Known examples of coating removing devices to remove a coating of an optical fiber include devices such as those described in Patent Literature 1 and 2. The coating removing devices described in Patent Literature 1 and 2 heat and soften a coating to be removed from an optical fiber, reduce adhesive force between the bare optical fiber and the coating, and remove the coating.
Patent Literature 1: Japanese Unexamined Utility Model Application Publication No. H01-90003
Patent Literature 2: Japanese Unexamined Patent Application Publication No. 2002-328241
FIG. 16A is an explanatory diagram of a manner in which coating removal is performed. A pair of blades 21A, 23A makes incisions in a coating 5 at a coating removal start position. Then, a gripping section (not illustrated described later) that grips an optical fiber 3 on the left side of FIG. 16A is moved such that the blades 21A, 23A pull off the coating 5, and the coating 5 is removed from the optical fiber 3. Since it is necessary to catch the coating 5 with the blades 21A, 23A during removal of the coating 5, a gap between the pair of blades 21A, 23A is set narrower than the thickness of the coating 5 (the diameter of the optical fiber 3), and slightly wider than the diameter of a bare optical fiber 4.
Due to the gap between the pair of blades 21A, 23A being wider than the diameter of the bare optical fiber 4, the bare optical fiber 4 moves up and down when pulling the coating 5 off, and the blades 21A, 23A may make contact with the bare optical fiber 4. The hardness of the blades 21A, 23A is accordingly set lower than the hardness of the bare optical fiber 4 so as to suppress damage to the bare optical fiber 4. As a result, the blade tips gradually wear with repeated removal of the coating 5.
If the coating 5 is removed using the worn blades 21A, 23A, an issue of not being able to completely remove the coating 5, and part of the coating 5 remaining on the bare optical fiber 4, arises. In cases in which part of the coating 5 remains on the bare optical fiber 4 and a subsequent cleaning process is not able to completely remove the coating 5, the coating 5 remaining on the surface of the bare optical fiber 4 might combust in a weld connection process, reducing the long-term reliability of the optical fiber 3.
Moreover, if, as illustrated in FIG. 16B, the coating 5 is removed in a state in which one of the blades (the lower side blade 21A in FIG. 16B) has become worn, a timing at which the worn blade 21A splits the coating 5 is delayed, and slippage occurs between the worn blade 21A and the coating 5. This results in an issue of force acting on the bare optical fiber 4 becoming unbalanced. When unbalanced force acts on the bare optical fiber 4, bending of the bare optical fiber 4 or excessive pressing of the bare optical fiber 4 against the upper blade 23A might occur, reducing the long-term reliability of the optical fiber 3.
In order to prevent issues such as those described above, it is desirable to replace the blades when the blades become worn. However, due to the difficulty in assessing the amount of wear of the blades by sight, it is easy to perform coating removal without noticing that the blades are due for replacement.