A multimode long period fiber Bragg grating (LPFBG) for a predetermined wavelength band. The LPFBG formed of a non-photosensitive material having an initial index of refraction. The multimode optical fiber core includes a substantially cylindrical surface, a longitudinal core axis, a core radius, and...http://www.google.se/patents/US20060093012?utm_source=gb-gplus-sharePatent US20060093012 - Multimode long period fiber Bragg grating machined by ultrafast laser direct writing
