How to Improve Fiber Optic Connector Adapter Efficiency

Tip 1: Check the stability of your test setup after reference

After completing the IL reference, connect the test leads directly to the power meter and observe the IL value while moving the reference fiber slightly on the bench. Power level variations should be small (approximately 0.00 +/- 0.02 max). If the power level changes when the reference fiber is moved, there may be a problem with the test layout (bent/clamped fiber or poor fiber adapter connection, etc.).

Tip 2: Find out why your losses are high

Higher wavelengths are more sensitive to losses caused by excessive fiber bending. Lower wavelengths are more sensitive to loss due to fiber misalignment in the adapter. If you are testing SM fiber and cannot meet the IL specification, look at the IL results at 1310nm and 1550nm. In an ideal environment, the two results should be "equal" (within about 0.02 dB). If the 1550 result is much higher than the 1310, the main cause of the loss may be excessive bending of the fiber somewhere in the assembly. If the 1310 results are much higher than the 1550, the main cause of the loss may be poor fiber-to-fiber alignment when the fiber optic connectors are mated.

Tip 3: Make sure the gasket is dry before connecting

Alcohol is often used to clean end faces prior to docking. If any liquid remains on the end face, it can act as an "index matching" liquid when used with another connector, resulting in abnormally high RL values. To ensure accurate RL results, make sure the end faces are clean and dry before mating (note: this is another reason why 99%+ pure alcohol is always recommended for cleaning as lower purity has a higher moisture content and does not evaporate as quickly) .

Tip 4: It is impossible to have a negative IL value

When you insert light into one end of a fiber optic component, there is always less light coming out the other side - there is always a certain amount of light loss - and it is impossible for a passive fiber optic component to emit light. If you test the IL on a fiber optic assembly and the result is negative (meaning, you are getting more light from the assembly than the test leads put in), your setup reference is invalid and needs to be zeroed again.

Tip 5: Securing the Detector

In order to obtain accurate IL results, it is critical that the test system's photodetectors be clean and free from scratches or other such defects. The surface of the detector should be inspected periodically and cleaned as necessary (5x magnification is sufficient). But be very careful when cleaning, refer to your test system user manual for proper detector cleaning - some detectors have an anti-reflective coating on the surface which will degrade if cleaned with alcohol.

Damaged photodetectors can cause major testing problems and are expensive and time-consuming to repair. Always contact the device manufacturer for recommended photodetector maintenance.

Tip 6: Test Lead Quality

As they say, "The chain is the strongest link and the weakest link". For IL and RL test systems, the weakest link is usually the test leads. Even with the best power supply and power meter, if your test leads are of poor quality, the accuracy and repeatability of your IL results will be poor. Core-to-ferrule OD concentricity of the test wire is critical to obtaining accurate and repeatable IL results - especially when testing singlemode, where even a small misalignment will Causes significant wire shift, resulting in incorrect IL measurements when used with the DUT.

Test lead ferrules should be of the highest quality and tightest dimensional tolerances and should be polished to meet or exceed typical industry standards for geometry and appearance, with core to ferrule outer diameter eccentricity of 0.5 microns or less. (Again, this is more important for smaller core sizes than for larger core sizes, since any decentering effects will be more pronounced for smaller core fibers). When everything else looks good but the results still don't seem right, consider stocking and using your master fiber optic test cord.

Tip 7: Inspect and clean device connectors before testing

Before testing, it is important that the "air referenced" return loss reading of the device interface connector is at least 65 dB within the dynamic range of the instrument.