Guan BO, Ran Y, Feng FR, et al. Formation and applications of the secondary fiber Bragg grating. Sensors 2017; 17: 398–412. 3. Chiang JS, Chang HY, Sun NH, et al. High sensitive two-dimension ...
A short length of optical fiber that ... Lawrence Bragg, noted British physicist (1890-1971) discovered this in his study of x-rays and crystal structures. See diffraction grating and WDM.