All-Optical Modulation-Format Convertor Employing Polarization-Rotation-Type Nonlinear Optical Fiber Loop Mirror

An all-optical modulation-format convertor with regenerative function based on fiber nonlinearity is proposed and demonstrated. The convertor was formed utilizing polarization- rotation-type nonlinear optical fiber loop mirror and could operate at both on–off keying (OOK) to OOK and OOK to phase-shift keying (PSK) format conversions only by simply rotating the optical axis of the intra $lambda/2$ waveplate, without excess-loss generation and realignment of the driving conditions of control optical signals in the format exchange. The 40-Gb/s OOK to OOK/PSK format conversions were successfully performed utilizing this new type of the all-optical convertor. The results also revealed that this convertor has a reshaping function to degraded control signals as an inline all-optical regenerator.      

Experimental Investigation of Polarization Effects in Semiconductor Optical Amplifiers and Implications for All-Optical Switching

A free-space contra-propagation configuration is implemented and pump-probe studies are undertaken in order to study polarization-dependent gain dynamics in bulk semiconductor optical amplifiers (SOAs) and their application to gain and polarization switching. The polarization dependence of the gain compression shows that the co-polarized case, in which the pump and probe are ${hbox{TE}}$-polarized, is the optimum for gain switching. When injecting light polarized at 45$^{circ}$, an additional contribution due to the presence of rotating fields is observed, and the cross-polarized case is found to be the most promising for polarization switching. The potential for all-optical switching based on nonlinear polarization rotation (NLPR) induced in the SOA is then assessed through characterization of the dynamics of the state of polarization. It is demonstrated that by careful selection of the orientation of a linear polarizer in front of the detector, it is possible to reduce the recovery time from 100 to 5 ps. The improvement comes about from the selection of the intraband fast gain recovery dynamics. Polarization switching offers potentially faster switching times compared to gain switching as well as an extinction ratio improvement of $sim $10 dB.      

Experimental Demonstrations of All-Optical Phase-Multiplexing Using FWM-Based Phase Interleaving in Silica and Bismuth-Oxide HNLFs

We propose an all-optical phase-interleaving technology based on dual-pump four-wave mixing (FWM) in highly nonlinear fiber (HNLF). The proposed all-optical phase-interleaving technology is applied in an all-optical phase-multiplexing scheme to successfully phase-multiplex 2x or 3$,times,$10-Gb/s DPSK-WDM signals to a 20- or 30-Gb/s DPSK in non-return-to-zero (NRZ) formats. The proposed all-optical phase multiplexing scheme is demonstrated using dual-pump FWM in highly nonlinear silica and bismuth fibers. In contrast with optical time-division multiplexing technology, the proposed all-optical phase-multiplexing technology does not require pulse-carving, thus offering a high spectral-efficiency. Differential precoder for each input tributary is operated independently, and no additional encoder or postcoder is required to recover the original data after demodulation on the receiver side.      

All-Optical Analog-to-Digital Conversion Using Split-and-Delay Technique

We propose a simplified configuration of all-optical analog-to-digital (A/D) conversion using nonlinear optical loop mirrors (NOLMs). While the conventional scheme of such all-optical A/D conversion requires encoders and threshold, for -bit resolution, the proposed configuration realizes an -bit resolution only using a single encoder and threshold, based on a split-and-delay technique, in which the encoder and the threshold operate more than times as fast as the sampling speed. After discussing detailed design issues of the NOLM-based encoder with particular emphasis on the so-called counterpropagating effects, all-optical 3-bit A/D conversion at 10 GS/s is experimentally demonstrated using the proposed configuration.     

All-Optical Network Consortium-ultrafast TDM networks

We describe recent results of the Advanced Research Projects Agency (ARPA) sponsored Consortium on Wideband All-Optical Networks which is developing architectures, technology components, and applications for ultrafast 100 Gb/s time-division multiplexing (TDM) optical networks. The shared-media ultrafast networks we envision are appropriate for providing low-access-delay bandwidth on demand to both future high-burst rate (100 Gb/s) users as well aggregates of lower-rate users (i.e., a heterogeneous user population). To realize these goals we are developing ultrafast network architectures such as HLAN, described here, that operate well in high-latency environments and require only limited processing capability at the ultrafast bit rates. We also describe results on 80-Gb/s, 90-km soliton transmission, 100-Gb/s soliton compression laser source technology, picosecond short-pulse fiber ring lasers, picosecond-accuracy optical bit-phase sensing and clock recovery, all-optical injection-locked fiber figure-eight laser clock recovery, short-pulse fiber loop storage, and all-optical pulse width and wavelength conversion     

All-Optical Packet Routing--Architecture and Implementation

We report in this paper the architectural design and implementation of all-optical packet networks. Using photonic switches to route information, an all-optical network has the advantages of bit rate, wavelength, and signal format transparencies. Within the transparency distance, the network is capable of handling a widely heterogeneous mix of traffic. We will describe our research on the implementation of all-optical backbone switches. The switch components including frame synchronizers, frame delineation units, frame header over-writing units, wavelength converters, frame concentrators, and WDM buffers were constructed at 2.5 Gb/s. Their subsystem and device structure as well as preliminary performance are reported.     

All-Optical Clock Recovery From NRZ-DPSK Signal

All-optical clock recovery (CR) from 20-Gb/s nonreturn-to-zero differential phase-shift-keying (NRZ-DPSK) signal is demonstrated, with an all-fiber delay interferometer (DI) and a mode-locked semiconductor optical amplifier (SOA) fiber laser. The tunable DI serves as an all-optical DPSK demodulator and the phase-modulated NRZ-DPSK signal is converted into the intensity-modulated pseudoreturn-to-zero (PRZ) signal, with the enhancement of the clock component. Followed SOA fiber-laser is used to achieve CR from the PRZ signal. Fixed bit pattern and 2³¹-1 pseudorandom binary sequence NRZ-DPSK signals are used to test the performance of the proposed system. It is shown that the recovered clock signal with the extinction ratio over 10 dB and the root-mean-square timing jitter of 800 fs can be achieved     

Polarization-Insensitive All-Optical Flip-Flop Using Tensile-Strained Multiple Quantum Wells

We demonstrate a polarization-insensitive all-optical flip-flop based on a multimode-interference bistable laser diode. Polarization-insensitive flip-flop operation is demonstrated with the set power as low as $-$3 dBm, by applying 0.3% tensile strain to the multiple quantum wells gain medium. The output state of polarization is stabilized to the transverse-magnetic mode irrespective of input polarization, indicating that our device also offers a polarization-stabilizing function. Dynamic switching is achieved without waveform distortion even when the input polarization state is scrambled.      

All-Optical Generation and Switching of Few-Cycle Millimeter-Wave Pulses

We conducted a comparative study of two schemes of photonic generation and switching of few-cycle sub-THz or millimeter wave (MMW) pulses by use of a photonic-transmitter-mixer (PTM) module with a broadband and high-power near-ballistic uni-traveling carrier photodiode (NBUTC-PD). In the first scheme, we performed all-optical ultra-fast switching (bias modulation) of the PTM injected with a 93 GHz optical local-oscillator signal. Sub-2-cycle short MMW pulses with central frequency at 93 GHz were generated. To compare, in scheme 2, we employed femtosecond optical short pulses to directly excite the PTM under a DC bias (optical modulation). The former approach is shown to be capable of providing much less signal distortion and much shorter pulse duration than the latter.     

Dynamic Wavelength Assignment for WDM All-Optical Tree Networks

We develop an on-line wavelength assignment (WA) algorithm for a wavelength-routed WDM tree network. The algorithm dynamically supports all$bf k$-port traffic matrices among$N$end nodes, where$bf k$denotes an integer vector$[k_1 ldots, k_N]$and end node$i, , 1leq ileq N$, can transmit at most$k_i$wavelengths and receive at most$k_i$wavelengths. Our algorithm is rearrangeably nonblocking, uses the minimum number of wavelengths, and requires at most$d^ast-1$lightpath rearrangements per new session request, where$d^ast$is the degree of the most heavily used node. We observe that the number of lightpath rearrangements per new session request does not increase as the amount of traffic$bf k$scales up by an integer factor. In addition, wavelength converters cannot reduce the number of wavelengths required to support$bf k$-port traffic in a tree network. We show how to implement our WA algorithm using a hybrid wavelength-routed/broadcast tree with only one switching node connecting several passive broadcast subtrees. Finally, using roughly twice the minimum number of wavelengths for a rearrangeably nonblocking WA algorithm, we can modify the WA algorithm to be strict-sense nonblocking.     

Plasmon-Assisted Self-Encrypted All-Optical Memory

All-optical responsive nanomaterials, which can rapidly switch between two stable states, have been regarded as the next-generation memories due to their potential to realize binary information storage and implement on-chip, integrated photonic neuromorphic systems. Rare earth oxides are preeminent candidates owing to their extraordinary luminescent stability and narrow optical transitions. However, due to the lack of simple and effective optical switches, it is difficult to realize all-optical data storage, encoding, and retrieval by pure rare earth-doped luminescent nanoparticles. Here, a rapid and high-contrast of 10⁴ luminescent switching of Y₂O₃:Eu³⁺ nanoparticle between the enhancement and quenching states is achieved by employing the strong light confinement and ultrafast thermal response of localized surface plasmon resonance. A self-encrypted all-optical memory is presented with optical information writing, encryption, reading, and re-writing, and a high-sensitivity synaptic response of emitters to frequency and light intensity flux, which can be harnessed to encrypt information flows and promote convenient and high-security information encryption. Such a convenient and secure plasmonic thermally assisted self-encrypting luminescent switch paves the way for constructing high-performance stimuli-responsive rare earth oxide crystals on demand and expanding their applications in various data encryption, anti-counterfeiting, and rewritable colouration devices.     

Implementation of an All-Optical Time-Slot-Interchanger Architecture

We demonstrate a wavelength-converter-based optical time-slot-interchanger. It consists of three cascaded programmable delay stages and employs the first hybrid integrated, on a chip, quadruple array of semiconductor optical amplifier Mach-Zehnder interferometer switches. It exhibits error-free operation with 10-Gb/s nonreturn-to-zero packets and a power penalty of 1.8 dB.     

One-Level Simplification Method for All-Optical Combinational Logic Circuits

We propose a novel one-level simplification method for all-optical combinational logic circuits. With the proposed method, an all-optical gray code to binary coded decimal converter is successfully developed for the first time by using conventional semiconductor optical amplifiers as building elements. In comparison to the construction algorithm based on the conventional two-level simplification method, a significant improvement is observed in the Q-factor.     

WDM Intelligent Transport Network for All-Optical Routing

Conventional optical wavelength division multiplexing (WDM) networks calls for optoelectronic conversion for each wavelength in every node plus a large management effort for proper packet routing. All-optical networks are still unavailable. Here, a new architecture is described where the optical transport is done without conversions (except at extreme nodes), and with minimal routing management effort. The present basic mechanism is, firstly, to gather (at any source node) the packets demanding for a certain destination node K. Secondly, all these packets are modulated onto wavelength K. Next, the wavelength is routed towards node K by passive directional devices. As other source nodes reuse wavelength K, an anti-collision mechanism is presented. This mechanism uses very economic and widely available components. The present arrangement seems to be pre-wired, conveying packets from source to destination nodes almost automatically. The present arrangement is simpler and far more economical than (G)MPL()S arrangements, for instance. Additionally, the present system does not demand for expensive wavelength conversions or central protocols. The disadvantage over (G)MPL()S is that the present arrangement limits its maximum number of operational nodes to the number of wavelenghts WDM is able to support.     

注入锁定半导体激光器全光波长转换技术

波长转换器是光通信网络中的一个重要器件。而除半导体光放大器（SOA）外，半导体激光器也是进行波长变换的一种很好选择。基于半导体激光器的注入锁定波长变换技术具有转换带宽较大、啁啾小、消光比特性好、结构简单、成本低廉等诸多优点。将探测光与信号光同步注入法布里-珀罗（F-P）半导体激光器，可以通过信号光功率的变化控制激光器锁模与失锁，导致腔内纵模变化，探测光随之被共振放大或减弱，从而将信息由信号光转换到探测光频率上。从静态实验入手，对半导体激光器的注入锁定现象及光信号控制法布里-珀罗纵模移动等问题分别进行了研究。分析了动态转换激光器工作点的选取问题，在动态实验中实现了较宽范围的正相与反相波长转换，转换速率达到了10Gb／s。     

Characterization of All-Optical Regeneration Potentials of a Bistable Semiconductor Ring Laser

All-optical pulse reamplification, reshaping (2R), and retiming (3R) using a monolithic bistable semiconductor ring laser (SRL) is demonstrated for the first time. The regeneration performance of the SRL is characterized with an all-optical settable switching threshold, achieving significant increases in the extinction ratio (ER) of the output pulse for input ER as low as 1 dB. For retiming, a rectangular retiming window generated by a clean clock signal is used to eliminate the timing jitter in the input pulse. For input pulse with peak-to-peak timing jitter as high as $sim {hbox {12}}%$ of the bit period, the timing jitter in the retimed output pulse is reduced to $ ≪ 2%$ of the bit period. The pulsewidth of the final regenerated data can be controlled by changing the width of the retiming window. The SRL is, therefore, shown to have a “hard” digital performance in both amplitude and time domain suitable for all-optical 3R.      

All-Optical Label/Payload Separation at 40 Gb/s

We demonstrate an all-optical label/payload separation circuit implemented with hybridly integrated semiconductor-optical-amplifier-based Mach–Zehnder switches. It is shown to operate error-free with 40-Gb/s variable length data packets containing$2 ^7-1$pseudorandom bit sequence and short guardbands between them. The circuit requires only the data packets as input and its complexity does not increase with label length.     

Network Dimensioning in WDM-Based All-Optical Networks

The problem of network dimensioning, which involves optimal network designs using minimal resources for a given well-predicted traffic between individual nodes but without a pre-determined network topology, is analyzed in details in this paper. Such optimal designs are critical as the network resources are directly related to the cost of implementation. The problem complexity increases as the traffic between every node pair varies in a periodic manner. Furthermore, the presence of wavelength conflicts makes the network-dimensioning problem distinct and more complicated than that for traditional circuit-switching networks. Here, we adopt the approach based on a multi-commodity flow problem. A general cost function covering the resources of all system components is formulated, and two solution approaches are presented; one based on integer programming and one on heuristics.     

40-Gb/s Polarization-Insensitive All-Optical Clock Recovery Using a Quantum-Dot Fabry–PÉrot Laser Assisted by an SOA and Bandpass Filtering

We experimentally demonstrate polarization- insensitive all-optical clock recovery using a passively mode-locked quantum-dot Fabry–PÉrot (QD-FP) semiconductor laser at 40 Gb/s. Polarization insensitivity is achieved by using a wavelength conversion stage based on cross-phase modulation in a semiconductor optical amplifier and optical bandpass filtering. A clock signal with a root-mean-square timing jitter of 300 fs is recovered for an input data signal with a scrambled state-of- polarization (SOP). This is comparable to that from the QD-FP laser alone for an input signal with a fixed SOP. Moreover, an improvement in the tolerance to a degradation in the optical signal-to-noise ratio of the input signal is achieved by the use of the wavelength conversion stage.      

基于磷酸盐玻璃微球腔的全光调谐光纤滤波器

提出并研究了一种基于磷酸盐玻璃微球腔的全光调谐光纤滤波器。利用自制的磷酸盐玻璃预制棒,以拉丝的方式制作出直径为200~500μm、纤芯-包层折射率差为0.004的磷酸盐玻璃光纤。利用大功率CO_2激光器熔融加热光纤制备出Q值达7.28×10⁵的微球腔。利用1550 nm波段的可调谐激光器,通过锥形光纤耦合方式激发微球腔内回音壁模式(WGM)共振,获得带宽约2 pm、插入损耗小于0.3 dB的耦合共振谱。在不同功率泵浦光的注入下,磷酸盐玻璃微球腔具有比普通石英微球腔更高的光敏感特性。实验结果表明:当微腔泵浦光功率增加时,磷酸盐玻璃微球腔内的WGM共振谱向短波长漂移(蓝移),光热调谐灵敏度约为72.727 pm/mW,线性度大于0.99;在相同光功率变化下,普通石英微球腔内的WGM共振谱向长波长漂移(红移),光热调谐灵敏度约为0.086 pm/mW,线性度较低。本文提出的磷酸盐玻璃微球腔全光调谐滤波器具有全光控制、结构紧凑、稳定性好、超窄带宽和调谐效率高等优势,在光纤传感和光纤通信等领域具有重要应用。