Leonard J. P. Ketelsen

Assessment and modeling of aging in electro-absorption distributed Bragg reflector lasers

We describe a protocol for assessing aging in the tuning section of a multisection distributed Bragg reflector laser integrated with amplifier, tap coupler, and electro-absorption modulator. Under accelerated aging, we observe a transient change of nonradiative recombination followed by saturation. A simple model of aging of the Bragg section of the tunable lasers enables prediction of changes in each wavelength channel using information obtained from a single channel only.

Characterizing residual reflections within semiconductor lasers, integrated sources, and coupling optics

We describe a method for analyzing reflections within or near semiconductor lasers and more complicated integrated sources. Through Fourier transformation of an optical spectrum from the wavevector to the length domain, reflections are analyzed for strength, round-trip path length, and current or voltage dependence. Identification of reflections from within semiconductor lasers, integrated electro-absorption modulated lasers, and from coupling optics is presented. Spatial resolution in InP of /spl sim/5 /spl mu/m with over two orders of magnitude in dynamic range is demonstrated. Inverse transformation of a spatially resolved feature in a transformed reflection spectrum provides an optical spectrum due to that individual feature of sufficient resolution to study wavelength dependence, for example, of coatings and gratings.

Experimental demonstration of composite packet switching on a WDM photonic slot routing network

We propose photonic slot routing ring networks that use a novel packet stacking technique to add/drop packets, which are simultaneously time and wavelength division multiplexed. Packet stacking, routing, and unstacking with four wavelengths was successfully demonstrated.

Experimental demonstration of composite-packet-switched WDM network

We propose and demonstrate experimentally a novel technique for packet switching on a ring network. We use the wavelength dimension to increase the transmission line rate and a novel packet-stacking technique to add/drop packets. Packet stacking is used for transport rate multiplication and for equal loading of wavelengths on the physical layer. Packet stacking, switching, and unstacking have been successfully demonstrated on a four-node hubbed ring network serving five source-destination pairs on four wavelengths. Each wavelength was running at 1-Gb/s bit rate.

Composite packet switched WDM networks

We proposed and successfully demonstrated a novel high connectivity composite packet switching system using a single tunable laser source and passive optical components at each node. This could become an economical solution for networks that require high connectivity and packet switching. Photonic slot routing schemes could not only be useful for local area networks but also be an economically viable solution for interconnecting large router farms.

Identifying sources of residual reflections within integrated electroabsorption modulated laser cavities

Integrated electroabsorption modulated lasers (EMLs) are designed for use in high bit-rate 1550-nm fiber-optic communication systems in which the dispersion penalty incurred using directly modulated distributed feedback (DFB) lasers is judged unacceptably high. A critical system parameter is the total frequency chirp exhibited by the EML source under digital modulation, typically at 2.5 or 10 GBit/s. Frequency chirp in an EML arises from the electro-optic effect in the modulator, electrical cross talk between modulator and laser sections and from reflected optical power, which re-enters and perturbs the DFB laser section after undergoing modulation.