Abstract: An optical directional coupling apparatus includes an optical directional coupling device for permitting light of a predetermined polarization direction to be emitted from a second port when it is received at a first port of the coupling device, and for permitting only a light component of a polarization direction at a given angle with respect to the first polarization direction to be emitted from a third port when light is received at the second port. A polarization maintaining single mode fiber, is coupled at one end to the second port and has a main axis set at a predetermined angle with respect to the first polarization direction, wherein an optical fiber to be measured is connected at one end to the other end of said polarization maintaining single mode fiber.

Abstract: In an indexing system for a member such as a turret head of a lathe, in which the member after undergoing an indexing movement is locked by a locking bolt thrust by spring force into a bolt hole in a plate coaxially fixed to the member, a hydraulic cylinder is used to exert a great force for holding the locking bolt positively and unmovably in each bolt hole against any reactive counter force from the side of the member due to a great load. The hydraulic cylinder is controllably actuated by a single hydraulic system containing also a hydraulic motor for driving the member in its indexing movement and a solenoid valve.