Ultrawide 75-nm 3-dB gain-band optical amplification witherbium-doped fluoride fiber amplifiers and distributed Raman amplifiers

An extremely large 3-dB gain-bandwidth of 75 nm (1531-1606 nm) is achieved with a partially gain-flattened erbium-doped fluoride fiber amplifier and a distributed Raman amplifier. The Raman amplifier consists of a 85-km dispersion-shifted fiber (transmission fiber) and a practical 1505-nm Fabry-Perot laser diode pump. 9×2.5 Gb/s wavelength-division-multiplexing (WDM) transmission is successfully demonstrated using two 75-nm gain-band amplifiers as in-line and preamplifiers     

Analysis and design of Kemp-type 3-dB quadrature couplers

An analysis is presented of the 3-dB quadrature coupler of Kemp et al. (Electron Lett., vol.19, p.197-9, March 1983), and a table of element values is given. It is shown that the Kemp approach overcomes the tight coupling problem associated with the method of E.G. Cristal and L. Young (IEEE Trans. Microwave Theory Tech., vol.13, no.9, p.544-58, 1965), but there is a severe bandwidth contraction penalty. It is also shown that the use of interconnection lines sufficiently long to reduce cross-coupling causes an unacceptable degradation in coupling performance. Although the technique provides a useful increase in bandwidth over that obtainable from a single-section coupler, it is suggested that the tandem multisection method is more suitable for decade bandwidths     

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     

Comprehensive analysis of two cascaded semiconductor optical amplifiers for all-optical switching operation

This paper presents numerical calculations and experimental results for two cascaded semiconductor optical amplifiers (SOAs) in a counterpropagating configuration for an all-optical switching operation. A detailed theoretical analysis with regard to the gain evolution and the extinction ratio (ER) through the SOAs' cavities show that the two cascaded SOAs have improved performance over the single SOA configuration. A measured ER up to 20 dB is obtained for close contra-directional signal wavelengths and for a wide range of optical input powers. An all-optical switching operation is realized for 2.5-GHz data pulses, and its feasibility is demonstrated with an ER higher than 12 dB over a wide range of wavelength.     

Comparison of gain clamped and conventional semiconductor optical amplifiers for fast all-optical switching

This paper reports computer simulation results to compare a Mach-Zehnder interferometer (MZI) when the two arms of it operate with gain-clamped and conventional semiconductor optical amplifiers (gcSOA and convSOA, respectively) for fast all-optical switching. The comparison is for demultiplexing optical pulses from 160 Gb/s to the base rate of 10 Gb/s or 40 Gb/s. The gain dynamics of the gcSOA is presented, the switching windows at the drop port of the MZI for both cases that were referred before and finally an evaluation of them is discussed.     

Integrated wavelength-selective optical MEMS switching using ring resonator filters

An integrated optical microelectromechanical system (MEMS) switch that provides wavelength selectivity is described. The switching mechanism is based on moving a MEMS actuated optically absorbing membrane into the evanescent field of a high-index-contrast optical ring resonator. By controlling the loss, and thus, the cavity quality factor, the resonant wavelength is switched between the drop and through ports.     

Proposal of a wavelength-selective switch based on an MMIMZIconfiguration with wavelength-selective phase-tuning circuits

This paper proposes a novel photonic device for wavelength-selective switching. The device is based on a multimode-interference Mach-Zehnder interferometer (MMIMZI) configuration with wavelength-selective phase-tuning circuits (WSPTC). Mode propagation theory is used for the analysis of this device     

Narrow-band wavelength-selective directional couplers made of dissimilar single-mode fibers

Asymmetrical wavelength-selective fiber couplers with a bandwidth of 22.5 nm have been constructed and investigated. The special shapes of the measured sidelobes in the power transmission characteristics are explained by the bending profiles of the fibers.     

Low-power all-optical broad-band switching device using ytterbium-doped fiber

All-optical photonic switching has been demonstrated at 1310 nm and 1545 nm using an all-fiber Mach-Zehnder interferometer incorporating ytterbium-doped silica fiber. The switching was achieved with 980 nm excitation from a laser diode, with a power-length product of 3.7 mW/spl middot/m and 5.8 mW/spl middot/m at 1310 nm and 1545 mm respectively, thus giving low power all-optical switching at the preferred telecommunications wavelengths.     

Ultrafast all-optical switching using highly nonlinear chalcogenideglass fiber

Ultrafast all-optical switching with a switching power of 14 W was demonstrated in a Kerr shutter configuration using a single-mode As₂S₃-based glass fiber only 48 cm long. The nonlinear refractive index of the fiber was evaluated from the switching characteristics to be n₂=4.2×10^-14 (cm²/W), which is higher by two orders of magnitude than silica glass fiber     

Adiabatic 3-dB couplers, filters, and multiplexers made with silicawaveguides on silicon

The performance of adiabatic 3-dB couplers and V-branches is reported. These devices are broadband and divide power equally. They have no observable polarization dependence. Typical excess losses relative to a straight waveguide is 0.1-0.2 dB for the 3-dB couplers and about 0.4 dB for the V-branches. Fiber to fiber insertion loss of 0.31 dB was measured for a 2.5-cm straight waveguide. The devices were used to fabricate transmission filters peaked at 1.55 μm and power combiners having two channels at 1.48 and 1.55 μm. The device fabrication was improved by use of a flowable top cladding layer containing boron and phosphorous which easily filled-in between closely spaced waveguides     

2noscillators combined with 3-dB directional couplers for output power summing

A method of combining 2ⁿidentical oscillators with 2ⁿ- 13-dB directional couplers for output power summing is described. Preliminary experimental results obtained at about 19 MHz with 32 tunnel diode oscillators and lumped constant 3-dB directional couplers show that the output power is multiplied by approximately 32.     

Optical packet switching and buffering by using all-optical signal processing methods

We present a 1 /spl times/ 2 all-optical packet switch. All the processing of the header information is carried out in the optical domain. The optical headers are recognized by employing the two-pulse correlation principle in a semiconductor laser amplifier in loop optical mirror (SLALOM) configuration. The processed header information is stored in an optical flip-flop memory that is based on a symmetric configuration of two coupled lasers. The optical flip-flop memory drives a wavelength routing switch that is based on cross-gain modulation in a semiconductor optical amplifier. We also present an alternative optical packet routing concept that can be used for all-optical buffering of data packets. In this case, an optical threshold function that is based on a asymmetric configuration of two coupled lasers is used to drive a wavelength routing switch. Experimental results are presented for both the 1 /spl times/ 2 optical packet switch and the optical buffer switch.     

Analysis of channel addition/removal response in all-optical gain-clamped cascade of lumped Raman fiber amplifiers

The effect of addition and/or dropping of wavelength-multiplexed channels in a network comprising three concatenated lumped Raman fiber amplifiers (LRFAs) have been analyzed by numerical simulation and verified experimentally. The first LRFA in the cascade is gain clamped using a ring-laser configuration, and the lasing power propagates through the cascade. A large-signal numerical model that incorporates time variation effects and the downstream propagation of signal, upstream propagation of pumps, and downstream and upstream propagation of amplified spontaneous emission spectral components has been used for the theoretical analysis. The LRFAs consist of 16 km of dispersion-compensating fiber counterdirectionally pumped at 1455 nm by a Raman fiber laser. Channel addition/removal is simulated by propagating through the cascade of LRFAs optical power from two laser diodes. One of them is square-wave modulated at 500 Hz, and power fluctuations of the second continuous-wave signal caused by the cross-gain saturation effect in LRFAs are monitored.     

Flat-gain fiber Raman amplifiers using equally spaced pumps

This paper analyzes the gain flatness of multiwavelength pumped fiber Raman amplifiers using equally spaced pumps with both a fixed and an optimized central pump wavelength. The signal gain ripple using equally spaced pumps is compared with the case in which the pump wavelengths are allowed to vary for two, four, and eight pumps with 20-, 40-, and 80-nm signal bandwidths. The paper shows that using an optimized central pump wavelength with equal pump spacing simplifies system design, while the gain ripple is no more than 0.4 dB larger than the ripple obtained when the pump wavelengths are optimized for the cases considered.     

An all-optical implementation of a 3-D crossover switching network

One of the more promising interconnection schemes proposed for use in photonic switching networks is the crossover interconnection network; however, reported implementations of the crossover have been limited in size and complexity. A large-scale cascadable implementation of the optical crossover network that capitalizes on planar symmetric self electrooptic effect device (S-SEED) arrays is discussed. A fully functional experimental prototype with 32 inputs and 32 outputs that was operated at a maximum rate of 55.7 kb/s is also discussed. It is also shown that S-SEED arrays can be operated as simple two-input two-output nodes (called 2-modules) within a controllable network     

Dynamic circuit provisioning in all-optical WDM networks using lightpath switching

In this paper we investigate the problem of provisioning holding-time-aware (HTA) dynamic circuits in all-optical wavelength division multiplexed (WDM) networks. We employ a technique called lightpath switching (LPS) wherein the data transmission may begin on one lightpath and switch to a different lightpath at a later time. Lightpath switches are transparent to the user and are managed by the network. Allowing LPS creates a number of segments that can use independent lightpaths. We first compare the performance of traditional routing and wavelength (RWA) assignment to routing and wavelength assignment with LPS. We show that LPS can significantly reduce blocking compared to traditional RWA. We then address the problem of routing dynamic anycast HTA dynamic circuits. We propose two heuristics to solve the anycast RWA problem: anycast with continuous segment (ACS) and anycast with lightpath switching (ALPS). In ALPS we exercise LPS, and provision a connection request by searching for the best candidate destination node is such a way that the network resources are utilized efficiently. In ACS we do not allow a connection request to switch lightpaths. The lightpaths to each candidate destination node of a request are computed using traditional RWA algorithms. We first compare the performance of ACS to ALPS and observe that ALPS achieves better blocking than ACS. Furthermore, we also compare the performance of these two anycast RWA algorithms to the traditional unicast RWA algorithm. We show that the anycast RWA algorithms presented here significantly outperform the traditional unicast RWA algorithms.     

三波长反向泵浦喇曼放大器的优化与系统实现

将三波长反向泵浦的光纤喇曼放大器的增益优化问题转化为有约束条件的非线性规划问题,并用二次规划法求解。在优化结果的指导下,建立了实验系统,并利用放大的自发喇曼辐射谱微调泵浦功率实现了70nm带宽上平均增益为10dB、增益波动小于1dB的喇曼放大。     

多泵浦拉曼光纤放大器增益均衡的研究

基于受激拉曼散射原理,根据传输方程,用数值解法计算了单泵浦输入时的拉曼光纤放大器的增益;在此基础上,计算了多信道信号输入时,多泵浦拉曼光纤放大器的增益,并和文献的实验结果做了比较;用遗传算法优化泵浦参数以实现多泵浦拉曼光纤放大器的增益均衡。 1