en 2-Optoelectronics and Photonics Optoelectronics and Photonics Research Paper Research Paper In this paper, a novel design of all-solid photonic bandgap fiber with ultra-low confinement loss is proposed. The confinement loss is reduced remarkably by managing the number of rods rings, up-doping level, pitch value, and rods diameters. Moreover, the designed PCF shows ultra-flattened dispersion in L- and U-band. Furthermore, a new design, based on introducing of an extra ring of air holes on the outside of the all-solid bandgap structure, is then proposed and characterized. We demonstrate that it significantly reduces the fiber diameter to achieve negligible confinement loss. The validation of the proposed design is carried out by employing a two dimensional finite difference frequency domain with perfectly matched layers. Confinement Loss,Dispersion,Finite Difference Frequency Domain,Photonic Bandgap Fiber,Up-Doping, 122 128 http://ijeee.iust.ac.ir/browse.php?a_code=A-10-402-1&slc_lang=en&sid=1 M. Aliramezani m_ramezani83@yahoo.com 180031947532846002191 180031947532846002191 Yes Department of Electrical Engineering, Iran University of Science and Technology Sh. Mohammad Nejad Shahramm@iust.ac.ir 180031947532846002192 180031947532846002192 No Department of Electrical Engineering, Iran University of Science and Technology