You need your fiber optics to perform reliably, so you have to make sure they stay clean and well-maintained. You also need to take extreme care when handling them to ensure they don’t get damaged. In this guide, we’ll discuss how you can keep fiber optic cables, connectors and optical transceivers clean and in good condition without causing any damage.
When to Clean Fiber Optics
You need to know which tools and processes to use for optical fiber cleaning, but it’s just as important — if not more important — to know when to use them.
It’s most important to clean fiber optics before installation. A new cable doesn’t guarantee a clean cable, and the installation process can introduce dust and other contaminants. Always clean the end of a fiber optic cable before you plug it into a connector.
After installation, you don’t need to perform regular preventative maintenance and cleaning. In fact, you should avoid it, as it can introduce contaminants.
Fiber systems are designed to be installed and then left alone unless they become damaged. If your system does get damaged, make sure you clean the cables and connectors after fixing the problem and before reconnecting them.
Although fiber systems are designed not to need regular maintenance, sometimes problems still occur. When they do, try cleaning your fiber optic cables and connectors and optical transceivers.
Reasons Not to Perform Regular Preventative Maintenance for Optics
While you may sometimes need to perform work on your fiber optic system, it’s not necessary to regularly perform maintenance checks, such as microscopic inspection of connectors and adaptors, insertion loss testing and optical time-domain reflectometer (OTDR) testing while the system is operating normally. In fact, there are several reasons why performing maintenance work, beyond necessary repairs and cleaning, can be detrimental.
Many of the components of fiber optic systems are fragile, and an accidental drop or impact can cause significant damage. It’s also easy to get contaminants, such as dust and dirt, into mating adaptors and connectors when they are exposed to air. Oil from your fingers can trap dust, in addition to causing issues of its own, which can result in scratches to the fiber connector and the optic it’s connected to.
Removing and inserting fibers can also cause a small static charge on each end, which attracts airborne particles. Fiber caps can also collect dirt, dust and other contaminants, so the ends of the fibers should be cleaned before reinserting them into an interface. Because of these risks, it’s best to avoid touching fiber optic components and leave them protected unless it’s necessary.
Mating and unmating connectors is necessary for many cleaning and maintenance tasks and can eventually wear the connector interfaces, leading to diminished performance. The fiber link loss may also change after reassembling a link, especially for connectors with spring-loaded ferrules. This change in loss could potentially cause issues on networks where loss margins are low.
If there is a problem with dust in the fiber system, cleaning the system is usually a short-term fix that comes with risks. In most cases, fixing issues related to air conditioning, air filtration and sealing is a more effective, thorough solution.
Working with fiber optics also comes with safety risks. Many systems use relatively high-powered lasers, which can damage the eyes. Using a high-powered microscope concentrates this light, increasing the risk of injury. Many of the lasers used are at the top end of human eye sensitivity, so only some people can see them — this means you may be looking into a laser without realizing it.
Equipment should be powered off when it’s being cleaned or inspected. In addition, most inspections require taking the network offline. It isn’t necessary to cause this potentially costly disruption to conduct inspections on a regular basis.
Maintaining fiber optics and optical transceivers means keeping them clean and in good condition, but also leaving them alone as much as possible. Because performing maintenance work on fiber optic systems comes with so many risks and can introduce contaminants, it’s best to avoid it if possible. If you do need to perform any maintenance or repairs, be sure to clean the equipment carefully before placing it back in service.
How to Ensure Reliability When Installing
One of the best ways to keep your fiber optics in good condition is to install them in a way that keeps them reliable. When burying the cable plant, bury it deep enough to reduce the chance of it from being dug up. If it is exposed, put it in the innerduct or conduit.
The Fiber Optic Association (FOA) offers some tips for ensuring cables are installed properly and in a way that won’t lead to damage — these include:
- Follow guidelines for pulling tension and bend radius.
- Avoid bundling patch cords too tightly.
- Avoid letting long cables hang on connectors.
- Check fibers in splice closures to make sure they aren’t stressed.
- Support vertical cables about every meter.
- Only use operating cables in environments within their specifications.
- Ensure all cables meet their loss budgets.
Directly after installing regular fiber, you can use a high-resolution optical time-domain reflectometer (OTDR) to reveal signs of stress. For bend-insensitive fiber, conduct a thorough physical inspection.
When installing a fiber system, carefully inspect and clean every connector, adapter and transceiver port. Clean them multiple times until you are sure any contamination is removed. Make sure you keep protective caps on every connector, adapter and port to prevent further accumulation of dirt and other contaminants, as well as physical damage.
Be sure to use patch panels and racks with lockable doors. This helps keep dirt out and prevents unauthorized personnel from messing with the equipment.
Problems That May Necessitate Cleaning
Tiny deposits of oil, dust particles, dirt and other contaminants can reduce the effectiveness of fiber optic systems and even lead to failure. Fiber caps can also collect dirt, dust and other contaminants, so the ends of the fibers should be cleaned before reinserting them into an interface. Contaminants on fiber optic cable surfaces can cause degraded signal power or loss of light, which can lead to intermittent optical connection issues.
Over time, laser power density can burn any contaminants that are present into optical surfaces, which can cause the fiber to produce inaccurate results. Contaminated cable connectors can also transfer contaminants into the optical sub-assembly barrels of the optical module into which they are inserted.
There are various safety precautions you should take when cleaning fiber connectors. Be sure to follow all instructions and safety measures in your optical device manuals and those of any tools or chemicals you use during the cleaning process in addition to these general precautions:
- Do not look into the end of an optical interface when it is operating, as laser radiation is harmful to the eyes.
- Do not take the covers off transceivers while they are operating.
- Make sure that the unit power is off during the cleaning process.
- Disable other power and light sources before cleaning optical interfaces.
- Do not make unauthorized alterations to optical devices.
Tools to Use
Some of the tools you can use for fiber optic cleaning include:
- Compressed air: Filtered or canned compressed air can help remove contaminants, but it must be Clean Dry Air (CDA) that is free of water, oil, dust and other particles.
- Lens paper: Long-fiber, low-ash lens paper with no chemical additives can be useful for wiping away contaminants.
- Isopropyl alcohol or methanol: You can use isopropyl alcohol or methanol for cleaning, but be sure to follow the manufacturer’s product guidelines and be extremely careful when using chemicals for cleaning.
- Reel cleaners: Reel cleaners use a reel of lint-free cloth that moves as you clean and is refillable, so the cloth used is always free of contaminants. Various types of reel cleaners made for different types of connectors are available.
- Cleaning pens: Various types of cleaning pens, such as the T-ORCH CLEP-125P cleaner, for different types of connectors are also available. These tools are designed to clean fiber optic connectors without causing smudges or scratches.
- Other cleaning tools: You can also find numerous other variations of reel cleaners and cleaning pens designed specifically for fiber optics.
How to Clean Fiber Optic Cables
Some general fiber optic cable cleaning tips include:
- Do not let the end of the cable touch your fingers or any surface.
- Be careful not to bend the fiber cable. This can cause internal breakage and poor performance or instability.
- Wear powder-free gloves or finger cots when handling fiber optic cables to avoid scratching, chipping or contaminating them.
- Only use fresh spectroscopic-grade isopropyl alcohol or methanol as a cleaning solvent.
- Turn the module power off and disable other light sources before beginning the cleaning process.
You can use any of several methods to clean fiber optic cables. Below is one cleaning procedure you can use:
- Blow the surface of the fiber using CDA to dislodge any larger, loose particles.
- Place a few drops of an appropriate cleaning solution, such as spectroscopic-grade isopropyl alcohol or methanol, in the middle of a lens tissue.
- Gently grasp the fiber by the cable or connector. Put the wet section of the tissue on the optical surface and slowly move it across the fiber.
- Under high-intensity light, use a magnifier, video inspection tool or optical loop to examine the fiber surface. If you see any contaminants or streaks, repeat the process with a new lens tissue.
- As soon as you finish the cleaning process, place a protective cover on the end of the cable or reinsert the fiber for use to prevent recontamination.
To avoid damage during cleaning, be extremely careful throughout the process, and follow the tips below:
- Don’t tip the CDA can while blowing, as this can cause the release of liquid, which will contaminate the fiber surface.
- Never use dry lens paper, as it is highly abrasive.
- Never use acetone as a cleaner for fiber optic surfaces.
- Don’t insert the lens tissue into the methanol or isopropyl alcohol, as this can contaminate the liquid. Instead, drip the cleaning solution onto the tissue.
As an alternative, you can use optical cable cleaning kits or tools. Follow the instructions that come with these tools to ensure you use them properly.
How to Clean Optical Transceivers
The ideal method for cleaning a transceiver port is to use a CDA stream to blow away particles. Follow these tips to ensure safe, effective cleaning of optical transceivers using compressed air.
- Handle optical modules only in electrostatic discharge (ESD) safe areas and follow ESD safety precautions.
- Turn the module power off before cleaning.
- Only use CDA or approved canned compressed air.
- Keep the compressed air can upright, as tipping can result in liquids in the air stream, which will cause contamination.
- Be careful not to touch the module’s inner surfaces, including the optical subassemblies.
- Don’t insert any foreign objects into the ports.
- Powder-free gloves or finger cots are not required, but do help ensure cleanliness.
Use the following procedure to clean optical transceivers:
- Blow the inner barrel of the receiver optical subassemblies and transmitter with CDA to remove any loose particles.
- Use a microscope to inspect the surface of the optical subassembly lens under high-intensity light or verify the optical signal and eye pattern quality. If you detect any contaminants, repeat the cleaning process.
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