Welcome to Fluke Fiber 07: Tier 2 OTDR Testing with the OptiFiber Pro
Course Duration: 35–45 minutes
Tier 1 tells you how much loss a link has. Tier 2 tells you where it is. This course covers how an OTDR works, the Fluke OptiFiber Pro models and specs, launch and tail cords, Auto, DataCenter, and Expert modes, SmartLoop bidirectional testing, and the extra care that singlemode and long links need.
What You'll Learn:
- Explain how an OTDR turns backscatter and reflections into a trace
- Identify OptiFiber Pro models and read their specs
- Use launch and tail cords correctly
- Choose Auto, DataCenter, Expert, or FaultMap mode
- Use SmartLoop and handle long singlemode and PON links
Course Structure
- How an OTDR Works
- Meet the OptiFiber Pro
- Launch & Tail Cords
- Setting Up a Test: Auto, Expert & DataCenter
- SmartLoop & Bidirectional Testing
- Singlemode & Long Links
- Final Assessment — 10 questions, 80% (8 of 10) to pass
Each section ends with a knowledge check. You get two attempts, and a first miss gives you a hint, not the answer. Finish the check to unlock the next section. You'll enter your name and email just before you submit the final assessment. Your results are emailed automatically to the training administrator, with a copy to you, whether you pass or not.
Section 1: How an OTDR Works
An OTDR (optical time domain reflectometer) sends short pulses of light into one end of a fiber and measures what comes back over time:
- Backscatter: the glass scatters a tiny fraction of light back all along the fiber. Its slow decline shows the fiber's attenuation.
- Reflections: glass-to-air interfaces (connectors, mechanical splices, breaks, the fiber end) send back sharp spikes.
- Steps: sudden drops in backscatter show loss at splices, bends, and connectors.
Time becomes distance using the fiber's index of refraction (IOR). The light travels out and back, so the distance is half the round trip:
That's Tier 2: unlike an OLTS total, the OTDR shows where each loss is and how big it is. It's the tool for locating faults, documenting splices, and characterizing long links. Tier 1 (OLTS) is still the most accurate measurement of total link loss.
Section 2: Meet the OptiFiber Pro
| Model | Wavelengths |
|---|---|
| OFP2-100-M | Multimode 850 / 1300 nm |
| OFP2-100-S | Singlemode 1310 / 1550 nm |
| OFP2-100-Q (Quad) | 850 / 1300 / 1310 / 1550 nm |
| OFP2-200 HDR | High-dynamic-range singlemode: 1310/1550, with 1490 or 1625 nm options, for long links and PON |
| Spec (Fluke datasheet, typical) | Value |
|---|---|
| Event dead zone | 0.5 m at 850 nm, 0.6 m at 1310/1550 nm (typical) |
| Attenuation dead zone | 2.5 m at 850 nm, 3.6–3.7 m singlemode (typical) |
| Dynamic range | 28 dB at 850, 30 at 1300, 32 at 1310, 30 at 1550 nm; HDR up to 42 dB at 1310 nm |
| Distance range | 40 km multimode, 130 km singlemode |
| Pulse widths | 3–200 ns at 850 nm; up to 20,000 ns at 1300/1310/1550 nm |
| Laser safety | Class 1 OTDR, Class II VFL |
| Battery | about 8 hours of Auto OTDR testing |
| Operating temperature | −18 to 45 °C |
Key terms
- Event dead zone: how close two reflective events can be and still be seen as separate.
- Attenuation dead zone: how far after an event before the next event's loss can be measured.
- Dynamic range: how much total loss the OTDR can see through before the trace drops into noise. It limits how long or lossy a link you can test.
Section 3: Launch & Tail Cords
An OTDR can't measure the first connector of a link: it's lost in the instrument's own dead zone. And the last connector has no fiber after it to show the step. So every Tier 2 test uses:
| Cord | Where | Purpose |
|---|---|---|
| Launch cord | Between the OTDR and the near end of the link | Moves the first link connector out of the dead zone so its loss and reflectance can be measured |
| Tail (receive) cord | At the far end of the link | Gives backscatter after the last connector, so its loss can be measured too |
Fluke's launch cords are 105 m multimode, 160 m singlemode launch cords. The tester can subtract the launch and tail cords so results start and end at the link's own connectors (launch compensation).
Section 4: Setting Up a Test: Auto, Expert & DataCenter
| Mode | What it does | When to use it |
|---|---|---|
| Auto OTDR | Picks the range, pulse width, and averaging time from the link it detects | Most certification and documentation work |
| DataCenter OTDR | One-touch settings tuned for short, connector-dense data-center links | Short links with many closely spaced connections |
| Expert / Manual | Starts from Auto, then lets you set range, pulse width, averaging time, and wavelength | Long links, troubleshooting, or separating closely spaced events |
| FaultMap | A quick look (around 2 to 10 seconds) that maps connections and faults | Fast troubleshooting and connection counting |
Basic test
- Choose the module and fiber type, the test limit (standard or customer specification), and the IOR or cable type.
- Inspect and clean the OTDR port, the launch cord, the link connectors, and the tail cord.
- Connect OTDR → launch cord → link → tail cord.
- Run the test at both wavelengths. Review the EventMap (a graphical map of connectors, splices, and faults), the trace, and the event table.
- Save it under the cable ID.
Pulse width trade-off
Narrow pulses separate closely spaced events (good for short, dense links) but reach less far. Wide pulses push through long, lossy links but blur nearby events together. Auto mode balances this. In Manual mode, you choose.
Section 5: SmartLoop & Bidirectional Testing
OTDR splice-loss readings depend on direction. Where two fibers with different backscatter properties join, one direction can show a “gain” and the other an exaggerated loss. The true loss is the average of both directions.
SmartLoop™
- Connect the launch cord to fiber 1, loop fiber 1 to fiber 2 at the far end through the tail cord (or a loop cord), and come back on fiber 2.
- One test analyzes both fibers and gives bidirectional averaged results, without walking to the far end to swap.
- The launch and tail cords stay in their standard positions, which meets the standard requirement for bidirectional testing.
- SmartLoop is included free on all OptiFiber Pro modules.
When bidirectional is needed
- Accurate splice-loss documentation, especially on singlemode backbones and outside plant
- When a splice shows a “gain” in one direction
- When the project specification calls for it
Section 6: Singlemode & Long Links
Long singlemode links
- Check dynamic range first: link loss plus a healthy margin must fit inside the OTDR's dynamic range, or the far end disappears into noise. The HDR models offer up to 42 dB at 1310 nm.
- Choose wider pulses and longer averaging for long runs. Expert mode lets you set them.
- Set the IOR from the cable data sheet, because distance errors grow with length. At 0.1% error, a 20 km link is off by 20 m.
Two wavelengths find bends
The OptiFiber Pro compares event loss across wavelengths to flag macrobends. A bend loses much more at 1550 nm than at 1310 nm, while a good splice loses about the same at both.
PON and 1625 nm
The HDR models support PON testing (Auto PON finds splitters, up to three cascaded) and offer 1490 nm or 1625 nm. 1625 nm is commonly used for testing out-of-band on live networks without interfering with traffic. Always confirm with the network owner before you connect to anything in service.
Final Assessment
Answer all 10 questions. You need 80% (8 of 10) to pass. These questions are different from the section knowledge checks. Enter your name and email below the questions, then submit.
Your Information
When you submit, your results are emailed automatically to the training administrator, and a copy is sent to the email address you enter here — whether or not you pass.
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