A data-collecting system structured to obtain information about at least one portion of a target, the system comprising: an optoelectrical element including an optical fiber element having a core, a coating surrounding the core, an optical axis, a proximal end, and a distal end, the optical fiber element containing a multi-mode optical fiber structured to transmit light between the proximal and distal ends, and an electrical member embedded within the coating along the optical axis to electrically connect the proximal and distal ends; an optical coupling unit at the distal end; and a transducer disposed at the distal end and electrically connected to the electrical member, the transducer being operable to receive first energy, generated in response to excitation light that has been transmitted from the proximal end to the distal end along said multi-mode optical fiber and outcoupled from the distal end toward the target, and to convert the received first energy to an electrical signal to be transmitted along the electrical member, wherein the optical fiber element is configured to collect, through the optical coupling unit, fluorescent radiation generated at said at least one portion of the target in response to irradiation of said at least one portion with the excitation light through the optical coupling unit, said system being a catheter. an optoelectrical element including an optical fiber element having a core, a coating surrounding the core, an optical axis, a proximal end, and a distal end, the optical fiber element containing a multi-mode optical fiber structured to transmit light between the proximal and distal ends, and an electrical member embedded within the coating along the optical axis to electrically connect the proximal and distal ends; an optical fiber element having a core, a coating surrounding the core, an optical axis, a proximal end, and a distal end, the optical fiber element containing a multi-mode optical fiber structured to transmit light between the proximal and distal ends, and an electrical member embedded within the coating along the optical axis to electrically connect the proximal and distal ends; a transducer disposed at the distal end and electrically connected to the electrical member, the transducer being operable to receive first energy, generated in response to excitation light that has been transmitted from the proximal end to the distal end along said multi-mode optical fiber and outcoupled from the distal end toward the target, and to convert the received first energy to an electrical signal to be transmitted along the electrical member, wherein the optical fiber element is configured to collect, through the optical coupling unit, fluorescent radiation generated at said at least one portion of the target in response to irradiation of said at least one portion with the excitation light through the optical coupling unit, said system being a catheter. to receive first energy, generated in response to excitation light that has been transmitted from the proximal end to the distal end along said multi-mode optical fiber and outcoupled from the distal end toward the target, and to convert the received first energy to an electrical signal to be transmitted along the electrical member,