This INTEGER value (in ps/nm, default -45000) sets the low end of the chromatic dispersion search range that the coherent optical channel (och-os) on the line side of a pluggable transceiver's coherent receiver scans when acquiring dispersion compensation for the incoming signal. An administrator narrows this bound when the approximate fiber distance and dispersion characteristics are already known, which can speed up how quickly the receiver locks onto the signal during turn-up. For example, an administrator provisioning och-os for a known short-haul span might raise this low bound closer to zero from the default -45000 so the receiver doesn't search across dispersion values that are physically implausible for that span.