A photonic wavelength-division switching system using tunable laserdiode filters

A photonic wavelength-division switching system using semiconductor tunable wavelength filters is proposed. A switching system using wavelength switches and multistage switching networks is discussed. A crucial point in developing this switching system is to achieve a large number of wavelength-division channels. The potential of 100 wavelength-division channels in such switching systems is estimated, based on InP optical integrated circuits. A wavelength network synchronization which permits the network to utilize such a large number of wavelength-division channels without wavelength misalignment and drift is proposed. An eight-channel wavelength-division switching experiment, using phase-shift-controlled distributed feedback laser diodes as tunable wavelength filters, is reported     

Digital optical signal processing with polarization-bistable semiconductor lasers

The operations of a complete set of optical AND, NAND, OR, and NOR gates and clocked opticalS-R, D, J-K,andTflip-flops are demonstrated, based on direct polarization switching and polarization bistability, which we have recently observed in InGaAsP/InP semiconductor lasers. By operating the laser in the direct-polarization-switchable mode, the output of the laser can be directly switched between the TM00and TE00modes with high extinction ratios by changing the injection-current level, and optical logic gates are constructed with two optoelectronic switches or photodetectors. In the polarization-bistable mode, the laser exhibits controllable hysteresis loops in the polarization-resolved power versus current characteristics. When the laser is biased in the middle of hysteresis loop, the light output can be switched between the two polarization states by injection of short electrical or optical pulses, and clocked optical flip-flops are constructed with a few optoelectronic switches and/or photodetectors. The 1 and 0 states of these devices are defined through polarization changes of the laser and direct complement functions are obtainable from the TE and TM output signals from the same laser. Switching of the polarization-bistable lasers with fast-rising current pulses has an instrument-limited mode-switching time on the order of 1 ns. With fast optoelectronic switches and/or fast photodetectors, the overall switching speed of the logic gates and flip-flops is limited by the polarization-bistable laser to < 1 ns. We have demonstrated the operations of these devices using optical signals generated by semiconductor lasers. The proposed schemes of our devices are compatible with monolithic integration based on current fabrication technology and are applicable to other types of bistable semiconductor lasers.     

Simultaneous time- and wavelength-domain optical demultiplexing ofNRZ signals by using a side-injection-light-controlled bistable laserdiode

The authors have demonstrated direct optical demultiplexing of NRZ signals with simultaneous wavelength conversion by using a side-injection-light-controlled bistable laser diode module. The 250 Mbit/s demultiplexed output signals are each selected once every four bits from 1 Gbit/s NRZ optical input signals. Then each signal is regenerated and its bit width and wavelength are converted on one chip     

Bistability and self-pulsing in Cerenkov-type optical parametric interactions

A Cerenkov-type optical parametric oscillator exhibiting optical bistability, hysteresis, self-pulsing, and other effects is discussed. Noteworthy are a low threshold intensity of the pumping beam and a short characteristic time of the relaxation to steady-state light oscillations in the oscillator.     

Extreme timing jitter reduction of a passively mode-locked laserdiode by optical pulse injection

Reduction of the timing jitter to less than that of the master laser pulses was achieved for a passively mode-locked laser diode stabilized by subharmonic-frequency optical pulse injection. Detailed investigation revealed that this phenomenon originates from the short-term stability of the mode locking frequency under passively mode-locking operation with suitable bias conditions of the saturable absorber and the gain sections     

Techniques for optical packet switching and optical burst switching

Wavelength-division multiplexing appears to be the solution of choice for providing a faster networking infrastructure that can meet the explosive growth of the Internet. Several different technologies have been developed so far for the transfer of data over WDM. We survey two new technologies which are still in the experimental stage-optical packet switching and optical burst switching-and comment on their suitability for transporting IP traffic     

光纤光栅光学双稳态器件

提出在一段掺铒光纤上制作一对光纤光栅可构成一种新型低功率高速光双稳器件。利用分布反馈耦合波理论结合掺铒光纤非线性特点分析了器件的运转和双稳阈值，表明在现有技术条件下，可实现纳秒微瓦级厘米尺寸器件的光双稳运转。     

Temperature dependence of lasing wavelength in a GaInNAs laserdiode

The temperature dependence of lasing wavelength in 1.2-μm or 1.3-μm-range GaInNAs edge-emitting laser diodes (LD) was found to be small. It is almost independent of the characteristic temperature (T₀) and is equivalent to the temperature shift of the bandgap wavelength of GaInNAs (0.42 nm/°C). Since the dependence is smaller than that of 1.3-μm-range conventional InGaAsP LD's and also smaller than the required value (<0.48 nm/°C), it is concluded that the GaInNAs LD's are promising for use as 1.3-μm-range light sources because of their lasing-wavelength stability against temperature shift and a high T₀. The small dependence is due to the small effect of band filling on lasing wavelength from the deep quantum well in GaInNAs LD's     

Waveband switching in optical networks

The rapid advances in dense wavelength-division multiplexing technology with hundreds of wavelengths per fiber and worldwide fiber deployment have brought about a tremendous increase in the size (i.e., number of ports) of photonic cross-connects, as well as in the cost and difficulty associated with controlling such large cross-connects. Waveband switching (WBS) has attracted attention for its practical importance in reducing the port count, associated control complexity, and cost of photonic cross-connects. We show that WBS is different from traditional wavelength routing, and thus techniques developed for wavelength-routed networks (including, for example, those for traffic grooming) cannot be directly applied to effectively address WBS-related problems. We describe two multigranular OXC architectures for WBS. By using the multilayer MG-OXC in conjunction with intelligent WBS algorithms for both static and dynamic traffic, we show that one can achieve considerable savings in the port count. We also present various WBS schemes and lightpath grouping strategies, and discuss issues related to waveband conversion and failure recovery in WBS networks.     

Bistable solitons and optical switching

Using a particular nonlinearity (the "linear + smooth step" model) as an illustrative example, it is demonstrated numerically that cyclic switching between bistable soliton states of the highly-non-linear (generalized) Schriödinger equation can occur. Some important aspects of the switching process, including the nature and role of the intermediate states, are discussed. This numerical simulation may serve as a model of optical switching between distinctly different soliton states in a nonlinear optical fiber and should stimulate the search for the materials and mechanisms with appropriate nonlinearities.     

Hybrid switching and p-routing for optical burst switching networks

One promising switching technology for wavelength-division multiplexing optical networks is optical burst switching (OBS). However, there are major deficiencies of OBS. (1) The delay offset between a control message and its corresponding data burst is based on the diameter of a network. This affects network efficiency, quality-of-service, and network scalability.( 2) OBS adopts one-way resource reservation scheme, which causes frequent burst collision and, thus, burst loss. We address the above two important issues in OBS. In particular, we study how to improve the performance of delay and loss in OBS. To reduce the end-to-end delay, we propose a hybrid switching scheme. The hybrid switching is a combination of lightpath switching and OBS switching. A virtual topology design algorithm based on simulated annealing to minimize the longest shortest path through the virtual topology is presented. To minimize burst collision and loss, we propose a new routing algorithm, namely, p-routing, for OBS network. The p-routing is based on the wavelength available probability. A path that has higher available probability is less likely to drop bursts due to collision. The probability-based p-routing can reduce the volatility, randomness, and uncertainty of one-way resource reservation. Our studies show that hybrid switching and p-routing are complementary and both can dramatically improve the performance of OBS networks.     

1.5 μm optical filter using a two-section Fabry-Perot laserdiode with wide tuning range and high constant gain

The 1.5-μm optical filter exhibits a tuning range as wide as 188 GHz (15 Å), with 23-dB constant gain and 5-GHz constant bandwidth. A 25-channel wavelength selection with less than -10-dB crosstalk is expected with this filter. The wavelength-tunable optical filter has applications in wavelength-division multiplexing lightwave transmission systems and wavelength division photonic switching systems     

Multicast with a new switching structure in optical networks

The emergence of new services demands for a multicast function in optical networks. At the same time, wavelength converters are introduced to increase the efficiency of wavelength usage. It is because of the high cost and complex architecture of optical multicast and wavelength conversion technology, that a new switch structure is introduced, in which optical splitters and wavelength converters are shared per-node. In order to accommodate this architecture, a multicast routing and wavelength assignment algorithm in a splitter–converter-sharing optical network and a changing link weight policy to balance network traffic are proposed. By extending RSVP-TE (Resource ReSerVation Protocol-Traffic Engineering) and OSPF-TE (Open Shortest Path First-Traffic Engineering), an optical multicast mechanism is provided, and message type, signaling flow, and finite state machine model are given. Simulations of NSFNET show that, when the number of splitters and converters are 50% and 12.5% of the full equipment respectively, the performance is close to the ideal case. Using a changing link weight policy can improve performance greatly, when there are enough splitters and converters.     

Improvement of switching time in a thermocapillarity optical switch

The switching time of existing thermocapillarity optical switches is about two orders of magnitude larger than that of other optical switches, such as a thermooptics switch and a free-space switch using microelectromechanical system technology. This paper reports a thermocapillarity switch whose switching time is comparable to that of the thermooptics and free-space switches. The greatly improved switching time is achieved by lowering the absolute viscosity of the refractive-index matching liquid and improving the switch design     

155 W CW optical power from 1 cm monolithic AlGaAs/InGaAs laserdiode array

155 W continuous-wave output power from a 1 cm wide monolithic AlGaAs/InGaAs laser diode array with an emitting aperture of 4800 μm has been demonstrated at a cooling water temperature of 3°C. A continuous-wave output power of 72 W was achieved at room temperature with an emitting aperture of 1600 μm. High T₀ was observed for the laser structures     

Burst segmentation benefit in optical switching

We derive the asymptotic behavior of the ratio between the blocking probabilities of burst segmentation (BS) and just-enough-time (JET) policies in an optical burst switch. It is shown that if the ratio between the offered load and the number of wavelengths, k, is fixed and equals c as the number of wavelengths approaches infinity, the ratio between the blocking probabilities of BS and JET approaches 1 if c > 1; 0.5 if c = 1; and is O(1/k) with a constant c/(1 - c)/sup 2/ if c < 1.     

Wavelength conversion in optical packet switching

A detailed traffic analysis of optical packet switch design is performed. Special consideration is given to the complexity of the optical buffering and the overall switch block structure is considered in general. Wavelength converters are shown to improve the traffic performance of the switch blocks for both random and bursty traffic. Furthermore, the traffic performance of switch blocks with add-drop switches has been assessed in a Shufflenetwork showing the advantage of having converters at the inlets. Finally, the aspect of synchronization is discussed through a proposal to operate the packet switch block asynchronously, i.e. without packet alignment at the input     

Buffering-deflection tradeoffs in optical burst switching

A very important issue in optical burst switching (OBS) networks is the excessive burst drop when no suitable network resources are found during path reservation. In this study, a network scenario is evaluated in which AWG-based optical nodes are used as burst router nodes within the optical network. The two classical solutions to solve the burst contentions on the channels outgoing from the node are considered, that is, either based on buffering within the node, or by exploiting deflection routing. A performance evaluation is carried out to evaluate and compare these solutions for different network topologies with different node and traffic parameters. Our main contribution is to set numerical tradeoffs between burst deflection through the network and buffering in the node, so that a guidance in optical network design is provided where node buffering is inherently technologically limited.     

光突发交换中的竞争解决

在过去的几年里,全球互联网上的IP业务量呈爆炸式增长,快速增长的业务量使人们把很大一部分精力放在了发掘光纤巨大的带宽资源上面,密集波分复用(DWDM)传输技术的出现及成熟使光纤所能承载的信息量成倍增长。目前,单一光纤已能够传输Tb/s以上容量的信息,DWDM已经成为各种网络升级扩容的首选方式;另一方面,如此高速增长的业务量又给信息处理交换带来了巨大的压力。由于目前各个网络交换节点都是采用电交换方式,速率远低于信息在光域中的传输速率,这就造成了一个“电子瓶颈”。为解决这一问题,光交换成为必然的发展趋势,但是由于目前光存…