Reflectometers

Reflectometers are instruments that analyze reflected signals to characterize a system or material. The term encompasses devices used across electrical, optical, and acoustic domains. By emitting a probe signal and measuring the returned wave, a reflectometer can determine impedance or refractive index, locate faults along a transmission path, or infer layer structure and thickness at interfaces.

Time-domain reflectometry (TDR) sends a fast electrical pulse along a conductor or cable. Reflections from impedance changes are recorded as a function of time, revealing fault positions, connector quality, and cable integrity. TDR is widely used in coaxial, twisted-pair wiring, and printed circuit boards.

Optical time-domain reflectometry (OTDR) uses short light pulses in fiber optics and detects backscattered light to produce a trace versus distance. OTDR identifies splices, breaks, and attenuation profiles along fiber. Optical frequency-domain reflectometry (OFDR) employs continuous-wavelength scanning with coherent detection, offering higher spatial resolution.

In microwave engineering, vector reflectometry measures the complex reflection coefficient across a range of frequencies, aiding impedance matching and network diagnosis. Acoustic reflectometry uses ultrasound to characterize layered materials and detect defects on surfaces or within samples.

Common outputs include return loss, reflection coefficient, impedance, and distance to events. Key uses include network installation and fault finding, nondestructive testing, fiber-optic deployment, and materials science.

Performance depends on source bandwidth, noise, dispersion, and termination quality; calibration standards are essential; interpretation may be hindered by multiple reflections or scattering.