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34 I ICT TODAY manufacturing defects with wrong or reversed polarities, mislabeling, or damage during shipment. For AOCs, they may get excessively bent, causing high loss, or the optical fibers may get crushed. In the case of DAC, there can be EMI degradation resulting in excessive bit errors. Prior to installation, a technician can choose to test all AOC/DAC cables using a test device equipped with dual-port SFP/QSFP or simply sample test a subset of the cables received from a batch. Troubleshooting cables that are already installed requires two devices because of the distance between the two cable connector endings. Bit Error Rate Testing The simplest and most effective way to test cables is to run a test pattern where the results can be compared to a bit error rate (BER) threshold. AOC and DAC cables usually have a BER rating on their datasheets, especially when they are meant to be used with devices implement- ing the RS-FEC algorithm. This BER rating depends on the type of cable, line rate and type of Ethernet interface. In the case of a cable meant for use with RS-FEC encoded traffic, which is typical at 100 GbE and 25 GbE, there may even be both a pre-FEC rating, which is before error correction, and post-FEC rating after error correction. In this case, it is recommended to perform a cable test using a pre-FEC BER threshold close to the cable BER rating and ensure the measured BER is smaller than the threshold for a successful test. For 40 GbE and 10 GbE cables where RS-FEC is not used, the expected BER threshold needs to be quite a bit smaller as there is no error correction on those circuits. In such cases, if there is no BER rating for the AOC or DAC, the recommend- ed BER threshold is 10 -12 . Test times of one minute per cable are more than sufficient to obtain meaningful BER results with line rates of 10 gigabits per second or higher. Best practice procedures for cable tests will result in the generation of test reports including a cable identifier, such as the serial number, which can be read from an AOC or DAC cable. In summary, ensuring AOC or DAC cables are tested against their target BER thresholds is a meaningful method to ensure cables will be functional when connected to switches and servers in the data center. Conclusion: Optimum Testing of AOC and DAC Cables ANSI/BICSI 002-2014 section 9.11 covers Testing and Quality Assurance, as well as many testing best practice procedures that should be followed. From a test unit and optimum testing of AOC and DAC cable perspective, technicians should seek a complete test and measurement solution in an all-in-one testing unit that provides line rates up to 112 Gbps. For contractors and installation companies, there are Because AOC and DAC cables do not provide test access to the actual fiber or copper cabling, traditional media test and certification tools cannot be used to certify the cable. ® ANSI/BICSI 002-2014 Data Center Design and Implementation Best Practices an American National Standard Datacenter 002 cover.pdf 1 9/24/2018 11:45:04 AM