The Quick Answer
For patch cords and short building runs, a 5 km VFL from QBL does the job: the pen type or the smaller mini type. For longer runs, use the 30 km pen, which QBL rates for 30 km. QBL also makes a pocket-size 20 mW VFL. If you want a Platinum Tools unit, the Platinum Tools Visual Fault Locator is a 10 mW visible laser.
Comparison
| Product | Form | What the maker lists | Who it is for | Price |
|---|---|---|---|---|
| QBL VFL, Pen Type, 5 km | Pen | 5 km rated range (QBL) | Patch cords, building runs, splice trays | $104.99 |
| QBL VFL, Mini Type, 5 km | Mini | 5 km rated range (QBL) | The same jobs, in a smaller body | $104.99 |
| QBL VFL, Pen Type, 30 km | Pen | 30 km rated range (QBL) | Longer runs such as campus links and drops | $174.99 |
| QBL VFL, Pocket Size, 20 mW | 20 mW output (QBL) | Techs who want a pocket-size unit | $139.99 | |
| Platinum Tools Visual Fault Locator | Handheld | 10 mW visible laser (Platinum Tools) | Techs who already carry Platinum Tools test gear | $140.94 |
The ranges are QBL's own ratings for its units. How far you can actually see the light depends on the fiber, the jacket color and how bright the room is.
What a VFL Does, and What It Cannot Do
A VFL shines visible red light into a fiber. Where the fiber is broken, bent too tightly, or badly connected, the light escapes and you can see the glow, often right through a light-colored jacket or boot. That makes it the fastest way to:
- find a broken patch cord or a bad connector
- trace which fiber is which in a panel or splice tray
- check a fusion splice or a mechanical splice right after you make it
- confirm a fiber is continuous from end to end on a short run
A VFL cannot measure loss and cannot tell you the distance to a fault you cannot see. Light will not show through black or armored jackets, so on a buried run, or one in a dark or armored jacket, the fault stays hidden. That is the job of an OTDR.
The Picks
QBL VFL, Pen Type and Mini Type, 5 km
Best for. Techs who work on patch cords, building runs and splice trays, where 5 km of rated range is more than the job needs.
The pen type and the mini type carry the same 5 km rating from QBL. The choice between them is the body: pen or mini. For longer runs, look at the 30 km pen below.
QBL VFL, Pen Type, 30 km
Best for. Techs on longer runs, such as campus links and FTTH drops, who want more rated range than the 5 km units.
The 30 km pen is rated by QBL for 30 km. Our guide to VFL distance: 5 km vs 30 km goes into when the extra range matters.
QBL VFL, Pocket Size, 20 mW
Best for. Techs who want a pocket-size unit.
For the pocket VFL, QBL lists its output, 20 mW, not a range. Check the laser class on the unit before use; see the safety section below.
Platinum Tools Visual Fault Locator
Best for. Techs who already carry Platinum Tools test gear, such as the PT-OTDR-100, and want a VFL from the same maker.
The Platinum Tools Visual Fault Locator (TVFL100) is a 10 mW visible laser, per Platinum Tools.
When a VFL Is Enough, and When You Need an OTDR
A VFL is enough when you can see the fiber: patch cords, panels, splice trays and short indoor runs. It is also the right first check after any splice.
You need an OTDR when the fault is somewhere you cannot see, when you need the distance to a fault, or when a customer wants a trace showing loss at each connector and splice. Our mini OTDR buying guide covers the OTDR side, and OTDR vs power meter covers when a loss test is the better tool.
VFL Safety
A VFL is a laser. Never look into a fiber end, a connector or an open port while a VFL or any other light source is connected to the fiber. Check the laser class printed on the unit: the higher the class, the stricter the precautions. Our guide to VFL laser class safety explains the classes.
A note on goggles: QBL's laser safety goggles are rated for 800 to 1755 nm. That range covers the invisible infrared light used by OTDRs and network lasers, such as 1310 and 1550 nm. A VFL's visible red light is outside that range, so those goggles are for work around infrared sources, not protection from a VFL.
VFLs We Do Not Sell
You will also see VFLs such as the Fluke Networks VisiFault and the EXFO FLS-240 Pocket Pal. We do not sell them. If you are comparing, ask each one the questions in the next section.
How to Choose a VFL
- Run length. Short indoor runs and patch cords: a 5 km unit. Longer runs: a 30 km unit.
- Body. Pen, mini or pocket, whichever you will actually carry.
- Connector fit. Check that the VFL's port fits the connectors you work on, or that an adapter is included.
- Laser class. Know the class of the unit and follow the safety rules for it.
FAQ
What is a visual fault locator?
A visual fault locator (VFL) is a handheld laser that shines visible red light into a fiber. Breaks, tight bends and bad connectors glow where the light escapes, so you can see where the problem is.
How far does a VFL reach?
It depends on the unit. QBL rates its pen and mini VFLs for 5 km and its long-range pen for 30 km. How far you can actually see the light also depends on the fiber, the jacket color and the lighting.
What is the difference between a VFL and an OTDR?
A VFL shows you where light escapes, so it works on fiber you can see. An OTDR reads light reflected back from the fiber and shows the distance to each connector, splice and fault, and the loss at each one, even on runs you cannot see.
Is a VFL laser safe to look at?
No. Never look into a fiber end or connector while a VFL is connected. Check the laser class printed on your unit and follow the safety rules for that class.
Do laser safety goggles protect against a VFL?
Not the ones we sell. QBL's laser safety goggles are rated for 800 to 1755 nm, which covers infrared light such as 1310 and 1550 nm. A VFL's visible red light is outside that range.
Shop VFLs
See every VFL and fiber tester we carry in test equipment.
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