In 2016, a novel interrogation technique for phase-sensitive (Φ)OTDR was mathematically formalized and experimentally demonstrated, based on the use of a chirped-pulse as a probe, in an otherwise direct-detection-based standard setup: chirped-pulse (CP-)ΦOTDR. Despite its short lifetime, this methodology has now become a reference for distributed acoustic sensing (DAS) due to its valuable advantages with respect to conventional (i.e., coherent-detection or frequency sweeping-based) interrogation strategies. Presenting intrinsic immunity to fading points and using direct detection, CP-ΦOTDR presents reliable high sensitivity measurements while keeping the cost and complexity of the setup bounded. Numerous technique analyses and contributions to study/improve its performance have been recently published, leading to a solid, highly competitive and extraordinarily simple method for distributed fibre sensing. The interesting sensing features achieved in these last years CP-ΦOTDR have motivated the use of this technology in diverse applications, such as seismology or civil engineering (monitoring of pipelines, train rails, etc.). Besides, new areas of application of this distributed sensor have been explored, based on distributed chemical (refractive index) and temperature-based transducer sensors. In this review, the principle of operation of CP-ΦOTDR is revisited, highlighting the particular performance characteristics of the technique and offering a comparison with alternative distributed sensing methods (with focus on coherent-detection-based ΦOTDR). The sensor is also characterized for operation in up to 100 km with a low cost-setup, showing performances close to the attainable limits for a given set of signal parameters [≈tens-hundreds of pe/sqrt(Hz)]. The areas of application of this sensing technology employed so far are briefly outlined in order to frame the technology.

Immedi ate effects of an exercise with the vocal tract semi-closed.Objective: To investigate the immediate effects of the phonation exercise in a straw in individuals with and without vocal fold lesions. Materials and Methods:Prospective study. 48 individuals, aged between 18 and 55 years participated in the study, and they were distributed into two groups: GL-with a benign vocal fold lesion; GSLwithout a lesion. The following analyses were carried out before and after the straw phonation exercises: voice self-analysis, [ε] vowel auditory-perception analysis, selected parameters acoustics (VoxMetria 2.6) and videolaryngoscopy. Results:The vocal self assessment indicated a statistically significant improvement on voice emission in GL individuals (p=0.015). There were no statistically significant differences before and after the exercise and between the groups, in the videolaryngoscopy, acoustic and auditory-perception assessments. Conclusion:The straw phonation exercise caused positive effects, seen upon voice self-assessment, indicating an easier and better voice upon phonation. Braz J Otorhinolaryngol. 2011;77(4):461-5. ORIGINAL ARTICLE BJORL

Advanced optical fiber reflectometry techniques enable spatially distributed measurements of true relative deformations over the length of a conventional optical fiber cable. This methodology is attractive for many applications ranging from intrusion monitoring to seismology. However, accurate quantification of the applied stimulus in general implies sophisticated implementations with poor sensitivity performance. Coherent reflectometry using chirped pulses is an appealing solution, as it provides fast dynamic strain measurements with a simple experimental deployment. Here, we analyze for the first time to our knowledge the lower performance bounds of this technique as a function of the signalto-noise ratio of the acquired optical signal. We demonstrate that implementations realized so far have been limited by the temporal sampling used instead of the optical signal quality. Through postprocessing interpolation approaches, we reach the performance limit for a given set of signal parameters, attaining unprecedented strain sensitivities (10 −12 ε/ÝHz) for km-length distributed sensors in conventional single-mode fibers.

Tuberculosis is a rare cause of chronic suppurative otitis media and mastoiditis; the predisposing factors of this association, however, are not commonly described. There has been an alarming increase in the incidence of tuberculosis in Brazil, including tuberculous otitis media. These patients typically present multiple perforations of the tympanic membrane, an ear discharge, and progressive hearing loss. This diagnosis should be taken into account in patients that do not respond to routine therapy for fungal external otitis or bacterial otitis media. In this retrospective study, the authors describe four cases of patients with tuberculous otitis media. This sample consisted of two physicians, a chemical engineer and an underage child in whose family there were cases of active tuberculosis. Predisposing factors for tuberculous otitis were contact with family members that had tuberculosis, professional contact with patients and exposure to pathogenic microorganisms in airways.

Phase-sensitive optical time-domain reflectometry (ΦOTDR) is a well-established technique that provides spatio-temporal measurements of an environmental variable in real time. This unique capability is being leveraged in an ever-increasing number of applications, from energy transportation or civil security to seismology. To date, a wide number of different approaches have been implemented, providing a plethora of options in terms of performance (resolution, acquisition bandwidth, sensitivity or range). However, to achieve high spatial resolutions, detection bandwidths in the GHz range are typically required, substantially increasing the system cost and complexity. Here, we present a novel ΦOTDR approach that allows a customized time expansion of the received optical traces. Hence, the presented technique reaches cm-scale spatial resolutions over 1 km while requiring a remarkably low detection bandwidth in the MHz regime. This approach relies on the use of dual-comb spectrometry to interrogate the fibre and sample the backscattered light. Random phase-spectral coding is applied to the employed combs to maximize the signal-to-noise ratio of the sensing scheme. A comparison of the proposed method with alternative approaches aimed at similar operation features is provided, along with a thorough analysis of the new trade-offs. Our results demonstrate a radically novel high-resolution ΦOTDR scheme, which could promote new applications in metrology, borehole monitoring or aerospace.