The objective of the thesis are to calculate power loss due to bending, to determinernthe spectral window at which ber can e ectively operates, to predict bend loss for arnhigher wavelength from the trend of shorter wavelengths and investigates the variationrnconstants of optical ber (MAC) factor,with respect to using Laser stage lighting, He-Nernlaser and Diode laser, with wavelengths in the visible and infra red region of an opticalrnspectrum.rnIn this thesis, a single mode ber (SMF) was bent to various bend radius with a spe-rncially designed, adjustable ber bending device and out put power was measured usingrna lock in ampli er. Thus, studying the relationship between macro bending and atten-rnuation would enable us to maximize the performance of an optical ber. As a whole inrnmy experimental investigation was made of the bending losses in step index single modern ber wave guide with di erent parameters of the equivalent step pro le for bending radiirnfrom 0.5cm to 10.05cm with steps of 0.5cm, with the attenuation coe cient range is 0.045rndB/m to 0.475 dB/m,0.065 dB/m to 0.48 dB/m and 0.10 dB/m to 0.61 dB/m for thernwavelengths 532nm, 633nm and 808nm respectivelyrnAs signal wavelength passes the cut o wavelength, attenuation decreases sharply duernto disappearance of higher order mode. At wavelengths longer than cut o wavelength,rnattenuation increases with wavelength increases. Furthermore, attenuation is inverselyrnproportional to bending radius measured at transmission wavelengths increases.rnThis study shows that attenuation introduced by macro bending depends on wave-rnlength and bending radius. Based on these ndings, one can minimize the adverse impactrnof macro bending. As a whole the results from the experiment have suggested that thernoptical power loss due to bending at the visible spectrum is more apparent than loss duernto other e ects such as absorption and scatteringrnviiirnAcronymsrna.u.................................. Arbitrary UnitrnFTTH ................................Fiber-to-the-HomernIR .. ..................................Infra redrnITU-T ................................International Telecommunication Union-TestingrnLASER ...............................Light Ampli cation Stimulated by Emission of RadiationrnMDUs ................................Multiple-Dwelling UnitsrnMFD ...............................Mode Field DiameterrnNA ...............................Numerical Aperturernppm ...............................parts per millionrnSMF ...............................Single Mode FiberrnSFUs ................................Single-Family UnitsrnUV ................................Ultra VioletrnKey words: macro bending ; optic beam launch; optical spectrum; radius of curvature:rnSingle mode ber: spectral window; power loss