Considerations for deployment and testing of optical fibres

On the one hand, the performance of the network of enterprises more and more high, on the other hand, the cost of fiber also more and more It is now becoming more common to achieve high bandwidth through optical fibers, such as connecting between the two offices through fiber optics, previously connected directly through a wire. Fiber optics for enterprises may not be luxuries, but necessities.





Although the light can provide a lot of bandwidth, but if deployed improperly, its performance will be compromised. To this end, for the need for light brazing Enterprises, the author has the following recommendations.





as far as possible to avoid the macro and micro-curved





the same as the normal cable, there will be a signal decay. Network cable is mainly due to distance caused by the loss of signal, and for optical fiber, it is mainly due to improper installation. If the fiber is stretched or bent too much, it may cause the core to crack, there will be small cracks. One consequence of this is that light will scatter, causing the signal to decay. In addition, if the fiber bending angle is too large, it will change the optical fiber contact to the core-cladding junction of the angle of incidence. This causes the incident angle to be less than the critical angle of the full reflection angle. Notice that at the bend, some of the light signals are not reflected, but are refracted into the cover and lost directly. Reflection, refraction, these professional terms may be difficult for readers to understand. Simply put, the network administrator in the deployment of optical fiber, the need to avoid the following two kinds of circumstances.





is a macro song. Macro area generally refers to the visible bending of the naked eye. The optical fiber gently pull the value, you can see the fiber has a broken down, it seems to be heavy weight pressure. When the administrator bends the optical fiber, part of the light exceeds the critical angle, causing the light to leak out of the core, into the cover layer. In general, once the light has entered the cover, it is difficult to return to the core again (even if it can be too expensive to give up). Usually it is leaked directly through the buffer layer.





second is the micro-song. The micro-curvature and the macro-curvature in the reason is more consistent, will lead to the light signal over the critical angle and leakage of fiber core. But in the outward manifestation, is different. If you are a macro, you can usually judge whether you are there by the naked eye. and the micro-curvature, the extent of its occurrence is very small, the naked eye is difficult to find. In other words, the general bending (such as the Racheng of the fiber) does not necessarily cause the micro-curvature. Only the curvature that satisfies a particular situation can cause a micro-curvature.





So in practice, how to avoid these two situations? A simpler way is to not press a heavy object on the fiber. Because of the long backlog of heavy objects, it is easy to cause optical fiber deformation, the phenomenon of macro-curvature, affecting the transmission of fiber signals. In addition, when deploying a fiber-optic network, it's a good idea to look at the appearance of the fiber first. Because if the occurrence of the macro, the appearance is more obvious, you can see directly from the appearance (to the obvious backlog of traces). If there is, then it is best to abandon this with fiber.





second, because the micro-curvature is difficult to see through the naked eye, this may need to pass the help of the instrument. At both ends of the fiber, a test instrument is connected, and then the degree of attenuation of the fiber can be viewed. If the user can be allowed to, then a little bit of a macro or micro-music is not a problem. But if the performance has been seriously affected, the fiber needs to be replaced.





Second, the purchase of optical fiber need to pay attention to whether there is internal tube




The attenuation of the
fiber signal is largely related to its installation. such as improper installation may lead to micro-curvature or macro-music and other undesirable phenomena. In order to avoid this situation, many optical fiber manufacturers now will be in the fiber to add a layer of "inner tube" material. This kind of material which is stretched by tubing can effectively avoid excessive bending of optical fibers.





in terms of hardness, the inner tube is much harder than the optical fiber, so it is not easy to be excessively bent. So the fiber that is protected by the inner tube is usually not easy to bend. According to the laboratory test results, it can be found that the inner tube can indeed protect the fiber. Not only can improve the tensile amplitude of optical fiber, but also to ensure that the curved fiber is not too large. Of course, because of the addition of an inner tube, the cost will be much higher. So not every brand of fiber will do so. Enterprises in the purchase of optical fiber, need to pay attention to this problem.





three, the installation needs to pay attention to both ends of the smooth





in the installation of optical fiber, than the installation of ordinary wire technology more complex. When the fiber is installed, the fiber ends need to be cut off. It is also necessary to make sure that the ends are smooth (usually through polishing, etc.) to ensure that the ends are smooth. If the end is not smooth, it will cause the signal attenuation. If the network administrator has the conditions, it is also best to use a microscope or built-in amplification equipment to detect the smoothness of the end of the fiber, to determine the degree of smoothness. In short, you need to ensure that the fiber ends are properly polished and molded.





Make sure the ends are smooth and then carefully install the ends of the connectors. The installation of this joint is also a technical activity. Because if the interface installation error, such as improper stitching, or two pieces of inconsistent size of the fiber splicing together, will greatly reduce the intensity of the light signal. In general, it is not recommended to use fiber with inconsistent dimensions.





when the fiber connector is well connected, it needs to take some protective measures. This is mainly because this part is where the signal is most likely to leak. If there is no dust, not clean, it will cause the light to reach the receiver when the large attenuation. Ensure that connectors and fiber ends are kept clean if necessary. Where necessary, a layer of protective film is also required at the end of the fiber to prevent damage. It also needs to be cleaned again when connecting the fiber to the router or switch interface. Clean method is relatively simple, generally only need to use alcohol-free lens paper wipe can be. In order to avoid dust pollution, in switches and routers and other network equipment, if there is fiber interface, usually do not need to take a certain measure of protection. such as cover the port, to prevent dust in. When you reuse it, you need to clean it again. Cleaning method is the same as cleaning the joint, only need to use a special paper to wipe it.





four, after installation to test and calculate the loss of light





even if the deployment of the most appropriate method or the use of optical fiber is the best, in the end it is still difficult to avoid the loss of light signals, but the degree of loss is not the same. If the loss of this light signal is within the range that the user can tolerate, then it is OK. On the contrary, but beyond the user's maximum, you need to analyze the reasons and take the appropriate measures.





In practice, units that measure the loss of light signals through decibels (note that this is not a unit of sound measurement). This unit indicates how much of the energy emitted by the transmitter is received by the receiver. In general, you need to test after the first installation and confirm with the user whether you can accept the value. Note that you need to record this value. This value should be used for reference in future maintenance. such as later in the use of the process of discovering network data transmission performance degradation. The administrator now needs to test it again. If you find that the test value is the same as the original, then the optical fiber is not a problem, is caused by the enterprise's own network, such as the increase in the amount of data or network architecture changes caused by the need to optimize the enterprise's network. Conversely, if you find that the loss of light energy is larger than the original, then consider the possibility of fiber or fiber receiver transmitter problem. To see if the protective layer of the fiber is damaged or if there is a lot of dust on the interface. The test of this optical fiber is very important. In the first test, it is important to record the obtained data 1510, as the basis for future fiber maintenance and network optimization.