Coupling efficiency and sensitivity of an LED to a single-mode fibre

Simple expressions are derived to estimate the coupling efficiency and sensitivity of an LED butt-coupled to a single-mode fibre. The concept of the single-mode numerical aperture is revised so as to incorporate the wave nature of the coupling process. Our analysis agrees well with experimental results.     

Low-current 1.3-µm edge-emitting LED for single-mode fiber subscriber loop applications

Light-emitting diodes coupled to single-mode fiber can offer an economical and reliable alternative to the use of diode lasers in many single-mode fiber systems. This paper describes index-guided InGaAsP edge-emitting LED's (ELED's) which couple 7 μW into single-mode fiber at a drive current of only 20 mA. The devices exhibit rise times of less than 1.5 ns and can be modulated at data rates in excess of 432 Mbit/s. Operating characteristics of these low-current ELED's are well-suited for single-mode fiber subscriber loop applications.     

激光二极管与单模保偏光纤的耦合分析

给出一种处理激光二极管经透镜与单模保偏光纤耦合的精确方法,讨论了透镜参数、耦合形式、激光二极管像散对耦合效率的影响,给出两种实际耦合系统的计算结果并与实验结果作了比较     

Transmission at 1 Gbit/s over 7.4 km of single-mode fibre using an edge-emitting LED and PINFET receiver

Transmission at 1 Gbit/s over 7.4 km of 1300 nm optimised single-mode fibre has been demonstrated using a standard, 1300 nm edge-emitting LED with 150 MHz 3 dB bandwidth and a PINFET receiver. Computer simulation was used to accurately assess each of the system degradations: LED rise/fall, extinction ratio, dispersion penalty and receiver noise.     

Very high radiance edge-emitting LED

In this paper we describe a new light-emitting diode (LED) whose radiance is 1000 W/cm²sr, an order of magnitude higher than any previous LED. The LED is an (AlGa)As double-heterojunction edge-emitting structure. This structure acts as a waveguide for the internally generated light, and with appropriate Al concentration difference at the heterojunctions (Deltax approx 0.3) and active region width (∼500Å), the radiation pattern perpendicular to the junction can be less than 30° (FWHM). For fiber-optic communications this LED is capable of coupling 850 μw, at a coupling loss of only -10 dB into a 0.14-numerical-aperture (NA), 90-μm-diam low-loss fiber. The LED is capable of being directly modulated at 250 MHz and has a spectral width of less than 300 Å.     

Linear InGaAsP edge-emitting LED's for single-mode fibercommunications

A 1.3-μm edge-emitting diode with a linear radiance and high coupled power into a fiber is described. The LED yields 60 μW of coupled power into a single-mode fiber at a driving current of 100 mA and an ambient temperature of 25°C. A V-groove structure with an optical absorption region separated from an active region is used. At active layer thicknesses below 0.14 μm, linear current-light output characteristics are obtained. The spectral modulation depth is 0% over the entire emission spectral width of 75 nm, and coherence length is 22.5 μm. LED characteristics are achieved in the range from -30 to 85°C at a driving current of 100 mA. The LEDs exhibit a cutoff frequency of 250 MHz. LED reliability is discussed using results of accelerated aging carried out at the ambient temperatures of 50, 125, and 200°C. The activation energy of degradation is determined to be 0.63 eV, and LED half-lives are estimated to be in excess of 10⁶ h     

Optical transmission with single-mode fibres and edge-emitting diodes

Edge-emitting diodes operating at 1.3 ?m wavelength are used to launch between 5 and 10 ?W of optical power into single-mode fibres at a driving current of 100 mA. This permits the transmission of 140 Mbit/s over a distance of more than 10 km.     

Gigabit single-mode fiber transmission using 1.3-µm edge-emitting LEDs for broad-band subscriber loops

This paper describes gigabit single-mode fiber transmission using 1.3-μm edge-emitting LED's for broad-band subscriber loops, focusing on a method of calculation for maximum transmission distance and 1.2-Gbit/s and 600-Mbit/s transmission experiments. Gigabit single-mode fiber transmission is necessary for subscriber loops, especially in broad-band ISDN and optical CATV systems. Edgeemitting LED's are excellent light sources because of their high power launched into the fiber compared with surface-emitting LED's, and currently lower cost and higher reliability than laser diodes. The maximum transmission distance is carefully estimated by taking into account the wavelength dependence for both chromatic dispersion and loss of the single-mode fiber, and the possibility of gigabit transmission near the dispersion free wavelength 1.3 μm, is confirmed. Encouraged by the above results, we demonstrate 1.2-Gbi,t/s 10-km and 600-Mbit/s 20-km transmission experiments using a newly developed 1.3-μm edge-emitting LED and a new driver circuit with a simple response compensation circuit. These results show the proposed calculation method and the LED response compensation circuit to be powerful tools for the realization of low-cost gigabit single-mode fiber transmission using edge-emitting LED's.     

单模光纤与SOI纳米线波导耦合设计

波导光栅在集成光学发展中扮演着重要的角色。与其他的耦合方法相比,光栅耦合器具有耦合效率高、制备封装成本低、无需芯片端面抛光、可以在任何地方实现信号输入输出等优点,成为纳米光波导最有潜力的耦合方法。本文提出利用OPTIFDTD软件仿真结合MATLAB编程的方法精确计算光栅耦合效率的新方法。仿真分析了光栅的周期、槽深、占空比、SiO2层厚度等光栅参数对耦合效率的影响,并给出了使输入光栅耦合器耦合效率达到42.6%;输出光栅耦合器的耦合效率达到72.3%的一组最佳光栅参数。     

Distributed single-mode fiber to single-mode planar waveguidecoupler

Light transfer between a curved single-mode fiber and a single-mode planar waveguide is investigated experimentally in dependence on the refractive index and thickness of the planar waveguide and for different polishing depths. Marcuse's model is applied to treat theoretically the coupler, leading to a very good agreement with the experimental results     

High-power InGaAsP edge-emitting LEDs for single-mode optical communication systems

The letter describes 1.3 ?m InGaAsP edge-emitting LEDs which couple 40 to 60 ?W into a single-mode fibre. The 1.0 ns rise times and 30 to 45 nm spectral widths of these LEDs make suitable for optical communication systems operating at data rates as high as 400 Mbit/s.     

Laser to single-mode fiber assembly using an electroforming technique

One of the most difficult problems in coupling laser diodes to single-mode fibers is maintaining alignment while the two components are locked into place. The authors report a novel approach to the lockup process that uses electroforming. This technique solves the isolation and train relief problem by locking the laser and fiber into a single structure rather than by mounting both to a common base. With this novel technique and simple butt coupling, coupling efficiencies as high as 14% have been achieved with very little alignment shift during lockup. The completed structure is at least 100 times smaller in volume than conventional packages and provides strain relief and isolation from mechanical disturbances.<>     

Theory of LED coupling to single-mode fibers

A theory is developed to estimate the coupling efficiency and sensitivity of an LED coupled to a single-mode fiber. Our analysis is found to be in good agreement with experimental results.     

LED fundamentals: Comparison of front- and edge-emitting diodes

We establish a criterion for the maximum amount of power that can be launched into an optical fiber relative to a front-emitting diode of given active layer (junction) thickness. According to this criterion it should be possible to obtain 7.5 times the amount of power from a light-emitting diode (LED) of optimum design relative to a front-emitting LED whose active layer of equal intrinsic brightness is 2.5 μm thick. We also discuss the performance of edge-emitting diodes and find that the LED's of our examples are capable of providing approximately 50 percent of the power expected from the ultimate diode configuration.     

New analysis of LED to single-mode fibre coupling

It is shown that the coupling efficiency between partially coherent sources like LEDs and single-mode fibres can be calculated from near-field and far-field data. Good agreement with experimental results is found.     

2 Gbit/s and 600 Mbit/s single-mode fibre transmission experiments using a high-speed Zn-doped 1.3 ?m edge-emitting LED

High-speed heavily Zn-doped mesa-structure 1.3 ?m edge-emitting LEDs have been developed for single-mode-fibre high-speed transmission. A 600 Mbit/s modulation without waveform equalisation, and a 2 Gbit/s modulation with equalisation, have been performed. At 2 Gbit/s, 9.8 km of single-mode-fibre transmission using the edge-emitting LED has been carried out for the first time.     

Coupling efficiency of surface-emitting LED's to single-mode fibers

Using coherent-mode representation, the light emission of a surface-emitting LED (SELED) with a Lambertian far-field and a uniform near-field intensity is expressed by coherent modes. The coupling efficiency of the SELED to a single-mode fiber is calculated as the weighted sum of the coupling efficiencies of the coherent modes to the fiber mode. The absolute maximum achievable efficiency is found to be the inverse of the number of the coherent modes, and is equal to (lambda^{2}/pi A), whereAis the LED emission area and λ is the emission wavelength. This efficiency can be obtained by butt coupling if the LED areaAis about equal to or larger than the fiber mode size. The theoretical prediction agrees well with published experimental data.     

High-power broad mesa structure AlGaAs/GaAs single-quantum-well edge-emitting LED

An edge-emitting light-emitting diode (LED) with a wide emitting region for optical sensing and information processing which requires slit-shaped light sources is discussed. Through the use of a high-quantum efficiency single-quantum-well structure grown by molecular beam epitaxy an output power as high as 3 mW at an injected current of 100 mA with a 50- mu m-wide mesa structure is achieved at the 780-nm emission wavelength. A uniform and rectangular intensity profile, which is suitable for practical use, is obtained with a mesa-restricted structure.<>     

多模光纤到单模光纤耦合效率的研究分析

由于多模光纤的纤芯直径远大于单模光纤的纤芯直径,且多模先纤的数值孔径也大于单模光纤的数值孔径,因此多单模转换效率极低.为了提高多模光纤到单模光纤的耦合效率,采用自聚焦透镜对从多模光纤出射的光束进行汇聚,使其半径大小尽量与单模光纤的芯径大小相匹配,然后再利用球透镜来减小被汇聚过的光束的发散角,在不考虑各种连接损耗的前提下,通过ZEMAX来求解多模光纤到单模先纤的耦合效率.采用这种新型组合透镜耦合的方法可以极大提高多单模耦合的耦合效率,其最高耦合效率可达到38.7%.因此,这种组合透镜法是可行的.