Abstract: An ultra wide band-pass, absorptive band-reject filter has a pair of quadrature hybrid couplers cascaded and coupled by a phase shifting element and a matched pair of band-reject filters in two parallel paths. The matched pair of band-reject filters each rejects signals in a desired reject frequency band. The quadrature hybrid couplers each have an insertion loss amplitude crossover for signals propagated to terminals across the coupler that coincides with the reject frequency band. The phase shifting element is configured to have a phase shift of 180 degrees at frequencies in the reject frequency band. In a preferred embodiment, the pair of quadrature hybrid couplers are identical in performance and the band-reject filters are identical in performance with respect to a center frequency fn of the reject frequency band. The absorptive band-reject filter thereby provides an absorptive rejection response in the reject frequency band while a very wide pass-band frequency range is maintained.

Abstract: An ultra wide band-pass, absorptive band-reject filter has a pair of quadrature hybrid couplers cascaded and coupled by a phase shifting element and a matched pair of band-reject filters in two parallel paths. The matched pair of band-reject filters each rejects signals in a desired reject frequency band. The quadrature hybrid couplers each have an insertion loss amplitude crossover for signals propagated to terminals across the coupler that coincides with the reject frequency band. The phase shifting element is configured to have a phase shift of 180 degrees at frequencies in the reject frequency band. In a preferred embodiment, the pair of quadrature hybrid couplers are identical in performance and the band-reject filters are identical in performance with respect to a center frequency fn of the reject frequency band. The absorptive band-reject filter thereby provides an absorptive rejection response in the reject frequency band while a very wide pass-band frequency range is maintained.

Abstract: The optical fiber backscatter signal generator (OFBSG) generates simulated ptical fiber backscatter waveform signals that are used to characterize or calibrate an optical time-domain reflectometer (OTDR). 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 (backscattered) 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.