Based on light intensity modification in optical fibers and optical time-domain reflectometry techniques, a proprietary and patented structural monitoring system has been developed. Featuring continuously-distributed spatial coupling of a proprietary optical fiber sensor with a structure, by means of attachment or embeddment, the system can monitor both the magnitude and location of structurally-related changes in strain, pressure or temperature. All measurements are made at a terminal connected to one end of the distributed sensor and located on or near the structure, or remotely operated. Four categories of systems, by length, are outlined. The descriptive term "FIBERTRONICtm System" has been selected for the various groupings of sensor and terminal designs. Initially directed toward structural integrity monitoring for strain, a prototype system has been demonstrated by sensor attachment to a 16-foot "I" beam in uniform bending. Another prototype, involving pressure sensing, was embedded in a pultruded graphite-epoxy composite to determine survivability under high pressure and temperature, as well as to locate a simulated void. Test data are included. Current developments include both sensor and terminal refinements for medium-length, short-length and ultra-short systems. These include pressure-sensor-diameter reduction, pressure tests over short sensor lengths and insertion-loss tests on a Fiber Optic Rotary Joint (FORJ). References are included for more detailed referral, including a companion paper (SPIE 986-14) which reported on a "Smart" aerospace structure utilizing a FIBERTRONICtm pressure sensor.