Wednesday, February 19, 2020

Visual inspection of connector by microscope

Fiber optic inspection microscopes are used to inspect connectors, in order to confirm that polishing is adequate and to find faults such as scratches, polishing defects and dirt. They can be used both to verify the quality of the finishing procedure and to diagnose problems. A well-made connector has a smooth, polished and scratch-free finish, and the fiber shows no signs of cracks, splinters or areas where the fiber is protruding from the end of the splint or inward.
The increase to visualize the connectors can be of a power of 30 to 400, but it is better to use an average increase. If the increase is very low, fundamental details may not be visible. Performing the inspection with a very large magnification can lead to the person who sees through the microscope being too critical, and rejects good connectors. Multimode connectors should use increases in the 100-200X range and single-mode fiber may use a larger increase, up to 400X. A better solution is to use a medium magnification, but inspect the connector in three ways:

   When viewing directly, the fiber and the hole of the splint can be visualized, and determine if it is of a suitable size, if the fiber is centered in the hole and if the appropriate amount of adhesive has been applied. However, with this form, only the largest scratches are visible. Adding light transmitted through the core will make the cracks visible at the end of the fiber, caused by pressure or heat during the polishing process.
    If you see the end of the connector from a certain angle, while lighting it from approximately the same angle on the opposite side or if you use lighting from a smaller angle and go directly, you will get the best inspection for polishing quality and possible scratches. The shadow effect produced by angular vision or illumination increases the contrast of the scratches against the smooth and mirrored polished surface of the glass.
    However, you must be careful when inspecting the connectors. Sometimes it tends to be too critical, especially if large increases are used. In general, only defects on the fiber core are considered problems. The glass chips around the outer part of the cladding are not unusual and will have no effect on the ability of the connector to couple light in the core of multimode fibers. Also, scratches that are only in the cladding should not cause any loss problem.

The best microscopes allow you to inspect the connector from different angles, either by tilting the connector or allowing angular illumination to get the best view of what is happening. Verify that the microscope has an easy-to-use adapter to connect the connectors of interest to the microscope.
The video output microscopes that are now available allow you to get an easier view of the connector's end face, and some even have software that analyzes the finish. Although they are much more expensive than normal optical microscopes, they facilitate inspection and greatly increase productivity.

It is important that you remember to verify that the cable has no power before looking at it under the microscope, in order to protect your eyes. The microscope will concentrate all energy that exists in the fiber and focus it on your eye with potentially dangerous results. Some microscopes have filters to stop the infrared radiation of the transmitters in order to minimize this problem.

1 comment:

  1. Automatic optical inspection You made such an interesting piece to read, giving every subject enlightenment for us to gain knowledge. Thanks for sharing the such information with us to read this...

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