Patent ID: 8768121

Claim:
A filter for filtering an electrical signal, comprising: an optical modulator for receiving light at a carrier frequency and for modulating light at a frequency of the electrical signal to obtain light at first and second frequencies; an optical filter for receiving the modulated light and for selecting light at a first frequency to propagate therethrough with at least a fraction of light at the carrier frequency, while suppressing light at the second frequency, the optical filter comprising a dual-band optical filter having a first passband for light at the first frequency and a second passband for light at the carrier frequency; and a photodetector for receiving light filtered by the optical filter and for detecting a signal at a beat frequency between the first frequency and the carrier frequency, wherein the detected signal at the beat frequency comprises an output signal of the filter; wherein the dual-band optical filter comprise first and second optical sub-filters connected in series, wherein the first and the second optical sub-filters each have and second passbands, wherein the passband of the dual-band optical filter comprises an overlap region between the first passbands of the first and the second optical sub-filters; wherein the second passband of the dual-band optical filter comprises an overlap region between the second passbands of the first and the second optical sub-filters; and wherein a central frequency and/or a bandwidth of the first passband of the dual-band optical filter is tunable by adjusting a central frequency of the first passband of the first optical sub-filter, of the second optical sub-filter, or of both first and the second optical sub-filters, whereby the filter for filtering the electrical signal is tunable in frequency and/or bandwidth.