Distributed optical fiber sensing technologies and corresponding instruments have been greatly developed in the recent 30 years.Many instruments such as optical time domain reflectometry(OTDR),Brillouin optical time domain reflctometry(BOTDR),Brillouin optical time domain analyzer(BOTDR),Raman Optical time domain reflectometry(ROTDR),coherent optical time domain reflectometry(COTDR),optical frequency domain reflectometry(OFDR)and so on have been playing important roles in structure health monitoring and other fields needing distributed status parameter sensing.However,these distributed optical fiber sensing instruments produced by different companies or institutes do not follow the same standards and their structure has huge difference.To build a universal structure standard for the distributed optical fiber sensing instruments(OFSI),a concept which adopts functionally divided modules to define OFSI is proposed and its feasibility is discussed.Generally,OFSI can be divided into five functional modules: controller module,pulse generator module,photo-electric module,signal gathering and processing modules and standard processing chassis module.Then the characteristics of OFSI are embodied mostly by the photo-electric modules.The novel method makes full use of the common functional parts and enhances the flexibility of OFSI,which can reduce the cost of OFSI.Additionally,to produce an instrument by functionally divided modules is a technical trend,and it will promote the standardized development of OFSI.