Reconfigurable Photonic Filter Research Articles

Fully Reconfigurable Photonic Filter for Flexible Payloads

Reconfigurable photonic filters represent cutting-edge technology that enhances the capabilities of space payloads. These advanced devices harness the unique properties of light to deliver superior performance in signal processing, filtering, and frequency selection. They offer broad filtering capabilities, allowing for the selection of specific frequency ranges while significantly reducing Size, Weight, and Power (SWaP). In scenarios where satellite communication channels are crowded with various signals sharing the same bandwidth, reconfigurable photonic filters enable efficient spectrum management and interference mitigation, ensuring reliable signal transmission. Furthermore, reconfigurable photonic filters demonstrate their ability to adapt to the dynamic space environment, withstanding extreme temperatures, radiation exposure, and mechanical stress while maintaining stable and reliable performance. Leveraging the inherent speed of light, these filters enable high-speed signal processing operations, paving the way to various space payload applications, such as agile frequency channelization. This capability allows for the simultaneous processing and analysis of different frequency bands. In this theoretical study, we introduce a fully reconfigurable filter comprising two decoupled ring resonators, each with the same radius. Each resonator can be independently thermally tuned to achieve reconfigurability in both central frequency and bandwidth. The precise reconfiguration of both central frequency and bandwidth is achieved by using the thermo-optic effect along the whole ring resonator path. A stopband rejection of 45 dB, with a reconfigurable bandwidth and central frequency of 20 MHz and 180 MHz, respectively, has been numerically achieved, with a maximum electrical power of 11.50 mW and a reconfiguration time of 9.20 µs, by using the scattering matrix approach, where the elements have been calculated through Finite Element Method-based and Beam Propagation Method-based simulations. This performance makes the proposed device suitable as key building block of RF optical filters, useful in the next-generation telecommunication payload domain.

Self-configuring programmable silicon photonic filter for integrated microwave photonic processors

Reconfigurable photonic filters show great promise as a potential solution to meet the evolving needs of future microwave communication systems. By integrating high-performance filters into programmable microwave photonic processors, they can provide significant benefits for signal processing applications. The development of an algorithm that can automatically characterize and reconfigure the filter using a single optical input and output port is essential for this purpose. This paper presents an optimization technique for a fully tunable ring-assisted Mach–Zehnder interferometer filter. The proposed filter design eliminates the need for monitoring components and employs a novel algorithm that operates independently in each ring by switching between the two arms of the filter. In addition, the filter can be configured to implement different filter architectures, allowing for flexible filtering requirements. Measurements were performed using the device as an interleaver, implementing different types of infinite impulse response filters in the optical and radio frequency domains. Side-coupled integrated spaced sequence of resonator filters were also implemented by reconfiguring the same device. These results demonstrate the exceptional reconfigurability of the filter design proposed herein in terms of bandwidth and central frequency.

Performance analysis of reconfigurable multifunctional photonic filters using triple coupled microring resonators

In this paper, we have introduced a new device architecture based on triple coupled microring resonators structure. The analytical model of the device is developed and performance analysis is carried out. The novelty of this device is that it performs as a multifunctional reconfigurable photonic filter in which multiple filtering functions such as notch, bandpass and bandstop responses are achieved by programming the coupling coefficients associated with it using thermal or electro optic tuning. Moreover, it can be used as a tuneable photonic true time delay line. As a bandpass reconfigurable filter, the maximally flat-top rectangular shape like bandpass response of 42 dB suppression ratio, and maximally flat-top bandwidth tunability of 1 GHz to 45 GHz are achieved. The notch filter response has an ultra-high rejection ratio of 148 dB. The flat bottom bandstop response has high suppression ratio of 81.5 dB within 7 GHz bandwidth. The device exhibits minimum group delay distortion over 18 GHz bandwidth, and a minimum of 8 ps and a maximum of 58 ps time delay tunability.

Automatic Monitor-Based Tuning of Reconfigurable Silicon Photonic APF-Based Pole/Zero Filters

Reconfigurable photonic filters are promising candidates to meet the requirements of future microwave communication systems. However, sensitivity to process and temperature variations necessitates an automatic calibration solution to enable robust operation. This paper demonstrates fully automatic tuning of silicon photonic all-pass filter (APF)-based pole/zero filters using a monitor-based tuning method that calibrates the initial response by controlling each pole and zero individually via microheaters. The proposed tuning approach calibrates severely degraded initial responses to the designed elliptic filter shapes and allows us for automatic bandwidth and center-frequency reconfiguration of these filters. This algorithm is demonstrated on second- and fourth-order filters fabricated in a standard silicon photonics foundry process. After the initial calibration, only 300 ms is required to reconfigure a filter to a different center frequency. Thermal crosstalk between the microheaters is investigated, with substrate thinning demonstrated to suppress this effect and reduce filter calibration to less than half of the original thick substrate times. This fully automatic tuning approach opens the possibility of employing silicon photonic filters in real communication systems.

Integrated reconfigurable photonic filters based on interferometric fractional Hilbert transforms.

In this paper, we present integrated reconfigurable photonic filters using fractional Hilbert transformers (FrHTs) and optical phase tuning structure within the silica-on-silicon platform. The proposed structure, including grating-based FrHTs, an X-coupler, and a pair of thermal tuning filaments, is fabricated through the direct UV grating writing technique. The thermal tuning effect is realized by the controllable microheaters located on the two arms of the X-coupler. We investigate the 200GHz maximum bandwidth photonic FrHTs based on apodized planar Bragg gratings, and analyze the reflection spectrum responses. Through device integration and thermal modulation, the device could operate as photonic notch filters with 5GHz linewidth and controllable single sideband suppression filters with measured 12dB suppression ratio. A 50GHz instantaneous frequency measuring system using this device is also schematically proposed and analyzed with potential 3dB measurement improvement. The device could be configured with these multiple functions according to need. The reconfigurable structure has great potential in ultrafast all-optical signal processing fields.

Full-field technique for measuring the spectral evolution of reconfigurable photonic filters

This Letter demonstrates a measurement technique based on frequency-to-time mapping and coherent detection, which enables the complete (i.e., amplitude and phase) characterization of dynamically reconfigurable photonic filters. We apply this technique to a unit cell from a silicon CMOS-compatible photonic lattice filter that has a rapidly changing transfer function with an 8.33 ns update time, 120 MHz spectral resolution, and 12 GHz bandwidth. These dynamic measurements allow characterization of transients, thermal effects, filter fidelity, and other time-dependent phenomena during switching.