F. R. Mahamd Adikan

Widely tunable linear cavity multiwavelength Brillouin-Erbium fiber lasers

Wideband multiwavelength Brillouin-Erbium fiber laser (BEFL) utilizing a linear cavity is presented, highlighting the usage of higher Brillouin and lower erbium doped-fiber pump powers to achieve higher lasing spectral bandwidth. A tuning range of 60 nm has been obtained from 1525 to 1585 nm. The dependency of the Stokes signal tuning range on the lasers pumping power is also elaborated. The wide tuning range of the proposed BEFL has potential in dense wavelength division multiplexing communication systems.

Long-wavelength EDFA gain enhancement through 1550 nm band signal injection

Abstract An experiment on gain enhancement in the long band (L-band) is demonstrated. Gain at the L-band is relatively inefficient because the operating wavelengths are far from the peak emission band of erbium ions. Gain enhancement for the L-band is achieved by using a signal from the conventional band (C-band). The efficiency of gain enhancement is strongly determined by the absorption coefficient of the C-band signal. Gain enhancement as high as 5.3 dB is obtained at −15 dBm of 1535 nm injected signal. Maximum gain enhancement for other injected signal wavelengths can be optimised by varying their power. Noise figure penalty is measured to be less than 1.0 dB at its optimised power. Furthermore, there is no penalty on the noise figure for injected signals longer than 1545 nm.

Surface Plasmon Resonance Photonic Crystal Fiber Biosensor: A Practical Sensing Approach

We propose a simple, two rings, hexagonal lattice photonic crystal fiber biosensor using surface plasmon resonance phenomenon. An active plasmonic gold layer and the analyte (sample) are placed outside the fiber structure instead of inside the air-holes, which will result in a simpler and straight forward fabrication process. The proposed sensor exhibits birefringent behavior that enhances its sensitivity. Numerical investigation of the guiding properties and sensing performance are conducted by finite element method. Using wavelength and amplitude interrogation methods, the proposed sensor could provide maximum sensitivity of 4000 nm/RIU and 320 RIU-1, respectively. The resolutions of the sensor are 2.5 × 10-5 and 3.125 × 10-5 RIU for wavelength and amplitude interrogation modes. The proposed sensor design shows promising results that could be used in biological and biochemical analytes detection.

Spectral variations of the output spectrum in a random distributed feedback Raman fiber laser

We report an ultra-long Raman laser that implemented a variable pumping scheme in backward and forward configurations. Rayleigh backscattering effects were realized in the 51 km fiber length that functioned as a virtual mirror at one fiber end. With the employment of a fiber Bragg grating that has a peak reflection wavelength at 1553.3 nm, spectral broadening effects were observed. These occurred as the pump power level was diverted more to the forward direction. Owing to this fact, a maximum width of 0.9 nm was measured at 100% forward pumping. The obtained results show that the efficient exploitation of four-wave mixing interactions as well as strong Rayleigh backscattering are beneficial to influence the lasing performances. Both of these nonlinear responses can be adjusted by varying pumping distributions along the fiber longitudinal dimension.

Highly sensitive multi-core flat fiber surface plasmon resonance refractive index sensor

A simple multi-core flat fiber (MCFF) based surface plasmon resonance (SPR) sensor operating in telecommunication wavelengths is proposed for refractive index sensing. Chemically stable gold (Au) and titanium dioxide (TiO(2)) layers are used outside the fiber structure to realize a simple detection mechanism. The modeled sensor shows average wavelength interrogation sensitivity of 9,600 nm/RIU (Refractive Index Unit) and maximum sensitivity of 23,000 nm/RIU in the sensing range of 1.46-1.485 and 1.47-1.475, respectively. Moreover, the refractive index resolution of 4.35 × 10(-6) is demonstrated. Additionally, proposed sensor had shown the maximum amplitude interrogation sensitivity of 820 RIU(-1), with the sensor resolution of 1.22 × 10(-5) RIU. To the best of our knowledge, the proposed sensor achieved the highest wavelength interrogation sensitivity among the reported fiber based SPR sensors. Finally we anticipate that, this novel and highly sensitive MCFF SPR sensor will find the potential applications in real time remote sensing and monitoring, ultimately enabling inexpensive and accurate chemical and biochemical analytes detection.

Implementation of the problem-based learning approach in the Department of Electrical Engineering, University of Malaya

This paper presents the application of the problem-based learning (PBL) method as an innovative approach to teaching engineering. This paper supports the idea that the PBL method is aptly suited to teaching the engineering disciplines, as its methodology nurtures critical thinking and problem-solving skills, which are central to a graduates career in engineering. It elaborates on the implementation of the PBL approach within the Department of Electrical Engineering, University of Malaya. Pertaining issues include the integration of the PBL method into the overall teaching methodology implemented by the department, the role of PBL facilitators and the characteristics of the PBL problems posed in the courses offered. Suggestions for future work, including the necessity for sufficient resources and collaboration with industry and academics from other disciplines, are proposed.

Copper-Graphene-Based Photonic Crystal Fiber Plasmonic Biosensor

We propose a photonic crystal fiber surface plasmon resonance biosensor where the plasmonic metal layer and the sensing layer are placed outside the fiber structure, which makes the sensor configuration practically simpler and the sensing process more straightforward. Considering the long-term stability of the plasmonic performance, copper (Cu) is used as the plasmonic material, and graphene is used to prevent Cu oxidation and enhance sensing performance. Numerical investigation of guiding properties and sensing performance is performed by using a finite-element method. The proposed sensor shows average wavelength interrogation sensitivity of 2000 nm/refractive index unit (RIU) over the analyte refractive indices ranging from 1.33 to 1.37, which leads to a sensor resolution of 5 × 10-5 RIU. Due to the simple structure and promising results, the proposed sensor could be a potential candidate for detecting biomolecules, organic chemicals, and other analytes.

Photonic Crystal Fiber in Photonic Crystal Fiber for Residual Dispersion Compensation Over

A photonic crystal fiber in photonic crystal fiber (PCF-in-PCF) architecture is numerically investigated for residual dispersion compensation in optical transmission link. The optimized structure shows a flattened and high average dispersion of -457.4 ps/nm/km in the wavelength range of 1360 nm to 1690 nm. The sensitivity of the fiber dispersion properties to a ±2% variation in the optimum parameters is studied for practical conditions. Additionally, the effect of variation in the structure parameters on effective mode area is simulated to understand its relationship to light confinement.

{\rm E} + {\rm S} + {\rm C} + {\rm L} + {\rm U}

Abstract The fabrication process of photonic crystal fibers based on a stack-and-draw method is presented in full detail in this article. In addition, improved techniques of photonic crystal fiber preform preparation and fabrication are highlighted. A new method of connecting a handle to a preform using only a fiber drawing tower is demonstrated, which eliminates the need for a high-temperature glass working lathe. Also, a new technique of modifying the photonic crystal fiber structural pattern by sealing air holes of the photonic crystal fiber cane is presented. Using the proposed methods, several types of photonic crystal fibers are fabricated, which suggests potential for rapid photonic crystal fibers fabrication in laboratories equipped with and limited to only a fiber drawing tower.

Wavelength Bands

We demonstrate liquid-crystal-based integrated optical devices with >140 GHz electrical tuning for potential applications in dynamic optical networks. Bragg wavelength tuning covering five 25 GHz wavelength-division multiplexing channel spacing has been achieved with 170 V (peak-to-peak) sinusoidal voltages applied across electropatterned indium tin oxide-covered glass electrodes placed 60 microm apart. This tunability range was limited only by the initial grating strength and supply voltage level. We also observed two distinct threshold behaviors that manifest during increase of supply voltage, resulting in a hysteresis in the tuning curve for both TE and TM input light.