The present invention relates to an electronic gastrointestinal capsule protected by an outer biocompatible shell resistant to the environment in the digestive system comprising a light source (4)； splitting means (5) to split the light beam, directing it to the reference arm (6) and the sampling arm (9)； an adjustable group delay element (24) depending on the distance to the tissue to analyse； optical moving means moving the intersection of the light beam (30) of the sampling arm (9) across the tissue； an optical system (8) focusing the light beam (30) from the sampling arm (9) on the tissue； interference means (10) producing interference between the reflected light； a detector (11) receiving said interference； processing means (2) processing the information acquired by the detector (11)； and power supply means (3) supplying power to the capsule without a physical connection to the outside.
