Developments in the technology sector are currently experiencing rapid progress, especially in data transmission technology. The increasing need for fast data traffic in the telecommunications sector requires technology that can send data quickly. Optical fiber has the speed of receiving and sending data at 2.5 Gbps while FSO has a speed of up to 100 Gbps but this depends on Wavelength, the modulation technique used and the distance of the telescope between the transmitter and receiver. The speed of receiving and sending data also depends on the Quality (Q) of the signal, the greater the value of Quality (Q) of the signal, the better the Quality of the signal. FSO is an optical communication system that uses the atmosphere as its propagation medium and Optical Fiber uses silica as its propagation medium. Therefore, in this paper, a performance analysis of Free Space Optics (FSO) and Single Mode Fiber is carried out based on the Quality Factor and Bit Error Rate (BER) of a signal that is carried out using Optical System simulations with a wavelength of 1310 nm, 1380 nm, 1550 nm, 1550 nm and 1560 nm, with 1 km, 3 km and 5 km, respectively. Then, analysis uses an Eye Diagram to analyze the output signal and compare the Factor Q and Bit Rate Error (BER).

Directional Coupler is one of the devices used in signal transmission techniques in optical fiber communication systems, especially Wavelength Division Multiplexing (WDM). The directional coupler can be used as a sensitive sensor, one of which is based on wavelength shifts and coupling length shift. This paper simulates a shift in wavelength and coupling length based on the influence of temperature in the range of 30℃ to 230℃ based on the characteristics of power output. The wavelength used in this simulation is in the C-Band region, which is around 1550 nm. Temperature changes cause changes in the material refractive index. Temperature changes cause a shift in wavelength and coupling length increase which describes the characteristics of the thermo-optic effects on the directional couplers.

To increase bandwidth and number of channels per fiber for more than one wavelength in the same fiber the dense wavelength division multiplexing (DWDM) technology has been utilized. One of the devices that are important in DWDM is an optical interleaver. This paper discussed the effects of temperatures in the DWDM interleaver by using the Mach-Zehnder interferometer (MZI) structures which is arranged in two-stage cascaded MZI and the three-stage cascaded MZI geometries. The main consequences of increase temperature inside the fiber optics are the change of effective refractive index in the material of silica fiber due to the thermo-optics effects. In our analysis we have used the transfer matrix method to investigate the wavelength dependence of output power to the temperatures changes that varies from 30oC to 430ºC. In the calculation we have used the C-Band range wavelength which is around 1530 to 1565 nm. It has been shown that the change of temperatures may shift the wavelength inside the MZI output power in linear manners. These effects may be used to tune wavelength transmission inside the MZI structures to suit the ITU-T defined grid.

In mechanical system where spring and damper are used often create unwanted vibration, due to external forces. Unwanted vibration may cause further noise and other damages such as engine break, etc. To reach system stability, we model of coupling series of freight car and analyze them using root loci and plot waves. From the result we can analyze what is the maximum stability by altering spring and damper constant. It is found when the spring and damper constant increase, the stability will be fast.

An application GUI (Graphical User Interface) is designed as a software simulation to compare the output signal of DFT and DTFT. DFT (Discrete Fourier Transform) and DTFT (Discrete Time Fourier Transform) are part of the digital signal processing. Digital signal processing is an analog signal processing method uses a mathematical technique to perform a transformation or retrieving information in digital form. One of the benefits of digital signal processing is to facilitate the representation of the signal, because the signal in digital form will be more visible, easily processed and has high accuracy. This GUI application designed using LabVIEW from National Instruments.  LabVIEW is a software graphical programming or a block diagram. LabVIEW program known as VI or Virtual Instrument. The input signal in this application is a square signal