Optical poling in germanium-doped microstructured optical fiber for visible supercontinuum generation

We report visible supercontinuum generation initiated by the second harmonic generation obtained in a germanium-doped microstructured optical fiber after optical poling processing. The visible spectral broadening is due to a cross-phase modulation effect between the generated IR solitons and the second harmonic (532 nm) of the 1064 nm pump wave. The 400-650 nm white-light emission is obtained on the fundamental propagation mode of the fiber.     

Optically controllable variable fiber optical attenuator integrated in conventional optical fiber

New type of optically controllable variable fiber optical attenuator based on thermo-optical effect in liquid cladding of optical fiber is described. The thermo-optical effect in liquid cladding optical fiber causes refractive index contrast changes in core–cladding interface, what enables to change the propagating optical signal power with temperature. The temperature change is achieved by fiber based heating element using laser radiation. Attenuation up to −12 dB was achieved in static dependence and dynamic response confirmed rise time up to 24 ms.     

1 Gbit/s transmission over step-index plastic optical fiber using an optical receiver with an integrated equalizer

A single chip optical receiver with an integrated large-diameter photodiode, transimpedance amplifier, two stages active equalizer, post amplifier and 50 Ω driver is used for gigabit transmission over PMMA step plastic optical fiber (SI-POF). The large-diameter photodiode with an antireflection coating optimized for red light. The integrated equalizer enables the presented optical receiver to reach 1 Gbit/s over 50 m SI-POF at bit error ratio of 10^− 6. An error free (< 10^− 9) 1 Gbit/s data rate over 40 m standard PMMA step-index plastic optical fiber is also achieved.     

Quantum cloning with an optical fiber amplifier

It has been shown theoretically that a light amplifier working on the physical principle of stimulated emission should achieve optimal quantum cloning of the polarization state of light. We demonstrate close-to-optimal universal quantum cloning of polarization in a standard fiber amplifier for telecom wavelengths. For cloning 1-->2 we find a fidelity of 0.82, the optimal value being 5 / 6=0.83.     

Continuous-wave, totally fiber integrated optical parametric oscillator using holey fiber

We present, for the first time to our knowledge, a cw, all-fiber optical parametric oscillator that uses a holey fiber. The oscillator operates at 1.55 microns and can yield an oscillating parametric signal that consists of a single line with a 30-dB extinction ratio and a 10-pm linewidth or that consists of multiple lines. In addition to the signal and the idler, five other pairs of spectral lines can be observed that are due to multiple parametric interactions. The source reaches threshold for a pump power of 1.28 W and saturates for pump powers in excess of approximately 1.6 W.     

Development of an optical fiber hydrophone with fiber Bragg grating

A new type of optical fiber hydrophone is constructed with a fiber Bragg grating (FBG) based on the intensity modulation of laser light in an FBG under the influence of sound pressure. The FBG hydrophone shows linearity, with dynamic range about 70 dB. It can measure amplitude and phase of an acoustic field in real time, and operates in a wide range of acoustic frequency, at least from 1 kHz to 3 MHz. No signal distortion is observed in the detected signal. Because of the simplicity in its operating principle and geometry, an FBG hydrophone is expected to be an acoustic sensor of high practicality compared to a conventional optical fiber hydrophone.     

球形光纤端面效应及其应用

本文介绍了球形光纤端面的制作方法,采用射线理论和等效透镜法分析了圆球形端面多模光纤的端面效应,并给出了两个不同端面多模光纤之间耦合的实验结果。结果表明：圆球形端面光纤具有聚光特性,与平端面相比,使用圆球形端面光纤不仅可以提高光器件之间的耦合效率,而且增大了它们之间的耦合距离,利于光路调试;可广泛应用于光源与光纤、光纤与光纤、光纤与探测器之间的耦合。     

Polarization-maintaining fiber loop with double optical length and its application to fiber optic gyroscope

A novel polarization maintaining fiber (PMF) loop is proposed and used for an interferometric fiber optic gyroscope (FOG). By splicing a conventional PMF loop with two pigtailed polarization beam splitters, polarized light can be guided to propagate along the slow and fast axes of the PMF in sequence to double its effective optical length in the loop. In particular, the resultant optical length in the combined loop is partially self-compensated for some external disturbances, such as transverse strain. Primary experiments on the FOG using the proposed loop demonstrate that the average static bias deviation between-40 and +60 °C is less than 0.050 deg./h, and the average bias variation under conventional random vibration test is less than 0.10 deg./h.     

Microball lens integrated fiber probe for optical frequency domain imaging

An integrated microball lens fiber catheter probe is demonstrated,which has better lateral resolution and longer working distance than a corresponding bare fiber probe with diverging beam for Fourier domain optical coherence tomography(FDOCT) . Simulation results are shown to gain the effect of the distance between the microball lens and the bare fiber to the focusing plane and beam width. The freedom of modifying the working distance and lateral resolution is shown. This is achieved by changing the gap dis...     

Analysis of an integrated optical coherent receiver with optical state of polarization control

An integrated optical coherent receiver with continuous state of polarization control is proposed and analyzed. The receiver consists of an integrated optical polarization rotator, a state of polarization detector and a balanced mixer receiver. Continuous state of polarization control can be achieved by using two polarization rotators in series and feeding the polarization rotator outputs into the state of polarization detector whose subsequent output is used to control the voltage settings on the polarization rotator. For the general case, the polarization rotator is comprised of two phase shifters and a TE - TM mode converter. The state of polarization detector stage consists of a δβ directional coupler mode splitter. A novel fabrication technique for achieving efficient polarization splitting is discussed. A balanced mixer receiver is implemented using a passive directional coupler with 50/50 power splitting. The need for a passive device is demonstrated and a method for achieving accurate power splitting ratios using the proton exchange fabrication technique is discussed and experimentally demonstrated. An analysis of the performance of such a system including the balanced mixer receiver is carried out to identify the critical areas of fabrication. Discussion is also given to the function and characteristics of the electronic control loop.     

带光纤环的分布式光纤拉曼温度系统

 为了抑制分布式光纤拉曼温度系统的温漂和瑞利散射光窜扰反斯托克斯散射光,在传感光纤前端盲区后放置光纤取样环,用瑞利散射光解调反斯托克斯散射光及用光纤取样环的温度计算光纤线上其它点的温度,提高了系统的测温精度和稳定性。采用功率100 mW,波长1.55 μm,脉宽10 ns脉冲激光器和15 dB前置光纤放大器,100M14bitA/D转换卡及DSP作数字平均构建光纤拉曼温度系统的实验,实现了测温误差在±0.03 ℃内。     

Sensor based on an integrated optical microcavity

A novel integrated optical sensor based on a cylindrical microcavity (MC) is proposed. A MC sustains so-called whispering-gallery modes (WGMs), in which the energy of the optical field can be efficiently stored. By monitoring the scattering intensity from the MC, one can detect minute changes in the refractive index of the WGM, for instance, as a result of analyte adsorption. Measurement of a change in refractive index of as little as 10(-4) is demonstrated experimentally. The MC-based integrated optical sensor may have a size of approximately 8mum , and it is rugged and inexpensive.     

Spectral domain optical coherence tomography imaging with an integrated optics spectrometer

We designed and fabricated an arrayed-waveguide grating (AWG) in silicon oxynitride as a spectrometer for spectral domain optical coherence tomography (SD-OCT). The AWG has a footprint of only 3.0 cm × 2.5 cm, operates at a center wavelength of 1300 nm, and has 78 nm free spectral range. OCT measurements are performed that demonstrate imaging up to a maximum depth of 1 mm with an axial resolution of 19 μm, both in agreement with the AWG design parameters. Using the AWG spectrometer combined with a fiber-based SD-OCT system, we demonstrate cross-sectional OCT imaging of a multilayered scattering phantom.     

微结构芯大模场平顶光纤及其传输特性分析

通过在纤芯引入非均匀分布的高折射率介质柱, 获得了大模场面积、平顶型模场分布的新型微结构光纤. 运用数值仿真, 分析了光纤在不同的结构参数下的模场面积、基模模场分布等特性. 研究结果表明: 通过合理设计光纤的包层和纤芯参数, 可以实现有效的平顶模场分布. 在工作波长为1064nm时, 平顶光纤的基模模场面积可以达到1655μm². 关键词： 大模场面积 平顶光纤 微结构芯 数值仿真     

有源光放大器链路中交叉相位调制的不稳定性

利用两种方法研究了有源放大器波分复用系统光纤链路中交叉 相位调制的不稳定性．首先利用非线性薛定谔耦合方程，在小幅度扰动下，研究了正常色散 和反常色散光纤中的交叉相位调制不稳定性. 由于相位噪声涨落，利用分裂步长傅里叶 变换法与Monte-Carlo法，模拟了有源放大器链路中反常色散和正常色散情况下的调制不稳定性. 两种方法得到的结论基本一致. 关键词： 调制不稳定性 交叉相位调制 斯托克斯带 反斯托克斯 带     

Design and operation of an evanescent optical fiber sensor

Design and operation of an optical fiber sensor based on the intensity modulation is reported in this article. Two distinct mechanisms are considered for the optical power loss and the sensor operation is explained in terms of these effects. The dominant loss mechanism is found to be the evanescent loss and based on this phenomenon the optical fiber sensor is designed. Performance of this sensor is tested as a liquid level sensor for water and the experimental results are reported. The dry and wet signals for this probe are measured for a series of measurements and important factors concerning the design and operation of sensor are described. The precision of measured values, reproducibility of the results, and the stability of sensing operation as a function of time are reported. Variation of the output reading of the sensor system for different launching power is also investigated. The output signal of an optical fiber sensor in general is nonlinear, but both the signal difference (dry minus wet) and diff/dry signal ratio for the reported sensor show linear dependence with the launching power at intensities below threshold. The reported results are promising and verify the successful operation of such a device as an on/off level switch and also as a liquid level sensor.     

A new design for an integrated optical isolator

We propose a new isolator structure for MT modes using the non-reciprocal phase shift of an asymmetric magnetooptic waveguide. The new design does not require phase matching between a magnetooptic and an anisotropic material. The required waveguide length, however, is larger than in previously suggested designs.     

Fabrication of an optical fiber reflective notch coupler

A method of fabricating a reflective notch coupler in an optical fiber has been developed. The coupler consists of a 45° microprism that penetrates into the core of a multimode optical fiber. One face, at 90° to the fiber axis, is nonreflective, and one face, at 45° to the fiber axis, is reflective. Our method of fabricating a notch and selectively mirroring only the 45° face is low-cost, precise, and easily scalable. The coupler allows near-100% coupling of light into an optical fiber from the side, while allowing coupling of any desired fraction of light out from the core at a 90° angle on the opposite side of the fiber.