Md. Shamim Ahsan

Migration to the Next Generation Optical Access Networks Using Hybrid WDM/TDM-PON

Due to the rapid growth of Internet and multimedia services, broadband fiber access technologies, such as Passive Optical Networks (PONs), come to the forefront of the research field. Network service providers mostly deploy Time Division Multiplexed (TDM)-PON everywhere in the world. In order to mitigate the future demand, researchers have investigated some next-generation PON systems, such as Wavelength Division Multiplexed (WDM)-PON and hybrid WDM/TDM-PONs. In this report, we propose the architecture of a self-restored hybrid WDM/TDM-PON. Due to the restorable capacity of the architecture, the availability of the PON system increases. Furthermore, the proposed architecture is a cost effective solution compared to the existing restorable PON architectures . Finally, we analyzed the power budget and signal quality of the proposed architecture , which proves the applicability of the proposed architecture to the access networks.

Formation mechanism of self-organized nanogratings on a titanium surface using femtosecond laser pulses

Abstract. We demonstrate the formation of self-organized nanogratings on a titanium surface under the irradiation of a single-beam femtosecond laser. Self-formed, periodic nanogratings are printed on a titanium surface by varying the average pulse energy, pulse width, and number of laser pulses in each spot. The direction of the nanogratings is perpendicular to the direction of the laser polarization. The nanograting period shows obvious dependence on the average pulse energy, pulse width, and number of laser pulses. The period of the self-organized nanogratings shows an increasing trend with the increase of laser energy and pulse width, and a decreasing trend with an increase of number of applied laser pulses. We qualitatively explain the formation mechanism of the self-organized nanogratings and their dependence on various laser parameters.

Fabrication of Fresnel zone plate lens in fused silica glass using femtosecond laser lithography technology

Abstract. This paper expresses maskless formation of Fresnel zone plate (FZP) lens on fused silica glass surface using femtosecond laser lithography technology. The FZP lens consists of a series of concentric rings that has been encoded on a glass surface using femtosecond laser irradiation followed by chemical etching and stripping. To compare the performance of the FZP lens with traditional laser induced FZP, we also fabricated FZP on the surface of and inside fused silica glass using femtosecond laser direct writing. In all the cases, the FZP lenses have a focal length of 50 mm. In addition, we fabricated a 25-mm focal length FZP lens by means of femtosecond laser lithography. Compared to traditional femtosecond laser direct writing, femtosecond laser lithography technique offers smooth patterning of materials. Consequently, femtosecond laser lithography engraved FZP lens yields considerably higher diffraction efficiency. Besides, we investigated the diffraction pattern of the fabricated FZP lenses. Using these FZP lenses, we are able to observe microletters encoded on an aluminum coated poly-methylmethacrylate surface indicating excellent focusing and imaging capability of the FZP lenses. The proposed maskless technology is simple compared to other lithography techniques, representing great potential for small-scale manufacturing of similar kinds of optical/photonics devices.

Formation of cylindrical micro-lens array in fused silica glass using laser irradiations

In this article, we report the development of plano-convex cylindrical micro-lens array on the surface of fused silica glass using laser processing technology. Initially, femtosecond laser pulses are irradiated on the target fused silica glass substrate to pattern periodic micro-grooves. Afterwards, laser beam from CO2 laser source is applied several times on the previously micro-patterned fused silica glass surface, the purpose of which is to polish the micro-patterned glass surface. As a consequence, periodic plano-convex cylindrical micro-lens array is evolved on the glass surface. The micro-lens array shows great consistency in size and shape throughout the sample area. We also investigate various optical properties of the micro-lenses evolved glass substrates including the diffraction pattern and diffraction efficiency of light. The glass sample comprising cylindrical micro-lens array can diffract light with moderate diffraction efficiency. We strongly believe that, it is possible to engineer cylindrical micro-lens array on the surface of a variety of transparent materials including glasses and polymers over a large area.

A study on PMIP deployment over EPON

In this paper, we discuss the issues that are needed to consider in proxy mobile IP (PMIP) deployment over Ethernet passive optical network (EPON) architecture. We present two architectures in this paper and discuss their strengths and weaknesses. Our discussion and analysis can help the network operators to deploy PMIP in EPON environment.

CO 2 Laser Assisted Fabrication of Micro-lensed Single-mode Optical Fiber

This paper reports the fabrication of various micro-lensed single-mode optical fibers through the use of an enhanced peak power

Migration to the next generation passive optical network

CO_2

An implementation of on-line traffic information system via short message service (SMS) for Bangladesh

laser beam. The end faces of the optical fibers are exposed to the

Femtosecond laser based in-fiber long period grating fabrication for improved solution sensing

CO_2

Characterization of femtosecond laser filament-fringes in titanium

laser beam to form convex, concave, and conical shape optical fiber tips. Peak power of the