Small loss-deviation tapered fibre star coupler with mixer rod

A large-scale biconical tapered fibre star coupler with mixer rod was developed. It shows considerable improvement in regard to power distribution uniformity. The loss deviation and average excess loss for a 100 × 100 star coupler were 0.37 and 3.2 dB, respectively.     

Erbium-doped fibre amplifiers with an extremely high gain coefficient of 11.0 dB/mW

A gain coefficient of 11.0 dB/mW is obtained using 0.98 mu m laser diode pumped erbium-doped fibre amplifiers with a low erbium concentration of 81 p.p.m. and a high relative refractive index difference of 1.88%.<>     

Star couplers with gain using fiber amplifiers

The authors propose a novel technique for constructing large passive star couplers with gain using high-power erbium-doped fiber (EDF) amplifiers. In contrast to other proposed techniques where each output port of the coupler requires its own EDF amplifier, the proposed alternative requires few EDF amplifiers with sufficient output saturation power levels. When used in an FDM/WDM star network, the size of the coupler can be increased by a factor of m using m narrowband EDF amplifiers. Moreover, this alternative avoids coupling the pump-laser light through the star coupler itself, alleviating the requirement on designing large bandwidth couplers to accommodate the signal and the pump wavelengths     

Numerical study of passive gain equalization with twin-core fibercoupler amplifiers for WDM systems

This paper presents a numerical study of twin-core fiber coupler amplifiers for equalization of wavelength division multiplexing (WDM) channels. The propagation of WDM pulses within a coupler and a chain of couplers is analyzed. The real spectrum gain of the device is considered along with dispersion and nonlinear effects. The influence of intermodal dispersion is studied. A model is developed based on a set of linearly coupled nonlinear Schrodinger equations     

All-optical gain control of in-line erbium-doped fiber amplifiers for hybrid analog/digital WDM systems

Automatic gain control using an all-optical feedback loop in in-line erbium-doped fiber amplifiers (EDFA's) used in hybrid analog/digital wavelength division multiplexing (WDM) systems was studied. It is found that the signal level variation for the digital channels can be maintained within a range /spl les/3-dB between the presence and dropout of the analog channel when the narrowband feedback is centered at the amplified spontaneous emission (ASE) peak (/spl sim/1532 nm) with loop loss ranging between 13-22 dB. Robust transmission at 2.5 Gb/s without measurable power penalty was obtained for the digital channels when the EDFA was saturated by either the analog or the control lasing signal.     

Optimisation of refractive index profile for high gain fibre amplifiers

It is shown that appropriately designed depressed cladding fibres offer the potential for erbium doped, Raman and Brillouin fibre amplifiers which combine high gain with low scattering losses.<>     

Lossless wide-band reflective star coupler using erbium-doped fiberamplifiers

A wide-band 64-port amplified reflective star coupler (ARSC) using eight fiber amplifiers and only four pump laser diodes is demonstrated. The loss of this ARSC can be fully compensated from 1530 mn to 1565 nm due to its double-pass amplification process. The power margin increment of 21.7 dB with the power penalty of 1.3 dB and the cross-channel power penalty of 2 dB are achieved in a 1.7 Gb/s system experiment. This ARSC technology makes the star coupler cost-effective to be used in many larger wavelength division multiple access networks     

Monolithic demodulator for 40-gb/s DQPSK using a star coupler

A novel device that demodulates both quadratures of the optical differential quadrature phase-shift keying (DQPSK) format in a single interferometer by using a 4 /spl times/ 4 star coupler was demonstrated. Simultaneous measurements of both DQPSK quadratures at 42.7 Gb/s are also presented.     

波分复用双芯光子晶体光纤耦合器的设计

在双芯PCF的基础上设计一种新型定向耦合器,根据波导间相互耦合原理,采用时域有限差分法分析了该器件的光传输特性.并数值计算了双芯PCF的结构参量对耦合性能的影响,发现其耦合长度随着空气填充率d/A的减小而增大,随着传输波长λ的增大而减小.并基于双芯PCF结构,以常用通信波长为例,设计出0.85/1.55 μm,0.98...     

Directional coupler switches with optical gain

We discuss the design and characteristics of directional coupler switches in semiconductor materials (GaAs/GaAlAs) which exhibit optical gain by laser action. Equal gain in the bar and cross states is achieved by carrier-induced changes in the real as the well as the imaginary parts of the refractive index in directional coupler structures. Conditions for equal gain and crosstalk, design tradeoffs, and saturation characteristics in terms of amplified spontaneous emission in relation to saturation power are briefly discussed.     

Comparison of distributed gain in two dual-wavelength pumping schemes for thulium-doped fibre amplifiers

Using the coherent optical frequency domain reflectometry technique, a non-invasive study has been made of the distributed gain in two pumping schemes for thulium-doped fibre amplifiers. The compared schemes employed 800+1050 nm or 800+1400 nm pump wavelengths, and it was concluded that the former is advantageous over the latter primarily due to the ground-state absorption and pumping mechanism.     

Wavelength conversion using semiconductor optical amplifiers in differential mach-zehnder interferometer with tunable input coupler

A monolithically-integrated wavelength converter on an InP platform with a semiconductor optical amplifier in each arm of a differential Mach-Zehnder interferometer is presented. The data input has a tunable coupler that adjusts the splitting ratio of the optical power sent to each arm. Wavelength conversion at 40 Gbit/s is demonstrated and a conversion penalty of<2 dB is found when less optical power is sent to the delayed arm.     

Polarising fibre coupler with high extinction ratio

Fused polarising fibre couplers have been fabricated using single-polarisation single-mode fibres. When circularly polarised light is fed into the coupler, one of the two orthogonal polarisation modes suffers strong attenuation, and only one polarisation mode couples in the fused biconical taper region. The extinction ratio of the coupler is 41 dB at a wavelength ? = 1.3 ?m with a coupling ratio of 48:52.     

Transimpedance amplifiers using three cascade variable inverter gain stages

A study of a transimpedance amplifier (TIA) using three cascade variable inverter gain stages is presented. It is shown that wide dynamical range (−38 dbm) and high bandwidth (500 Mhz) TIA can be achieved. This configuration is good for the optical transmission of OC-3. Cheng Juang received the Ph.D. degree in electrical engineering from the University of Washington, Seattle, in 1990. At present, he is a full professor at Electronics Department, Ming Hsin University. Hsueh-Shu Fang received the MS in Electronics from Ming Hsin University, in 2005. At present, she is working at Texas Instruments Taipei branch. Shin-Yi Tsai is currently working toward his MS degree at Electronics Department, Ming Hsin University. Jyh-Neng Yang received the Ph.D. degree at the Department of Electronics Engineering and the Institute of Electronics, National Chiao-Tung University, Hsinchu, in 2006. Currently, he is an associate professor at Electronics Department, Ming Hsin University.     

High-power digitally tunable laser with integrated star coupler

A novel scheme for a digitally tunable laser requiring only P+Q+1 optical amplifiers for a device with in total P /spl times/ Q wavelength channels is presented A 32-channel InP/InGaAsP based device is fabricated. An optimised active layer and low on-chip losses result in a high optical output power.     

Effect of enhancing the Raman gain factor on the linearity of Raman fibre amplifiers

The effect of enhancing the Raman gain factor on the linearity characteristics of Raman fibre amplifiers is analysed. In addition to providing higher Raman gain per unit pump power, a higher value for the Raman gain factor also results in a lower value for the maximum gain, and therefore the maximum output power, available from the amplifier if it is to operate in the linear regime. This has important implications for optimising the design of Raman fibre amplifiers.<>     

1.55 μm wavelength region high-stability optical fibre lossvariation measurement using fibre coupler

A 1.55 μm-wavelength high-stability optical fibre loss variation measurement system, using a comparison method with an optical fibre coupler, was developed. Long-term stability within ±0.001 dB over a 120 hour period at a room temperature variation of ±2.2°C has been achieved     

WDM coherent star network with absolute frequency reference

A WDM coherent star network with an absolute frequency reference was demonstrated. The absolute reference was obtained from a GaInAsP DFB laser frequency-locked to an atomic Ar transition at 1.2960 μm. The resonant frequencies of a tunable fibre Fabry-Perot interferometer, locked to this absolute reference, were used to frequency-lock the transmitting lasers. Thus, the transmitting lasers operated at different, but fixed, optical frequencies. The receiver sensitivity was not degraded by the addition of the absolute frequency reference to the network     

WDM experiment using 1300/1500 nm dual-wavelength LED for single-mode fibre transmission systems

A wavelength-division-multiplexing transmission experiment using a 1300/1500 nm dual-wavelength LED modulated at 140/560 Mbit/s over 10 km of single-mode fibre has been demonstrated. This dual-LED device has a 9 ?m emitter spacing between the active facets with a coupling loss of 2.3 dB through a lens/fibre coupler. The chromatic dispersion penalty for the 1500 nm channel at 560 Mbit/s was about 6-5 dB and the electrical crosstalk penalty was 2.5 dB.     

New star coupler compatible with single multimode-fibre data links

A star coupler for optical data links for use with a single multimode fibre, as opposed to fibre bundles, was realised in the form of a multiport directional coupler assembled from bicorical tapers of multimode fibres. The insertion loss above furcation loss of the 4-paired-port coupler was measured to be 2.8 dB.