IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 18, NO. 5, MARCH 1, 2006 679 Repetition Rate and Center Wavelength-Tunable Optical Pulse Generation Using an Optical Comb Generator and a High-Resolution Arrayed-Waveguide Grating Kohei Mandai, Student Member, IEEE, Daisuke Miyamoto, Student Member, IEEE, Takanori Suzuki, Hiroyuki Tsuda, Member, IEEE, Koichi Aizawa, and Takashi Kurokawa, Member, IEEE Abstract—Optical pulse generation using an optical comb generator and a high-resolution arrayed-waveguide grating with 30 integrated phase and amplitude modulators is successfully demonstrated. The repetition rate and the center wavelength of the Gaussian pulse train can be controlled from 9.7 to 10.3 GHz and from 1527 to 1565 nm, respectively. Index Terms—Arrayed-waveguide grating (AWG), optical frequency comb, optical pulse generation, optical pulse shaping. I. INTRODUCTION T HE SHAPING of optical pulses with diffraction gratings and a spatial light modulator has been studied extensively [1], and the diffraction gratings have been replaced with an arrayed-waveguide grating (AWG) for application to an optical communication system [2]–[5]. In particular, the deployment of an AWG with integrated phase and amplitude modulators has proved useful for synthesizing optical pulses in combi- nation with an optical frequency comb [6]–[11]. This system features arbitrary waveform generation with relatively large and continuous tuning of the repetition frequency, wide tun- ability of the center wavelength, and a high signal-to-noise ratio. These features are advantageous when compared to a semiconductor mode-locked laser diode (MLLD) and a fiber ring laser. Therefore, such a system is suitable for use as a coherent seed source for an ultrashort pulse generator, and it can also be applied as an optical source for dense wave- length-division multiplexing [6]. In this letter, a 30-ch 10-GHz spacing high-resolution AWG was fabricated and used to control an optical comb generated by lithium niobate (LN) phase and intensity modulators [12]. Gaussian optical pulses were successfully generated for the input light with center wavelengths covering the whole of -band (1527–1565 nm) at repetition rates of 9.7–10.3 GHz. Manuscript received July 21, 2005; revised November 18, 2005. This work was supported by the Ministry of Public Management, Home Affairs, Posts and Telecommunications. K. Mandai, D. Miyamoto, T. Suzuki, and H. Tsuda are with the Department of Electronics and Electrical Engineering, Keio University, Kanagawa 223-8522, Japan (e-mail: mandai@tsud.elec.keio.ac.jp). K. Aizawa and T. Kurokawa are with the Faculty of Technology, Tokyo Uni- versity of Agriculture and Technology, Tokyo 184-8588, Japan. Digital Object Identifier 10.1109/LPT.2006.870060 Fig. 1. (a) Schematic of an arbitrary short pulse generator realized by controlling the sidebands of the modulated light, and (b) an AWG with integrated modulators. II. OPTICAL PULSE SYNTHESIZER The schematic configuration of the optical pulse generator is shown in Fig. 1(a). Continuous-wave light with a frequency of emitted from a tunable laser diode (LD) was modulated at a rep- etition frequency of by an LN optical phase modulator and an LN intensity modulator connected in series [12]. In this experi- mental setup, the insertion loss of the optical comb generator was 12 dB. The modulators were driven by in-phase electrical sinu- soidal signals, . The spectral bandwidth of the comb is almost proportional to the modulation index of the phase modu- lator . The peak-to-peak modulation amplitude and the bias of the intensity modulator are and , respectively. 1041-1135/$20.00 © 2006 IEEE