Common optical fiber failures and their solutions

Any professional who has done network troubleshooting knows this is a complex process. Here are some of the most common fiber failures and possible factors for these failures, which will help users to have a base guess on network failures.

Fiber breakage is usually caused by physical extrusion or excessive bending of the external force;
Insufficient transmission power;
Optical fiber laying distance too long may cause signal loss;
damage to the connector may result in a loss of signal;
Fibre connector and connector (connectors) failures can cause signal loss;
excessive use of fiber connectors and connectors may result in loss of signal;
The optical cable tray (patchpanel) or the weld Plate (Splicetra) connection fails.

Typically, if the connection is completely disconnected, it is likely that the fiber is fractured. However, if the connection is intermittent, there may be the following reasons:
The combination of poor production level or too many times caused by the fiber attenuation is serious;
Because of dust, fingerprints, abrasions, humidity and other factors damage the connector;
The transmission power is too low;
The connector is wrong between wiring.

Gather information
　　
Whenever I am sent to a new network to deal with problems, the first thing I want to do is collect basic information about failure performance and possible causes. In any available way, the key to troubleshooting is to get valuable information by presenting the right questions. Here are some questions that should be raised first.
　　
Has anyone ever moved a fiber (removed, reconnected) or moving a PC recently?
It is important to find out if a PC has recently been disconnected or moved. If the fiber cable is disconnected from the PC, it is likely that the cable has not been properly connected at all, or that there has been a problem with the reconnection, or that the fiber has been damaged during disconnection.
　　
Has your PC's hardware been modified?
Upgrading your PC hardware can also cause problems. The cable may be disconnected, either not reconnected, or the connection is incorrect, or the fiber will be damaged before reconnecting. Similarly, it is entirely possible that the fiber has not been disconnected during hardware upgrades. If this is the case, it could be that the fiber was pulled while moving the PC, or the back of the PC chassis accidentally hit the wall and crashed the connector.
　　
It is also possible that the fiber is not damaged or pulled at all, but that the new hardware makes the NIC not working properly. The solution is to determine whether the NIC is a problem by changing the operating system. Of course, if you are using Windows9x, Me, 2000, or XP, you can use Device Manager (DeviceManager) to check the system for any hardware to determine if the device is working properly.
　　
If possible, I also recommend that you temporarily take down the new hardware and return to the early state of the system. This can analyze whether the problem is due to the new hardware of the system or other reasons.
　　
Have you moved the equipment recently?

I can't tell you how many times I've handled a copper network failure because someone was walking too fast to bring up a table that was already on the wall, or the cleaners accidentally moved the table to do the vacuuming. When you move a table without unplugging the network cable, the cable is likely to be pulled over or pressed or folded by the table. If such an action would damage a copper wire, then imagine what the consequences would be for the fiber, which is made of glass.
　　
Has anyone (such as a telephone company employee) been working in this building lately?

This seems to be a strange question, but in my experience, failures often occur at the same time as calls from employees of the telephone company. The telephone company's technicians may cut off the cables, unplug the plugs, and do anything you might think of. I'm not going to speculate on the logic behind this behavior, but if there's a problem with the network and you're told that someone was installing a phone in the building yesterday or doing other electrical work, you might be able to find a good starting point for the problem.

has the fiber been trampled, pressed at the foot of the Chair, or subjected to other physical oppression?

I would be amazed when my questions hit the point and the end user confessed what they were doing. If you're using a kindly way to ask how much force a user's cable can withstand, they usually tell you the right answer. But remember, the vast majority of users are not sure that the fiber will break if it is being trampled or bent too hard and crushed by a chair.

Fast But imprecise tests

when dealing with a particular problem, time is usually a key factor. Users need to get back online as quickly as possible, and I'll have a lot of other work to do. For this reason, I always diagnose the problem as quickly as possible.

has a less scientific but very effective way to start troubleshooting. I first disconnect the ends of the fiber and then point a laser beam at the fiber section to see if there is light on the other end, as shown in Figure A. If you don't have a laser pointing device, a bright flashlight can also be, as shown in Figure B. The optical fiber is designed to conduct light, so you don't have to worry about the need to align the light source very precisely to the cable.

If there is no light passing through the cable, the fiber is indeed damaged and needs to be replaced. If the light does go through the wire, it does not necessarily indicate that the cable works. This only means that the fiber inside the cable is not completely fractured. However, if the light can be passed through the cable and cable other diagnostic techniques

If the light from the laser pointing device and flashlight can go through the wire, it's time to further diagnose. In solving such problems, I tend to use the exclusion method.

I usually start by unplugging the computer fiber plug with the problem, and then I pick up a PC or laptop computer that I know is working properly on the line. If the PC's network function works, then I can be sure it's not a cable problem. It is possible that the NIC is damaged or that a configuration problem has prevented the computer from correctly identifying the NIC. For example, the NIC may conflict with other devices in the system, or the required DLL file is corrupted.

If this originally working computer does not have access to the network after connecting the cables, the problem is either on the wire or on another disconnected port. Let the normal PC keep a connection to the cable, and then connect the other end to a port that is sure to work properly. If the PC network still fails to connect, then the cable does have a problem. On the other hand, if the PC network starts to work, then the problem is on the original port.

But sometimes you can't use exclusions. For example, you don't have an extra computer or extra port, or a cable that spans a long distance, and so on, makes such a method of troubleshooting impossible. If this is the case, we have other methods and tools for troubleshooting.

Diagnostic Tool

Maybe you noticed that in my list of common fiber problems, signal attenuation is a word that appears frequently. Fortunately, there is a technique for signal attenuation detection (losstesting) that can be used to measure the degree of attenuation of fiber signals.

This technique requires a light generator to be attached to a power meter. You can set the signal dbm range and wavelength that you want to test with the light generator. Then the light generator is connected to the power meter, and the power meter detects the signal and gives the report of the signal attenuation. In general, before you measure an unknown cable, you need to use a cable that has been identified to work properly as a reference to establish a measurement baseline. If the unknown cable is not a problem, then its signal loss measurement data should be similar to the reference cable measurement values.

But I can't tell you what level of signal loss can cause problems because it depends largely on the cabling and the physical environment. However, here are some guidelines you can refer to. Keep in mind that these are just guidance points. Because your cable type differs from mine, your data may differ significantly from the data here: the

Signal will have a 0.5-db attenuation through each connector, with a maximum attenuation of 0.75dB;
　　The signal will have 2dB attenuation through each optical fiber binding;
If single mode fiber is used, 0.1db is expected to decay every 600 feet;
If multimode fiber is used, 0.1db is expected to decay every 100 feet.

The actual test equipment you need varies according to the type of cable and connector you use. Obviously, not every connector can be connected to a test device. Similarly, a device designed to test single-mode fibers cannot be expected to test multimode fibers. Many different optical fiber testing instruments can be seen on the market. Some test instruments can only test one kind of fiber, while others can test many kinds. In my personal opinion, the network test equipment produced by Flukenetworks is the best.

Fiber Optic microscope

I've mentioned that fiber contamination is also a problem. The fiber is contaminated by dust, abrasions, epoxy resins at the end of the fiber connector, and so on. The best way to check for problems such as fiber optic contamination is to use a fiber optic microscope. The

Fiber microscope is a special microscope designed for viewing optical fibers. Usually the price of fiber microscopes ranges from 100 dollars to 800 dollars.

If you are considering buying a fiber optic microscope, there are some factors to consider besides the price. The 1th is that you should check whether there is a plug, so that you can easily hold the cable. Many inexpensive portable microscopes require you to hold the fiber in your observation. In the case of high magnification, there is no need to hold the optical fiber, through the microscope can be thoroughly examined. The next thing you need to notice about

is magnification. Generally speaking, the magnification range of the fiber microscope is 100 times times to 400 times times. The higher the magnification, the more fiber details you can see.

Finally, you need to check whether the microscope is optical or electronic. Many high-end fiber microscopes actually display images on a video display without having to look through a microscope lens tube. Such a system can usually enlarge the 3mm fiber end to a tennis ball size.

A Fame priorscientific company has produced a fiber-optic microscope software. This fiber-optic microscope can be used to check the optical fiber to exclude all subjective factors. The software looks for specific details in the image provided by the microscope, and then evaluates the fiber based on the image.

or it may not be your fault.

The

, like the glass it makes, is indeed very fragile. You can tie the copper wire to a knot and then use it, but you need to be careful with the epithelial gloves when dealing with the fiber. Starting with the use of optical fiber, you will encounter all sorts of problems that come along. Understanding the causes of optical problems and the corresponding countermeasures will help solve these problems without the painful abandonment of the use of optical fibres.