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How to test connectors: a slightly modified field-test procedure requires careful attention to detail - Cabling, Wiring and Enclosures

Communications News, Oct, 2002 by Robert Zahr

With the escalating popularity of the MT-RJ connector for optical fiber cabling systems, there is a growing need to implement proper field-test procedures to ensure reliable cabling connections between the signal source and destination at the time of installation. TIA/EIA 568-B, Commercial Building Telecommunications Cabling Standard, and ISO/IEC 11801, Generic Cabling for Customer Premises, refer to the use of the "one-reference jumper method" specified in ANSI/TIA/EIA-526-14-A, Method B, for measuring link attenuation of multimode fiber.

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The need for a modified one-reference jumper Method B field-test procedure stems from the fact that the MT-RJ is a dual-fiber connector design. The vast majority of test equipment in use today has either single or dual straight tip (ST) or standard connector (SC) fiber ports as the interface. Accordingly, the one-reference jumper measurement procedure must be slightly modified in order to test MT-RJ systems using MT-RJ to ST or SC test cables, which essentially convert an ST or SC optical test set to MT-RJ.

In years past, reference measurements were taken first--primarily to zero the loss of the one jumper used in the test. After zeroing out the test lead, it was expected to maintain the connection on the source side throughout the testing procedure.

While this is still an acceptable practice, the transition from the traditional ST or SC connection type on the test equipment to the MT-RJ connection may require disruption of the source connection. Fortunately, connector technology and tolerances have improved over the years, reducing connector-to-connector variability and the accompanying test variances. As important as ever is verifying that the jumpers used for testing are good, quality jumpers.

One testing procedure is recommended for a test set with dual ports (one transmitter and one receiver); a second can be used for a test set with only one port available (either a source or a power meter). The ideal method for testing MT-RJ systems is to use a test set with MT-RJ test ports. Until these devices are readily available, dual-port power meters to test two fibers simultaneously--testing one fiber of the pair in one direction and the other fiber in the reverse direction--is acceptable. Testing the MT-RJ system with a single port test set is less efficient (since only one direction can be tested at a time), but is still effective.

The procedures outlined here assume the test equipment has ST-compatible interfaces; however, the same procedure can be used for any single-fiber interface (SC, FC). As the MT-RJ interface option becomes available on optical test sets, the switch to the traditional TIA/EIA-526-14A Method B, one-reference jumper, is recommended.

The first steps of this procedure are designed to acquire a system reference and change the interface of the test equipment to MT-RJ. Prior to testing, verify test-lead performance. Instructions on how to verify test-lead performance, as well as test-kit configurations and additional details, can be found in the "MT-RJ Optical Fiber Systems Testing" white paper found at http://www.mtrj.com/. MT-RJ test-lead kits that contain special test leads and couplers are available from test equipment manufactures and MT-RJ vendors.

Step 1. Connect the pinned MT-RJ to ST jumper to one test unit (the MT-RJ in this jumper has preinstalled alignment pins unlike the MT-RJ connectors of standard MT-RJ, which are pinless). Connect the unpinned MT-RJ to ST jumper to the other test unit. Mate the two plugs together through an MT-RJ coupler.

Verify that the ST connectors are properly connected to the test equipment (i.e., connector A to receiver and connector B to transmitter). Do not disconnect the jumpers until testing is complete. If mandrels are used, they should be connected to the transmit side of both sources. Zero or reference the meter per the equipment-manufacturer's recommendation.

Step 2: Disconnect the unpinned MT-RJ from the adapter and insert this plug into the jack of one end of the system under test. Connect a standard (without pins) MT-RJ to MT-RJ jumper between the pinned MT-RJ test lead and the jack of the other system end.

The next test procedure described is to be used when only a one-port test set is available to do the testing. The first phase of this procedure is to acquire a system reference and change the interface of the test equipment to MT-RJ.

Step 1: Connect the pinned MT-RJ to ST jumper to one test unit (the MT-RJ in this jumper has preinstalled alignment pins unlike the MT-RJ connectors of standard MT-RJ, which are pinless). Connect the unpinned MT-RJ to ST jumper to the other test unit. If a mandrel is used, it should be connected to the transmit side of the source. Zero or reference the meter per the equipment-manufacturer's recommendation.

Verify that the ST connectors are properly connected to the test equipment (i.e., connector A to receiver and connector B to transmitter). Do not disconnect these jumpers until testing is complete.

Technology Industry

How to test connectors: a slightly modified field-test procedure requires careful attention to detail - Cabling, Wiring and Enclosures

Communications News, Oct, 2002 by Robert Zahr

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