Cleaning Is Paramount!

Critical Cleaning of Fiber Optic Connectors

Cleaning fiber optic connectors is an important and necessary step in maintaining the integrity and functioning capability of fiber optic networks. Over 80 percent of all issues in fiber optic networks can be traced back to contaminated or damaged connectors. However, the amount of information available on cleaning fiber optics connectors can be overwhelming.

Over the years we have received damaged test equipment, tech support calls, and traces bearing significant wear and tear with one thing in common: contaminated connectors. Cleaning fiber optic connectors isn’t optional, it’s critical! While cleaning connectors may not be the most exciting topic in the industry, it is one of significant importance.

Why Is Cleaning So Important?

Contaminated or damaged connectors cause high insertion loss values which steal power from the network. Contaminated connectors also create strong back reflections which will reduce ORL values and ultimately create high Bit Error Rates. This can cause the information not to reach its intended destination.

Contaminated connectors damage test equipment and any other equipment or cable they come in contact with. Contaminated connectors also produce inaccurate test result measurements.

When Should I Clean Fiber Optic Connectors?

Connectors should always be cleaned right before they are installed. This applies to brand-new patch cables right from the factory, connectors you have previously disconnected from equipment or racks, and any connector you intend to connect to something. Do not assume the connector is clean even if you just disconnected it from an active system.


The word contamination applies to a wide variety of possible soils that create dirty connectors, eventually leading to damaged connectors. Soils that can create contamination include:

  • Dirt
  • Dust
  • Skin oil
  • Icky pic
  • Solvent residues
  • Other particles

Soils or contaminants can be broken down into two distinct groups, Ionic and Non-Ionic:

– Ionic soils include skin oil, residues, or any other soil that does not have the ability to bond with the ferrule. Ionic soils are easier to remove.

– Non-Ionic soils such as dirt, icky pic, and oily soil or hand lotions can create a bond to ferrules through charged particles or molecular adhesion. Non-Ionic soils typically require some type of cleaning solution to be completely removed.

Cleaning Techniques

One of the most important aspects of cleaning connectors is to use the proper cleaning techniques. Dry cleaning and Wet-to-dry cleaning are two basic cleaning techniques available that are very effective.

– Dry cleaning can be used for Ionic soils such as skin oil and certain Non-Ionic soils such as dust. However, dry cleaning should not be considered a superior cleaning practice; it is simply the easiest.

– Wet-to-dry cleaning is the superior option. Wet-to-dry utilizes a cleaning solution to loosen all types of contaminants. The solution and contaminants are then removed with a dry cleaning product. This technique is by far the best option for any technician, especially when a dry cleaning process leaves dust or pits. Technicians can differentiate between pits and dust easily when implementing this technique.

Note any locations on the ferrule end face where a questionable pit exists. Clean the connector using the wet-to-dry technique and inspect the connector again. If the questionable pits are gone, the issue was dust. If the pits remain, repeat the process one more time to confirm pits actually exist. Document or replace any connectors that display pits and never plug that connector into test equipment.

Products Not to Use

Connector cleaning products have become an industry all their own. With so many different options available today it can be difficult to pick the best one for your company. It is not only important to identify products that should be used, but also important to identify those that should not. Cleaning items that should not be used include:

  • Paper towels
  • Tissues
  • T-shirts
  • Any other fabrics (they leave behind lint)
  • 99% Isopropyl alcohol (While this is a common choice of cleaners, it is not ideal because of its inability to maintain its 99% purity level. 20 percent of the product ends up being water and other contaminants, failing to evaporate quickly and leaving a haze over the end of a connector. This can cause connectors to fail the OTDR test as the insertion loss is high yet the reflectance is normal.)

Inspection Zones

Inspection Zone Criteria

Inspection Zones

Several years ago the industry began to see an increase in customer-contractor disputes regarding the condition of the connector end face. At that time, the standards for cleaning were loose and required attention from standards organizations. Today the industry has a cleaning standard all contractors and customers can reference to resolve such disputes. The new IEC 61300-3-35 standard led to the concept of inspection zones with each zone having specific criteria. The standard created four zones:

  • The core
  • The cladding
  • The adhesive
  • The contact

This standard took much of the guesswork out of the inspection. Test equipment companies now sell video microscopes with software packages that can perform automated tests and generate reports.

Particle Comparison

Once possible contamination sources are identified, it is important to discuss the microscopic scale we are working with. The core of a Singlemode fiber is 9 microns. Human hair is approximately 80 microns in diameter and the naked human eye is only capable of seeing particles as small as 40 microns. A human is incapable of determining a clean connector without magnification of at least 200x.

Particle comparison can be taken one step further by investigating three categories of particles and their impact on connector mating. Different particle sizes will “react” differently when connectors are mated together.

  1. A Ten-micron particle is quite large and will hold connector end faces apart or be crushed into smaller particle sizes. Either option creates poor connector performance because true physical contact can be inhibited.
  2. Five-micron particles tend to be crushed down to smaller particle sizes which can be worse than expected.
  3. Particles smaller than five microns tend to get embedded in the end face of the connector which can create pits and scratches. These pits and scratches can cause damage to other connectors and produce inconsistent transmission performance especially when testing. Pits and scratches are permanent issues that typically require replacing connectors.

Particle Comparison

Products to Use

Now that we have established what not to use, we will address what should be used.

Wipes can be used for both wet and dry cleaning of ferrules or fiber preparation for splicing. Any wipe being used must be low lint. This will reduce the likelihood of particles being introduced to the connector from the wipe. Common low-lint wipes are available almost anywhere. Our favorite is Kimtech Kimwipes.

Cartridge Cleaners are typically used for the dry clean portion of both dry and wet-to-dry cleaning techniques. An important aspect of cartridge cleaners is the material which the cleaning cloth is made from. Polyester weaves have become very popular today as they are low lint and can be woven with other materials to produce a consistent cleaning media.

One Click Cleaners are also a useful dry cleaning option. These units use a small wand-style tip with a cleaning tape to clean through bulkhead adapters. A specialized boot on the wand tip can also be used to clean patch cables. These One Click Cleaners are very useful for cleaning test equipment as well.

Cleaning Solutions are available in a wide array of options on the market. Each manufacturer has their own proprietary formula. The most important factors for any technician to consider are:

  • How fast does the product evaporate while cleaning?
    Products that evaporate slowly tend to leave residue behind, while extremely fast evaporation means you will use more of the product to complete the project.

  • What is the shelf life of this solution?
    Certain products can diminish in purity over time because infrequent use causes air to be trapped inside the container. Lower purity solutions can react and absorb contaminants from the packaging such as low-quality metal containers.


  • Finally, does this product have shipping restrictions?
    Products with shipping restrictions can have slower delivery times along with higher delivery charges associated with Hazardous Material shipping restrictions.

Over-application of solvent cleaner dried

Regardless of which cleaning products you choose, be sure to use them sparingly. Over-application of cleaning solutions leads to incomplete evaporation. Over application of cleaners applied to the side of the ferrule can actually wick towards the connection point after inspection and connection.

A common example of over-application can be seen in the image. Note the ring of solution around the fiber. This ring is actually an outline of the contact zone.

Remember, you can clean connectors but if you don’t inspect the connector with a microscope, how will you know it is actually clean? You can’t! Always inspect after cleaning. Contact us to request a quote and get started on your next project today!