Advanced Telecom Technologies and Mid-Infrared Lasers & Applications

Wednesday, April 28, 2004
7:00 PM
Free and open to the public

This talk will briefly describe three on-going projects in my laboratory at the University of Michigan. The first project is on optical switching cores for 100Tb/s routers. Routers are rapidly becoming the bottleneck for high-speed and high-capacity backbone IP networks, and a key enabler would be an optical switching core that connects racks of line cards with minimum scheduling complexity. Wavelength division multiplexed (WDM) technologies can be used to construct optical switching cores that will be lower in cost, size and power dissipation than their electronic counterparts. The switching fabric is based on using a broadcast and select switch with tunable filters. The fabric could be a star coupler with fiber leads, while the filters could be arrays of MEMS Fabry-Perot devices or electro-optic multi-layer devices.

The second project is on secure communications in all-optical networks. With the distance between regenerators expanding and many WDM channels in parallel on optical fibers, new sources of vulnerability arise for information assurance and system survivability in all-optical networks. Raman amplified systems and novel modulation formats can mitigate many of the new sources of vulnerability. The typical pump power and optical spectrum monitoring used with Raman amplification can detect tapping along the length of the system. In addition, the fundamental physics of Raman amplifiers allow them to minimize service disruption. Moreover, the use of constant intensity modulation schemes, such as polarization shift keying, can reduce the eavesdropping between wavelengths through fiber nonlinearities.

Finally, a third thrust of our work is on developing mid-infrared lasers for wavelengths between ~ 2 to 6.5 microns based on cascaded Raman wavelength shifting. The laser leverages mature technology in the telecom window, and then builds a bridge using Raman shifting in chalcogenide or fluoride fibers to the mid-infrared. The mid-infrared laser can serve as a platform for a number of applications including chemical sensing, combustion monitoring, infrared countermeasures, selective laser ablation in neurosurgery and advanced semiconductor process control. To illustrate, the last application will be described, where the mid-infrared lasers are used to monitor the etching in the process chamber. The poly-gate etching can be monitored by observing the concentration of HCl or HBr, while the dielectric etching for contact holes can be monitored by observing the concentration of various CxFy compounds.

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Mohammed Islam

University of Michigan