High-temperature sensor using a Fabry-Perot interferometer based on solid-core photonic crystal fiber

A micro Fabry-Perot interferometer(M-FPI) is constructed by splicing a short section of polarizationmaintaining photonic crystal fiber(PM-PCF) to an end-cleaved single-mode fiber with controllable offset. Due to the high effective optical path difference induced by the solid core of the PCF,the M-FPI has an ultrasmall cavity of approximately 110μm.The temperature sensitivity within a range from 33℃to approximately 600℃is measured to be 13.8 pm/℃,which shows good agreement with the theoretical result.This proposed sensor has the advantages of ultracompact size and high stability.Therefore,it is suitable for various space-limited sensing applications in harsh environments.     

Temperature characteristics of a core-mode interferometer based on a dual-core photonic crystal fiber

A core-mode Fabry–Perot (FP) interferometer is constructed by using a dual-core photonic crystal fiber (DCPCF). The FP cavity is formed by a single piece of DCPCF, which can also serve as a direct sensing probe without any additional components. We theoretically and experimentally studied its temperature responses in the range of 40–480 °C. The temperature sensitivity is 13 pm/°C which matches the theoretical results. Since the temperature sensitivity of the proposed sensor is independent on cavity length, precise control of the length of FP cavity or photonic crystal fiber is not required. The sensor size can be as short as 100–200 μm, and its fabrication only involves splicing and cleaving, which make the sensor production very cost-effective. The proposed FP interferometric sensor based on a DCPCF can find applications in high-temperature measurement especially those that need accurate point measurement with high sensitivity.     

Novel modal interferometer based on ring-core photonic crystal fiber

An original design of ring-core photonic crystal fiber （RPCF） is proposed. By splicing a section of the homemade RPCF between two segments of single mode fibers （SMFs）, a simple modal interferometer is presented and experimentally demonstrated. Owing to the effects of the collapsed region, the ring modes in RPCF can be effectively activated. To our knowledge, it is the first time to demonstrate the modal interferometer based on the interference between the ring modes, which is different from the previously reported interferometers based on the interference between core modes or cladding modes. The temperature and strain characteristics of the interferometers with different lengths of RPCF are investigated.     

Temperature-independent curvature sensor based on tapered photonic crystal fiber interferometer

A temperature-independent highly-sensitive curvature sensor by using a tapered-photonic crystal fiber (PCF)-based Mach-Zehnder interferometer (MZI) is proposed and experimentally demonstrated. It is fabricated by sandwiching a tapered-PCF between two standard single mode fibers (SMFs) with the air holes of the PCF in the fusion splicing region being fully collapsed. The tapering of PCF is found to enhance the sensitivity significantly. Large curvature sensitivities of 2.81 dB/m⁻¹ and 8.35 dB/m⁻¹ are achieved in the measurement ranges of 0.36-0.87 m⁻¹ and 0.87-1.34 m⁻¹, respectively, with the resolution of 0.0012 m⁻¹ being guaranteed. The proposed sensor also shows negligible temperature sensitivity less than 0.006 dB/°C.     

Mach-Zehnder interferometer formed in a photonic crystal fiber based on a pair of long-period fiber gratings

We demonstrate implementation of an all-fiber Mach-Zehnder interferometer formed in a photonic crystal fiber (PCF). We formed the all-PCF Mach-Zehnder interferometer by mechanically inducing two identical long-period fiber gratings (LPGs) in the PCF. The spectral properties of a LPG and a LPG pair were investigated. The interference fringe formed within the stop band of the LPG pair varied with the period and the strength of the gratings, and the fringe spacing was decreased with increasing grating separation. From the fringe spacing measurement the differential effective group index of the PCF was calculated to be deltam approximately equal to 2.8 x 10(-3).     

超低温度系数的光子晶体光纤Sagnac压力传感器

 提出了一种基于光子晶体光纤Sagnac干涉仪的横向压力传感器。使用的光子晶体光纤为低双折射光纤,首先预先在Saganc环中的光子晶体光纤上施加初始压力,使Sagnac干涉仪产生正弦干涉光谱,然后再将被测物体放在光子晶体光纤上,由于被测物体重力的作用,Saganc干涉仪输出的光谱产生移动,实现横向压力传感测量。传感器具有高灵敏度0.529 nm/(N·mm)及超低的温度系数-0.4 pm/℃,其环境温度的影响可以忽略。     

超低温度系数的光子晶体光纤Sagnac压力传感器

提出了一种基于光子晶体光纤Sagnac干涉仪的横向压力传感器。使用的光子晶体光纤为低双折射光纤,首先预先在Saganc环中的光子晶体光纤上施加初始压力,使Sagnac干涉仪产生正弦干涉光谱,然后再将被测物体放在光子晶体光纤上,由于被测物体重力的作用,Saganc干涉仪输出的光谱产生移动,实现横向压力传感测量。传感器具有高灵敏度0.529 nm/(N·mm)及超低的温度系数-0.4 pm/℃,其环境温度的影响可以忽略。     

Temperature-insensitive strain measurement using a birefringent interferometer based on a polarization-maintaining photonic crystal fiber

We propose a novel and simple scheme for a temperature-insensitive strain measurement by using a birefringent interferometer configured by a polarization-maintaining photonic crystal fiber (PM-PCF). The wavelength-dependent periodic transmission in a birefringent interferometer can be achieved by using a PM-PCF between two linear polarizers. Since the PM-PCF is composed of a single material, such as silica, the peak wavelength shift with temperature variation can be negligible because of the small amount of the birefringence change of the PM-PCF with temperature change. The measured temperature sensitivity is −0.3 pm/°C. However, the peak wavelength can be changed by strain because the peak wavelength shift is directly proportion to strain change. The strain sensitivity is measured to be 1.3 pm/με in a strain range from 0 to 1600 με. The measurement resolution of the strain is estimated to be 2.1 με. The proposed scheme has advantages of simple structure and low loss without a Sagnac loop, temperature insensitivity, ease installation, and short length of a sensing probe compared with a conventional PMF-based Sagnac loop interferometer.     

外腔式光纤Fabry-Perot干涉型高温应变传感器

介绍了一种外腔式光纤Fabry-Perot干涉型(EFPI)高温应变传感器,传感器是在两段切割平整的单模光纤之间熔接一段空心光纤构成。实验证明,传感器在1000℃以下时能够稳定工作,腔长变化灵敏度为0.17nm/με,应变测量灵敏度可达±1με,线性度高达0.99998。EFPI高温应变传感器结构紧凑,工艺简洁,成本低廉,是一种可靠、优秀的高温应变传感器。     

Switchable multi-wavelength fiber ring laser based on a compact in-fiber Mach-Zehnder interferometer with photonic crystal fiber

Switchable multi-wavelength fiber ring laser with an in-fiber Mach-Zehnder interferometer incorporated into the ring cavity serving as wavelength-selective filter at room temperature is demonstrated. The filter is formed by splicing a section of few-mode photonic crystal fiber (PCF) and two segments of single mode fiber (SMF) with the air-holes on the both sides of PCF intentionally collapsed in the vicinity of the splices. By adjusting the states of the polarization controller (PC) appropriately, the laser can be switched among the stable single-, dual- and triple-wavelength lasing operations by exploiting polarization hole burning (PHB) effect.     

Highly sensitive bend sensor based on Mach-Zehnder interferometer using photonic crystal fiber

Optical fiber bend sensor with photonic crystal fiber (PCF) based Mach-Zehnder interferometer (MZI) is demonstrated experimentally. The results show that the PCF-based MZI is sensitive to bending with a sensitivity of 3.046 nm/m⁻¹ and is independent on temperature with a sensitivity of 0.0019 nm/°C, making it the best candidate for temperature insensitive bend sensors. To that end, another kind of bend sensor with higher sensitivity of 5.129 nm/m⁻¹ is proposed, which is constructed by combining an LPFG and an MZI with zero offset at the second splice mentioned above.     

In-fiber modal interferometer based on dual-concentric-core photonic crystal fiber and its strain, temperature and refractive index characteristics

An in-fiber modal interferometer is demonstrated by splicing a section of homemade dual-concentric-core photonic crystal fiber (DCCPCF) and two segments of single-mode fibers (SMFs) with collapsing the air holes in the splice regions. By analyzing the transmission spectra and the spatial frequency spectra of the interferometers, it's observed that the main interfering modes are the high-order ring modes, which are different from the previously reported interferometers using the single-, few- or multi-mode fibers. The influences of the lengths of DCCPCF and the first collapsed region on the interferometers were investigated experimentally. The strain, temperature and refractive index characteristics of the interferometer were analyzed.     

Widely tunable photonic crystal fiber Fabry-Perot optical parametric oscillator

We present a widely tunable low-threshold chi(3) optical parametric oscillator. The oscillator cavity is formed by butt coupling dichroic mirrors to either end of a highly nonlinear index-guiding photonic crystal fiber. This yields a singly resonant Fabry-Perot oscillator with a high feedback fraction for the resonant parametric sideband. The tuning range of the output parametric sideband stretches from 23 to 164 THz above the pump frequency. The threshold power of the oscillator is only 15 W.     

Multi-wavelength fiber laser in single-longitudinal mode operation using a photonic crystal fiber Sagnac interferometer

In this paper, we report a new configuration of a tunable multi-wavelength erbium-doped fiber laser based on the commercial optical multiplexers and a Sagnac interferometer which includes a section of a high-birefringent photonic crystal fiber. Four-wavelength laser emission lines were obtained simultaneously in single-longitudinal mode operation showing a power instability lower than 1 dB, and an optical signal-to-noise ratio higher than 65 dB for all the emitted wavelengths. This proposed configuration allows the individual control of the loss of each channel of the laser and because of it is based on the commercial ITU-grid multiplexers, the laser is adapted to the telecommunications channel’s normative.     

Strain-insensitive and high-temperature long-period gratings inscribed in photonic crystal fiber

We fabricate and demonstrate strain-insensitive and high-temperature long-period gratings in endlessly single-mode photonic crystal fiber by use of focused pulses of a CO2 laser and a periodic stress relaxation technique without geometrical deformation and elongation of the fiber. The thermal dependence of mode coupling at 1299.59 nm is 10.9 pm/degrees C from 24 to 992 degrees C, whereas the coefficient of strain sensitivity is -0.192 pm/muepsilon up to the maximum strain of 2.74%epsilon. It is found for what is believed to be the first time that, in contrast with the traditional fiber case, the coupling resonance shifts toward shorter wavelengths under applied strain, indicating that the refractive index of the core is decreased as a result of the rebuilding of tension attributed to the stress-elastic effect, and the cladding modes is highly dispersive because of airholes arranged in the fiber cladding.     

Fabry-Perot interferometers built by photonic crystal fiber pressurization during fusion splicing

We report on a microscopic Fabry-Perot interferometer whose cavity is a bubble trapped inside an optical fiber. The microcavity is formed by pressuring a photonic crystal fiber (PCF) with large voids during fusion splicing with a conventional single-mode fiber. The technique allows achieving high repeatability and full control over the cavity size and shape. It was found that the size of the PCF voids contributes to control the cavity size independently of the pressure in the PCF. Our devices exhibit a record fringe contrast of 30?dB (visibility of 0.999) due to the ellipsoidal cavity whose surfaces compensate for the diffraction of the reflected beam. The strain sensitivity of the interferometers is higher when the cavities are ellipsoidal than when they are spherical.     

Temperature sensor based on an isopropanol-sealed photonic crystal fiber in-line interferometer with enhanced refractive index sensitivity

We fabricate a simple, compact, and stable temperature sensor based on a liquid-sealed photonic crystal fiber (PCF) in-line nonpolarimetric modal interferometer. Different from other reported PCF devices, it does not need expensive polarimetric devices, and the liquid is sealed in one fiber. The device consists of a stub of isopropanol-filled PCF spliced between standard single-mode fibers. The temperature sensitivity (-166 pm/°C) increases over an order of magnitude compared with those of the previous sensors based on air-sealed PCF interferometers built via fusion splicing with the same mechanism. In addition, the refractive index sensitivity also increases. Higher temperature sensitivity can be realized by infiltrating some liquid having a higher thermo-optic coefficient into the microholes of the PCF.     

Detection of cancer affected cell using Sagnac interferometer based photonic crystal fiber refractive index sensor

Optical and Quantum Electronics - A complex studies of optoelectronics, non-linear optical and laser stimulated piezoelectric features of chalcogenide powder-like chalcogenide crystals pure and...     

Polarization beam splitter based on photonic crystal self-collimation Mach-Zehnder interferometer

A polarization beam splitter based on a self-collimation Mach-Zehnder interferometer (SMZI) in a hole-type silicon photonic crystal was proposed and numerically demonstrated. Utilizing polarization dependence of the transmission spectra of the SMZI and polarization peak matching (PPM) method, the SMZI can work as a polarization beam splitter (PBS) by selecting appropriate path length difference in the structure. Because of its intrinsic operating principle, the PBS possesses high polarization extinction ratios (PERs). As its dimensions are only several operating wavelengths, the PBS may have practical applications in photonic integrated circuits.     

波长扫描法布里-泊罗光纤加速度计的研究

利用光纤传感器的独特优点 ,用波长扫描法将 Fabry- Perot干涉仪 (以下简称 FPI)和传统加速度计相结合 ,得到了较好的分辨率。分析了在 FPI中多光束干涉对双光束干涉的影响。实验研究表明 ,它对由振动引起的位移 (加速度 )变化相当灵敏