Fitting system for introducing an optical fibre transport line into a gas line (12, 12'), comprising: - a shaped body - having a pipe section which has a first and a second end respectively for connection to a gas line (12, 12'), wherein the pipe section surrounds a duct running from the first to the second end, and - having a branch pipe end extending laterally from the pipe section and surrounding a branch duct extending from the duct to a branch opening, and - a branch closure adapted to the branch pipe end for closing the branch opening, wherein the branch closure has a through channel for passing an optical fibre transport line therethrough, - wherein the branch closure is configured in the form of a branch plug having an insertion part which is provided to be inserted into the branch duct of the branch pipe end and the outer contour of which is adapted to the inner contour of the branch pipe end, - wherein connecting means (50, 52) corresponding to one another are provided on the branch closure and on the branch pipe end to produce a force-fitting and/or form-fitting connection between the branch pipe end and the branch closure, characterised in that - the branch closure has a cover part which is provided to be slipped over the branch pipe end and the inner contour of which is adapted to the outer contour of the branch pipe end, and - a heating coil wire is provided on the branch pipe end and/or on the insertion part of the branch closure for producing a heating coil weld between the branch pipe end and the branch closure. - a shaped body - having a pipe section which has a first and a second end respectively for connection to a gas line (12, 12'), wherein the pipe section surrounds a duct running from the first to the second end, and - having a branch pipe end extending laterally from the pipe section and surrounding a branch duct extending from the duct to a branch opening, and - having a pipe section which has a first and a second end respectively for connection to a gas line (12, 12'), wherein the pipe section surrounds a duct running from the first to the second end, and - having a branch pipe end extending laterally from the pipe section and surrounding a branch duct extending from the duct to a branch opening, and - a branch closure adapted to the branch pipe end for closing the branch opening, wherein the branch closure has a through channel for passing an optical fibre transport line therethrough, - wherein the branch closure is configured in the form of a branch plug having an insertion part which is provided to be inserted into the branch duct of the branch pipe end and the outer contour of which is adapted to the inner contour of the branch pipe end, - wherein connecting means (50, 52) corresponding to one another are provided on the branch closure and on the branch pipe end to produce a force-fitting and/or form-fitting connection between the branch pipe end and the branch closure, - the branch closure has a cover part which is provided to be slipped over the branch pipe end and the inner contour of which is adapted to the outer contour of the branch pipe end, and - a heating coil wire is provided on the branch pipe end and/or on the insertion part of the branch closure for producing a heating coil weld between the branch pipe end and the branch closure.