This article describes the issue of the RXDATA is not derived from the optical line error message being generated in syslog.

The following error message is generated in the logs:

Oct 21 17:06:33 ROUTER fpc2 .pm3392.2.0. XSBI: RXDATA is not derived from the optical line

Certain digital data streams, especially high-speed serial data streams (such as optical fiber communications), are sent without an accompanying clock signal; but the receiver is required to process this data synchronously. 

So, the clock or timing information must be recovered from the incoming data stream at the receiver. Most of the clock recovery circuits employ some form of a PLL (Phase Locked loop). The receiver generates a clock from an approximate frequency reference and then phase-aligns to the transitions in the data stream with PLL. This process is commonly known as clock and data recovery (CDR). If the CDR fails in recovering the reference clock, this error message is logged in syslog.

These errors are hardware based. Excess timing jitter on the receiving optical data stream might be a possible trigger of the errors. All terminals and ports on both ends should be cleaned. Subsequently, if the error still persists, verify the attenuation in the signal and if the optical power level is appropriate. The optical transmission line and opposite optical transmitter should also be checked.