CONTROL METHOD AND APPARATUS

摘要

The propulsive force on an optical transmission line member moving through a tubular passageway can be varied so the line travels at or close to optimum speed without risk of damage to the line or associated apparatus. A curve is provided in a portion of the passageway such that a transmission line subject to unacceptable compressive forces buckles towards the outer side of the curve. A sensor detects the presence or absence of the line at this point and a control circuit varies the propulsive force. Excessive tension in the fibre may also be detected. A modified system uses deflectors to ensure that buckling occurs by bowing in the direction towards the sensor with the transmission line undeflected under correct tension. The invention finds particular application in a method of fibre blowing where an optical fibre transmission line is propelled along a tube by fluid drag.