Nearly zero-dispersion, low confinement loss, and small effective mode area index-guiding photonic crystal fiber at 1550nm wavelength Saeed OLYAEE (), Fahimeh TAGHIPOUR, Mahdieh IZADPANAH Nano-photonics and Optoelectronics Research Laboratory (NORLab), Faculty of Electrical and Computer Engineering, Shahid RajaeeTeacher Training University (SRTTU), Lavizan, 16788-15811, Tehran, Iran. Tel/Fax: +98 (21) 22970006, Email: s_olyaee@srttu.edu Abstract In this paper, a new simple structure of index-guiding photonic crystal fiber (PCF) is designed and presented. In this PCF, dispersion, confinement loss, and effective mode area characteristics are investigated in the second communication window (1.55μm). Since 1.55μm wavelength is widely used in optical communication systems, we try to optimize the PCF characteristics in this wavelength by designing an index-guiding PCF and three versions of optimized PCF. The results show that the dispersion is obtained very close to zero around 4.6×10 -4 ps/ (nm.km). Also, the confinement loss is 2.303×10 -6 dB/km and effective mode area is as small as 2.6 μm 2 . Keywords dispersion, effective area, confinement loss, index-guiding, photonic crystal fiber 1 Introduction Nowadays, single mode fibers are widely used as transmission media in wavelength division multiplexing systems. In these fibers, dispersion and confinement loss depend on the wavelength. Because optical fibers show minimum loss at 1.55μm, this wavelength is very applicable to transfer information. In standard optical fibers, loss is around 0.1dB/km and dispersion equals 16 ps/nm·km in 1.55 μm wavelength. Recently, a new type of microstructure fibers having zero dispersion value in a wide range of wavelengths is presented. These fibers are called photonic crystal fibers (PCFs) and have unique characteristics. PCFs can be composed of silicon glass with arrays of air-holes channels running along its length [1]. Created defect in the center of this array plays the role of the core. In this paper, an index-guiding fiber is presented that its core refractive index is more than cladding refractive index. So, the light propagates based on the total internal reflection (TIR) effect in the fiber. In conventional PCFs, 20 rings of same air-holes are used to achieve acceptable loss. This leads to increase in the fiber diameter. Newly, scientists are focused on PCFs with multi-structures to control the characteristics better. PCF with three-fold symmetric hybrid core can achieve zero dispersion as well as low confinement loss. In this PCF, dispersion and confinement loss are respectively around -2ps/ (nm.km) and less than 7.9 dB/km [2]. The later designs [2-12] have shown better results by using various techniques such as: PCFs with elliptical air holes [3], PCF structure with gradually increasing the diameter of the hole from inner ring to the outer [4], filling air holes with different liquids selectively [5], and PCFs with double cladding [6], although the fabrication processes are difficult in these plans. RESEARCH ARTICLE Front. Optoelectron. China (2011) 4: DOI 10.1007/s12200-000-0000-0