Abstract: A communication protocol is proposed, to be used by a main station and a plurality of mobile sub-stations, while time slots are used in which data packets are transmitted. A sub-station that has a message to be sent to the main station first transmits a request-for-access data packet to the main station. If the sub-station knows its own position as well as that of the main station, the sub-station applies an advancement of time to the request-for-access data packet, so that this may be longer and contain more information, such as a self-selected recognition code and/or information relating to the length of the message to be sent.The main station measures the instant at which the request-for-access data packet is received relative to the time slot distribution and sends a correction of the advancement of time to the sub-station.

Abstract: In the PCVD method glass layers are deposited on the inner wall of a glass tube by heating the tube to a temperature between 1100.degree. and 1300.degree. C., passing a reactive gas mixture at a pressure between 1 and 30 hPa through the glass tube, and moving back and forth inside the glass tube a plasma. After the glass layers are deposited, the glass tube is collapsed to produce a solid preform from which optical fibers are drawn. The regions of nonconstant deposition geometry at the ends of the preform (taper) are reduced by moving the plasma in the area of at least one reversal point nonlinearly with time and/or by changing the longitudinal extent of the plasma as a function of time. The length of the ramp is chosen to ensure an effective reduction of the end taper.