Frequency-quadrupled Microwave Signal Research Articles

Tunable frequency-multiplying optoelectronic oscillator based on a dual-parallel Mach-Zehnder modulator incorporating a phase-shifted fiber Bragg grating

A tunable frequency-multiplying optoelectronic oscillator (OEO) based on a dual-parallel Mach-Zehnder modulator (DPMZM) is proposed and experimentally demonstrated. In the proposed system, the tunable fundamental microware signal is generated by a tunable optoelectronic oscillator incorporating a phase-shifted fiber Bragg grating (PS-FBG). By adjusting the DC bias of the DPMZM, the frequency-doubled microwave signal with a tunable frequency range from 11 GHz to 20 GHz and the frequency-quadrupled microwave signal with a tunable frequency range from 22.5 GHz to 26 GHz are generated. The phase noises of the fundamental, frequency-doubled and frequency-quadrupled signals at 10 kHz offset frequency are −105.9 dBc/Hz, −103.3 dBc/Hz and −86.2 dBc/Hz, respectively.

Tunable 360° microwave photonic multichannel phase shifter with frequency quadrupling.

In this paper, a photonic scheme to generate a frequency-quadrupled microwave signal with full-range 360° tunable phase shift is proposed and experimentally demonstrated. Pure ±2nd-order sidebands with the carrier suppressed are generated by a dual-parallel Mach-Zehnder modulator. The two sidebands are separated by a fiber Bragg grating with the polarization state of one sideband rotated by 90deg via a Faraday rotating mirror and then recombined to obtain a pair of orthogonally polarized wavelengths. The two orthogonally polarized optical sidebands are aligned into the same polarization direction by using a polarizer (Pol). Finally, a radio frequency (RF) signal with frequency quadrupling of a local oscillator signal is obtained by beating the ±2nd-order sidebands at a photodetector. The phase θ of the frequency-quadruped RF signal can be independently and arbitrarily adjusted from 0° to 360° through control of the polarization direction. Experiments are carried out to demonstrate the scheme, and frequency-quadrupled microwave signals at 12GHz and 16GHz are generated. A continuous phase shift from 0° to 360° of the frequency-quadrupled signal at 12GHz is also verified. The proposed scheme not only has the merits of large operation bandwidth and simple structure but also can be extended to multi-channel applications.

Frequency-multiplying optoelectronic oscillator with a tunable frequency multiplication technique

An optoelectronic oscillator (OEO) for the generation of a frequency-doubled or -quadrupled microwave signal with a tunable frequency multiplication technique is proposed and demonstrated. In the proposed OEO, a modulated signal is generated by a Mach–Zehnder modulator (MZM). The modulated signal is then divided into two parts. One part is sent to a photodetector (PD1) via an optical domain dual-loop composite cavity and then fed back to the MZM to form the OEO loop that can generate an oscillation signal with the frequency determined by the center frequency of an electrical bandpass filter used in the loop and the length difference of the dual-loop composite cavity. The other part is sent to a fiber-optic recirculating delay line (RDL) structure and then applied to another PD (PD2) for the formation of a microwave photonic (MWP) notch filter. Through using the cascade characteristics of the RDL loop in the fiber-optic RDL structure and the notch response of the MWP notch filter, a frequency-doubled or -quadrupled microwave signal is generated. A detailed theoretical analysis is provided and the results are verified by an experiment. A fundamental oscillation signal at 5.592 GHz is generated in the OEO loop, which is multiplied to generate a frequency-doubled microwave signal at 11.184 GHz or a frequency-quadrupled microwave signal at 22.368 GHz, respectively. The performance of the generated microwave signals is also investigated.

Photonic generation of frequency-octupled and frequency-quadrupled microwave signals using a dual-parallel polarization modulator

An approach to generate microwave signal with tunable frequency multiplication factor (FMF) is presented based on an integratable electro-optic dual-parallel polarization modulator (DPPolM), which consists of a polarization beam splitter, two polarization modulators, and a polarization beam combiner. From a theoretical analysis, the frequency-octupled and frequency-quadrupled microwave signal can be generated respectively depending on the polarization direction of the polarizer after the DPPolM. Simulation results show that the frequency-octupled microwave signal with an optical sideband suppression ratio (OSSR) of 56.36 dB and a radio frequency spurious suppression ratio (RFSSR) of 49.24 dB, the frequency-quadrupled microwave signal with an OSSR of 41.15 dB and a RFSSR of 35.95 dB can be obtained, which match well with the theoretical analysis. The DPPolM based system is simple, compact, and able to generate high FMF microwave signal without an optical filter.

Photonic Generation of Frequency-Quadrupled Microwave Signal With Tunable Phase Shift

A photonic scheme for frequency-quadrupled microwave signal generation with full 360 ° arbitrarily tunable phase shift is proposed and experimentally demonstrated. Two coherent optical components are generated by biasing a Mach-Zehnder modulator at maximum transmission point to suppress odd-order sidebands. Then, two second order sidebands together with the optical carrier are sent to a programmable filter to reject the optical carrier and introduce a phase shift to one of the second order sidebands. A frequency-quadrupled microwave signal with tunable phase is finally obtained by beating the two sidebands at a photodetector. Tunable phase shift of full 360 ° with a microwave frequency from 30 to 42.4 GHz is experimentally demonstrated. The proposed approach has potential applications in the broadband array signal processing system.

Frequency quadrupling optoelectronic oscillator using a single polarization modulator in a Sagnac loop

We propose and demonstrate a novel and cost efficient method to generating a frequency quadrupling optoelectronic oscillator (OEO) using a single polarization modulator (PolM) in a Sagnac loop. The OEO loop and the Sagnac loop share the same PolM. In the OEO loop, the PolM is used to generate the fundamental microwave signal. In the Sagnac loop, the joint use of the PolM, a polarization controller (PC), and a polarization beam splitter (PBS) is equivalent to an intensity modulator. The odd order sidebands of the modulated signal are suppressed by biasing the equivalent intensity modulator at the maximum transmission point. Moreover, the undesired optical carrier is also eliminated by bidirectional use of the PolM. As a result, only the two second order sidebands are left. The beating between the two second order sidebands in a photodetector (PD) generates a microwave signal at the frequency corresponding to four times of the fundamental tone. A frequency quadrupling microwave signal at the frequency of 39.74GHz with a phase noise of −100.14dBc/Hz at 10kHz frequency offset was experimentally generated.