The present disclosure provides for systems and methods for quasi-static and dynamic characterization and adjustment of radio frequency aperture and transmission. The system may comprise a transmission structure with a plurality of sensors. The system may comprise a plurality of optical metric markers. The system may receive corrective signals, shape, or deflection knowledge, or any combination thereof, from an estimator to one or more controllers. The method may comprise association of distance measurements received from a plurality of sensors through physical system identification to plot cartesian coordinates in three-dimensional space as a function of time. When the system comprises one or more controllers, the controllers may be actuated in response to shape or deformation knowledge provided by the computation module. The estimator may comprise phase correction of a large array from sparse data that is then translated to controller actuation.

A process including the following steps: injecting in an optical fiber a first optical pump at a first optical frequency that evolves in time or not, and a second optical pump at a second optical frequency that evolves in time or not, the first optical frequency and the second optical frequency being different at each given time; a first detection of a first Rayleigh backscattered signal at the first optical frequency from the optical fiber; a second detection, separated from the first detection, of a second Rayleigh backscattered signal at the second optical frequency from the optical fiber; and analyzing the detected first Rayleigh backscattered signal and the detected second Rayleigh backscattered signal.

Resonator measurement system having at least MEMS and/or NEMS, comprising: an optomechanical device comprising at least one resonating element at at least one resonance frequency of fr and at least one optical element whose optical index is sensitive to the displacement of the resonating element, excitation circuitry of exciting the resonating element at least at one operating frequency of fm, injection device for injecting a light beam whose intensity is modulated at frequency f1=fm+Δf in the optomechanical device, a photodetection device configured measure the intensity of a light beam coming out of the optomechanical device, the intensity of the measurement beam having at least one component at frequency Δf.

A system and method for performing an in-service optical time domain reflectometry test, an in-service insertion loss test, and an in-service optical frequency domain reflectometry test using a same wavelength as the network communications for point-to-point or point-to-multipoint optical fiber networks while maintaining continuity of network communications are disclosed.

This invention relates to a system and method to determine the distributed birefringence profile along an optical fibre. Birefringence manifests as different refractive indices for two orthogonal states of polarization of the light propagating in the optical fibre. The technique is based on the correlation among sets of measurements acquired using phase-sensitive optical time-domain reflectometry (φOTDR), launching light into the fibre with multiple states of polarization. The correlation between the measurements performed while sweeping the laser frequency gives a resonance (correlation) peak at a frequency detuning that is proportional to the refractive index difference between the two orthogonal polarizations. This enables measurements of the local value of the phase birefringence at any position along the optical fibre, so that longitudinal fluctuations of its value can be evaluated. Such fluctuations can be induced either accidentally during cabling and installation processes, or voluntarily due to varying conditions or environmental quantities such as temperature, strain and pressure, or even unintentionally as a result of a badly controlled manufacturing process.

A system (20) for fiber-optic reflectometry includes an optical source (28, 40), a beat detection module (52, 56) and a processor (36). The optical source is configured to generate an optical interrogation signal that is transmitted into an optical fiber (24). The beat detection module is configured to receive from the optical fiber an optical backscattering signal in response to the optical interrogation signal, and to mix the optical backscattering signal with a reference replica of the optical interrogation signal using In-phase/Quadrature (I/Q) mixing, so as to produce a complex beat signal having In-phase (I) and Quadrature (Q) components. The processor is configured to sense one or more events affecting the optical fiber by analyzing the I and Q components of the complex beat signal.

According to examples, a Brillouin and Rayleigh distributed sensor may include a first laser source to emit a first laser beam, and a second laser source to emit a second laser beam. A photodiode may acquire a beat frequency between the two laser beams. The beat frequency may be used to maintain a predetermined offset frequency shift between the two laser beams. A modulator may modulate the first laser beam. The modulated first laser beam is to be injected into a device under test (DUT). A coherent receiver may acquire a backscattered signal from the DUT. The backscattered signal results from the modulated first laser beam injected into the DUT. The coherent receiver may use the second laser beam as a local oscillator to determine Brillouin and Rayleigh traces with respect to the DUT based on the predetermined offset frequency shift.

A vibration detector and method of measuring vibration are described. The vibration detector includes an optical fiber comprising a reference reflector and a delay coil, and one or more sensors comprised at respective one or more locations in the optical fiber, each of the one or more sensors including a center reflector and two side reflectors on either side of the center reflector, the delay coil eliminating detection of interference among reflections from the one or more sensors. The vibration detector also includes a light source to introduce light into the optical fiber to interrogate the optical fiber, a detector to obtain interference signals, each of the interference signals being based on interference between reflections from the reference reflector and one of the one or more sensors; and a processor to process each of the interference signals to obtain vibration measurements.

An improved technique for acoustic sensing involves, in one embodiment, launching into a medium, a plurality of groups of pulse-modulated electromagnetic-waves. The frequency of electromagnetic waves in a pulse within a group differs from the frequency of the electromagnetic waves in another pulse within the group. The energy scattered by the medium is detected and, in one embodiment, the beat signal may be used to determine a characteristic of the environment of the medium. For example, if the medium is a buried optical fiber into which light pulses have been launched in accordance with the invention, the presence of acoustic waves within the region of the buried fiber can be detected.

One or more modal characteristics are determined for a waveguide that supports more than two modes. In an example implementation, optical frequency domain reflectometry (OFDR) is used to couple light into the waveguide and detect Rayleigh scatter reflections associated with a segment of the waveguide. An original set of Rayleigh scatter data associated with the detected Rayleigh scatter reflections is generated. In addition, a scaled set of Rayleigh scatter data associated with the detected Rayleigh scatter reflections is generated. The original set of Rayleigh scatter data is correlated with the scaled set of Rayleigh scatter data. One or more modal characteristics of the waveguide are determined based on the correlation.