N. Md. Yusoff

Gain-flattened erbium-doped fiber amplifier with flexible selective band for optical networks

Erbium-doped fiber amplifier with flat gain over 30 nm bandwidth is demonstrated using flexible selective band methods. The band optical amplifier was designed to cater 44 wavelength division multiplexing channels which were separated into bands of 4 nm. Without using any gain flattening filter, the gain of optical amplifier was maintained at 19 dB with a maximum gain variation of less than 1.6 dB even though the input signal power was varied from −19 to −6 dBm. The amplifier was able to maintain 1 dB gain flatness with 83% chance for any selective bands of 4 nm within the wavelength range from 1530 to 1565 nm. This feature is very attractive to support band optical networks.

Bidirectional-pumped L-band erbium-doped fiber amplifier with pump distribution technique

A dual-stage erbium doped fiber amplifier (EDFA) having a flat gain wavelength response throughout L-band transmission window is presented. By applying pump power distribution technique, the pump power is distributed to two different stages with different length of EDF depending on the coupling ratio. By controlling these two parameters, gain of 19.1 dB with small gain variation of less than 0.5 dB and a noise figure of less than 10.5 dB are achieved in this architecture using bidirectional pumping. However, when another 3 dB power coupler is added to split the pump power equally at the second stage in bidirectional, a better noise figure of less than 7.5 dB was obtained. Comparison with a conventional single-stage optical amplifier was made in order to validate the performances of this dual-stage EDFA.

Ultrashort pulse laser generation in ring-type EDFL using carbon-nanotube saturable absorber

This study investigates the capability of an ultrashort pulse laser in a ring cavity of erbium-doped fiber laser (EDFL). Generation of pulses was performed by inserting a carbon-nanotube saturable absorber in this EDFL. Mode-locked laser was achieved with an average power of 20mW and a peak power of 3.37kW. Pulse duration laser of 950fs with repetition rate of 6.24MHz was obtained at 3dB bandwidth of 3.65nm. Higher power with better pulse duration can be achieved by optimizing the cavity length.

Multiwavelength Fiber Laser based on Bidirectional Lyot Filter in Conjunction with Intensity Dependent Loss Mechanism

With the rapid growth of communications via the Internet, the need for an effective firewall system which has not badly affect the overall network performances has been increased. In this paper, a Field Programmable Gate Array (FPGA) -based firewall system with high performance has been implemented using Network FPGA (NetFPGA) with Xilinx Kintex-7 XC7K325T FPGA. Based on NetFPGA reference router project, a NetFPGA-based firewall system was implemented. The hardware module performs rule matching operation using content addressable memory (CAM) for higher speed data processing. To evaluate system performance, throughput, latency, and memory utilization were measured for different cases using different tools, also the number of rules that an incoming packet is subjected to was varied to get more readings using both software and hardware features. The results showed that the designed firewall system provides better performance than traditional firewalls. System throughput was doubled times of the one with Linux-Iptables firewalls.

Q-switched Thulium-doped fiber laser using nitrogen-doped graphene in linear and ring cavity

Q-switched Thulium-doped fiber laser has been demonstrated with two configurations; linear cavity and ring cavity. Nitrogen-doped graphene in polyvynil alcohol has been applied in both laser cavities during loss modulation process.

Multiwavelength SOA fiber ring laser based on bidirectional Lyot filter

We have demonstrated multiwavelength fiber laser (MWFL) based on bidirectional Lyot filter and semiconductor optical amplifier (SOA). The intensity dependent loss (IDL) mechanism is utilized to obtain a flat multiwavelength spectrum of 94 wavelength lines within 5 dB bandwidth. The extinction ratio (ER) is 9 dB, while the line spacing is narrow at 0.1 nm. No polarizer is used in the experimental structure, thus the IDL mechanism is only came from SOA. When SOA current is decreased, worse wavelength lines and multiwavelength flatness is achieved. Without proper adjustment of polarization controllers (PCs), the multiwavelength performance is found degraded.

Investigation of nitrogen doped graphene as saturable absorber in Thulium-Doped Fiber Laser

The work investigated the Q-switched Thulium-Doped Fiber Laser (TDFL) that operates in 1900 nm region by using nitrogen graphene (NG) embedded in polyethylene oxide (PEO) as saturable absorber (SA). The highest output power achieved was 0.52 mW with highest repetition rate of 33.43 kHz. The shortest pulse width was 3.205 μs with pulse energy of 31.11 nJ.

Investigation on the signal performances of pre-, post- and inline compensation of l-band dispersion compensator using Chirped Fiber Bragg grating

The placement of Chirped Fiber Bragg grating in between the span plays an important role as it affects the signal quality when it reaches the transmission end. The work highlights on the signal performance at 10 Gbps data rate after propagating through a 90 km transmission fiber. The worst BER is obtained in the inline compensation configuration as compared to pre- and post- compensation. The highest received power of -0.19 dBm with bit error rate of 2.65 E-07 is obtained in post-compensation configuration while the highest received power for post-compensation configuration is around -0.7 dBm with bit error rate of 4.95 E-07. However, pre-compensation configuration is chosen in further measurement as it gives the best power penalty as compared to other configurations when BER of 1 E-06 is used as the benchmark for the signal quality.

Pump power distribution in bidirectional pumped dual-stage L-band EDFA

Bidirectional pumped dual-stage L-band EDFA utilizing a single power splitter and pump laser has been presented in this paper. A power splitter has been used to distribute the pump power bidirectionally to pump two EDFs with different length. An average gain of 18.6 dB with average NF of 8.6 dB has been attained when the signal is equal to 0 dBm ranging from 1570 nm to 1605 nm signal. By using a single pump simultaneously with low gain ripple of less than 0.7 dB throughout the L-band transmission window.

Investigation of continuously adjustable extinction ratio in a multiwavelength SOA fiber laser based on intensity dependent transmission effect

We investigate a flat multiwavelength fiber laser (MWFL) with the extinction ratio (ER) is continuously adjustable at variation of either half wave plate (HWP) position or polarization maintaining fiber (PMF) length. The multiwavelength laser is generated from an intensity dependent transmission (IDT) effect which is induced from nonlinear polarization rotation (NPR), arising from a combination of a semiconductor optical amplifier (SOA), polarization controllers (PCs) and polarization beam splitter (PBS). The ER is continuously adjustable from 6 dB to 12 dB by rotating the HWP of a PC, as the same value of the minimum and the maximum ER can be obtained in every 45° of HWP position. The ER value is also adjustable at different length of PMF, as longer PMF is contributed to a flatter multiwavelength spectrum. The proposed MWFL design is simple, high number of lines, flat and able to adjust ER continuously.