The invention provides an 
optical fiber sensing method which takes a full-scale distribution type and has locally and highly precise collineation, and a 
system of the 
optical fiber sensing method comprises the parts of a Brillouin sensing 
demodulation device, a 
fiber grating demodulation device, an 
optical switch (or a coupler) and an FRP-FBG-OF sensing probe, etc. One or a plurality of 
fiber gratings are written onto an ordinary single mode 
fiber with arbitrary length and made into the sensing probe through the encapsulation of FRP, and the sampling 
optical switch or the coupler is respectively connected with the fiber 
grating demodulation device and a Brillouin 
distributed testing system, thus forming an intelligent sensing 
monitoring system which implements the large-scale, full-distributed and locally and highly precise testing of structural damage, achieves the full-scale damage positioning and quantitative testing of important projects and the mutual checking effect, and provides complete, direct and reliable information for 
structural safety evaluation. The 
optical fiber sensing method is especially applicable to structural damage monitored objects which are characterized by wide distribution range, long distance and concealed position, etc., and has the advantages of compact 
system, low cost, strong 
operability, good stability and durability and reliable result, etc.