Optimization of reflection spectra for phase-only sampled fiber Bragg gratings

In this paper, the reflection spectra of a phase-only sampled fiber Bragg grating is obtained by optimizing its phase profile. The standard simulated annealing method is improved for optimization, and superior phase profiles which contain as few segments as possible per sampling period are obtained for 8, 16 and 32 identical channels. As very well known, increased number of WDM channels results in higher grating length and refractive index modulation amplitude. It is observed that application of these phase profiles limits the increases in both of these parameters considerably.     

Ultrahigh-channel-count fiber Bragg grating based on the triple sampling method

A triple sampling method to have enabled excellent channel uniformity and high in-band energy efficiency is firstly proposed for the design of an ultrahigh-channel-count fiber Bragg grating (FBG), which is based on the simultaneous utilization of two amplitude-assisted phase sampling (AAPS) functions and a phase-only sampling (POS) function. As an example, one linearly chirped FBG with consecutive 1215 channels enabling to cover all fiber telecom bands (O + E + S + C + L + U) is numerically demonstrated, which has a length of 9 cm, a dispersion of − 1360 ps/nm, and a channel spacing of 50 GHz. The maximum index-change required for 10 dB strength of the FBG is less than 6 × 10^− 3.     

Novel flat multichannel filter based on fiber Bragg grating and phase shift

In this letter, a novel optical fiber filter based on fiber Bragg grating and phase shift is proposed for wavelength-division-multiplexing (WDM) system applications. As the channel-space of the comb filter based on chirped sampled fiber Bragg grating and phase shift was not accurate and the multi-channel was unable to channel the standard frequency, we discussed and calculated the error between theory and practice which has certificated by simulation. Then a compensatory method with phase shift between the samples was proposed, and a 80-channel comb filter with accurate 50-GHz channel-spacing was simulated, which is a good foundation for fabricating comb filters with accurate transmission peak in future.     

Channel spacing halving and multi-channel apodisation of sampling fiber Bragg grating based on Moiré effect

Channel spacing halving and multi-channel apodisation of sampling fiber Bragg grating (SFBG) based onSFBG. The experiment and theoretical analysis showed that the channel spacing could be halved whenfringe was twice the length of SFBG and the initial phase difference of two exposures was odd times of π.A novel method to control the initial phase difference of two exposures is presented in this paper. Usingthis technique, we fabricated two SFBGs with channel spacing of 50 and 100 G by a same phase mask andan apodized SFBG with channel spacing of 100 G.     

利用均匀相位掩模板制作线性啁啾光纤光栅

理论上分析并从实验上验证了一种利用均匀相位掩模板写入啁啾光纤光栅的方法:将光纤弯曲,由于光纤离掩模板的距离不同从而使光纤光栅的周期轴向渐变,由此产生啁啾。分析了这种啁啾光纤光栅的谱特性和时延特性,同时也分析了由于光纤离掩模板的距离不同而引起的折射率调制变化给光纤光栅特性带来的影响。设计了一种石英曲面,利用其使光纤按照弯曲函数进行弯曲,然后进行紫外曝光制成了线性的啁啾光纤光栅。实验中制作的啁啾光纤光栅色散值为-1102 ps/nm,纹波为17ps。通过改变弯曲函数就可以实现利用一块均匀相位掩模板制作不同啁啾量的啁啾光纤光栅的目的,降低了啁啾光纤光栅的制作成本。     

用于光纤布拉格光栅法布里-珀罗腔的改进的Rouard算法

比较了光纤布拉格光栅法布里一珀罗腔的极限法、平衡法及传输矩阵法3种算法,证明了它们是一致的,指出了光纤布拉格光栅复振幅传输矩阵的相移特性对法布里一珀罗腔透射率的影响.对计算任意折射率调制的光纤布拉格光栅的Rouard算法进行了改进,在分层方法中考虑了折射率分布初始相位的影响,获得了更为准确的反射复振幅相位特性,将该结果应用于计算光纤布拉格光栅法布里一珀罗腔,得到了光纤布拉格光栅法布里一珀罗腔具有多峰结构的透射谱,并经过实验验证了该理论的正确性.     

相移光纤光栅的制作和特性

在光纤光栅的刻蚀平台中引入精密移动电机,控制相位掩模板的移动,从而在光纤光栅的刻蚀过程中,在光栅的固定位置引入相移量,采用此简单易行的方法制作出了多种相移光纤光栅,分析所刻光纤光栅的光谱曲线,符合理论分析和设计的要求。     

多信道梳状滤波器信道间的相移补偿（已撤稿）

采样大啁啾光纤光栅理论（LCSBG）是实现超高信道数梳状滤波器的理想方案,但实际制作时存在信道间隔不准确、多信道无法同时对齐的问题,文中通过对多信道梳状滤波器反射谱特性的数值模拟分析以及信道间隔误差进行了理论计算,指出问题的来源为LCSBG 要求的光栅为周期倒数线性啁啾,并不是简单的线性啁啾.对此,提出了相移补偿方案,并以100信道,40 GHz 梳状滤波器为例进行了仿真验证,得到了理想的结果.这为实际制作高信道、高准确度的多信道梳状滤波器打下了良好的理论基础. 关键词： 光纤光栅 采样大啁啾 相移 多信道梳状滤波器     

Long-period-grating-assisted optical add-drop filter based on mismatched twin-core photosensitive-cladding fiber

A noninterferometric optical fiber add-drop channel filter based on a mismatched twin-core photosensitive-cladding fiber and long-period fiber grating is demonstrated. With assistance from the fiber grating, co-directional spectrally selective cross coupling between the two cores can be realized with an efficiency of 90%.     

Novel B/Ge codoped photosensitive fiber and dispersion compensation in an 8×10 Gbit/s DWDM system

We used the Modified Chemical Vapor Deposition (MCVD) method to fabricate a B/Ge codoped fiber with a depressed cladding in which boron and germanium were also doped, the depressed cladding was photosensitive, which can greatly suppress the cladding mode coupling. The transmission spectrum of written grating in this fiber made by the phase mask method verified its larger photosensitivity and great suppression of the cladding mode coupling. We then analyzed the Bragg wavelength tuning theory in the phase mask method in detail which gave us a more exact equation. The ultra-violet (UV) exposure system was modified, and eight cascaded Fiber Bragg Gratings (FBG) centered at different wavelengths were written in this photosensitive fiber successfully using a 248 nm KrF excimer laser and one piece of 1067 nm phase mask. Each channel spacing was 100 GH according to the Densed Wavelength Division Multiplexing (DWDM) standards of the International Telecommunication Union (ITU-T). At the same time, we also wrote in chirp in each grating by tilting the phase mask to realize dispersion compensation. The dispersion in 44 km SMF was successfully compensated by the cascaded chirped gratings in the eight channel WDM system with each channel being 10 Gbit/s.     

多信道梳状滤波器信道间的相移补偿

采样大啁啾光纤光栅理论（LCSBG）是实现超高信道数梳状滤波器的理想方案,但实际制作时存在信道间隔不准确、多信道无法同时对齐的问题,文中通过对多信道梳状滤波器反射谱特性的数值模拟分析以及信道间隔误差进行了理论计算,指出问题的来源为LCSBG 要求的光栅为周期倒数线性啁啾,并不是简单的线性啁啾.对此,提出了相移补偿方案,并以100信道,40 GHz 梳状滤波器为例进行了仿真验证,得到了理想的结果.这为实际制作高信道、高准确度的多信道梳状滤波器打下了良好的理论基础.     

一种利用相位掩模版对光栅波长进行微调的光栅刻写方法

提出并实验证实了一种刻写光栅时既能保护相位版又能对光栅的反射波长进行微调的方法.通过调整光纤和相位版之间的距离,利用1 550 nm单模光纤和掺铒分别实现了0.48 nm和2.2 nm的光栅反射波长的调节.在相位版和光纤之间的距离保持在3 mm的条件下,既可以保护相位版又可以获得高质量的光栅.     

40 Gb/s超短光脉冲序列的四相编解码实验研究

采用3码片的超结构光纤布拉格光栅(SSFBG)作为编/解码器,该编/解码器光栅包含3段子光栅(空间码片),在相邻的空间码片的边界处存在离散的四相相移(0,π/2,π,3π/2)。利用四相编解码所具有的良好自相关和互相关特性,成功实现了单信道速率高达40 Gb/s,码片速率高达240 Gchip/s的全光编解码实验。据我们所知,这是利用光纤布拉格光栅作为编/解码器的全光码分复用(OCDM)系统所达到的最高单信道传输速率。理论计算和实验结果表明了利用超结构光纤布拉格光栅(SSFBG)实现多相高速全光编解码的可行性。这样高速的全光编解码可以应用于光码分复用系统和分组交换网络。     

Flexible chirp control using the linearly inherent chirped phase mask with the equivalent chirp design

The design of fiber Bragg grating to achieve different chirp amount in the selective transmission channel is presented. The method depends on the combination effect of introduced equivalent chirp with the linearly inherent chirp provided by the phase mask. Since these two chirps can be incorporated, or be counteracted, the different chirp amount can be easily obtained.     

非啁啾取样光纤布拉格光栅反射峰值波长的分析

推导并验证了非啁啾取样光纤布拉格光栅(SFBG)反射谱中反射峰值波长的表达式。基于种子光栅中心波长对应的折射率调制深度和取样光纤布拉格光栅折射率调制函数的傅里叶级数展开式,提炼出取样光纤布拉格光栅的折射率调制深度和各阶光栅周期,从而导出其反射峰值波长的表达式。由于考虑了占空比、取样周期等取样光纤布拉格光栅的结构参量,因而表达式能够描述反射峰的分布。仿真实验中,不同占空比或取样周期下计算出的反射峰值波长、信道间隔符合数值反射谱。该表达式既适用于均匀取样光纤布拉格光栅,也适用于交流切趾和交直流切趾取样光纤布拉格光栅。     

优化二元相位取样光纤布喇格光栅及对色散和色散斜率补偿的应用

利用粒子群算法对二元相位取样光栅的周期相位调制进行优化设计，在此基础上提出了基于二元相位取样光纤布喇格光栅的色散和色散斜率补偿技术.通过光栅周期啁啾可以调整每个信道的带宽，色散量由子光栅长度决定，调整取样函数的啁啾系数可以改变色散斜率，因此可以设计出用于波分复用系统的多信道色散补偿器件.     

双波长啁啾相移光纤光栅

理论研究并实验验证了一种含有两段π相移的啁啾相移光纤光栅.采用F矩阵对啁啾相移光纤光栅进行计算并分析了该光栅的谱特性.含有两段π相移的啁啾相移光纤光栅可以在普通啁啾光栅透射谱阻带中产生双波长透射峰,透射峰位置直接取决于光栅中π相移的位置,透射峰的线宽和透射峰的波长间隔没有关系,仅随着啁啾率的增大而增大.采用带相位掩模的逐点扫描法对含有两段π相移的双波长啁啾相移光栅进行了制作,获得波长间隔为8 nm的双波长透射谱的光栅器件.该光栅的消光比和3 dB谱线宽分别为20 dB和0.08 nm,实验结果和理论设计一致.     

绝对编码光栅的相位细分及其在位移测量中的应用

提出通过光栅条纹相位的精密测量,获取光栅高精度位移信息的方法。具体方法是对光栅图像采用多码道设计,用CCD二维图像传感器获取测量段光栅图像多码道信息。对最低码道图形的周期函数序列进行傅里叶变换、基频滤波和逆傅里叶变换获得光栅截断相位分布,其余码道信息提供相位展开的级次,以此获得测量段光栅的绝对相位分布。用光刻的手段制作了实用的绝对编码光栅,基元码道的尺寸是:27.36μm用于明条纹,27.36μm用于暗条纹,最小基元码道空间周期为54.72μm,光栅长度为14008.32μm。在步长近似3μm的位移测试中,与比对的标准仪器记录值比较,标准偏差为0.2057μm,精度在亚微米量级。重复性实验表明,位置测试的稳定性为0.09μm(标准差),得到600倍以上细分的分辨力。     

非线性二次曝光法制作三角形光纤Bragg光栅

提出了一种利用非线性二次曝光技术制作三角形光纤Bragg光栅的新方法.该方法只使用普通Bragg位相模板,采用两次曝光技术,通过控制光纤光栅的本地谐振波长和反射率,达到控制光纤光栅谱形的目的.第一次直接对光纤曝光,用来控制光纤光栅谐振波长;第二次通过位相模板曝光,用来控制光纤光栅的反射率.考虑到光敏光纤感光特性曲线的多项e负指数变化规律,按照"分步写入光纤光栅设计软件"进行曝光分布设计,利用"分步曝光光纤光栅写入系统"进行曝光控制,使用信息产业部第46研究所生产的DCS-01型光敏光纤,得到了线性范围1.24 nm、反射率为0～64%的三角形光纤Bragg光栅.三角形光纤Bragg光栅作为光纤光栅传感解调器件,在光纤传感领域具有重要应用价值.     

Writing Fiber Grating of Different Wavelength Using the Same Phase Mask

Chirped fiber grating was used in dispersion compensator. We tried to use the same phase mask to write fiber grating of different wavelength with two methods to reduce the price of the fiber grating.