Combinazione coerente di dati SAR per analisi tomografiche

In questo lavoro è stato sviluppato uno stimatore operante su dati tomografico differenziali a singolo look in grado di estrarre informazioni su : quota, velocità ed accelerazione degli scatteratori presenti nello scenario, con elevata risoluzione.L'algoritmo di stima e' stato testato su modelli semplici a 2 e 3 scatteratori con varie combinazioni dei parametri quota , velocità ed accelerazione

Integrated hybrid Raman/fiber Bragg grating interrogation scheme for distributed temperature and point dynamic strain measurements

We propose and experimentally demonstrate the feasibility of an integrated hybrid optical fiber sensing interrogation technique that efficiently combines distributed Raman-based temperature sensing with fiber Bragg grating (FBG)-based dynamic strain measurements. The proposed sensing system is highly integrated, making use of a common optical source/receiver block and exploiting the advantages of both (distributed and point) sensing technologies simultaneously. A multimode fiber is used for distributed temperature sensing, and a pair of FBGs in each discrete sensing point, partially overlapped in the spectral domain, allows for temperature-independent discrete strain measurements. Experimental results report a dynamic strain resolution of 7.8  nε/√Hz within a full range of 1700 με and a distributed temperature resolution of 1°C at 20 km distance with 2.7 m spatial resolution

Raman-based distributed temperature sensor with 1 m spatial resolution over 26 km SMF using low-repetition-rate cyclic pulse coding

We experimentally investigate the benefits of a new optical pulse coding technique for long-range, meter and submeter scale Raman-based distributed temperature sensing on standard single-mode optical fibers. The proposed scheme combines a low-repetition-rate quasi-periodic pulse coding technique with the use of standard high-power fiber lasers operating at 1550 nm , allowing for what we believe is the first long-range distributed temperature measurement over single-mode fibers (SMFs). We have achieved 1 m spatial resolution over 26 km of SMF, attaining 3°C temperature resolution within 30 s measurement time

Current Status and Future Trends of Photonic-Integrated FBG Interrogators

In this paper, we present an overview of the current efforts toward integration on chip of fiber Bragg grating (FBG) sensor interrogators. Different photonic-integration platforms are discussed, including monolithic planar lightwave circuit technology, silicon on insulator (SOI), indium phosphide, and gallium arsenide material platforms. Furthermore, various possible techniques for wavelength metering and methods for FBG multiplexing are discussed and compared in terms of resolution, dynamic performance, multiplexing capabilities, and reliability. The use of linear filters, array waveguide gratings (AWG) as multiple linear filters, and AWG-based centroid signal processing techniques are presented as well as interrogation techniques based on tunable microring resonators and Mach-Zehnder interferometers for phase sensitive detection. FBG sensor interrogation based on SOI platform using active and passive phase sensitive detection is also described, demonstrating specifically the potential of passive phase demodulation for high-speed dynamic strain measurements. This paper finally presents the challenges and perspectives of photonic integration to address the increasing requirements of several industrial applications

High-performance Raman-based distributed fiber-optic sensing under a loop scheme using anti-stokes light only

A distributed fiber-optic temperature sensor technique inherently allowing for system calibration, compensating time-dependent variations of the fiber losses as well as local external perturbations, is proposed using a loop-scheme together with Raman anti-Stokes-only measurement. A temperature resolution enhancement with respect to a standard loop configuration is shown by experiments, providing a robust and reliable high-performance sensing technique for long sensing ranges. © 2006 IEEE

Fiber Bragg grating sensor interrogators on chip: Challenges and opportunities

In this paper we present an overview of the current efforts towards integration of Fiber Bragg Grating (FBG) sensor interrogators. Different photonic integration platforms will be discussed, including monolithic planar lightwave circuit technology, silicon on insulator (SOI), indium phosphide (InP) and gallium arsenide (GaAs) material platforms. Also various possible techniques for wavelength metering and methods for FBG multiplexing will be discussed and compared in terms of resolution, dynamic performance, multiplexing capabilities and reliability. The use of linear filters, array waveguide gratings (AWG) as multiple linear filters and AWG based centroid signal processing techniques will be addressed as well as interrogation techniques based on tunable micro-ring resonators and Mach-Zehnder interferometers (MZI) for phase sensitive detection. The paper will also discuss the challenges and perspectives of photonic integration to address the increasing requirements of several industrial applications

Distributed optical fiber temperature sensor using only anti-Stokes Raman scattering light in a loop configuration

In this paper we demonstrate distributed Raman temperature sensing (RDTS) in a loop scheme employing anti-Stokes light intensity only. Using a single-channel receiver and anti-Stokes traces measured in loop configuration, we implement RDTS with inherent compensation of fiber wavelength-dependent losses, as well as local external perturbations. Experimental results show a signal-to-noise ratio enhancement with respect to a standard RDTS in loop configuration, providing a robust and reliable high-performance sensor for long sensing ranges. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE)