Patent ID: 7483205

Claim:
A transient optical power suppressor, comprising: a feedforward control loop including an input power splitting element, an input optical power sensing element and a loop controller; a feedback control loop including an output power splitting element, an output optical power sensing element, and said loop controller, wherein said loop controller is a shared controller that controls both the feedforward control loop and the feedback control loop; and a variable optical attenuator operatively coupled to said loop controller and providing a fast response time to suppress transients, said variable optical attenuator receiving an input optical signal and variably attenuating the input optical signal to produce an output optical signal wherein the degree of attenuation varies with the amount of electrical current injected; wherein said variable optical attenuator is coupled between said input power splitting element and said output power splitting element and wherein there are no intervening optical amplifiers; said feedforward control loop comprising means for feedforward control of said variable optical attenuator to reduce optical power transients and maintain a substantially constant output power based on an input optical power measured by said input optical power sensing element and a first reference value; said feedback control loop comprising means for feedback control of said variable optical attenuator to reduce optical power transients and maintain the substantially constant output power based on an output optical power measured by said output optical power sensing element and a second reference value, wherein said first reference value and said second reference value each comprise a value proportional to one of a desired output power level and a desired optical attenuation, and wherein said first reference value and said second reference value are each adjustable by a user; said loop controller comprising a loop filter/processing element configured to improve the dynamic performance of the power/attenuation control loops; said variable optical attenuator having a default opaque state in which the input optical signal is substantially attenuated when power is not being supplied to said variable optical attenuator; and means for biasing said variable optical attenuator to a non-zero value in order to compensate for both positive and negative transients.