Hybrid distributed acoustic and temperature sensor using a commercial off-the-shelf DFB laser and direct detection.

We demonstrate a hybrid distributed acoustic and temperature sensor (DATS) using a commercial off-the-shelf (COTS) distributed feedback (DFB) laser, a single-mode optical fiber, and a common receiver block. We show that the spectral and frequency noise characteristics of the laser, combined with a suitable modulation scheme, ensure the inter-pulse incoherence and intra-pulse coherence conditions required for exploiting the fast denoising benefits of cyclic Simplex pulse coding in the hybrid measurement. The proposed technique enables simultaneous, distributed measurement of vibrations and temperature, with key industrial applications in structural health monitoring and industrial process control systems.

Hybrid Raman/Brillouin-optical-time-domain-analysis-distributed optical fiber sensors based on cyclic pulse coding.

We experimentally demonstrate the use of cyclic pulse coding for distributed strain and temperature measurements in hybrid Raman/Brillouin optical time-domain analysis (BOTDA) optical fiber sensors. The highly integrated proposed solution effectively addresses the strain/temperature cross-sensitivity issue affecting standard BOTDA sensors, allowing for simultaneous meter-scale strain and temperature measurements over 10 km of standard single mode fiber using a single narrowband laser source only.

Cyclic pulse coding for fast BOTDA fiber sensors.

A cyclic pulse coding technique is proposed and experimentally demonstrated for fast implementation of long-range Brillouin optical time-domain analysis (BOTDA). The proposed technique allows for accurate temperature and strain measurements with meter-scale spatial resolution over kilometers of standard single-mode fiber, with subsecond measurement times.

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.

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.

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.

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.