A. Ahmad

Brillouin-Raman comb fiber laser with cooperative Rayleigh scattering in a linear cavity

We demonstrate a multiple-wavelength Brillouin comb laser with cooperative Rayleigh scattering that uses Raman amplification in dispersion-compensating fiber. The laser resonator is a linear cavity formed by reflector at each end of the dispersion-compensating fiber to improve the reflectivity of the Brillouin Stokes comb. Multiple Brillouin Stokes generation has been improved in terms of optical signal-to-noise ratio and power-level fluctuation between neighboring channels. Furthermore, the linewidth of the Brillouin Stokes is uniform within the laser output bandwidth.

Flat amplitude multiwavelength Brillouin-Raman comb fiber laser in Rayleigh-scattering-enhanced linear cavity

We investigate the amplitude flatness of Rayleigh-assisted Brillouin-Raman comb laser in a linear cavity in which feedbacks are formed by high-reflectivity mirror. The optimization of Brillouin pump power and wavelength is very crucial in order to obtain a uniform power level between Stokes lines. The Brillouin pump must have a relatively large power and its wavelength must be located closer to the Raman peak gain region. The flat-amplitude bandwidth is also determined by the choice of Raman pump wavelengths. A flat-amplitude bandwidth of 30.7 nm from 1527.32 to 1558.02 nm is measured when Raman pump wavelengths are set to 1435 and 1450 nm. 357 uniform Brillouin Stokes lines with 0.086 nm spacing are generated across the wavelength range. The average signal-to-noise ratio of 17 dB is obtained for all the Brillouin Stokes lines.

Brillouin-Erbium fiber laser with enhanced feedback coupling using common Erbium gain section

We demonstrate an enhanced architecture of Brillouin-Erbium fiber laser utilizing the reverse-S-shaped fiber section as the coupling mechanism. The enhancement is made by locating a common section of Erbium-doped fiber next to the single-mode fiber to amplify the Brillouin pumps and the oscillating Stokes lines. The requirement of having two Erbium gain sections to enhance the multiple Brillouin Stokes lines generation is neglected by the proposed fiber laser structure. The mode competitions arise from the self-lasing cavity modes of the fiber laser are efficiently suppressed by the stronger pre-amplified Brillouin pump power before entering the single mode fiber section. The maximum output power of 20 mW is obtained from the proposed fiber laser with 10 laser lines that equally separated by 0.089 nm spacing.

OSNR variation of multiple laser lines in Brillouin-Raman fiber laser

We report experimental results demonstrating the variation of optical signal-to-noise ratio (OSNR) of laser lines in Brillouin-Raman fiber laser against Raman pump power (RPP) variation. The reduction of OSNR is attributed to the spectral broadening of laser lines depending on the RPP. The spectral broadening is owing to the effect of the interaction between laser lines and turbulent waves (nonlinear interaction between longitudinal cavity modes). In our experiment, the worst OSNR is obtained at 650 mW RPP as a result of maximum spectral broadening when the Brillouin pump wavelength is fixed at 1555 nm. On the other hand, the OSNR improvement is obtained for RPP beyond 650 mW due to the effect of red-shift, the Raman peak gain is shifted away from the laser lines generated around 1555 nm thus reduces the spectral broadening effect.

Backflashover analysis for 132 kV Kuala Krai-Gua Musang transmission line

Lightning has been a major concern to the power system researchers because it can cause damage to the connected electrical equipment and transmission failure. One study carried out is that where the level of voltage at a substation is observed following a backflashover analysis on a transmission line. Sample of worst case transmission line was taken from Tenaga National Berhad, which is 132 kV Kuala Krai-Gua Musang line for the purpose of simulation using PSCAD software. An integral part of this study is the model of transmission line components such as insulator coordination gap flashover, tower model, nonlinear current dependent resistance as footing model. All models are verified by accurate analysis of previous researchers. Results were analyzed and influences of line parameters to backflashover rate were discussed. Practical recommendations and conclusions based on the results are made for an improvement in the lightning performance of high voltage transmission line.

Gain-control Raman fiber amplifier incorporating ring cavity

All-optical gain-control Raman fiber amplifier (RFA) based on ring cavity technique using a pair of circulators is investigated experimentally. A pair of 1465 nm laser diodes are used as the pump source to the RFA which provides a gain peak at around 1565 nm. The analyses of gain and noise figure are carried out using lasing wavelengths of 1550 and 1565 nm. Gain and noise figure variations are 0.4 and 0.5 dB respectively. We observed strong influence of pump-signal relative intensity noise transfer that results in noise figure penalty.

FTTx optical extender for Ethernet Passive Optical Network (EPON)

This paper present the PON optical extender designed for Ethernet Passive Optical Network (EPON) architecture. The PON extender performance test has been performed on an EPON platform for a scalable PON network deployment. A 256 optical splitting ratio at a 20km fixed fiber span and average throughput of 92.383 Mbps has been achieved.

Influence of the pumping scheme in double-pass discrete Raman-fiber amplifiers

We demonstrate the effect of the pumping scheme in a double-pass discrete Raman-fiber amplifier. The copumping scheme outperforms the counterpumping scheme for small and medium signal power ranges. The performance discrepancy of about 0.3 dB is measured. However, the counterpumping scheme performs better than that of the copumping scheme for large signal powers. These effects are influenced by the pump distribution along the fiber-amplifying medium. The pump-depletion effect is found to be the main cause of the performance discrepancy between these two pumping schemes. These findings can be utilized as the guidelines in designing double-pass discrete Raman-fiber amplifiers.

Polarization Insensitive Optical Wavelength Conversion Based-on Degenerated FWM in Raman Ring Laser

We demonstrate the idler generation based on degenerated four-wave mixing assisted by Raman amplification in highly nonlinear fiber. The pump source is internally created using a ring oscillation in the Raman cavity laser. The wavelength conversion efficiency is greater than unity within 19.5 nm wavelength range around the pump source.

Performance evaluation of multi-user detection in CDMA using micro-genetic algorithm

Two main problems of multi-user communication systems are the multiple access interference (MAI) and the near-far effects. While the near-far effect problem can be approached by applying power control, the MAI problem requires individual receivers to identify the desired signal from interferences thus making multi-user detector a popular area of research. Genetic algorithms (GA) is a search and optimization technique that works by estimating multiple solutions in order to come with the best estimated solution. GA works iteratively over a population of solutions using crossover and mutation to simulate a potential solution. In this paper we examine the performance of a micro-genetic algorithm-based multi-user detector. Our simulation shows that /spl mu/GA achieves a performance close to an optimal detector.