FSO (Free Space Optic) is a form of optical technology communication by transmitting light to media free space. In the FSO system, the data transmission can be larger, namely 1-100 Gbps, and this is due to the large bandwidth width. FSO runs at a wavelength of 850 nm and 1550 nm. FSO is usually with a maximum distance of 2-4 km. This paper simulates the FSO optical transmission system using NRZ and RZ line coding in bright and rainy weather conditions. The parameters analyzed are Eye diagram, Optical Spectrum , photocurrent, and received signal power. In the FSO line coding system, NRZ has an eye height value, received signal power and received photocurrent is greater than the RZ line coding at a distance of 1 km and 5 km in bright and rainy conditions. In the trial of this FSO communication system, it is better to use it at a distance of 1 km, because the received signal power is above 20 dBm and received photocurrent is still above 800 mA for NRZ and RZ line coding. This is due to the attenuation value of sunny weather conditions that are smaller between 0.2-3 dB/km, while in rain conditions between 4-17 dB/km.

Theoretical approach to study the influence of temperature of the effective refractive index value for asymmetric nonlinear optical waveguides was developed. Waveguide structures are equipped with linear cladding and substrate. Numerical modeling and calculations were performed to measure the sensitivity of the effective refractive index core thickness for transverse electrical (TE) mode and transversal magnetic (TM) mode. Based on the results, which affect the waveguide refractive index value, we can also adjust the waveguide by varying the temperature value. The waveguide structure is completed by linear cladding and substrate.