Ronald Menendez

Spectrally efficient optical CDMA using coherent phase-frequency coding

We demonstrate feasibility of a spectrally efficient wavelength-division-multiplexing-compatible optical code-division multiple-access system using 16 phase-locked laser lines within an 80-GHz tunable window as frequency bins and an ultrahigh frequency resolution spectral phase encoder-decoder. Coding and decoding using binary [0, /spl pi/] phase chips were demonstrated for four users at 2.5 Gb/s, and a single coded signal was separated from four copropagating signals, with bit-error rate <10/sup -9/.

Fully programmable ring-resonator-based integrated photonic circuit for phase coherent applications

A novel ring-resonator-based integrated photonic chip with ultrafine frequency resolution, providing programmable, stable, and accurate optical-phase control is demonstrated. The ability to manipulate the optical phase of the individual frequency components of a signal is a powerful tool for optical communications, signal processing, and RF photonics applications. As a demonstration of the power of these components, we report their use as programmable spectral-phase encoders (SPEs) and decoders for wavelength-division-multiplexing (WDM)-compatible optical code-division multiple access (OCDMA). Most important for the application here, the high resolution of these ring-resonator circuits makes possible the independent control of the optical phase of the individual tightly spaced frequency lines of a mode-locked laser (MLL). This unique approach allows us to limit the coded signals spectral bandwidth, thereby allowing for high spectral efficiency (compared to other OCDMA systems) and compatibility with existing WDM systems with a rapidly reconfigurable set of codes. A four-user OCDMA system using polarization multiplexing is shown to operate at data rates of 2.5 Gb/s within a 40-GHz transparent optical window with a bit error rate (BER) better than 10/sup -9/ and a spectral efficiency of 25%.

GHz-bandwidth optical filters based on high-order silicon ring resonators

Previously demonstrated high-order silicon ring filters typically have bandwidths larger than 100 GHz. Here we demonstrate 1-2 GHz-bandwidth filters with very high extinction ratios (~50 dB). The silicon waveguides employed to construct these filters have propagation losses of ~0.5 dB/cm. Each ring of a filter is thermally controlled by metal heaters situated on the top of the ring. With a power dissipation of ~72 mW, the ring resonance can be tuned by one free spectral range, resulting in wavelength-tunable optical filters. Both second-order and fifth-order ring resonators are presented, which can find ready application in microwave/radio frequency signal processing.

Experimental results on the simultaneous transmission of two 2.5 Gbps optical-CDMA channels and a 10 Gbps OOK channel within the same WDM window

We propose and experimentally validate a novel method for transmitting several OCDMA channels in the unused bandwidth of a single WDM channel thus allowing the OCDMA and SONET signals to share the same WDM channel.

A novel method for increasing the spectral efficiency of optical CDMA

Given K simultaneously active users, an Optical CDMA (OCDMA) receiver needs to discriminate among K codes. Since the number of available codes C is always C Gt K at any given time for any truly asynchronous OCDMA system that employs quasi-orthogonal codes, there is always a set of unused codes. We here propose to exploit these unused codes to increase the spectral efficiency of the system. This can be accomplished by exclusively assigning to each user a set of M codes which represent a log2(M)-tuple of bits so that each user effectively uses a multi-dimensional modulation (multiple information bits per code are conveyed). In this paper, we analyze the performance of such a system and find in closed form an upper bound on the average probability of error. Moreover, we report for the first time that, under lightly loaded, non interference-limited conditions, the multi-dimensional OCDMA scheme here proposed allows us to obtain both higher spectral efficiency and lower bit- error probability (BEP) than a conventional OCDMA system, which employs one code only per user. The analysis here presented allow us to formulate a useful system design criterion that yields truly asynchronous OCDMA systems with very high spectral efficiency.

Efficient, Fault-Tolerant All-Optical Multicast Networks via Network Coding

Network coding, an emerging field of research, provides a means to create efficient all-optical multicast networks that feature hitless reconfiguration. Here a photonic bitwise exclusive-OR hardware element supplies the key enabling functionality.

Spectrally Efficient Six-User Coherent OCDMA System Using Reconfigurable Integrated Ring Resonator Circuits

We demonstrate a spectral phase encoded optical code-division multiple-access system using programmable ring-resonator-based integrated coders. A six-user polarization multiplexed system operates at data rates of 5 Gb/s within an 80-GHz transparent optical window with a bit-error rate of 5times10-11 or better and a high spectral efficiency of 0.375 b/s/Hz

Fully-programmable ring resonator based integrated photonic circuit for phase coherent applications

We demonstrate a novel reconfigurable ring resonator based integrated photonic chip with ultra-fine frequency resolution for spectral phase encoding. A spectrally efficient four-user OCDMA system is shown to operate at 2.5 Gb/s with BER< 10/sup -9/.

DWDM-compatible spectrally phase encoded optical CDMA

We present initial results on a WDM compatible spectrally phase encoded optical CDMA (OCDMA) system that uses 16 phase-locked laser lines within an 80-GHz tunable window and an ultrahigh frequency resolution encoder/decoder. The described system differs from conventional OCDMA systems by independently phase encoding individual spectral line of a mode locked laser (MLL). We report here novel properties of phase codes and we also demonstrate compatibility of the proposed OCDMA system with conventional WDM networking by simultaneous transmission of two 2.5 Gb/s OCDMA users in one DWDM window along with six DWDM channels in other DWDM windows through a transparent reconfigurable network having 25 km node spacing.

An Overlay Photonic Layer Security Approach Scalable to 100 Gb/s

As data rates outpace the capabilities of electronic encryption schemes, photonic layer security may fill the gap in providing a communication security solution at high data rates. In this article we review and highlight the advantages of our proposed optical code-division multiplexed (OCDM)-based photonic layer security (PLS) system based on high-resolution control of the optical phase of tightly spaced phase locked laser lines. Such a PLS system is scaleable to 100 Gb/s and provides a protocol independent security solution. We review the use of high-resolution control of the optical phase of mode-locked laser frequency combs as an enabling technology for a new class of OCDM systems. A network based on such systems is compatible with and can have comparable spectral efficiency to existing DWDM networks. Through inverse multiplexing of 10 Gb/s tributaries, we have already demonstrated optical transmission of a 40 Gb/s aggregate OCDM signal over 400 km. Such a PLS solution is achieved through shared phase scrambling of the individual OCDM codes assigned to each of the tributaries using an integrated micro-ring resonator-based phase coder/scrambler. The confidentiality of OCDM-based PLS is robust against exhaustive, known plain text, and archival/forensic attacks, and can complement digital encryption operating at higher layers. Moreover, the integrity of the PLS solution is ensured through the inherent coupling to confidentiality, since knowledge of the key is needed in order to easily alter the transmitted data stream without introducing observable errors. This system can leverage advances in optical integration to support new applications where electronic encryption is impractical because of space, weight, power, availability, and cost requirements. Such applications range from timely security support for the emerging 100 GbE standards to all-optical multilevel security offered through the compatibility of PLS with transparent DWDM networks.