Farhan Zaidi

Hybrid Raman/fiber Bragg grating sensor for distributed temperature and discrete dynamic strain measurements

We propose and experimentally demonstrate a hybrid fiber optic sensing technique that effectively combines Raman optical time domain reflectometry and in-line time-division-multiplexing for fiber Bragg grating (FBG) dynamic interrogation. The highly integrated proposed scheme employs broadband apodized low reflectivity FBGs with a single narrowband optical source and a shared receiver block, allowing for simultaneous measurements of distributed static temperature and discrete dynamic strain, over the same sensing fiber.

Hybrid BOTDA/FBG sensor for discrete dynamic and distributed static strain/temperature measurements

We propose and experimentally demonstrate a hybrid fiber optic sensing technique that effectively combines Brillouin optical time-domain analysis and a time-domain multiplexing interrogation technique for Fiber Bragg Gratings (FBGs). The highly-integrated proposed scheme employs broadband apodized low-reflectivity FBGs with a single optical source and a shared receiver block, allowing for simultaneous measurements of distributed static and discrete dynamic temperature and strain, over the same sensing fiber.

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.

High-performance hybrid Raman/fiber Bragg grating fiber-optic sensor based on simplex cyclic pulse coding

We propose and experimentally demonstrate the use of cyclic pulse coding to improve the performance of hybrid Raman/fiber Bragg grating (FBG) fiber-optic sensors, for simultaneous measurement of distributed static temperature and discrete dynamic strain over the same sensing fiber. Effective noise reduction is achieved in both Raman optical time-domain reflectometry and dynamic interrogation of time-division-multiplexed fiber FBG sensors, enhancing the sensing range resolution and providing real-time point dynamic strain measurement capabilities. The highly integrated sensor scheme employs broadband apodized low-reflectivity FBGs, a single narrowband optical source, and a shared receiver block.

High Performance Time Domain FBG Dynamic Interrogation Scheme Based on Pulse Coding

A novel method to improve the measurement range, resolution, and multiplexing capability of time division multiplexed (TDM) fiber Bragg grating (FBM) sensors, based on advanced cyclic pulse coding, is proposed and experimentally demonstrated. The mechanism of noise reduction by quasi-periodic cyclic coding is quantitatively demonstrated, pointing out significant improvement in dynamic strain resolution with respect to single pulse TDM FBG interrogation. The use of cycling pulse coding allows for enhanced dynamic performance of real time strain measurement with respect to other coding techniques. The proposed technique can also enhance the sensing range of hybrid optical fiber sensor systems in which continuous static temperature/strain distributions and discrete dynamic strain in specific critical points are simultaneously measured over the same sensing fiber.

Advanced Coding Techniques for Long-Range Raman/BOTDA Distributed Strain and Temperature Measurements

We describe the use of pulse coding for long-range distributed Raman and Brillouin optical time domain analysis (BOTDA) sensors and for implementing hybrid Raman/BOTDA distributed sensors for simultaneous strain and temperature measurement on the same fiber.

Advanced hybrid BOFDA/FBG sensor system for simultaneously point-wise and distributed temperature/strain measurements

We propose and experimentally demonstrate for the first time to the best of our knowledge the feasibility of an integrated hybrid optical fiber sensing system that efficiently combines distributed Brillouin optical frequency-domain analysis (BOFDA) technique with FBG-based quasi-distributed approach offering the possibility for simultaneous distributed and point-wise measurements. The highly integrated proposed scheme employs Gaussian shaped, broadband and low reflectivity apodized FBGs with a common narrow-band optical source and shared receiving unit over the same sensing fiber. A single mode optical fiber is used for distributed sensing and a pair of FBGs is employed for simultaneous pointwise measurements.

Hybrid Fiber Optic Sensors for Simultaneous Distributed and Dynamic Discrete Measurement

Hybrid sensing is becoming a key technology in application fields requiring simultaneous distributed temperature and discrete strain measurements. Two hybrid fiber optic sensing techniques effectively combining Raman and FBG-based sensing are presented in this paper.

Hybrid Raman/FBG-based sensing for simultaneous point dynamic strain and distributed temperature measurement

We propose and experimentally demonstrate an integrated hybrid optical fiber sensing technique that combines distributed Raman-based temperature measurements with a time-domain approach for FBG dynamic interrogation using a shared optical source and receiver block.

High performance fiber optic sensor based on self referenced FBGs and high-speed dual-wavelength pulse coding

We propose and experimentally demonstrate the feasibility of a highly efficient FBG-based quasi-distributed sensing system employing dual-wavelength cyclic pulse coding. Significant improvement in the measurement range, resolution and TDM multiplexing capabilities can be achieved, as well as crosstalk reduction with respect to a single wavelength TDM-based FBG interrogation scheme. The mechanism of noise reduction by quasi-periodic cyclic coding is experimentally demonstrated, pointing out significant improvement in accuracy with respect to dual-wavelength single pulse TDM-based FBG interrogation. The proposed technique can also enhance the sensing range of hybrid fiber optic sensor systems in which continuous monitoring of distributed and discrete points are simultaneously measured over the same sensing fiber.