the optical fiber backscatter signal generator generates simulatedptical fiber backscatter waveform signals that are used to characterize or calibrate an optical time - domain reflectometer . an otdr is a commercially available test instrument that measures loss and length of a fiber optic cable by launching an optical signal into the cable and measuring the power that is reflected back into the otdr . the ofbsg device creates a simulated optical fiber backscattered signal of a virtual cable and couples this signal into the otdr so that length accuracy , loss accuracy , and dynamic range of the otdr can be determined . an electrooptical section , a signal generator section and a microprocessor section that is programmable to simulate a variety of cable anomalies , provide adaptability to accommodate a wide variety of otdrs and , by reason of its sound engineering design , it is capable of being used under adverse conditions such as those encountered in the field .