Inspection and Cleaning Procedures for Fiber-Optic Connections CISCO (1)


It is important that every fiber connector be inspected and cleaned prior to mating. This document describes inspection and cleaning processes for fiber optic connections.

The procedures in this document describe basic inspection techniques and processes of cleaning for fiber optic cables, bulkheads, and adapters used in fiber optic connections.

Note: This document is intended for use by service personnel, field service technicians, and hardware installers.

Inspection and Cleaning are Critical

Clean fiber optic components are a requirement for quality connections between fiber optic equipment. One of the most basic and important procedures for the maintenance of fiber optic systems is to clean the fiber optic equipment.

Any contamination in the fiber connection can cause failure of the component or failure of the whole system. Even microscopic dust particles can cause a variety of problems for optical connections. A particle that partially or completely blocks the core generates 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.

  • A 1-micrometer dust particle on a single-mode core can block up to 1% of the light (a 0.05dB loss).

  • A 9-micrometer speck is still too small to see without a microscope, but it can completely block the fiber core. These contaminants can be more difficult to remove than dust particles.

By comparison, a typical human hair is 50 to 75 micrometers in diameter, as much as eight times larger. So, even though dust might not be visible, it is still present in the air and can deposit onto the connector. In addition to dust, other types of contamination must also be cleaned off the endface. Such materials include:

  • Oils, frequently from human hands

  • Film residues, condensed from vapors in the air

  • Powdery coatings, left after water or other solvents evaporate away

These contaminants can be more difficult to remove than dust particles and can also cause damage to equipment if not removed.

caution Caution: With the high powered lasers now in use for communications systems, any contaminant can be burned into the fiber endface if it blocks the core while the laser is turned on. This burn might damage the optical surface enough that it cannot be cleaned.

When you clean fiber components, always complete the steps in the procedures carefully. The goal is to eliminate any dust or contamination and to provide a clean environment for the fiber-optic connection. Remember that inspection, cleaning and re-inspection are critical steps which must be done before you make any fiber-optic connection.

General Reminders and Warnings

Review these reminders and warnings before you inspect and clean your fiber-optic connections.


  • Always turn off any laser sources before you inspect fiber connectors, optical components, or bulkheads.

  • Always make sure that the cable is disconnected at both ends or that the card or pluggable receiver is removed from the chassis.

  • Always wear the appropriate safety glasses when required in your area. Be sure that any laser safety glasses meet federal and state regulations and are matched to the lasers used within your environment.

  • Always inspect the connectors or adapters before you clean.

  • Always inspect and clean the connectors before you make a connection.

  • Always use the connector housing to plug or unplug a fiber.

  • Always keep a protective cap on unplugged fiber connectors.

  • Always store unused protective caps in a resealable container in order to prevent the possibility of the transfer of dust to the fiber. Locate the containers near the connectors for easy access.

  • Always discard used tissues and swabs properly.


  • Never use alcohol or wet cleaning without a way to ensure that it does not leave residue on the endface. It can cause damage to the equipment.

  • Never look into a fiber while the system lasers are on.

  • Never clean bulkheads or receptacle devices without a way to inspect them.

  • Never touch products without being properly grounded.

  • Never use unfiltered handheld magnifiers or focusing optics to inspect fiber connectors.

  • Never connect a fiber to a fiberscope while the system lasers are on.

  • Never touch the end face of the fiber connectors.

  • Never twist or pull forcefully on the fiber cable.

  • Never reuse any tissue, swab or cleaning cassette reel.

  • Never touch the clean area of a tissue, swab, or cleaning fabric.

  • Never touch any portion of a tissue or swab where alcohol was applied.

  • Never touch the dispensing tip of an alcohol bottle.

  • Never use alcohol around an open flame or spark; alcohol is very flammable.

Best Practices

  • Resealable containers should be used to store all cleaning tool, and store endcaps in a separate container. The inside of these containers must be kept very clean and the lid should be kept tightly closed to avoid contamination of the contents during fiber connection.

  • Never allow cleaning alcohol to evaporate slowly off the ferrule as it can leave residual material on the cladding and fiber core. This is extremely difficult to clean off without another wet cleaning and usually more difficult to remove than the original contaminant. Liquid alcohol can also remain in small crevices or cavities where it might re-emerge.

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