| 摘要 |
PROBLEM TO BE SOLVED: To prevent twist in a SZ-grooved rod by the resistance of a phase detection butt strap. SOLUTION: A pseudo phase detection butt strap 3' is arranged in a position detached from the phase detection butt strap 3 by the odd number of times of the inversion pitch P of the grooves apart from the phase detection butt strap 3 as a groove phase detection part 15 which directly detects the phase of the groove 1 of the SZ-grooved rod 2. The phase detection butt strap 3 and the pseudo phase detection butt strap 3' have the same structure and they are in ring shapes having projections engaged into the grooves 1 of the SZ-grooved rod 2. The phase detection butt strap 3 is the rotary part of an encoder. Since the two butt straps 3 and 3' are detached by the odd number of times as much as an inversion pitch P, directions becoming resistance to the grooves 1 of the SZ-grooved rod 2 become opposite and resistances which the SZ-grooved rod 2 receives from the butt straps 3 and 3' are canceled (F1-F2=0), and thus force causing the twist of the SZ-grooved rod 2 is not generated. Since a twist does not occur in the SZ-grooved rod 2, a coated optical fiber can smoothly be stored in the groove 1 the SZ-grooved rod 2.
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