Tunable dispersion device based on a tapered fiber Bragg grating and nonuniform magnetic fields

We present a new variable dispersion device based on tuning the chirp of a tapered fiber Bragg grating by means of a magnetic transducer. By using a nonuniform magnetic field, we demonstrate a 188-472-ps/nm dispersion tuning range, suitable for tunable radio-frequency filters and dispersion compensation, among others.     

Wavelength tuning of fiber Bragg gratings over 90 nm using a simple tuning package

We demonstrate a silica-based tunable fiber Bragg grating filter with a wavelength tuning range over 90 nm. A bend-tuning technique in a simple tuning package is employed to obtain a wide wavelength tuning range from 1634 to 1544 nm, covering the entire L-band and a half of the C-band. The polarization-mode dispersion and polarization-dependent loss of the device show little variations over the whole operating region.     

A tunable four-channel fiber Bragg grating dispersion compensator

A tunable four-channel dispersion compensator is achieved using fiber Bragg grating technology and applying a temperature gradient along the grating. Any dispersion from -370 to -1420 ps/nm could be obtained.     

宽带可调谐光纤光栅色散补偿器系统设计

文章提出一种在光纤光栅自身热膨胀效应产生啁啾的基础上,利用铝片热膨胀系数比较高的特点产生应力来增强光纤光栅啁啾,从而实现了宽带、大范围色散调谐的新型光纤光栅色散补偿器。该色散补偿器能够分别对群速度色散及中心波长独立调谐。实验结果表明,在中心波长为1 551.25nm处,能够实现>1.5nm的色散补偿带宽,-350～-690ps/nm的群时延色散调谐范围;在色散为-660ps/nm情况下,能够实现中心波长1nm的偏移。     

一种可调谐掺铒光纤激光器的研究

文章基于掺铒光纤在1 550 nm波段的增益特性,利用光纤光栅作为调谐装置,设计了可调谐光纤光栅激光器的简单结构,通过改变光纤光栅的温度对光纤激光嚣的波长进行了调谐.更重要的是实验分析了不同掺铒光纤长度对激光输出功率的影响,在温度为25℃时,实验中分别取10、20和30 m 3种不同光纤长度进行了测试,结果表明,不同长度的掺铒光纤,其阀值不同.     

基于非线性啁啾光栅和波长扫描的ROF系统

为了降低光信号在不同传输距离产生的色散对光载射频(ROF)(光载无线电)传输系统的信号质量的影响,提出了一种基于静态非线性啁啾光纤光栅(NLCFBG)和动态波长扫描相结合的可调谐色散补偿ROF传输系统方案。在对所提出系统方案进行理论分析的基础上制作了NLCFBG,并对ROF传输中的可调谐色散效果进行半实物仿真,分析和比较了有无光栅色散补偿时系统的传输性能;验证了此方案对不同传输距离、不同激光频率以及不同射频载波频率的光纤传输系统色散补偿性能。     

Adjustable compensation of polarization mode dispersion using ahigh-birefringence nonlinearly chirped fiber Bragg grating

We demonstrate an adjustable polarization-mode-dispersion (PMD) compensator. The device uses a nonlinearly chirped fiber Bragg grating written into a high-birefringence photosensitive fiber. By mechanically stretching the grating, the device generates a time delay between different polarizations that is adjustable from 100 to 320 ps and is tunable over 2.3 nm. We demonstrate tunable PMD compensation of a 10-Gb/s signal that has an initial delay between the two polarization states of 127 or 302 ps     

可调谐全正色散掺镱光纤激光器

利用相位长周期光纤光栅作为光谱滤波器,熔接于全正色散掺镱光纤激光系统中,从而实现了具有波长可调谐的连续激光输出和被动锁模激光脉冲输出,可调谐激光波长范围分别为11.4 nm和10.5 nm.通过调节偏振片改变激光腔内的偏振状态,输出锁模脉冲实现脉冲宽度的可调谐,其调谐范围为3.6~1.2 ns.在530 mW的最大泵浦功率下,得到了重复频率为2.5 MHz、最大单脉冲能量为38.9 nJ的锁模脉冲输出和最大输出功率为124 mW的连续激光输出.     

Twin fiber grating tunable dispersion compensator

A new tunable dispersion compensator that does not suffer from higher order dispersion is reported. The device consists of two quadratically chirped fiber Bragg gratings, each with linear strain actuators. The module has a tuning range of 500 ps/nm and a bandwidth of 0.5 nm. In a 40-Gb/s return-to-zero system, the dispersion penalty tolerance is extended from 100 to 600 ps/mm     

Nonlinearly strain-chirped fiber Bragg grating with an adjustabledispersion slope

In this letter, we demonstrate an adjustable dispersion slope compensator for waveform distortion compensation based on a nonlinearly strain-chirped fiber Bragg grating. The dispersion slope of the device can be tuned up to -18.9 ps/nm² with a bandwidth >2.4 nm. After transmission through a 120-km-long dispersion-shifted fiber, the resulting waveform distortion for a 2.65-ps pulse is successfully compensated by using this device     

Tunable fiber Bragg grating filters realized by chirp rate tuning with a cantilever beam

An efficient scheme to change the chirp rate of a fiber Bragg grating (FBG) has been developed based on a specially-designed cantilever beam with the beam-bending method. It allows, to date, the largest tuning range of 36 nm in reflection bandwidth of a chirped-FBG (CFBG) while keeping the center wavelength nearly fixed during the tuning process. Using this method, bandwidth-tunable fiber grating filters with tunable chromatic dispersion or differential group delay have been demonstrated. Channel spacing-tunable multi-wavelength filters based on both sampled- and superimposed-CFBGs have also been realized. Moreover, tuning of the bandwidth and channel spacing is continuous with this scheme that makes the achieved devices more flexible.     

Optimized All-Fiber Supercontinuum Source at 1.3 μm Generated in a Stepwise Dispersion-Decreasing-Fiber Arrangement

In this paper, the generation of a continuous-wave (CW)-pumped supercontinuum (SC) source at 1.3 mum is described. The device makes use of a tunable Yb-doped fiber laser, a cascade of fiber Bragg grating mirrors, and a concatenation of standard silica fibers with stepwise decreasing dispersion. It is shown that the dispersion-decreasing-fiber set enhances the width of the generated SC, since it favors the fission of the CW input into high-order solitons. The generated SC spans from 1280 to 1513 nm, shows an average output power of 1.34 W, and exhibits >0-dBm/nm spectral density of over 200 nm.     

Dynamic post dispersion optimization at 40 Gb/s using a tunablefiber Bragg grating

A compact tunable fiber Bragg grating that uses distributed thin-film heaters on the surface of the fiber is used to dynamically optimize the post dispersion compensation of a multi-span 40-Gb/s nonreturn-to-zero (NRZ) transmission system. Dynamic post dispersion compensation with this device enables the system to operate over a much wider range of launch power than is otherwise possible with simple, fixed compensation using dispersion compensating fiber     

Tunable wavelength filter using a Bragg grating fiber thinned byplasma etching

We studied a tunable wavelength filter using a single-mode fiber Bragg grating with a cladding thinned by reactive plasma etching. Reflection wavelength shifts were demonstrated by controlling the effective refractive index or the period of the grating. When liquid paraffin was used for additional cladding on a thinned grating fiber of 19-μm diameter, the shift rate of 0.055 nm/°C was obtained. In the case of applying the tension to the grating region, the shift rate was 3.4 nm/100 V for the fiber of 41-μm diameter     

Optimization of apodized linearly chirped fiber gratings foroptical communications

The dispersion characteristics of apodized, linearly chirped fiber Bragg gratings and their potential as dispersion compensators have been studied systematically. It is shown that the positive hyperbolic-tangent profile results in an overall superior performance, as it provides highly linearized time-delay characteristics with minimum reduction in the linear dispersion. To compensate for the linear dispersion of 100 km of standard telecom fiber over certain bandwidth (in nanometers), the required grating length is 19.24 cm/nm     

Electrically tunable efficient broad-band fiber filter

We demonstrate a new type of fiber-optic electrically tunable filter that enables a tuning range of 60 mm with an electrical power of 0.17 W, corresponding to a tuning efficiency of approximately 320 nm/W. The device is based on a metal coated long-period fiber grating written in a specially designed “air-clad” fiber that is filled with a polymer whose index of refraction is a sensitive function of temperature. Resistive heating, caused by current flowing through the metal coating, heats the polymer and induces changes in its index of refraction; these changes induce shifts in the position of the attenuation dip associated with the long-period grating. The air-clad structure has two benefits: (1) it enables the introduction of temperature sensitive materials into the fiber thus enabling power efficient operation of the device and (2) ensures that the cladding modes are insensitive to the surrounding environment and thus are unaffected by the metal coating on the surface of the fiber     

Integrated tunable fiber gratings for dispersion management in high-bit rate systems

Dispersion management is becoming paramount in high-speed wavelength-division-multiplexed lightwave systems, that operate at per-channel rates of 40 Gb/s and higher. The dispersion tolerances, in these systems, are small enough that sources of dispersion variation, that are negligible in slower systems, become critically important to network performance. At these high-bit rates, active dispersion compensation modules may be required to respond dynamically to changes occurring in the network, such as variations in the per-channel power, reconfigurations of the channel's path that are caused by add-drop operations, and environmental changes, such as changes in ambient temperature. We present a comprehensive discussion of an emerging tunable dispersion compensating device, based on thermally actuated fiber gratings. These per-channel devices rely on a distributed on-fiber thin film heater, deposited onto the outer surface of a fiber Bragg grating. Current flowing through the thin film generates resistive heating at rates that are governed by the thickness profile of the metal film. A chirp in the grating is obtained by using a thin-film, whose thickness varies with position along the length of the grating in a prescribed manner; the chirp rate is adjusted by varying the applied current. The paper reviews some of the basic characteristics of these devices and their implementation, in a range of different applications, including the mitigation of power penalties associated with optical power variations. We present detailed analysis of the impact of group-delay ripple and polarization-mode dispersion on systems performance, and present results from systems experiments, that demonstrate the performance of these devices at bit rates of 10, 20, 40 and 160 Gb/s. We also discuss advantages and disadvantages of this technology, and compare to other devices.     

Recompression of pulses broadened by transmission through 10 km ofnon-dispersion-shifted fiber at 1.55 μm using 40-mm-long opticalfiber Bragg gratings with tunable chirp and central wavelength

A 40-mm-long fiber Bragg grating with both tunable chirp and central wavelength is used to recompress pulses broadened by transmission through 10.0 km of non-dispersion-shifted fiber at 1.542 μm. 4.0-ps transform-limited pulses having an optical bandwidth of greater than 1 nm were broadened to 230 ps, and recompressed to 12 ps, showing compensation of 95% of the fiber dispersion     

基于悬臂梁啁啾调谐的光纤光栅滤波器

提出并发展了一种基于悬臂梁结构的啁啾光纤Bragg光栅(CFBG)啁啾调谐方案,获得了一系列性能优异的可调谐CFBG滤波器,包括调谐范围达到36 nm(1.8～37.8 nm)的带宽可变反射滤波器、色散在178～2 100ps/nm范围内可调的色散补偿器、基于取样CFBG或重叠写入CFBG的信道间隔可调谐滤波器等。这些FBG滤波器不但能维持较高的反射率,还能保持中心波长基本不变。     

Adjustable dispersion-compensation devices with wavelength tunability based on enhanced thermal chirping of fiber Bragg gratings

We demonstrate a dispersion compensation device based on thermal chirping of a glued fiber Bragg grating. The device can change the group velocity dispersion (GVD) while maintaining a center wavelength or change the center wavelength while preserving a GVD value. The GVD can be tuned from -122.5 to -57 ps/nm with a center wavelength at 1552.9 nm. On the other hand, the center wavelength can be shifted by 2.2 nm with a GVD value around -105 ps/nm.