Selecting fiber-optic products

Selecting fiber-optic products can be confusing. However, the following guidelines may help you avoid problems when you are choosing fiber-optic cables and connectors.

Eric R. Pearson, CPC, Pearson Technologies Inc.

Selecting fiber-optic products can be confusing. However, the following guidelines may help you avoid problems when you are choosing fiber-optic cables and connectors.

General guidelines

1) Before you contact any vendor, use a summary sheet to list the specifications for cables and connectors. If you have all the specifications for each component available when you are talking with potential suppliers, you can avoid overlooking a specification.

2) Talk to at least four vendors for each component. This will help you determine the competitive price, verify accuracy of information and uncover performance concerns.

3) You may receive conflicting information from vendors. To resolve such conflicts before you choose your products, ask for test data to support all the information.

4) Choose suppliers that have been in business for at least five years. Their experience can help guide you to avoid problems.

5) Avoid being a beta-test site for the vendor (unless you have a good reason to do so). Do not buy products with a low serial number; the serial number usually indicates how many parts have already been made.

6) Before you choose the design, understand what the cost impact of one design over another will be; for example, the cost of ST versus SC connectors, or loose-tube versus breakout or premise cable.

7) Buy only the performance you need. You will not gain anything by paying a premium price for performance you will not use.

Selecting cable

8) Ask if the manufacturer has a product in stock that is close to your needs. For example, a cable manufacturer may have a 10-fiber cable with one or two fibers that do not meet its specification, but it will meet your need for an 8-fiber cable.

9) Look for the best price possible consistent with your product performance and delivery needs. The fiber-optic cable industry is competitive: Cable prices can differ by 40%.

10) Do not pay for premium performance unless your design calculations support this need. Many data-communications applications do not need the highest bandwidth products available. Price, of course, is not the only consideration; reliability, workmanship, quality and delivery are equally important.

Choose connectors with operating limits equal to or greater than the range of operating conditions imposed by the environment of the application. The trend in connectors is that the easier the installation, the more likely there will be some reduction in performance; for example, cable retention strength, temperature range.

- The cable retention strengths of epoxyless/adhesiveless connectors (that use a mechanical method for gripping the fiber) are usually lower than connectors that require the use of a curing epoxy or adhesive. But this is not relevant to the application when connectors are not subject to severe pull loading.

- Another example is connectors preloaded with an adhesive material that requires preheating. Such products have a reduced upper temperature operating limit; however, this limit is irrelevant if the application does not subject the connectors to excess temperatures. Generally speaking, if a connector is easy to install, you may find some reduction of performance.

While contact connectors--ST, FC and SC--have the advantages of low loss, low backreflection and low cost, they may not always be the best choice. In environments where there is significant shock, vibration or dirt, such noncontact connectors as SMA or biconic are preferable. Shock, vibration or dirt can result in damage to the fiber surface when the contacting fibers bounce against each other.

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