The most sensitive part of the installed optical fiber fable is the optical loss variation of the splicing part according to the environmental changes. This paper presents the details of the experimental results of the external environmental changes on optical loss, such as bending, temperature variation, temperature variation after water osmosis and vibration. Through the bending test of optical fiber, rapid increase of optical loss was measured within the radius of 30mm. The result of optical loss variation within the temperature range of $-30^{circ}C{sim}60^{circ}C$ is less than 0.02dB. It was confirmed that the maximum optical loss increased up to 0.2dB in case of water osmosis within the temperature range of $-40^{circ}C{sim}80^{circ}C$. There is small optical loss variation of 0.01dB under the 1mm vibration test. The experimental results of this paper can be used as the reference data for the design of the optical fiber cable splicing enclosure to protect the optical loss variation due to environmental changes.