Photonic generation of Ultra-wideband monocycle and doublet pulses using simplex semiconductor optical amplifier Jianji Dong, Xinliang Zhang * , Dexiu Huang, Enbo Zhou Wuhan National Laboratory for Optoelectronics, School of Optoelectronic Science and Engineering, Huazhong University of Science and Technology, Wuhan, China, 430074; ABSTRACT We demonstrate two all-optical methods for UWB pulse generation based on various nonlinearities of the semiconductor optical amplifier (SOA), namely, self phase modulation (SPM), and cross gain modulation (XGM). In the first method, we present UWB doublet generation based on SPM. The monocycle pulse is generated from dark return-to-zero (RZ) signal, and then converted to doublet pulse by injecting an additional probe signal with the SMF transmission. For the first time to best of our knowledge, we report that the generated doublet pulses are transmitted over 5km SMF by proper dispersion compensation without distortion. Second, we present UWB doublet generation by XGM of two cascaded SOAs. The configuration of our all-optical methods is compact and simple. Keywords: Ultra-wideband, semiconductor optical amplifier (SOA), microwave photonics 1. INTRODUCTION Ultra-wideband (UWB) is regulated by the Federal Communications Commission (FCC) and drawn considerable attention for a variety of applications, including communication, imaging, surveillance, and locating. One of the most attractive applications is for the indoor communication system [1]. The UWB technology has many advantages over traditional wireless communication, such as lower power consumption, higher bit rate, immunity to multipath fading, shorter time duration, and lower duty cycle [2, 3]. The FCC also defines UWB as any signal that occupies more than 500MHz bandwidth in the 3.1 to 10.6GHz band or has a fractional bandwidth greater than 20%. The choice of UWB pulse types is critical to the performance of the UWB systems. Gaussian monocycle and doublet pulses are the first-order and second-order derivative of a Gaussian pulse, which have been considered promising candidates for UWB communications [4]. Many approaches to generating UWB signals proposed are implemented using electronic circuits in the electrical domain [5-7]. However, at the current stage of technology, it is difficult and expensive to generate UWB pulses with a large fractional bandwidth. In addition, the current UWB signals are limited to short distances due to the low power density, whereas UWB-over-fiber technology can provide a promising solution to integrate local UWB environment into the fixed wired optical network or wireless wide-area infrastructures [8]. Therefore, it is highly desirable that the UWB signals can be generated directly in optical domain without electrical- optical conversion so that the optics advantages, such as huge bandwidth capacity and immunity to electromagnetic interference, can be utilized. Generally, the UWB generation in optical domain can be grouped into two categories, namely, hybrid method and all- optical method. Fig. 1 shows a conceptual illustration of a typical UWB-over-fiber system, where the UWB signal is generated by (a) hybrid method and (b) all-optical method. In the system, optical UWB pulses are generated and encoded in the central office, transmitted by the fiber link, and distributed to the access point. The hybrid method means that input pulse is generated electrically and the UWB pulse is generated by optical devices, but the all-optical method means both the input pulse and output UWB pulse are generated in the optical domain. And the all-optical schemes can be well incorporated into UWB-over-fiber networks and eventually simplify the entire network. The hybrid methods to generate UWB signals are reported with microwave differentiator [9], optical phase modulators [10-13], chirp-to-intensity converter [10, 14], intensity modulator [15-17], and photonic microwave delay-line filter [18]. The all-optical methods are reported with semiconductor optical amplifier (SOA) [19-22], dispersion shifted fiber [23], and frequency to time * xlzhang@mail.hust.edu.cn, phone 86-27-87792367 Optical Transmission, Switching, and Subsystems VI, edited by Ken-ichi Kitayama, Pierpaolo C. Ghiggino, Kim Roberts, Yikai Su, Proc. of SPIE Vol. 7136, 71362M · © 2008 SPIE · CCC code: 0277-786X/08/$18 · doi: 10.1117/12.803788 Proc. of SPIE Vol. 7136 71362M-1 2008 SPIE Digital Library -- Subscriber Archive Copy