Optical Fibre Communications Includes: Rather than using optical fibre connectors, it is possible to splice two optical fibres together. An fibre optic splice is defined by the fact that it gives a permanent or relatively permanent connection between two fibre optic cables. That said, some manufacturers do offer fibre optic splices that can be disconnected, but nevertheless they are not intended for repeated connection and disconnection. There are many occasions when fibre optic splices are needed. One of the most common occurs when a fibre optic cable that is available is not sufficiently long for the required run. In this case it is possible to splice together two cables to make a permanent connection. As fibre optic cables are generally only manufactured in lengths up to about 5 km, when lengths of 10 km are required, for example, then it is necessary to splice two lengths together. Fibre optic splices can be undertaken in two ways: The mechanical splices are normally used when splices need to be made quickly and easily. To undertaken a mechanical fibre optic splice it is necessary to strip back the outer protective layer on the fibre optic cable, clean it and then perform a precision cleave or cut. When cleaving (cutting) the fibre optic cable it is necessary to obtain a very clean cut, and one in which the cut on the fibre is exactly at right angles to the axis of the fibre. Once cut the ends of the fibres to be spliced are placed into a precision made sleeve. They are accurately aligned to maximise the level of light transmission and then they are clamped in place. A clear, index matching gel may sometimes be used to enhance the light transmission across the joint. Mechanical fibre optic splices can take as little as five minutes to make, although the level of light loss is around ten percent. However this level of better than that which can be obtained using a connector. Fusion splices form the other type of fibre optic splice that can be made. This type of connection is made by fusing or melting the two ends together. This type of splice uses an electric arc to weld two fibre optic cables together and it requires specialised equipment to perform the splice. The protective coating from the fibres to be spliced is removed from the ends of the fibres. The ends of the fibre optic cable are then cut, or to give the correct term they are cleaved with a precision cleaver to ensure that the cuts are exactly perpendicular. The next stage involves placing the two optical fibres into a holder in the fibre optic splicer. First the ends if the cable are inspected using a magnifying viewer. Then the ends of the fibre are automatically aligned within the fibre optic splicer. Then the area to be spliced is cleaned of any dust often by a process using small electrical sparks. Once complete the fibre optic splicer then uses a much larger spark to enable the temperature of the glass in the optical fibre to be raised above its melting point and thereby allowing the two ends to fuse together. The location spark and the energy it contains are very closely controlled so that the molten core and cladding do not mix to ensure that any light loss in the fbre optic splice is minimised. Once the fibre optic splice has been made, an estimate of the loss is made by the fibre optic splicer. This is achieved by directing light through the cladding on one side and measuring the light leaking from the cladding on the other side of the splice. The equipment that performs these splices provides computer controlled alignment of the optical fibres and it is able to achieve very low levels of loss, possibly a quarter of the levels of mechanical splices. However this comes at a process as fusion welders for fibre optic splices are very expensive. Mechanical and fusion splicesThe two types of fibre optic splices are used in different applications. The mechanical ones are used for applications where splices need to be made very quickly and where the expensive equipment for fusion splices may not be available. Some of the sleeves for mechanical fibre optic splices are advertised as allowing connection and disconnection. In this way a mechanical splice may be used in applications where the splice may be less permanent. Fusion splices offer a lower level of loss and a high degree of permanence. However they require the use of the expensive fusion splicing equipment. In view of this they tend to be used more for the long high data rate lines that are installed that are unlikely to be changed once installed. Wireless & Wired Connectivity Topics:
What is Fiber Optic Splicing?  Mechanical splices are simply alignment devices, designed to hold the two fiber ends in a precisely aligned position thus enabling light to pass from one fiber into the other. (Typical loss: 0.3 dB) The typical reason for choosing one method over the other is economics. Mechanical splicing has a low initial investment ($1,000 - $2,000) but costs more per splice ($12-$40 each). While the cost per splice for fusion splicing is lower ($0.50 - $1.50 each), the initial investment is much higher ($15,000 - $50,000 depending on the accuracy and features of the fusion splicing machine being purchased). The more precise you need the alignment (better alignment results in lower loss) the more you pay for the machine. As for the performance of each splicing method, the decision is often based on what industry you are working in. Fusion splicing produces lower loss and less back reflection than mechanical splicing because the resulting fusion splice points are almost seamless. Fusion splices are used primarily with single mode fiber where as Mechanical splices work with both single and multi mode fiber. Many Telecommunications and CATV companies invest in fusion splicing for their long haul singlemode networks, but will still use mechanical splicing for shorter, local cable runs. Since analog video signals require minimal reflection for optimal performance, fusion splicing is preferred for this application as well. The LAN industry has the choice of either method, as signal loss and reflection are minor concerns for most LAN applications. Fusion Splicing Method As mentioned previously, fusion splicing is a junction of two or more optical fibers that have been permanently affixed by welding them together by an electronic arc. Step 1: Preparing the fiber - Strip the protective coatings, jackets, tubes, strength members, etc. leaving only the bare fiber showing. The main concern here is cleanliness. Step 2: Cleave the fiber - Using a good fiber cleaver here is essential to a successful fusion splice. The cleaved end must be mirror-smooth and perpendicular to the fiber axis to obtain a proper splice. NOTE: The cleaver does not cut the fiber! It merely nicks the fiber and then pulls or flexes it to cause a clean break. The goal is to produce a cleaved end that is as perfectly perpendicular as possible. That is why a good cleaver for fusion splicing can often cost $1,000 to $3,000. These cleavers can consistently produce a cleave angle of 0.5 degree or less. Step 3: Fuse the fiber - There are two steps within this step, alignment and heating. Alignment can be manual or automatic depending on what equipment you have. The higher priced equipment you use, the more accurate the alignment becomes. Once properly aligned the fusion splicer unit then uses an electrical arc to melt the fibers, permanently welding the two fiber ends together. Step 4: Protect the fiber - Protecting the fiber from bending and tensile forces will ensure the splice not break during normal handling. A typical fusion splice has a tensile strength between 0.5 and 1.5 lbs and will not break during normal handling but it still requires protection from excessive bending and pulling forces. Using heat shrink tubing, silicone gel and/or mechanical crimp protectors will keep the splice protected from outside elements and breakage. Mechanical Splicing Method 1. Thoroughly and frequently clean your splicing tools. When working with fiber, keep in mind that particles not visible to the naked eye could cause tremendous problems when working with fiber optics. "Excessive" cleaning of your fiber and tools will save you time and money down the road.
Tecra Tools offers a large selection of fiber optic tool kits and fiber optic supplies. We currently stock Fibrlok Mechanical Splicing Kit from 3M and the Miller Fiber Optic Cleaver. Click here to see our Fiber Splicing Kit and let us help you find the right tools for all your fiber optic needs. Thank you for doing your business with Tecra Tools and we look forward to serving you soon! Return to Top of Page Get tips & information for field service and MRO professionals. * indicates required |
The two types of fiber optics splicing are
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