Optical filter wavelength tuning using raised cosine control signal

A switchable optical device, comprising:

• an optical component for controlling switching functions between one or more input signals and one or more output signals as a function of an applied electrical control signal, the optical component exhibiting a nonlinear response to the applied electrical control signal;
• and
• a control source for providing a raised cosine signal as the electrical control signal input to the component, the raised cosine signal exhibiting a defined rise time associated with minimizing fluctuations in the nonlinear response of the component;
• wherein the optical component exhibits an under-damped second-order oscillatory response approximated by a transfer function defined as:
• H
• ⁡
• (
• ω
• )
• =
• 1
• 1
• +
• 2
• ⁢
• j
• ⁢
• ω
• ⁢
• ζ
• -
• ω
• 2
• ,
• where ζ is defined as a damping factor of the transfer function and exhibits a value less than unity.

A method of wavelength tuning an optical filter, comprising:

• determining a nonlinear response of an optical wavelength filtering element utilized for wavelength tuning;
• selecting a target wavelength for use as the output wavelength from the optical filter;
• determining a target electrical drive signal associated with the selected target wavelength, based on the nonlinear response of the optical wavelength filtering element;
• and
• applying a raised cosine drive signal to the optical wavelength filtering element to tune the wavelength of the optical filter from an initial value to the selected target wavelength;
• where a rise time of the raised cosine drive signal is selected to reach the target wavelength with an oscillation less than a defined percentage of the target in the output signal.

A method of maintaining a selected output wavelength for a tunable optical filter, comprising:

• determining a nonlinear response of an optical wavelength filtering element utilized for wavelength tuning;
• selecting a target wavelength for use as the output wavelength from the optical filter;
• applying a first raised cosine drive signal to the optical wavelength filtering element for tuning the wavelength of the optical filter from an initial value to a value near the selected target wavelength;
• applying a second raised cosine drive signal to the optical wavelength filtering element for scanning an optical output wavelength across a wavelength band including the target wavelength and recording an optical output power at identified wavelengths within the wavelength band;
• determining a final raised cosine drive signal as associated with a recorded maximum output power;
• and
• applying a third raised cosine drive signal to the optical wavelength filtering element to tune the optical filter to the maximum output power value.

A tunable optical filter, comprising:

• a nonlinear optical filter component exhibiting a nonlinear time domain response, the optical filter component responsive to a multi-wavelength input optical signal and an electrical drive signal, the electrical drive signal for tuning an output wavelength of the tunable optical filter from an initial wavelength value to a selected target wavelength value, the nonlinear filter component exhibiting an oscillatory response to the electrical drive signal;
• and
• a control source for providing a raised cosine signal as the electrical drive signal input to the nonlinear optical filter component, the raised cosine signal exhibiting a defined rise time associated with minimizing the extent of the oscillatory response of the nonlinear filter component;
• wherein the rise time of the raised cosine drive signal is selected to reduce oscillations to a defined percentage of the selected target wavelength value during a defined settling time period, the defined settling time period less than the settling time period associated with a step function waveform drive signal.

A method of wavelength tuning an optical filter, comprising:

• determining a nonlinear response of an optical wavelength filtering element utilized for wavelength tuning;
• selecting a target wavelength for use as the output wavelength from the optical filter;
• determining a target electrical drive signal associated with the selected target wavelength, based on the nonlinear response of the optical wavelength filtering element;
• and
• applying a raised cosine drive signal to the optical wavelength filtering element to tune the wavelength of the optical filter from an initial value to the selected target wavelength;
• wherein the optical wavelength filtering element includes a MEMS tuning mirror and the determined nonlinear response takes the form of a highly under-damped second order oscillation.