Now-a-day's optical fiber forms the basis for local, national and telecommunication network. It is broadly used in communication system instead of electrical copper cables because of its small size, very high bandwidth and low transmission loss. But it has always some chances to loss the transmitting signal. Bending is one of the permanent reasons to loss of the transmitting signal. It can increase the fiber attenuation by two mechanisms: macrobending and microbending. Macrobend occurs when a fiber is bent through a large angle and microbend can be generated at any stage during the manufacturing process or service. For these cases, entire signals do not reach the receiver. We perform a simulation study for bending losses in a single mode optical fiber. Single mode fibers are commonly used in communication system than multimode fibers because of its least attenuation and low dispersion. The study has been done using the software "Understanding Fiber Optics on a PC". We find a minimum loss of 0.0 dB for the wavelength of 1.3µm, core radius of 4.0 µm, refractive index difference of 0.35% and bend radius of 7 cm. This result may be an important milestone to design an optical fiber.