Abstract: A fault management system for an access network forms part of a public telecommunications network. In the access network, terminating lines in the form of pairs of copper wires extend from a local switch through a series of nodes to terminal equipment provided for user of the network. The fault management system includes a test head and an access network management system. Each night, the test head performs a series of test on each of the terminating lines. The results of the test are transmitted to the access network management. The test results are then converted into circuit scores, each of which is indicative of the operational quality of the tested circuit. For each node, the circuit scores of the tested circuits passing through the node are combined to produce a node score which is indicative of the operational quality of the node. In order to identify the node having the worst operational quality and therefore most in need of investigation, the nodes are ranked in accordance with their node scores.

Abstract: An optical test apparatus includes an optical time domain reflectometer for launching light pulses into a test fibre. An optical amplifier is provided in the light path between the optical time domain reflectometer and the test fibre or amplifying the light pulses. An optical switch is positioned in the light path between the amplifier and the test fibre for preventing light reaching the test fibre between the light pulses launched by the OTDR. Timing structure is provided for synchronising the operation of the optical switch so as to open the switch as a light pulse reaches the switch and close the switch as a light pulse leaves the switch.

Abstract: A method is described of detecting loss in a branched optical fibre network comprising a first optical fibre (1) and a plurality of second optical fibres (3) each of which is coupled to the first optical fibre. The first optical fibre (1) constitutes a main line. The method comprises the steps of launching a pulse into the main line (1) and monitoring the main line for changes in attenuation of reflected signals returning from the reflectors (5).

Abstract: An apparatus and method for introducing a transmission line (5) into a duct (1) through which it is to be propelled by viscous drag of a fluid propellant. A high local flow of fluid is created by inputting fluid, preferably compressed air, adjacent the input of the transmission line to the duct and bleeding a proportion of the fluid from the duct a short distance along from the input. This local flow provides the driving force to progress the transmission line along the first third of the duct against the hydrostatic potential. The extent of the venting via the bleed valve is controllable to control the driving force on the transmission line (5). This technique is especially useful for transmission lines including optical fibres.

Abstract: 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.