Showing papers by "Ciena published in 2010"

Method and apparatus for multicast implementation in a routed ethernet mesh network

Abstract: Interest in multicast group membership may be advertised via a routing system on an Ethernet network along with an indication of an algorithm to be used by the nodes on the network to calculate the distribution tree or trees for the multicast. Each node, upon receipt of the advertisement, will determine the algorithm that is to be used to produce the multicast tree and will use the algorithm to calculate whether it is on a path between nodes advertising common interest in the multicast. Example algorithms may include shortest path algorithms and spanning tree algorithms. This allows multicast membership to be managed via the routing control plane, while enabling spanning tree processes to be used to forward multicast traffic. Since spanning tree is able to install multicast state per service rather than per source per service, this reduces the amount of forwarding state required to implement multicasts on the routed Ethernet mesh network.

Packet and circuit network convergence with OpenFlow

Abstract: IP and Transport networks are controlled and operated independently today, leading to significant Capex and Opex inefficiencies for the providers. We discuss a unified approach with OpenFlow, and present a recent demonstration of a unified control plane for OpenFlow enabled IP/Ethernet and TDM switched networks.

100G and beyond with digital coherent signal processing

Abstract: The demand for increased bandwidth is ever present. Coherent technology coupled with advanced modulation formats and digital signal processing is a key enabler for optical communication systems at 100 Gb/s and beyond. This article reviews the attributes of coherent systems in light of the challenges faced by system designers to realize increased bit rates for next-generation optical systems.

Systems and methods of measuring latency and routing thereon in optical networks

Abstract: The present disclosure provides systems and methods for making latency measurements and using these measurements in routing in optical networks. In an exemplary embodiment, a method is defined whereby two nodes sharing a line automatically determine whether both nodes are capable of making a latency measurement and then which node will initiate and which node participates in making the latency measurement. In another exemplary embodiment, an on-demand latency measurement may be made between any two arbitrary nodes within a domain. Routing messages may be used to disseminate the latency of links via a signaling and routing protocol. Advantageously, the present invention provides measurement of latency and latency variation of customer circuits (i.e., SNCs) using an in-band, non-intrusive calculation with a high-degree of accuracy. Furthermore, the present invention may consider these calculations for circuit routing based on the latency and circuit acceptance based on maximum latency restrictions.

Ethernet network synchronization systems and methods

Abstract: The present disclosure relates to Ethernet synchronization systems and methods that combines Synchronous Ethernet (Sync-E) and Precision Time Protocol (PTP) IEEE 1588 algorithms. The present invention includes systems and methods for Ethernet networks and node configurations that include a set of rules on node placement, such as Boundary Clock (BC) nodes and Sync-E nodes, a clock selection algorithm, a holdover algorithm, and the like. Advantageously, the present invention provides an architecture that allows practical and real-world useful clock propagation through placement of BCs and Sync-E nodes for best performance. Practical experience and theoretical design are embodied in the present invention to define a very specific set of rules on how to build a network capable of providing accurate and reliable synchronization. The present invention includes clock selection that unifies Sync-E and 1588 algorithms.

Optical packet buffers for backbone internet routers

Abstract: If optical routers are to become reality, we will need several new optical technologies, one of which is to build sufficiently large optical buffers. Building optical buffers for routers is daunting: Today's electronic routers often holdmillions of packets, which is well beyond the capabilities of optical technology. In this paper, we argue that two new results offer a solution. First, we show that the size of buffers in backbone routers can be made very small--just about 20 packets per linecard--at the expense of a small loss in throughput. Second, we show that integrated delay line optical buffers can store a few dozen packets on a photonic chip. With the combination of these two results, we conclude that future Internet routers could use optical buffers.

High-speed optical transponder systems

Abstract: The present disclosure provides high-speed wavelength division multiplexing (WDM) transponders (e.g., 10 Gb/s, 40 Gb/s, 100 Gb/s, and beyond) that receive one or more optical signals and convert and/or remodulate the received optical signals onto a newly generated optical channel along with overhead processing/addition, forward error correction, and the like. In general, the transponders of the present invention include a client-side and a line-side, each with bi-directional optical transmission. The transponders provide an effective mechanism to support WDM networks that are transparent to the client-side.

Control system for a polar optical transmitter

Abstract: A method of controlling a polar optical transmitter comprising a dual-branch Mach-Zehnder (MZ) modulator driven by a pair of independent electrical drive signals. A cost function is provided which defines a relationship between a control parameter of the optical transmitter and a power level of an output optical signal generated by the MZ modulator. A selected component of the electrical drive signals is dithered using a predetermined dither signal. A modulation depth of the output optical signal power level corresponding to the dither signal is detected, and the control parameter adjusted based on the cost function and the detection result.

System and method for switching packet traffic over an optical transport network

Abstract: A system and method for switching packet traffic over an optical transport network comprises a network element having first and second mappers for mapping packet traffic to electrical streams. A network interface includes a packet switch that directs a first packet stream to the first mapper based on a destination of the packets in the first packet stream and a second packet stream to the second mapper based on a destination of the packets in the second packet stream. The first mapper produces a first stream of electrical signals from the first packet stream, and the second mapper produces a second stream of electrical signals from the second packet stream. Each electrical signal stream is allocated a portion of bandwidth of an optical interface. The optical interface produces an optical signal that includes the first and second electrical signal streams according to the bandwidth allocated to each electrical signal stream.

Optimized directionless optical add/drop module systems and methods

Abstract: The present disclosure provides optimized configurations for a directionless reconfigurable optical add/drop multiplexer application. The present invention includes an add module with improved optical signal-to-noise through placing amplifiers prior to a multi-cast optical switch. The present invention includes various drop module configurations utilizing distributed gain, channel selective filters, and bi-directional configurations to reduce power consumption and complexity. Additionally, the present invention includes an integrated broadcast and select architecture.

In-band signaling for point-multipoint packet protection switching

Abstract: A method and system provide in-band protection switch signaling in a communication system arranged as a point-to-multipoint tree. The point-to-multipoint tree includes a root node communicatively coupled to a plurality of leaf nodes through both a working link and a protection link. Data is transferred through a current link of the point-to-multipoint tree. The current link is either the working link or the protection link. A fault is detected in the current link in the point-to-multipoint tree. Each leaf node in the point-to-multipoint tree is notified of the fault using the current link. Upon receiving the notification, the root node and each leaf node switch to the other link of the working link and the protection link.

High density switching platform with interbay connections arrangement

Abstract: A high density switching platform arranges multiple circuit cards interconnected by a single backplane. A single backplane has three sets of circuit cards on one side. A shared ventilation chamber on the other side of the backplane draws ambient air through each of the three sets of circuit cards independently. The air flow also allows cooling of power modules that supply power to the circuit cards. The platform allows interconnection of its circuit cards with circuit cards in adjacent platforms.

Detection of a Single 40 Gb/s Polarization-Multiplexed QPSK Channel With a Real-Time Intradyne Receiver in the Presence of Multiple Coincident WDM Channels

Abstract: We have characterized the performance of a single-ended intradyne receiver when multiple wavelength-division multiplexed (WDM) channels are incident. Detection of a single 40 Gb/s dual-polarization QPSK channel is achieved within a band of up to 17 WDM channels using a receiver with real-time digital signal processing and without optical demultiplexing. Measurements are presented of the performance in a back-to-back configuration as well as after transmission over 400 km of standard single-mode fiber. The dependence of the coincident channels' interference on various parameters, such as the net chromatic dispersion and the orientation of the coincident channels' polarization tributaries relative to the receiver polarizer, is explored. We also investigate using a single interfering channel with its power appropriately scaled to represent multiple interfering channels as an alternative configuration for evaluating receiver performance. The single-interferer approach has significant disadvantages including increased polarization sensitivity and different scaling of the interference term arising from the channel-channel beating compared to true multi-channel interference.

Design of Polarization De-Multiplexer and PMD Compensator for 112 Gb/s Direct-Detect PDM RZ-DQPSK Systems

Abstract: The design of a polarization de-multiplexer and a polarization mode dispersion compensator (PMDC) for direct-detect polarization division multiplexed (PDM) return-to-zero differential quadrature phase shift keying (RZ-DQPSK) systems are studied in detail. The impact of polarization dependent loss is studied in polarization de-multiplexers with different error detection configurations for both bit-aligned and bit-interleaved PDM systems. The level of the clock frequency of the combined pulse train of the two polarizations is proposed as the error signal for the PMDC. It enables the PMDC to work in the cancellation mode. Two separate control loops are proposed for the polarization de-multiplexer and the PMDC to allow them to work independently. The DGD tolerances for the one-stage and two-stage PMDC are measured and discussed. Finally the glitch problem in the polarization tuning algorithm is studied. An advanced dithering algorithm and the corresponding architecture of the polarization controller are proposed to solve the glitch problem.

Optical network in-band control plane signaling, virtualized channels, and tandem connection monitoring systems and methods

Abstract: The present disclosure provides improvements with respect to in-band control plane signaling, virtualized channels, and tandem connection monitoring in optical networks utilizing Synchronous Optical Network (SONET), Synchronous Digital Hierarchy (SDH), Optical Transport Network (OTN), and the like In an exemplary embodiment, the present disclosure includes an optical network operating a control plane with in-band signaling utilizing SONET/SDH path level overhead In another exemplary embodiment, the present disclosure includes an optical network operating virtualized SONET/SDH or OTN channels with manually cross-connections at intermediate line terminating elements In yet another exemplary embodiment, the present disclosure includes a tandem connection monitoring selection method across multiple operator domains

SPM-Tolerant Pulse Shaping for 40- and 100-Gb/s Dual-Polarization QPSK Systems

Abstract: An intersymbol-interference-free pulse shape is specifically designed for self-phase-modulation (SPM) mitigation. It is experimentally shown to increase the SPM tolerance of a 40-Gb/s single-channel postcompensated dual-polarization quadrature phase-shift keying system by 1.5 dB. Numerical analyses at 40 and 100 Gb/s indicate that the specialized pulse shape can increase the maximum reach for G.652 fiber and G.655 fiber up to 1190 and 820 km, respectively.

Development of the first IEEE 1588 telecom profile to address mobile backhaul needs

Abstract: This article describes the work performed by ITU-T SG15Q13 for defining the first telecom profile based on the use of IEEE Std 1588-2008. The first profile is specifically developed for the distribution of frequency using unicast IPv4 transmission, and required adaptation of the IEEE1588 protocol to make it suitable for the telecom environment. The objectives, reasons, and results of this adaptation are explained in this article. Since the distribution of phase/time is also gaining importance in telecom, the article briefly discusses the objectives, reasons, and upcoming work for the definition of another profile that will leverage other functions and clocks defined in IEEE1588.

Mesh restoration in optical transport networks

Abstract: The present disclosure provides mesh restoration systems and methods with Optical Transport Network (OTN) links using a signaling and routing protocol, such as Optical Signaling and Routing Protocol (OSRP), Automatically Switched Optical Network (ASON), Generalized Multi Protocol Label Switching (GMPLS), and the like. The present invention includes an optical node, network, and method using the signaling and routing protocol for OTN lines of differing bandwidth granularities. The present invention utilizes OTN overhead for in-band signaling and may include capability for supporting SONET/SDH lines as well as OTN lines in the same system using the signaling and routing protocol.

Method and apparatus for traffic engineering in shortest path bridged networks

Abstract: A method and apparatus for diverting traffic in a communications network are disclosed. According to one aspect, the invention provides a communications network with a first node and a second node. Connecting these two nodes is a first set of intermediate nodes on a first path (the true shortest path) and a second set of intermediate nodes on a second alternate path. At a first node, a first processor determines whether a packet arriving at the first node must transit the second node. If so, the base virtual local area network (VLAN) identifier (VID) of the packet is replaced by a first VID, and the packet is transmitted along the second path through the second set of intermediate nodes to the second node. At the second node, a second processor determines whether a packet arriving at the second node must transit the first node. If so, the base VID of the packet is replaced by a second VID different from the first VID and different from the base VID, and the packet is transmitted along the second path through the second set of intermediate nodes to the first node.

Proliferation of the optical transport network: a use case based study

Abstract: The ITU-T G.709 standard is perhaps the most underrated and yet widely used of all telecommunication standards, especially pertaining to the transport layer. In this article we focus on OTN as a delivery platform for emerging services. We will understand why OTN was originally proposed and how it can be a critical enabler for emerging services. To this end, we build use cases of OTN especially for Ethernet transport, mobile backhaul, IP router interconnection, sub-wavelength support, and support of overlaid services, especially across multiple domains. The use cases will bring to the fore key advantages of OTN and how this technology solution is ideal for emerging applications. We also discuss future movements in this technology and how these can affect the transport network.

E-spring (g.8032) interworking to provide access protection

Abstract: A method of enabling a resilient interface between a first node and a G.8032 Ethernet ring. A Link Aggregation Group (LAG) comprising respective links is provided between the first node and at least two ring nodes of the Ethernet ring. An aggregation function is instantiated at the first node, for distributing subscriber traffic to the links of the LAG in a conventional manner. A first one of the ring nodes is designated as Active, and each of the other ones of the ring nodes are designated as Inactive. At each Inactive ring node, a logical block is imposed on its respective link of the LAG, such that subscriber traffic between the first node and the Ethernet ring is routed by the aggregation function only through the respective link between the first node and the Active ring node.

Timing recovery in presence of optical impairments and optimization of equalization based on timing recovery moment strengths

Abstract: The present disclosure provides timing recovery in optical systems in the presence of chromatic dispersion (CD), polarization mode dispersion (PMD), and polarization dependent loss (PDL) and to optimization of equalization settings based upon timing recovery moment strengths. A stable timing point may be determined in the presence of PMD and PDL impairments, even when the direct estimate of timing becomes unreliable. This determination may be performed entirely in the digital domain providing precise, predictable performance. Also, the present invention utilizes a monotonic relationship between the timing metric and CD setting error to provide directed search in setting the CD equalizer thereby reducing significantly the overall search effort in optimizing CD equalizer settings. This utilizes computations already performed by the transceiver for timing recovery function yielding a computational advantage over competing methods.

Fabric extra traffic

Abstract: A method of forwarding traffic through a network node including an ingress IO card, an egress IO card, and a pair of parallel switch fabric cards. One of the switch fabric cards is designated as a working switch fabric card, and the other one of the switch fabric cards is designated as a protection switch fabric card. In the ingress IO card, the traffic flow is divided into a committed information rate (CIR) component and an extra information rate (EIR) signal. Under a normal operating condition of the node, the ingress IO card forwards the CIR traffic component through the working switch fabric card, and forwards the EIR traffic component through the protection switch fabric card. Upon detection of a failure impacting the working switch fabric card, the ingress IO card drops the EIR traffic component and forwards the CIR traffic component through the protection switch fabric card.

Card guide and heatsink assemblies for pluggable electro-optic modules

Abstract: In various exemplary embodiments, the present invention provides improved card guide and heatsink assemblies for pluggable electro-optic modules utilized in optical communications networks and the like. More specifically, the present invention provides a solderable surface-mounted card guide assembly and a staggered heatsink assembly. These assemblies are utilized with small-form factor pluggable electro-optic modules and the like, and the concepts presented herein can be extended to XFP, XENPAK, XPAK, and X2 electro-optic modules, for example. The solderable surface-mounted card guide assembly of the present invention finds particular applicability with small-form factor pluggable electro-optic modules not utilizing any type of module cage, while the staggered heatsink assembly of the present invention finds particular applicability with small-form factor pluggable electro-optic modules both not utilizing and utilizing any type of module cage.

Optical network real time latency measurement systems and methods

Abstract: The present disclosure provides systems and methods for real-time, in-service latency measurements over optical links that may be further integrated within various optical control planes. The present invention may utilize minimal unused overhead to calculate latency of an optical line through a transport network. The present invention utilizes timers at two end-point nodes associated with the optical line, and includes a mechanism to filter out frame skew between the nodes. Advantageously, the present invention provides a highly accurate latency measurement that may calculate latency on links as small as one meter, an in-service algorithm operable without network impact, and may be integrated with an optical control plane to automatically provide administrative weight variables associated with link costs.

Method and system for optical network smart timer management via delay measurement between spans

Abstract: A method and system for determining timers in an High Level Data Link Control (HDLC) Traffic Manager (HTM) state machine are disclosed. According to one aspect, the invention provides for determining a transit delay between two nodes by sending a first packet having a delay measurement byte to a second node that is on a link between the first node and the second node. The method also includes receiving a second packet with the delay measurement byte from the second node. The delay measurement byte sent by the second node is adjusted by the second node to indicate its receipt by the second node. A measured delay value is determined. The measured delay value is the delay between a time of sending the first packet to the second node and receiving the second packet from the second node. The measured delay value is determined by the hardware of the first node. Upon determining the measured delay value, timer values of the HTM state machine are set based on the measured delay value.

Electronic precompensation of the nonlinear distortion in a 10 Gb/s 4-ary ASK directly modulated laser

Abstract: The nonlinear distortion resulting from the direct modulation of a semiconductor laser using 4-ary amplitude shift keying at 10 Gb/s is mitigated by precompensation based on the use of digital signal processing to generate an appropriate modulating current.

Physical layer validation of Filterless optical networks

Abstract: A simple analytical model is proposed for validating the physical layer of Filterless optical networks based on advanced transmission technologies. Results obtained with a prototype tool developed in MATLAB environment and validated using VPItransmissionMaker™ are presented.

Single pin coherent receiver

Abstract: In a coherent optical receiver of an optical communications system, methods and systems for receiving a data signal x(t) modulated on an optical signal. A linearly polarized LO light is generated, which has a frequency of f 1 =f 0 ±Δf, where f 0 is a frequency of a narrowband carrier of the optical signal, and Δf corresponds with a band-width f B of the data signal x(t). The LO light and a received light of the optical signal are heterodyned on a photodetector. An analog signal generated by the photodetector is low-pass filtered to generate a filtered signal, using a filter characteristic having a sharp cut-off at a frequency of Δf+nf B , where n is an integer multiple. An analog-to digital (A/D) converter samples the filtered signal at a sample rate of 2(Δf+nf B ) to generate a corresponding multi-bit digital sample stream. The multi-bit digital sample stream is digitally processed to recover respective In-Phase and Quadrature components of the received light of the optical signal.

Multi-core, multi-blade, and multi-node network environment simulation

Abstract: The present disclosure provides systems and methods for a simulation environment that simulates hardware at a fiber level, a data plane level, a card level, and a chassis level The simulation environment may be utilized in development and testing of complex, real time, embedded software systems, such as, for example, routers, switches, access devices, base stations, optical switches, optical add/drop multiplexers, Ethernet switches, and the like In an exemplary embodiment, the simulation environment operates on one or more workstations utilizing a virtual machine to operate a virtualized module, line card, line blade, etc Further, a plurality of virtual machines may operate together to operate a virtualized chassis forming a network element and with a plurality of virtualized chassis forming a network Advantageously, the present invention provides state of the art data plane traffic and control plane simulation that reduces development time and cost while increasing design flexibility