Improvement of the coding performance of SSFBG en/decoder by apodization technique

Abstract

width are seen (varied from 126°to 63°, a variation of 63°). This behavior indicates that, by varying the diameter D, the 3-dB beamwidth of the monopole's radiation pattern can be effectively controlled. Figure 6 presents the measured antenna gain against frequency for the cases with h ϭ 0 (reference antenna) and 25 mm. The reference antenna shows an antenna gain level of about 1.5 dBi higher than that of the case with h ϭ 25 mm. This is because the reference antenna has a smaller 3-dB beamwidth, thus having a higher directiveity and a higher antenna gain. Measured antenna gain at 2442 MHz for other cases studied is also listed in Tables 1 and 2 for comparison. In general, a larger 3-dB beamwidth obtained will lead to a smaller antenna gain for the monopole antenna. CONCLUSIONSThe omnidirectional radiation pattern of a cylindrical monopole antenna with a truncated-conical ground plane has been experimentally studied for operation in the 2.4-GHz WLAN band. The results have indicated that, by varying the height h and opening diameter D of the truncated-conical ground plane, the maximum radiation direction and 3-dB beamwidth of the monopole's omnidirectional radiation pattern can be effectively controlled. With this pattern-control technique, the cylindrical monopole antenna is very suitable for WLAN access-point applications and can provide an optimal or near-optimal omnidirectional radiation pattern in order to cover the desired service area for enhanced WLAN communications. IMPROVEMENT OF THE CODING PERFORMANCE OF SSFBG EN/DECODER BY APODIZATION TECHNIQUE

Investigation of superstructured fiber Bragg grating-based OCDMA system

“…In the SSFBG-based phase-coding OCDMA scheme, the variations of input pulse width [7] and grating refractive index modulation amplitude [8] will result in different correlation characteristics of the SSFBG en/decoder. However, previous analysis about correlation performance of en/decoder could only qualitative evaluate the effects of increased input pulse width and grating refractive modulation amplitude on the system performance.…”

Code cardinality maximization using highly reflective SSFBG with optimum apodization profiles

“…In a SSFBG based OCDMA, the code performance is maximized for low values of modulation index, as only this level of reflectivity assures that the pulse response is given by a Fourier-transform of the spatial refractiveindex modulation profile [2]. However the gratings reflectivity should also be kept high enough in order to minimize overall system loss.…”

“…However the gratings reflectivity should also be kept high enough in order to minimize overall system loss. Hence, the refractive index must be balanced by a trade-off between the code performance (Fourier transform relation) and the reflectivity of SSFBG [2].…”

Sistema de fabricación de altas prestaciones de redes de difracción de bragg en fibra y aplicaciones al campo de los sensores ópticos y a los sistemas de comunicaciones ópticas.

“…Debido a esta baja reflectividad, las pérdidas de inserción de este tipo de dispositivos son elevadas (>10 dB). En la literatura se ha propuesto una función de apodización de la variación del índice de refracción que compensa las pérdidas y permite incrementar la reflectividad local [WAN04]. Esto provoca una disminución de las pérdidas de inserción, pero no evita la distorsión de la respuesta impulsiva producida por las múltiples reflexiones.…”