Fig. 1. Three structures for PMF design. (a) PMF operating at the coherent regime; (b) PMF operating at the incoherent regime; (c) PMF based on the mapping of optical response. (E/O, electro-optic conversion; PD, photodetector.)

Fig. 2. Operation principle for the bandstop PMFs based on the RF cancellation technique.

Fig. 3. Schematic diagram of the bandpass PMF with ultra-high ORR when using the amplified recirculating delay line and windowing technique. (OFS, optical frequency shifter; WDE, wavelength-dependent element; PD, photodetector.)

Fig. 4. Schematic diagram of bandpass PMF with ultra-high ORR when using a Gaussian-shaped optical frequency comb (OFC).

Fig. 5. Operation principles for the bandpass PMFs: the direct spectrum mapping (top) and phase modulation to intensity modulation (PM-IM) conversion (bottom). (OC, optical carrier; OBPF, optical bandpass filter; ONF, optical notch filter.)

Fig. 6. Operation principle of the bandpass PMF using the polarization modulation and polarization pulling effect. Optical spectra of polarization modulation when (a) switching off or (c) switching on the SBS processing. RF spectral responses of the PMF when (b) switching off or (d) switching on the SBS processing. x and y represent two orthogonal polarization states. ΩB is the Brillouin frequency shift. OC, optical carrier; O/E, optic-electronic conversion.

Fig. 7. Measured RF response of the bandpass PMF with a record high ORR of 80 dB.

Table 1. Selected Bandstop PMFs with Rejection Ratio Higher than 40 dB

Table 2. Selected Bandpass PMFs with an Out-of-band Rejection Ratio Higher than 40 dB