Abstract: Methods and apparatus for control of variable optical attenuators are described. A method for control of a variable optical attenuator located in an optical link comprising a plurality of optical attenuators. The method comprises determining that an initial calibration step of a variable optical attenuator has been completed, and transmitting a signal indicative of the variable optical attenuator having completed the initial calibration step for receipt by a downstream variable optical attenuator. A method of controlling a variable optical attenuator comprises receiving a signal indicative of an upstream variable optical attenuator having completed an initial calibration step, and initiating calibration of the variable optical attenuator in response to receipt of said signal.

Abstract: Methods and apparatus for control of variable optical attenuators are described. A method for control of a variable optical attenuator located in an optical link comprising a plurality of optical attenuators. The method comprises determining that an initial calibration step of a variable optical attenuator has been completed, and transmitting a signal indicative of the variable optical attenuator having completed the initial calibration step for receipt by a downstream variable optical attenuator. A method of controlling a variable optical attenuator comprises receiving a signal indicative of an upstream variable optical attenuator having completed an initial calibration step, and initiating calibration of the variable optical attenuator in response to receipt of said signal.

Abstract: A method and apparatus suitable for controlling the power of a channel in an optical network are described. A control system for a variable optical attenuator includes a processing element arranged to: (a) receive a signal indicative of the radiation power of an optical signal output from a variable optical attenuator; (b) determine an error signal in dependence upon the received signal and a predetermined target radiation power level; (c) determine a control signal for controlling the attenuation of the variable optical attenuator in dependence upon the error signal and a gain factor; and (d) repeat the operations of (a) to (c). The control system is arranged to utilize a first value of the gain factor during a first time period and a second, lower value of the gain factor during a second time period. Such a control system can be used to control the introduction of a channel in a node of an automatically switched optical network.