Any professional who has done network troubleshooting knows that this is a complex process. Here are some of the most common fiber failures and the likely factors behind them, information that will help users make educated guesses about network failures.
Fiber breaks are usually due to physical extrusion or excessive bending by external forces;
Insufficient transmission power;
Long fiber laying distance may cause signal loss;
Damaged connectors may cause signal loss;
Optical fiber splices and connectors (connectors) failure may cause signal loss;
Using too many fiber optic connectors and connectors may cause signal loss;
Faulty fiber optic patchpanel or splicetra connections.
Generally speaking, if the connection is completely dead, the fiber is probably broken. But if the connection is intermittent, there may be the following reasons:
The production level of the junction is poor or the number of times of junction is too large, resulting in serious optical fiber attenuation;
Damaged connectors due to dust, fingerprints, scratches, humidity, etc.;
Transmission power is too low;
Connector error in the wiring closet.
Fiber failure
collect information
Whenever I am dispatched to a new network environment to deal with a problem, the first thing I do is gather basic information on the symptoms and possible causes of the failure. With whatever means available, the key to troubleshooting is getting valuable information by asking the right questions. Here are some questions that should be asked first.
Has anyone moved the fiber (removed, reconnected) or moved the PC recently?
It's important to find out if a PC has been disconnected or moved recently. If the fiber optic cable is disconnected from the PC, it is likely that the cable was never properly connected at all, or something went wrong when it was reconnected, or the fiber was damaged when it was disconnected.
Has the PC's hardware been modified?
Upgrading PC hardware can also cause problems. The cable may have been disconnected, or not reconnected, or connected incorrectly, or the fiber was damaged before it was reconnected. Also, it's entirely possible that the fiber wasn't disconnected during the hardware upgrade. If this is the case, it is possible that the fiber was pulled while moving the PC, or that the back of the PC case was accidentally bumped against the wall and broke the connector.
It's also possible that the fiber wasn't damaged or pulled at all, but the new hardware was preventing the NIC from working properly. The solution is to change the operating system to determine whether it is a NIC problem. Of course, if you are using Windows 9x, Me, 2000 or XP, you can use the Device Manager to check any hardware in the system to determine whether the device is working properly.
If possible, I would also recommend taking the new hardware off temporarily and going back to an earlier state of the system. This can analyze whether the problem is due to the new hardware of the system, or something else.
Has the equipment been moved recently?
I can't count how many times I've dealt with a copper network failure because someone walked too fast and moved a table that was against the wall, or a cleaner accidentally moved the table to vacuum. When moving the table without unplugging the network cable, the cable is likely to be stretched excessively, or pinched or twisted by the table. If such an action would damage a copper wire, imagine what this would do to the fiber, which is made of glass.
Has anyone (such as a phone company employee) been working on this building recently?
This may seem like an odd question, but in my experience, failures often coincide with phone company employee visits. Phone company technicians can cut cables, unplug, and do anything you can 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 or doing some other electrical work in the building yesterday, then you might be able to find a solution to the problem. entry point.
Has the fiber been stepped on, pinned under the foot of the chair, or subjected to other physical pressure?
I am amazed every time my question hits the mark and the end user admits what they did. If you ask the user how much physical stress the cable can handle in a benign way, they will usually tell you the correct answer. But keep in mind that the vast majority of users are unaware that fiber optics can break when stepped on or bent too hard and run over by chairs.
fast but imprecise test
Time is often a critical factor when dealing with a particular problem. Users need to get back to online work as soon as possible, and I also have a lot of other work to do. For this reason, I always try to diagnose the problem as quickly as possible.
There is a less scientific but very effective way to start troubleshooting. I first disconnected both ends of the fiber, and then pointed a laser pointer at a section of the fiber to see if there was light coming out of the other end, as shown in Figure A. If you don't have a laser pointer, a bright flashlight will do. Fiber optics are designed to conduct light, so you don't have to worry about aligning the light source very precisely at the cable.
If no light passes through the cable, then the fiber is indeed damaged and needs to be replaced. If light does pass through the cable, it doesn't necessarily mean the cable is working properly. This just shows that the fiber inside the cable is not completely broken. However, if the light can pass through the cable and the length of the cable is within a hundred meters, the cable will generally work well.
Other diagnostic techniques
If both the laser pointer and the flashlight can pass through the cable, it's time for further diagnostics. I tend to use exclusion when solving this type of problem.
I usually start by unplugging the optical fiber of the computer in question, and then attaching the cable to a PC or laptop that I'm sure is working fine. If the PC's networking is working then I'm pretty sure it's not a cable issue. It is possible that the NIC is damaged, or a configuration problem is preventing the computer from properly recognizing the NIC. For example, the NIC may be in conflict with other devices in the system, or a necessary DLL file may be corrupted.
If the otherwise working computer is also unable to connect to the network after connecting the cable, then the problem is either the cable or another disconnected port. Leave the normal PC connected to the cable first, then connect the other end to a port that is sure to work. If the PC network still doesn't work, then there is something wrong with the cable. On the other hand, if the PC network starts working, then the problem is with the original port.
But sometimes you can't use exclusion. For example, you don't have extra computers or extra ports, or cables span a long distance, etc., making such troubleshooting methods impossible. If this is the case, we have some other troubleshooting methods and tools.
Diagnostic tools
You may have noticed that in my list of common fiber problems, signal attenuation is a word that comes up frequently. Fortunately, there is a technique known as loss testing that can be used to measure the degree of fiber optic signal attenuation.
This technique requires connecting a light generator to a power meter. You can set the dBm range and wavelength of the signal you wish to test with the optical generator. Then connect the optical generator to the power meter, which will detect the signal and give a report on the signal attenuation. Generally, before measuring an unknown cable, you need to use a cable that has been determined to work as a reference to establish a measurement baseline. If the unknown cable is OK, its signal loss measurement should be similar to the reference cable measurement.
I can't tell you what level of signal loss would be a problem though, as it depends a lot on the cable and the physical environment. However, here are some guidelines you can refer to. Remember, these are just guidelines. Since your cable type is different from mine, your data may be very different from the data here:
The signal will have 0.5-db attenuation through each connector, the maximum attenuation is 0.75dB;
There will be 2dB attenuation of the signal passing through each fiber junction;
If single-mode fiber is used, expect an attenuation of 0.1db per 600 feet;
If using multimode fiber, expect an attenuation of 0.1db per 100 feet.
The actual test equipment you need will vary depending on the type of cables and connectors you use. Obviously, not every type of connector can be connected to a test instrument. By the same token, equipment designed to test singlemode fiber cannot be expected to test multimode fiber. There are many different fiber optic test instruments available in the market. Some test instruments can test only one type of fiber, while others can test many kinds. In my personal opinion, the network test equipment made by FlukeNetworks is the best.
Fiber Microscope
I already mentioned that contamination of the fiber is also a problem. Fiber contamination comes from dust, scratches, epoxy on the fiber connector end, and more. The best way to check for problems like fiber contamination is to use a fiber microscope.
A fiber optic microscope is a special microscope designed for viewing optical fibers. Typically fiber microscopes cost anywhere from $100 to $800.
If you're considering purchasing a fiber optic microscope, there are a few factors to consider besides price. The first point is that you should check that there is a plug so that you can easily hold the cable. Many inexpensive portable microscopes require you to hold the fiber while viewing. At high magnification, there is no need to hold the fiber and it can be thoroughly inspected through the microscope.
The next point to pay attention to is the magnification. Typically, fiber optic microscopes have magnifications ranging from 100x to 400x. The higher the magnification, the more fiber detail you can see.
Finally, hello need to check if the microscope is optical or electronic. Many high-end fiber optic microscopes actually display images on a video display without viewing through the microscope's lens barrel. Such systems can typically scale up a 3mm fiber tip to the size of a tennis ball.
A company called PriorScientific has produced a fiber-optic microscope software. This fiber optic microscope can take all subjective factors out of the inspection of the fiber. The software looks for specific details on the image provided by the microscope and then evaluates the fiber based on the image.
it may not be your fault
Like the glass from which it is made, optical fibers are indeed very fragile. You can tie the copper wire into a knot and use it, but you need to be careful and wear leather gloves when handling the fiber. Start with fiber, and you'll have all the troubles that come with it. Knowing what causes fiber problems, and what to do about them, will help solve these problems without the painful abandonment of fiber.
