The Optimal Cleaning Process for Fiber Optic Connectors

Why Clean Fiber Optic End-Faces?

Dirty connectors are the single most common reason for fiber optic network failures. Probably the most important items in a Fiber Optic Technician’s tool kit are the cleaning supplies, because nearly 50% of the failures he will encounter can be remedied with proper cleaning.

How Does Contamination Cause Network Problems?

First, if contamination blocks or partially blocks the light path then less light can pass through the connection. This decrease in light amounts to a decrease in signal strength, which may result in data errors.

The second way that contamination can cause a problem is if the contamination keeps the connector end faces from physically contacting one another. If this happens the Return Loss (RL) or “Back Reflection” increases which can have a devastating impact on the network.

How Does a Connector Become Contaminated?

In most cases, mated fiber optic connectors are not likely to become contaminated unless there is a clearly destructive event like a fire, flood or earthquake. Therefore, most connector end faces become contaminated when they are left un-mated (exposed) or handled by humans during deployment, testing or rerouting.

When Must Connectors Be Cleaned?

Every connector end-face that touches the network must be cleaned each time it is attached. Also, every port into which a connector is placed must be cleaned properly. This includes, test equipment and associated devices such as test jumpers, fiber boxes and attenuators as well as installation of new jumpers.

A Close Look at the Cleaning Process

Whether cleaning dishes, cars, windows or floors, the procedures are similar. For example, dishes. Remove any remaining food (now considered contamination) from the plate, wash the plate with detergent and a sponge, rinse the plate with hot water and then dry it with a clean dry towel. What really happens during those four steps?

Consider washing a car. Wet the car to rinse off large contaminates that might mar the surface. Take soapy water (the solvent) and apply it to the surface of the car with a “clean” sponge or soft rag. The wiping with the sponge or rag applies mechanical action to loosen the contamination from the surface.

Actually, much of the dirt is left in suspension in the soapy water on the surface of the car. That is why rinsing the soapy water off right away is important – so that contaminants, dirt, will not be re-deposited on the car.  This rinse allows the loose contaminants to wash away. Then dry the car with a clean towel or chamois so that contaminants in the rinse water are not left on the surface. “Water spots” from dissolved minerals or other contaminants can spoil the appearance of the car.

What are the similarities in these cleaning processes?
  • Gross cleaning to remove large contaminants.
  • Use of solvents/soaps combined with mechanical action to clean the surface.
  • Removal of the contaminants from the area (the rinse).
  • Purity of the rinse and the ability of materials to absorb solvents and contaminants (chamois or towels).
A Quick Look at Familiar Cleaning Processes:
Car Dishes Windows Floors Spill on floor
1 Gross contamination removal Wet with water from hose wet/rinse with water Usually N/A except to remove cobwebs. Sweep Remove glass
2 Loosen contamination Wash with soap and sponge Wash with soap and water with sponge Spray on solvent, wash with paper towel Wash with mop and soapy water. Use towel to absorb
3 Remove
loosened contamination

with water from hose

Rinse with clean water Wipe with solvent damp paper towel Rinse with mop and clean water Use towel to absorb
4 Assure no contamination left on surface Dry with chamois Dry with clean towel Wipe with clean dry paper towel Wipe with damp mop and leave to dry Use clean towel to wipe dry
 What Happens During the Cleaning Processes:
1 Gross contamination removal Usually some form of mechanical action (moving air, moving water, brushing or wiping)
2 Loosen contamination Chemical action of solvent combined with mechanical action of a wipe used together, or just the mechanical action of a wipe
3 Remove loosened contamination Flush contamination with pure solvent rinse or use an absorbent wipe to remove contamination
4 Assure no contamination left on surface Use a clean absorbent wipe to remove any remaining contamination on the surface

Essentially, ideal cleaning results are dependent on mechanical action and chemical action to loosen the contamination. It also depends on the availability of a pure rinsing fluid to flush the contaminant away and a clean highly absorbent material to remove the contaminants from the surface to be cleaned.

Cleaning Fiber Optic Connectors

Now apply the above to cleaning fiber optic connectors. Remember, the end-face of the connector is typically ceramic and glass, which have been highly polished. Therefore, it is not likely that contaminants would penetrate the surface. However, ceramic and glass are excellent electrical insulators and can therefore hold an electric charge that can attract and hold very small particulate. And since there is concern about micron-sized contaminants, take the ionic bonds into consideration.

Also, consider the constraints under which the connector end-face is cleaned. It is certainly easier to clean an exposed connector end-face on the end of a patch cord than to clean an end-face hidden within an alignment sleeve. Wipe the connector end-face of a jumper with a lint free wipe repeatedly and if it does not become clean, dampen the wipe with solvent and continue the process.

However, when cleaning an end-face within an alignment sleeve, the ability to wipe is severely limited. Typically it is limited to the surface area at the end of a swab (which becomes very small with a small form factor connectors such as LC’s or MU’s). Therefore it is important to maximize the mechanical action and absorbency of the swab end-face.

The Optimal Cleaning Process for Fiber Optic Connectors

Let’s first look at cleaning exposed connector end-faces. Experience shows that wiping the connector end-face with a “lint free” absorbent material typically removes most surface contaminants. The material should be backed with a resilient pad (much like the palm of your hand) so that the material conforms to the end-face geometry and the end-face will not be damaged by any harsh contaminate on a hard surface. In cases where the wiping alone does not sufficiently clean, add solvent to the wipe. In this way both chemical and mechanical action is applied to the cleaning. However, the solvent used must be pure, and not leave a residue. The solvent should also be electrically conductive so that it can dissipate any electrical charge that may be ”holding” particulate on the end-face surface.

Cleaning Inside an Alignment Sleeve

Now consider a connector end-face or lens within an alignment sleeve. The ability to wipe is very limited. It is virtually impossible to provide the absorption and mechanical action applied to an exposed connector. One would have to use numerable swabs to achieve the surface area of one wipe of an exposed connector on a lint free wipe. Therefore, the careful choice of a clean lint free, highly absorbent cleaning tip that provides good mechanical action and conforms to the end-face geometry is necessary.

Also, the addition of chemical action (solvents) is advised. With the proper solvent, less mechanical action is required. However, the purity, absorbency and cleaning properties of the cleaning stick as well as the purity, volatility and cleaning properties of the solvent become key factors in selecting a cleaning process. To clean a connector end-face within an alignment sleeve, the solvent must be very pure and highly volatile and the cleaning tip must be clean lint-free, highly absorbent, provide excellent mechanical action and conform to the end-face.

Cleaning Fiber Optic Connector End-Faces:
Exposed connector end- faces Connector end-faces within alignment sleeves
1 Gross contamination removal Usually some mechanical action (blowing air, spraying water, etc) N/A Canned air
2 Loosen contamination Mechanical and/or chemical action: Wiping or solvent or both Wipe with an
absorbent lint
free material
Wipe with an absorbent lint free cleaning tip with solvent
3 Remove loosened contamination Absorption of contamination with a material Wipe with an
absorbent lint
free material
Wipe with an absorbent lint free cleaning tip with solvent
4 Assure no contamination left on surface Wipe with lint free absorbent material, rinse with ultra pure solvent Wipe with an
absorbent lint
free material
Wipe with an absorbent lint free cleaning tip with solvent
Choice of Cleaning Materials

The first rule of cleaning materials is to do no harm. Wipes or swabs should be clean and non-abrasive so that they cannot damage the end-face of connectors. Likewise, solvents must be materials compatible so that surrounding components will not be damaged. Now let’s take a closer look at wipes swabs and solvents.

Choice of Wipes:

Carefully consider what material to choose for wiping the exposed connector end-faces. The material should be clean and lint free. A tee shirt does not fill this requirement. Remember, these are micron-sized contaminants requiring 200x magnification to view. Therefore, the wipe must be really clean, lint free and absorbent. The wipe provides mechanical action to loosen the contamination and also allows absorption to remove the contaminants from the surface.

Also be careful about the wipe location. Wipe on a resilient surface so that the wipe conforms to the end-face geometry of the connector and so that any hard contaminate that may be lodged behind the wipe will not protrude through the wipe and scratch the end-face permanently damaging it.

Choice of Swabs:

Swabs are typically used to clean connector end-faces within alignment sleeves. Like wipes, the cleaning tips must be clean, lint free, and highly absorbent in order to absorb as much contamination as possible. Also, since swabs are frequently used with solvents, the construction materials of the cleaning stick must be compatible with the solvent. One would not want the glue used to attach material to a swab dissolved by the solvent and left on the end-face of the connector.

Choice of Solvents:

When cleaning fiber optic connector end-faces with a solvent there are several issues that must be in mind. First, the solvent should not contain any water, detergents or surfactants. These materials leave residues on the surface. The ideal solvent is fast drying, leaves no residue, dissolves oils and water-soluble oils, and is conductive to dissipate ionic bonds. It should also have excellent materials compatibility so that it will not attack surrounding components. The drying speed (volatility) of the solvent is particularly important. A slow-drying solvent wicks within the slit of the alignment sleeve and other mating surfaces only to weep back out later (up to several minutes later) and wet the connector end-face.

IPA – Why Use It?

There are many disadvantages to using IPA to clean fiber optic connectors. Many older specifications recommend reagent grade IPA. Reagent IPA is 99% pure IPA. This grade of alcohol is not readily available. Most drug stores sell rubbing alcohol which is only about 60% IPA. Some higher grades range up to 91% IPA. The real problem with IPA as a cleaner is that it is infinitely hygroscopic. That is, IPA infinitely absorbs water from the surrounding air until it completely dilutes itself.

Therefore, it is next to impossible to keep IPA pure. As soon as the technician opens the bottle, the IPA begins to dilute. The issue with this dilution process is that the water it absorbs from the air has contaminants dissolved in it. These contaminants end up on the connector end face after cleaning. IPA leaves a “haze” on the end-face of a connector that can become literally “baked” onto the glass by high-powered lasers in long-haul systems if not wiped away immediately. Each subsequent cleaning adds to the “haze” and increases insertion loss for the system. This haze is only removed by re-polishing the connector end-face. Also, when cleaning within alignment sleeves, IPA does not dry fast and will likely re-contaminate a cleaned connector.

Consider Cleaning Fluid Safety

Another problem with IPA is that it is flammable and considered hazardous material. It cannot legally be transported without special manifests and HAZMAT markings. Therefore, in many cases the technician cannot take the cleaner with them to the job site. Also there are increased liabilities carrying flammable liquids for any employee; something every employer must consider.

Furthermore, IPA is a 100% Volatile Organic Compound (VOC). Most environmental groups are attempting to reduce the emissions of VOCs into the atmosphere. VOCs  contribute in the formation of low-level (ground level) ozone and smog, which contributes to human health risks.

There are fiber optic cleaning fluids which address these issues for cleaning connector end-faces. Chemically, they are HFCs (Hydroflourocarbons) and HFEs (Hydroflouroethers). These fluids are fast drying, non-flammable, and not highly hygroscopic, like IPA.

Sticklers Products Get the Job Done

MicroCare Corporation has developed a line of cleaning products for fiber optics industry. These Sticklers™ products address the cleaning problems of both exposed connector end-faces and those within alignment sleeves.

The Products:

Sticklers™ Fiber Optic Splice & Connector Cleaner is a very fast drying fluid that dries without a residue.  This speeds up cleaning time. It is perfect for cleaning within alignment sleeves. It is an excellent cleaner and has exceptional material compatibility. This product is non-flammable, non-hazardous, non-regulated.

CleanStixx™ Connector Cleaning Sticks feature a high purity, sintered polymer material providing a clean fibrous, lint free, highly absorbent cleaning surface. These products come in various sizes for virtually any fiber optic connector. There are no binders or glues used in these cleaning sticks. When dampened with a cleaning fluid, the cleaning tip’s capillary action draws the contamination from the end-face into the stick tip.

Sticklers CleanWipes are highly absorbent lint free wipes ideal for cleaning exposed connector end-faces. The small, 2″ x 4″ wipes come in a box to keep them clean and ready for use.

Some Things to Remember:
  • Every connector end-face that touches the network must be cleaned each time it is attached.
  • Every port into which a connector is placed must be cleaned. This includes, test equipment, and associated devices such as test jumpers and fiber boxes.
  • Ideal cleaning results depend on mechanical action and chemical action to loosen the contamination. In addition, the availability of a pure rinsing fluid to   flush the contaminant away and a clean highly absorbent material to remove the contaminants from the surface to be cleaned is important.
  • Cleaning materials must do no harm.
  •  Fiber optic cleaning materials must be clean, lint free and highly absorbent.
  •  IPA is not the best cleaner.
  •  Very fast drying cleaning fluids are necessary for cleaning connector end-faces within alignment sleeves.
  •  Always check the material compatibility of fiber optic cleaning fluids.