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Flexibility and Fragmentation Aware Routing, Core and Spectrum Allocation for Hybrid AoD Nodes in SDM-EONs

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Abstract

Space division multiplexing elastic optical network (SDM-EON) enables high-capacity transmission, in which the network nodes should provide high switching flexibility while limiting the complexity and costs of nodes. Architecture on demand (AoD) nodes can meet these requirements but the slow configuration time of optical backplane in AoD nodes makes it difficult to serve latency-sensitive requests. In this paper, we propose a hybrid optical backplane based on micro-electromechanical systems (MEMS) and semiconductor optical amplifier (SOA) switches to provide fast configuration time for AoD nodes. Moreover, we propose quantitative measures of node switching flexibility in SDM-EONs and of link configuration speed in AoD nodes. Based on the hybrid backplane architecture and the measurement approaches, we propose a flexibility and fragmentation aware routing, spectrum and core allocation algorithm and an AoD synthesis algorithm. Simulation results show that the hybrid AoD nodes with support of spatial lane change can reduce network blocking probability. The AoD based on this hybrid backplane structure can improve the network performance by 32.8% compared to the AoD based on the traditional MEMS. Compared with traditional reconfigurable optical add/drop multiplexers (ROADMs), the hybrid AoD nodes can control the number of wavelength selective switch (WSS) ports.

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The quality-of-transmission (QoT) degradation due to the dispersion effect in longer lightpaths is higher than that of shorter lightpaths in a dispersion uncompensated network. To overcome this shortcoming, this letter proposes a dispersion-adaptive first-last fit spectrum allocation scheme for elastic optical networks to decrease the call blocking in the network. The proposed scheme assigns longer lightpath requests from the smallest indexed spectrum slot, where the dispersion effect is less, and shorter lightpath requests from the largest indexed spectrum slot, where the dispersion effect is more. As a result, a less robust modulation technique is used to maintain the QoT threshold level for the longer lightpath requests, and hence a lower number of spectrum slots are required for lightpath establishment. Simulation results show that the proposed scheme outperforms the conventional scheme in terms of blocking probability and contiguous aligned available slot ratio.
Article
We demonstrate full flex-grid operation with Nyquist frequency division multiplexing. The technique supports high spectral efficiency, asynchronous operation of channels, variable channel loading with different modulation formats and dynamic bandwidth allocation. Data from different sources with different bit and symbol rates are encoded onto electrical Nyquist pulses with different electrical subcarrier frequencies, and then transmitted optically. We give details on the transceiver design with digital signal processing and investigate the implementation penalty as a function of several design parameters such as limited filter length and effective number of bits. Finally, experiments are performed for receivers with direct detection, intradyne and remote heterodyne reception.
Article
This paper investigates the spectrum fragmentation issue, which undermines the bandwidth efficiency in elastic optical networks. After categorizing the two-dimensional fragmentation problem as the fragmentation and misalignment subproblems, this paper proposes joint routing and spectrum assignment (RSA) algorithms to alleviate the spectral fragmentation in the lightpath provisioning process. The time complexity of the two proposed algorithms are analyzed in detail, and both algorithms can run in 0(kdnC log C) time, where k is the number of the shortest path in the routing algorithm, d is the maximum node degree in the network, n is the number of nodes in the network, and C is the link capacity expressed as the number of spectral slots. Simulation results indicate that the proposed fragmentation-aware (FA) RSA algorithm and the FA algorithm with congestion avoidance (CA) outperform the existing schemes in terms of blocking probability (BP) reduction. Compared with the benchmark K-shortest-path routing and first-fit assignment (KSP-FF) algorithm, the proposed FA and FA-CA algorithms can achieve a BP reduction of [100%, 4.43%] and [100%, 6.45%], respectively, according to the traffic load in a sample NSFNET topology.
Conference Paper
How serious is spectrum fragmentation in an elastic optical network? It is addressed by the tremendous provisioning gain achieved by eliminating a particular kind of fragmentation, namely, one that could be removed by Hitless Optical Path Shift (HOPS), a non-disruptive defragmentation technology. We devised a series of HOPS-based defragmentation algorithms, ranging from proactive to reactive strategies. Analysis and simulation results show that for typical backbone networks operated with a light load, using our optimal reactive defragmentation scheme, 98% of the requested spectrum bandwidth, that is otherwise blocked, can be provisioned. Moreover, the corresponding defragmentation costs (in terms of impact on existing connections, and defragmentation delay) are kept at minimum.
Article
This paper reviews advances in the technology of integrated semiconductor optical amplifier based photonic switch fabrics, with particular emphasis on their suitability for high performance network switches for use within a datacenter. The key requirements for large port count optical switch fabrics are addressed noting the need for switches with substantial port counts. The design options for a 16£ 16 port photonic switch fabric architecture are discussed and the choice of a Clos-tree design is described. The control strategy, based on arbitration and scheduling, for an integrated switch fabric is explained. The detailed design and fabrication of the switch is followed by experimental characterization, showing net optical gain and operation at 10 Gb/s with bit error rates lower than 10 ¡9 . Finally improvements to the switch are suggested, which should result in 100 Gb/s per port operation at energy efficiencies of 3 pJ/bit.
Article
A scalable photonic interconnection network architecture is proposed whereby a Clos network is populated with broadcast-and-select stages. This enables the efficient exploitation of an emerging class of photonic integrated switch fabric. A low distortion space switch technology based on recently demonstrated quantum-dot semiconductor optical amplifier technology, which can be operated uncooled, is used as the base switch element. The viability of these switches in cascaded networks is reviewed, and predictions are made through detailed physical layer simulation to explore the potential for larger-scale network connectivity. Optical signal degradation is estimated as a function of data capacity and network size. Power efficiency and physical layer complexity are addressed for high end-to-end bandwidth, nanosecond-reconfigurable switch fabrics, to highlight the potential for scaling to several tens of connections. The proposed architecture is envisaged to facilitate high-capacity, low-latency switching suited to computing systems, backplanes, and data networks. Broadband operation through wavelength division multiplexing is studied to identify practical interconnection networks scalable to 100 Gbits/s per path and a power consumption of the order of 20 mW/(Gbits/s) for a 64×64 size interconnection network.
Article
Bell System Technical Journal, also pp. 623-656 (October)
Article
We present what is to our knowledge the first active-passive monolithically integrated 16×16 switch. The active InP/InGaAsP elements provide semiconductor optical amplifier gates in a multistage rearrangeably nonblocking switch design. Thirty-two representative connections, including the shortest, longest, and comprehensive range of intermediate paths have been assessed across the switch circuit. The 10  Gb/s signal routing is demonstrated with an optical signal-to-noise ratio up to 28.3  dB/0.1  nm and a signal extinction ratio exceeding 50 dB.
Article
A monolithic 8:1 SOA gate switch that integrates an 8-ch SOA gate array, an 8:1 optical coupler, and a 1-ch SOA gate was developed for use in a large scale optical packet switching system. A 250-mum-long compact field-flattened coupler (FFC) produces a very small channel-imbalance together with a compact total chip size of 3.0 times 1.0 mm. The device exhibited a large ON-state gain of >14.3 dB and a small total gain deviation of 3.0 dB. The optimized passive waveguide structure successfully suppressed the stray light, which resulted in a record-high ON-OFF extinction ratio of >70 dB. We used a thin tensile-strained multi-quantum well (MQW) active layer which can attain high-saturation output power, low noise, and polarization insensitivity for SOA gates. Due to the coexistence of a high saturation output power and a low noise figure, the device exhibited a very wide input power dynamic range of 20.5 dB for a 10-Gb/s NRZ signal.
Article
We report for the first time a successful operation of a 4/spl times/4 optical switch. A novel structure is utilized to achieve lossless and extremely low crosstalk characteristics. Sixteen of carrier-injection type optical single-slip-structure (S/sup 3/) switch with traveling-wave amplifier (COSTA) are monolithically integrated in 4/spl times/4 crossbar configuration on an InP substrate. A fiber-to-fiber gain of 5 dB and an on/off ratio of 54 dB have been demonstrated using this structure. We believe this switch structure has a potential to be employed in a large scale photonic switching system where low loss and low crosstalk are critical requirements.< >