Fiber Ring Resonator Research Articles

Electro-Optic Tuneable of Direct Current Voltage in Ring Resonator

In this paper, a new design of the electro-optical tuning voltage in buried fiber ring resonator (BFRR) system is proposed. The crystals of LiNbO3, (Ba, Sr)TiO3, K(Ta, Nb)O3 and KH2PO4 are used as electro-optic core materials. The applied voltage can generate different refractive index deformation when used different electro-optic crystals. Different electro-optic crystals produce distinct maximum power loss within BFRR. The power loss in an electro-optic crystal can be controlled by tuning the applied voltage. The K(Ta, Nb)O3 crystal produce maximum power loss with lower voltage compared to other crystals.

Basic prerequisites for limit-cycle oscillations within a synchronously pumped passive optical nonlinear fiber-ring resonator

By taking into account Kerr nonlinearity and negative second-order dispersion, we show by numerical investigations that in a passive optical nonlinear fiber ring resonator synchronously pumped with femtosecond pulses a temporal delay via a resonator length detuning or via third-order dispersion leads to limit cycle behavior, which is represented by an oscillatory evolution of the temporal as well as the spectral pulse shape. By introducing a two-dimensional iterative map, we show that limit cycles arise due to the mutual coupling of different spectral pulse components. The resulting system behavior can be used to introduce additional adjustable frequency components into frequency combs.

OPTICAL BISTABILITY IN A NONLINEAR SOA-BASED FIBER RING RESONATOR

A novel optical inverted bistable switch based on a nonlinear fiber ring resonator (FRR) containing a semiconductor optical amplifier (SOA) has been analyzed and experimentally demonstrated. Optical bistability is obtained due to the transmission characteristics of the resonator and the SOA's gain characteristics. A complete theoretical analysis and supporting simulations are presented. A prototype is demonstrated using commercial optical components. Experimental results show switching performance with falling times lower than 10 ns.

Phase-generated carrier demodulation scheme for fiber Fabry–Pérot interferometric sensor with high finesse

This paper presents a demodulation scheme using phase-generated carrier (PGC) for a fiber Fabry-Pérot interferometric (FFPI) sensor with high finesse. The FFPI is constructed by a polarization maintaining fiber ring resonator with dual-coupler (PMDC-FRR), which can eliminate the polarization induced fading phenomenon. Compared with the former phase demodulation methods, the PGC scheme in this paper does not assume a two-beam interferometric approximation for the Fabry-Pérot cavity, and can work at arbitrary value of finesse in theory. Two PMDC-FRRs with reflective coefficients of 0.5 and 0.9 are made in experiments for demodulation. Both the single-frequency and the wideband signals are successfully demodulated from the transmission intensities using the PGC demodulation scheme. The experimental results demonstrate that the PGC demodulation scheme is feasible for the FFPI sensor with high finesse. The effects of the reflective coefficient and the intensity loss to the finesse are also discussed.

Complex-number asymmetry parameters of the optical Fano effect in ring resonators

We studied the sharp asymmetric Fano line shape in fiber ring resonator systems and provided an explicit expression for asymmetry parameters using the physical parameters of the system. The fiber ring system was controllable and reconfigurable, allowing us to produce a variety of Fano line shapes in different configurations. Experimentally observed asymmetric spectral structures were fully reproduced using the complex-number asymmetry parameters, validating the approximations used to reduce the analytical expression for the line shape to the phenomenological Fano formula. The results may be useful in the design of on-chip application systems.

Enhancing the sensitivity of fiber Mach–Zehnder interferometers using slow and fast light

We demonstrate theoretically and experimentally that the sensitivity of a fiber Mach-Zehnder (M-Z) interferometer can be enhanced by coupling fiber ring resonators with it. The experimental results agree well with theoretical predications that combining slow light with fast light will further increase the sensitivity of a fiber M-Z interferometer.

Response characteristic analysis of polarization maintaining fiber ring resonator with dual-coupler for sensing application

A polarization maintaining fiber ring resonator with dual-coupler (PMDC-FRR) for sensing application is presented in this paper. Polarization maintaining directional fiber couplers and fiber loop are employed to eliminate the polarization fading in the fiber ring resonator. Three important characteristic parameters associated with the sensing application, which are the visibility of the output intensities, the free spectral range and the finesse, are discussed as functions of the coupler coefficients and the fiber loop length in detail. In addition, the critical drive voltage of the tunable laser to keep the output intensities stable is also analyzed, when the fiber ring resonator with dual-coupler is utilized as fiber sensor with phase modulation. A PMDC-FRR is designed practically in experiment with the power coupling coefficients of 0.5 and the loop length of 22 m. The experimental results provide sufficient arguments for the theoretical predicts. The theoretical and experimental analysis results will be useful to the sensing application of the PMDC-FRR.

Full investigation of the backscattering in resonator fiber optic gyro

Resonator Fiber optic gyro (RFOG) is a high accuracy inertial rotation sensor based on the Sagnac effect. The optical fiber ring resonator (OFRR) is the key rotation sensing element. The backscattering characteristics of the OFRR are fully investigated. The Rayleigh backscattering dominates the backscattering spectrum with the input power below the threshold. High carrier suppression is crucial to reduce this Rayleigh backscattering error. Being different from the intrinsic Rayleigh scattering of the fiber, the stimulated Brillouin scattering (SBS) in the OFRR should be avoided. This is because the finesse and the resonance notch depth of the OFRR decrease for the pump depletion through the SBS process. The shot noise limited sensitivity (SLS) of the RFOG is improved by increasing the input power. Through analysis, it is found that the threshold input power is improved after phase modulation. The SLS of the RFOG is analyzed at different modulation parameters and its relevant SBS threshold. Accordingly, the optimized modulation frequency and the corresponding maximum input power are all obtained. A simple method of testing the frequency shift in the SBS is also proposed. In this method, the central frequency of the laser source is locked to the resonance frequency of the OFRR in one direction. A steady SBS light is observed and its frequency shift is measured together.

Tunable Tm-doped fiber ring laser operating at 19 μm band using force-induced fiber grating as wavelength tuner

We report wavelength-tunable operation of a Tm-doped silica fiber laser by using a force-induced long-period fiber grating (LPFG) formed in a fiber ring resonator. The laser output wavelength is tuned by moving the transmission passband that is generated between adjacent resonance wavelengths due to the force-induced LPFG. By changing the grating period around 900 μm, we control the laser output wavelength between 1845 and 1930 nm.

Transient response of a resonator fiber optic gyro with triangular wave phase modulation

We present an in-depth analysis of the transient response of a resonator fiber optic gyro based on triangular wave phase modulation. Unusual effects have been observed in the process of tracking the resonant frequency of an optical fiber ring resonator (OFRR). There is a distortion phenomenon, unlike the ideally square wave or a pure DC output of the OFRR, but signal overshoot or undershoot occurs. A deep analysis of the influence of the nonideal square wave or pure DC output on gyro performance is fully developed for the first time, to the best of our knowledge. Further analysis shows that this is the transient response process after modulation by the triangular wave, and the process is related both to the parameters of the OFRR and the modulation frequency of the triangular wave. By sampling the steady-state signal of the distortion square wave, or by oversampling the distortion signal to get a number of data, and then accumulating and averaging these data to be demodulated, the distortion's effect can be considerably decreased.

Laser diode frequency stabilization with a fiber ring resonator

To improve the frequency stabilization of laser diode in the laser frequency scanned interferometric metrology, a modified method is proposed by using a fiber ring resonator. The theoretical analysis of this modified method is performed. Moreover, the Pound-Drever-Hall (PDH) technique is employed to obtain the frequency discrimination curve of a fiber ring resonator, whose finesse is 1260 and line-width is 270 kHz. The simulated results show that the curve has a steep slope near the resonant frequency, which proves the sensitivity of this system to the frequency deviation, so the modified method has great potential for the frequency stabilization of a laser diode.

Simultaneous observation of superluminal and slow light propagation in a nested fiber ring resonator

We observe both superluminal and slow light propagation simultaneously in a nested fiber ring resonator. The two outputs of the resonator exhibit different absorption characteristics that produce opposite dispersion performance. The transmission spectra of two outputs are demonstrated experimentally for a variety of coupler settings. In particular, the group delays of the resonator for various values of the coupling coefficients are demonstrated theoretically and experimentally. We also discuss potential applications of the resonator.

A Shot-Noise Limited Fiber Laser Source by Cascaded Passive Optical Filtering

We present a technique for suppressing relative intensity noise in a fiber laser, which uses two Pound-Drever-Hall feedback control loops to lock two optical fiber ring resonators in series. The resonators act as cascaded passive optical filters to remove high frequency intensity noise. We describe and discuss the control scheme for holding the cavities on resonance, and present the experimental result, demonstrating shot noise limited performance for intensity fluctuations above 2.5 MHz.

Sensitivity analysis of a fiber ring resonator based on an air-core photonic-bandgap fiber

The fiber ring resonator (FRR) is the core sensing element in a resonator fiber optic gyroscope (R-FOG), and its sensitivity determines the performance of the R-FOG. This paper presents an in-depth analysis of the sensitivity of the FRR which is made of an air-core photonic-bandgap fiber (PBF), in which the characteristics of the FRR using PBF are compared with that of an FRR using a conventional single mode fiber. When using PBF instead of conventional fiber, it is found that the resonance curve is changed, and the sensitivity of the FRR is decreased a little when a narrow spectral linewidth laser is used. However, the degree of the decrease in sensitivity is not big enough to deny the advantages of PBF in improving the performance of the R-FOG considering that PBF is much better than conventional fiber in reducing the drift. Also, the optimal parameters of the directional coupler for sensitivity are discussed. It is found that the optimal intensity coupling coefficient when using PBF is nearly two times larger than that when using conventional fiber, and the optimal coupler intensity loss when using PBF is smaller than that when using conventional fiber.

Dark soliton array generation using fiber loop and ring resonators

We propose a system that can be used to generate a dark soliton pulse array by using multidark soliton sources in the microring resonators and an optical multiplexer, where the different dark soliton center wavelengths can be generated. To verify the simulation results, the experimental setup was employed by using the Brillouin enhanced fiber laser in the fiber ring resonator (loop) system, where two different systems, called forward and backward schemes, were used to generate the dark soliton arrays. Three different center wavelengths of dark solitons were generated and seen to be in good agreement with the theoretical results.

Dependence of output power in modulated optical fiber ring resonator on nonlinear refractive index

Nonlinear dynamics in optical fiber ring resonators (OFRRs) can be applied to the estimation of the nonlinear refractive index of optical fibers. The output power of the OFRR becomes convergent, periodic, and chaotic with an increase in the input power. In this study, the dependence of the output power on the nonlinear refractive index is analyzed numerically. The critical input power at which the convergent state changes to the periodic state decreases smaller as the nonlinear refractive index increases. In addition, the maximum oscillation width of the output power decreases monotonically with the nonlinear refractive index. These dependences are sensitive to the parameters of the OFRR. The estimation of the nonlinear refractive index can be realized effectively using the maximum or minimum critical input power, and the maximum oscillation width of the output power even under a subtle fluctuation in the optical fiber ring length.

Microwave photonic filter based on circulating a cladding mode in a fiber ring resonator

We propose a microwave photonic filter based on circulating a cladding mode in a fiber ring resonator, where the cladding mode is injected into and extracted from the resonator with a pair of matching long-period fiber gratings (LPFGs). The filter has a compact configuration and allows the frequency spacing and the notch depth to be tuned easily. The use of LPFGs also provides the capability of wavelength selection and tuning. Using a standard single-mode fiber and a pair of CO(2) laser-written LPFGs, we demonstrate a filter with a frequency spacing of approximately 1.3 GHz and a notch depth of approximately 17 dB. Our experimental results agree well with theoretical calculations.

Theoretical analysis of Sagnac loop mirror with an inline high birefringence fiber ring resonator: Application in single-frequency fiber lasers

Abstract We newly propose and theoretically analyze a Sagnac loop mirror with an inline ring resonator containing a piece of high birefringence fiber (HBF) and erbium-doped fiber (EDF). With the EDF properly pumped to offset the passive loss in the inline ring resonator, narrowband transmission peaks with large effective free spectral range can be realized by the intrinsic vernier effect between orthogonally polarized lights traveling along the two primary axes in the HBF. In addition, this property is independent of polarization states of the input signal, which makes the proposed Sagnac loop mirror suitable for a narrowband filter applied to single-frequency fiber lasers.

Electronic Feedback System for Stabilization of Fiber Ring Resonator

We propose a simple technique to stabilize the optical output intensity of a fiber ring resonator. The electronic feedback circuit system, which consists of two voltage control oscillators, a phase comparator, and a low pass filter, is applied to the fiber ring resonator in order to compensate the optical phase shift in the ring loop. The reference electrical signal determines the operating condition of the fiber ring resonator for the desired optical output signal. The experimental results within the operating range agree well with the analytical results. The simulated performance of the proposed model is also compared with that of other existing models and shows significant improvement over them.

Observation of the Phase Shift and Group Delay in Nested Optical Fiber Ring Resonator

We theoretically and experimentally demonstrate the transmission characteristics and time delay performance in a nested fiber ring resonator. The nested ring resonator is composed with a U-shaped fiber loop and a fiber ring nested together. With proper design of the coupling coefficient between the ring and the loop, the device is capable of generating a doubleFano spectral response. And the maximal group delay that it can be introduced depends on the value of the coupling coefficient. In this paper we measure the transmission properties of our nested fiber ring resonators with different coupling coefficients, using a Mach-Zehnder fiber interferometer. By inserting the nested fiber ring resonator into one arm of the fiber Mach-Zehnder interferometer we are able to optically measure the intensity transmission factor and the phase shift produced by the coupled resonators as a function of the optical frequency. The group delay can be deduced from this information. This theoretical and experimental demonstration shows the potential of nested ring resonators for dispersion tailoring and slow-light applications.