Simulation of an optical coupler using beam propagation method

Abstract

Optical coupler is an important thing in a fiber optics system. In this paper, the simulation of an optical coupler is performed by Beam Propagation Method for Fiber (BPM 3DF). I f two waveguides are sufficiently close such that their fields overlap, light can be coupled from one into the other. By using BPM 3DF, 2 linear waveguides as the fiber are designed, embedded in a wafer (cladding). 3 parameters are changed one by one; the length, the width and the height of the wafer and the fiber to define the exact parameters that can make the device acts as a 3 dB coupler. By using 2250 µm length, 35 µm width and 22 µm height, the program shows that half of optical power is transferred to fiber 2 so that the coupling ratio is 50:50. Besides, if the length is increased more than 2250 µm, more than half of power is transferred to fiber 2 until it is transferred completely at a distance 4500 µm. If more than 4500 µm length, the power is interchanges continuously between fiber 1 and fiber 2. If the length isless than 2250 µm, only small quantity of power is transferred. The same result would be observed if it is increased and decreased one by one of the parameters; the width of wafer or the height of wafer while other parameters are constant. If the width is more than 35 µm or the height is more than 22 µm while other parameters constant, the power interchanges continuously between fiber 1 and fiber 2. While the width is less than 35 µm or the height is less than 22 µm, more than half of power is transferred to fiber 2. Inthis case, it is observed that there is a minimum width which is 17 µm and the minimum height which is 9 µm, whereby above that values, the program is executable. From the result, its shows that the length, the width and the height of the wafer and fiber are influenced the quantity of optical power through from one fiber to other fiber and can build a 3 dB coupler.