Page 86 - Fiber Bragg Gratings

3.1 Methods for fiber Bragg grating fabrication 65

Figure 3.7: (a) Avoiding the zero order from the region of the grating by
repositioning the interferometer mirrors. Alternatively, tilting the mirrors out-
ward from their normally vertical positions, means that the beams no longer
interfere in the plane of the zero order (b).

this interferometer, since the orientation of the phase mask determines
whether the two beams will overlap at the fiber, while the cylindrical lens
determines whether or not the overlapping stripes align along the fiber
core. It is important to ensure that the path lengths from the phase mask
to the fiber are identical so that the mutual coherence of the beams is