Patent ID: 7821712

Claim:
A tunable optical filter, comprising: (a) a separator for spatially separating an input optical signal and an output optical signal traveling in opposite directions but sharing a same optical path; (b) an optical means for spectrally splitting the input optical signal comprising a plurality of wavelengths into a drop optical signal comprising one or more wavelengths of said plurality of wavelengths, and the output optical signal comprising remaining wavelengths of said plurality of wavelengths; (c) an optical means for directing the output optical signal back to the separator along the said same optical path; and (d) a means for tuning the tunable optical filter to select said one or more wavelengths; wherein: (i) the optical means for spectrally splitting comprises an optical thin-film filter (TFF), (ii) the optical means for directing comprises a rotatable mirror and a spatially fixed mirror; (ii) the optical TFF and the rotatable mirror are spaced apart and are free to rotate; (iv) the rotatable mirror is arranged to be parallel to the optical TFF; and (v) the means for tuning comprises a means for rotating the optical TFF and the rotatable mirror synchronously by the same angle.