Osamu Matsuda

Study on wavelength cross-connect realized with wavelength selective switches

A novel structure for wavelength cross-connect (WXC) is proposed using the wavelength selective switch (WSS) devices. A 4/spl times/4 WXC node is realized and tested. The key technologies for the WSS based WXC node are also discussed.

Optical tunable asymmetric interleaver

A novel optical tunable asymmetric interleaver is demonstrated. It consists of two symmetric interleaves with wavelength shifting capability in series. It can deliver continuous tunable interleaving ratios for WDM applications, particularly for 10 G+40 G network upgrade.

Wavelength-shift-keying (WSK) encoded pulses for optical labeling applications

Optical label switching (OLS) is an important approach for building future all-optical networks. In OLS systems, the label and payload can be encoded on the same optical carrier through orthogonal modulation schemes. We demonstrate the generation of wavelength-shift-keying (WSK) encoded optical pulses using spectral processing techniques and their applications in optical labeling systems. We show that the extinction ratio impairment issue for WSK-labeled intensity-modulated optical systems can be solved by using pulse position modulation (PPM) for the payload data, because PPM can guarantee equalized pulse energy in each of the bit period. In our optical labeling experiments with 622 Mb/s label and 9.95-Gb/s payload, the power penalty for the optical WSK label is reduced from 17.5 to 1.6 dB at the bit-error rate of 10/sup -9/ when the payload modulation format is changed from intensity modulation to PPM.

Testbed for ROADM and WXC based metro WDM networks

A testbed for metro wavelength division multiplexing (WDM) network is realized and tested. The testbed contains a reconfigurable optical add/drop multiplexer (ROADM) node, a 2x2 wavelength cross-connect (WXC) node, and two interconnected two-fiber bidirectional path protected switching ring networks (TF-BPSR). Both the ROADM and WXC node are bidirectional nodes, so they can select channels from the working and the protection ring networks simultaneously, and they support both protected and unprotected services. The ROADM node uses a flexible band tunable filter (FBTF) to drop a waveband from the input WDM signals and send the express channels directly to the output port. As a result, the physical impairment accumulated on the express channels can be minimized. It also has a modular structure, so additional modules can be cascaded to expand the capacity and functionality of the node without any interruption to current services. The WXC node is realized with interconnected ROADM modules that are comprised of wavelength selective switches (WSSes). Arbitrary wavelength or wavelength sets can be either dropped in the node or cross-connected in a non-blocking manner. Multiple services, such as OC-48 and OC-192 SONET signals, gigabit Ethernet streams carrying interactive movie signals, and live video broadcasting services, are carried in the network, dropped in the ROADM and WXC node, and switched between the two ring networks. The testbed is controlled by a websever based network management system that facilitates remote control and monitoring. Experiments demonstrate that the performance of the nodes and the testbed meets the requirement of the services.

State-Based Algorithm for Power Stability Control in Transparent WDM Networks

This paper analyzes power fluctuation caused by interaction of fiber cut, add/drop operation, EDFA transients and ROADM attenuation adjustment in WDM networks. A state-based power control algorithm is proposed and tested in our simulation system.

Centralized Resource Management in WSS-Based Wavelength Cross-Connect Nodes

We analyze the applications of centralized resource management for transponder sharing and repeater assignment in wavelength selective switch based wavelength cross-connect nodes. We also propose a novel solution to realize centralized resource management.

Low crosstalk demodulators for 42.8 Gb/s WDM DPSK

A new type of optical demodulator is proposed to reduce the channel crosstalk in dense WDM DPSK systems. It can relieve the strong filtering condition required by transmitting 42.8 Gb/s signals over 50 GHz ITU grids.

Inter-symbol interference comparison for wavelength and waveband switching in all-optical optical cross-connect nodes

Inter-symbol interference caused by filtering effect in the all-optical optical cross-connect (OXC) will lead to degradation of optical signal. We investigate the effect of 40 Gb/s data ISI in the OXC nodes with different modulation formats and various parameters including channel spacing, OXC cascading, and passband profile. We show that waveband switching OXC causes less ISI effect to the signals.

Waveband Deaggregator Cascading Effect in Multi-granularity Optical Cross-connect Nodes

The cascaded filtering effect in multi-granularity optical cross-connect (OXC) nodes is studied. We perform simulation and conduct 40 Gb/s transmission experiment on waveband deaggregator-based hierarchical OXC node. The results show that wavebands experience less cascading effect than individual wavelengths

A Si bipolar 1.4-GHz time space switch LSI for B-ISDN

A 155-MB/s 32*32 Si bipolar switch LSI designed for wide application in the broadband ISDN was implemented. The operating speed is 1.4 GHz using an A-BSA Si bipolar process. Its throughput is 5.0 Gb/s by handling four 1.4-GHz interfaces, each of which supports an eight-channel multiplexed data stream. To realize a highly integrated high-speed bipolar LSI, power consumption and chip area should be reduced. Two technologies were developed for the LSI: (1) an active pull-down circuit with an embedded bias circuit in each gate, and (2) a modified standard cell with overlapped cell-channel structure. Using these technologies, total power consumption and chip area were reduced to 60% and 70%, respectively, of what is expected when conventional emitter-coupled logic (ECL) technologies and standard cell structures are used. The LSI evaluation results show that the developed LSI has sufficient performance to realize a large-scale B-ISDN switching system. >