Abstract: A method of generating a pulse width modulated (PWM) signal receives digital demand data comprising at least one more significant bit and at least one less significant bit. The PWM signal comprises a sequence of one or more frames, each frame comprising a plurality of PWM pulses whose duty cycle is substantially governed by the at least one more significant bit. At least one of its PWM pulses is selected to have its duty cycle modified in response to the at least one less significant bit. Each of the at least one less significant bit uniquely mapping onto the at least one selected PWM pulse of the frame. An apparatus operable according to this method includes an optical attenuator whose optical attenuation is dependent upon its temperature and in which the temperature and, hence, the attenuation is controlled using the above PWM signal.

Abstract: A method of generating a pulse width modulated (PWM) signal comprises: receiving digital demand data Vcontrol comprising at least one more significant bit (bit7 to bit14) and at least one less significant bit (bito to bit). The PWM signal comprises a sequence of one or more frames (100), each frame: comprising a plurality of PWM pulses (W1 to W127) whose duty cycle is substantially governed by the at least one more significant bit (bit7 to bit14); and having at least one of its PWM pulses selected to have its duty cycle modified in response to the at least one less significant bit (bit0 to bit6); each of the at least one less significant bit (bit0 to bit6) uniquely mapping onto the at least one selected PWM pulse of the frame (100). The invention is also concerned with apparatus operable according to the above method and an optical attenuator whose optical attenuation is dependent upon its temperature and in which the temperature an hence attenuation is controlled using the above PWM signal.

Abstract: A method of generating a pulse width modulated (PWM) signal receives digital demand data comprising at least one more significant bit and at least one less significant bit. The PWM signal comprises a sequence of one or more frames, each frame comprising a plurality of PWM pulses whose duty cycle is substantially governed by the at least one more significant bit. At least one of its PWM pulses is selected to have its duty cycle modified in response to the at least one less significant bit. Each of the at least one less significant bits uniquely mapping onto the at least one selected PWM pulse of the frame. An apparatus operable according to this method includes an optical attenuator whose optical attenuation is dependent upon its temperature and in which the temperature and, hence, the attenuation is controlled using the above PWM signal.

Abstract: A method of generating a pulse width modulated (PWM) signal comprises: receiving digital demand data Vcontrol comprising at least one more significant bit (bit7 to bit14) and at least one less significant bit (bit0 to bit6). The PWM signal comprises a sequence of one or more frames (100), each frame: comprising a plurality of PWM pulses (W1 to W127) whose duty cycle is substantially governed by the at least one more significant bit (bit7 to bit14); and having at least one of its PWM pulses selected to have its duty cycle modified in response to the at least one less significant bit (bit0 to bit6); each of the at least one less significant bit (bit0 to bit6) uniquely mapping onto the at least one selected PWM pulse of the frame (100). The invention is also concerned with apparatus operable according to the above method and an optical attenuator whose optical attenuation is dependent upon its temperature and in which the temperature an hence attenuation is controlled using the above PWM signal.

Abstract: The present invention provides an optical attenuator comprising an optical attenuator module, an optical splitter, a detector and a control unit. Input radiation (Pi) is received at the attenuator module which is operable to attenuate the input radiation to generate corresponding attenuated radiation (Po). The detector is operable to receive a portion of the attenuated radiation (0.1 Po) and generate a corresponding electrical signal T1. The signal T1 is applied by the control unit via a first feedback loop to regulate the attenuator module so that radiation power of the attenuated radiation is maintained to a predetermined level. In a situation where an interruption of the input radiation (Pi) occurs, the control unit is operable to monitor temperature of the attenuator module using a thermistor sensor and to regulate the temperature of the module using a second feedback loop to a predetermined temperature during the interruption.

Abstract: The present invention provides an optical attenuator comprising an optical attenuator module, an optical splitter, a detector and a control unit. Input radiation (Pi) is received at the attenuator module which is operable to attenuate the input radiation to generate corresponding attenuated radiation (Po). The detector is operable to receive a portion of the attenuated radiation (0.1Po) and generate a corresponding electrical signal T1. The signal T1, is applied by the control unit via a first feedback loop to regulate the attenuator module so that radiation power of the attenuated radiation is maintained to a predetermined level. In a situation where an interruption of the input radiation (Pi) occurs, the control unit is operable to monitor temperature of the attenuator module using a thermistor sensor and to regulate the temperature of the module using a second feedback loop to a predetermined temperature during the interruption.