In a device for continuously varying the extinction ratio, ER, a laser diode is connected to a first end of a PZ fiber. The test logic includes a built-in self test apparatus providing logic to simultaneously and independently test the memory devices interfaced to one or more of the hub device ports using read and write data patterns. A user can select charts associated with a data records for comparison from an index of data records. A reject level is identified along the grayscale distribution.