Certified jumper cables ensure accurate link-loss measurement

Most installers do not realize the importance of having jumper cables that exhibit a consistent, high-quality, low-loss range. Many contractors mistakenly believe that "zeroing out" the power meter handles the problems that poor-quality cables sometime present. Historically, many installers use a two-jumper reference method, which includes two jumper cables mated together and then "zeroed-out." But, as identified by the standards (see below), the one-jumper method proves to be a more reliable pr

Jun 1st, 1999
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Larry Widgeon and Dan Morris, KITCO Fiber Optics

problem

Most installers do not realize the importance of having jumper cables that exhibit a consistent, high-quality, low-loss range. Many contractors mistakenly believe that "zeroing out" the power meter handles the problems that poor-quality cables sometime present. Historically, many installers use a two-jumper reference method, which includes two jumper cables mated together and then "zeroed-out." But, as identified by the standards (see below), the one-jumper method proves to be a more reliable procedure.

solution

Purchase two jumper cables, which should consistently fall between 0.01 and 0.35 decibel of link loss, and two singlemode adapters. When a light source and power meter are used to check component or link loss, it is imperative that a reference cable within the aforementioned range be used. Otherwise, an accurate loss measurement of the component or link cannot be verified, and the results may not be repeatable. Jumper cables should be certified by a reputable reference cable manufacturer, and the verifications of 10 connections and disconnections should be documented in writing.

procedure

1) Clean all connectors and adapters at the test points before performing the measurements.

2) Connect jumper 1 between the light source and power meter, and record the power level displayed on the power meter as P1 (the reference power level).

3) Attach jumper 1 to one end of the cable link to be tested, and attach jumper 2 to the other end of the cable link.

4) Record the power level displayed on the power meter as P2.

5) Calculate optical loss in decibels using the following formula: Loss = P1 - P2.

Document results as required, and compare test loss limits as set by prevailing standards or documentation. Testing should be performed in accordance with the contract documentation invoking this test procedure. If no procedures are specified, testing should be performed in both directions at 850- and 1300-nm wavelengths.

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This procedure is also the accepted method for measuring link loss in accordance with mil-std-2042a, part 6, and is used for all U.S. Navy Shipboard Testing Requirements. Testing should be performed in both directions at the wavelength at which the system is expected to operate.

Larry Widgeon is president and Dan Morris is a bicsi- certified registered communications distribution designer (rcdd) and manager of fiber-optic training, both at kitco Fiber Optics (Virginia Beach, VA). This tip was submitted for the Cabling Installer Tips` Contest at Cabling Installation Expo `98, held last October in Atlanta, GA.

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