Abstract: A method of controlling a polar optical transmitter comprising a dual-branch Mach-Zehnder (MZ) modulator driven by a pair of independent electrical drive signals. A cost function is provided which defines a relationship between a control parameter of the optical transmitter and a power level of an output optical signal generated by the MZ modulator. A selected component of the electrical drive signals is dithered using a predetermined dither signal. A modulation depth of the output optical signal power level corresponding to the dither signal is detected, and the control parameter adjusted based on the cost function and the detection result.

Abstract: A method of controlling a polar optical transmitter comprising a dual-branch Mach-Zehnder (MZ) modulator driven by a pair of independent electrical drive signals. A cost function is provided which defines a relationship between a control parameter of the optical transmitter and a power level of an output optical signal generated by the MZ modulator. A selected component of the electrical drive signals is dithered using a predetermined dither signal. A modulation depth of the output optical signal power level corresponding to the dither signal is detected, and the control parameter adjusted based on the cost function and the detection result.

Abstract: A method of controlling a polar optical transmitter comprising a dual-branch Mach-Zehnder (MZ) modulator driven by a pair of independent electrical drive signals. A cost function is provided which defines a relationship between a control parameter of the optical transmitter and a power level of an output optical signal generated by the MZ modulator. A selected component of the electrical drive signals is dithered using a predetermined dither signal. A modulation depth of the output optical signal power level corresponding to the dither signal is detected, and the control parameter adjusted based on the cost function and the detection result.

Abstract: A method of controlling a polar optical transmitter comprising a dual-branch Mach-Zehnder (MZ) modulator driven by a pair of independent electrical drive signals. A cost function is provided which defines a relationship between a control parameter of the optical transmitter and a power level of an output optical signal generated by the MZ modulator. A selected component of the electrical drive signals is dithered using a predetermined dither signal. A modulation depth of the output optical signal power level corresponding to the dither signal is detected, and the control parameter adjusted based on the cost function and the detection result.

Abstract: Provided by the invention is a fast, continuously variable AGC that can be used to control the gain of an optical amplifier. The AGC is designed around a controller having control coefficients that may be dynamically adjusted according to operating conditions. According to an embodiment of the invention provided is an AGC that can operate at much higher speeds in comparison with prior art AGC designs that have fixed control coefficients, while simultaneously maintaining stability over all operating conditions.

Abstract: In method of controlling an optical amplifier dynamically adapts to both configuration and performance changes of a communications system. An error vector is calculated to indicate a difference between respective detected values and target values of a parameter of a light beam downstream of the optical amplifier. A sensitivity matrix indicative of a sensitivity of the detected parameter value to incremental changes in a control variable of the optical amplifier is calculated. A predicted optimum value of the control variable is then calculated using the error vector and the sensitivity matrix. Calculation of the predicted optimum control variable value can be iterative, with the sensitivity matrix calculated either during each iteration, or at the beginning of each optimization run. As a result, optimization of the amplifier control variables is performed based on a sensitivity matrix that accurately reflects the performance of the amplifier.

Abstract: A structural component having a stiffness which can be actively varied to control vibrations, for example in a helicopter rotor, an aircraft wing or tail, or in a robotic manipulator. The component has at least one recess or notch with opposed walls, which walls, in the absence of any intervening member, tend to move relative to each other when the component is stressed. A stiffness control element is situated in the recess or notch, this element comprising electrically or magnetically expandable material capable of being rapidly expanded from a first condition in which the element is out of contact with one of the walls, to an expanded condition in which the element extends across the recess or notch and transmits forces from one of the walls to the other, thus altering the stiffness of the component. The preferred expandable material is a stack of piezoelectric crystals.