Session 4: Termination and Splices
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Transcript of Session 4: Termination and Splices
Session 4:
Termination and Splices
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FO Connectors Specifications Specifications
Loss Repeatability Environment (temp, humidity, vibration,
etc.) Reliability Back reflection Ease of termination Cost
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Connector Ferrules
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Connector End Finishes
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Connector Termination Processes
Epoxy/polish Hot-melt (3M trademark) Anaerobic Crimp/Polish Crimp/cleave Mechanical Splice
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Termination - Adhesive/Polish
Stripping The Fiber
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Connector Termination
Applying Adhesive
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Connector Termination
Crimping To The Cable
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Connector Termination
Cleaving The Fiber
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Connector Termination
“Air Polishing”
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Connector Termination
Polishing
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Connector Termination
Microscope Inspection
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Connector Termination
Direct With Core Illuminated
Angle View
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Fiber Optic Splices Permanent terminations for fiber Specifications
Loss Repeatability Environment Reliability Back reflection Ease of termination Cost
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Fiber Optic Splices
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Fiber Optic Splices - Fusion
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Fiber Optic Splices - Mechanical
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Fiber Optic Splices - Cleaving
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Connector & Splice Loss
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Back Reflection (Return Loss) Light reflects at surfaces
between materials of different indices of refraction
Glass to air interface yields about a 4% reflection
Occurs at fiber optic joints
Splices have lower back reflection due to fusing or using index matching fluid
Domed (PC) fiber end faces can minimize air to reduce back reflection
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Continuity Testing With visual tracer or fault locator
Tracer is flashlight or LED Fault locator uses visible red laser
Useful for verifying mechanical splices or prepolished/splice-type connectors
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Insertion Loss Testing
Simulates actual system operation
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OTDR Testing OTDR testing
OTDRs OTDRs are valuable tools for testing fiber
optics. They can verify splice loss, measure length and find faults.
used to create a blue print of fiber optic cable when it is newly installed.
Later, comparisons can be made between the "blue print" trace and a second trace taken if problems arise.
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OTDR Testing
OTDRs work like "optical RADAR," sending out a test pulse and looking for return signals.
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OTDRs See Backscattered Light
Scattering is the primary loss mechanism in fiber
Some light is scattered back to the source ~1 millionth of signal at 1310 nm
OTDR process Send out high power signal Gather backscatter light Averages signal Display backscatter signal over time
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Typical Result
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Information In The OTDR Display
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Fiber Attenuation and Distance
Attenuation Coefficient = (Psource –Pend)[dB]/fiber length [km]
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2-Point Loss
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Least Squares Loss
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Connector or Splice Loss By 2-Point Method
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Connector 2-Point Loss
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Connector or Splice Loss By “Least Squares”
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Connector Least Squares Loss
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Back Reflection (Optical Return Loss)
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Connector Reflectance
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OTDR Launch Cable
Pulse Suppressor /Testing Initial Connector
Testing Far End Connector
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OTDR Ghosts
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OTDR Pulse Width
Wider pulse = more energy = more range
But wider pulses mean less resolution 1 us => 3x108 m/s x 1x10-6 s = 300 m 1 ns => 3x108 m/s x 1x10-9 s = 0.3 m
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OTDR Resolution
1. to see an event close to the OTDR;2. to see two events close together.
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OTDRs and Multimode Fibers
• Laser test signal is smaller than core• Underestimates loss significantly
• OTDR is no substitute for insertion loss test
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Good OTDR Traces
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Improving OTDR TracesUsing index matching fluid
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OTDR Measurement ParametersApproximate Settings
Wavelength (850/1300 MM, 1310/1550 SM) generally do both wavelengths
Range (2 to 100+ km) Set to greater than 2X cable length
Pulse width (10 m to 1 km) Set as short as possible for best
resolution Averaging (1 to 1024 averages)
For short cables, 16-64 averages
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Range
• A 5.2 km link taken at ranges of 2 km (green), 5 km (brown) and 10 km (blue).
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Wavelength
• A single fiber at both 850 nm (green) and 1300 nm (blue) wavelengths.
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Pulse Width
• A single fiber measured at shortest (blue), median (brown) and longest (green) pulse widths.
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With 30 ns and 90 ns Pulse Width
90 ns (equivalent to 18 m) pulse width)
30 ns (equivalent to 6 m) pulse width
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Averages
no averaging
averaged 1024 times
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Index of Refraction nor nominal velocity of propagation (NVP)
we need to know n to calibrate the measured length of the fiber.Generally the fiber length is
~1% more than the cable to allow for cable stretching
the fault distance will be at ~ 99% of the distance shown by the OTDR
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1. Items 1,2,3 & 4 are all fiber segments. They all have different slopes. Why?
2. Why does the end of the fiber (5) have such a high reflection?
3. How what is the total length of the fibers ? a. The fibers in each segment have
different attenuation coefficients.b. It is cleaved neatly.c. 35.63 km
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What are we measuring here?
Length and loss or attenuation coefficient of a fiber segment between splices.
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1. What is the splice loss measured here?
2. What is the approximate pulse width used for the OTDR measurement?
a. Splice loss, 0.28 dBb. 300 m
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a. What is event 2 ?b. On very long fibers, what do we change on the
OTDR to get more distance?c. Why is the reflection at the end (5) so strong? d. Why does the trace look more “noisy” at point 3
than point 4 ?
b. Pulse width and range or length of the trace
a. Reflective splice or connector
d. As the OTDR trace goes further from the instrument, the power loss causes worse signal to noise performance – the trace will get noiser as it gets closer to the distance limit.
c. It’s is very nicely cleaved.
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1. This is an extremely long fiber. How long? How much loss?176.67 km, 39.13 dB2. Does it look like this is close to the limit of the OTDR range? Why?Yes, the trace is getting very noisy.
3. Why is there no reflective pulse at the end?It is not well cleaved.
Any Questions?
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