John D. Moores

All-Optical Network Consortium-ultrafast TDM networks

We describe recent results of the Advanced Research Projects Agency (ARPA) sponsored Consortium on Wideband All-Optical Networks which is developing architectures, technology components, and applications for ultrafast 100 Gb/s time-division multiplexing (TDM) optical networks. The shared-media ultrafast networks we envision are appropriate for providing low-access-delay bandwidth on demand to both future high-burst rate (100 Gb/s) users as well aggregates of lower-rate users (i.e., a heterogeneous user population). To realize these goals we are developing ultrafast network architectures such as HLAN, described here, that operate well in high-latency environments and require only limited processing capability at the ultrafast bit rates. We also describe results on 80-Gb/s, 90-km soliton transmission, 100-Gb/s soliton compression laser source technology, picosecond short-pulse fiber ring lasers, picosecond-accuracy optical bit-phase sensing and clock recovery, all-optical injection-locked fiber figure-eight laser clock recovery, short-pulse fiber loop storage, and all-optical pulse width and wavelength conversion.

Soliton transmission control

The Gordon-Haus limit of long-distance soliton transmission can be partially overcome through the use of linear filters in each amplifier stage. New limits are derived, and they show the possibility of increased bit rates and/or distances of propagation.

On the Ginzburg-Landau laser mode-locking model with fifth-order saturable absorber term

Abstract A modified equation describing the laser field in a passively mode-locked laser is presented. This model includes a fast saturable absorber which is bleached only over a limited intensity-range, as in an additive pulse mode-locked (APM) laser. Dynamic stability is analyzed in the near-soliton limit, and it is shown that the fifth-order saturable absorber term plays a key role in stabilization. The model is compatible with the experimental observation of per-pass nonlinear phase shifts on the order of π/2 radians in APM lasers. Finally, approximate and exact solutions are obtained.

Nonlinear compression of chirped solitary waves with and without phase modulation

Novel exact solutions suggest the possibility of clean and efficient nonlinear compression of chirped solitary waves with appropriate tailoring of the gain or dispersion as a function of distance and with optional phase modulation. A numerical simulation with 20-fold compression is reported. Numerical tests reveal the robustness of the technique to perturbations of the initial condition or to the tailored gain/dispersion.

Stability and timing maintenance in soliton transmission and storage rings

Abstract Several compensation techniques, including intensity-dependent absorption/gain, filtering, and phase- and amplitude-modulation, are considered for use in high bit rate (100+ Gb/s) pulse storage rings and transmission. We propose novel memory devices utilizing intensity-dependent absorption/gain. Other compensation methods include filtering and amplitude- and phase-modulation, which provide restoring forces to suppress frequency- and timing shifts of pulses. The relative merits of these compensation techniques are evaluated perturbatively. We consider the influence of amplifier noise, Raman self-frequency shift, and third-order dispersion. In the absence of compensation, Raman timing fluctuations grow with the fifth power of distance, and may exceed Gordon-Haus jitter at approximately 40 Gb/s. The compensation techniques can eliminate the asymptotic growth of timing variance.

Effect of third-order dispersion on passive mode locking

The effect of third-order dispersion on the width of mode-locked pulses is investigated analytically and numerically. The pulse width increases monotonically with increasing third-order dispersion as a consequence of the symmetric chirp introduced by it. The chirp broadens the bandwidth and lowers the gain. Computer simulations show the appearance of a resonant sideband that also taxes the gain. Reducing the filter bandwidth partially suppresses the sideband and narrows the pulse.

Demonstration of optical switching by means of solitary wave collisions in a fiber ring reflector

We have demonstrated the use of solitary wave collisions in optical pulse switching. Our apparatus consisted of a fiber ring with 11 sections of polarization-maintaining fiber, with successive sections fusion spliced with the axes rotated 90 deg. The configuration yielded enhanced transmission (autocorrelation contrast ratio 2.82:1), in agreement with expectation for this number of sections and the unoptimized fiber coupler that was used. Design criteria for complete switching are presented.

20-GHz optical storage loop/laser using amplitude modulation, filtering, and artificial fast saturable absorption

An optical pulse storage ring, storing 1.76 kb of 20 Gb/s pulsed, on-off keyed, noise-generated data has been demonstrated. Stable operation is achieved using amplitude modulation, filtering, and artificial fast saturable absorption. Patterns with widely varying densities of ONEs have been stored, including patterns with all ONEs (harmonic mode-locking).<<ETX>>

50-Gbit / s optical pulse storage ring using novel rational-harmonic modulation.

50-Gbit/s, 3.8-kbit packets of optical return-to-zero data have been stored in a unidirectional fiber storage ring by use of a novel modulation scheme in which the ratio of the fundamental modulation frequency to the cavity fundamental frequency is rational (nonintegral). The modulation technique should be applicable to lasers and to soliton transmission.

All-optical storage of a 1.25 kb packet at 10 Gb/s

An all-optical pulse storage ring storing a 1.25 kb packet at 10 Gb/s is demonstrated. Optical modulation of the transmission of a semiconductor diode amplifier via cross-gain saturation provides timing stability in the ring.<<ETX>>