NEC

About: NEC is a company organization based out in Tokyo, Japan. It is known for research contribution in the topics: Signal & Layer (electronics). The organization has 33269 authors who have published 57670 publications receiving 835952 citations. The organization is also known as: NEC Corporation & NEC Electronics Corporation.

Routing system capable of effectively processing routing information

Abstract: In a routing system having a plurality of external input ports and a plurality of external output ports, a switch network having a plurality of internal input ports and a plurality of internal output ports, an input section between the external input ports and the internal input ports, an output section between the internal output ports and the external output ports, and a control section connected to the switch network and the input section, an input port number which may be assigned to each of the external input ports is arranged in a routing information field of a transmission path signal by an input port number setter included in the input section. The input port number is memorized in a discarded cell memory of the control section together with an internal output port number which is assigned to the internal output ports and which is derived from a routing table along with a header. On occurrence of a discarded cell, the cause of discard can be analyzed by the use of the input port number and the header. When a plurality of external input cells are multiplexed into a multiplexed input cell sequence, the input port number may be replaced by the internal output port number in the control section to effectively utilize the routing information field.

Field and lab experimental demonstration of nonlinear impairment compensation using neural networks

Abstract: Fiber nonlinearity is one of the major limitations to the achievable capacity in long distance fiber optic transmission systems. Nonlinear impairments are determined by the signal pattern and the transmission system parameters. Deterministic algorithms based on approximating the nonlinear Schrodinger equation through digital back propagation, or a single step approach based on perturbation methods have been demonstrated, however, their implementation demands excessive signal processing resources, and accurate knowledge of the transmission system. A completely different approach uses machine learning algorithms to learn from the received data itself to figure out the nonlinear impairment. In this work, a single-step, system agnostic nonlinearity compensation algorithm based on a neural network is proposed to pre-distort symbols at transmitter side to demonstrate ~0.6 dB Q improvement after 2800 km standard single-mode fiber transmission using 32 Gbaud signal. Without prior knowledge of the transmission system, the neural network tensor weights are constructed from training data thanks to the intra-channel cross-phase modulation and intra-channel four-wave mixing triplets used as input features. Long-distance fiber communications still face many fundamental challenges in capacity due to nonlinearities. The authors develop a neural-network based tool to compensate nonlinearities, without prior knowledge of the transmission link, with low complexity.

Broadcast verification system, broadcast verification method, broadcast verification apparatus and storage medium storing broadcast verification program

Abstract: A broadcast verification system is provided which enables broadcast verification to be performed by a third party being independent of a broadcasting station, without being assisted by another, at low costs and to be reported to a client. The client submits CM (Commercial Message) images to the broadcasting station and registers feature descriptors in a database. When the broadcasting station broadcasts the CM images in accordance with a contract, a receiving device in a checking base extracts contents from received broadcasting waves and a checking section compares feature descriptors of the contents with that of contents stored in the database. When there is coincidence between them, the checking section transmits comparison results to an aggregating section which creates a report including broadcast time, broadcasting channel, broadcasting state and submits it to the client. A broadcast verifying agent receives a broadcast verification entrusting fee.

Microoptic grating multiplexers and optical isolators for fiber-optic communications

Abstract: As new optical devices for increasing further the utility of and to expand the application of fiber-optic communications, grating multiplexers and isolators have been developed for 0.8 μm band employing microoptic approach. The development of these devices is the subject of this paper. The devices have desirable features of small size, compactness, high optical performances, and high reliability. The grating multiplexer consists of a graded-index rod, a blazed reflection grating replicated onto the graded-index rod slanting facet or a wedge facet, and an input-output fiber array. Simple calculations have been done to determine necessary element parameters for a given channel spacing. Experimental results are presented for five-channel multiplexers devised using a SELFOC®lens. Around 3 dB insertion loss and less than -30 dB crosstalk have been obtained for about 35 nm channel spacing in overall device size of 18 \times 13 \times 50 mm. Faraday rotation optical isolators for 0.8 μm band have been miniaturized by employing an efficient paramagnetic glass Faraday rotator, a magnet with a through hole and a folded optics in the Faraday rotator. The path number in the folded optics has been optimized in terms of trading-off between the magnet size and the insertion loss. A 0.9 dB insertion loss including fiber coupling loss and 36 dB isolation have been obtained in overall device size of 24 \times 24.5 \times 42 mm. Results on the temperature and wavelength dependence of the isolation are also presented. In addition, fundamental properties of optical circulators for 0.8 μm band and optical isolators and circulators both for 1.3 μm band, developed as extended modifications of the optical isolators for 0.8 μm band, are briefly described.

1.25 Gbps wireless Gigabit ethernet link at 60 GHz-band

Abstract: A 1.25 Gbps 60 GHz-band full duplex wireless Gigabit Ethernet link has been developed. Direct ASK modulation and demodulation scheme is adopted for the 60 GHz-band transceiver. CPW MMIC's and planar filters are flip-chip mounted in TX and RX LTCC MCM's. The wireless Gigabit Ethernet link has the function of converting an optical fiber link to a wireless link seamlessly combining a 60 GHz-band transceiver with a 1000Base-SX optical in/out module. The size is 159/spl times/97/spl times/44 mm/sup 3/.