Katherine L. Hall

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.

Femtosecond pulse generation in a laser with a nonlinear external resonator

A simple model is presented to describe mode locking in a laser coupled to a nonlinear resonator. It reveals a new mechanism for pulse shortening and shows that shortening does not rely on dispersion in the auxiliary cavity. Experimental results are given to support the basic predictions of the model.

Architectures and technologies for high-speed optical data networks

Current optical networks are migrating to wavelength division multiplexing (WDM)-based fiber transport between traditional electronic multiplexers/demultiplexers, routers, and switches. Passive optical add-drop WDM networks have emerged but an optical data network that makes full use of the technologies of dynamic optical routing and switching exists only in experimental test-beds. This paper discusses architecture and technology issues for the design of high performance optical data networks with two classes of technologies, WDM and time division multiplexing (TDM). The WDM network architecture presented stresses WDM aware Internet protocol (IP), taking full advantage of optical reconfiguration, optical protection and restoration, traffic grooming to minimize electronics costs, and optical flow-switching for large transactions. Special attention is paid to the access network where innovative approaches to architecture may have a significant cost benefit. In the more distant future, ultrahigh-speed optical TDM networks, operating at single stream data rates of 100 Gb/s, may offer unique advantages over WDM networks. These advantages may include the ability to provide integrated services to high-end users, multiple quality-of-service (QoS) levels, and truly flexible bandwidth-on-demand. The paper gives an overview of an ultrahigh-speed TDM network architecture and describes recent key technology developments such as high-speed sources, switches, buffers, and rate converters.

Femtosecond gain dynamics in InGaAsP optical amplifiers

We have studied ultrafast gain dynamics in InGaAsP optical amplifiers by means of pump‐probe and cross‐correlation measurements using 180 fs optical pulses. The data show strong gain nonlinearities due to nonequilibrium carrier distributions and differ significantly from those observed in AlGaAs amplifiers.

Femtosecond index nonlinearities in InGaAsP optical amplifiers

We present the first femtosecond measurements of refractive index nonlinearities in diode laser amplifiers at 1.5 μm. Our results are obtained with a novel measurement technique, based on a time domain interferometer with heterodyne detection that allows the study of polarization anisotropy in the refractive index nonlinearities. We observe index changes due to carrier heating and stimulated transitions, as well as an instantaneous refractive index change similar to that observed in AlGaAs devices.

100-GHz soliton pulse train generation using soliton compression of two phase side bands from a single DFB laser

A 100-GHz soliton pulse train, with the potential of very low timing jitter, is generated using soliton compression of the beat signal between two optical carriers. The optical carriers are obtained by optically filtering out the third-order sidebands generated from a single DFB laser and a LiNbO/sub 3/ electro-optic phase modulator driven at 16.9 GHz.<<ETX>>

Femtosecond gain dynamics and saturation behavior in InGaAsP multiple quantum well optical amplifiers

Femtosecond pump‐probe experiments on InGaAs/InGaAsP multiple quantum well optical amplifiers reveal ultrafast dynamics that are similar to, but quantitatively different from, those observed in bulk amplifiers. Pulse energy saturation of the amplifier gain is also studied using 150 fs and 20 ps pulses and is found to be pulsewidth dependent. The measured saturation energies are 200 fJ and 6 pJ, respectively.

Short pulse gain saturation in InGaAsP diode laser amplifiers

The saturation behavior of InGaAsP optical amplifiers is studied for input pulsewidths of 15 ps and 150 fs. The measured output saturation energies are 150 and 40 fJ, respectively. A simple rate equation model based on pump-probe results predicts the observed pulsewidth-dependent saturation behavior.<<ETX>>

Bias‐lead monitoring of ultrafast nonlinearities in InGaAsP diode laser amplifiers

In this letter we report the first femtosecond measurements of gain and loss dynamics in InGaAsP diode laser amplifiers using optically induced changes in diode junction voltage. Our results confirm that previously observed optical pump‐probe signals are related to carrier dynamics in the active region of the amplifiers.

Chapter 2 – Nonlinearities in Active Media

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