Source coherence impairments in a direct detection direct sequence optical code-division multiple-access system.

We demonstrate that direct sequence optical code- division multiple-access (DS-OCDMA) encoders and decoders using sampled fiber Bragg gratings (S-FBGs) behave as multipath interferometers. In that case, chip pulses of the prime sequence codes generated by spreading in time-coherent data pulses can result from multiple reflections in the interferometers that can superimpose within a chip time duration. We show that the autocorrelation function has to be considered as the sum of complex amplitudes of the combined chip as the laser source coherence time is much greater than the integration time of the photodetector.

Efficient Bragg gratings in phosphosilicate and germanosilicate photonic crystal fiber.

We present ArF laser-induced dynamics of Bragg grating (BG) growths in phosphosilicate-doped or germanosilicate-doped core photonic crystal fibers (PCFs). To this end, we have adapted the technique of H2 loading, usually used in conventional fiber, to the case of microstructured fiber, allowing both the concentration of hydrogen in the PCFs to be kept nearly constant for the time of the exposure and the BG spectra to be easily recorded. We compared the characteristics of BG growths in the two types of PCF to those in conventional step-index fibers.

Isochronal annealing of Bragg gratings written in H2-loaded or in UV-hypersensitized germano-phosphosilicate planar waveguides: a comparison.

Bragg Gratings (BGs) have been written within either H2-loaded or UV-hypersensitized phosphorous-germanium co-doped silica planar waveguides through exposure to light at 248 nm. The stability of these BGs has been investigated by means of isochronal annealing experiments. It appears that the stability of both the modulation and the Bragg wavelength is higher in the hydrogenated waveguides than in the hypersensitized counterparts.