Growth dynamics of Bragg gratings in multimode optical fibre

The spectrum of a Bragg grating in a multimode optical fiber can be controlled by the number of irradiation pulses during the writing procedure. Hence, a single mode grating can be fabrication readily within a multimode fiber. The width of the stop band of the grating can also be controlled by means of the number of irradiation pulses. A tilted grating leads to the coupling of core mode to cladding mode, and when the tilt is sufficiently large, eventually to radiation mode. In the case of small tilt, the grating spectrum is the sum of the core-core mode spectrum and the core-cladding mode spectrum.     

Temperature and strain discrimination using a single tilted fibre Bragg grating

A fibre optic sensor capable of discriminating between temperature and strain, using a single fibre Bragg grating, is presented. The technique exploits the core-cladding mode coupling of a tilted fibre Bragg grating (TFBG). The core and cladding modes exhibit different thermal sensivities, while the strain sensivities are approximately equal. Monitoring the core-core mode coupling resonance and the core-cladding mode coupling resonance of the TFBG spectrum allows the separation of the temperature and strain induced wavelength shifts.     

Femtosecond mode-locked Yb fiber laser for single-mode fiber chirped pulse amplification system

High-peak-power laser systems are based on the chirped pulse amplification (CPA) technique. CPA laser system needs a mode-locked laser oscillator for stable ultrashort pulse laser generation. We report a single-mode fiber CPA system which consists of stable mode-locked Yb-doped fiber laser oscillator with a wide tuning range, chirped fiber Bragg grating stretcher, and two Yb-doped fiber amplifiers. The single-mode fibers can generate high-quality and single-mode beams which are stable for long time.     

Numerical Analysis of Highly Birefringent Photonic Crystal Fibers with Bragg Reflectors

We analyze theoretically the coupling properties of Bragg gratings written in highly birefringent photonic crystal fibers with doped core and show how they can be tuned by the parameters of a microstructured fiber. We apply the coupled mode theory combined with a fully vectorial mode solver based on the plane-wave method. The results indicate large differences in interaction with the grating for the two linearly polarized fundamental modes. We show fiber designs, which provide single-mode operation with high birefringence and at the same time a high coupling efficiency of the grating. Such features can be used in fiber sensors, fiber laser configurations or to introduce a polarization dependent feedback in a long external cavity system with a semiconductor laser.     

利用倾斜光纤光栅的可开关双波长光纤激光器

报导了一种在四波混频作用下利用倾斜光纤布拉格光栅进行波长选择的可开关双波长掺铒光纤激光器。通过将倾斜光纤光栅与单模光纤进行横向错位焊接,使光栅的反向LP01和LP11两个模式具有相近的有效反射率,从而可以用来进行激光器的双波长选择。接入腔内的一段高非线性光子晶体光纤引入的四波混频效应克服了模式竞争,使得双波长激光在室温下稳定振荡。腔内起偏器和偏振控制器的联合作用可产生依赖于波长的损耗,以补偿光纤光栅两反射峰峰值的大小差异。基于以上原理,通过调节腔内的偏振态,该激光器实现了室温下稳定的双波长输出,也实现了在两波长之间的转换。两波长激光均有超过45 dB的信噪比,最大的功率波动为0.8 dB     

Femtosecond laser direct writing of multiwavelength Bragg grating waveguides in glass

Novel Bragg grating waveguide structures have been fabricated in bulk borosilicate glass through a type II photosensitivity mechanism driven by single femtosecond laser pulses. Low-loss single-mode waveguides and narrow-linewidth Bragg gratings were generated simultaneously by forming an array of refractive index voxels in a single laser scan. Laser pulse duration is shown to significantly affect the grating strength and waveguide loss. Bragg wavelengths, defined by the periodicity of laser-modified volumes, were fully controlled by the sample scan speed to provide resonances anywhere in the 1200-1620 nm telecommunication bands. Four linear Bragg filters with distinct resonant wavelengths are presented that define the first demonstration of laser writing of multiple-wavelength and cascaded Bragg grating waveguides in a single process step.     

Fiber laser with combined feedback of core and cladding modes assisted by an intracavity long-period grating

We present a fiber laser made in a single piece of conventional doped-core fiber that operates by combined feedback of the fundamental core mode LP((0,1)) and the high-order cladding mode LP((0,10)). The laser is an all-fiber structure that uses two fiber Bragg gratings and a long-period grating to select the modes circulating in the cavity; the laser emits at the coupling wavelength between the core mode LP((0,1)) and the counterpropagating cladding mode LP((0,10)) in the Bragg gratings. This work demonstrates the feasibility of high-order mode fiber lasers assisted by long-period gratings.     

Externally-modulated high-power fiber grating ring laser for digital transmission

We have constructed a low-cost, double-cavity erbium-doped fiber ring laser with a fiber Bragg grating and a 2×2 coupler. A high output power of 8.7 dBm and a signal-to-noise-floor ratio of 43 dB were demonstrated. This fiber grating ring laser is used as the light source for the 2.488 Gb/s transmission experiment through a 100 km single mode fiber. To our knowledge, this is the first time a fiber grating ring laser is being used as an externally modulated source for digital transmission.     

Stable single frequency Er-doped all-fiber ring laser with fiber Bragg grating Fabry-Perot filter

Using a fiber Bragg grating (FBG) and a Fabry-Perot cavity composed of two fiber Bragg gratings (FBGFP) as its frequency-selective components, a type of single frequency all-fiber ring laser permits oscillation only on one longitudinal mode of the main cavity without modehopping while the cavity length can be up to tens of meters. The salient feature is due to the single narrowband resonance of the FBGFP filter. Such a fiber ring laser is achieved experimentally, and the laser mode is limited inside the single resonance of the FBGFP.     

多模光纤光栅温度传感特性的实验研究

利用氢敏化处理的多模光纤制作了多模光纤光栅,并对多模光纤光栅的温度传感特性进行了实验研究与理论分析,表明这种光栅三个反射峰的布拉格波长随温度变化均呈现出良好的线性关系,并且重复性相当好,同一光栅的各反射峰的理论温度灵敏度系数都等于0．01nm／℃,实验测得的温度灵敏度系数为0．0098nm／℃或0．0099nm／℃,与理论分析相当吻合,这些特性与单模光纤光栅的温度传感特性接近相同。因此可以用多模光纤光栅代替单模光纤光栅开发光纤光栅传感器,以降低成本;这一实验结果还可以作为对多模光纤光栅进一步深入研究的参考。     

电流调谐光纤光栅外腔分布布拉格反射激光器

报道一种新颖的波长可调谐光纤光栅外腔分布拉格反射激光器。把经过金属管封装的光纤面布拉格光栅作为激光二极管的外腔反射镜,得到的单模激光输出不仅线宽窄,边模抑制比高,而且,调节流过金属管的电流,可在5nm范围内的6个不同波长间转换。     

Effect of active fiber birefringence on polarization properties of DBR all-fiber laser

Laser Physics - The polarization properties of a distribute Bragg reflective (DBR) all-fiber laser configured with a common single mode high-reflectivity fiber Bragg grating (SM-FBG) and a...     

Passively mode-locked Raman fiber laser with 100 GHz repetition rate

We experimentally demonstrate the operation of a passively mode-locked Raman fiber ring laser with an ultrahigh repetition rate of 100 GHz and up to 430 mW of average output power. This laser constitutes a simple wavelength versatile pulsed optical source. Stable mode locking is based on dissipative four-wave mixing with a single fiber Bragg grating acting as the mode-locking element.     

Monochromatization of semiconductor laser diodes using one-dimensional photonic crystals

The results on the development of the single-frequency semiconductor laser with external cavity based on a fiber Bragg grating (one-dimensional photonic crystal) formed in a single-mode fiber waveguide are presented. Stable single-frequency lasing at a wavelength of 977 nm with a spectral half width of 0.2 nm is achieved with a laser power output of 350 mW. The temperature dependence of lasing parameters is studied.     

Rapid fabrication of microhole array structured optical fibers

A microhole array in a common single-mode fiber is fabricated by selective chemical etching of femtosecond-laser-induced fiber Bragg grating (FBG), which has a laser-modified region extending from the fiber core to the cladding-air boundary due to laser self-focusing. The shape and size of the orderly microhole on the fiber surface are controlled via changing conditions of FBG fabrication and chemical etching. A simultaneous sensing for surrounding refractive index and temperature is demonstrated by this microhole array FBG through measurement of the transmission power change and Bragg resonant wavelength shift.     

Fabrication of high-mechanical-resistance Bragg gratings in single-mode optical fibers with continuous-wave ultraviolet laser side exposure

The mechanical resistance of single-mode fibers containing fiber Bragg gratings inscribed with cw UV laser irradiation is almost identical to that of pristine fiber. The median breaking strength of the gratings' Weibull distribution is more than 5 GPa, and the m value is of the order of 70. Based on a dynamic fatigue model, a Bragg grating lifetime of 50 years with a failure probability of 0.001 is predicted, assuming a constant applied stress of 0.96 GPa.     

光纤光栅可调谐半导体单模超短光脉冲的研究

本文利用光纤光栅形成外腔反馈,得到量子阱半导体激光二极管单模超短光脉冲.其光谱线宽约为0.4nm,脉冲宽度约为60ps.并利用调谐装置,改变光纤光栅的反射波长,得到不同波长的超短光脉冲,其波长可长期稳定.     

Inscription and Visualization of Tilted Fiber Bragg Gratings

Tilted fiber Bragg gratings with different tilt angles have been inscribed in single-mode isotropic optical fiber with an increased photorefractivity using Talbot interferometer and KrF-excimer laser system. Their spectra are studied. Using a confocal laser scanning luminescent microscope the images of gratings in transmitted light were obtained. The calculated dependence of the slope angle of the grating recorded in the Talbot interferometer on the angle between the strokes of the interference pattern created in the interferometer and the transverse section of the optical fiber is experimentally verified.     

Fibonacci quasi-periodic superstructure fiber Bragg gratings

Superstructure fiber Bragg gratings constructed following the Fibonacci sequence are proposed and simulated by using the transfer matrix method. The reflection spectrum has a multi-fractal structure as a function of the wavelength and is symmetric to the center. The reflectivity has self-similarity and scaling with respect to the Fibonacci sequence order at the central wavelength. For the transmission spectrum, the interaction of the core-cladding mode is investigated and the particular wavelengths for which the resonance condition is satisfied are located by varying the grating parameters. The potential application of the quasi-periodic structure as fiber sensors is also proposed.