A Selectable Multiband Bandpass Microwave Photonic Filter

Abstract

A multiband bandpass microwave photonic filter (MPF) whose passband number and position can be selected is theoretically analyzed and experimentally demonstrated. The proposed MPF is based on a wide-band optical source (WBOS) and a two-order highbirefringence fiber loop mirror (HB-FLM), which serves as a slicing filter. Two segments of high-birefringence fiber (HBF) with the lengths of 3 m and 6 m are used in the HB-FLM, and three typical spectral periods or their combinations can be independently achieved by simply adjusting the polarization controllers (PCs) in the HB-FLM. Subsequently, the light source is sliced with uniform or mixing wavelength spacing. A coil of single-mode fiber (SMF) is then used to act as a dispersive medium to introduce time delay between taps. Thus, a single or multiband bandpass response is obtained at the output of a high-speed photodetector (PD). In addition, the passband centered at dc frequency is removed due to the use of phase modulation. All of the radio frequency (RF) characteristics of the proposed MPF show good agreement with the theoretical prediction. It has the merits of good flexibility, high spectrum efficiency, and great potential of extension.

Tunable Multiband Microwave Photonic Filters

“…With careful design, the high-order comb profile can be used as a spectral slicer for generating multi-wavelength optical carrier with multiple interleaved combs. Figure 6a shows the architecture of a high-order loop mirror filter with two segments of high-birefringent fiber [21]…”

“…With careful design, the high-order comb profile can be used as a spectral slicer for generating multi-wavelength optical carrier with multiple interleaved combs. Figure 6a shows the architecture of a high-order loop mirror filter with two segments of high-birefringent fiber [21], where the resultant comb profile is adjustable by the polarization controller in between the two pieces of high-birefringent fibers. The number of passband in the microwave photonic filter depends on the number of interleaving optical comb (with different comb spacings) in the high-order loop mirror filter.…”

A tunable dual-passband microwave photonic filter based on optical slicing and dual-path fiber delay lines

“…Most techniques mentioned above to realize MPFs are not applicable for this kind of multi-passband MPFs, since most of them have periodic frequency responses and their passbands move simultaneously when tuning the MPFs by changing their free spectrum ranges (FSR). Recently, a novel microwave photonic filter with selectable passbands and tunability based on double slicing of the broadband optical source and dispersive medium has been proposed, and MPF with selective and non-periodic passbands has been realized in their experiment [21,22]. In this technique, two finely adjustable Mach-Zehnder interferometers based on two high-birefringence fiber loop mirrors are needed.…”

Cascaded fiber Sagnac loop-based microwave photonic multiband bandpass filter with a selectable passband frequency

“…For a dual-passband MPF based on a spectrally sliced broadband optical source (BOS) that is sliced by a fiber Mach-Zehnder interferometer (FMZI), the dual-passband frequency response has been realized by utilizing two dispersive fiber delay lines of different length and recombining two groups of delayed samples on the photodetector (PD) [13] . A microwave photonic multiband bandpass filter with three reconfigurable passbands has also been demonstrated, where the passband reconfigurability is achieved by manually adjusting the polarization controllers (PCs) [14] . Moreover, a tunable and selectable multiband MPF utilizing reflective and cascaded FMZI has been demonstrated, the passband selection can be realized via rotating the PCs within reflective and cascaded FMZIs, and the central frequency of the passband can be tuned by changing the length of the variable optical delay line (VODL) in the FMZI [15] .…”

“…The spectrum slicer as shown in Fig. 1 (dashed box) is a modified structure of two cascaded first-order fiber Sagnac loops [14] . Compared with a second-order fiber Sagnac loop structure, the cascade structure has a higher extinction ratio of the comb spectrum.…”