IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 12, NO. 4, JULY/AUGUST 2006 679 All-Optical Processing of Time-Serial IM/DPSK Encoded Label and Payload Packets J. J. Vegas Olmos, Idelfonso Tafur Monroy, M. Garc´ ıa Larrod´ e, and A. M. J. Koonen, Senior Member, IEEE Abstract—We demonstrate an all-optical label and payload pro- cessor based on nonlinear optical signal processing with semicon- ductor optical amplifiers. The processor separates the label and the payload, and generates a synchronization pulse, used to control the label comparison operation in an all-optical routing node. Index Terms—All-optical signal processing, nonlinear optics, optical fiber communication, semiconductor optical amplifiers (SOAs). I. INTRODUCTION T HE ever increasing line bitrate of data transmission over wavelength division multiplexing (WDM) links and the new network services, which require packet switched oriented approaches instead of the traditional circuit switched oriented, have recently brought much attention on optical label swapping (OLS) techniques. OLS is a promising technique for implement- ing optical packet switching (OPS) over WDM optical networks. In order to enhance the capabilities of the core routers, match- ing packet routing speeds and line bitrate, those OLS techniques are deeply focused on all-optical solutions for ultra-fast oper- ation [1]. These so-called all-optical techniques apply signal processing in the optical domain, avoiding any electronic con- trol stages [2], [3]. One possible all-optical node architecture, under study within the IST—All-Optical Label Swapping Em- ploying Optical Gates in a Network Node (LASAGNE) project, is depicted in Fig. 1. The performance of packet routing, without electronic control stages, requires a new group of system blocks to be developed, including label and payload separators [4], [5], label comparison blocks [6], and optical flip-flops [7], [8]. A key building block of the node architecture presented in Fig. 1 is the label and payload processor, which should ideally sepa- rate perfectly the label and the payload, and also generate the control pulses for subsequent setting and resetting the all-optical the flip-flop. In that way, when a packet arrives to the node, the label and the payload are separated. The payload is delayed and sent to the wavelength converter. The label is processed by a bank of optical autocorrelators, and a single pulse is generated in case of a matching address. This pulse is used to generate a new label. Simultaneously, a preset pulse obtained from the label data sets the optical flip-flop. The flip-flop signal is used as a probe for the wavelength converter. Then, the delayed payload and the new inserted label are converted into a new wavelength. Manuscript received August 12, 2005; revised March 2, 2006 and March 23, 2006. This work was supported in part by the IST Program of the European Commission. The authors are with the COBRA Institute of Technology, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands (e-mail: j.j.vegas@tue.nl; i.tafur@tue.nl; m.garcia.larrode@tue.nl; a.m.j.koonen@tue.nl). Digital Object Identifier 10.1109/JSTQE.2006.876174 Fig. 1. Generic all-optical label swapping node architecture. AOLXG: all- optical logic XOR gate; ODL: optical delay line. Once the wavelength conversion operation is realized, a re- set pulse is needed to reset the flip-flop into the standby state again. Therefore, not only a block able to separate the label from the payload and vice versa with a high suppression ratio (relation with the signal and the suppressed signal) is needed, but also a pulse generator to optically control the flip-flops. We propose a novel all-optical packet processor to perform such a task, with no need of external synchronized control signal. The proposed architecture uses a combined modulation scheme; intensity modulation (IM) for the label and differential phase- shift keying (DPSK) for the payload. This time-serial, header and payload encoding facilitates the optical signal processing and furthermore, optical transmission by using DPSK modula- tion format [9]–[11] has been demonstrated to be robust against chromatic dispersion, polarization mode dispersion (PMD), and cross-phase modulation (XPM) effects, enabling record high ca- pacity in transmission links [12]. It also reduces pattern effects induced by the semiconductor optical amplifier (SOA) carrier dynamics [13]. Furthermore, the proposed scheme allows for variable-length burst operation without observed distortion in the eye diagrams of both label and payload signals. We exper- imentally demonstrate an all-optical processor, composed of a label and payload separator operating entirely at 10 Gb/s and a single pulse generator. This paper is organized as follows. In Section II, the label and payload separator is described briefly and experimentally demonstrated. In Section III, we investigate a label extractor and pulse generator. Preset and reset pulses can be generated from the incoming packets. Section IV describes a complete all-optical label and payload processor, including label and pay- load separation and pulse generation functionalities. Section V presents summary conclusions. 1077-260X/$20.00 © 2006 IEEE