A rotary-type fastening structure for fixedly coupling an extension rod with a coupling plate, having a rotatable fastening device in the form of a main body with an off-center shaft hole. The series string of sensors is excited by optical power coupled from the broadband source port, and returns optical signal response to a sensor port of the OADM, which optical energy is added to optical energy at the signal input port to form the signal output port. A data integrity is determined to be consistent at the recovery point by examining data and meta-data associated with the recovery point.