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Fiber Optics

MECHANICAL SPLICES

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Fiber Optics

Knowledge of fiber optic splicing methods is vital to any company or fiber optic technician involved in Telecommunications or LAN and networking projects.

Mechanical splicing is an optical junction where the fibers are precisely aligned and held in place by a self-contained assembly, this is a semi-permanent bond.

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Fiber Optics

This method aligns the two fiber ends to a common centerline, aligning their cores so the light can pass from one fiber to another.

There are several methods and at least half a dozen different mechanical splices to choose from.

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Fiber Optics

Mechanical splicing is normally a function of cable plant restoration due to an accident causing a fiber optic cable to be broken or cut.

Back hoes are infamous for pulling up direct buried cables and in some instances these cables can be fiber.

So as a result we would need to perform an emergency cable restoration.

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The mechanical splice provides a temporary fix until an new cable can be installed.

This method of splicing can provide a fairly low loss solution usually around 0.3dBm to 0.5dBm

The splices are placed in a weather proof enclosure for protection and re-buried, more often than not temporary becomes permanent, especially if the data link is working well.

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The quickest and easiest way to do an emergency restoration is by means of a mechanical splice.

The process of mechanical splicing is very similar to the light crimp terminations that you learned in a previous lesson.

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Two cleaved fiber tips are mechanically aligned to each other by a special housing.

Index matching gel is positioned between the fiber tips to maximize coupling and minimize back reflection.

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Fiber Optics

The Siemon splice has an alignment window and adjustable end collet nuts to adjust and secure the fiber for optimum alignment and low loss.

Why two different colors here for the same splice?

SM & MM

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• What do you thing is the most critical step in the splice process to achieve a very low loss connection?

JUST LIKE THE LIGHT CRIMP TERMIANTIONS THE CLEAVE WILL DETERMINE HOW SUCCESSFUL THE SPLICE IS

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There are some significant advantages of using a mechanical fiber splice rather than fusion splices. Here are a few of them:

1. Mechanical splices require no power supplies.

2. Many mechanical fiber splice designs require no extra tools beyond a fiber stripper and fiber cleaver.

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3. They can be used in situations where fusion splicing is not practical or impossible.

4. Mechanical splices can be made within a couple of minutes, this makes it ideal for temporary connections.

Fiber optic mechanical splices have their cons too.

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Fiber Optics

1.Higher insertion loss. The typical insertion loss for a mechanical splice is about 0.3dB which is significantly higher than the 0.02dB loss for a typical fusion splice.

2.Mechanical splices are typically for multimode fibers. The tough alignment tolerance for single mode fibers makes it hard for mechanical splices to meet the required loss budget.

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1.Mechanical splice is more expensive than fusion splices, but if you take into account the expensive fusion splicing machines that fusion splices need, the average cost is actually much lower for mechanical splice if you just do a few splices.

2.Since the refractive index of most index matching compounds varies with temperature, so the optical performance of a mechanical splice can be sensitive to ambient temperature.

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3. Mechanical splices are not thought to be as reliable as fusion splices over long periods of time.

4. Mechanical splices are used only in relatively benign environments such as inside an office building.

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V-groove has been used widely in aligning optical fibers. The most obvious example is its success in fusion splicing machines. Look at the following illustration.

V-groove is the most commonly used alignment mechanism for mechanical fiber splices. V-groove consists of a base plate in which a precise V-groove is etched.

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1.Cleaved fibers are placed into the groove and their ends are butt-coupled into contact.

2.Index matching gel is used to bridge the gap between the two ends to prevent gap loss and to reduce Fresnel reflection.

3.A locking mechanism then holds the fibers in position and provides mechanical protection for the fibers.

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4. Index matching epoxy can be used in place of index matching gel.

5. The epoxy is usually cured with ultraviolet light, the epoxy can hold the fibers in place

6. Mechanical splices are then placed in a tray.

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The splice whether mechanical or fusion is placed in an enclosure, these can be direct buried, manhole or aerial type enclosures.

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Another form of mechanical splicing is the use of a coupler and simply coupling two connectors together.

This is the down and dirty method and is used as an indoor solution.

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Data centers or IT rooms may need this type of splice to be done in an emergency and this is usually done under the raised floor of a computer room.

BY USING SIX PACKS WE CAN QUICKLY SPLICE A 6 STRAND OR HIGHER COUNT FIBER

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The loss of a coupled splice is much higher than that of a mechanical splice and should be strictly a temporary solution.

If an emergency arises most companies in the Telecom industry will have the Uni-cam kit and connectors on hand.

Where as with mechanical splices they would usually have to be ordered.