Method and apparatus for fusion-splicing polarization maintaining optical fibers

A method for fusion-splicing a first polarization maintaining optical fiber having a core and stress applying members which form a polarization plane and a second polarization maintaining optical fiber having a core and stress applying members which form a polarization plane, comprising:

• aligning an end face of the first polarization maintaining optical fiber and an end face of the second polarization maintaining optical fiber in accordance with images obtained from two different lateral directions of the first and second polarization maintaining optical fibers;
• adjusting the polarization planes of the first and second polarization maintaining optical fibers to be coincident with each other in accordance with a luminance distribution for each of the first and second polarization maintaining optical fibers, the luminance distribution being obtained from at least one of the images from two different lateral directions;
• and
• fusion-splicing the first and second polarization maintaining optical fibers with the thus coincided polarization planes with each other,
• wherein the polarization plane adjusting step includes detecting a first luminance peak closest to a first end of a bright portion of the luminance distribution and a second luminance peak closest to a second end of the bright portion, the second end being opposite to the first end, obtaining a sum of a first distance between positions of the first end and the first luminance peak and a second distance between positions of the second end and the second luminance peak, or a third distance between positions of the first and second luminance peaks, and moving at least one of the first and second polarization maintaining optical fibers such that the sum of the first and second distances becomes minimum or the third distance becomes maximum.