Hyperfine Spectral Phase Coded Optical CDMA:
Component Technologies and Networking Applications
P. Toliver and S. Etemad
Telcordia Technologies, 331 Newman Springs Road, Red Bank, NJ 07724
email: ptoliver@research.telcordia.com
Recently, there has been a renewed interest in exploring optical CDMA (OCDMA) as a next generation
communications technology. Some of benefits it has the potential to offer include increased levels of security at the
physical layer as well as the possibility to simplify certain networking functions, such as code translation. A variety
of optical CDMA implementations have been proposed and can generally be classified as either coherent or
incoherent approaches, each of which has its own set of advantages and challenges. This paper will focus on a
specific coherent approach to OCDMA referred to as spectral phase coding. What is unique about this work over
previous research is the fine spectral resolution at which our orthogonal phase codes are applied. Through the use of
ultra-narrow spectral filtering techniques, including hyperfine DWDM filters and ring resonator technologies, our
system is able to accurately tailor the spectral phase of each distinct frequency lines from a mode-locked laser
operating at 5 or 10 GHz. This approach enables us to make the spectral width of the OCDMA signal, coded with
an orthogonal phase mask covering 16 frequency bins, compatible with filtering and transmission components used
in conventional DWDM systems aligned on a 100 or 200 GHz ITU grid. By combining coherent OCDMA with
orthogonal coding and synchronous user operation, the largest overall system spectral efficiency can be achieved.
In addition to describing the system architecture and device technologies, we will also present recent
experimental results on practical optical networking applications, including the transmission of OCDMA with other
conventional DWDM channels (inter-band compatibility). In addition, we show it is possible to have the OCDMA
signal coexist with a conventional DWDM channel within the same passband (intra-band compatibility). Finally,
we demonstrate the ease at which OCDMA signals can be translated from one code to another code using
completely passive optics, and discuss how this function can be exploited in a practical OCDMA networks.
Fig. 1 Illustration of hyperfine spectral phase coded OCMDA system architecture and conceptual view of
optical signals as they propagate through the system, represented both in time and frequency domains.
Paul Toliver received his B.S. in Electrical Engineering from the University of Wisconsin-Madison in 1995 and his
Ph.D. in Electrical Engineering from Princeton University in 2000, where his research focused on 100 Gb/s photonic
packet switching networks and ultrafast all-optical interferometric switches. Since 1995, he has participated in a
number of government and commercial optical networking systems research efforts. He was involved in the
research and development of next generation DWDM systems and technologies within Nortel Networks Advanced
Technologies Group. In October 2000, he joined the Telcordia Technologies, Applied Research as a Senior
Research Scientist, where he has recently been involved in a number of government-sponsored next-generation
optical networking research programs including transparent optical networks, optical label switching, optical
CDMA, and quantum communications.