Contents lists available at ScienceDirect Optical Fiber Technology journal homepage: www.elsevier.com/locate/yofte Optimization of spin parameters for spun fbers having low polarization mode dispersion Şerif Ali Sadık a,b, ⁎ , Sait Eser Karlık c , Hasan Temurtaş d , Ahmet Altuncu a,b a Department of Electrical and Electronics Engineering, Kütahya Dumlupınar University, Kütahya, Turkey b Photonics Technologies Application and Research Center, Kütahya Dumlupınar University, Kütahya, Turkey c Department of Electrical and Electronics Engineering, Bursa Uludağ University, Bursa, Turkey d Department of Computer Engineering, Kütahya Dumlupınar University, Kütahya, Turkey ARTICLEINFO Keywords: Polarization mode dispersion (PMD) Spun fber Optimization Diferential Evolution Algorithm (DEA) ABSTRACT Polarization mode dispersion (PMD) is a dispersive efect caused by the birefringence of the optical fber. Spinning the fber with periodic profles during the drawing process from preform is known as a PMD-reducing process. In this paper, common spin parameters giving successful results in obtaining low PMD for three spin profles, i.e. sinusoidal, amplitude modulation-suppressed carrier (AM-SC) and amplitude modulation-trans- mitted carrier (AM-TC), are searched and an optimization problem based on this research is defned. This op- timization problem is solved by using Diferential Evolution Algorithm (DEA) and common spin parameters suitable for all discussed spin profles are obtained. For all spin profles, optimum common spin parameters are found to be 8.81 turns/m for the spin amplitude and 3.69 m for the spin period. Numerical analysis performed with those optimum spin parameters show that in the short fber regime the diferential group delay (DGD) takes a value under 0.25 fs and the mean DGD value remains lower than 15 fs in long lengths of fber. The obtained results show that PMD reduction with respect to unspun fbers can be achieved by using optimized spin profles even in the case of random mode coupling. 1. Introduction With the requirement of high capacity optical fber networks, the performance-limiting polarization mode dispersion (PMD) efect has become an important issue. In single mode optical fbers light propa- gates along the fber core as two orthogonally polarized modes. Due to the presence and random variation of birefringence along the fber, these two modes propagate with diferent group velocities. The delay between these modes is called as the diferential group delay (DGD). The DGD leads to pulse perturbation called PMD [1–3]. Spinning the optical fber during the drawing process while the fber is in the viscous state has been proposed as a practical solution for reducing PMD. The idea of spun fber was proposed by Barlow et al. in [4] and improved by Hart et al. [5]. While the optical fber is being drawn from the preform in spun fbers, the applied torque forces slow and fast axes of the fber to rotate. With rotation of axes, the DGD evolves in a periodic way preventing accumulation. The spin may be applied in one direction with constant spin rate or in both directions with periodic spin rate [6–9]. This paper discusses the theory behind PMD in spun fbers and presents optimum input parameters for producing low-PMD spun fbers. We believe this to be a well analyzed presentation of the proposed spin function in [10] and other periodic spin functions, and also provide valuable guidance on the choice of the optimum parameters for all periodic spin functions associated with manufacturing low-PMD fber. The proposed optimum parameters presented in this work can achieve low PMD requirements for high-bit-rate communication systems. The second section reviews the coupled mode theory of orthogonal polar- ization modes for understanding PMD in spun fbers. In the third sec- tion, general steps of an optimization problem and the Diferential Evolution Algorithm (DEA) are introduced. The fourth section four provides numerical results of the simulations. Finally, the results are discussed in the conclusion section. 2. PMD of spun fibers The light propagating in an ideal single mode optical fber has two degenerate modes with orthogonal polarization. The electric feld of propagating light is a linear superposition of these two orthogonally polarized modes. In real fbers, these modes propagate at diferent https://doi.org/10.1016/j.yofte.2019.04.011 Received 15 January 2019; Received in revised form 9 April 2019; Accepted 26 April 2019 ⁎ Corresponding author at: Department of Electrical and Electronics Engineering, Kütahya Dumlupınar University, Kütahya, Turkey. E-mail address: serifali.sadik@dpu.edu.tr (Ş.A. Sadık). Optical Fiber Technology 51 (2019) 31–35 1068-5200/ © 2019 Elsevier Inc. All rights reserved. T