Abstract: The invention relates to a plate heat exchanger (1) for a process engineering system (2), having a plurality of lamellae (3, 4) and a plurality of separating plates (5-7), which are arranged alternately, wherein at least one separating plate (6) has an optical waveguide (35) that is embedded in the at least one separating plate (6) in such a way that the optical waveguide (35) is covered on both sides by material of the at least one separating plate (6) in a first direction (R1) and in a second direction (R2), which are each oriented perpendicular to a plane (E) defined by the at least one separating plate (6) and in opposite senses with respect to one another.

Abstract: The present invention concerns a method for producing a plate heat exchanger (1) with a multiplicity of parting sheets (20) and a multiplicity of fins (11, 12), a fin being respectively arranged between two neighboring parting sheets, wherein at least one capillary (30) with at least one thermocouple and/or measuring resistor element (40) is introduced into at least one parting sheet (20), and wherein in each case a parting plate of the multiplicity of parting plates and a fin of the multiplicity of fins are alternately arranged and are connected to one another in a material-bonding manner, and concerns a plate heat exchanger (1) produced in such a way.