Temperature-insensitive long period grating sensors in photonic crystal fibre

A long period grating has been fabricated in endlessly single-mode photonic crystal fibre using a spatially-periodic electric arc discharge. The sensing characteristics of the grating have been studied and it was found to possess an insensitivity to temperature, a bend sensitivity of 3.7 nm /spl middot/ m and a strain sensitivity of -2.0 pm//spl mu//spl epsiv/.     

Macro-bending loss properties of photonic crystal fibre

Photonic crystal fibres are examined with respect to bending loss. An equivalent step-index fibre is modelled using an effective-index approach for the microstructured cladding. Measurements have been performed in a broad spectral range, and the results agree well with the calculated losses     

基于光子晶体光纤长周期光栅的双参数传感技术研究

利用高频CO2激光脉冲在折射率引导型的光子晶体光纤(PCF)上写制了长周期光栅(LPG),产生多个谐振峰。实验观察和理论分析均表明,这些峰是源于纤芯LP01模式向高阶纤芯LP11模式的耦合。通过研究产生的两个谐振峰随外界温度、弯曲、折射率和轴向应变的变化发现,LPG只对温度和轴向应变敏感,从而实现对弯曲和折射率均不敏感且能同时测量温度和应变的双参量传感器,减小了交叉敏感,其温度和轴向应变的灵敏度分别为10 pm/℃和-4.0 pm/με。     

Electric-arc-induced long-period gratings in fluid-filled photonic bandgap fibre

Electric-arc-induced long-period gratings in a fluid-filled photonic bandgap fibre (PBGF) is demonstrated. Gratings of varying pitch were fabricated and excellent agreement between the measured resonances and numerically simulated phase matching curves is obtained. The PBGF geometry allows the detection of very small arc-induced structural deformations of the fibre and their correlation with the grating strength.     

Refractive index sensing with long-period grating fabricated in biconical tapered fibre

A single long-period fibre grating was written in a biconical fibre taper made from standard communications step-index optical fibre, resulting in an interferometric fibre sensor device that provided a resolution of 1/spl times/10/sup -4/ for refractive indices in the range of 1.30 to 1.34, suggesting that these devices may be suitable for use with aqueous solutions.     

Cladding-mode extraction from long-period fibre grating using self-aligned core-mode blocker

A novel method is presented of fabricating a core-mode blocker for use in long-period fibre gratings by forming a self-aligned absorber on the end of the fibre core. The absorber efficiently suppresses the core-mode power and allows the cladding-mode radiation to pass through, thereby resulting in a bandpass output at the resonant wavelengths     

Brillouin fibre laser with 20 m-long photonic crystal fibre

Brillouin fibre laser is demonstrated using a very short length of photonic crystal fibre (PCF). A simple ring resonator is used in the experiment which consists of a 20 m long highly nonlinear PCF and 49 cm long Bismuth-based erbium-doped fibre (Bi-EDF). The proposed Brillouin laser is able to generate up to 3 Stokes and 3 anti- Stokes lines in the 1560 nm region at a channel spacing of 0.09 nm.     

PMD characteristics of twisted photonic crystal fibre

A photonic crystal fibre (PCF) with polarisation mode dispersion (PMD) of 0.03 ps/rkm was obtained by unidirectional twist. The work was also successful in reducing the PMD of the PCF to 10% of its initial value by periodic bidirectional twisting without loss increasing and structural deformation.     

Experimental study of dual-core photonic crystal fibre

The authors report the fabrication and characterisation of photonic crystal (`holey') fibres in which multiple cores are created by filling in selected air-holes with glass. The guidance mechanism is modified total internal reflection. Using a tunable diode laser, the inter-core coupling is investigated as a function of air-hole spacing     

高频CO2激光脉冲写入PCF-LPFG传感特性研究

采用高频CO2激光技术在柚子型光子晶体光纤(PCF)上写入长周期光纤光栅(LPFG),并对其温度、应变和弯曲特性进行了实验研究。实验测得,PCF-LPFG谐振波长的温度和应变灵敏度分别为0.002nm/℃和0.001 8nm/με,谐振峰损耗值对温度和应变不敏感。由于高频CO2激光写入为单侧写入,导致PCF-LPFG透射谱的弯曲特性与方向和曲率直接相关。选择弯曲灵敏度较大的方向进行了弯曲测试,测得在一定的曲率范围内,PCF-LPFG的谐振波长及谐振峰损耗值的灵敏度分别为-5.45nm/m-1和3.32dB/m-1。基于PCF-LPFG的透射谱温度不敏感特性,本文为制作不受温度影响的应变和弯曲传感器提供了新的方法。     

Simultaneous refractive index and temperature measurement usingcascaded long-period grating in double-cladding fibre

A compact scheme for simultaneous temperature and surrounding refractive index (SRI) measurement using two long-period gratings (LPGs) of different periods inscribed side-by-side in a single piece of a double-cladding fibre is presented. One of the LPGs is sensitive to both SRI and temperature, whilst the second is sensitive to temperature only     

40 Gbit/s transmission over photonic crystal fibre using mid-span spectral inversion in highly nonlinear photonic crystal fibre

Transmission at 40 Gbit/s over large mode area photonic crystal fibre (PCF) together with dispersion compensation by optical phase conjugation in a highly nonlinear PCF are demonstrated for the first time.     

Microwave photonic filtering using Gaussian-profiled superstructured fibre Bragg grating and dispersive fibre

Microwave photonic filtering is realised using a superstructured fibre Bragg grating. The time delay of the optical taps is precisely controlled by the grating characteristics and fibre dispersion. A bandpass response with a rejection level of >45 dB is achieved.     

γ-radiation-induced attenuation in photonic crystal fibre

Results are presented of what, to the knowledge of the authors, is the first study of the sensitivity of a photonic crystal fibre (PCF) under steady-state gamma irradiation. Radiation-induced attenuation of a PCF has been measured at 1.55 μm. This new type of fibre showed a higher attenuation level than a standard monomode fibre but had a fast kinetic of recovery after irradiation     

基于光子晶体光纤长周期光栅的传感器研究

详细研究了光子晶体光纤长周期光栅(LPG-PCF)的应力和温度特性,利用成功制作的温度不敏感PCF-LPG,实现了两种结构简单光纤传感器.在温度不敏感应力传感器中,PCF-LPG作为温度不敏感的应力传感头,当以波长为1553nm的分布反馈(DFB)激光器为入射光源、用分辨率为0.001dB的光功率计测量时,PCF-LP...     

Low pump power photonic crystal fibre amplifiers

Designs of low pump power optical amplifiers, based on photonic crystal fibres are presented. The potential of these fibre amplifiers is investigated, and it is demonstrated that such amplifiers may deliver gains of more than 15 dB at 1550 nm with less than 1 mW of optical pump power. We focus on the design of erbium-doped photonic crystal fibre amplifiers operated at very low pump powers. We achieve this by using PCFs with large air holes and thereby large index contrasts. With such high index contrast fibres, we may obtain very small mode field diameters.     

Electronic tunability of ferroelectric liquid crystal infiltrated photonic crystal fibre

The electronic tunability of ferroelectric liquid crystal filled photonic crystal fibres is demonstrated for the first time. The tunability is obtained in the wavelength range of 1500-1600-nm, with a free spectral range of-20-nm. The electronic tunability is achieved by applying an electric field onto the infiltrated photonic crystal fibre which facilitates the photonic bandgap tuning owing to the microsecond-order switching speeds of ferroelectric liquid crystals. The polarised transmission spectrum shows the behaviour of a tunable notch filter with a change in applied voltage. The results obtained could pave the way for the fabrication of fast tunable all-in-fibre devices in the telecom wavelength range.     

Analysis of etched long-period fibre grating and its response to external refractive index

Analytical formulas are presented for the first time to describe the shift in the resonance wavelength of a long-period fibre grating (LPFG) in response to etching of the fibre cladding or a change in the external refractive index. The accuracy of the formulas is confirmed by comparison with numerical simulations and experimental results. It is shown that the resonance wavelengths of an etched LPFG are more sensitive to the external refractive index than those of an unetched grating.