An optical connecting device for a surgical instrument including a coupling for connecting first and second optical fiber bundles. The coupling including: a tubular sleeve having an outer surface defining an internal space for receiving an end of the first optical fiber bundle in the internal space of the tubular sleeve; a clamp movably disposed on the outer surface of the tubular sleeve, the clamp having one or more of a first convexity and a first concavity; and a union having one or more of a second convexity and a second concavity. The clamp has a continuous longitudinal opening along its longitudinal extension and on its outer side such that the clamp can be elastically deformed in a radial direction, and the clamp is configured to elastically deform such that one or more of the first convexity and the first concavity engages with one or more of the second convexity and the second concavity of the union.