Abstract
The electric arc technique is used to apodize fiber Bragg gratings (FBGs). Arc discharges applied to the ends of the grating produce a smoothing of the refractive-index modulation profile reducing the sidelobes of the reflection spectrum at longer wavelengths. A sidelobe reduction of 17 dB was obtained. (c) 2007 Wiley Periodicals, Inc.

Abstract
The thermal behavior of long-period gratings arc-induced in B/Ge codoped fibers is presented. We also demonstrated the possibility to erase gratings written in Ge-doped and B/Ge codoped fibers through uniform exposure to UV-laser radiation. The gratings spectra were afterward recovered by thermal annealing. permanent thermally induced refractive index changes were found. (C) 2007 Wiley Periodicals, Inc.

Abstract
OTDM-to-WDM conversion from 128.1 Gbit/s to 3x42.7Gbit/s is achieved by wavelength conversion using side filtering of SPM broadened spectrum in HNLF, followed by a single electro-absorption modulator based optical gate. A maximum 2dB penalty was achieved. (C) 2008 Optical Society of America.

Abstract
Integrated optics is a mature technology with standard applications to telecommunications. Since the pioneering work of Berger et al. 1999 beam combiners for optical interferometry have been built using this technology. Classical integrated optics device production is very expensive and time consuming. The rapid production of devices using hybrid sol-gel materials in conjunction with UV laser direct writing techniques allows overcoming these limitations. In this paper this technology is tested for astronomical applications. We report on the design, fabrication and characterization of multiaxial two beam combiners and a coaxial beam combiner for astronomical interferometry. Different multiaxial two beam combiner designs were tested and high contrast (better than 90%) was obtained with a 1.3 mu m laser diode and with an SLID (lambda(0) = 1.26 mu m, FWHM of 60 nm). High contrast fringes were produced with 1.3 mu m laser diode using the coaxial two beam combiner. These results show that hybrid sol-gel techniques produce devices with high quality, allowing the rapid prototyping of new designs and concepts for astronomy.

Abstract
We derive the time-variant second-order statistics of the depth-scan photocurrent in time-domain optical coherence tomography (TD-OCT) systems using polarized thermal light sources and superluminescent diodes (SLDs). Since the asymptotic-joint-probability-distribution function (JPDF) of the photocurrent due to polarized thermal light is Gaussian and the signal-noise-ratio in TD-OCT is typically high (> 80 dB), the JPDF of the depth-scan photocurrent could be approximated as a Gaussian random process that is completely determined by its second-order statistics. We analyze both direct and differential light detection schemes and include the effect of electronic thermal fluctuations. Our results are a necessary prerequisite for future development of statistical image processing techniques for TD-OCT. (c) 2007 Optical Society of America.

Abstract
Femtosecond Titanium: sapphire lasers can deliver high average power broadband spectra in a high quality beam, being therefore an optical source of choice for high-resolution optical coherence tomography (OCT) at high acquisition rates. We present a brief tutorial on the basic physics behind the operation and design of Kerr-lens modelocked lasers, where the high peak powers associated with femtosecond pulses give rise to nonlinear optical effects that play a major role in the laser operation itself and strongly influence the output spectrum. Additional nonlinear devices, in particular photonic crystal fibers (PCFs), can also be directly pumped with the generated femtosecond pulses to further extend the spectral range of the laser output, both in terms of bandwidth and center wavelength. Two specific laser systems employing different technologies for intracavity dispersion compensation (intracavity prisms in one case, and octave-spanning double-chirped mirrors in the other) will be described, and the corresponding advantages for OCT, namely the maximum achievable resolution and the applicability of spectral tuning and shaping techniques, will be briefly discussed.