NOVELTY - Method (M1) of measuring measurand in fiber optic distributed sensor (120) system, comprises: providing fiber optic distributed sensor configured to respond along its length to a measurand of interest, where the sensor has first sections interspaced with second sections, and first sections have enhanced sensitivity to measurand relative to second sections; launching successive optical pulses into the sensor; and detecting backscattered optical signals generated in at least second sections in response to successive optical pulses to determine characteristics of the measurand.    USE - The method is useful for measuring measurand in fiber optic distributed sensor system (claimed) which are useful: in hydrocarbon production applications (i.e. to monitor various characteristics of the surrounding formation and/or hydrocarbon liquid flow); in injection wells for improving hydrocarbon recovery, geothermal wells for energy extraction or storage and wells for carbon dioxide sequestration; intrusion detection systems; and for monitoring the integrity of a structure (e.g. pipeline or other asset that includes volatile fluids at significant pressures and/or temperatures).    ADVANTAGE - The method provides highly sensitive and precision measurements with a high degree of linearity together with a distributed measurement.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) a system (I) comprising: a fiber optic distributed sensor having sections of contrasting sensitivity to a measurand; and an interrogation and acquisition system to launch optical pulses into the fiber optic distributed sensor and to detect coherent Rayleigh noise (CRN) generated in the sections of contrasting sensitivity in response to the launched optical pulses, where the interrogation and acquisition system configured to determine a phase difference between the CRN generated in sections of lower sensitivity surrounding a section of higher sensitivity to determine characteristics of the measurand;    (2) method (M2) for making precision measurements in a distributed fiber optic sensor system, comprising acquiring a distributed measurement of a measurand from an optical fiber sensor configured to respond along its length to the measurand, where the optical fiber sensor has first sections having an enhanced sensitivity to the measurand interspaced with second sections having a reduced sensitivity to the measurand; and    (3) system (II) to determine characteristics of a measurand detected by a distributed fiber optic sensor, comprising an interrogation and data acquisition system having at least one processor and at least one storage medium to store executable code that, when executed by the at least one processor, causes the interrogation and data acquisition system to acquire a distributed measurement of a measurand detected by an optical fiber sensor that responds along its length to the measurand.    DESCRIPTION OF DRAWING(S) - The figure illustrates an exemplary distributed vibration sensor with alternating sections of contrasting sensitivity to a measurand.    Fiber optic distributed sensor (120)    Highly compliant region (128)    Optical fiber (130)    Highly sensitive region (136)    Low-sensitivity regions (138)