Bipolar pulse coding for enhanced performance in Brillouin distributed optical fiber sensors

We propose and experimentally demonstrate the possibility to use a pump signal based on bipolar pulse sequences using single-sideband suppressed-carrier (SSB-SC) modulation in Brillouin optical time-domain analysis (BOTDA) sensors. The SSB-SC modulated pump makes a sequential use of the Brillouin gain and loss spectra, increasing the intensity contrast of the measurements. The method is demonstrated using bipolar Golay codes along a 50 km sensing fiber and 2 m spatial resolution. Results indicate that the use of bipolar sequences provides a higher SNR enhancement and stronger robustness to pump depletion in comparison to BOTDA systems employing conventional unipolar sequences

Bipolar optical pulse coding for performance enhancement in BOTDA sensors

A pump signal based on bipolar pulse coding and single-sideband suppressed-carried (SSB-SC) modulation is proposed for Brillouin optical time-domain analysis (BOTDA) sensors. Making a sequential use of the Brillouin gain and loss spectra, the technique is experimentally validated using bipolar complementary-correlation Golay codes along a 100 km-long fiber and 2 m spatial resolution, fully resolving a 2 m hot-spot at the end of the sensing fiber with no distortion introduced by the decoding algorithm. Experimental results, in good agreement with the theory, indicate that bipolar Golay codes provide a higher signal-to-noise ratio enhancement and stronger robustness to pump depletion in comparison to optimum unipolar pulse codes known for BOTDA sensing

Time/frequency coding for Brillouin distributed sensors

In this paper, we propose a novel coding for long range Brillouin Optical Time Analysis (BOTDA) distributed sensors based on a combination of time and frequency pulses, resulting in an additional coding gain of √2 with respect to traditional intensity-modulated codes. The generation of frequency-chirped pseudo-arbitrary pulses in return-to-zero (RZ) format with a Direct-Digital Synthesizer (DDS) is presented and the coding gain is experimentally verified, perfectly matching its theoretical value

Audit about Medical Decision: Data Transmission Concerning Patients with Dementia Entering French Nursing Homes Does Not Confirm the Diagnosis

Background. Dementia was affecting 855.000 patients in France in 2007. Lanmeur's rural hospital population was representative of the French nursing home's population. The followup was assumed by local GPs, which is also usual care in France for nursing homes. The study looked at clinical and paraclinical data transmitted at the institutionalization time of patients suffering from dementia. Aim. showing that admission letters did allow establishing a diagnosis of dementia for the GPs. Method. we included all patients with dementia at the time of institutionalization between July 2000 and July 2007. We searched in the admission letters for 25 criteria extracted from the French guidelines for dementia and Alzheimer disease diagnosis (multiple cross-sectional analysis per year). Results. 293 patients were included. The median number of diagnostic criteria present in the letters of admission is 1 (first quartile: zero, third quartile: 4, and maximum: 12). Conclusions. the data in admission letters did not allow the diagnosis of dementia according to the French guidelines. We know that dementia is underchecked and undertreated in France according to the same guidelines. What consequences did this lack of basic data give on motivation for treatment and recurrent diagnosis process for GPs? This has to be evaluated

Compact fibre Bragg grating-based thermometer for on-line temperature monitoring of drill bits

In this communication, a novel compact fibre Bragg grating-based thermometer for on-line temperature monitoring of drill bits is reported. Our proposed technique can potentially be used to optimize any drilling process, requiring the use of small drill bits, through direct temperature measurement at the drill bit instead of relying on indirect parameters (speed of rotation, applied force) in order to avoid an overheating as it is currently done nowadays

Dual-pump sweep-free stimulated Brillouin optical distributed sensing method and device

The present invention concerns a Brillouin optical distributed sensing method, comprising steps of: (i) providing a first and a second optical pulsed pump wave (20, 23) and an optical probe wave comprising at least one probe spectral component (26), (ii) detecting a stimulated Brillouin scattering signal resulting from the interactions in a sensing optical fiber of the optical probe wave with the first and the second optical pulsed pump waves (20, 23), (iii) spectrally arranging the first and the second optical pulsed pump waves (20, 23) and the optical probe wave so that the optical probe wave comprises a probe spectral component (26) located within the Stokes Brillouin spectrum (21) of the first optical pulsed pump wave (20) and a probe spectral component (26) located within the anti-Stokes Brillouin spectrum (24) of the second optical pulsed pump wave (23), (iv) deducing the Brillouin frequency (22, 25) of the Brillouin spectra (21, 24) from the stimulated Brillouin scattering signal. The present invention concerns also a device for implementing the method

Differential chirped-pulse pair for sub-meter spatial resolution Brillouin distributed fiber sensing

A distributed fiber sensor based on a differential chirped-pulse pair Brillouin optical time domain analysis (DCPBOTDA) is proposed for sub-meter spatial resolution sensing. The technique is based on the subtraction of two measurements made with the same pump pulse widths, but differing in the final short section of the pulse by a positive or negative frequency chirp, respectively. Experimental results are compared with a precise theoretical modeling, validating the sub-meter sensing capabilities of the technique