Wet vs. Dry Fiber Optic Cleaning by Harvey Stone – MicroCare Corporation

The major drawback to a “Dry” cleaning only procedure is that “Dry” cleaning puts a static charge on the connector end-face and repeated cleaning, more wipes on dry cleaning material, adds to the charge on the connector end-face. iNEMI documented this in tests that are detailed in the NFOEC 2007 paper “Accumulation of Particles Near the Core During Repetitive Fiber Connector Matings and De-matings”. The paper also stated that: “It also was shown that the [static] effect could be reduced by application of ionized air or by a cleaning fluid instead of a dry cleaning process, both methods neutralizing the electrostatic charge at the connector end face.” The solvents used in their test procedure were MicroCare’s Fiber Connector Cleaner (FCC03M) and Fiber Preparation Fluid (FPF03M).

Therefore, it is my contention that “Best Practice” should be “Wet/Dry” cleaning. By that, I mean that a lint free wipe material should be spot dampened with a static dissipative, residue free, solvent; the connector should be placed in the damp area and drawn into the dry area of the wipe. This can easily be accomplished with MicroCare’s Triton dispenser; just “flip” open the dispenser and press the wipe down on the can of solvent and you have a dampened spot. If a cartridge type cleaning devise is being used, like a Cletop, the leading edge of the wipe window can be dampened with FCC using the red straw, and connector can wiped from wet to dry. If ports need to be cleaned with cleaning sticks, the cleaning tips can easily be damped with FCC in the well on the side of the Triton dispenser. If one of newer mechanical port cleaning devices is being used, the “tip” of the cleaner can be dampened with FCC in the Triton well. In this case the first activation of the device will be a wet wipe of the connector end-face and second activation will be a dry wipe.

In addition, to the static issue with dry cleaning only, one should also consider the advantage of adding chemical action to the mechanical action and absorption of a wipe or swab. The addition of a solvent to the cleaning process will facilitate the removal of a wider variety of contaminants with less effort.

One may ask, why hasn’t the industry embraced this method sooner? The original specifications called for the use of 99.9% pure reagent grade IPA (alcohol). It turns out that this grade of alcohol is not readily available outside the laboratory. Also, IPA is hygroscopic. (It loves water.) IPA immediately starts to absorb moisture from the air as soon as it is opened. The moisture in the air contains contaminants which are also absorbed by the IPA. It is virtually impossible to keep IPA pure (that is residue free) in the fiber optic installation and maintenance environment. Several, circumstances contributed to the failure of IPA for cleaning fiber optic connectors:

    1. The specified reagent grade 99.9% pure IPA is not easily obtained.
    2. Drug Store grade IPA, used as a replacement, is not pure.
    3. IPA is not easily transportable.
      a. IPA is flammable and classified as a hazardous material.
      b. IPA cannot be shipped via air or brought on an airplane without special paperwork and fees.
    4. IPA is virtually self-contaminating once exposed to the air and leaves residue on connector end-faces.
    5. IPA is not fast drying and can stay in the slit of an adaptor alignment sleeve and weep back out across the connector end-face after inspection and mating.

The factors above contributed to the impression that the use of solvents for cleaning fiber optic connectors was not desirable. Dry cleaning became the standard method and wet cleaning was used in only the most troublesome situations. However, the science of chemistry and solvents has changed since the 1970’s when commercial fiber was first installed. There are currently available, non-hazardous, non-flammable, very fast drying, non-residue leaving solvents precisely formulated for cleaning fiber optics. The reasons for not wet/dry cleaning are no longer applicable. Today with the newer, safer, purer, static dissipative solvents it only makes sense to clean fiber optic connectors in the best manner known. The method that will clean the fastest, without leaving residue, and protect against further contamination is the Wet/Dry cleaning method.