All-optical processing of time-serial IM/DPSK encoded label and payload packets

We demonstrate an all-optical label and payload processor based on nonlinear optical signal processing with semiconductor 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.

I. Introduction

The 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 implementing optical packet switching (OPS) over WDM optical networks. In order to enhance the capabilities of the core routers, matching packet routing speeds and line bitrate, those OLS techniques are deeply focused on all-optical solutions for ultra-fast operation [1]. These so-called all-optical techniques apply signal processing in the optical domain, avoiding any electronic control stages [2], [3]. One possible all-optical node architecture, under study within the IST—All-Optical Label Swapping Employing 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 separate 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. Fig. 1.

Generic all-optical label swapping node architecture. AOLXG: all-optical logic XOR gate; ODL: optical delay line.