Critical dispersion of chirped fiber Bragg grating for eliminating time delay signature of distributed feedback laser chaos

Optical chaos has attracted widespread attention owing to its complex dynamic behaviors.However,the time delay signature(TDS)caused by the external cavity mode reduces the complexity of optical chaos.We propose and numerically demonstrate the critical dispersion of chirped fiber Bragg grating(CFBG)for eliminating the TDS of laser chaos in this work.The critical dispersion,as a function of relaxation frequency and bandwidth of the optical spectrum,is found through extensive dynamics simulations.It is shown that the TDS can be eliminated when the dispersion of CFBG is above this critical dispersion.In addition,the influence of dispersive feedback light and output light from a laser is investigated.These results provide important quantitative guidance for designing chaotic semiconductor lasers without TDS.

Code synchronization based on lumped time-delay compensation scheme with a linearly chirped fiber Bragg grating in all-optical analog-to-digital conversion

We propose a novel lumped time-delay compensation scheme for all-optical analog-to-digital conversion based on soliton self-frequency shift and optical interconnection techniques. A linearly chirped fiber Bragg grating is optimally designed and used to compensate for the entire time-delays of the quantized pulses precisely. Simulation results show that the compensated coding pulses are well synchronized with a time difference less than 3.3 ps, which can support a maximum sampling rate of 151.52 GSa/s. The proposed scheme can efficiently reduce the structure complexity and cost of all-optical analog-to-digital conversion compared to the previous schemes with multiple optical time-delay lines.

The Analysis and Research of Chirped Bragg Fiber GratingTheory on Dispersion Compensation

Based on the general theory of linear Chirped Bragg fiber grating, this paper discusses some parameters including different chirped values and quasi gauss coupling function relating with the reflectivity coefficient dispersion compensation.The result shows that selecting larger chirped value and appropriate qusi guass coupling function can improve the dispersion compensation while ensuring high reflectivity. The concept of "figure of merit" in the microwave field is introduced to quantize the equalizing power of the dispersion compensator.

Tunable Super-Structured Fiber Bragg Gratings with Perfect Sequences Based on m-Sequence

Recently, a tunable fiber Bragg grating(FBG) was developed by using stress-responsive colloidal crystals. In this paper, we have simulated the application of these nanoparticles into the super-structured fiber Bragg grating(SSFBG) written with perfect sequences derived from a short maximal-length sequence. A tunable SSFBG will be available to overcome the prohibitive temperature variation of the optical codecs. Nevertheless,we presented a method to implement coherent time spreading optical code-division multiple-access(OCDMA) where a unique code(or perfect sequence) can be reused and mixed with different wavelengths to obtain a tunable wavelength-division multiplexing(WDM)system. In order to maximize the binary throughput, we have selected a unique short maximal-length sequence composed of 7 chips that can be tuned with 7 different optical wavelengths. We found thousands of different tunable combinations that presented power contrast ratios(P/C) higher than 12 dB. When a WDM-OCDMA system used 2 different combinations simultaneously, the perfect binary detection with error correction codes was achieved successfully. The tunable SSFBG with colloidal crystals will be a simple and good alternative choice for fiber-to-the-home(FTTH) communications.

Strain Multipoint Measurements Based on Chirped Bragg Grating Sensors

In this paper,we propose the novel system of multipoint measurement.The sensors of measurements are chirped Bragg grating and the interrogation of sensors is sub-carrier phase.The wavelength division multiplexing technique is used for addressing a network of FBG sensors and the time-division multiplexing technique is used for multipoint measurements.In the system,the modulation frequency of 200 MHz is adopted.The range of dectetion is from 0 to 900μεand the resolution is 12με. The time of the sensor response is about 1ns.

Chirped Bragg光纤光栅的优化设计与优化指数

根据线性ChirpedBragg光纤光栅的一般原理 ,探讨了不同啁啾系数 ,准高斯耦合函数对Bragg反射光栅的反射率及色散补偿特性的响应。结果表明 :增大啁啾系数以及选取适当的准高斯耦合函数 ,在保证反射率较大的情况下 ,能有效地改善色散补偿特性。通过引入微波领域的“优化指数”这一概念 ,量化了色散补偿器的补偿能力。

任意布拉格波长Chirped光栅的写入

提出了一种波长写入范围达30 nm 的Chirped 光栅的构造方法,这种方法只需要一个会聚柱透镜、一个发散柱透镜和相位掩膜板,并且对光纤与相位掩膜板的距离与写入光栅的Bragg

Chirped Bragg 光纤光栅色散补偿研究

分析ＣｈｉｒｐｅｄＢｒａｇｇ光纤光栅的色散特性，并作一定性分析．利用耦合模方程导出ＣｈｉｒｐｅｄＢｒａｇｇ光纤光栅的反射率方程，从而推导出ＣｈｉｒｐｅｄＢｒａｇｇ光纤光栅的色散计算公式，并用数值分析画出它们的响应曲线．

平顶型CLPG-CFBG级联结构中温度应力传感特性的研究

为了使光纤光栅传感器在光纤传感系统的应用中同时具有温度应力双参量传感和通信传输的功能,提出了一种由啁啾长周期光纤光栅(CLPG)和啁啾光纤布喇格光栅(CFBG)组成的平顶型光纤光栅传感器结构。采用测量中心波长位移的方法,建立了传感器温度和应力灵敏度系数矩阵,进行了理论分析和仿真验证。结果表明,CLPG的温度和应力灵敏度大小分别为2660 pm/℃和132 pm/με;CFBG的温度和应力灵敏度大小分别为12.6 pm/℃和0.8 pm/με,且CLPG和CFBG同时都具有平顶输出光谱,平顶光谱带宽分别达到了13.8 nm和5.6 nm,该传感器可以实现温度应力双参量同时传感,具有稳定的通信传输波段。该研究为光纤光栅传感器在光纤传感系统中的应用提供了参考。

线性chirp光纤光栅色散补偿器的理论与计算

从物理上解释了线性ｃｈｉｒｐ光纤光栅色散补偿器的工作原理。根据耦合模理论，导出了光纤光栅的基本方程。利用这一方程，计算了线性ｃｈｉｒｐ光纤光栅的响应特性。

Chirp光纤光栅及其主要应用

本文扼要评述ｃｈｉｒｐ光纤光栅的光学特性，包括耦合波方程、反射谱和时延特性，对几种主要紫外写入ｃｈｉｒｐ光纤光栅的技术进行了全面的评价，最后介绍了ｃｈｉｒｐ光纤光栅在光通信和激光等方面的重要应用。

Vector bending sensor based on chirped long-period grating with off-axis micro-helix taper

Vector bending sensing has been consistently growing in many fields.A low-cost and high sensitivity vector bending sensor based on a chirped long-period fiber grating[LPFG]with an off-axis micro helix taper is proposed and experimentally demonstrated.The grating is composed of several sections of single-mode fiber with gradually larger lengths,and the off-axis micro helix tapers with fixed lengths when they are fabricated by using the arc discharge technology.The large refractive index modulation in the micro-helix taper greatly reduces the sensor size.The total length of the sensor is only 4.67 mm.The micro-helix taper-based LPFG can identify the bending direction due to the asymmetric structure introduced by the micro helix.The experimental results show that the transmission spectra of the sensor have distinct responses for different bending directions,and the maximum bending sensitivity is 14.08 nm/m^(-1)in the range from 0.128 m^(-1)to 1.28 m^(-1).The proposed bending sensor possesses pronounced advantages,such as high sensitivity,small size,low cost,and orientation identification,and offers a very promising method for bend measurement.

Fabrication of kW-level chirped and tilted fiber Bragg gratings and filtering of stimulated Raman scattering in high-power CW oscillators

Suppression of stimulated Raman scattering(SRS)by means of chirped and tilted fiber Bragg gratings(CTFBGs)has become a key topic.However,research on high-power systems is still lacking due to two problems.Firstly,after the inscription,there are a large number of hydroxyl compounds and hydrogen molecules in CTFBGs that cause significant heating due to their strong infrared absorption.Secondly,CTFBGs can couple Stokes light from the core to the cladding and the coating,which causes serious heating in the coating of the CTFBG.Aimed at overcoming these bottlenecks,a process that combines constant-low-temperature and variable-high-temperature annealing is used to reduce the thermal slope of the CTFBG.Also,a segmented-corrosion cladding power stripping technology is used on the CTFBG to remove the Stokes light which is coupled to the cladding,which solves the problem of overheating in the coating of the CTFBG.Thereby,a CTFBG with both a kilowatt-level power-carrying load and the ability to suppress SRS in a fiber laser has been developed.Further,we establish a kW-level CW oscillator to test the CTFBG.Experimental results demonstrate that the power-carrying load of the CTFBG is close to 1 kW,the thermal slope is lower than 0.015 ℃/W,and the SRS suppression ratio is nearly 23 dB.

Multi-wavelength fiber ring laser based on a chirped moiré fiber grating and a semiconductor optical amplifier

A simple and cost-effective multi-wavelength fiber ring laser based on a chirped Moire fiber grating （CMFG） and a semiconductor optical amplifier （SOA） is proposed. Stable triple-wavelength lasing oscillations at room temperature are experimentally demonstrated. The measured optical signal-to-noise ratio （SNR） reaches the highest value of 50 dB and the power fluctuation of each wavelength is less than 0.2 dB within a 1-h period. To serve as a wavelength selective element, the CMFG possesses excellent comb-like filtering characteristics including stable wavelength interval and ultra-narrow passband, and its fabrication method is easy and flexible. The lasing oscillation shows a narrower bandwidth than SOA-based multi-wavelength fiber lasers utilizing some other kinds of wavelength selective components. Methods to optimize the laser performance are also discussed.

Calculation of the Figure of Merit of Linearly Chirped Fiber Gratings for Dispersion Compensation

At first, we systematically sum up and deduce the figure of merit of the compensator using linearly chirped fiber gratings. Secondly, we solve the Reccatti differential equation by the Runge Kutta method and calculate the reflectivity and dispersion of the linearly chirped fiber gratings to obtain the figure of merit numericallu.On the other hand, we also discuss the figure of merit under the circumstances of three kinds of coupling coefficients and compare them Finally, we present one kind of perfect design of the compensator using the Gauss coupling function, and simply discuss the method to realize the Gauss coupling function in the fabrication of linearly chirped fiber gratings in this paper.

The generation of group delay ripple of chirped fiber gratings

The analysis of the group delay ripple (GDR) generated by chirped fiber gratings is developed based on the Fabry-Perot (F-P) resonator. It shows clearly how the GDR is generated and why the periods of GDR varies along the chirped fiber gratings. It could also explain why apodization could suppress the GDR and how apodization affects the chirp of the grating. The theory could be used to devise the apodization of fiber gratings.

Wavelength-swept fiber laser based on bidirectional used linear chirped fiber Bragg grating

A wavelength-swept fiber laser is proposed and successfully demonstrated based on a bidirectional used linear chirped fiber Bragg grating(LC-FBG). The wavelength-swept operation principle is based on intracavity pulse stretching and compression. The LC-FBG can introduce equivalent positive and negative dispersion simultaneously, which enables a perfect dispersion matching to obtain wide-bandwidth mode-locking. Experimental results demonstrate a wavelength-swept fiber laser that exhibits a sweep rate of about 5.4 MHz over a 2.1 nm range at a center wavelength of 1550 nm. It has the advantages of simple configuration and perfect dispersion matching in the laser cavity.

Grating-free 2.8μm Er:ZBLAN fiber chirped pulse amplifier

We report on a grating-free fiber chirped pulse amplifier(CPA)at 2.8μm for the first time.The CPA system adopted Er:ZBLAN fiber with large anomalous dispersion as the stretcher and germanium(Ge)rods as the compressor with a compact structure.High-energy picosecond pulses of 2.07μJ were generated at the repetition rate of 100 kHz.Using highly dispersive Ge rods,the amplified pulses were compressed to 408 fs with a pulse energy of 0.57μJ,resulting in a peak power of approximately 1.4 MW.A spectral broadening phenomenon in the main amplifier was observed,which was caused by the special gain shape of the Er:ZBLAN fiber amplifier in operation and confirmed by our numerical simulation.This compact fiber CPA system at 2.8μm will be practical and meaningful for application fields.

A novel tunable polarization mode dispersion compensator with strain chirped fiber Bragg gratings

A tunable polarization mode dispersion (PMD) compensator based on strain-ckirped fiber Bragg gratings (FBGs) is proposed. It natures in flexible designing, large tuning range, without using linear or nonlinear chirped phase mask, fast tuning response time, continuously adjustable, all-fiber based, compact, and cheap.

A new method for analyzing the characteristics of sampled chirped fiber grating

On the basis of the coherence theory a new method is presented to analyze the sampled chirped fiber gratings (SCFG). With this method, more results on the SCFG are obtained, including not only the characteristics of reflectivity, transmission and time delay, but also the simplified reflectivity formula, the channel's number, wavelength spacing and channel's bandwidth. Therefore, this method is more systematic and perfect than the usual transfer matrix method and can well guide the design of the SCFG.