DesignCon 2022 Schedule Builder

High speed serial data buses, such as 10 Gb/s Ethernet and faster, prescribe the measurement bandwidth used for measurement. This practice improves repeatability of test across vendors. Originating in telecom, then popularized in Ethernet for datacom, this is now becoming important in standards for automotive and other markets using high speed serial data. The usage of Ethernet in automotive standards in particular is hurt by lack of precedent, and the IEEE 802.3’s preference to “rely on the discretion of the implementer” in some parts of the specification. Consequently the specifications of measurement bandwidth is in practice often misunderstood or poorly implemented and results in measurement errors.

We explain the rationale for controlling the bandwidth of the measurement equipment, and what the impact of the standard specification on measurement results. Further we will discuss the part that only a few optical standards explicitly mention in spite of the fact that it impacts both electrical and optical signals’ measurements alike: the end of measurement filter compliance.

We will also discuss the 802.3’s policy of relying on the implementer’s expertise in some specifications, and how to interpret the standard’s requirement technically, without bias.