Arik Bergman

Ariel University · Department of Electrical and Electronics Engineering

Forward Brillouin scattering interactions support the sensing and analysis of media outside the cladding boundaries of standard fibers, where light cannot reach. Quantitative point-sensing based on this principle has yet to be reported. In this work, we report a forward Brillouin scattering point-sensor in a commercially available, off-the-shelf mu...

The exotic physics emerging in non-Hermitian systems with balanced distributions of gain and loss has recently drawn a great deal of attention. These systems exhibit phase transitions and exceptional point singularities in their spectra, at which eigen-values and eigen-modes coalesce and the overall dimensionality is reduced. So far, these principl...

Opto-mechanical interactions in planar photonic integrated circuits draw great interest in basic research and applications. However, opto-mechanics is practically absent in the most technologically significant photonics platform: silicon on insulator. Previous demonstrations required the under-etching and suspension of silicon structures. Here we p...

Optical fibers containing multiple cores are being developed towards capacity enhancement in space-division multiplexed optical communication networks. In many cases, the fibers are designed for negligible direct coupling of optical power among the cores. The cores remain, however, embedded in a single, mechanically-unified cladding. Elastic (or ac...

The exotic physics emerging in non-Hermitian systems with balanced distributions of gain and loss has drawn a great deal of attention in recent years. These systems exhibit phase transitions and exceptional point singularities in their spectra, at which eigen-values and eigen-modes coalesce and the overall dimensionality is reduced. Among several p...

The compression of extended, coded sequences allows for laser ranging measurements with low peak power levels. Previous realizations of this approach were restricted by additive noise of direct, incoherent detection. In this work we bring together pulse sequence coding and optical coherent detection to achieve very high sensitivity. Collected seque...

We report the first realization of an anti-parity-time symmetric optical potential supporting a 2nd-order exceptional point in standard optical fibers. Phase-transition, symmetry-breaking and coalescence of supermodes are observed when Brillouin optomechanical coupling exceeds the wavenumber-mismatch.

Optical fibers containing multiple cores are being developed towards capacity enhancement in space-division multi-plexed optical communication networks. In many cases, the fibers are designed for negligible direct coupling of optical power among the cores. The cores remain, however, embedded in a single, mechanically-unified cladding. Elastic (or a...

Opto-mechanical interactions in planar photonic integrated circuits draw great interest in basic research and applications. However, opto-mechanics is practically absent in the most technologically significant photonics platform: silicon on insulator. Previous demonstrations required the under-etching and suspension of silicon structures. Here we p...

Dense wavelength division multiplexers are key components of data communication networks. This work presents a silicon-photonic eight-channel multiplexer device with a channel spacing of only 0.133 nm (17 GHz). Devices were fabricated in a commercial silicon foundry, in 8" silicon-on-insulator wafers. The device layout consists of seven unbalanced...

A range finder based on an extended sequence of coded pulses is demonstrated. Coherent detection is used to measure the range of weak point reflections, with average energy of only 0.15 photons per code symbol.

Opto-mechanical oscillators that generate coherent acoustic waves are drawing much interest, in both fundamental research and applications. Narrowband oscillations can be obtained through the introduction of feedback to the acoustic wave. Most previous realizations of this concept, sometimes referred to as "phonon lasers", relied on radiation press...

Brillouin-Enhanced Four-Wave-Mixing techniques, which couple four optical beams through Brillouin nonlinearity, have gained popularity in the 1980’s largely owing to their phase conjugation properties. Experiments were mainly conducted in liquid cells. The interest in Brillouin-Enhanced Four-Wave-Mixing has reawakened in the 2000’s, following the q...

Brillouin-Enhanced Four-Wave-Mixing techniques, which couple four optical beams through Brillouin nonlinearity, have gained popularity in the 1980's largely owing to their phase conjugation properties. Experiments were mainly conducted in liquid cells. The interest in Brillouin-Enhanced Four-Wave-Mixing has reawakened in the 2000's, following the q...

Opto-mechanical oscillators that generate coherent acoustic waves are drawing much interest, in both fundamental research and applications. Narrowband oscillations can be obtained through the introduction of feedback to the acoustic wave. Most previous realizations of this concept, sometimes referred to as "phonon lasers", relied on radiation press...

Highly nonlinear waveguides are fabricated through deposition of chalcogenide glass into pre-patterned trenches in a silica cladding. No processing of the chalcogenide glass is required. Four-wave mixing is demonstrated with nonlinear coefficient of 6.5±1 [W×m]−1.

Point analysis of forward stimulated Brillouin scattering is demonstrated for the first time, using a Bragg grating in a multi-core fiber. Measurements distinguish between air and water outside a cm-scale fiber section.

This paper presents the application of distributed fiber optic strain sensing as a standard procedure for airworthiness assessment of an entire fleet of operational High Altitude Long Endurance (HALE) Unmanned Aerial Vehicles (UAVs) during service. The Rayleigh-backscattering-based sensing concept is applied to a standard optical fiber, which is em...

We demonstrate a novel distributed fiber sensing technique with a record broadband sensitivity of 10nƐ/√Hz at a sampling rate of 1MHz. A standing acoustic wave is generated by all-optical excitation of two simultaneously counter-propagating Brillouin dynamic gratings. A dual-tone readout probe pulse is used for the distributed measurement of strain...

A novel technique combining Brillouin phase-shift measurements with Brillouin dynamic gratings (BDGs) reflectometry in polarization-maintaining fibers is presented here for the first time. While a direct measurement of the optical phase in standard BDG setups is impractical due to non-local phase contributions, their detrimental effect is reduced b...

Probe coding can significantly improve the signal to noise ratio and measurement speed in Brillouin Dynamic Grating (BDG) fiber-optic distributed sensing, but only if coherent reception is employed. This is because both the amplitude and phase of the BDG impulse response vary along the fiber due to fiber non-uniformities, as well as the effect of t...

An add-on amplifying module is presented, capable of significantly extending the measurement dynamic range of fiber-optic distributed strain/temperature interrogators, which are based on Rayleigh backscattering and Optical Frequency-Domain Reflectometry (OFDR). Since Rayleigh backscattering in single-mode optical fibers is very weak, any optical lo...

Digital pulse compression was used to enhance the performance of optical time-domain reflectometry, employing Brillouin dynamic gratings (BDGs) in polarization-maintaining fibers. The fundamental and unique issues in BDG field-reflection are addressed, and rules for proper selection of the coding and detection techniques are formulated. While codin...

A hybrid, low cost HUMS concept, based on fiber-optic point and distributed strain sensing for both usage monitoring and damage detection, is presented. Sensing is based on in-flight Fiber Bragg Grating (FBG) technology, combined with on-ground Rayleigh-backscattering distributed strain sensing. The in-flight FBG instrumentation monitors loads and...

We present a novel fiber-optic sensing technique based on the distributed measurement of Brillouin-induced phase-shift in the reflection from Brillouin dynamic gratings in polarization-maintaining fibers. Subject to signal to noise considerations, the strain sensitivity of the phase-shift in the reflection of a pulsed probe, orthogonally polarized...

The ability of Brillouin-based fiber-optic sensing to detect damage in a moving cantilever beam is demonstrated. A fully computerized, distributed and high spatial resolution (10cm) Fast-BOTDA interrogator (50 full-beam Brillouin-gain-spectra per second) successfully directly detected an abnormally stiffened (i.e., ‘damaged’) 20cm long segment in a...

This paper presents the application of distributed fiber optic strain sensing to commercial aircraft composite fuselage panels for load monitoring and impact detection. This work is part of the EU SARISTU project aimed at enhancing the technology of Smart Intelligent Aircraft Structures. One aspect of Smart Intelligent Aircraft Structures is applyi...

In recent years, in order to ensure safe operation of UAVs, especially over populated areas, the industry has moved towards establishing airworthiness requirements like the STANAG 4671, based on commercial manned aircraft airworthiness regulations. An attractive option towards maintaining structural integrity is the utilization of Structural Health...

One of the leading methods for high-spatial resolution, though semi-static distributed strain sensing in optical fibers makes use of Rayleigh backscattering, as measured by the coherent Optical Frequency-Domain Reflectometry (OFDR) technique. OFDR uses swept wavelength interferometry to measure the complex optical transfer function of the fiber und...

Brillouin Dynamic Gratings (BDGs) are optically generated longitudinal density (acoustic) waves in optical fibers, whose strength depends on the intensity of the counter-propagating pumping signals and the electrostrictive properties of the interaction medium. Since it was first introduced in 2008, the manipulation of BDGs in optical fibers was dem...

We present a novel technique that advantageously combines both Stokes and anti-Stokes reflections from counter-propagating BDGs in optical fibers, allowing distributed phase-shift measurement with high spatial resolution and immune to variations in fiber birefringence.

Spontaneous Brillouin backscattering, which accompanies the operation of Brillouin Dynamic Gratings (BDG) sensors, is experimentally investigated for the anti-stokes configuration, where the probe wave propagates against the orthogonally polarized high frequency writing pump. Even in the absence of the low frequency writing pump but for a strong en...

The performance of optical time-domain sensing technique, employing the slope of Brillouin dynamic gratings in polarization-maintaining fibers, is significantly enhanced using coherent pulse compression techniques. The strain sensitivity of the reflectivity of a coded probe, orthogonally polarized to the pumps which generated the grating, depends o...

Embedded fiber-optic strain sensing networks for airworthy assessment of operational Unmanned Aerial Vehicles (UAVs) are presented. Sensing is based on in-flight fiber Bragg grating technology, as well as on on-ground Rayleigh-backscattering distributed strain sensing. While the in-flight instrumentation monitors loads, looking for excessive values...

For fiber optic sensors to be integrated in aerospace structures and for these sensors to provide data that can be used for structural health monitoring (SHM), development work has been performed in the SARISTU project. This particular chapter describes the inclusion of fiber optic sensors in a tape format, called ribbon tape, for damage detection...

This paper presents the application of distributed fiber optic strain sensing as a standard procedure for airworthiness assessment of an entire fleet of operational High Altitude Long Endurance (HALE) Unmanned Aerial Vehicles (UAVs) during service. The Rayleigh-backscattering-based sensing concept is applied to a standard optical fiber, which is em...

An overview is presented of recent progress in dynamic and distributed Brillouin-based fiber-optic sensing, culminating in sampling speeds, limited only by the fiber length.

A new fast and distributed optical time-domain sensing technique, employing the slope of Brillouin dynamic gratings in polarization-maintaining fibers, is proposed and demonstrated. The strain sensitivity of the reflectivity of a pulsed probe, orthogonally polarized to the pumps, which generated the Brillouin dynamic grating, is found to be practic...

The performance of an optical time-domain sensing technique, employing the slope of Brillouin dynamic gratings in polarization-maintaining fibers, can be significantly enhanced using Golay complementary sequences. The strain sensitivity of the reflectivity of a coded probe primarily depends on the detuning between the orthogonally polarized pumps,...

We present an add-on technique to improve the power budget of fiber-optic strain interrogators, based on Rayleigh backscattering and Optical Frequency-Domain Reflectometry (OFDR). Since backscattering in single-mode optical fibers is very weak, any optical loss along the sensing fiber, originating from bending, embedding and/or bad connectors, may...

This work presents an innovative Structural Integrity Monitoring concept based on embedded optical fiber distributed Rayleigh back-scattering strain sensing. The UAV wing main spar strain distribution, under load, was recorded periodically during service. These strain measurements were analyzed and compared to a baseline record in order to identify...

An overview of recent progress in the field of distributed fiber-optic sensors based on stimulated Brillouin scattering (SBS) is presented. SBS sensors provide distributed measurements of temperature and strain, in which every segment of standard fiber serves as a sensing element. The fundamental measurement configuration was first proposed in the...

A representing damaged UAV wing spar cap was repaired using bonded unidirectional composite materials. For such a repair concept, its strength and long-term durability depend on optimizing the geometry of the repair in order to minimize stress concentration in the adhesive. In order to assess the stress distribution along the repair bond-line, an o...

A new fast and distributed optical time-domain sensing technique, employing the slope of Brillouin dynamic gratings (BDG) in polarization-maintaining (PM) fibers, is proposed and demonstrated. The strain sensitivity of the reflectivity of a pulsed probe, orthogonally polarized to the pumps which generated the BDG, is shown to depend on both pump an...

An acousto-optic cell consists of an interaction material to which a piezoelectric transducer is bonded. The transducer launches a compression wave into the material which in turn, creates a strain wave. The strain wave leads to density changes in the interaction medium and consequently, to index of refraction changes. Light passing through the aco...