Multi-tap Microwave Photonic Filter Research Articles

Multitap microwave photonic filter based on a DFB laser array using photonic wire bonding

We propose and experimentally demonstrate a multitap microwave photonic filter (MPF) based on a distributed feedback (DFB) laser array using photonic wire bonding (PWB). Through the application of the PWB technique, an eight-wavelength DFB laser array with wavelength spacing of 400 GHz was hybrid-integrated with an arrayed waveguide grating multiplexer. Remarkably, the insertion losses of all eight channels are maintained below 5 dB. In the experiments, the larger wavelength spacing allowed us to achieve a sinc MPF with a lower 3 dB bandwidth of 0.22 GHz using only eight taps. Further, Gaussian apodization enabled the out-of-band rejection of the filter to reach 24 dB. These results indicate that the proposed scheme could provide a promising guideline for the MPFs that demand high reconfigurability and greatly reduced size and complexity.

Photonic compressive sensing with a micro-ring-resonator-based microwave photonic filter

A novel approach to realize photonic compressive sensing (CS) with a multi-tap microwave photonic filter is proposed and demonstrated. The system takes both advantages of CS and photonics to capture wideband sparse signals with sub-Nyquist sampling rate. The low-pass filtering function required in the CS is realized in a photonic way by using a frequency comb and a dispersive element. The frequency comb is realized by shaping an amplified spontaneous emission (ASE) source with an on-chip micro-ring resonator, which is beneficial to the integration of photonic CS. A proof-of-concept experiment for a two-tone signal acquisition with frequencies of 350MHz and 1.25GHz is experimentally demonstrated with a compression factor up to 16.

Sidelobe Suppression Enhancement of Radiofrequency Photonic Filters via Time-to-frequency Mapping

We present a multi-tap microwave photonic filter with high selectivity through applying time-to-frequency mapping and optical frequency comb shaping techniques. When arranged in the time-to-frequency mapping stage, by a Fourier transform, the deviation of the optical taps to the target profile is significantly reduced while maintaining the apodization profile, resulting in high sidelobe suppression in the filters. By applying a simple time-to-frequency mapping stage to the conventional optical frequency combs, we demonstrate a substantially enhanced (>10dB) sidelobe suppression, resulting in filter lineshapes exhibiting a significantly high (>40dB) main lobe to sidelobe suppression ratio. These results highlight the potential of the technique for implementation in various passband filters with high sidelobe suppression.

All-Optical Tunable Multitap Microwave Photonic Filter Enabled by Fiber Optical Parametric Amplifier

We propose and experimentally demonstrate an all-optical tunable microwave photonic filter (MPF) based on single pump fiber-based optical parametric amplifier (OPA). The delay-line structure is achieved with a spool of dispersion-compensating fiber and a simple time-delay-compensating element. Owing to the idler generation during the OPA process, the frequency responses of 2-tap, 4-tap, and 8-tap MPFs are experimentally achieved by one, two, and four signal laser sources, respectively. Thus, ~50% reduction on the number of laser sources is accomplished. The tunability of the filter transfer function can be achieved through either continuously tuning the wavelength spacing of the signals or changing the total dispersion value.

Reconfigurable microwave photonic filter with negative coefficient based on an optoelectronic oscillator

We report a reconfigurable multi-tap microwave photonic filter with negative coefficient based on an optoelectronic oscillator (OEO). The key novelty of this work is that a single polarization modulator (PolM) is used to build the OEO as well as to generate a multi-wavelength optical source. Thus, an external microwave source which is usually involved in the generation of multi-wavelength optical source by externally modulating a single tone optical beam is saved. In addition, the spectrum of the multi-wavelength optical source is reconfigurable in terms of the number of the optical components and the frequency interval between the adjacent components. The negative coefficient of the microwave photonic filter is achieved using a phase modulator (PM) and a dispersive element. The proposed approach is theoretically analyzed and experimentally verified. The generated fundamental microwave signal has a frequency of 9.95GHz and a phase noise of −118dBc/Hz at 10kHz offset. By adjusting the optical power inside the OEO loop and the polarization controller (PC) outside the OEO loop, the tap number of the microwave photonic filter can be adjusted from 2 to 5, leading to a reconfigurable microwave photonic filter. The measured frequency responses of the microwave photonic filters agree well with the simulated ones.

Multi-tap microwave photonic filter with positive and negative coefficients based on an unbalanced Mach-Zehnder modulator

A novel approach for the implementation of microwave photonic filter with positive and negative coefficients based on an unbalanced Mach-Zehnder modulator (MZM) is proposed. In the proposed filter, a microwave signal to be filtered is applied to an unbalanced MZM. Thanks to the unbalance between the two arms of the modulator, a π phase shift is obtained by adjusting the wavelength interval between the adjacent wavelengths, which leads to the generation of the positive and negative coefficients. The theoretical fundamentals of the design are described, which show that the required unbalanced MZM in the scheme can be well fabricated by the current technology, and the required other components, including the wavelength multiplexer, are also commercially available devices. An eight-tap microwave photonic filter with positive and negative coefficients is demonstrated. The tunability and reconfigurability of the eight-tap microwave photonic filter are also investigated to verify our approach.

Tunable multi-tap microwave photonic filter with complex coefficients using a dual-parallel Mach–Zehnder modulator

We propose and demonstrate a tunable multi-tap microwave photonic filter (MPF) with complex coefficients. It is based on addition of carrier suppressed single sideband (CS-SSB) signal and phase-controllable optical carrier. Instead of using the technique of optical filtering, the CS-SSB signal is generated by a dual-parallel Mach–Zehnder modulator (DPMZM) in our scheme. Frequency tuning of the filter is achieved by changing the phase of the optical carrier, which can be controlled by a variable optical delay line (VDL). The proposed structure features high flexibility and wideband RF response, and the experimental results demonstrate that it can be tuned continuously over one free spectral range (FSR) without changing the spectral shape of the filter.

Multitap Microwave Photonic Filter With Negative Coefficients Based on the Inherent Birefringence in a $\hbox{LiNbO}_{3}$ Phase Modulator

A novel technique to implement a multitap microwave photonic filter with positive and negative coefficients based on the inherent birefringence in a LiNbO3 phase modulator is proposed and demonstrated. In the proposed filter, a microwave signal is applied to the phase modulator and an optical polarizer is connected at the output of the phase modulator to perform polarization interference and phase-modulation to intensity-modulation (PM-IM) conversion. Thanks to the inherent birefringence in the LiNbO3 crystal, a π phase shift is obtained by adjusting the wavelength spacing between two adjacent wavelengths, which leads to the generation of a positive coefficient and a negative coefficient. An equivalent experiment is performed. Four-tap and six-tap microwave photonic filters with positive and negative coefficients are experimentally demonstrated. The reconfigurability of the four-tap and six-tap microwave photonic filters is also investigated.

Tunable multitap microwave photonic filter with all complex coefficients

Architecture for the implementation of a tunable multitap microwave photonic filter (MPF) with all complex coefficients is proposed and demonstrated. The complex coefficients are realized by 360° tunable photonic microwave phase shifters based on single-sideband polarization modulation. The polarization modulator, wavelength-division multiplexers, polarizer, and photodetector required for achieving the tunable phase shift are shared by all taps. Only a polarization controller is required in each tap to adjust each phase shift independently, making the system simple and compact. A proof-of-concept experiment is performed. A four-tap MPF with full free spectral range tunability and adjustable filter shape is realized.

A single source microwave photonic filter using a novel single-mode fiber to multimode fiber coupling technique

In this paper we present a fully tunable and reconfigurable single-laser multi-tap microwave photonic FIR filter that utilizes a special SM-to-MM combiner to sum the taps. The filter requires only a single laser source for all the taps and a passive component, a SM-to-MM combiner, for incoherent summing of signal. The SM-to-MM combiner does not produce optical interference during signal merging and is phase-insensitive. We experimentally demonstrate an eight-tap filter with both positive and negative programmable coefficients with excellent correspondence between predicted and measured values. The magnitude response shows a clean and accurate function across the entire bandwidth, and proves successful operation of the FIR filter using a SM-to-MM combiner.

Tunable and reconfigurable multi-tap microwave photonic filter based on dynamic Brillouin gratings in fibers

We propose and experimentally demonstrate new architectures to realize multi-tap microwave photonic filters, based on the generation of a single or multiple dynamic Brillouin gratings in polarization maintaining fibers. The spectral range and selectivity of the proposed periodic filters is extensively tunable, simply by reconfiguring the positions and the number of dynamic gratings along the fiber respectively. In this paper, we present a complete analysis of three different configurations comprising a microwave photonic filter implementation: a simple notch-type Mach-Zehnder approach with a single movable dynamic grating, a multi-tap performance based on multiple dynamic gratings and finally a stationary grating configuration based on the phase modulation of two counter-propagating optical waves by a common pseudo-random bit sequence (PRBS).

Multitap microwave photonic filters with programmable phase response via optical frequency comb shaping

We present a programmable multitap microwave photonic filter with an arbitrary phase response operating over a broad bandwidth. Complex coefficient taps are achieved by optical line-by-line pulse shaping on a 10 GHz flat optical frequency comb using a novel interferometric scheme. Through high-speed real-time measurements, we demonstrate programmable chirp control of a waveform via phase filtering. This achievement enables us to compress broadband microwave signals to their corresponding bandwidth-limited pulse duration.

Tunable complex-valued multi-tap microwave photonic filter based on single silicon-on-insulator microring resonator

A complex-valued multi-tap tunable microwave photonic filter based on single silicon-on-insulator microring resonator is presented. The degree of tunability of the approach involving two, three and four taps is theoretical and experimentally characterized, respectively. The constraints of exploiting the optical phase transfer function of a microring resonator aiming at implementing complex-valued multi-tap filtering schemes are also reported. The trade-off between the degree of tunability without changing the free spectral range and the number of taps is studied in-depth. Different window based scenarios are evaluated for improving the filter performance in terms of the side-lobe level.

Tunable Programmable Microwave Photonic Filters Based on an Optical Frequency Comb

We demonstrate the application of optical combs to implement tunable programmable microwave photonic filters. We design well-known multi-tap microwave photonic filters; however, the utilization of an optical comb with a dispersive medium enables scaling of these filters to a large number of taps. We use optical line-by-line pulse shaping to program tap weights, which allows us to shape the filter's bandpass. Our scheme is simple and easily implementable, which provides filters with arbitrary tap weights. As an example, we implement filters with Gaussian apodized tap weights, which achieve more than 35-dB sidelobe suppression. Our experiments provide usable bandwidth, free of sampling spurs, over a Nyquist zone of 5 GHz, equal to half of our 10-GHz comb repetition frequency. Furthermore, we introduce a simple new technique, based on a programmable optical delay line, to uniformly tune the passband center frequency across the free spectral range (FSR) of the filter, ideally without changing the bandpass shape. We demonstrate this scheme by tuning the filter over a full FSR, equal to 10.4 GHz in our experiments.

Tunable and reconfigurable multi-tap microwave photonic filter with negative coefficients based on a single laser diode

A tunable and reconfigurable multi-tap microwave photonic filter with negative coefficients is proposed and demonstrated. The baseband resonance is eliminated by an electro-optic phase modulator co ...

A microwave photonic filter using a switchable multiple dual-wavelength erbium-doped fiber laser

A multi-tap microwave photonic filter is proposed and experimentally demonstrated. The filter is based on a switchable multiple dual-wavelength erbium-doped fiber laser with a narrowband polarization maintaining (PM) Fabry–Perot filter (FPF) as the wavelength selection component. The tunability feature of the filter is also demonstrated through switching of the laser between multiple dual-wavelengths and a normal multiwavelength laser.

Bandpass multitap microwave photonic filter with a round‐trip configuration

AbstractWe propose a novel bandpass microwave photonic multitap filter configuration using a section of Hi‐Bi fiber in a round‐trip configuration. The configuration makes use of a chirped FBG both as a mirror and a dispersive device. Measured results are presented to show a two‐tap and three‐tap filter response, with a notch rejection greater than 35 dB and tunability of the level of secondary sidelobes by adjusting a polarization controller. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1181–1184, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23330