In this paper a fiber optic metallic embedding technique is presented based on laser Brazing manufacturing process. The embedding strategy to follow by the laser Brazing, which consists in three steps, minimizes the thermal stress of the embedded fiber, relaxes microbending strains and reduces damage on the fiber. The minimum embedded fiber optic Ni coating total diameter is 237 μm for a successful process with negligible optical loss on the fiber. Fiber Bragg Gratings were successfully embedded in metallic specimens and their strain response was in accordance with their specifications.
We present and demonstrate a Brillouin Optical Time Domain Analysis (BOTDA) based long range sensor network with
remote switching. Two different 5 km long sections were monitored alternatively by using a fast remotely controlled and
optically powered up optical switch. The sensed fibers were located 10 km away from the interrogation unit. The
BOTDA unit uses a simplified configuration to reduce the sensor network costs. Proof-of-concept experiments were
carried out verifying the capacity of the proposed system.
KEYWORDS: Signal attenuation, Signal detection, Sensors, Signal to noise ratio, Phase measurement, Modulation, Time metrology, Precision measurement, Fiber optics sensors, Spatial resolution
We demonstrate a novel dynamic BOTDA sensor based, for the first time to our knowledge, on the use of the Brillouin
phase-shift instead of the conventional Brillouin gain. This provides the advantage of measurements that are largely
immune to variations in fiber attenuation or changes in pump pulse power. Furthermore, the optical detection deployed
can lead to an enhanced precision or measurement time and to the broadening of the measurement range.
Proof-of-concept experiments demonstrate 1.66 kHz measurement rate with 1-m resolution over a 160-m sensing fiber
length.
We present a Brillouin optical time domain analysis (BOTDA) sensor that takes advantage of the enhanced
characteristics obtained employing self-heterodyne optical detection combined with synchronous RF demodulation to
increase the sensibility of the sensor and minimize non-local effects. We also perform for the first time to our knowledge
distributed measurements of the Brillouin phase shift in an optical fiber.
We propose a hybrid network that combine point and distributed Brillouin sensors in an architecture that also deploys
remote distributed Raman amplification to extend the sensing range. A 46-km proof-of-concept network is
experimentally demonstrated integrating point vibration sensors based on fiber-optic tapers, with distributed temperature
sensing along the network bus. The sensor network with a double-bus topology offers a higher optical signal to noise
ratio and dynamic range than a single-bus for intensity point multiplexed sensors. In this network, we include low-cost
intensity sensors that are able to measure vibrations in the 0.01 to 50 Hz frequency range, which are important in the
monitoring of large infrastructures such as pipelines.
We present a solution for Brillouin optical time domain analysis (BOTDA) long-range distributed sensing that
contributes to improve considerably one of the most important problems these sensors have nowadays: the cost of the
setup. We achieve this by simplifying the process to obtain a stable frequency shift between pump and Stokes waves.
The technique we propose consist in obtaining the Stokes wave from the pump by frequency shifting in two steps: the
first one with a so-called passive Brillouin frequency shifter (BFS), and the second one by low-speed modulation.
Moreover, we demonstrate preliminary measurements of this system in typical long-range conditions, with 25km of fiber
at 1m resolution, highlighting the sensor capacity.
We demonstrate a novel configuration for Brillouin optical time domain analysis based on single-sideband modulation and RF shaping that provides pump pulses with 80 dB extinction ratio. This extremely reduced leakage, which to our knowledge is the lowest ever achieved, completely suppresses distortion of the measured spectra, thus sensor precision is enhanced. Furthermore, the proposed setup results in a simplified system with only one modulator and no need for optical filtering in detection.
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