POSITION WEIGHTING OF FIBER BRAGG GRATINGS FOR BANDPASS FILTERING

A fiber Bragg grating bandpass filter with tailored refractive-index m odulation is investigated. The writing method includes a position weig hting technique, which provides flexible and accurate control of the i ndex modulation along the fiber. This weighting is accomplished by adj usting the positions of a large number of overlapping subgratings to c ontrol the local grating strength. A 10-cm grating with a truncated si n(x)/x refractive-index modulation function was written and characteri zed with this method, showing good agreement with simulations. These t ypes of filter are well suited for wavelength-division-multiplexing ap plications and can be made to have steep edges, low sidelobes, large b andwidth, and low stopband ripple. (C) 1997 Optical Society of America .