Abstract: A lightwave component measurement system provides modulation measurements and the use of digital signal processing for the resolution of single or multiple optical reflections in optical fiber cable or in open beam at discontinuities attributable to changes in the effective index of refraction in an optical transmission medium. The lightwave component measurement system preferably incorporates a transform capability that converts data measured in the modulation frequency domain to the time or distance domain. The time-domain data are both stable and accurate, since they are calculated from highly-stable, highly-precise frequency-domain information. The time-domain transform capability in the lightwave component measurement system allows a reflection to be located to millimeters, and resolution of multiple discontinuities just centimeters apart.

Abstract: A lightwave component analyzer comprising at least an internal optical receiver and preferably also comprising an internal optical source which are selectively connectable by switches configurable by means of an internal or an external instrument controller for calibration and performance of electro-optical, opto-electrical, and optical measurements. The switches are arranged in a switch matrix. The configurable switch matrix is connected by the instrument controller in response to selection of a measurement by a user to facilitate calibration of, and test measurements of devices under test with, the lightwave component analyzer.

Abstract: A method and apparatus for calibrating absolute and relative measurements of modulation and/or demodulation transfer characteristics of electro-optical and opto-electrical devices during setup of a lightwave component measurement system for characterizing performance of fiber optic systems and associated components. The lightwave component measurement system calibrated in accordance with the method of the invention provides the capability to measure the optical, electrical, and, especially, the electro-optical (E/O) and opto-electrical (O/E) components with specified measurement performance. In accordance with the calibration method of the invention, when the lightwave component measurement system is used to characterize an E/O or O/E device, an initial calibration reference is established based on the known characteristics of a lightwave source and lightwave receiver included in the lightwave component measurement system.

Abstract: A signal measurement system with softkey menus for guiding a user in selecting a desired test setup, including selection and connection of the device to be tested, as well as selecting calibration measurement and test measurement for the device. In response to a given softkey selection, the signal measurement system prompts the user with a set of displayed textual instructions and pictorial diagrams via a user interface to step the user through setup, calibration, and measurement processes. Preferably, a signal processing unit (or analyzer) included in the signal measurement system incorporates the user interface in firmware to guide and aid the user in connecting the device to be tested to the signal measurement system for the desired test, and leading the user through calibration and measurement processes. The analyzer preferably displays the softkey menus, instructional text displays, and pictorial block diagram displays on a cathode ray tube included in the analyzer to guide the user.

Abstract: A polar display representing the ratio of two input signals is provided by exponentiating the logarithmic ratio of two input signals. The DC voltage thus produced, which is proportional to the ratio between the two input signals is then multiplied by a constant amplitude AC signal derived from one of the input signals and thus converted to an AC signal which is phase coherent with that input signal. This AC signal is then split into its orthogonal components, using an AC signal derived from the other input signal, to generate the X and Y coordinate of the polar diagram.

Abstract: A network analyzer is provided with an electronically variable phase shifter in the IF portion of the reference channel, and the phase shifter is connected to sweeping signal generator (sweeper) driving the device under test. As the output frequency of the sweeper changes, the control signal to the phase shifter changes the phase shift in the IF portion of the reference channel, compensating for phase differences between the test and reference signals due to different line lengths in the two signal paths. The electronically variable phase shifter may comprise a linear phase shifter such as a phase lock loop along with a frequency multiplier and down converter to multiply the phase shift produced by the phase shifter.

Abstract: A network analyzer is provided with an electronically variable phase shifter in the IF portion of the reference channel, and the phase shifter is connected to sweeping signal generator (sweeper) driving the device under test. As the output frequency of the sweeper changes, the control signal to the phase shifter changes the phase shift in the IF portion of the reference channel, compensating for phase differences between the test and reference signals due to different line lengths in the two signal paths. The electronically variable phase shifter may comprise a linear phase shifter such as a phase lock loop along with a frequency mulitplier and down converter to multiply the phase shift produced by the phase shifter.