Conventional Optoelectronic Oscillator Research Articles

Wideband frequency-tunable optoelectronic oscillator with ultra-narrow linewidth based on stimulated Brillouin scattering

We propose and theoretically analyze a wideband frequency-tunable optoelectronic oscillator based on stimulated Brillouin scattering (SBS) and gain–loss superposition with ultra-narrow linewidth. Typically, the linewidth of optoelectronic oscillator (OEO) based on SBS is difficult to narrow because of the relatively fixed 3-dB bandwidth of SBS. In the structure, three generated new pump lights with certain frequency intervals generated by optical modulation on the pump laser light are launched in a highly nonlinear fiber (HNLF) from the direction opposite to the phase modulated signals, where the SBS effect occurs. The gain spectrum of one pump light is superimposed with the loss spectra of the other two pump lights. As a result the linewidth of the output signal reduces highly compared with conventional OEOs based on SBS. Consequently, a microwave signal with wide tunable range of 1 GHz to 40 GHz and near 60% linewidth reduction at most is realized in theory. Particularly, the theoretical simulation of the phase noise is about −112.5 dBc/Hz at 10 kHz offset when the wavelength of the continuous wave laser is 1550 nm and the frequency of the output signal is 35 GHz. In addition, the proposed method can be generalized, theoretically, to any OEO based on SBS to effectively reduce its linewidth. Overall, the proposed structure improves the quality of generated signals prominently and has vast potential in microwave generation.

Hybrid-integrated wideband tunable optoelectronic oscillator.

As a photonic-based microwave signal generation method, the optoelectronic oscillator (OEO) has the potential of meeting the increasing demand of practical applications for high frequency, broadband tunability and ultra-low phase noise. However, conventional OEO systems implemented with discrete optoelectronic devices have a bulky size and low reliability, which extremely limits their practical applications. In this paper, a hybrid-integrated wideband tunable OEO with low phase noise is proposed and experimentally demonstrated. The proposed hybrid integrated OEO achieves a high integration level by first integrating a laser chip with a silicon photonic chip, and then connecting the silicon photonic chip with electronic chips through wire-bonding to microstrip lines. A compact fiber ring and an yttrium iron garnet filter are also adopted for high-Q factor and frequency tuning, respectively. The integrated OEO exhibits a low phase noise of -128.04 dBc/Hz @ 10 kHz for an oscillation frequency of 10 GHz. A wideband tuning range from 3 GHz to 18 GHz is also obtained, covering the entire C, X, and Ku bands. Our work demonstrates an effective way to achieve compact high-performance OEO based on hybrid integration, and has great potential in a wide range of applications such as modern radar, wireless communication, and electronic warfare systems.

Actively mode-locked optoelectronic oscillator for microwave pulse generation

The optoelectronic oscillator (OEO) is the most widely investigated microwave photonic hybrid system for the generation of microwave signal with high frequency and low phase noise. It has been considered a reasonable and promising solution for obtaining pure microwave signal. Generally, a conventional OEO is used for the generation of only continuous microwave signal owing to the long mode building time of the oscillation cavity, leading to limited application areas. Here, the concept of actively mode-locking in fiber laser is introduced into the OEO, in which an external microwave signal with the frequency integral multiple of the free spectral range of OEO is injected to achieve a mode-locked condition. In this case, an OEO that can directly generate pulsed microwave signal with adjustable central frequency and time duration is demonstrated. Furthermore, by changing the frequency of the injection signal, harmonic mode locking with different orders can be easily achieved, while supermodes are confined. The proposed OEO has great potential in applications such as radars, communications and metrology.

Active mode-locking optoelectronic oscillator.

The optoelectronic oscillator (OEO) has been widely investigated to generate ultra-pure single-frequency microwave signals. In this study, we propose and experimentally demonstrate an active mode-locking optoelectronic oscillator (AML-OEO), which can generate broadband microwave frequency comb (MFC) signals. An additional intensity modulator is inserted into the OEO as an active mode-locking device for loss modulation to realize phase-locking between adjacent oscillation modes. Through the active mode-locking technique, steady multi-mode oscillation is achieved, which is difficult to realize in a conventional OEO due to the mode-competition effect. By tuning the frequency of the active modulation signal (AMS), both fundamental and harmonic AML-OEOs can be established. In the experiments, MFC signals with a frequency spacing of 195 kHz and 50.115/100.035 MHz are generated with fundamental and harmonic AML-OEOs.

Control of coexisting periodic oscillations in an optoelectronic oscillator

We investigate the dynamics of a modified optoelectronic oscillator (OEO) through theoretical and numerical analysis. The OEO under study is different from the conventional OEO in the sense that it contains a van der Pol oscillator (VDPO) in its feedback loop, in place of the RF band pass filter. Two coexisting limit cycle oscillations are identified, known as birhythmicity. Subsequently, a simple self-feedback scheme is introduced to control the birhythmic behavior of the oscillator. To the best of our knowledge, the control of birhythmicity in an intrinsic time-delayed oscillator has not been studied earlier.

The Simplest Laser-Based Optoelectronic Oscillator: An Experimental and Theoretical Study

We present a theoretical and experimental study of the most simple autonomous optoelectronic oscillator (OEO) with a delayed feedback loop. Contrarily to the overwhelming majority of OEOs, our OEO does not use an external intensity- or phase-modulator to translate the electrical radio-frequency signal into the optical domain. Instead, we show that the electric signal can simply be used as a driving pump current of the laser that is seeding the oscillator. With this architecture, the intensity modulation is performed through the piecewise-linear (that is, nonlinear) power-intensity transfer function of the laser-diode, instead of the sinusoidal transfer function of the usual Mach–Zehnder modulators. We provide a model to investigate the dynamics of this simple architecture of OEO. This model is an integro-differential delay equation which is characterized by three timescales as in the conventional OEO, namely the low/high-cutoff frequencies of the wideband filter and the time delay. The stability analysis of our OEO reveals a complex bifurcation behavior which critically depends on the gain of the feedback loop. In particular, we show that a sequence of Hopf bifurcations may lead to fast-scale oscillations with a period which is the double of the time-delay, or to slow-scale oscillations with a period which depends on the three aforementioned timescales. Our theoretical results are shown to be in excellent agreement with numerical simulations and the experimental measurements.

Multifrequency optoelectronic oscillator

We propose a simple and cost-effective multifrequency optoelectronic oscillator (OEO) which is able to simultaneously generate two or more independent microwave signals by adding parallel filtering branches in the feedback loop. In the experimental demonstration, two signals with frequencies of 20 and 9 GHz are suc- cessfully generated. Compared with a conventional OEO, the generated signals have no additional noise and do not interfere with each other. The side-mode suppression by the optical dual-loop configuration is effective for both channels. The measured side-mode suppression ratios are larger than 65 dB, and the phase noises at a 10-kHz frequency offset are −108 and −113 dBc∕Hz for 20 and 9-GHz signals, respectively. © 2014 Society of Photo-

Experimental optimization of phase noise performance of optoelectronic oscillator based on directly modulated laser

The experimental optimization of a 10 GHz optoelectronic oscillator (OEO) based on a 1.55 μm directly modulated distributed feedback (DFB) laser is demonstrated in this paper. The phase noise of the directly modulated laser (DML) based OEO is significantly reduced by proper selection of the laser’s bias current and by using a dispersion shifted fiber as a delay line. The phase noise performance of the DML OEO achieved after optimization is close to that of a conventional OEO constructed using a commercial DFB laser and a LiNbO3 Mach-Zehnder modulator. The DML based OEO is most promising for future realization of a miniature OEO architecture with the components integrated on a semiconductor substrate.

High-Performance Photonic Microwave Downconverter Based on a Frequency-Doubling Optoelectronic Oscillator

Photonic microwave downconversion based on an optoelectronic oscillator (OEO) is interesting because the local oscillator signal is directly extracted from the RF signal, but some of the frequency components in the RF signal would leak to the oscillation signal due to the limited rejection ratio of the electrical bandpass filter in the OEO, which degrades the downconverted signal. In this paper, a high-performance photonic microwave downconverter based on a frequency-doubling OEO (FD-OEO) is proposed and demonstrated to avoid the direct degradation from the RF signal. A 20-GHz RF signal with 1-Gb/s data modulation is successfully downconverted by the FD-OEO. The phase noise at 10-kHz frequency offset of the extracted RF carrier by the FD-OEO is 14 dB lower than that extracted by a conventional OEO, and the receiver sensitivity of the downconverted signal has a 1.173-dB improvement. The downconverter needs only low-frequency devices, which may find application in phased-array antenna arrays, electronic warfare receivers, avionics, and wireless communication systems.