Dual-loop Optoelectronic Oscillator Research Articles

Tuneable Photonic Microwave Waveforms Generation Based on a Dual-Loop Optoelectronic Oscillator

Tuneable Photonic Microwave Waveforms Generation Based on a Dual-Loop Optoelectronic Oscillator

Broadband electro-optic chaotic system using coupling mutual feedback for intensity and phase chaos generation

An innovative dual-coupled dispersive electro-optic chaotic system utilizing two interlinked nonlinear feedback loops is introduced and demonstrated experimentally. This system efficiently converts phase chaos into intensity chaos while incorporating dispersion, achieved by integrating a broadband chirped fiber Bragg grating (CFBG) into a dual-loop opto-electronic oscillator (OEO) system. Consequently, this leads to the generation of broadband intensity and phase chaos with heightened complexity. Experimental findings indicate that the system achieved up to 24 GHz of 80% bandwidth and 35.5 GHz of 10 dB bandwidth for intensity chaos carriers, and up to 26 GHz of bandwidth with 40.52 GHz of 10 dB bandwidth for phase chaos carriers. The approach features a straightforward structure and mitigates delay characteristics inherently within the system itself. This two-dimensional chaotic source presents potential for secure communications in high-speed Quadrature Amplitude Modulation (QAM) systems.

Fully Distributed Strain Sensor Based on a Dual-Loop Optoelectronic Oscillator

Fully Distributed Strain Sensor Based on a Dual-Loop Optoelectronic Oscillator

Magnetic Field Measurement With Improved Scale Factor Based on a Dual-Loop Optoelectronic Oscillator With Vernier Effect Using a Cascaded GMM-FBG and Monel-400-FBG

Magnetic Field Measurement With Improved Scale Factor Based on a Dual-Loop Optoelectronic Oscillator With Vernier Effect Using a Cascaded GMM-FBG and Monel-400-FBG

Nonlinear dynamics of the dual-loop optoelectronic oscillator based on polarization multiplexing

This paper focuses on the temporal dynamics of the dual-loop optoelectronic oscillator (OEO) based on polarization multiplexing. The delay-differential equation (DDE) for the dual-loop OEO system is presented for the first time. After employing microwave envelope method to simplify the DDE, the envelope signal equation describing the system dynamics is obtained. Stability analysis of the static solution of the envelope signal equation is also performed, and the gain thresholds for the system to exhibit various dynamic behaviours are calculated. Moreover, the proposed nonlinear dynamics approach reveals the stability of microwave envelope in detail as a function of the feedback gain and coupling coefficient, which indicates that there is not monotonously incremental relationship between envelope amplitude of the ultrapure microwave and the feedback gain. Finally, the experimental measurements confirm the results obtained from the theoretical and numerical analysis.

High-precision temperature-compensated fiber Bragg grating axial strain sensing system based on a dual-loop optoelectronic oscillator with the enhanced Vernier effect.

A temperature-compensated fiber Bragg grating (FBG) axial strain sensor based on a two-dual-loop optoelectronic oscillator (OEO) with the enhanced Vernier effect is proposed and experimentally demonstrated. The sensing head consists of two cascaded FBGs, one of which acts as a sensing FBG to measure both the axial strain and temperature and the other as a reference FBG to detect temperature. Acting as the optical carrier, the reflected optical signal of the sensing head is divided into two paths with opposite dispersion coefficients and slightly different lengths to achieve an enhanced Vernier effect. After being divided by a wavelength division multiplexer, the optical signal launches into two electrical paths with different electrical bandpass filters (EBPFs) for frequency division multiplexing. The EBPF I selects the microwave signal generated by the sensing FBG, while the EBPF II selects the microwave signal generated by the reference FBG. Therefore, the axial strain and temperature can be recovered by recording the microwave frequency within EBPF I, and the temperature can be interrogated by tracking the microwave frequency within EBPF II. The axial strain applied on the sensing FBG can be distinguished by solving the cross-sensitivity matrix. The results show that the sensitivity of the dual-loop OEO is much greater than that of the single-loop OEO. The maximum measurement error for the axial strain is 0.112µε, and the maximum temperature compensation error is as low as 0.024°C in the dual-loop OEO, which is far less than that in the single-loop OEO. The enhanced Vernier effect not only improves the sensitivity, but also reduces the temperature compensation error.

Highly Precise Magnetic Field Measurement Based RF-Assisted Sagnac Interferometer With Tapered Fiber

A radio frequency (RF)-assisted Sagnac interferometer based on a dual-loop optoelectronic oscillator (OEO) is experimentally demonstrated for high-precision magnetic field measurement, in which the tapered fiber covered with the magnetic fluid (MF) as the magnetic field sensing head is embedded in the Sagnac interferometer. The evanescent field of the tapered fiber can interact with the MF under the external magnetic field to cause the birefringence variation of the fundamental mode, leading to the change in the free spectral range (FSR) of the interferometer, which can be mapped to the oscillation frequency shift of the OEO in the microwave domain. By the above converting, the magnetic field measurement with high interrogation speed and resolution can be realized. In addition, the designed device shows a certain measurement directionality of the magnetic field due to two orthogonally polarized fundamental modes asymmetric to the magnetic field, obtaining a good conformity with the constructed theoretical models. The experimental results show the maximum magnetic field sensitivities of 159.4 Hz/mT in the range of 8.48-27.83 mT, and 350.8 Hz/mT in the range of 0-5.14 mT, corresponding to the light wave vector parallel and perpendicular to the magnetic field, respectively.

Frequency Division Multiplexing Fiber Bragg Grating Sensing System Based on a Dual-Loop Optoelectronic Oscillator

Frequency Division Multiplexing Fiber Bragg Grating Sensing System Based on a Dual-Loop Optoelectronic Oscillator

Stability improvement of a dual-loop optoelectronic oscillator based on self-phase locking.

In this study, we experimentally demonstrate what we believe is a novel dual-loop optoelectronic oscillator (OEO) with a self-phase locking loop (SPLL). Using this feedback loop, the phase of the oscillating signal is locked to its past by adjusting the DC bias voltage of the used Mach-Zehnder modulator. In this way, the oscillating frequency stability can be improved. Proving experiments on a 10-GHz OEO are performed. The results show that more than 20 dB improvements in the phase noise at low offset frequencies are achieved, the frequency fluctuation is reduced to less than 4 kHz in an hour, and the corresponding Allan deviation is decreased by 1 order of magnitude owing to the SPLL. This frequency stabilization scheme without use of any external reference sources has a great prospect in an integrated OEO.

Rational number harmonic mode-locked dual-loop optoelectronic oscillator with low supermode noise and low intermodulation distortions

A rational number harmonic mode-locked dual-loop optoelectronic oscillator (RHML-DL-OEO) is proposed and experimentally demonstrated. In the proposed system, an external radio frequency (RF) signal and a feedback oscillating microwave signal drive two arms of a dual-drive Mach-Zehnder modulator (DMZM). Mode locking is realized by frequency detuning. The larger effective free spectrum range (FSR) and higher side-mode suppression result from the Vernier effect effectively suppress supermode noise and intermodulation distortions (IMDs). Experimental results demonstrate that the microwave frequency comb (MFC) signals with repetition frequencies of 901.8 kHz, 2.3046 MHz and 5.3106 MHz are generated by 9th-, 23rd- and 53rd-order rational number harmonic mode-locking, respectively. Compared with the rational number harmonic mode-locked optoelectronic oscillator based on single-loop structure, the supermode noise suppression ratios of the scheme we propose are improved by 30.5 dB, 27.6 dB and 20.3 dB, respectively. Furthermore, the performance of single sideband (SSB) phase noise is also investigated.

Highly Sensitive Fiber Bragg Grating Sensing System Based on a Dual-Loop Optoelectronic Oscillator With the Enhanced Vernier Effect

In this paper, a highly sensitive fiber Bragg grating (FBG) interrogation system based on a dual-loop optoelectronic oscillator (OEO) with the enhanced Vernier effect has been proposed and experimentally demonstrated. Light reflected from the FBG sensor is used as the optical source of the OEO. By introducing dispersion in the OEO loop, the sensor information encoded in the FBG wavelength can be interrogated by detecting the frequency of microwave signal generated by the OEO loop. The dispersive media in OEO has two paths, one path is formed with a roll of dispersion compensation fiber (DCF), and the other path is formed with a roll of single-mode fiber (SMF). By designing the length of two paths with slightly difference, the Vernier effect is generated in the OEO. Since the dispersion of the two paths is opposite, an enhanced Vernier effect can be realized, which can significantly enhance the sensitivity. The experimental results prove the possibility of applying the concept of enhanced Vernier effect to the OEO for temperature sensing. The sensitivity is about 0.926 kHz/°C and 0.0912 kHz/°C for a single-loop OEO with DCF and SMF, respectively. By employing the enhanced Vernier effect, the sensitivity can be improved to 141.13 kHz/°C, which is estimated about 152.4 and 1547.5 times higher than that of the two single loops, respectively. Furthermore, sensitivity can be further improved by using a dispersive link with larger dispersion.

High-Precision Magnetic Field Sensor Based on Fiber Bragg Grating and Dual-Loop Optoelectronic Oscillator

A novel fiber-optic magnetic field sensor with high interrogation speed and resolution by using an etched fiber Bragg grating (FBG) in conjunction with a dual-loop optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. A commercial FBG is firstly dipped into mixed hydrofluoric acid solution to remove the cladding layer and then is embedded with the magnetic fluid (MF) as a sensing element. The central wavelength reflected from the FBG is related to the overall time delay of the dual-loop OEO, which determines the oscillating frequency of the OEO. Therefore, the magnetic field can be estimated by measuring the oscillating frequency shift of OEO. The experimental results show that the oscillating frequency linearly increases with the increment of the magnetic field, achieving the sensitivity of 16.3 Hz/Oe with a R-square of 0.991 in the range of 5 mT–10 mT. In addition, the maximum error is within ±0.05 mT in the range of 7 mT–8 mT, which offers potentials in many fields where the high-precision magnetic field measurement is required.

Controlling birhythmicity in a new Dual Loop Optoelectronic Oscillator with an injection locked van der Pol oscillator

In the present literature, an attempt has been made to understand the birhythmic behaviour of a modified time delayed Dual Loop Optoelectronic Oscillator (DLOEO). To this end, an analytical solution of periodic oscillation is obtained using weakly nonlinear analysis. Two coexisting periodic oscillations are identified, considering shorter loop delay as a control parameter. Subsequently, to control the birhythmicity, a self-feedback mechanism is applied that incorporates the variable to be controlled and its canonical conjugate. Our study reveals that with proper control of the feedback strength, birhythmicity can be removed and monorhythmicity can be induced in the oscillator.

Enhanced performance of a reservoir computing system based on a dual-loop optoelectronic oscillator.

Time-delayed reservoir computing (RC) is a brain inspired paradigm for processing temporal information, with simplification in the network's architecture using virtual nodes embedded in a temporal delay line. In this work, a novel, to the best of our knowledge, RC system based on a dual-loop optoelectronic oscillator is proposed to enhance the prediction and classification. The hardware is compact and easy to implement, and only a section of fiber compared to the traditional optoelectronic oscillator reservoir is added to conform the dual-loop scheme. Compared with the traditional reservoir, a remarkable performance of the proposed RC system is demonstrated by simulation on three well-known tasks, namely the nonlinear auto regressive moving average (NARMA10) task, signal waveform recognized task, and handwritten numeral recognition. The parameter optimization in the NARMA10 task is presented with influenced factors. The novel RC system finally obtains a normalized mean square error at 0.0493±0.007 in NARMA10 task, 6.172×10-6 in signal waveform recognized task, and a word error rate at 9% in handwritten numeral recognition with suitable parameters.

High-gain narrowband radio frequency signal amplifier based on a dual-loop optoelectronic oscillator.

A novel photonic-assisted method for radio frequency (RF) signal amplification with high-gain and narrowband based on a dual-loop optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. In the proposed system, the low-power RF signal is injected into a dual-loop OEO which is below the threshold oscillation state. And the maximum gain is obtained when the frequency of the RF signal matches with the potential oscillation mode of the dual-loop OEO. The approach provides an average gain greater than 22 dB for the RF signal which matches with oscillation mode. After amplification, the signal-to-noise ratio (SNR) turns out to be 40 dB. Furthermore, the 3 dB bandwidth of the suggested system can be narrower than 1.2 kHz which can effectively remove the out-of-band noise and spurious effects. Meanwhile, the performance of sensitivity and phase noise are also investigated.

Simultaneous RF Self-Interference Cancellation, Local Oscillator Generation, Frequency up- and down-Conversion in an Integrated In-Band Full-Duplex 5G RF Transceiver Front-End

Wideband radio-frequency (RF) self-interference cancellation (SIC), local oscillator (LO) generation, frequency up-, and down-conversion are all crucial for an in-band full-duplex (IBFD) 5G RF transceiver front-end. In this paper, a microwave photonic approach enabled by only one optical dual-polarization IQ modulator (DP-IQMZM) is proposed to simultaneously realize wideband RF SIC, LO generation, frequency up- and down-conversion. Note that, the LO signal with high spectral purity and low phase noise is produced by a dual-loop optoelectronic oscillator (OEO) using a self-polarization stabilization structure, and the generated LO signal is applied for frequency up- and down-conversion. Besides, the optical single-sideband signal is produced at the output of this 5G RF transceiver for uplink transmission from the remote antenna unit (RAU) to the baseband unit (BBU), so the power fading induced by fiber dispersion could be completely suppressed. A proof-of-concept experiment is performed, and the LO signal with the central frequency of 10 GHz, the phase noise performance of −108.97 dBc/Hz at a frequency offset of 10 kHz is achieved. A 5 × 20 MHz Long Term Evolution (LTE) 16/64-ary quadrature amplitude modulation-orthogonal frequency division multiplexing (16/64QAM-OFDM) signal with the central frequency of 12.6 GHz is down-converted to 2.6 GHz. Meanwhile, the cancellation ratio of 30.22 dB and 26.26 dB could be achieved when the bandwidth of the self-interference signal is 150 MHz and 300 MHz, respectively. Moreover, a 3 × 20 MHz LTE 64QAM-OFDM signal with a central frequency of 2.6 GHz is up-converted to 12.6 GHz, and the electrical signal-to-noise ratio of the generated RF signal can achieve 31.34 dB. The measured error vector magnitude performance shows that the generated down- and up-converted signal both meet the 3^rd Generation Partnership Project (3GPP) requirements for 5G systems.

Supermode noise suppression with polarization-multiplexed dual-loop for active mode-locking optoelectronic oscillator.

The active mode-locking (AML) technique has been widely used in erbium-doped fiber lasers to generate picosecond pulse trains. Here we propose a novel active mode-locking dual-loop optoelectronic oscillator (AML-DL-OEO), which can generate microwave frequency comb (MFC) signals with adjustable comb spacings. Based on this scheme, the order of harmonic mode-locking is dramatically decreased for a certain AML driving frequency compared with a single-loop AML-OEO. Thus, the supermode noise caused by harmonic mode-locking can be efficiently suppressed. In addition, the sidemodes are well suppressed by the dual-loop architecture. An experiment is performed. MFC signals with different comb spacings are generated under fundamental or harmonic mode-locking states. AML-DL-OEO systems with different length differences between two loops are implemented to evaluate supermode noise suppression capability. The performance of the generated MFC signals is recorded and analyzed.

Frequency-domain analysis of dual-loop optoelectronic oscillators.

Optoelectronic oscillators (OEOs) are hybrid systems consisting of optical and radio-frequency (RF) parts that are used to produce ultralow phase noise RF oscillations. Dual-loop OEOs can overcome some problems incorporated with single-loop OEOs such as the mode-hopping phenomenon and the large spurious peaks in the phase noise. Therefore, they are usually considered the practical implementation of many OEOs. Here, a frequency-domain steady-state and phase noise analysis approach of these systems is presented, based on the conversion matrix approach. Compared with the existing time-domain analysis approaches, it requires much smaller run times. Compared with the other frequency-domain modeling approaches, such as the linear-time-invariant phase transmission models, it can take all noise-transferring phenomena between various sidebands and all amplitude-noise to phase-noise conversions and vice versa into account. Therefore, it can be regarded as a comprehensive analysis approach to dual-loop OEOs. The validity of the new approach is verified by comparing its results with those of the previously published formulations in the literature.

Sensitivity Enhancement for Fiber Bragg Grating Strain Sensing Based on Optoelectronic Oscillator With Vernier Effect

Based on a dual-loop optoelectronic oscillator (OEO) with Vernier effect, a scheme of fiber Bragg grating (FBG) interrogation system with an improved scale factor has been proposed and experimentally demonstrated. Functioning as the optical carrier of the OEO, the reflection signal of two cascaded FBGs is divided into two optical beams by using a wavelength division multiplexer (WDM). The two optical beams at different wavelengths travel along single mode fibers with different lengths. After combined together by another WDM, the two optical beams go through a section of dispersion compensation fiber (DCF). The oscillating frequency shift of the OEO is determined by the overall time delay, which is affected by the wavelength change of the sensing FBG. Thus, the wavelength change of the sensing FBG can be converted into the oscillating frequency shift of the OEO. Furthermore, due to the length difference between the two optical beams, an obvious Vernier effect has been generated in the frequency response of the OEO. By detecting the frequency shift of the envelope peak of the frequency response curve, the sensitivity of the sensing interrogation can be enhanced greatly. A proof-of-concept OEO-based FBG sensor for axial strain sensing experiment is performed. The experimental results show that the sensitivity is about 0.31 KHz/μϵ for a single-loop OEO. By employing Vernier effect, the sensitivity can be improved to -11 KHz/μϵ, which is 35 times higher than that of the single-loop OEO.

Low jitter microwave pulse train generation based on an optoelectronic oscillator.

We demonstrate an approach to ultra-short pulse train generation with a low time jitter based on pulse compression of a frequency comb generated by a dual-loop optoelectronic oscillator (OEO). The proposed dual-loop OEO consists of two feedback loops, with one having a long loop length and the other a short loop length. In the long loop, a phase modulator (PM) cascaded with a Mach-Zehnder modulator (MZM) are employed, and in the short loop, only the MZM is included. Due to the Vernier effect, the use of the dual-loop structure can facilitate mode selection to generate a single-frequency microwave carrier with multiple optical sidebands corresponding to an optical comb. By adjusting the phase relationship between the optical sidebands using a dispersion compensating fiber (DCF), a stable optical pulse train is generated. Thanks to the low phase noise nature of an OEO, the generated pulse train has a low time jitter. The proposed approach is evaluated experimentally. A pulse train with a repetition frequency of 2.023 GHz and a pulse width of 40 ps is generated. The single-sideband (SSB) phase noise of the carrier frequency generated by the OEO is measured to be -118 dBc/Hz at a 10-kHz offset frequency, corresponding to a time jitter of the pulse train of 391.2 fs. The phase noise can be further reduced if an active cavity stabilization mechanism is adopted, enabling further reduction in the time jitter to the order of tens of femtoseconds.