This paper studies in depth the losses resulted from the mechanical alignment errors in fiber-optic information transmissions at 1 550 nm and 1 310 nm.MATLAB simulation results show that attenuation in higher order modes is more serious than that in lower order modes and the lateral alignment error of single-mode fibers is the most serious factor for these losses

and that when the Numerical Aperture（NA）is large

the coupling loss caused by angle deviation is reduced

while when the NA remains the same

the higher the refractive index of matching fluid

the lower the coupling efficiency

which is opposite to the effect on losses arising from the end clearance.The study results in this paper have certain theoretical and practical significance for the stable development of fiber-optic information communication.