Fiber Bragg Grating Fabry-Perot Cavity Research Articles

Watt-level long-term stable ultra-narrow linewidth 1064 nm single-longitudinal-mode ring cavity fiber oscillator

This study presents a high-power, single-longitudinal-mode (SLM) fiber oscillator with a ring cavity design, operating at 1064 nm. Utilizing a double-cladding ytterbium-doped fiber as the gain medium, the system incorporates a fiber Bragg grating Fabry-Perot cavity and a dual coupler ring for step-by-step filtering to achieve SLM operation. With a pump power of 4.19 W, the oscillator delivered an output power of 1.01 W and narrowed the linewidth to 147 Hz, with the potential for further power increase. The oscillator demonstrated excellent longitudinal-mode stability, maintaining mode-hop-free operation for 8.7 hours after temperature stabilization. To the best of our knowledge, this work represents the longest duration of mode-hop-free operation and the narrowest laser linewidth achieved by a free-running ring-cavity SLM fiber oscillator at watt-level output powers.

Sensitivity Enhancement for Magnetic Field Sensor Using an Optoelectronic Oscillator Based on Fiber Bragg Grating Fabry-Perot Cavity With Acrylate Adhesive

Sensitivity Enhancement for Magnetic Field Sensor Using an Optoelectronic Oscillator Based on Fiber Bragg Grating Fabry-Perot Cavity With Acrylate Adhesive

Tunable and Switchable Dual-Wavelength SLM Narrow-Linewidth Fiber Laser with a PMFBG-FP Filter Cascaded by Multi-Ring Cavity

A single longitudinal mode (SLM) dual-wavelength switchable erbium-doped fiber laser (DW-EDFL) based on polarization-maintaining fiber Bragg grating Fabry–Perot cavity (PMFBG-FP) cascaded multiple sub-ring cavities (MSCs) is proposed. A PMFBG-FP with a narrow-band transmission peak and MSCs was implemented as an optical filter to achieve stable dual-wavelength laser output and guaranteed SLM status. By stretching the PMFBG, a highly stable dual-wavelength tunable output could be achieved with a maximum tuning interval of 0.17 nm. The optical signal-to-noise-ratio (OSNR) at dual-wavelength lasing was higher than 57 dB, and the optimal wavelength and power fluctuations within 0.5 h were 0.01 nm and 0.79 dB, respectively. Meanwhile, the measured linewidths of each wavelength were 1.55 kHz and 1.65 kHz, respectively. The measured polarization states of the two laser wavelengths were linear and orthogonal, with a degree of polarization (DOP) of nearly 100%.

Resonant fiber-optic thermometry with high resolution and wide range.

We report a high-resolution and wide-range thermometer using a fiber Bragg grating Fabry-Perot cavity (FBG-FP) combined with beat frequency interrogation. Two distributed feedback (DFB) lasers are locked to the FBG-FP sensing head and a hydrogen cyanide H13C14N (HCN) gas cell, respectively, both using the Pound-Drever-Hall (PDH) technique. The light beams from two lasers are brought together to interfere on a photodetector producing a beat frequency signal which provides a measure of the temperature change. Our sensor exhibits a dynamic range of ∼109 °C, a high resolution of 2×10-4 °C with an averaging time of 1 s. By introducing the reference frequency, the sensor has demonstrated good long-term stability. This sensor provides a useful tool for those fields where resolving slight temperature changes is crucial, such as deep ocean temperature measurement.

Curvature and temperature sensing based on a dual-frequency OEO using cascaded TCFBG-FP and SMFBG-FP cavities

A dual-frequency optoelectronic oscillator (OEO) incorporating cascaded fiber-Bragg-grating Fabry–Perot (FBG-FP) cavities designed for both curvature and temperature sensing is proposed and experimentally validated. The OEO is composed of two tunable laser diodes (TLDs), a phase modulator (PM), two FBG-FP cavities, a spool of fiber, a photodiode (PD) and an electrical amplifier (EA). One FBG-FP cavity is curved on a twin-core fiber (TCF) and the other is curved on a single mode fiber (SMF), with one core of the TCF aligned and spliced with the core of the SMF. The oscillating frequencies of the OEO are determined by the wavelength differences of the TLDs and the notches of the FBG-FP cavities. The oscillating frequency related to the twin-core-fiber-Bragg-grating Fabry–Perot cavity is both curvature and temperature sensitive thanks to the off-set core of the TCF, while the oscillating frequency corresponding to the single-mode-fiber-Bragg-grating Fabry–Perot cavity is only temperature sensitive. By monitoring the oscillating frequencies of the OEO, high-sensitivity curvature and temperature sensing are realized. The oscillating frequencies are linearly proportional to the curvature and temperature, with sensitivities as high as −1.19 GHz/m−1 and 1.14 GHz/oC, respectively.

Influence of intra-cavity loss on transmission characteristics of fiber Bragg grating Fabry–Perot cavity**Project supported by the National Natural Science Foundation of China (Grant Nos. 61405212, 61377062, 61405218, and 61775225) and Scientific Innovation Fund of Chinese Academy of Sciences (Grant No. CXJJ-17S010).

A theoretical model of the fiber Bragg grating Fabry–Perot (FBG-FP) transmission spectrum considering loss of FBG and intra-cavity fiber is presented. Several types of FBG-FPs are inscribed experimentally, and their spectra are measured. The results confirm that weak intra-cavity loss is enhanced at the resonance transmission peak, that is, loss of transmission peaks is observably larger than other wavelengths. For FBG-FPs with multi resonance peaks, when the resonance peak wavelength is closer to the Bragg wavelength, the more significant loss effect of resonance transmission peak is exhibited. The measured spectra are fitted with the presented theoretical model. The fitted coefficient of determinations are near 1, which proves the validity of the theoretical model. This study can be applied to measure FBG loss more accurately, without a reference light. It can play an important role in FBG and FBG-FP writing process optimization and application parameter optimization.

High resolution inclinometer based on vertical pendulum and fiber Bragg grating Fabry–Perot cavity

In this paper, an inclinometer based on a vertical pendulum and a fiber Bragg grating Fabry–Perot cavity (FBG-FP) is proposed. A low-damping rotation structure is used to reduce the mechanical frictions of the pendulum system and induce a wavelength shift of FBG-FPs. We find that the sensitivity can be maximized by optimizing the parameters of the inclinometer. Using a high-resolution demodulation system, a sensitivity of 179.9 pm/(°), and a resolution better than 0.02″ can be achieved. Experiments also show that the proposed inclinometer has good linearity and repeatability.

基于Terfenol-D材料和光纤光栅法布里珀罗腔的磁场传感器

基于Terfenol-D材料和光纤光栅法布里珀罗腔的磁场传感器

Subkilohertz linewidth reduction of a DFB diode laser using self-injection locking with a fiber Bragg grating Fabry-Perot cavity.

A simple and low-cost 1550 nm semiconductor laser with subkilohertz intrinsic linewidth is experimentally demonstrated. A commercial distributed feedback diode laser is self-injection locked to the resonance transmission peaks of a fiber Bragg grating Fabry-Perot cavity through a polarization-maintaining fiber ring with the optical path length of 4 m, with the laser frequency noise suppressed by over 70 dB in the Fourier frequency band from 5 Hz and 1 kHz. The laser features an intrinsic Lorentzian linewidth of 125 Hz as well as a relative intensity noise of <-142 dBc/Hz above 2 MHz, and provides over 0.8 nm quasi-continuous tunability, which is suitable for advanced applications requiring a narrow linewidth laser with ultralow frequency noise.

A switchable dual-wavelength fiber laser based on asymmetric fiber Bragg grating Fabry–Perot cavity with a SESAM

A switchable dual-wavelength fiber laser with an asymmetric fiber Bragg grating (FBG)–Fabry–Perot (FP) cavity based a semiconductor saturable absorber mirror (SESAM) is proposed and experimentally demonstrated. The proof of concept device consists of a FGB laser with an asymmetric FBG-FP cavity, a SESAM as mode loss modulator, and a intracavity FBG as wavelength selector by changing its operation temperature. The results demonstrate the new concept of dual-wavelength fiber laser based SESAM with asymmetric FBG-FP cavity and the technical feasibility.

Design of fiber magnetic field sensor based on fiber Bragg grating Fabry-Perot cavity ring-down spectroscopy

A novel fiber magnetic sensor based on the fiber Bragg grating Fabry-Perot (FBG-FP) cavity ring-down technique with pulse laser injection is proposed and demonstrated theoretically. A general expression of the intensity of the output electric field is derived, and the effect of the external magnetic field on the ring-down time is discussed. The results show that the output light intensity and the ring-down time of the FBG-FP cavity are in the inverse proportion to the magnitude of the external magnetic field. Our results demonstrate the new concept of the fiber magnetic sensor with the FBG-FP cavity ring-down spectroscopy and the technical feasibility.

Dual-wavelength erbium-doped fiber laser with asymmetric fiber Bragg grating Fabry-Perot cavity

A novel dual-wavelength fiber laser with asymmetric fiber Bragg grating (FBG) Fabry-Perot (FP) cavity is proposed and experimentally demonstrated. A couple of uniform FBGs are used as the cavity mirrors, and the third FBG is used as intracavity wavelength selector by changing its operation temperature. Experimental results show that by adjusting the operation temperature of the intracavity wavelength selector, a tunable dual-wavelength laser emission can be achieved. The results demonstrate the new concept of dual-wavelength lasing with asymmetric FBG FP resonator and its technical feasibility.

双波长相移光纤光栅的光谱特性及传感应用

The theoretical model of a dual wavelength phase-shifted fiber Bragg grating was established and its spectral characteristics were obtained by numerical simulations,which pointed that the transmission peaks spacing was affected by the amount of phase shift,refractive index modulation and grating length.The expression of transmission peaks spacing was acquired by resonance phase conditions of fiber bragg grating Fabry-Perot cavity,and the curves obtained by numerical simulation method accord well with the curves obtained by analytic formula,proves the correctness of the numerical simulation results.Finally,a sensing method based on transmission peaks spacing of a dual wavelength phase-shifted fiber Bragg grating was proposed,the temperature sensing characteristics were analyzed,and the theoretical sensitivity was about 60pm/℃.

Filter properties of chirped fiber Bragg grating Fabry–Perot cavity: a potential wavelength stabilizer of diode laser

We investigate filter properties of chirped fiber Bragg grating (CFBG) (Fabry-Perot) F-P cavity through analyzing the coupled wave equation from one-dimensional Helmholtz equation. We derive an approximate formula of the reflectivity of a CFBG F-P cavity, simulate the central wavelength detuning, and calculate the central wavelength shift with the increase of ambient temperature. In the experiments, we measured the spectra of a diode laser with an FBG/CFBG F-P cavity at 0°C-110°C. The experimental results show that the CFBG F-P cavity can help a diode laser to obtain a less central wavelength shift and a narrower 3dB reflection bandwidth, compared with the FBG F-P cavity at 0°C-110°C. The research results indicate that the CFBG F-P cavity is a potential wavelength stabilizer of uncooled diode laser.

光纤布拉格光栅法布里珀罗腔时延和色散特性的研究

光纤布拉格光栅法布里珀罗腔时延和色散特性的研究

High-Resolution Strain/Temperature Sensing System Based on a High-Finesse Fiber Cavity and Time-Domain Wavelength Demodulation

A high-resolution strain/temperature sensing system based on a fiber Bragg grating-Fabry-Perot cavity (FBG-FPC) and a wavelength-swept single-longitudinal-mode laser diode (modulated by a sawtooth signal) is proposed. The high-finesse (~627) FBG-FPC formed by two uniform FBGs of high reflectivity (~99.5%) is used both as a strain/temperature sensor and a FPC with ultranarrow (~0.12 pm) transmission bands. Using a photodetector to detect the transmissive light of the laser diode through the FBG-FPC, wavelength demodulation is achieved by mapping wavelength measurement to time measurement. Both strain sensing and temperature sensing with a resolution of 0.11 muepsiv and 0.014degC, respectively, have been demonstrated.

Theoretical and experimental investigation of the mode-spacing of fiber Bragg grating Fabry-Perot cavity

The mode-spacing of the fiber Bragg grating Fabry-Perot (FBG F-P) cavity is calculated by using the effective cavity length which contains the effective length of the FBG. The expression of the effective length, defined by using the phase-time delay, is obtained and simplified as a function of the peak reflectivity at the Bragg wavelength, the band edges, and the first zero-reffectivity wavelength. The effective length is discussed from the energy penetration depth point of view. Three FBG F-P cavities are fabricated in order to validate the effective length approach. The experimental data fits well with the theoretical predictions. The limitation of this method is also pointed out and the improved approach is proposed.

High efficient and narrow linewidth fiber laser based on fiber grating Fabry-Perot cavity

A high Er3+-doped narrow linewidth fiber laser based on fiber Bragg grating Fabry-Perot cavity was demonstrated. The spatial hole burning effect was restrained by a fiber Faraday rotator. Two short fiber Bragg grating Fabry-Perot cavities as narrow bandwidth filters discriminated and selected laser longitudinal modes efficiently. A stable single-frequency 1534.83 nm laser was acquired. Pumped by two 976 nm laser diodes and two-ended output, the fiber laser exhibited a 12 mW threshold. Total 39.5 mW output power and one end 22 mW output power were obtained at the maximum 145 mW pump power. Optical-optical efficiency was 27% and slope efficiency was 29.7%. The output power seemed to be saturated when pump power increased. The 3 dB linewidth of the laser was less than 7.5 kHz, measured by the delayed self-heterodyne method with 15 km monomode fiber. The high power narrow linewidth fiber laser can be used in high resolution fiber sensor systems.

Phase-modified coupled mode theory for calculation of fiber Bragg grating Fabry-Perot cavity transmission spectrum

Based on the influence of reflection phase of fibre Bragg grating on the transmission spectrum of fibre Bragg grating(FBG) Fabry-Perot cavity, the reason for the error of traditional coupled mode theory when calculating the reflection phase of uniform FBG is analyzed. A parameter of initial phase of effective index distribution is introduced to describe the slight offset of the index distribution of FBG in the longitudinal direction, and the real reflection and transmission coefficients are substituted for the simplified coefficients to modify the traditional coupled mode theory by introducing a phase factor, which is related with the initial phase of effective index distribution and independent of wavelength. The phase of transfer matrix method for nonuniform FBG is further modified. The modified fast calculation results are used to calculate the transmission spectrum of FBG F-P cavity and show the influence of initial phase of effective index distribution on the wavelength offset of FBG Fabry-Perot cavity transmission peaks. The results agree with those of Rouard method and experimental values.