The technique of optical interferometry has many applications in various fields of knowledge, including astronomy, optical metrology, biology, and chemistry. The visible interference pattern of a conventional single mode fiber (SMF-28) tapered and core-offset structured in-line Mach-Zehnder interferometer has been demonstrated. The white source is generated by an LED, with a wavelength range of 400 nm to 650 nm emission. We analyze the performance of the interference emission with a waist length of 1.8 mm to 6 mm and with a waist diameter of 10 µm to 60 µm for the tapered structure. The achieved visibility is V=0.14 with an FSR of 23 nm. The core-offset structure interferometer is analyzed with different displacements in x and y axis and with a separation length L of 2.5 cm, 4.0 cm and 5.0 cm between two core joints. The output interference emission has a visibility of V= 0.3, V=0.27 and V=0.34 with an FSR of 23 nm, 17 nm and 8 nm, respectively. The sensitivity obtained from the temperature sensor is of 3.53 a.u./°C, with R2 of 0.99769. The proposed MZIs are low cost and can be used for implementation of sensing system in the field as the industry and medical applications.