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1.
提出了一种光纤横截面折射率变化呈旋转非对称变化的长周期光纤光栅(R-LPFG) 结构,并利用多层圆波导理论和横截面折射率离散分析方法,结合模式耦合方程组和数值求解方法理论分析了这种光栅的模式耦合特征.理论分析表明R-LPFG纤芯基模主要与一阶非对称包层模发生耦合,当光栅旋转度逐渐变大时,R-LPFG基模会与一阶非对称包层模的奇模和偶模同时发生耦合,这就会使原来单一的谐振峰逐渐分裂成双峰,这是常规光栅类型所不具有的透射谱特征.由于R-LPFG的双峰来自同一对耦合模式,它们对温度的响应很相似,因此可利用双峰间距来进行无需温度补偿的扭曲、应变等物理量的测量.最后利用高频CO2激光脉冲写入法制作了这种光栅,并实验研究了这类光栅的传输谱演变特征,实验结果和理论分析一致.可以预见,这类光栅在光纤传感或通信中将具有较大的潜在应用价值. 相似文献
2.
长周期光纤光栅的折射率敏感特性 总被引:1,自引:0,他引:1
利用光波导的耦合模理论分析了长周期光纤光栅(LPFG)的折射率传感特性,给出了LPFG 的谐振波长相对于环境折射率变化时的漂移量解析表达式.对 LPFG 的折射率传感特性进行了数值模拟.结果表明:在光栅周期不变的情况下,当包层折射率小于且接近外界环境折射率时,波长的漂移量增大,且对应的模次越高、包层半径越小、包层折射率越小,波长漂移量越大,即 LPFG 对应于外界折射率传感灵敏度得到显著提高;当外界环境折射率大于包层折射率时,光栅的谐振波长将近似不变. 相似文献
3.
We demonstrate a femtosecond laser microfabricated fiber Mach-Zehnder interferometer and reveal the dependences of the sensitivities of different environmental parameters on the specifications of the interferometer. A 30-mm-long fiber interferometer at a wavelength of 1593 nm exhibits a temperature sensitivity of 0.103 nm/°C, axial strain sensitivity of -1.35 pm/με, and refractive index sensitivity of -15.294 nm/RIU, respectively. In addition to dependence on interferometer length, the sensitivities are also strongly dependent on the operation wavelength of the selected interference order. When the operation wavelength is selected at 1525 nm, the sensitivities are 0.085 nm/°C, -0.09 pm/με, and -13.824 nm/RIU, respectively. 相似文献
4.
Highly sensitive cladding-etched arc-induced long-period fiber gratings for refractive index sensing
We have investigated the effects of cladding etching in arc-induced long-period fiber gratings. Comparing the position of the resonant wavelengths at each diameter with the corresponding theoretical dispersion curves of effective refractive index, it is found that some of the resonances show a better match with anti-symmetrical cladding modes, while others with symmetrical cladding modes. Etching the cladding diameter to ∼39 μm, results in coupling to a high-order cladding mode that is very sensitive to changes in the ambient refractive index. The resonant peak shifts remarkably (∼230 nm) toward shorter wavelengths as the external refractive index increases. This sensitivity is higher than any previously reported in arc-induced long-period fiber gratings. 相似文献
5.
提出了一种光纤横截面折射率变化呈旋转非对称变化的长周期光纤光栅(R-LPFG) 结构,并利用多层圆波导理论和横截面折射率离散分析方法,结合模式耦合方程组和数值求解方法理论分析了这种光栅的模式耦合特征.理论分析表明R-LPFG纤芯基模主要与一阶非对称包层模发生耦合,当光栅旋转度逐渐变大时,R-LPFG基模会与一阶非对称包层模的奇模和偶模同时发生耦合,这就会使原来单一的谐振峰逐渐分裂成双峰,这是常规光栅类型所不具有的透射谱特征.由于R-LPFG的双峰来自同一对耦合模式,它们对温度的响应很相似,因此可利用双峰间
关键词:
光纤传感
光纤光栅
2激光')" href="#">CO2激光
旋转折变 相似文献
6.
A true single-step process suitable for fabrication of micro-periodic structure in polymer films by two photon initiated photopolymerization and laser ablation is presented. By the right choice of the irradiation energy, the irradiated zone is modified or ablated in the 1.44-μm-thick film. The mechanism of grating generation and the potential application of the gratings in integrated optics are discussed. 相似文献
7.
The sensing characteristics of long period gratings (LPGs) in photonic crystal fiber (PCF) can be changed by using femtosecond laser to modify the PCF waveguide structure although dispersive characteristic plays a key role in determining the sensitivity. Based on the coupled local-mode theory, the coupling behaviors and spectral characteristics of the LPGs in PCF fabricated by a femtosecond laser and a CO2 laser are analyzed which are supported by experiment results. When the distance between the central of fiber core and the peak of the drilled hole, namely the micro-hole diameter is about 3.5 μm, the temperature and strain sensitivities are changed by 27% (from 6.20 to 7.81 pm/°C) and −21% (from −2.41 to −1.91 pm/με) in comparison with the changes of the sensitivities that is induced by CO2 laser. The investigation demonstrates that the local structural changes of PCF have an impact on the sensitivity of LPGs. The investigation demonstrates the versatility of the technique in potential applications to design the desired sensitivity of fiber grating flexibly by forming proper geometrical modulations. 相似文献
8.
We report a novel fiber design for obtaining long period gratings (LPGs) having a broad transmission spectrum. These gratings are based on guided to guided mode coupling in a staircase profile fiber. Numerical simulations predict 20 dB bandwidths as high as 100 nm and an estimated insertion loss of less than 1 dB. Such broadband LPGs are expected to find applications in many all fiber components. 相似文献
9.
Optical and Quantum Electronics - Based on the coupled mode theory, the influences of material dispersion on the spectral characteristics of the gold coated long-period fiber grating (LPFG) are... 相似文献
10.
We have used the finite-difference frequency-domain (FDFD) method to simulate the core mode to cladding mode couplings in long-period gratings (LPGs) in photonic crystal fiber (PCF). Four sets of LPG-PCF have been fabricated with respective periodicities of 590, 540, 515, and 490 μm, resulting in corresponding resonance wavelengths (RWs) of 1241, 1399, 1494, and 1579 nm. We show both theoretically and experimentally that the longer the RW, the more sensitive the LPG-PCF is to the index change in Ar. We demonstrate a robust sensitivity of 517 nm per refractive index unit using the LPG-PCF at 1579 nm RW. 相似文献
11.
Bragg gratings in rectangular microfiber for temperature independent refractive index sensing 总被引:1,自引:0,他引:1
We present fiber Bragg grating fabricated in rectangular microfiber for temperature-independent refractive index (RI) measurement. The grating has two Bragg peaks due to the high geometrical birefringence of the rectangular microfiber. The two peaks present different RI responses because the modes along the orthogonal polarizations have different energy fractions in terms of evanescent field outside the silica microfiber and hence the light/liquid interaction strength are different. In contrast, they exhibit identical temperature sensitivities because most mode energy is confined in the microfiber and the thermal-optic effect of silica dominantly determines the temperature response. As a result, temperature-independent RI sensing can be realized by monitoring the wavelength separation between the two peaks. 相似文献
12.
采用简化的三层光纤模型,从模式理论和耦合模理论出发,分析了长周期光纤光栅的耦合特性及功率透射谱,给出了长周期光栅的主要特性参数。利用计算机建模,采用Matlab软件对实用的SMF 28单模光纤加以特定的光栅折射率调制参数进行数值计算,并采用振幅掩模法刻写长周期光纤光栅进行实验验证,计算结果与实验结果相吻合。 相似文献
13.
O. Frazão C. Correia J.M. Baptista M.B. Marques J.L. Santos 《Optics Communications》2008,281(22):5601-5604
This work presents two distinct configurations based on phase-wavelength conversion using a ring fibre laser with two different long period gratings interferometer topologies. The sensors are interrogated by analysing the wavelength change of the emission laser, which is directly dependent on the interferometer phase change. The first configuration integrates a Mach-Zehnder interferometer, which is based on a pair of long period gratings and is used as sensing head for bending radius and longitudinal strain measurement. The second configuration, comprehends a Michelson interferometer, which is based on a single LPG and a fibre end mirror and is used as a liquid level sensor or as an optical refractometer. 相似文献
14.
It is proposed that the high dispersion at the transmission band edges of uniform long period gratings (LPG) fabricated on relatively high Δ fibers can be used for efficient dispersion compensation. Since the transmission of LPG varies with length of the grating or refractive index modulation, we show that it is possible to tailor the transmission spectrum to obtain high transmission with constant dispersion and negligible delay ripple over a reasonable bandwidth. Since the proposed structure works in transmission it should be suitable for fiber optic communication links. 相似文献
15.
本文提出一种在同一段少模光纤上写入两个不同周期Λ1和Λ2的长周期光纤光栅构成叠栅的方法,实现了纤芯基模LP_(01)向高阶纤芯模LP_(11)模式转换的宽带宽的新型的全光纤模式转换器.利用有限元法和耦合模理论建立了模式转换器的理论分析模型.数值仿真分析了叠栅中两个子光栅周期间隔、光栅长度、耦合系数等光栅参数对模式转换器的影响.仿真分析和实验结果表明,通过改变两个子光栅的周期间隔来改变两个损耗峰的位置,形成一个损耗峰,从而可以实现宽带宽的模式转换器,其10dB带宽约是单栅的2倍.与传统的模式转换器相比,该转换器带宽宽、转换效率高,尺寸小、抗干扰能力强,可以在模分复用系统和光通信中得到广泛的应用. 相似文献
16.
Yanhua Luo Zengchang Li Ru Chen Qijin Zhang Gangding Peng Gang Zou Bing Zhu 《Optics Communications》2009,282(12):2348-2353
Based on the photoinduced birefringence in azo materials, the model of the birefringent long period fiber gratings (BLPFGs) has been proposed and the transmission of such birefringent fiber gratings was further simulated by the coupled mode theory. In order to obtain the optimum condition for making birefringent azopolymer optical fiber (APOF) gratings the photoinduced birefringence of azo dye and methyl methacrylate (MMA) copolymers was systematically studied. After photosensitivity study of azo samples, using Teflon technique, azo dye containing single mode polymer optical fiber (POF) was fabricated. Finally, BLPFGs can be fabricated in azopolymer fiber using polarized 532 nm laser. A 120 μm LPFG with a 50% duty cycle has been successfully written within the core of the fiber with 532 nm laser by an amplitude mask method. Under polarized microphotography, the grating was observed when the optical axis was set at 45° with the direction of the first polarizing lens of the polarization microscope. 相似文献
17.
Nonlinear refractive index of a rare-earth-doped fiber laser 总被引:1,自引:0,他引:1
Bochove E 《Optics letters》2004,29(20):2414-2416
An expression is derived for the intensity-dependent index of refraction of a rare-earth-doped fiber laser by use of a Kramers-Kronig relation and simple rate equations. The solution is applied to examine the properties of the nonlinear index of an ytterbium-doped silicate fiber laser at 975-nm pump and 1080-nm laser wavelengths. 相似文献
18.
19.
采用耦合模理论,针对光纤芯层为矩形折射率分布的长周期光纤光栅,分析不同模式间耦合对计算精度的影响。结果表明:对于一阶低次包层模式,偶次包层模式与光纤芯层基模的耦合常数要远远小于奇次包层模式与光纤芯层基模的耦合常数。因此,在不影响计算精度的情况下,可以采用忽略偶次包层模式的方法来提高计算速度。同时,根据不同的计算波长范围和计算精度的要求,可以选择合适的正弦折射率调制阶数范围来减小计算工作量。 相似文献
20.
Mileńko K Hu DJ Shum PP Zhang T Lim JL Wang Y Woliński TR Wei H Tong W 《Optics letters》2012,37(8):1373-1375
In this paper we present an interferometer based on photonic crystal fiber (PCF) tip ended with a solid silica-sphere for refractive index sensing. The sensor is fabricated by splicing one end of the holey PCF to a single mode fiber (SMF) and applying arc at the other end to form a solid sphere. The sensor has been experimentally tested for refractive index and temperature sensing by monitoring its wavelength shift. Measurement results show that the sensor has the resolution of the order of 8.7×10(-4) over the refractive index range of 1.33-1.40, and temperature sensitivity of the order of 10 pm/°C in the range of 20-100 °C. 相似文献