A cost-effective distributed acoustic sensor using a commercial off-the-shelf DFB laser and direct detection phase-OTDR

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Development of a Pulsed Laser for Hybrid Optical Fiber Sensors for Simultaneous Distributed Temperature and Dynamic Point Measurements

In Raman based distributed or hybrid Raman/FBG optical fiber sensors, the pulsed laser source plays a key role and must be optimized in terms of output power, spectral width in order to provide high back-scattered light without coherent Rayleigh noise for suitable measurement of physical parameters. In this thesis work, a pulsed laser system for use as a source in such a hybrid fiber-optic sensing scheme has been designed, using narrowband semiconductor laser and amplifier, also considering various optimizations of the used components. The pulsed optical source has been designed specifically for hybrid Raman/FBG optical fiber sensor systems, allowing for the use of optical pulse coding to improve sensing range and static/dynamic resolution of distributed temperature & dynamic point measurements. The effectiveness of the source has been experimentally verified in this hybrid Raman/FBG sensors; the pulsed laser characteristics are also useful for other sensor schemes

Hybrid distributed optical fiber sensors for temperature, strain and vibration measurements

We describe hybrid distributed optical fiber sensor schemes for temperature, strain and vibration measurements. In particular, we first introduce the use of cyclic Simplex coding in hybrid Raman/BOTDA distributed sensors for fast long-distance strain and simultaneous temperature measurements over the same SMF, using a single narrowband source. The same advanced coding technique is also proposed to demonstrate a hybrid distributed acoustic and temperature sensor (DATS) based on Raman and coherent Rayleigh scattering processes in a standard SMF, using a single commercial off-the-shelf DFB laser and a common receiver block