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All-optical wavelength conversion, using four-wave mixing in highly nonlinear fiber for different wavelengths at GHz resolution, was experimentally investigated with two-stage-comb-generated pump light for 10 Gbaud RZ-QPSK signals. The pump light was generated using a mode-locked fiber laser followed by a LiNbO3 phase modulator, or by using a tunable laser followed by two-stage LiNbO3 phase modulators (LN-PMs). The performance of the generated pumps was compared with the electrical spectrum, and eye patterns of the wavelength converted signals. It is confirmed that the quality of the generated pump light could be evaluated from the measured power spectrum within the GHz frequency range, and that the suppression of the noise level of the pump light affects the time waveform of the idler signal. In our experiments, clear eye openings could be obtained in case of the pump generation scheme using two-stage phase modulators. The pump lights with frequency shifts from the original continuous waveform light carrier of −10 GHz at the 1st-LN-PM, ±5 GHz at the 2nd-LN-PM, +10 GHz at the 1st-LN-PM, and −5 GHz at the 2nd-LN-PM were generated, and a frequency difference of the pump of less than the resolution of an optical spectrum analyzer, compared with the ideal one, was confirmed. In addition, wavelength converted signals with different wavelengths were obtained according to the different wavelengths of the pump lights. Clear eye openings of the wavelength converted signals were observed, and a bit error rate of

We developed an optical processing platform that handles over 100 space-division-multiplexed signals in the C-band. The device consists of free-space optics based on liquid crystal on silicon (LCOS) with a waveguide frontend. Thanks to the holographic wavefront modulation by the LCOS spatial light modulator, the device arbitrarily manipulates the optical amplitude and phase in the space and spectral domains simultaneously. This ability enables us to create various optical processing functions such as tunable wavelength filtering, variable optical attenuation, and flexible delay line interferometry with arbitrary spatial and wavelength channel dependence. These functions are highly suitable for large-scale optical performance monitoring (OPM). As an application, we demonstrate OPM for 100 spatial channels over the C-band. The constructed OPM can monitor not only the power spectrum but also the optical signal-to-noise ratio (OSNR) by setting different LCOS phase patterns. We achieved channel power monitoring and OSNR monitoring with 1.8- and 1.9-dB accuracy over 100 spatial channels.

We demonstrate a highly scalable subsystem-modular optical cross-connect (OXC) that uses sub-OXCs based on a newly developed single-module 6 × 6 wavelength-selective switch (WSS). Network simulations in dynamic-traffic scenarios assure the good routing performance of the architecture. Its technical feasibility is confirmed by transmission experiments using 96-wavelength 32-Gbaud dual-polarization quadrature phase-shift keying (DP-QPSK) signals. The developed 6 × 6 WSS allows each DP-QPSK signal to traverse 12 nodes when the internode distance is 100 km.

We report a configuration of an N-in-1 wavelength selective switch array utilizing on a spatial and planar optical circuit (SPOC) platform. We also demonstrate a novel wavelength crossconnect configuration that provides a simple optical connection.

All-optical wavelength conversion with two-stage-comb-generated pump for RZ-QPSK signals in highly-nonlinear fiber was experimentally investigated. Less than 1GHz frequency deviation of pump and BER of $ for converted idlers with different wavelengths have been achieved.

We demonstrate experimentally SDM node using low power consumption MC-EDFA and 6×6WXC using WSS arrays. MC-EDFA reduced power consumption by 16.4% and WSS arrays switched signals of all cores, revealing potential high-capacity scalable SDM node.

As optical networks have evolved from point-to-point systems to ring or mesh networks, the optical devices that are needed to construct optical nodes have become more important and need to be more scalable. Hybridization of waveguide and free-space optics, or spatial and planar optical circuits (SPOCs), may provide the solutions for such needs. An SPOC platform is attractive because it can take advantage of both waveguide technology and free-space optics. Waveguide technology provides a high degree of integration of optical functionality for devices such as splitters and non-wavelength selective switches while free-space optics supplies a high degree of parallelism with two-dimensional spatial light modulators such as a liquid crystal on silicon (LCOS) devices. In this paper, we summarize the basics of SPOC technology and review its application to reconfigurable optical add-drop multiplexing (ROADM) devices. The key elements of a waveguide on an SPOC platform are an arrayed-waveguide grating and a spatial beam transformer. The latter functions as a microlens array and provides attractive features such as dense integration of switches. An LCOS device has numerous phase modulating pixels, enabling flexible manipulation of lightwaves. Using an SPOC platform, we constructed and demonstrated devices for ROADM applications including a wavelength filter, tunable optical dispersion compensators, and wavelength selective switches (WSSs). The WSSs range from an ultrahigh port count WSS to a single module wavelength cross connect.

We propose a novel optical system that employs alternating wave-band arrangement on LCOS for multi-band operation. We demonstrated a 2-in-1 $1\times 10$ wavelength selective switch (WSS) with the operational range of $C+L$ -band by using multiple PLC frontends.

A wavelength selective switch (WSS) is proposed based on a Bragg reflector waveguide array, which has a footprint of only 2 × 6 mm2. We demonstrated arbitrary switching among 182 output ports by using a liquid crystal on silicon as a switching engine. The proposed WSS module length is only 10 cm, taking an advantage of the large angular dispersion in the Bragg reflector waveguide. Wavelength selective switching of 60 channels is carried out, exhibiting the device's excellent capability in providing ultra-large number of port count and wavelength channel operations at the same time. The crosstalk between adjacent ports are below –20 dB by a suitable alignment, which can be further improved by optimizing the module optics and alignments. The flexible lithography defined waveguide array design also reveals versatile potentials in integrating with other functional components.

We propose a densely integrated programmable spectral processor array that handles over 100ch optical signals. Using the device, we achieved the optical performance monitoring for 100 spatial channels over C-band.

We propose a novel optics for integrated wavelength selective switch (WSS) array that suppresses inter-sub WSS crosstalk for space-division multiplexed network. A crosstalk level of as low as −50 dB has been achieved.

We demonstrate a highly scalable subsystem-modular OXC, where a newly developed single-module 6×6 WSS is utilized as a sub-OXC. Network simulations in dynamic-traffic scenarios assure its good applicability. Its technical feasibility is confirmed by transmission experiments using 32-Gbaud DP-QPSK signals.

A photonic crystal is an artificial crystal with a periodic array of dielectric material. Such a crystal possesses a band gap for an electromagnetic wave with wavelengths corresponding to a lattice period. In this study, the photonic crystal with the spherical lattice of hundreds of micrometer-order corresponding to wavelengths of terahertz wave was fabricated by a template method. Monosized spherical copper particles were self-assembled into f.c.c. structure and sintered to form necks between adjacent particles. The array was impregnated with the resin whose dielectric constant was controlled. Subsequently to cure the resin, only the copper particles lattice was etched away by chemical dissolve. The obtained resin-inversed crystals were confirmed to exhibit a photonic stopgap along ‹111› direction by a terahertz wave spectroscopy. The frequency and gap width of measured gaps well agreed with the calculated ones by the plane wave expansion method.

We propose a tunable optical dispersion compensator (TODC) that uses an arrayed waveguide grating (AWG) and a flat mirror. The TODC employs simple and cost-effective optics, and its chromatic dispersion can be changed simply by translating the AWG. We obtained a 3-dB bandwidth of 39 GHz when the dispersion was tuned within 800 ps/nm, and a maximum dispersion of plusmn3000 ps/nm.

We describe the proof-of-concept demonstration of flexible chromatic dispersion compensation over the entire L-band region wavelength-division-multiplexing transparent networks operating at over 40 Gb/s using span-by-span compensation with an arrayed-waveguide grating and an liquid crystal on silicon-based multichannel tunable dispersion compensator.

Three-dimensional artificial crystals with periodicity corresponding to terahertz wave lengths were fabricated by self-assembling monosized metal spherical particles. The metal crystals were weakly sintered to utilize them as templates. The metal templates were inverted to air spheres crystal embedded in dielectric resin though infiltration and etching. The resulting resin inverted crystals clearly presented the photonic stop gaps within terahertz wave region and the frequencies of the gaps were confirmed to agree well with calculation by plane wave expansion method.

We propose a spatial beam transformer (SBT) for a wavelength selective switch, which is monolithically integrated on a silica-based planar lightwave circuit (PLC). The PLC-integrated SBT has advantages such as freedom from precise alignment and the elimination of expensive bulk optics. In addition, the aspect ratio can be freely designed simply by redesigning the layout of the SBT without adding any other optical components. We successfully tuned the aspect ratio from 7.9 to 87.5 simply by changing the PLC layout.

We realized a wide-passband multi-channel tunable optical dispersion compensator for 88 WDM signals with 50-GHz spacing by combination of an arrayed-waveguide and bulk gratings. It utilizes a novel optics arrangement for high wavelength resolution.

We propose a novel optical configuration for a multichannel tunable optical dispersion compensator (TODC) with channel-by-channel operation across the entire L-band. The TODC consists of a cyclic frequency arrayed-waveguide grating whose free spectral range coincides with the channel spacing, a bulk grating, and a liquid crystal on silicon. We achieved channel-by-channel compensation over 50 channels with a maximum chromatic dispersion of ±800 ps/nm.

We propose a novel optical configuration for a channelized tunable optical dispersion compensator (TODC) with channel-by-channel operation across entire the L-band. The TODC consists of a cyclic frequency arrayed-waveguide grating (AWG) whose free spectral range (FSR) coincides with the channel spacing, a bulk grating and a liquid crystal on silicon. We achieved channel-by-channel compensation over 50 channels with a maximum chromatic dispersion of 800 ps/nm.

We propose a novel configuration for a tunable optical dispersion compensator (TODC) with increased bandwidth. We demonstrate 40-wavelength channelized compensation for 400-ps/nm chromatic dispersion with a 40-GHz bandwidth using the proposed TODC.

We propose a tunable optical dispersion compensator (TODC) using an arrayed-waveguide grating (AWG) and a flat mirror. The TODC employs simple and cost-effective optics, and its chromatic dispersion can be changed simply by translating the AWG. We obtained a tuning range of plusmn 250 ps/nm, a group delay ripple of Lt 3.5 ps and an insertion loss of 6.3 dB.

We demonstrate a tunable optical dispersion compensator consisting of an arrayed-waveguide grating and a liquid crystal on silicon. We obtained a tuning range of ± 800 ps/nm with a bandwidth of 16 GHz.

We propose and demonstrate a multi-channel tunable optical dispersion compensator (TODC) that consists of an arrayed-waveguide grating (AWG) and liquid crystal on silicon (LCOS). By utilizing the AWG with a large angular dispersion and the LCOS with a flexible phase setting, we can construct a compact and flexible TODC that has a wide tuning range of chromatic dispersion. We confirmed experimentally that the TODC could realize channel-by-channel CD compensation for six WDM channels with a ± 800 ps/nm range and a 3 dB bandwidth of 24 GHz. We believe that the multi-channel operation of this TODC will help to reduce the cost and power consumption of high-speed optical transmission systems.