Optical data packet synchronization and multiplexing using a tunable optical delay based on wavelength conversion and inter-channel chromatic dispersion Irfan Fazal1, Omer Yilmaz1, Scott Nuccio1, Bo Zhang1, Alan E. Willner1, Carsten Langrock2 and Martin M. Fejer2 1
Dept. of Electrical Engineering – Systems, University of Southern California, Los Angeles, CA-90007 2 Edward L. Ginzton Laboratory, Stanford University, Stanford, CA-94305
[email protected]
Abstract: 10 Gb/s non-return-to-zero (NRZ) on-off keyed (OOK) optical data packets are synchronized and time-multiplexed using a 26-ns tunable all-optical delay line. The delay element is based on wavelength conversion in periodically poled lithium niobate (PPLN) waveguides, inter-channel chromatic dispersion in dispersion compensating fiber (DCF) and intrachannel dispersion compensation with a chirped fiber Bragg grating (FBG). Delay reconfiguration time is measured to be less than 300 ps. ©2007 Optical Society of America OCIS codes: (060.4259) Networks, packet-switched; (060.2360) Fiber optics links and subsystems; (190.2620) Frequency Conversion.
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(C) 2007 OSA
Received 9 May 2007; revised 1 Aug 2007; accepted 2 Aug 2007; published 6 Aug 2007
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1. Introduction Optical packet switching holds the promise of highly efficient use of the available bandwidth in an optical network. As with electronic packet switching, a key enabling technology is the ability to controllably delay/buffer a data packet so as to synchronize packets and rapidly resolve output port contention. Desirable characteristics of this delay include large tuning range, continuous tunability, and rapid reconfiguration [1]. Previously published results for optical delays used in packet switching have typically been chosen from a finite set of discrete optical path lengths. This methodology produces only a fixed set of delays, whether they are in fiber [2, 3], waveguides [4], or free-space [5]. However, a laudable goal for a truly flexible and efficient packet switch would be to generate any arbitrary delay value. Recently, tunable delays have been shown using wavelength conversion via self-phase modulation [7] or four wave mixing [8, 9] coupled with dispersive elements. In this method, a data stream was converted to a slower-propagating wavelength, followed by conversion back to the original wavelength. Note that proper dispersion compensation was necessary. The result is that a data bit arrives at the output, delayed in time relative to a data bit that had always resided at the original, faster-propagating wavelength. Bit-level delays were shown [10], but little was reported relating to using these delays for time manipulation and synchronization of full data packets. In this paper, we experimentally demonstrate synchronizing and multiplexing of optical data packets using a 26-ns tunable optical delay based on wavelength conversion and inter-channel chromatic dispersion. We achieved tunability for 10-Gbit/s non-return-to-zero (NRZ) on-off keyed (OOK) data packets, multiplexed two packet streams, and measured a 10-9 bit error rate (BER). The delay reconfiguration time from one delay value to another was measured to be
