Abstract: A demodulator includes a splitter, a first dielectric substance, and a combiner. The splitter splits a differential phase shift keying optical signal into a first light beam and a second light beam and outputs the first light beam to a first optical path and the second light beam to a second optical path. The first dielectric substance is disposed in the first optical path and has a refractive index higher than the average refractive index of the second optical path. The combiner combines the first light beam and the second light beam and causes the beams to interfere with each other. The difference in length between the first and second optical paths and the refractive index of the first dielectric substance are set such that the first light beam is delayed by one bit with respect to the second light beam.

Abstract: A coupling element has a first interface, which is adapted to mechanically connect the coupling element to an actuator, a second interface, which is adapted to mechanically connect the coupling element to a valve, and a deformable portion, which is shaped in such a manner, that, as a result of a compression along an axial direction of the coupling element, the deformable portion irreversibly bends such that a projection is formed. Thereby, the projection is adapted to permanently engage with an annular groove formed at the actuator, such that the coupling element and the actuator are connected with each other in a non-detachable but rotatable manner.

Abstract: A bidirectional communication system which provides a wide variety of communication services to meet the needs of broadcast audiences. Each client terminal sends a service request message over a communications network and receives authorization, and after that, it transmits and receives the video information. A client management server receives service request messages from clients and executes a two-stage authentication process to grant authorization to them. A video data communication server transmits and receives the video information to/from the requesting clients when their identity has successfully been authenticated.