Fundamental research of 300-Gb/s-class, semiconductor-based,
all-optical gate scheme which contains complex-amplitude
spectrum synthesizer
Takehiro Nishida1, Satoshi Shinada2, Naoya Wada2,Takeru Yamaji1, Ryoichi Nakamoto1, a), and Yoshiyasu Ueno1
1. Univ. of Electro-Communications (UEC), Dept. of Electronic Engineering
2. National Institute of Information and Communications Technology (NICT)a) present affiliation: Sumitomo Electric Industries, Ltd.
e-mail: nishida@ultralfast.ee.uec.ac.jp
All-optical wavelength converters based on semiconductor optical amplifiers (SOAs) are promising
devices for future high-capacity wavelength-division-multiplexing (WDM) networks, due to their ultrafast
response, low power consumption, and integration potential. 320-Gb/s wavelength conversion with adelayed-interference (DI) scheme has recently been demonstrated1. For ultrahigh-speed signal processing
above 320 GHz, pulse width shorter than 1 ps is required. It has been reported that under ultra-short control
pulses the gated output waveforms with the DI scheme is distorted since the SOA gain recovery has fastand slow components (Fig. 1) due to carrier temperature relaxation and electron-hole recombination,
respectively2. Ueno et al. had numerically demonstrated a particular optical-spectrum-synthesizer (OSS)
design that independently controls the intensity and the phase of spectrum with the expanded DI scheme,by which the gated waveform distortion has successfully been removed3. In this talk, we report the progressof experimental demonstration that all-optical gate with OSS removes the gated output waveform distortion.
In advance of experimentally studying the OSS gate scheme, we characterized the spectral resolution andthe extinction ratio of one of our proto-type OSS (it is called variable bandwidth spectrum shaper4 (VBS,Optoquest Co., Ltd.) due to control function). The spectral resolution and the extinction ratio were from 9.7
GHz to 11.6 GHz and 13 dB, respectively. According to these latest results, we have estimated that we’ll beable to verify the validity of the above-mentioned new scheme by our experimentally removing most of thewaveform distortion with using the existing proto-type OSS. Figure 2 indicates the presently estimateddegree of improvement (i.e., from the distortion without VBS in Fig. 2(a), to that with VBS in Fig. 2(b)).
Based on these estimated results, we will try to experimentally observe such significant removals of theultrafast distortion, and present one typical example in the poster presentation.

Fig 1. Measured (solid) and calculated(dashed) SOA gain recovery. Input pulses are
2.0-ps 10-fJ at 1.25-GHz. The fast and slow
recovery time constants were 6.0 ps and 50 ps,respectively.

Fig 2. Numerically estimated waveforms at the output of all-opticalgates, where 2.7-ps, 40-GHz, 7.6-fJ input pulses were assumed.
(a): assuming the conventional gate scheme.
(b): assuming our planning experimentwith an existing proto-type OSS.

References
1. Y. Liu, E. Tangdiongga, Z. Li, H. de Waardt, A.M.J. Koonen, G.D. Khoe, X. Shu, I. Bennion, and H.J.S. Dorren, IEEE J.
Lightwave Technol. 25, 103 (2007).
2. J. Mørk, T.W. Berg, M.L. Nielsen, and A.V. Uskov, IEICE TRANS. ELECTRON. E87-C, 1126 (2004).
3. Y. Ueno, R. Nakamoto, J. Sakaguchi, and R. Suzuki, Optics Express 14, 12655 (2006).
4. S. Anzai, M. Mieno, Y. Komai, N. Wada, T. Yoda, T. Miyazaki, and K. Kodate, OFC/NFOEC 2008, JThA25 (2008).