Welcome to Fluke Fiber 03: First Tests: VFL, Power Meter & Light Source
Course Duration: 35–45 minutes
Before automated certification, every fiber technician should be able to find a fiber with a visual fault locator, read optical power, and measure loss by hand. This course teaches those basics with the tools built into the Fluke CertiFiber Pro.
What You'll Learn:
- Choose between the VFL, light source, and power meter
- Use the CertiFiber Pro VFL safely and know its limits
- Work with dBm, dB, and loss math
- Use Tools › Power Meter/Light Source and Far End Source mode
- Make a manual loss measurement and avoid common mistakes
Course Structure
- Your First Fiber Tools
- The Visual Fault Locator
- dBm, dB & Loss Math
- CertiFiber Pro as Power Meter & Light Source
- Making a Simple Loss Measurement
- Field Uses & Common Mistakes
- 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: Your First Fiber Tools
| Tool | What it tells you | What it can't do |
|---|---|---|
| Visual fault locator (VFL) | Continuity, which fiber is which, and breaks or tight bends near the end, by showing visible red light | Measure loss, or see through dark or armored jackets |
| Light source | Sends a stable signal at a known wavelength (850/1300 or 1310/1550 nm) | Measure anything by itself |
| Optical power meter | How much light arrives, in dBm, and so whether a fiber is live | Tell you where loss happens |
| Source + meter together | Loss in dB: the basis of Tier 1 testing | Locate events (that's the OTDR, courses 7–8) |
The Versiv CertiFiber Pro includes all of these: a VFL, light sources, and power meters in its main and remote modules. This course uses them one at a time. Courses 4–5 combine them into automated certification.
Section 2: The Visual Fault Locator
The CertiFiber Pro's VFL is a 650 nm, continuous or 2–3 Hz blink, Class II, 2.5 mm universal adapter red laser. You plug a connector into the VFL port and watch for the red light.
| Use | What you see |
|---|---|
| Continuity | Red light glowing out of the far-end connector means the fiber is continuous |
| Fiber identification | Light the fiber at one end and find the glowing port at the far panel. Blink mode makes it easier to spot. |
| Breaks and tight bends | Red glow leaking through a jacket, boot, or splice tray marks the spot |
| Polarity check | Confirms which strand at one end arrives at which port at the other |
Limits
- Visible red light is absorbed fairly quickly in fiber, so the VFL is a short-range tool, best on patch cords, inside-plant runs, and the first stretch of a longer link.
- Light only escapes where the jacket lets it show. You won't see it through black, armored, or heavily jacketed cable.
- It doesn't measure loss. A fiber can glow at the far end and still fail certification.
Section 3: dBm, dB & Loss Math
Absolute power: dBm
A power meter reads in dBm: decibels relative to 1 milliwatt.
| dBm | Power |
|---|---|
| 0 dBm | 1 mW |
| -3 dBm | 0.50 mW (about half) |
| -10 dBm | 0.1 mW (100 µW) |
| -20 dBm | 0.01 mW (10 µW) |
| -30 dBm | 0.001 mW (1 µW) |
Relative power: dB
Loss is the difference between two power readings, in dB:
Section 4: CertiFiber Pro as Power Meter & Light Source
On the Versiv main unit, open Tools › Power Meter/Light Source. The CertiFiber Pro meter covers 0 to −65 dBm at 850 nm and 0 to −70 dBm at the other wavelengths.
Using the remote as a far-end source
- Inspect and clean every connector you'll use.
- Connect the remote's OUTPUT port to the main unit's INPUT port with a test cord (or through the fiber under test).
- On a remote with a Quad module, hold the button next to the VFL port for 2–3 seconds until the output LED alternates red and green. That switches it from Smart Remote mode to Far End Source mode, and the TEST LED flashes.
- On the main unit, select the fiber type (MM or SM) and the wavelengths (for example, 850 and 1300 nm).
- Read the power in dBm. Tap REF to zero out the reference cord, then LOSS shows the loss in dB. POWER switches back to dBm.
- Tap SAVE to store the reading.
Readings saved from this tool have no loss limit attached. For PASS/FAIL, create a custom fiber test limit, or use the automated certification test (course 4).
Section 5: Making a Simple Loss Measurement
- Inspect and clean the source cord, the meter cord, and both ends of the link.
- Reference: connect the source cord to the meter, then tap REF at each wavelength.
- Leave the source cord on the source. Disconnect only at the meter end.
- Connect the source cord to one end of the link, and a meter cord from the far end of the link to the meter.
- Read the loss at each wavelength and save it under the fiber's label.
- Compare it with the link's loss budget (course 5 covers how to calculate one).
Why both wavelengths?
Fiber loses less at the longer wavelength (1300 nm vs. 850, or 1550 vs. 1310), but bends hurt the longer wavelength more. A link that is much worse at 1550 nm than at 1310 nm usually has a tight bend somewhere.
Section 6: Field Uses & Common Mistakes
Everyday uses
- Is it live? Before you inspect or disconnect a fiber in service, check it with the power meter. Any reading above the noise means light is present.
- Equipment output: measure a transceiver's transmit power, with the meter set to the matching wavelength, and compare it with the equipment's specification.
- Received power: measure what reaches the far-end equipment, to check the link has margin above the receiver's sensitivity.
- Finding a fiber: VFL in blink mode, then watch the far-end panel.
Common mistakes
| Mistake | Result |
|---|---|
| Wrong wavelength selected on the meter | Inaccurate readings; the meter is calibrated at specific wavelengths |
| Source cord unplugged at the source after REF | Invalid reference, so every loss reading is wrong |
| Uninspected connectors | Extra loss, and contaminated test cords |
| Multimode test cords on singlemode fiber (or the reverse) | Huge, meaningless losses |
| Loss reads negative (a “gain”) | The reference was taken with something dirty that's now clean, or the cords changed. Clean everything and re-reference. |
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.
Assessment Complete
Score: 0 / 0
Percentage: 0%
Status: —
Time in course: —