All-optical Packet Research Articles

A Review on Nonlinearity in Semiconductor optical Amplifer as Application in all Optical Signal Processing

The optical signal processing is the future of communication network. High speed all-optical packet routing is one of the essential applications of all-optical networks which is only possible with the development of all-optical logic technology. The development of optical logic elements and circuits are the steps in the growth of this technology and higher speed up to Tbit/sec can be achieved. The optical carrier frequency range 1013 to 1016 Hz provides enormous potential bandwidth with superior information carrying capacity over a long transmission distance. The need of higher capacity is continuing to encourage research in wavelength division multiplexing (WDM) and optical time division multiplexing (OTDM) based transmission systems, which need optical demultiplexing and wavelength conversion technology. Therefore, for high-speed optical networks, it is required to develop the all-optical gates to avoid power consumption in opto-electronics conversion. All optical logic gates perform computing operations, storage and transmission of data using light also known as optical computing. Optical technology promises massive upgrades in the efficiency and speed of computers, aswell as significant shrinkage in their size and cost. The non-linear optical device to be used i.e. Semiconductor Optical Amplifier (SOA) has proved to be the promising for all optical functions like wavelength conversion, logic functions, signal representation in all optical domain. Its compact size, high gain, fast response, strong refractive index variation, easy to manufacture and integration, and power efficiency makes it most optimum device for optical signal processing. In this paper, the application of SOA in optical processing is thoroughly reviewed and orient towards the latest application in neural networks.

A novel variable-length header extraction scheme based on ring laser for all-optical packet switching network

In this paper, a novel header extraction scheme based on a semiconductor ring laser is proposed and simulated for the proof of principle. This scheme is to be used in all-optical packet switching networks which can extract return-to-zero (RZ) modulation data packets with variable header/payload length and intensive spacing. Simulations and numerical analysis for a 3-byte header and 128-byte payload show that this structure can extract headers with more than a 20 dB contrast ratio. Additionally, the structure's simplicity and its small size makes it a proper candidate for integration with other all-optical circuits.

Large-capacity and low-loss integrated optical buffer.

Temporarily storing light occupies a pivotal position in all-optical packet switching network and microwave photonics. An integrated optical buffer with large capacity and low loss is demonstrated on a silica wafer. The optical buffer consists of four silica waveguide delay lines connected by five thermo-optic switches. With different switch combinations applied, related delay lines are selected to realize a different storage time in the buffer, and a storage time up to 100 ns with a 10-ns step size is implemented. By optimizing the fabrication process and introducing the offsets between straight and bending waveguides, the propagation loss as low as ~1.08 dB/m is achieved. This large-capacity and low-loss buffer enables broad applications in optical communications and microwave photonics.

Construction of Polynomial-Size Optical Priority Queues Using Linear Switches and Fiber Delay Lines

One of the main problems in all-optical packet switched networks is the buffering of packets. A popular solution for buffering packets is to use a set of fiber delay lines attached to a switch. A priority queue is one of the most general buffering schemes that allows the packet with the highest priority to depart the buffer on a departure request and dropping of the lowest priority packet if a new packet arrives when the buffer is full. We present a recursive algorithm for constructing optical priority queues of polynomial size from a switch with linear number of inputs/outputs and fiber delay lines. The best known lower bound allows the construction of a priority queue of size $2^{M}$ using a switch of size $M$ . However, the best known upper bound constructs a priority queue of size $M^{3}$ using a switch of size $M$ . We show that it is possible to construct a priority queue of size $O(M^{c})$ for a fixed constant $c$ using a switch of size $O(M)$ .

Study of all-optical logic XNOR gate based on XGM in linear optical amplifier

Future digital optical communication cannot develop without all-optical high-speed optical devices, especially in the field of high speed large capacity optical transmission, all-optical packet switching and optical computing, and thus optical logic devices are becoming a hotter spot of research. Based on the cross-gain modulation (XGM), a novel scheme of all-optical logic XNOR gate using linear optical amplifier (LOA) is presented in this paper. LOA results show a good gain characteristic, which can get better output logic operation than traditional semiconductor optical amplifier (SOA). Choosing suitable injection current, wavelength scope of the input signal and CW power can achieve better logic operation effect.

An Ultra-Low-Latency Guaranteed-Rate Internet for Cloud Services

An Enhanced-Internet network that provides ultra-low-latency guaranteed-rate (GR) communications for Cloud Services is proposed. The network supports two traffic classes, the Smooth and Best-Effort classes. Smooth traffic flows receive low-jitter GR service over virtual-circuit-switched (VCS) connections with negligible buffering and queueing delays, up to 100% link utilizations, deterministic end-to-end quality-of-service (QoS) guarantees, and improved energy efficiency. End-to-end delays are effectively reduced to the fiber time of flight. A new router scheduling problem called the Bounded Normalized-Jitter integer-programming problem is formulated. A fast polynomial-time approximate solution is presented, allowing TDM-based router schedules to be computed in microseconds. We establish that all admissible traffic demands in any packet-switched network can be simultaneously satisfied with GR-VCS connections, with minimal buffering. Each router can use two periodic TDM-based schedules to support GR-VCS connections, which are updated automatically when the router's traffic rate matrix changes. The design of a Silicon-Photonics all-optical packet switch with minimal buffering is presented. The Enhanced-Internet can: 1) reduce router buffer requirements by factors of ≥ 1000; 2) increase the Internet's aggregate capacity; 3) lower the Internet's capital and operating costs; and 4) lower greenhouse gas emissions through improved energy efficiency.

All-optical switching for 10-Gb/s packet data by using an ultralow-power optical bistability of photonic-crystal nanocavities.

An all-optical packet switching using bistable photonic crystal nanocavity memories was demonstrated for the first time. Nanocavity-waveguide coupling systems were configured for 1 × 1, 1 × 2, and 1 × 3 switches for 10-Gb/s optical packet, and they were all operated with an optical bias power of only a few μW. The power is several magnitudes lower than that of previously reported all-optical packet switches incorporating all-optical memories. A theoretical investigation indicated the optimum design for reducing the power consumption even further, and for realizing a higher data-rate capability and higher extinction. A small footprint and integrability are also features of our switches, which make them attractive for constructing an all-optical packet switching subsystem with a view to realizing optical routing on a chip.

Flexible 16 $\times$ 10-Gb/s All-Optical Broadcast and Multicast TWDM Passive Optical Network

To achieve flexible packet routing in a time wavelength-division multiplexing passive optical network (PON) architecture, most proposed systems use a tunable transceiver in the optical line terminal (OLT). The tunable transceiver is attractive for use in a PON system because it is able to broadcast and multicast packets within the entire PON system, being limited only to a single PON link. The proposed all-optical packet routing (AOPR) module was designed to incorporate a fixed-type wavelength OLT transmitter with a continuous-wave pump probe signal module. The design of the module is based on the ALL-ON method to support all broadcast signals, which replaces the wavelength tuning feature in the tunable OLT transmitter. The proposed architecture was designed using the multicasting cross-gain modulation (XGM) method. In this proposed design, the XGM function of the OLT system becomes a part of the AOPR OLT transmitter. The arrangement of this design aims to generate single or multiple wavelengths in a downstream direction in each OLT PON port. The measurement results revealed that the proposed system can handle a total of 160-Gb/s broadcast downstream bandwidth to serve 16 PON links using $16\lambda$ with a maximum of 2048 users.

Optical Packet Switching Architecture Using Wavelength Optical Crossbars

All-optical packet switching (OPS) is one of the promising technologies for the next generation of optical networks. It realizes the packet switching in optical domain that eliminates optical–electrical and electrical–optical conversions. One of the main components in an OPS network is the optical interconnect that provides the basic functionality of directing packets from input ports to the desired output ports, while maintaining data in the optical domain. Advances in all-optical technologies enable the wavelength exchanging phenomenon that can be used to develop new optical interconnect architectures. These architectures simultaneously combine the switching and the conversion domains. Thus, the use of the exchanging technology reduces the complexity without impacting the overall switching performance. In this paper, a new bufferless OPS interconnect by adopting wavelength optical crossbars that can combine both switching and wavelength conversion capabilities is proposed. The proposed architecture can operate in either of two modes: blocking or nonblocking. Our analysis to the proposed architecture confirms that, for the same number of input and output ports, a reduction in conversion and switching complexity can reached up to 50% and 99%, respectively, compared to traditional architectures.

A novel delay line buffering architecture for asynchronous optical packet switched networks

Optical buffering is one major challenge in realizing all-optical packet switching. In this paper we focus on a delay-line buffer architecture, named a Multiple-Input Single-Output (MISO) optical buffer, which is realized by cascaded fiber delay lines (FDLs). This architecture reduces the physical size of a buffer by up to an order of magnitude or more by allowing reuse of its delay line elements. We consider the MISO buffers in a network scenario where the incoming packets are asynchronous and of fixed length. A novel Markov model is developed to analyze the performance of our buffering scheme, in terms of packet loss ratio, average packet delay and the output link utilization. Both simulation and analytical results show that the length value of basic FDL element will significantly affect the performance of this buffer. This paper gives clear guidelines for designing optimal basic FDL lengths under different network scenarios. It is noticeable that this optimal length value is independent of the buffer sizes for specific traffic load and pattern.

All-Optical Packet Alignment Using Polarization Attraction Effect

We demonstrate submicrosecond polarization alignment of nonreturn to zero 10-Gbit/s optical packets using an all-optical polarization attraction effect in a low polarization-mode dispersion-shifted fiber. We experimentally demonstrate the alignment of optical packets having durations of 205 and 409 ns using a counter-propagating four-wave mixing process. To evaluate this technique, consecutive packets were aligned with distinctly different polarization states using a fiber interferometer. We experimentally demonstrate the recovery of optical packets that were lost due to their state of polarization (SOP) misalignment with the receiver. Polarization stability of the proposed system was assessed over a period of 30 min and it was observed that the scheme was able to correct the SOP and equalize the received optical power.

Delay Measurement and Split-Step Time-Domain Analysis of Ring Resonator All-Pass Filters

Single-ring all-pass filters with various coupling ratios are designed, fabricated, and characterized to assess the validity of the split-step time-domain modeling approach, which is considered for direct simulation of time-domain characteristics, such as optical delay, of various ring resonator devices. When the coupling ratio of the single-ring all-pass filter is 0.4 and 0.8, the delay time is measured to be about 145 and 42 ps respectively, which is comparable to the time-domain modeling results of 151 and 47 ps respectively. The measurements for two- and three-ring all-pass filters are also found to agree quite well with the simulation results. With these results it is confirmed that the split-step time-domain model could be efficiently incorporated into an optical-communication simulation module for ring resonator delay components in an all-optical packet switching system.

160-Gb/s Silicon All-Optical Packet Switch for Buffer-less Optical Burst Switching

We experimentally demonstrate a 160-Gb/s Ethernet packet switch using an 8.6-mm-long silicon nanowire for optical burst switching, based on cross phase modulation in silicon. One of the four packets at the bit rate of 160 Gb/s is switched by an optical control signal using a silicon based 1 × 1 all-optical packet switch. Error free performance (BER <; 1E-9) is achieved for the switched packet. The use of optical burst switching protocols could eliminate the need for optical buffering in silicon packet switch based optical burst switching, which might be desirable for high-speed interconnects within a short-reach and small-scale network, such as board-to-board interconnects, chip-to-chip interconnects, and on-chip interconnects.

Bufferless Routing in Optical Gaussian Macrochip Interconnect

The ever increasing intra-chip and inter-chip traffic load in computing systems has been pushing traditional electronic interconnects to their limit in communication bandwidth, latency, and energy consumption. In order to achieve the high bandwidth and low latency required by intra-chip and inter-chip communications and mitigate the high interconnect power dissipation, optical interconnects have been considered as a promising candidate for intra-chip and inter-chip interconnections in next generation computing systems. In addition, packet switching is an efficient switching paradigm to fully utilize the communication bandwidth. However, due to lack of random access optical memory, it is challenging to implement all-optical packet switching in optical interconnects. In this paper, we exploit bufferless routing, a special type of packet-switching, to overcome the problem of lack of random access optical buffer. More specifically, we study bufferless routing in a novel optical multichip system, called Gaussian macrochip, where embedded chips are interconnected by an optical Gaussian network. By taking advantage of the underlying Hamiltonian cycles in the Gaussian network, we design a bufferless routing algorithm for the Gaussian macrochip, which routes packets along the shortest path in the absence of deflection, and guarantees that deflected packets reach their destinations within ${{N}}$ hops. Our extensive simulation results demonstrate that by adopting the proposed routing algorithm, Gaussian macrochip can support much higher inter-chip communication bandwidth, has much shorter average packet delay, and is more power efficient than the previously proposed architectures for optical multichip systems.

Experimental analysis of an all-optical packet router

In this paper, we address the experimental implementation of an all-optical packet routing scheme, with contention resolution capability, using interconnected semiconductor optical amplifier (SOA)-based Mach- Zehnder interferometer (SOA-MZI) structures. Cross talk stemming from the blocked packets, due to the nonideal switching performed by the SOA-MZIs, is analyzed in every stage of the routing configuration. The routing functions and states performance are evaluated through bit-error ratio measurements and extinction ratio analysis.

Experimental Analysis of an All-Optical Packet Router

In this paper, we address the experimental implementation of an all-optical packet routing scheme, with contention resolution capability, using interconnected semiconductor optical amplifier (SOA)-based Mach- Zehnder interferometer (SOA-MZI) structures. Cross talk stemming from the blocked packets, due to the nonideal switching performed by the SOA-MZIs, is analyzed in every stage of the routing configuration. The routing functions and states performance are evaluated through bit-error ratio measurements and extinction ratio analysis.

Low-Latency Multicast Scheduling in All-Optical Interconnects

Optical interconnects are considered as a very appealing solution for future high speed interconnections in core networks and parallel computers. In this paper, we study multicast scheduling in all-optical packet interconnects/switches. We first propose a novel optical buffer called multicast-enabled fiber-delay-lines (M-FDLs), which can provide flexible delay for copies of multicast packets using only a small number of FDL segments. We then present a Low Latency Multicast Scheduling (LLMS) Algorithm that considers the schedule of each arriving packet for multiple time slots. We show that LLMS has several desirable features, such as a guaranteed delay upper bound and adaptivity to transmission requirements. To relax the time constraint of LLMS, we further propose a pipeline and parallel architecture for LLMS that distributes the scheduling task to multiple pipelined processing stages, with N processing modules in each stage, where N is the size of the interconnect. Finally, by implementing it with simple combination circuits, we show that each processing module can complete the packet scheduling for a time slot in O(1) time. The performance of LLMS is evaluated extensively against statistical traffic models and real Internet traffic traces, and the results show that the proposed LLMS algorithm can achieve superior performance in terms of average packet delay and packet drop ratio.

All Optical Packet Switches Based On Space Switch Array for the Transmission of Higher Data Rate Using NRZand RZ Modulation

The explosive growth of the Internet traffic requires the design of next generation switching systems accommodating huge data-centric traffic at the packet level. All-optical packet switching (OPS) with greater flexibility, granularity and switching capacity is able to meet the complexity of traffic. An all-optical fiber-optic switching device maintains the signal as light, from input to output. Semiconductor optical amplifiers (SOAs) are widely studied as nonlinear elements for high bit rate all-optical switching applications, such as wavelength conversion and regeneration. All optical switches incorporating SOAs have peculiarities like small size, low switching energy requirement and high non linearity. Here simulation of a 4 x 4 optical packet space switch array based on Optically Amplified Suppressed Interference Switches (OASIS) with different data rate has been performed. The OptiSystem version-12 simulator is used to model the structure, it is also used to assess the behavior and performance of this switch array. The simulation of 4x4 space switch array with different bit rate and for different modulation format is done which gives the BER within the acceptable range. Implications of cascadability of this switch array will be analysed which improves the quality and capacity of the existing networks

Wavelength Tuning Free Transceiver Module in OLT Downstream Multicasting4λ × 10 Gb/s TWDM-PON System

We propose a new architecture of dynamic time-wavelength division multiplexing-passive optical network (TWDM-PON) system that employs integrated all-optical packet routing (AOPR) module using4λ×10 Gbps downstream signal to support 20 km fiber transmission. This module has been designed to support high speed L2 aggregation and routing in the physical layer PON system by using multicasting cross-gain modulation (XGM) to route packet from any PON port to multiple PON links. Meanwhile, the fixed wavelength optical line terminal (OLT) transmitter with wavelength tuning free features has been designed to integrate with the semiconductor optical amplifier (SOA) and passive arrayed waveguide grating (AWG). By implementing hybrid multicasting and multiplexing, the system has been able to support a PON system with full flexibility function for managing highly efficient dynamic bandwidth allocation to support the4λ×10 Gb/s TWDM-PON system used to connect 4 different PON links using fixed wavelength OLT transceivers with maximum 38 dB link loss.

On the fly all-optical packet switching based on hybrid WDM/OCDMA labeling scheme

We introduce a novel design of an all-optical packet routing node that allows for the selection and forwarding of optical packets based on the routing information contained in hybrid wavelength division multiplexing/optical code division multiple access (WDM/OCDMA) labels. A stripping paradigm of optical code-label is adopted. The router is built around an optical-code gate that consists in an optical flip–flop controlled by two fiber Bragg grating correlators and is combined with a Mach–Zehnder interferometer (MZI)-based forwarding gate. We experimentally verify the proof-of-principle operation of the proposed self-routing node under NRZ and OCDMA packet traffic conditions. The successful switching of elastic NRZ payload at 40Gb/s controlled by DS-OCDMA coded labels and the forwarding operation of encoded data using EQC codes are presented. Proper auto-correlation functions are obtained with higher than 8.1dB contrast ratio, suitable to efficiently trigger the latching device with a contrast ratio of 11.6dB and switching times below 3.8ns. Error-free operation is achieved with 1.5dB penalty for 40Gb/s NRZ data and with 2.1dB penalty for DS-OCDMA packets. The scheme can further be applied to large-scale optical packet switching networks by exploiting efficient optical coders allocated at different WDM channels.