SOA-based Wavelength Conversion and All-optical Switching of 80 Gb/s Data Packets using a Wavelength Converter and a Monolithically Integrated Optical Flip-flop

We demonstrate an error-free 160 Gb/s SOA-based optical wavelength converter. This optical wavelength converter can be controlled by a monolithically integrated optical flip-flop memory to switch 80 Gb/s data-packets alloptically. The optical wavelength converter consists of an SOA and an optical filter. Assisting by an optical bandpass filter, an effectively recovery time of 3 ps is achieved in an SOA, which ensures 160 Gb/s operation. The integrated optical flip-flop based on two-coupled lasers, exhibits single-mode operation, has 35 dB contrast ratio between the states and switches state in about 2 ns. We show that the integrated flip-flop is capable to control an optical wavelength conversion up to 160 Gb/s. The system is capable of routing 80 Gb/s data packets with duration of 35 ns, separated by 15 ns of guard time. Introduction High-speed all-optical switches offer advantages in power consumption, foot-print and switching architectures compared to their electronic counterparts [1,2]. The essential building blocks of an all-optical packet switch are all-optical wavelength converters (AOWCs) and all-optical flip-flop memories (AOFFs). AOWCs that utilize nonlinearities of semiconductor optical amplifiers (SOAs) have attracted considerable research interest due to the integration ability and power efficiency. A number of SOA-based AOWCs have been demonstrated [3-6]. However, the slow SOA recovery time can cause unwanted pattern effects in the converted signal, which limits the maximum operation speed. We present an error-free and pattern-independent 160 Gb/s wavelength conversion with a low power penalty using a single SOA. The wavelength converter is constructed by using commercially available fiber pigtailed components. The SOA in the experiment has an initial gain recovery time of > 90 ps. We demonstrate that the effectively recovery time of the SOA can be dramatically shortened to be less than 3 ps with the assistance of an optical bandpass filter. A delayed-interferometer is utilized to change the inverted signal into non-inverted signal. It should be noted that in contrast to [5], the differential operation in a delayedinterferometer is not essential for realizing 160 Gb/s operation in our concept. This wavelength converter has a simple configuration and allows photonic integration. In all-optical packet switches, AOFFs are used to store the switch decision information. It has been demonstrated in [7] that an optical flip-flop based on two symmetrically coupled lasers can control an optical packet switch. In that particular configuration, the optical flip-flop state was set by an optical header recognizer, and the flip-flop controls a wavelength routing switch. The flip-flop presented in [7] had a switching time of about 2 μs, since it was implemented using fiber pig-tailed components, which made that the cavity length of each laser was in the order of 10 meters. Recently, we realized a monolithically integrated version of the flip-flop used in [8]. This flip-flop exhibits single-mode operation, has 35 dB contrast ratio between the states and switches state in about 2 ns. In this paper, we show that a wavelength converter controlled by this flipflop allows error-free wavelength conversion at 80 Gb/s [12]. A clear open eye indicates that the system can also operate error-free at 160 Gb/s. Moreover, we demonstrate that this system is capable of switching data packets with duration of 35 ns and a guard time of 15 ns. Experimental results 160 Gb/s SOA-based wavelength conversion The experimental setup is shown in Fig. 1a. The setup was constructed by using commercial available fiberpigtailed components. A 10 Gb/s data stream with 1.9 pswide optical pulses, is modulated by an external modulator (MOD) at 10 Gb/s to form 2−1 RZ-PRBS signal. This data stream is multiplexed to 160 Gb/s. The 160 Gb/s RZ-PRBS data signal is combined with a CW probe light and fed into an AOWC via a 3 dB coupler. The AOWC is made out of an SOA, a 1.4 nm optical bandpass filter (BPF) and a delayed-interferometer (DI). The 1.4 nm BPF is detuned 1.23 nm to the blue side of the probe carrier wavelength. The DI consists of two polarization controllers (PCs), a polarization maintaining fiber (PMF) with 2 ps differential delay, and a polarization beam splitter (PBS). The SOA is pumped with 250 mA. The average optical power of the 160 Gb/s data stream is 4.8 mW and 2.6 mW for the CW probe light. At the output of the 1.4 nm BPF, the converted probe light is monitored by using an optical sampling scope, the result is shown in Fig. 1b. An inverted 160 Gb/s signal with a clear open eye-pattern is obtained, which clearly shows that a 3 ps recovery is achieved. The inverted 160 Gb/s converted signal is subsequently injected into the DI, where the inverted signal is converted into a noninverted signal. The result is presented in Fig. 1c. It is noted that the differential operation in the DI is not essential for realizing 160 Gb/s operation because the input (inverted) pulses have already been fully recovered within 3 ps, as shown in Fig. 1b. After wavelength conversion, the converted signal is