J. Subías

High resolution light intensity spectrum analyzer (LISA) based on Brillouin optical filter

A high-resolution light intensity spectrum analyzer technique to derive the RF modulation spectrum of optical signals is presented and experimentally confirmed. It uses the XPM nonlinear effect in a dispersion shifted fiber to obtain the light intensity spectrum, and a Brillouin optical filtering method to implement the high resolution spectrometric analysis. Measured RF spectra of PRBS modulated optical signals at 2.5 Gb/s and 10 Gb/s are presented and compared with their corresponding ones obtained in the electrical detection domain to confirm the capabilities of the method.Influence of fiber electrostriction effect is measured and analyzed.

All in fiber optical frequency metrology by selective Brillouin amplification of single peak in an optical comb.

Suitable use of stimulated Brillouin amplification (SBA) effect for selective single peak amplification in an optical frequency comb is demonstrated to provide high accuracy in optical frequency metrology. A pump wave generated by a tunable laser source (TLS) is used to stimulate SBA of such optical comb along an optical fiber and selectively amplify only one single peak of the comb. Nature of SBA preserves both linewidth and absolute wavelength position of the selected comb peak. All of these features result in a simple, robust and compact all in fiber system. Relative optical frequency accuracy in the order of Hz is confirmed.

Brillouin induced self-heterodyne technique for narrow line width measurement

A novel technique is introduced for jitter-insensitive sub-KHz resolution linewidth characterization technique in ultra-narrow lasers for optical communication applications. The technique is based on self-heterodyne detection induced by Stimulated Brillouin Scattering (SBS). Non linear SBS drives the heterodyne mixing through optical frequency locking of a narrow tunable laser source and the signal under test, which is modulated in the low frequency range. Due to SBS nature, jitter variations in the optical frequency do not affect the correlation spectra measured with resolution figures up to 300 Hz, without the need for optical delay line as in conventional homodyne correlation techniques.

Subpicometer wavelength accuracy with gain-switched laser diode in high-resolution optical spectrometry

We present a method to generate an optical reference comb signal with subpicometer wavelength accuracy. XPM nonlinear effect in a fiber is used to get an optical frequency comb signal, free of frequency chirp and wavelength instabilities, from a pulsed gain-switched laser diode. Principles of such comb generation are presented as well as the application of this comb as a ruler to measure frequency differences in high resolution optical spectrum measurements. To confirm this method, Brillouin filtering optical spectrometric technique is used to characterize a modulated optical source. Typical resolution of this technique allows 0.08 pm wavelength accuracy.

BIDIMENSIONAL PLANAR MICRO-OPTICS FOR OPTOCHEMICAL ABSORBANCE SENSING

A new approach for developing optochemical absorbance sensors is presented. The method is based on a planar micro-optic circuit in which an optochemically active membrane that responds to selective compounds is deposited in the device, yielding a part of the guiding planar structure. In this way the optical field is confined in the direction transverse to the substrate and controlled in the lateral direction by means of planar micro-optics components. High sensitivity of the device can be easily obtained because of the relatively long light paths through the membrane, and the response time is low because the analyte has to diffuse through a several-micrometer-thin membrane. Experimental results of measurements of the concentration of potassium are also presented to verify the possibilities of these devices as specific absorbance sensors.

Direct measurement of frequency and polarization dependences of cross-phase modulation in fibers from high-resolution optical spectra

We present the results of an experiment for frequency and polarization dependence characterization of non-linear cross-phase-modulation (XPM) effects in optical fibers. The measurement technique is based on the direct analysis of high-resolution optical spectra of a signal wave that is phase modulated by an intensity-modulated pump wave. Measurement results provide experimental confirmation of the scalar character, over the whole resonant frequency range, of the electrostrictive contribution to the nonlinear refractive index. Also, the results confirm experimentally the relation describing the polarization dependence of the Kerr contribution to XPM in non-polarization-maintaining fibers.

Carcinoma neuroendocrino de oído medio

This case was of a 42-year-old male who presented a 5-year history of sensation of hearing loss and tinnitus in the right ear. Otoscopy revealed a non-pulsatile bulge of the tympanic membrane. In audiometry testing, he had a fall in high-pitched sounds from 2000 Hz onwards. Initial diagnosis was set as congenital cholesteatoma or glomus. Magnetic resonance imaging (MRI) revealed a hypercapturing mass that occupied the entire tympanic membrane, antrum and attic, compatible with possible tympanic glomus. In the computed tomography (CT) of the petrous portion of the temporal bone, no bone erosions surrounding the ossicular structures were seen (Fig. 1). It was decided to carry out a tympanoplasty and a slightly bleeding, purplish-red mass was found in the operation. Anatomopathological study indicated a neoformation with hyperchromatic cell groups and eosinophilic cytoplasm; the immunohistochemical study was positive for AE1-AE3, CAM5.2, chromogranin and synaptophysin (Fig. 2). The diagnosis was neuroendocrine carcinoma of low-grade activity. The possibility that it was a secreting tumour was posed to the Internal Medicine Service at this hospital. The X-ray study and that of the tumour markers (carcinoembryonic