
100GBASE-SR10 (100 m, 1.9 dB over OM3)
100GBASE-SR10 (150 m, 1.5 dB over OM4)
Limits are getting tighter, CPR and MPD no longer goodenough
ANSI/TIA-568-C.0-2
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Sadly, most folks are setting a reference this way
Issues
You have no idea what the loss is in the adapter
Whatever it is, its subtracted from your measurement
The uncertainty is horrendous negative loss
What is done today
? dB
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So you end up with this
Issues
You have no idea what the loss is in the adapter
Whatever it is, its subtracted from your measurement
The uncertainty is horrendous negative loss
What is done today
x dB z dB
y dB
Measurement = x + y + z - ?
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Lets take an example
Issues
You have no idea what the loss is in the adapter
Whatever it is, its subtracted from your measurement
The uncertainty is horrendous negative loss
What is done today
0.75 dB
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Lets take an example
Issues
You have no idea what the loss is in the adapter
Whatever it is, its subtracted from your measurement
The uncertainty is horrendous negative loss
What is done today
0.3 dB 0.3 dB
0.1 dB
Measurement = 0.3 + 0.1 + 0.3 0.75
= -0.05 dB
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ANSI/TIA describes this as Method A
Not for enterprise cabling systems
Used in long haul measurements
Uncertainty of one connector not considered critical?
What is done today
? dB
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For testing an installed fiber optical link, should always usethe 1 Jumper Reference Method
Does require the test equipment to have interchangeable
adapters on the INPUT ports
What is done today
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Removed from INPUT port only
Its ok to remove the fiber from the input ports
You cannot remove the fiber from the output port, doingso will invalidate the reference you just made
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To the INPUT ports
Connect known good cord
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To the INPUT ports
Connect known good cord
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How do I know if those cords are good?
Connect known good cord
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Connect them together using a singlemode adapter andmeasure the loss
Verifying the cords
ISO/IEC 14763-3 "0.1 dB for Multimode
"0.2 dB for Singlemode
ANSI/TIA-568-C.0 "0.75 dB?
Cabling Vendors "0.50 dB?
Why not save this as proof of good test reference cords?
*
* This can be up to 0.15 dB for LC
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Test Reference Cord Values
ISO/IEC 14763-3
1 Jumper method (0.1 dB for Multimode and 0.2 dB for Singlemode)
ANSI/TIA-568-C.0
Does not call out test reference cord values ("0.75 dB?)
You are expected to specify this
Require documentation of TRCs
?
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Disconnect
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ANSI/TIA-568-C.0
First and last connections "0.75 dB
All other connections "0.75 dB
Connect to the fiber optic link
!0.75 dB !0.75 dB
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ISO/IEC 11801:2010 & ISO/IEC 14763-3
First and last connections "0.30 dB
All other connections "0.75 dB
Connect to the fiber optic link
!0.30 dB !0.30 dB
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In ISO/IEC 14763-3 (2006), cords were recognized as asource of great uncertainty
This standard reduced uncertainty by defining theperformance of the test cord connector
Reference grade connectors were required
Multimode "0.10 dB
Singlemode "0.20 dB
Impact of test reference cords
0.75 dB0.10 dB
!0.30 dB
0.75 dB0.20 dB
!0.50 dB
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ISO/IEC 14763-3 group working on this
The figure of 0.09 dB assumes 1 Jumper Referencemethod with a test reference cord using a reference grade
connector of 0.10 dB
Excludes Encircled Flux uncertainty
Measurement uncertainty
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Myth: cannot use 1 Jumper Reference
LC to SC fiber links
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Myth: cannot use 1 Jumper Reference
LC to SC fiber links
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Myth: cannot use 1 Jumper Reference
LC to SC fiber links
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Myth: cannot use 1 Jumper Reference
LC to SC fiber links
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Myth: cannot use 1 Jumper Reference
LC to SC fiber links
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Titled:
Practical Considerations for Implementation of Multimode Launch
Conditions in the Field
Currently in draft
TSB = Telecommunications System Bulletin
Not an official standard
An advisory document
Chances are will end up in ANSI/TIA-568-D.3
Helps users understand Encircled Flux and the options for
implementing it
Look out for TIA-TSB-4979
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Option 1
Ignore it
Practical implementation of EF
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Option 2
Use an external mode controller
Replaces the mandrels
Practical implementation of EF
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Practical Considerations
of Encircled Flux Compliance
Todays solution
When that LC connector breaks or
wears out, it cannot be re-terminatedin the field
Re-terminations need to beverified for EF compliance
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So why not just make the source EF compliant?
EF compliance is at the end of the test cord
Practical Considerations
of Encircled Flux Compliance
EF Compliance is met at the end of the Test Reference Cord
A Test Reference Cord will alter the EF template
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Can I add a sacrificial cord to protect that LC?
Adapter concentricity may not be good enough
Fiber core would have to be 0.5 !m
diameter for the sacrificial cord
No practical way to verify in the field
Practical Considerations
of Encircled Flux Compliance
Sacrificial cord
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Similar to the CPR method, ANSI/TIA-526-14-B describesa field artifact, with multiple concatenated offset splices
The idea is to characterize the loss through the artifact
with an EF compliant launch and compare this loss with afield light source
While this artifact has been qualified in test labs, none
exist commercially
At this time, the only way to measure for EF compliance is
in a lab with bench top equipment designed to measurenear field radiation
Verifying EF compliance in the field
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It is claimed that different labs show different results whenverifying EF compliance
TIA initiated a round robin test
19 months and 14 vendors later, the results were
presented to TR 42.11
There was good agreement amongst all vendors exceptfor one (defect in camera)
Biggest myth on EF
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At a minimum, use a mandrel
This does not yield the controlled launch condition the industry
desires that is Encircled Flux
Dont use a VCSEL source
Too much variability
Consider investing in fiber optic test equipment that allows
a 1 Jumper Reference reduced uncertainty
Verify your Test Reference Cords
Save the results and make it part of your documentation
If Encircled Flux is a contractual requirement, use mode
controllers for now
Summary
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