BERT takes on 400 Gbps links

-May 17, 2016

This product is featured in EDN's Hot 100 products of 2016. See all 100 here.
If you walked the exhibit floor or attended the conference at DesignCon or OFC, then you surely heard talk of 400 Gbps links. Both IEEE 802.3bs and OIF CEI-56G (Optical Internetworking Forum) have declared that 400 Gbps links will use eight 56 Gbps channels and both standards allow for the use of either 56 Gbps NRZ (non-return-to zero) or 28 Gbps PAM4 (four-level pulse-amplitude modulation). Regardless of which transmission for you use, you'll need to generate test patterns and measure bit errors.

Seeing that need, Keysight Technologies has introduced the M8040 BERT (bit-error rate tester). Consisting of AXIe pattern generator and error detector modules, the M8040A can, at the present time, produce and detect 32 Gbps NRZ and 32 Gbaud (64 Gbps) PAM4 signals. Future versions will double the data rates. The current 32 Gbaud (64 Gbps) PAM4 capability give the M8040A the ability to test 28 Gbaud (56 Gbps) PAM4 links now.

The pattern generator—a 3-slot M8045A—lets you add jitter and de-emphasis to transmitted signals when you add the M8057A remote head (shown in photo, click to enlarge). That lets you measure BER under less than ideal conditions.

The remote head lets you shorten connections between the DUT and the measurement instrument, which minimizes signal losses and crosstalk in the measurement loop. "Channel loss is significant above 16 GHz," said Keysight's BERT Product Manager Ellen Spindler.

NRZ and PAM4 modulation are software selectable and the pattern generator lets you adjust PAM4 nonlinearity, which means you can adjust the shape of the signals and test over a range of eye patterns. By changing eye height in PAM4 or NRZ signals, you can test a receiver for bit detection at varying voltage levels (eye height) and you can test for clock recovery.

M8040A prices

32 Gbps NRZ 32 Gbaud PAM4 64 Gbps NRZ 64 Gbaud PAM4
Pattern generator module M8045A (3-slot), 1 ch with jitter and de-emphasis, remote head M8057A $189,000 $257,000 $300,000 $388,000
Error detector module M8046A (1-slot), 1 ch $58,000 $125,000 Not available Not available
AXIe 5-slot chassis, M8070A software and embedded controller $32,000 $32,000 $32,000 $32,000

Keysight Technologies, M8040A product page.

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