*Article* **Manufacturing of Double Layer Optical Fiber Coating Using Phan-Thien-Tanner Fluid as Coating Material**

**Zeeshan Khan 1, Haroon Ur Rasheed 1, S.O. Alharbi 2, Ilyas Khan 3,\*, Tariq Abbas <sup>1</sup> and Dennis Ling Chuan Chin <sup>4</sup>**


Received: 9 November 2018; Accepted: 14 January 2019; Published: 24 February 2019

**Abstract:** Modern optical fiber required a double-layer resin coating on the glass fiber to provide protection from signal attenuation and mechanical damage. The most important plastics resin used in coating of fiber optics are plasticized polyvinyle (PVC), low/high density polyethylene (LDPE/HDPE), nylon, and polysulfone. Polymer flow during optical fiber coating in a pressure type coating die has been simulated under non-isothermal conditions. The flow dependent on the wire or fiber velocity, geometry of the die, and the viscosity of the polymer. The wet-on-wet coating process is an efficient process for two-layer coating on the fiber optics. In the present study, the constitutive equation of polymer flow satisfies viscoelastic Phan-Thien-Tanner (PTT) fluid, is used to characterize rheology of the polymer melt. Based on the assumption of the fully developed incompressible and laminar flow, the viscoelastic fluid model of two-immiscible resins-layers modeled for simplified-geometry of capillary-annulus where the glass fiber drawing inside the die at high speed. The equation describing the flow of the polymer melt inside the die was solved, analytically and numerically, by the Runge-Kutta method. The effect of physical characteristics in the problem has been discussed in detail through graphs by assigning numerical values for several parameters of interest. It is observed that velocity increases with increasing values of ε*D*<sup>2</sup> <sup>1</sup>, <sup>ε</sup>*D*<sup>2</sup> <sup>2</sup>, *X*1, and *X*2. The volume flow rate increases with an increasing Deborah number. The thickness of coated fiber optic increases with increasing ε*D*<sup>2</sup> <sup>1</sup>, <sup>ε</sup>*D*<sup>2</sup> <sup>2</sup>, and δ. Increase in Brinkman number and Deborah number enhances the rate of heat transfer. It is our first attempt to model PTT fluid as a coating material for double-layer optical fiber coating using the wet-on-wet coating process. At the end, the present study is also compared with the published work as a particular case, and good agreement is found.

**Keywords:** optical fiber coating; double-layer coating; viscoelastic PTT fluid; analytic and numerical simulations
