Optical tee coupler for data bus system with single multimode fibres

A new type of optical tee coupler was developed for a data bus system with single multimode fibres. It is constructed of a wedge-shaped mirror and three graded-index rod lenses. Its three ports, which are ready to plug in, interconnect asymmetrically with one another. For a laser diode of wavelength 0.9 ?m, the coupling losses between three fibres attached into the ports were adjusted to be 3.9 to 7.9 dB. The coupler insertion losses were 1.3 to 2.5 dB.     

基于光纤传输的激光引信仿真系统

激光引信是制导武器普遍使用的近炸引信，然而要在实验室内获得接收机窗口处的光信号功率并验证信号处理系统的准确性是比较困难的。针对这一问题，提出一种基于光纤传输的激光引信仿真系统。此系统首先通过耦合透镜和自聚焦透镜将发射机输出的激光束耦合进入光纤通道，然后通过程序控制的宽带光强衰减器实时地模拟光束经过目标反射引起的光强衰减，最后将衰减后的光信号通过光纤传输并经过耦合透镜馈入引信的接收机窗口。该系统的设计能够较为准确地模拟激光引信在交会过程中的回波光功率大小，并可实时地仿真激光引信各通道的回波信号，从而可以在实验室内验证激光引信信号处理系统的可靠性。     

Optical waveguide directional coupler measurements using amicrocomputer-assisted TV camera system

Characterization of optical waveguide directional couplers using a microcomputer-assisted TV camera system is reported. A fluorescent technique is employed to visualize wave propagation in the optical waveguides, which exhibit small scattering. The method is simple and reproducible, and can be used to estimate waveguide losses and evaluate various optical devices such as waveguide lenses and waveguide interferometers on substrates. As an example of its application, parallel and nonparallel dual-chamber directional couplers and parallel triple-channel directional couplers are measured. Power transfer between the coupled channel waveguides is observed clearly, and coupling coefficients of the couplers are obtained nondestructively. The measured performance of the couplers is in good agreement with that predicted by coupled-mode analysis     

Operating regimes of an optical coupler combined fiber laser system

Rate equations have been used to study an optical coupler combined Er³⁺-doped fiber laser system, in which a common mirror attached at one of the coupler output ports is shared by two constituent lasers. Three regimes may be identified for the system depending on the relative magnitude of the wavelength difference δλ between the two constituent laser fields to the reflection band of the fiber gratings. Taking into consideration the transmission features of the coupler-mirror combination, appropriate boundary conditions have been established according to the operation regimes of the compound system. After neglecting the backgrounds losses of the fiber, rate equations have been simplified to a set of algebra equations. Based on the algebra equations, we discussed in detail the case where the laser field generated by the first laser with a wavelength slightly different from that of the field oscillating inside the second laser, is injected into the other laser by the common mirror, leading to a decreased gain for the oscillating field.     

激光半主动导引头光学系统设计

激光制导导引头是当今最常用的制导装置,本文设计的激光半主动制导导引头由光学接收系统和一个四象限探测器组成。本文对四象限探测器的工作原理进行了分析介绍。结合激光器的发射功率、作用距离与四象限探测器的参数,对导引头光学系统参数进行了计算与分析,得到了系统入瞳的最小尺寸。应用ZEMAX软件对激光半主动导引头的光学系统进行了优化设计,并通过包围圆能量曲线、光斑均匀性等对光斑质量进行了评价。使用MATLAB软件对能量曲线进行拟合,根据拟合曲线对光斑的能量分布进行评价。     

Polarizing grating coupler for high Q laser cavities

A coupling grating made in the last high-index layer of a highly reflective multilayer laser output mirror, located at the outside of the laser cavity, induces a significant fall of the reflection coefficient for one of the polarizations. The lasing polarization does not suffer more than 0.1% scattering. The understanding of device operation revealed by experiments shows the way for achieving an industrial manufacturing scheme, despite the poor control which layer-deposition technologies presently have on the layer index and thickness separately.     

Polarization-maintaining optical fibers used for a laser diode redundancy system in a submarine optical repeater

Polarization-maintaining optical fibers are developed for installation in a submarine optical repeater. These fibers preserve the polarization of light emitted from laser diodes (LD's) to a single-mode fiber through a light-switching coupler. Crosstalk of less than -30 dB in a 1-m length of these optical fibers, called PANDA optical fibers, is achieved with a bending radius greater than 10 mm, twists of less than 60 turns, and tension of less than 3 kg, and ambient temperatures of-20-80degC. The mechanical strength of these fibers is the same as that of single-mode fibers.     

Optical directional coupler based on Si-wire waveguides

We fabricated optical directional couplers with Si-wire waveguides and demonstrated their fundamental characteristics. Their coupling-length was extremely short, several micrometers, because of strong optical coupling between the waveguide cores. Wavelength demultiplexing functions were also demonstrated for devices with a long coupled waveguide. Optical output from a device 800 /spl mu/m long changed reciprocally with 2.5-nm wavelength spacing between the parallel and cross ports.     

半导体激光器光束匀化系统的光学设计

为了提高半导体激光器光束的均匀性,设计了非球面与微柱透镜阵列相结合的匀光系统。快轴方向利用光线追迹设计非球面匀化透镜;慢轴方向采用微柱透镜阵列对光束进行分割叠加。半导体激光器输出光束通过该匀光系统,在目标面上可以得到能量匀化的方形光斑。利用Zemax光学软件对半导体激光器单管和阵列进行匀化仿真,验证了该匀化系统应用于半导体激光器整形的可行性,得到了目标面动态范围变化对均匀度的影响程度,研究了微柱透镜阵列间距变化及快轴匀化透镜旋转对光斑均匀度的影响。单管和阵列在输出面上的光斑均匀度均大于90%,能量传输效率分别为95.4%和96.2%。该设计结果对半导体激光器光束匀化具有一定的参考价值。     

Optical bistability in a nonlinear directional coupler

In the nonlinear directional coupler, the optical field and the nonlinear material usually interact in a spatially and temporally local fashion and the device exhibits a nonlinear transmission characteristics, but it is not bistable. In this paper, it is shown theoretically that optical bistability in the input optical power is possible for the nonlinear directional coupler if the local phase change of the optical mode propagating through tile coupler is influenced by the excitation over the whole coupler. This condition can be satisfied in a coupler based on biased-pin-diodes comprising coupled asymmetric quantum wells in the i-region, Calculations show that in this configuration, the nonlinear directional coupler can exhibit sharp switching characteristics, low switching optical powers, optical bistability or bifurcation     

用于Nd:YAG激光医疗系统的插入式光纤光束耦合器的机械设计

本文介绍一种用于Nd:YAG激光医疗系统的插入式光纤光束耦合器,就该耦合器机械设计及装调中一些问题进行一定的探讨。     

Diode laser array excited star coupler suitable for Fibernet II

18- and 100-port fibre-optic coupler systems are driven by 10 emitter laser arrays capable of CW output powers in excess of 500 mW/facet. This source has advantages over both LEDs and conventional laser diodes, including insensitivity to feedback, no modal noise, ease of coupling and a very high launched power per output fibre.     

非成像式激光告警系统的光学设计及优化

针对非成像式激光告警系统的工作特点与要求,提出并设计了一种双片式柱透镜光学结构。对柱面光线追迹以及柱透镜成像进行了深入分析,提出了一种新型像差优化方法,使其在子午方向各个视场的调制传递函数得到最大幅度的优化。此光学系统由两片硒化锌柱透镜组成,满足了1.0~4.0 m 工作波长范围,并且克服了传统单片式柱透镜和柱面反射镜视场通常小于1且聚焦线斑不理想的缺点,其视场达到20,在7lp/mm 空间分辨率条件下,边缘视场子午方向的调制传递函数值优于0.7,达到了非成像式激光告警系统的要求。     

Component redundancy vs system redundancy in the hazard rateordering

Design engineers are well aware of the stochastic result which says that (under the appropriate assumptions) redundancy at the component level is superior to redundancy at the system level. Given the importance of the hazard rate in reliability and life testing, we investigate to what extent this principle holds for the stronger stochastic ordering, viz, hazard rate ordering. Surprisingly, this does not hold for even series systems if the spares do not match the original components in distribution. It is true for series systems however for matching spares, and we conjecture that this is the case in general for k-out-of-n:G systems. We also investigate this principle for cold-standby redundancy (as opposed to active or parallel redundancy)     

宽发射面激光二极管光束整形系统的光学设计

宽发射面激光二极管作为泵浦源在全固态激光器中得到了广泛的应用,但由于快慢轴发散角太大和发光面的不对称,所以需要对其进行光束整形。针对发光面为1m（快轴）200m（慢轴）且远场光斑为矩形光斑的宽发射面激光二极管,分析了输出光束在平行于p-n结方向上光场（侧模）的多光丝分布特性。通过在ZEMAX非序列里,设置合理的光丝间隔、尺寸和以纵模为间隔的多个波长,模拟了与实际相符的远场光斑。利用圆柱透镜压缩激光二极管快轴发散角,再用自聚焦透镜进行聚焦,最后在离自聚焦透镜后端面1.8 mm处得到快慢轴方向长分别为0.15 mm0.17 mm的方形光斑,且快慢轴方向发散角分别为3.32.4。同时,通过实验逐步比较了光束通过每一个光学元件后光斑形状的变化和光强分布,结果表明:宽发射面激光二极管光束整形中,通过引入侧模光丝结构的矩形光斑模拟方法是可行的。     

Optical homodyne receiver with a six-port fibre coupler

The performance of a PSK optical homodyne system based on a six-port fibre coupler, which avoids the need for an optical 90° hybrid device, is determined. Depending on the actual receiver implementation using the coupler, the receiver sensitivity is shown to be about 0.5?3 dB from ideal and local laser excess intensity noise can be cancelled.     

用于HCN激光器耦合输出的F-P腔的优化设计

本文介绍一种由双面金属栅网构成的F-P腔式激光耦合输出端,改变其间距,透过率可连续变化。将栅网等效为一导纳,利用等效电路方法,进行模拟计算。经优化计算得到一组最佳栅网参数。     

Semiconductor laser with tapered-rib adiabatic-following fiber coupler for expanded output-mode diameter

A new expanded-mode AlGaAs diode laser with reduced far-field divergence and 0.9 dB single-mode optical fiber coupling loss is demonstrated. This new laser achieves a two-dimensional (2-D) expansion of the fundamental output mode with a rib waveguide tapered in only one dimension. Stable fundamental-mode operation with a narrow, 5.7/spl deg/ by 7.40 full-width-at-half-maximum far-field divergence is observed well above lasing threshold. Tapered waveguide dimensions are compatible with conventional optical lithographic techniques, making this device suitable for mass production.     

一种便携式激光多普勒测速光学系统的设计

为了将激光多普勒测速技术应用于野外流体速度测量,设计了一种基于舣光束模式的激光多普勒测速光学系统,采用光纤耦合半导体激光器作为光源,通过保偏光纤耦合器、保偏光纤准直器以及非球面透镜来实现激光的分束、准直与聚焦,形成干涉条纹,并利用接收透镜、针孔光阑以及雪崩光电二极竹检测多普勒信号光.结果表明,所设汁的光学系统的空间分辨...     

Square ring laser diode with MMI coupler cavity

A square ring laser diode is designed and fabricated in which a multimode interference 3-dB coupler operates as an output coupler and a ring resonator simultaneously. This merged structure allows a shorter cavity length and a lower loss in the output branching. Lasing in the ring cavity is confirmed and the spectra are also measured.