Modular test system automates 802.3aq compliance testing

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Circadiant Systems (Allentown, PA) recently released its Hydra modular test system (MTS), which the company says ranks among the industry’s first commercially available 10-Gigabit Ethernet (GbE) long-reach multimode (LRM) compliance test systems.

“With regard to LRM, there are severe cost pressures throughout the industry to get costs down,” contends Joey Thompson, cofounder of Circadiant. “There’s a horse race right now [among module vendors] to be the first with a legitimate product to market so that they can use the standard in enterprise 10-GbE networking applications. And that’s where we come in: We enable people to test compliance to the standard easily.”Th 210723

Circadiant’s Hydra MTS enables quick, accurate compliance testing of 10-Gbit components such as electronic dispersion compensators, as well as modules and subsystems per the IEEE 802.3aq draft standard for 10-GbE LRM transmissions.

Circadiant says that the “comprehensive, all-in-one” Hydra MTS is designed to solve issues such as calibration, instrument drift, and system-to-system correlation, all of which can slow design cycles, by providing standard-compliant measurements for stress testing, variable pattern generation, bit-error ratio (BER) versus optical modulation amplitude (OMA), and automated transmitter wavelength-dispersion penalty (TWDP).

“There’s clearly a trend in the industry to move toward what I keep calling ‘real-world’ testing: People want to test their devices and their systems with signals that are impaired in a way that duplicates the type of impairment that can happen in real life,” observes Thompson. “That’s not something that used to happen with SONET so much, but it’s clearly happening now.”

The 10GBase-LRM PMD, defined in the IEEE 802.3aq draft standard, was conceived to allow 10-GbE transmissions over the existing FDDI multimode fiber that populates the majority of corporate complexes, accounting for more than 60% of installed fiber, according to Circadiant. The company maintains that the standard was conceived to ensure a 10-GbE “optical plug-and-play architecture” over a minimum of 220 m of low-grade multimode fiber.

The company says its Hydra MTS is designed to enable quick, easy, and accurate compliance testing of 10-Gbit components such as electronic dispersion compensators, as well as modules and subsystems per the latest 802.3aq standard. The system is designed to test all physical layer aspects of the standard, including stressed receiver sensitivity (SRS) and TWDP.

“A module, a line card, and an active network, they all share one thing: They have a receiver that needs to be able to extract the data successfully from the impaired signal,” explains Thompson. “So we enable each of these market segments to test their interfaces with a ‘real-world’ impaired signal.”

The test system generates standard-compliant stressors to mimic worst-case optical degradations while automatically measuring receiver BER performance as a function of output power. The system also automates TWDP testing through an external high-speed sampling scope for the transmitter portion of the standard.

Circadiant says the Hydra MTS generates fully compliant test signals per the 802.3aq standard, including all three stressors (precursor, symmetric, and postcursor), additional noise source, and jitter. Proprietary TWDP measurement software automatically controls the external scope and corrects for the measurement limitations of sampling scopes to deliver accurate TWDP results. The company notes that the Hydra MTS further speeds the process for accurate LRM compliance testing by combining receiver and transmitter test functions.

“Just because the module vendor says his module works, doesn’t mean that you get successful results when you put that in a real-world system-you really need to test at every level,” concludes Thompson.

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