Fiber Weave Effect

Signal Skew

Differential trace pairs that run parallel to the fiber bundle orientation are especially vulnerable to timing mismatch. If one line of the pair lies over a glass bundle and the other lies over resin, their signals arrive at the receiver at slightly different times. This timing mismatch, or skew, degrades the differential signal quality and increases electromagnetic interference.

In severe cases, the timing difference exceeds the receiver’s jitter tolerance, causing data errors and packet loss. This performance drop can render a high-speed communications card completely non-functional.

Mitigation Design

Designers mitigate this issue by routing high-speed traces at an angle relative to the woven grid or by specifying spread glass styles. Angling the trace ensures that both lines of a differential pair cross an equal number of glass bundles and resin pockets, averaging out the dielectric differences.