Takahashi Hiroshi

We designed and fabricated an integrated 1×4 wavelength selective switch using a silica planar light wave circuit. The channel spacing is 100 GHz and the number of channels is 40. Signal switching experiments show the switch to be error-free and have low power penalty bit-error rate performance.

We designed and fabricated an integrated 1×4 wavelength selective switch using a silica planar light wave circuit. The channel spacing is 100 GHz and the number of channels is 40. Signal switching experiments show the switch to be error-free and have low power penalty bit-error rate performance.

We designed and fabricated an arrayed-waveguide grating (AWG) type high-resolution optical spectrum control circuit using silica planar lightwave circuit (PLC) technology for optical signal processing. The spectral phase and amplitude of an optical signal can be controlled. In order to obtain flat pass band characteristics, the number of spectral output waveguides is set to be twice as many as that of arrayed waveguides in the AWG. We obtained flat pass band characteristics with a ripple of 0.9dB or below with the fabricated device by controlling tunable phase shifters.

We designed and fabricated an arrayed-waveguide grating (AWG) type high-resolution optical spectrum control circuit using silica planar lightwave circuit (PLC) technology for optical signal processing. The spectral phase and amplitude of an optical signal can be controlled. In order to obtain flat pass band characteristics, the number of spectral output waveguides is set to be twice as many as that of arrayed waveguides in the AWG. We obtained flat pass band characteristics with a ripple of 0.9dB or below with the fabricated device by controlling tunable phase shifters.

We designed and fabricated integrated 1x2 wavelength selective switches (WSSs) for both fixed and flexible frequency grid. The fixed-grid WSS works for 40ch, 100GHz-spacing wavelength division multiplexing (WDM) signals and has the maximum loss of 8.1dB and the crosstalk ranging from -40.7 to -23.0dB. The flexible-grid WSS can adjust the channel bandwidth from 200GHz to 4000GHz. The maximum loss and crosstalk are 5.9dB and -25.1dB, respectively.

We designed and fabricated integrated 1x2 wavelength selective switches (WSSs) for both fixed and flexible frequency grid. The fixed-grid WSS works for 40ch, 100GHz-spacing wavelength division multiplexing (WDM) signals and has the maximum loss of 8.1dB and the crosstalk ranging from -40.7 to -23.0dB. The flexible-grid WSS can adjust the channel bandwidth from 200GHz to 4000GHz. The maximum loss and crosstalk are 5.9dB and -25.1dB, respectively.

In order to cope with the further traffic expansion due to the introduction of future broadband services such as IP-TV/VoD, hierarchical optical path networks that utilize waveband paths, groups of multiple wavelength paths, have been investigated. It was shown that node switch scale of the hierarchical optical path network node (Hierarchical Optical Cross-Connect: HOXC) can significantly be reduced when the grooming ratio, the ratio of number of groomed waveband paths to that of all incoming/outgoing waveband paths, is restricted [S. Kakehashi et al., 2008]. A recent work [L. H. Chau et al., 2008] elucidates that network with colorless grooming ratio restriction, which defmes grooming ratio regardless of the waveband index, can offer high efficiency of path utilization by utilizing a new effective design algorithm. In this paper, we develop a novel matrix-switch-based HOXC architecture and wavelength MTJX/DMUX that implement the colorless grooming ratio restriction. Numerical evaluations demonstrate that our proposed HOXC can significantly reduce node switch scale compared not only to the single-layer optical path network node (single-layer OXC) but also the conventional HOXC node that offers the same restriction. We also developed a prototype system of the proposed HOXC node and performed transmission experiments to verify its good transmission characteristics.

Optical signal processing based on time-to-space conversion is key technology in high speed optical communication system. It can be applied to dispersion compensation or to optical waveform shaping. In this report, we proposed a high-resolution optical spectrum control circuit that has flat transmission and can arbitrarily control phase or amplitude of optical signal in frequency domain. We also studied band-limited transmission system using this circuit to improve frequency usage efficiency.

We proposed and demonstrated a newly developed tandem MZI-synchronized AWG for wide and low-ripple passband. 0.5dB passband of 59GHz and group delay ripple of ±1psec were obtained. To farther improvement, we also developed a modified version employing 1st mode-converter and simple way to eliminate its GDR. We obtained 0.5dB passband of 69GHz and 0.5ps total GDR for a dispersion balanced out pair.

We fabricated a tunable optical dispersion compensator using integrated resin lenses in an arrayed-waveguide rating. It utilizes thermooptic effect of the lens material to tune the dispersion. The dispersion was successfully controlled from +47 to +410ps/nm. The 3-dB bandwidth was changed 80 to 38GHz. The power consumption at the maximum dispersion setting was 7.2W. Error-free dispersion compensation was confirmed for 42.7-Gbps CSRZ-DQPSK optical signals. The OSNR penalty at BER of 10^<-9> was less than 1.5dB.