Angel Ullan

L-Band Multiwavelength Single-Longitudinal Mode Fiber Laser for Sensing Applications

In this work, a novel single-longitudinal-mode (SLM) four-wavelength laser configuration for sensing applications in the L-band is proposed and experimentally demonstrated. The sensor system presented here is based on ring resonators, and employs fiber Bragg gratings to select the operation wavelengths. The stable SLM operation is guaranteed when all the lasing channels present similar output powers. It is also experimentally demonstrated that when a SLM behavior is achieved, lower output power fluctuations are obtained. Characterization of the lasing structure for temperature sensing is also shown.

Remote (155 km) Fiber Bragg Grating Interrogation Technique Combining Raman, Brillouin, and Erbium Gain in a Fiber Laser

We present and demonstrate a technique for remote sensing of fiber Bragg gratings (FBGs) beyond 150 km. The system combines Raman, Brillouin, and erbium gain in a linear cavity fiber laser and deploys a novel heterodyne detection technique to avoid the signal-to-noise ratio limitations produced by Rayleigh scattering. Two FBGs located in series were interrogated at 155 km away from the processing unit using 0.6 W of Raman pump and less than 2 mW of Brillouin pump provided by a tunable wavelength-swept laser. Heterodyne detection brings forth a signal-to-noise ratio of approximately 10 dB in our measurements.

Temperature sensing in multiple zones based on Brillouin fiber ring laser

A simple system for sensing temperature in multiple zones based on a multi-wavelength Brillouin fiber laser ring is presented. Optical fiber reels are serially concatenated and divided in zones (one per sensing area). Setting the Brillouin lasing in each spool of fiber generates a characteristic wavelength that depends on the fiber properties and the temperature in the zone. Thus, it is possible to measure temperature independently and accurately through heterodyne detection between two narrow laser signals. The proposed sensor integrates the temperature along the whole spool of fiber in each zone. These real time measurements were successfully checked in our laboratory.

Quasi distributed hybrid Brillouin fiber laser sensor system

A hybrid quasi distributed sensing system combining point fiber Bragg gratings and long integral Brillouin scattering transducers is presented. It is able to measure global temperature changes along the sensing line as well as punctual changes at the critical locations of the structure. A 20 km proof-of-concept system has been experimentally demonstrated with a temperature resolution of 0.47 °C.

L-band multiwavelength erbium-doped fiber ring laser for sensing applications

In this work, a novel single-longitudinal-mode (SLM) four-wavelength laser configuration for sensing applications in L-band is proposed and experimentally demonstrated. This spectral region presents some advantages for the detection of dangerous gases. The sensor system presented here is based on ring resonators, and employs fiber Bragg gratings to select the operation wavelengths. The stable SLM operation is guaranteed when all the lasing channels present similar output powers. It is also experimentally demonstrated that when a SLM behavior is achieved, lower output power fluctuations are obtained.

Focal beam position detection in a laser induced breakdown spectroscopy system by using a fiber Bragg grating sensor

Chemical analysis of dangerous materials entails a safety issue for the researchers. Laser Induced Breakdown Spectroscopy offers the possibility to analyze these materials away from them using Stand-Off Set-ups. To optimize the plasma induction, the remote focalization of the laser beam is of paramount importance. A custom Fiber Bragg Grating sensor system able to correct the laser beam focalization errors is proposed and experimentally checked. The optical transducer architecture and the preliminary obtained results are reported in this paper.

Sensor System Based on a Brillouin Fiber Laser for Remote in Series Fiber Bragg Gratings Interrogation

A simple sensor system designed to monitor the temperature or strain of a certain number of critical points along a structure is presented and demonstrated. It is based on the remote interrogation of fiber Bragg gratings (FBGs) placed in series by means of a Brillouin fiber laser. Three FBGs were interrogated 50 km from the processing unit using 8 mW of Brillouin pump. Heterodyne detection brings forth a signal-to-noise ratio of approximately 40 dB in our measurements.

Application of remote power-by-light switching in a simplified BOTDA sensor network

We propose and demonstrate the use of spatial multiplexing as a means to reduce the costs of distributed sensing networks. We propose a new scheme in which remote power-by-light switching is deployed to scan multiple branches of a distributed sensing network based on Brillouin Optical Time Domain Analysis (BOTDA) sensors. A proof-of-concept system is assembled with two 5-km sensor fiber branches that are alternatively monitored using a fast remotely controlled and optically powered optical switch. The multiplexed distributed sensor fibers were located 10 km away from the interrogation unit and a Raman pump is used to remotely power the switch. Furthermore, the deployed BOTDA unit uses an alternative configuration that can lead to simplified setups.

Long integral temperature Brillouin sensor for off- shore wind energy power supply lines

A hybrid Erbium-Brillouin fiber laser sensor to measure the temperature along 22 km fiber is proposed and experimentally demonstrated. A multi-line laser oscillation is induced by the Brillouin gain of different concatenated transducer fiber sections placed in the ring cavity. Integral temperature measurements of each fiber section are obtained through each laser line. This sensor can be used to monitor the temperature of off-shore wind energy power cables.

Multi-zone temperature sensor using a multi-wavelength Brillouin fiber ring laser

A simple system for sensing temperature in multiple zones based on a multi-wavelength Brillouin fiber laser ring is presented. Optical fiber reels are serially concatenated and divided in zones (one per sensing area). Setting the Brillouin lasing in each spool of fiber generates a characteristic wavelength that depends on the fiber properties and the temperature in the zone. Thus, it is possible to measure temperature independently and accurately through heterodyne detection between two narrow laser signals. The proposed sensor integrates the temperature along the whole spool of fiber in each zone. These real time measurements were successfully checked in our laboratory.