Intracore fiber Bragg gratings for strain measurement in embedded composite structures

An intracore Bragg grating written on a photosensitive fiber core is used f or strain measurement in composite specimens under load. The strain informa tion is directly related to the absolute change in the Bragg-reflected wave length. Fiber Bragg grating (FBG) sensors (fibers with intracore gratings) are thus sensitive to strain that is caused by changes in temperature as we ll as to load-induced changes. Thus these sensors can be made to be indepen dent of source intensity variations and losses. FBG sensors used for load-i nduced strain sensing in composite structures and the effects of temperatur e on them are discussed. A detailed account of the use of such embedded str uctures as self-monitoring nondestructive testing devices is given. (C) 200 1 Optical Society of America OCIS codes: 060.2370, 050.0050, 0050.2770, 120 .4290.