The invention relates to an interventional apparatus comprising an interventional device with a handle (6). The handle comprises a) a first guide (20, 51) guiding an optical fiber, which is also guided within the interventional device, from a first proximal opening (14) of the handle to a distal portion (21) of the handle, wherein the first guide only has radii of curvature being larger than 10 mm, and b) a second guide (22) for guiding an elongated interventional instrument from a second proximal opening (13) of the handle to the distal portion of the handle. Since the first guide is relatively straight, the optical fiber is substantially not bent or only slightly bent and the likelihood that the interventional instrument and the optical fiber press against each other can be significantly reduced. This allows for an improved accuracy of determining the position of the interventional device by optical shape sensing.