With the consideration of fast gain saturation, an approximate analytical solution of nondegenerate four-wave mixing between short optical pulses in a semiconductor optical amplifier is presented. It is simple and agrees well with the rigorous solution. In addition, conditions for the optimum pump input energy and the time delay between the pulses are also investigated.

This paper presents a new technology for constructing IP over photonic systems. An IP with multiprotocol label switching (MPLS) over wavelength division multiplexing (WDM)-based broad-band IP network architecture and protocol is proposed and analyzed in this paper, which supports variable-length IP-like optical packet label switching and optical virtual path routing. This system tries to merge into one layer the functionalities of the wavelength switching, SONET mux/demux, and IP routing, and is sometimes known as the concept of optical MPLS. The label banding, forwarding/switching process, and node architecture of the proposed network are discussed and studied. A unique as well as important function of a lambda/label edge router (LER) is a flow assembly device that can encompass MPLS' forward equivalence classes, label stacking, and label switching path aggregation function. At the same time, a particular function of the core label switching router is wavelength merging. A fiber delay line is used to delay the data stream in order to process the label information and resolve contention. Transmission bit error rate measurements of the baseband data stream and back-to-back is also demonstrated to show its feasibility.

A novel optical time-division multiplexing frame synchronization scheme based on a terahertz optical asymmetric demultiplxer (TOAD) and an electrical clock extraction circuit with feedback is presented and simulated. This scheme is characterized by both the ultrahigh speed of a TOAD and the high clock fidelity of the electrical clock extraction circuit. The simulation shows that this scheme can perform frame synchronization very soon, and a very low timing jitter can be obtained in the recovered frame clock.

A novel self-synchronization scheme utilizing a semiconductor optical amplifier (SOA) monolithically integrated with a delay interferometer (DI) is proposed and numerically demonstrated in this letter. The proposed scheme is based on the fast gain saturation and relatively slow gain recovery of the SOA. With the properly chosen DI delay time, input pulsewidth, and SOA carrier lifetime, input pulse energies as low as 100 fJ can be utilized to achieve a larger than 10-dB contrast ratio of the first to the other pulses of a transmitted packet.

In this paper, we develop an analytical method to deal with the timing performance in an optical clock extraction circuit based on stimulated Brillouin scattering (SBS). Three kinds of SBS active filters are considered and their frequency-transfer functions are obtained under the assumption that pump depletion caused by SBS is negligible. When pump depletion is taken into account, an SBS active filter acts as a nonlinear filter. To investigate the timing performance at this situation, we introduce the concept of "dynamic frequency-transfer function" to describe its frequency-response property for a fixed-signal light and pump light. Using the obtained "frequency-transfer function," we give analytical expressions for both root-mean-square (rms) phase jitter and rms amplitude jitter of the extracted optical clock, in which we have taken the impacts of SBS gain, pump light linewidth, optical pulse chirp, and pump detuning into account. Finally, a detailed numerical investigation on the timing performance for the three active filters is presented.

A performance analysis of an optical clock extraction circuit based on a Fabry-Perot filter (FPF) is presented. Two analytical methods, time-domain and frequency-domain analysis, are developed in this paper. Time-domain analysis shows that there is no phase jitter in the extracted optical clock if the free spectral range (FSR) of the FPF is exactly equal to the signal clock frequency. Based on this, we obtain an analytical expression for root mean square (rms) amplitude jitter of the extracted optical clock in time domain, in which we have taken the impacts of carrier frequency drift and carrier phase noise into account. When the FSR of the FPF deviates from the signal clock frequency, both phase jitter and amplitude jitter will occur in the extracted optical clock. In this situation, a more general frequency-domain method is developed to deal with the timing performance under the assumption that carrier phase noise is negligible. This method allows us to calculate both rms phase jitter and rms amplitude jitter of the extracted optical clock. Using the developed two methods, we present a detailed numerical investigation on the impacts of finesse of the FPF, carrier frequency drift, resonator detuning, carrier phase noise, and optical pulse chirp on the timing performance. Finally, the application of this circuit in multiwavelength clock recovery is discussed.

This article reviews the current status and technologies of all-optical XOR gates. Various schemes with semiconductor optical amplifiers, particularly those associated with interferometric structures, are discussed and compared. Finally, the applications of all-optical XOR gates to emerging networks are explored, and the future direction is outlined.

An analytical theory is presented which demonstrates the timing jitter induced by amplifier noise in ultrahigh-speed dispersion- managed soliton systems when the Raman effect and thirdorder dispersion (TOD) are considered. The analysis indicates that Raman jitter remains a potential problem for picosecond and subpicosecond pulses. Positive residual TOD can enhance the timing jitter caused by the combined action of TOD and Raman effect, while vice versa for negative residual TOD. Dispersion-managed soliton, Raman effect, thirdorder dispersion, timing jitter, ultrahigh bit rates.

The performance of ultra-fast all-optical XOR gate using two types semiconductor optical amplifier-based Mach-Zehnder interferometers (SOA-MZIs) is analyzed. Key parameters are optimized through numerical simulations. With properly designed parameters, 40 Gb/s all-optical XOR gate using SOA-MZI can be realized with fairly high performance. The results are helpful for parameter design of SOA-MZI-based XOR gate.

The performance degradation of differential quadrature phase-shift keying (DQPSK) wavelength-division-multiplexed (WDM) systems due to self-phase modulation (SPM)- and cross-phase modulation (XPM)-induced nonlinear phase noise is evaluated in this letter. The XPM-induced nonlinear phase noise is approximated as Gaussian distribution and summed together with the SPM-induced nonlinear phase noise. We demonstrate that 10-Gb/s systems, whose walkoff length is larger than 40-Gb/s systems', are more sensitive to XPM-induced nonlinear phase noise than 40-Gb/s systems. Furthermore, DQPSK WDM systems show lower tolerance to both SPM- and XPM-induced nonlinear phase noise than differential phase-shift keying WDM systems.