Category Archives: Fiber Optic Testers & Tools

Visually Locating Fiber Loss With VFL

As fiber links support higher speed network bandwidths with increasingly stringent requirements, it is becoming all the more important to ensure that your backbone links meet tightening loss standards. As network applications grow and expand, the need for higher data transmission capacity continues to grow as well. To guarantee reliable and efficient network connectivity and data transfer, the testing tool holds a key position in reducing the time spent identifying and locating the fiber loss. In this article, we will introduce an useful tool—visual fault locator (VFL) to achieve quicker, easier and more efficient fiber loss identification.

Introduction to VFL

VFL, also known as visual fault locator, serves as a fiber optic testing device that is widely used to locate the breakpoint, bending or cracking of the fiber glass. It can also locate the fault of OTDR dead zone and make fiber identification from one end to the other end. Designed with FC, SC and ST universal adapter, this fiber fault locator can be used without any other additional fiber adapters to locate fault up to 10 km in fiber cable. Featured by compact size, low weight and red laser output, the VFL is widely adopted to visually locate loss locations on fiber links and can also be employed to confirm fiber continuity.

Generally, there exist two types of commonly used VFLs : pen shape visual fault locator and hand-held visual fault locator, the following picture shows the outlook of them.

Visual fault locator

How Does VFL Work?

Since the light involved in transmitting signals over fiber optic is usually at 1300nm to 1650nm wavelength which is invisible to human, we can barely see it with our naked eyes. However, by injecting powerful visible light at 360nm to 670nm wavelength to the fiber, VFL helps to visually and directly locate the faults in fiber optic cable. This visible light keeps traveling along the core until it reaches a fault, then it leaks out, which can be seen through plastic coating and jackets. Thus, we can visually locate loss locations be it a macrobend, faulty connectors or a poor splice. In addition, VFL also helps to cover the range where optical time-domain reflectometers (OTDRs) are not useful because of the dead zone of the OTDR.

Fiber testing

Application of VFL

VFL is an ideal tool for locating defects that occur at connection and around fiber cabinets which are hidden in an OTDR “blind-spot” or “dead-zone”. Fiber breaks, faulty connector, sharp bends, bad splices and similar faults can be visually located by VFL. Visual fault locator can boost productivity in the field by providing fast detection, precise fault location, distance, loss, and ORL measurements.

Reference Guide to Use VFL

Network environments sometimes are too complicated for technicians to find the fault location, which makes visual fault locator a vital and indispensable tool for fixing the problem timely and precisely. The VFL is also used for conducting continuous tests and performing fiber identification. With visual fault locator, you can easily isolate high losses and faults in optical fiber cables. Here we offer you step-by-step procedures on how to use a VFL.

  • Step 1: Remove the plastic connector covers from both ends of the test fiber cable.
  • Step 2: Connect the fiber optic visual fault locator to one end of the fiber. Press the tester button and observe that light emanates from the other end of the fiber. This gives a simple indication of the continuity of the fiber link.
  • Step 3: Repeat with several other fibers. Check for light that can be seen leaking from a faulty splice. This may illustrate an easy way of carrying out visual fault finding on bad splices or joints.
  • Step 4: Disconnect all equipment, put the plastic covers back on the connector ends and return everything to the state it was before you started the practical, so the next group can carry out the practical in full.


What should be addressed is that during the testing process, you should never look into the output of VFL directly. After finishing the whole procedure, and remember to cover the VFL’s output with the dust cap.


Visual fault locator provides us a simple and convenient way to quickly locate faults in fiber optic cable, which is proved to be time saving and economical as well. Besides, it also alleviates the problems and pressures when dealing with massive fiber optic cabling system. Hope this article would help you get a better understanding of visual fault locator.

An Overview of Fiber Optic Connector Cleaning

A fiber optic connector works to terminate the end of an optical fiber, as the name indicates, it is generally adopted to join optical fibers where a connect or disconnect capability is required. The connector mechanically couples and aligns the cores of fibers to enable light passing from one fiber to another. Fiber optic connector is widely employed to connect equipment and cables. Besides, it also captures an essential position when cross-connect cables are required. As an indispensable component in cable installation that can affect the performance and reliability of the whole system, the cleanliness of fiber optic connector cannot be ignored. This article aims to raise the awareness of connector cleaning and offer some constructive suggestions .

Why It Is Critical to Ensure Fiber Connector Cleaning

It is important to know the fact that every fiber optic connector should be inspected and cleaned before mating, because a clean fiber optic connector is a necessary requirement for quality connections between fiber optic equipment. And One of the most basic and important procedures for the maintenance of fiber optic systems is to clean the fiber optic equipment. However, any contamination in the fiber connection can cause failure of the component itself, or even worse, failure of the whole system.

In addition, even microscopic dust particles can cause various problems for optical connections. A particle that blocks the core, either partially or completely, could generate strong back reflections, which can cause instability in the laser system. Dust particles trapped between two fiber faces can scratch the glass surfaces. Even if a particle is only situated on the cladding or the edge of the endface, it can cause an air gap or misalignment between the fiber cores which significantly degrades the optical signal. Besides dust, there still exists other kinds of contamination such as oil, human touch, film residues, vapors in the air and so on, which are proved to be more difficult to remove than dust particles. If not removed properly, they may also result in great damage to equipment.

Contaminated fiber optic connectors can often lead to degraded performance and costly, but preventable failures. So, to ensure proper performance and reliability, care must be taken with the installation and maintenance of fiber connectors. Cabling industry best practices recommend that both field and pre-terminated connections should be inspected and cleaned prior to mating to other connectors or equipment.

Common Contamination Conditions of Fiber Connector

In this part, this article intends to show several common contamination conditions of fiber connector through the following picture:

Figure 1 shows a clean single mode ceramic endface.

connector cleaning

Figure 1

Figure 2 shows a connector with dust particles spread across the surface of the endface that needs cleaning.

Connector with dust particles

Figure 2

Figure 3 shows a connector with liquid contamination that needs cleaning.

Connector with liquid contamination

Figure 3

Figure 4 shows a connector with alcohol residue that needs cleaning.

Connector with alcohol residue

Figure 4

Figure 5 shows a connector with a dry residue that needs cleaning.

Connector with dry residue

Figure 5

Figure 6 shows a connector with an oil residue that needs cleaning.

Connector with oil residue

Figure 6

The Methods of Fiber Connector Cleaning

Based on the cleaning method, generally there are four types of fiber optic cleaning kit on the market nowadays:

Dry cleaning: Optic cleaning without the use of any solvent.

Wet cleaning: Optic cleaning with a solvent. Typically IPA (isopropyl alcohol).

Non-Abrasive cleaning: Cleaning without abrasive material touching the fiber optic connector end face. Examples are air dusters or pressured solvent jet used in automated in-situ connector cleaners.

Abrasive cleaning: The popular lint free wipes, reel based fiber connector cleaners and optic cleaning swabs such as the sticks are all abrasive cleaning types.

The Process of Fiber Connector Cleaning

In this part, let’s move to describe the connector cleaning process. For general fiber optic connector cleaning, it is necessary for you to complete the following steps:

  • Step 1: Clean the fiber optic connectors with a dry cleaning technique.
  • Step 2: Inspect the connector.
  • Step 3: If the connector is dirty, repeat the dry cleaning technique and inspect the connector again.
  • Step 4: Clean the connector with a wet cleaning technique if it’s still dirty.
  • Step 5: Inspect the connector again.
  • Step 6: Repeat these steps until the connector is clean.

If you are using resealable containers, you should store the end caps in separate containers and store all of the cleaning tools as well. The inside of the containers should be clean and the lid should be kept tight to avoid contamination. Do not allow the cleaning alcohol to evaporate slowly. This may leave a residue on the cladding or fiber core. It is often difficult to clean and can be more difficult to remove than the original contaminant.


As the demand for increased bandwidth, more data and better quality audio/video grows rapidly, the use of fiber optics around the globe has increased greatly. That need for more and better data means more fiber optic cable and more high density, reliable optical connectors. It is thus nature that cleaning consideration is the number one issue in fiber optic cable technology today, with the proper method and process implemented in connector cleaning, the fiber optic connector will perform flawlessly for years in your fiber cable infrastructure. FS.COM provides cost-efficient and high-quality fiber optic cleaners that ensure you high-performed fiber connector cleaning. Supported by large quantities of products in stock, you can enjoy really fast delivery in FS.COM. For more detailed information, please visit or contact