Cleaning the Connector of an Optical Fiber

This topic describes how to clean the connector of an optical fiber. Frequent insertion and removal or not taking dustproof treatment for a long time causes the connector to be unclean and deteriorated, which compromises the quality of the line. Therefore, you need to take measures to prevent dust and periodically clean optical fiber connectors, including the connector endface of an optical fiber, optical port of an optical module, and fiber adapter.

Prerequisites

Prepare the cleaning tools before cleaning, and follow the instructions in "Precautions".

Context

A large number of optical fiber connectors are used in optical transmission, which are easy to be contaminated in OM. The dust particles that can be seen by a microscope affect the quality of optical signals. As a result, the system performance deteriorates and network stability is affected. For two connected optical components, dust particles may damage the surface of the optical fiber. If the cladding or edge of an optical fiber has dust particles, the cores of two connected optical fibers may not be exactly aligned. As a result, the quality of optical signals is affected.

A 1 μm dust particle on a single-mode optical fiber blocks 1% optical signals and therefore leads to 0.05 dB attenuation loss. A 9 μm dust particle is hard to be seen without a microscope but it completely blocks the core of an optical fiber. Therefore, even an extremely small contaminant that can only be found by an instrument such as a microscope may block the connector of an optical fiber. Besides dust particles, the following contaminants need to be cleaned away:

Grease (usually brought by hands)
Condensation residues
Powder (evaporation residues of water or solvent)

Such contaminants will also damage optical components and are more difficult to clean away than dust particles. To clean optical components, you must follow the corresponding steps.

Tools and Materials

The following lists commonly used cleaning tools and materials:

Optical power meter: used for testing whether the laser on the connector of an optical fiber is disabled.
Lint-free wipe: a piece of long silk cotton specially used for cleaning the connector endfaces of an optical fiber.
Lint-free swab: used for cleaning the optical port of an optical module, and a fiber adapter. It has two specifications: ф2.5 mm and ф1.25 mm. You can select one according to the port type (use the lint-free swab with ф2.5 mm for the ports of SC and FC types, and use that with ф1.25 mm for the ports of LC and MTRJ types).
Protective cap: used on the connector of an optical fiber, optical port of an optical module, and fiber adapter.
Cleaning tool box: used for placing lint-free wipes and protective caps. Place lint-free wipes and protective caps separately from other tools.
Cleaning reagent (alcohol): used for cleaning the connector of an optical fiber. It is flammable and therefore must be safely stored and kept clean.
Optical fiber endface magnifier: a microscope (400^*) used for checking whether the connector endface of an optical fiber is clean and smooth.

Impact on the System

An optical module must be powered off before its port is cleaned. In this case, services carried on the optical port will be interrupted.

Precautions

DANGER:

Never look into the optical port or the connector of an optical fiber without eye protection. Never put an optical port towards the flammables.
Never clean an optical fiber connector when the laser is on.
ESD discharge damages the equipment. To remove or insert a pluggable optical module before or after cleaning, wear an ESD wrist strap or ESD gloves.

Put a protective cap into the cleaning tool box immediately after taking it off. Place unused protective caps in the cleaning tool box, or in the ESD bag for sealed storage. Clean protective caps quarterly (it is recommended to clean them by using an ultrasonic cleaner).
Keep your hands clean and dry before cutting a lint-free wipe, and place unused lint-free wipes in the clean ESD bag or the cleaning tool box for sealed storage.
After the cleaning, cover the connector of the optical fiber, optical module, and fiber adapter that will not be immediately used with protective caps.

Procedure

Clean the connector endface of an optical fiber.
1. Power off the laser of the connector before cleaning. Disconnect the optical fiber (at both ends) to be cleaned.
2. Use the optical power meter to test the optical power and ensure that no optical signals are sent from the connector of the optical fiber.
3. Clip a piece of lint-free wipe into 32 small pieces of the same size.
4. Use a dry lint-free wipe (two-layer) to wipe the connector endface of the optical fiber along one direction once. For a seriously contaminated connector, use a lint-free wipe (two-layer) dipped with a little cleaning reagent to wipe the connector endface of the optical fiber along one direction once, and then use a dry lint-free wipe (two-layer) to wipe it along one direction once again for ensuring that the connector endface is dry
  NOTE:
  - A lint-free wipe can be used only once. Use the portion of the lint-free wipe that is not touched by your hands.
  - You can use the optical fiber end magnifier to check the cleaning and abrasion condition of an optical fiber connector.
5. After the cleaning, do not touch the connector. Connect the optical fiber (at both ends) immediately. Cover the optical connectors that will not be immediately used with protective caps.
6. Power on the laser.
Clean the optical port of an optical module.
1. Power off the laser of the optical module before cleaning. Disconnect the optical fiber (at both ends) from the optical module.
2. Use the optical power meter to test the optical power and ensure that no optical signals are sent from the port of the optical module.
3. Wear an ESD wrist strap or ESD gloves to remove a pluggable optical module.
4. Select lint-free swabs with a suitable diameter according to the type of the optical port. Dip a swab with the cleaning reagent, insert the swab into the inside of the optical port, and then clean it by rotating the swab 360 degrees in one direction along the inner wall of the optical port.
  
  NOTE:
  The lint-free swab with ф2.5 mm is used for the ports of SC and FC types and that with ф1.25 mm is used for the ports of LC and MTRJ types.
5. Insert a dry swab of the same type into the inside of the optical port and clean it by rotating the swab 360 degrees in one direction along the inner wall of the optical port.
6. After the cleaning, connect the optical fiber (at both ends). Cover the ports of the optical modules that will not be immediately used with protective caps. Wear an ESD wrist strap or ESD gloves to insert a pluggable optical module.
7. Power on the laser.
Clean a fiber adapter.
1. Power off the laser of the optical port before cleaning. Disconnect the optical fiber (at both ends) from the fiber adapter.
2. Use the optical power meter to test the optical power and ensure that no optical signals are sent from the connector of the fiber adapter.
3. Select lint-free swabs with a suitable diameter according to the type of the fiber adapter. Dip a swab with the cleaning reagent, insert the swab into the socket inside the fiber adapter, and then clean it by rotating the swab 360 degrees in one direction along the inner wall of the fiber adapter.
  
  NOTE:
  The lint-free swab with ф2.5 mm is used for the ports of SC and FC types and that with ф1.25 mm is used for the ports of LC and MTRJ types.
4. Insert a dry swab of the same type into the socket inside the fiber adapter and clean it by rotating the swab 360 degrees in one direction along the inner wall of the fiber adapter.
  
  NOTE:
  Use an ultrasonic cleaner to clean fiber adapters when there are a large quantity of them.
5. After the cleaning, connect the optical fiber (at both ends). Cover the fiber adapters that will not be immediately used with protective caps.
6. Power on the laser.

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