In this work, we present an enhanced design for a Brillouin Ring Laser (BRL) based on a doubly-resonant cavity (DRC) with short fiber length, paired with a heterodyne-based wavelength-locking system, to be employed as pump-probe source in Brillouin sensing applications. The enhanced source is compared with the long-cavity (LC) (~ 2 km) BRL pump-probe source that we have recently demonstrated, showing a significantly lower relative intensity noise (~-145 dB/Hz in the whole 0-800 MHz range), a narrower linewidth (10 kHz), combined with large tunability features and an excellent pumpprobe frequency stability (~200 Hz) which is uncommon for fiber lasers. The measurement of intensity noise on the novel BRL signal yielded an improved signal-to-noise ratio (SNR) of about 22 dB with respect to LC-BRL schemes that is expected to lead to a temperature/strain resolution enhancement in BOTDA applications up to 5.5 dB.
Brillouin distributed optical fiber sensors have proved to be a powerful technology for real-time detection of strain and temperature. In such sensors the optical fiber is interrogated along its full length with a resolution down to decimeters and a frequency-encoding of the measurement data that is not affected by variation of the optical attenuation. The fiber sensing cable plays a key role, since it must provide accurate strain transfer, robustness and durability. In this paper, a novel, suitably designed fiber cable for achieving optimal strain measurement performance is presented. The concept and development phases are illustrated, together with results on the strain transfer capability.
In this work, we present an enhanced design for a Brillouin Ring Laser (BRL) based on a doubly-resonant cavity (DRC) with short fiber length, paired with a heterodyne-based wavelength-locking system, to be employed as pump-probe source in Brillouin sensing applications. The enhanced source is compared with the long-cavity (LC) (~ 2 km) BRL pump-probe source that we recently demonstrated, showing a significantly lower relative intensity noise (~ -145 dB/Hz in the 0-800 MHz range), a narrower linewidth (10 kHz), combined with large tunability features and an excellent pumpprobe frequency stability (~200 Hz) which is uncommon for fiber lasers. The measurement of intensity noise on the novel BRL signal yielded an improved signal-to-noise ratio (SNR) of about 22 dB with respect to LC-BRL schemes that is expected to lead to a temperature/strain resolution enhancement in BOTDA applications up to 5.5 dB.
In this work we report the results of a theoretical and experimental study that we have carried out on a Brillouin optical time domain analysis (BOTDA) sensing scheme using a novel low-noise actively-stabilized fiber Brillouin ring laser (BRL) as probe source. The BRL laser is based on a short-cavity (SC), < 4 meters long, layout achieving double-resonance (DR) operation for both pump and probe signals; an active wavelength-locking circuit is used to stabilize the signal and tune the signal frequency over a range of ̴ 200 MHz range. The wavelength-locked SC-DR BRL shows spectral linewidth of approximately 10 kHz and RIN values of ~-145 dB/Hz across the (0-600) MHz range; pump-probe frequency shift can be efficiently tuned across the entire Brillouin gain spectrum of the sensing fiber with sub-kHz precision (200 Hz) and high temporal stability for timescale of BOTDA measurements (more than 100 ms). A preliminary BOTDA measurement using a wavelength-locked long-cavity (LC) BRL yielded a Brillouin frequency shift (BFS) uncertainty of 1,5 MHz corresponding to temperature and strain sensitivity values of 1 K and 25 με, respectively, and a spatial resolution of 5 m for 50 ns-long pump pulses.
In this paper we show a Brillouin optical time-domain analysis (BOTDA) sensing system experiment employing a tunable narrow-linewidth dual pump-probe source based on modified Brillouin ring laser technology. The developed cost-effective source generates a pump-locked and tunable probe light, with wavelength shift and a large tuning range (~200 MHz), narrow linewidth (<2.5 MHz) and adequate power (~0.5 mW). The developed source was hence employed in BOTDA system experiments providing distributed sensing over ~10 km single mode optical fiber, and attaining strain and temperature resolutions of ~10με and ~0.5 °C respectively, indicating the pump-probe source as an efficient and cost-effective solution for BOTDA avoiding high-frequency signal generators or complex locking techniques.
We present a tunable narrow-linewidth dual pump-probe optical source based on modified Brillouin ring laser technology aimed at Brillouin-based sensing. The developed source exhibits a narrow linewidth and allows for a large tuning range, attaining <2.5 MHz bandwidth, ~200 MHz tuning range and ~0.5 mW power, thus constituting an efficient and cost-effective solution for sensing interrogators.
In this work we report the results of both theoretical and experimental strain analysis of Silicon waveguides and
couplers. Simulations of induced stress and strain distributions on photonic structures (waveguides with 450 × 220 nm
cross section) have been performed taking into account a ~375 nm thick Si3N4 straining layer. The Convergent Beam
Electron Diffraction (CBED) technique has also been employed to provide locally accurate strain measurements on
fabricated silicon rib and coupling structures across the nitride-to-silicon interface, showing a good match between
multiphysics simulations and measurements along the rib cross-section, resulting in notable attained strain levels.
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