Fiber-optic liquid level sensing system based on a titanium diaphragm extrinsic Fabry-Perot interferometer and microwave photonic filter

An approach is considered to estimate direction of arrival of broadband microwave signals in linear phased array antenna with photonic beamforming system by using additional subsystem – microwave photonic filter. The frequencies of the notches in the spectrum of broadband signal at the microwave photonic transversal filter output allow to measure mutual delay between signals from two antenna array elements, and thus providing estimation of the signal arrival angle . Architecture of the constructed transversal filter is based on the components of two analog fiber-optic links being a part of antenna array photonic beamforming system. Some shown results of test measurements of microwave photonic transversal filter characteristics prove out an operability of the technique.

Tunable single notch microwave photonic filter based on delay lines

<p>\n\tA reconfigurable microwave photonic filter (MPF) based on an integrated Kerr comb source was proposed and demonstrated. By employing an on-chip micro-ring resonator (MRR), a broadband Kerr comb with a large number of comb lines was generated and used as a high-quality multi-wavelength source for the MPF, which greatly reduced the size and cost. The enhanced performance of the MPF was theoretically analysed and systematically characterized. Due to the large channel number and high reconfigurability of the scheme, the MPF features an improved Q factor and wideband tunability. The experimental results matches well with theory, verifying the feasibility of our approach as a solution towards implementing highly reconfigurable MPFs with reduced system complexity. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.</p>

A tunable and reconfigurable bandpass microwave photonic filter (MPF) is demanded in scenarios where different center frequencies and bandwidths are required. Here, we propose and demonstrate a silicon-on-insulator (SOI)-based microwave photonic bandpass filter, whose center frequency and bandwidth can be adjusted. The MPF is implemented by using four cascaded microring resonators (MRRs) that fabricated based on SOI wafer. Each MRR combines the design of multi-mode waveguides and tunable coupling regions, thereby exhibiting simultaneous high frequency selectivity and excellent reconfigurability. The center frequency can be tuned by adjusting the resonant wavelengths of the MRRs, and the bandwidth can be reconfigured by adjusting the coupling coefficients as well as the resonant wavelengths of the MRRs. The operation state of each MRR can be monitored and thus the MPF can be adjusted precisely. In the experiment, the bandwidth and center frequency of the MPF are adjusted from 0.7 to 2 GHz and from 5.2 to 35.8 GHz, respectively. During the adjustment, the rejection ratio of the MPF remains above 40 dB. The link performance, including the link gain, noise figure and spurious-free dynamic range, are also charactered. The achieved MPF can be potentially applied to radar, sensor networks, and wireless communications.

Microwave photonic (MWP) filters are essential components in microwave systems due to their wide bandwidth, low loss, and immunity to electromagnetic interference. Steep roll‐off is critical for precise spectral shaping and effective interference suppression, yet conventional MWP filters face challenges in simultaneously achieving steep transitions and high reconfigurability. Here, reconfigurable MWP filters with steep roll‐off based on a transversal filter structure using an optical microcomb source are demonstrated. Four different types of single‐band MWP filters with ultrahigh roll‐off rates up to ∼32.6 dB/GHz and a minimum 20‐dB shape factor of ∼1.15 are achieved. In addition, simply through programming tap coefficients, band‐pass filters with tunable centre frequencies ranging from 5 to 15 GHz and dual‐band MWP filters with various filter responses are demonstrated without changing any hardware, where steep roll‐off is also validated. The reconfigurable MWP filters with steep roll‐off offer a stable and versatile solution for applications requiring high spectral selectivity, such as next‐generation wireless networks, high‐resolution radar imaging, and advanced biomedical sensing.

Microwave photonic (MWP) filters are essential components in microwave systems due to their wide bandwidth, low loss, and immunity to electromagnetic interference. A sharp transition band is critical for precise spectral shaping and interference suppression, yet conventional MWP filters face challenges in achieving both sharp transitions and high reconfigurability. Adaptive MWP filters with sharp transition based on a transversal filter structure using an optical microcomb source are demonstrated in this paper. Four different types of single-band MWP filters with roll-off rates up to ~32.6 dB/GHz and a minimum shape factor of ~1.15 are achieved. In addition, simply through designing tap coefficients, band-pass filters with tunable centre frequencies ranging from 5 GHz to 15 GHz and dual-band MWP filters with various filter response are demonstrated without changing any hardware, where sharp transition is also validated. The adaptive filters with sharp transition presented in this paper offer a stable and highly reconfigurable solution for applications requiring stringent spectral selectivity, such as next-generation wireless networks, high-resolution radar imaging, and advanced biomedical photonic sensing.

Microwave photonic (MWP) filters are essential components in microwave systems due to their wide bandwidth, low loss, and immunity to electromagnetic interference. A sharp transition band is critical for precise spectral shaping and interference suppression, yet conventional MWP filters face challenges in achieving both sharp transitions and high reconfigurability. Adaptive MWP filters with sharp transition based on a transversal filter structure using an optical microcomb source are demonstrated in this paper. Four different types of single-band MWP filters with roll-off rates up to ~32.6 dB/GHz and a minimum shape factor of ~1.15 are achieved. In addition, simply through designing tap coefficients, band-pass filters with tunable centre frequencies ranging from 5 GHz to 15 GHz and dual-band MWP filters with various filter response are demonstrated without changing any hardware, where sharp transition is also validated. The adaptive filters with sharp transition presented in this paper offer a stable and highly reconfigurable solution for applications requiring stringent spectral selectivity, such as next-generation wireless networks, high-resolution radar imaging, and advanced biomedical photonic sensing.

A general theoretical model for microwave photonic filters based on multi-wavelength light source and dispersive media is summarized and presented, and is applied to the analysis of double-laser-based microwave photonic notch filters’ performance. The different influences of the double-sideband(DSB) modulation and the single-sideband(SSB) modulation are demonstrated and explained theoretically. Furthermore, the impact of different factors, such as frequency spacing, 3dB bandwidth and the spectrum amplitude mismatch on the performance of the microwave photonic notch filters are also studied. The numerical simulation results are in good agreement with predictions, and could be beneficial for future optimization of microwave photonic filters.

Microwave photonic filters are fundamental parts in microwave frequency signal processing. The possibility of microwave photonic filters to be integrated in a monolithic chip is highly appealing due to more compact size, weight and lower power consumption. We demonstrate a highly-integrated microwave photonic bandpass filter with wide-frequency tunable range. Both active and passive components including a phase modulator, four cascaded microring resonators and a photodetector, are integrated on a silicon photonic chip. The integrated filter has a wide tunable range from 6.08 GHz to 35.92 GHz and a reconfigurable bandwidth from 0.22 GHz to 0.54 GHz. Spurious-free dynamic range is also measured to examine the link performance. This work is a solid step towards the implementation of an on-chip miniaturized microwave signal processing system.

We report a fully integrated microwave photonic passband filter on a silicon photonic chip. The on-chip integrated microwave photonic filter (IMPF) consists of a high-speed phase modulator (PM), a thermally tunable high-Q micro-disk resonator (MDR), and a high-speed photodetector (PD). The bandpass filtering function of the IMPF is implemented based on phase modulation and phase-modulation to intensity-modulation conversion, to translate the spectral response of an optical filter, which is the MDR in the IMPF, to the spectral response of a microwave filter. By injecting a CW light from a laser diode (LD) to the PM, a passband IMPF with a broad tuning range is demonstrated. Thanks to the ultra-narrow notch of the MDR, a passband IMPF with a 3-dB bandwidth of 2.3 GHz is realized. By thermally tuning the MDR, the center frequency of the IMPF is tuned from 7 to 25 GHz, achieving a tuning range of 18 GHz at a power consumption of 1.58 mW. This successful implementation of an IMPF marks a significant step forward in full integration of microwave photonic systems on a single chip and opens up avenues toward real applications of microwave photonic filters.

We propose and experimentally demonstrate a fully tunable microwave photonic narrow bandpass filter based on phase modulation to intensity modulation (PM-IM) conversion. In the filter implementation, an on-chip dual-drive microring resonator (MRR) is a key component. This resonator leverages a multimode waveguide to enable a high Q-factor. A metallic micro-heater and a lateral PN junction are simultaneously created for resonance wavelength tuning. When one driving signal is applied to the micro-heater, a large tuning range of the resonance wavelength is resulted; when another driving signal is applied to the PN junction, a fast tuning speed of the resonance wavelength is caused. By jointly using two different tuning mechanisms, the realized microwave photonic filter features a large frequency tuning range as well as a fast tuning speed. In addition, the filter bandwidth can also be tuned. A silicon-based dual-drive high-Q racetrack MRR chip is designed, fabricated, and evaluated. By incorporating the chip in a microwave photonic filter system, a bandpass filter with a narrow bandwidth of 1.27 GHz is achieved. An ultra-wide frequency tuning range from 3 to 51 GHz, an ultra-fast tuning speed less than 0.54 ns, and a tunable bandwidth from 1.27 to 4.47 GHz is experimentally demonstrated. This fully tunable filter offers significant potential in future radar and next-generation wireless communication applications.

An on-chip frequency-tunable bandpass microwave photonic filter (MPF) implemented on a silicon photonic platform is reported. The on-chip MPF consists of a high-speed phase modulator (PM), a thermally tunable high-Q micro-disk resonator (MDR), and a high-speed photodetector (PD). The filtering function of the MPF is realized based on phase modulation and phase modulation to intensity modulation conversion, to translate the spectral response of the MDR in the optical domain to the spectral response of the MPF in the microwave domain. The tunability of the MPF is realized by thermally tuning the MDR. The proposed on-chip bandpass MPF is fabricated and characterized. An MPF with a passband of 1.93GHz and a tunable range from 3 to 10GHz is demonstrated. The power consumption, the insertion loss, and the bandwidth over the entire tunable range are studied. This successful implementation of an MPF marks a significant step forward in the full integration of microwave photonic systems on a single chip.

A microwave photonic notch filter with a complex coefficient is proposed and demonstrated based on four wave mixing (FWM). FWM effect of two single-frequency laser beams occurs in a highly nonlinear fiber (HNLF), and multi-wavelength optical signals are generated and used to generate the multi-tap of microwave photonic filter (MPF). The complex coefficient is generated by using a Fourier-domain optical processor (FD-OP) to control the amplitude and phase of the optical carrier and phase modulation sidebands. The results show that this filter can be changed from bandpass filter to notch filter by controlling the FD-OP. The center frequency of the notch filter can be continuously tuned from 5.853 GHz to 29.311 GHz with free spectral range (FSR) of 11.729 GHz. The shape of the frequency response keeps unchanged when the phase is tuned.

A widely tunable microwave photonic notch filter with adjustable bandwidth based on multi-wavelength fiber laser is proposed and demonstrated. The multi-wavelength fiber laser generates the multi-taps of the microwave photonic filter (MPF). In order to obtain notch frequency response, a Fourier-domain optical processor (FD-OP) is introduced to control the amplitude and phase of the optical carrier and phase modulation sidebands. By adjusting the polarization controller (PC), different numbers of taps are got, such as 6, 8, 10 and 12. And the wavelength spacing of the multi-wavelength laser is 0.4 nm. The bandwidth of the notch filter is changed by adjusting the number of taps and the corresponding bandwidths are 4.41 GHz, 3.30 GHz, 2.64 GHz and 2.19 GHz, respectively. With the additional phase shift introduced by FD-OP, the notch position is continuously tuned in the whole free spectral range (FSR) of 27.94 GHz. The center frequency of the notch filter can be continuously tuned from 13.97 GHz to 41.91 GHz.

A high-speed optically controlled microwave photonic (MWP) reconfigurable dual-band filter is presented, which is achieved using a Lyot loop filter for spectrum slicing and ultrafast nonlinear polarization rotation (NPR) effect in a semiconductor optical amplifier for high-speed tuning. Through the control of optical pump power, the MWP filter is switchable between four different operation states-all-block state, dual-band state, and single-band state with two different passband frequencies. The use of NPR greatly increases the tuning speed of the MWP filter to gigahertz range, making it capable for high-speed tuning in dynamic multiband applications. The four operation states and high-speed adjustment significantly improve operation flexibility of the filter. Furthermore, good passband quality is also obtained that the sidelobe suppressions of both passbands are over 40 dB with clean and sharp passband profiles, providing good filter selectivity.