The fiber optic sensors one can subordinate to class with open optical track, closed and half-open track. The sensor of D type is interesting construction and belongs to the last group. This sensor name comes from implemented in the head fiber optic core transverse intersection shape. A sensor of this type using range is detection of liquid type. The sensor head construction elaboration is the basic question of classic optical sensor synthesis. In peculiarity this problem concerns: the optical fiber selection, length and depth of D type area so to the transmission of optical radiation prove the sensibility on for looked extent, which has the touch with the head. In presented work authors show solution of this problem with use of intensity method on the sample of the sensor that recognize the juice from black currant with specified parameters.