According to one embodiment, an optical filter has a polarization rotator
and two instances of an optical bandpass filter (OBPF). The first
instance of the OBPF processes a TE-polarized component of an optical
input signal to produce a first filtered signal. The polarization rotator
then transforms the TE polarization of the first filtered signal into the
TM polarization. The polarization rotator also transforms the
polarization of a TM-polarized component of the optical input signal into
the TE polarization. The second instance of the OBPF processes the
resulting TE-polarized signal to produce a second filtered signal. The
first and second filtered signals having TM and TE polarizations,
respectively, are then combined to produce a filtered output signal.