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SCHOTT North America
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Technologies
End Termination
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In standard light guides the fiber ends are epoxied to each other and to the end ferrule before being ground and polished. Light guide ends treated this way can withstand temperatures up to 200°C (120°C is a standard value).
Where long-term operation in excess of 200°C is involved, and particularly where additional mechanical loads such as pressure, tension, vibration or acceleration occur at the light guide end, there is a danger of the adhesive disintegrating and the light guide consequently being damaged.
In order to ensure safe operation even at high temperatures, SCHOTT has developed a unique end termination process in which no adhesive is used. Instead, the fiber ends are fused together in a process combining heat with pressure. At the same time the fibers are embedded in a stainless steel ferrule.
The benefits of hot-fused ends are:
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High temperature resistance (up to 350°C for long-term operation)
High durability in combination with high power light sources
On the end surface of a light guide with epoxied ends, interstitial gaps can be seen between the round fibers which don't make any contribution to light transmission. The fusing process reshapes the fibers, making them predominantly hexagonal, and the gaps are eliminated. As a result more fibers can be accommodated in the same optically effective cross-section resulting in a transmission increase of 15% compared with epoxied ends.
Reproducible high quality resulting from computer-controlled manufacturing process.
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bonded
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hotfused
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Light guides with hot-fused ends are particularly suitable for the following applications:
Pyrometry
Approximation switches
Spark control
For bonded light guides, end ferrules are made from alluminium, brass, stainless steel, nickel silver or other materials to customer specification. For technical reasons only stainless steel ferrules are used for hot-fused components.
In order to effeciently launch or extract light from an optical fiber bundle, the ends of each fiber should be cut, ground and polished at right angles to their optical axis. Both the quality and the method of termination will greatly influence the light guide properties. Two apparently indentical light guides may exhibit different transmission and angular output characteristics due to light guide assembly and in particular the way in which the end faces have been ground and polished.
In the final stage of production all fibers are optically ground and polished using special termination techniques to provide our customers with the highest possible quality.
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