I. Introduction
The renowned name in the family of integrated optics is micro ring resonator (MRR). Its vast execution in the field of Optical-switch [1], modulation [2], sensing [3], signal processing [4], wavelength division multiplexing (WDM) [5], optical filtering etc. increase the research area over optical discipline. In the integrated photonic platform, it is a suitable component because of its high efficiency, low loss and small size. Particularly, the micro and nano-fabrication process of silicon photonic technology has opened a new era to the research world and it has revolutionized the optoelectronics and photonics industry by its countless advantages especially for complementary metal-oxide semiconductor (CMOS) [6]. In Fiber optic communication channel, the application of OPADF always depends on the large Bandwidth (BW). So our main aim is to increase the BW by increasing the FSR. The Fabry-Peot ring resonator structure where single ring was coupled with 2 bus waveguides (B-Ws) and double ring structure ware developed by Suzuki et al. [7]. The structure was capable to provide the FSR of l4.3GHz and 98 GHz respectively. In the next stage of research, Mandal.et al. [8] introduced three rings coupled with two B-Ws that provides the FSR of 200GHz. The FSR was further increased by S. Addya and S.B. Dey by modelling four MRRs coupled with two B-Ws [9]. The same approach was followed by F. Rukerandanga et al. [10] by modelling six MRRs based OADF. MRR based OADF by using silicon on insulator (SOI) material was projected by L. Tozzetti et al. [11]. The band-pass filter was designed by N.Kohli et al. [12] by serially joined MRRs. The add-drop optical filter is explained by H. J. Borkakati et al. [13] by using photonic crystal ring resonator.