Fiber Cleaning & Inspection
The ability of a test setup to measure fiber optic cables and components accurately is highly dependent on the quality and condition of the cables used. Connectors especially are susceptible to dirt or scratches on the fiber end face. These imperfections can cause excessive loss and prevent proper mating of connectors, all of which compromise the performance and results of the test. There are steps that operators can take for the prevention, detection, and correction of these issues.
Prevention: Dust Caps and SAVer Cables
The most effective way to protect connectors and equipment interfaces from dirt or damage is to keep them covered when not in use. OptoTest equipment ships with dust caps on all ports and it is strongly advised that you keep the dust caps and use them to cover any open ports. Cables also ship with dust caps and should be covered when they are not connected in a bulkhead.
Besides covering ports when not in use, another prevention step for the front panel is to avoid excessive connections to it. SAVer cables are a great tool because launch cables mate to them rather than to the front panel directly. This is especially useful for test environments when the same equipment is used to test different connector types that require different launch cables in the setup. Should damage occur at the connector interface, the SAVer cable is more accessible for cleaning and repair than the internal connector.
Prior to mating connectors to the test equipment or to each other, all end faces should be inspected to identify impurities or imperfections. Typically, the naked eye is not enough to detect these impurities so there are a number of handheld and benchtop tools available to help inspect connectors. Through our partnership with Sumix we are able to offer some of the best inspection and interferometer devices in the industry, including the very same ones that we use in house for our production needs.
Correction: Cleaning Tools
When dirt or damage is found on the end face of a connector, it is important to address the problem before that cable can be used as it could compromise other elements of the setup. The types of imperfections can range from surface dirt to deep scratches and must be dealt with accordingly.
Note that in addition to the connector surface, dirt can also enter the guide pin holes of MPO/MTP connectors and prevent proper mating. A brush cleaning tool can be used to dislodge dirt from these connectors.
For surface dirt, dry cleaning using a cleaning tool is sufficient. Alternatively, nonwowen dry cleanroom wipers like the TX604 from Texwipe® can be used. If the impurities do not come off by dry cleaning, like in the case of water spots or oily residue, deeper cleaning with alcohol and TX604 wipers is recommended.
Once a connector end face is cleaned of impurities, one of two things will happen: the connector will be deemed ready for use or the cleaning will expose deeper imperfections that must be addressed. Polishing is the next step to do away with pits or scratches on the connector surface. Polishing by hand is best for individual or small quantities of connectors. If multiple connectors require polishing there are machines that can do so at higher volumes, such as the Domaille polishers that we use in-house.
Any deeper scratches that are not fixed by polishing may require that the connector be re-terminated or the entire cable be replaced. These should be the last resort for addressing issues as they will likely require some level of re-calibration of the device in the case of internal connectors on test equipment.