The invention consists of a secure data transmission cable for electronically transmitting secure data between remote locations in an exposed condition. The data transmission cable comprises a tubular outer protective layer, an inner core disposed within the outer protective layer, a data transmission line carried within the inner core for transmitting secure data between the remote locations, and a fiber optic sensor line included in the outer protective layer for detecting unauthorized activity relative to the transmission line. The fiber optic data transmission line comprises a plurality of optical fibers for transmitting data between remote locations and for detecting unauthorized activity relative to the transmission line. A protective casing surrounds the data transmission line for protecting the fiber optic data transmission line from contacting the outer protective layer. An outer protective casing braided around the core in which the sensor line is enclosed provides strength to the cable.