Demonstration of an Optical Packet Label Swapping Scheme Using DPSK Encoded Bit-Serial Labels

INTRODUCTION Optical label switching (OLS) is a promising technique for enabling low-latency forwarding of high-speed optical packets in future packet-based WDM networks. An efficient and robust optical label swapping technique is necessary for practical implementation. Several labeling schemes, including bit-serial [1, 2], sub-carrier multiplexing (SCM) [3] and orthogonal modulation [4] schemes have been proposed and demonstrated. Among these schemes, bit-serial approach is the least restrictive approach in terms of packet bit rate and modulation extinction ratio. However, low penalty label swapping was only achievable using bulky fiber-based nonlinear process [1] or synchronous logic operation with high timing requirements [2]. In this letter, we report a simple bit-serial optical packet label swapping scheme using optical return-to-zero differential phase shift keying (RZ-DPSK) encoded labels and RZ-OOK packet payload. The use of the RZ-DPSK label in bit-serial manner imposes no constraint on the extinction ratio of the optical packets. The phase-encoded label information can be effectively erased asynchronously by means of a wavelength converter. The content-erased RZ label bits can then be DPSK-encoded with the new label information via an optical phase modulator. Thus, a simple and robust optical label swapping can be realized. The feasibility and performance of this proposed scheme have been proven experimentally on 10.61-Gb/s RZ optical packets.