Visual fault locator is also called red light pen, due to it use red light 650nm wavelength. The red light pen is the simplest tool to locate whether the optical fiber is broken. It is often used for short-distance testing within 5km. YINGDA will use this tool when assembling pigtails or splitters into optical fiber boxes. It is often used in the actual optical fiber wiring construction process. The following is a summary of professional skills for using a red light pen to detect optical fibers. I hope it can help you.
Equipment preparation and basic operation
Battery and interface adaptation
- Pay attention to the positive and negative directions when inserting the battery, and tighten the pen body to ensure good contact
- The LC interface needs to be connected to the red light pen with a conversion head(2.5mm to 1.25mm adapter), and the SC/FC interface can be directly inserted
SC/FC/ST connector → Direct plug-in visual fault locator
LC connector → Adapter + visual fault locator
The key to end face cleaning
- Use anhydrous alcohol cotton pad to clean the fiber end face to avoid false breakpoint misjudgment caused by dust
- Interface pollution will cause red light attenuation by more than 50%
Tips for selecting detection mode
| Mode | Applicable scenarios | Operation tips |
| Constant light mode | Dark environment on/off detection | Press and hold the switch for 2 seconds to start, and observe the red light transmission of the entire link |
| Flashing mode | Strong light environment/precise location of breakpoints | Short press to switch, the red light pulse makes it easier to identify the light leakage point |
| Combination application | Multi-fiber core complex scenarios | The flashing mode marks a specific fiber, and the constant light mode verifies the connectivity |
Example: When inspecting the fiber distribution box in the corridor during the day, the flashing mode can penetrate the interference of sunlight.
Practical skills for fault location
Precise location of breakpoints
- When a light leak is found, gently pinch both sides of the optical fiber to observe the change in red light intensity. The strongest point is the core of the break
- Bending damage: continuous red light leakage → adjust the bending radius > 5cm (single mode)/3cm (multimode)
Fusion point/cold splice detection
- Qualified fusion point: uniform red light transmission without scattering
- Cold splice defect: obvious red light haloing at the interface (attenuation > 3dB requires redoing)
Key points for improving safety and accuracy
Safety taboos
- Do not look directly at the output port with naked eyes (650nm laser can damage the retina)
- Red light pens are prohibited for optical fibers that have been opened for service (strong light will burn the optical module)
Environmental optimization tips
- Strong light scene: Wrap the detection section optical fiber with black tape to enhance the development
- Long-distance detection: With the fiber optic identifier, the effective detection distance is increased to 30km
Typical troubleshooting process
The red light pen only verifies physical connectivity and needs to be combined with an optical power meter to quantify the attenuation value.
The red light pen cannot emit light
Possible reasons:
1. The battery is not lit enough, and the battery is installed upside down. Replace it and check the battery to solve the problem
2. The aluminum shell battery compartment is not tightened, tighten the aluminum shell to solve the problem.
3. The light is burned out and needs to be returned to the factory for repair.
The red light pen emits normally, but cannot be used normally.
Possible reasons:
1. Check whether there is any stain on the light outlet. If so, first remove the metal cap and the magnetic sleeve, wipe them with a cotton swab or dust-free paper dipped in alcohol, and then reinstall them in order.
The ceramic sleeve is broken. Use tweezers to remove the damaged and broken ceramic sleeve, and replace it with the ceramic sleeve provided by random.
The red light pen emits weak light
Possible reasons:
1. The battery is low, please replace and check the battery
2. The light head is burned out, please return to the factory for repair.
