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CLEO Report: Pick of the Papers

BALTIMORE -- CLEO 2001 -- This week's Conference on Lasers and Electro-Optics (CLEO) has seen a total of nearly 750 papers presented, which surpasses the Optical Fiber Communications (OFC) conference held in March (see OFC Report: Pick of the Papers). Unlike OFC, however, the Baltimore conference is not focused exclusively on telecommunications; optics is a key technology in many other areas, including medicine, manufacturing, and fundamental physics.

Here Light Reading offers a selection of papers that caught our attention. We picked the list ourselves, so the papers are chosen for their immediate relevance to optical networking, rather than technical merit. The basic idea is to provide a flavor of what's hot and what could influence optical components in two to five years' time. ...............................................................

CPD11 -- 106 x 10 Gbit/s, 25 GHz-spaced, 640 km DWDM transmission employing a single supercontinuum multicarrier source
H. Takara and co-workers, NTT Electronics Corp. (NEL)
This paper describes the first DWDM experiment using a broadband (supercontinuum) source, which generates all 106 channels simultaneously. The source consists of a mode-locked laser diode, an erbium-doped fiber amplifier, and a piece of polarization maintaining fiber.

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CPD12 -- High-power 1550 nm distributed feedback lasers with 440 mW CW output for telecommunications applications
R. Menna and co-workers, Princeton Lightwave Inc. (PLI)
See Princeton Lightwave Claims Laser Record.

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CPD13 -- Monolithic GaAs-based 1.3 μm VCSEL directly modulated at 10 Gbit/s
R.L. Naone and co-workers, Cielo Communications Inc.
Cielo's laser was used to transmit 10-Gbit/s signals error-free over 10 km with direct modulation (turning the laser on and off). For details see Cielo Makes a 10-Gig VCSEL.

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CMB1 -- Passively mode-locked surface-emitting semiconductor laser with >200 mW average power
R. Häring and co-workers, Institute of Quantum Electronics, Swiss Federal Institute of Technology, Zurich (ETHZ)
Mode-locking is a technique for producing pulsed sources with multi-gigahertz repetition rates. Now the Swiss team has generated peak power of 30 W, using an external saturable absorber mirror and a vertical cavity laser -- a power improvement of more than 20 times on their first attempt.

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CMD2 -- Electro-optically addressable total internal reflection switch in domain engineered lithium niobate
A.J. Boyland and co-workers, Optoelectronics Research Centre, University of Southampton
Boyland and colleagues have come up with a new way of making an optical switch in lithium niobate. They claim it could have many advantages, including a high contrast ratio, low drive voltage, and ease of manufacture. The mechanism relies on a two adjacent regions that are poled in opposite directions. When a voltage is applied, the refractive index in the two regions changes in opposite directions. If the index contrast is high enough, light hitting the boundary at an angle is internally reflected with a theoretical efficiency of 100 percent. ...............................................................

CMH3 -- Ultra-compact 90-degree bends and MMI [multimode interference] couplers in silicon-on-insulator
R.U. Ahmad and co-workers, Columbia University
Optical devices on silicon-on-insulator (SOI) can potentially be integrated into CMOS technology. Equally important, the large difference in refractive index between the silicon and the insulator can help shrink optical circuits. In this platform, the authors have made a 1x2 power splitter just 6.8 micrometers long, which they reckon could be the smallest to date.
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CTuF3 -- High efficiency narrow band holographic reflective filter for DWDM
O.M. Efimov and co-workers, Centre for Research and Education in Optics and Lasers (CREOL), University of Central Florida
Thermo-photo-refractive (TPR) glass can be used to make better Bragg gratings, because it can hold a truly three-dimensional grating, says the CREOL group. They made gratings with an absolute diffraction efficiency of 90 percent. As a bonus, the recording process uses a low dose of ultraviolet radiation, in contrast to standard fiber Bragg gratings.
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CTuH2 -- Room temperature CW operation of GaAsSb/GaAs VCSELs near 1.3 μm
F. Quochi and co-workers, Bell Labs
This is the first report of a vertical-cavity surface emitting laser (VCSEL) made from a combination of gallium arsenide with antimony that lases near 1.3 μm. Previously the longest wavelength obtained was 1.23 μm. The maximum output power was about 0.2 milliWatts.

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CTuL2 -- Micro-mechanically electrostatically actuated optical switch for NxN cross connect array
I. Shubin and co-workers, Centre for Research and Education in Optics and Lasers (CREOL), University of Central Florida
Shubin's switch is made from silicon-oxynitride (SiON) waveguides in two layers, one on top of the other. At the switch position, the waveguides are suspended on a cantilever structure. When the switch is actuated, by applying a voltage, the cantilever is pulled down so that the lower waveguide on the input side now aligns with the upper waveguide on the output side. It takes 25 V to energize the switch, and the switching speed is 90 microseconds.

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CTuM45 -- High repetition rate flat-topped pulse trains from an arrayed waveguide grating
D.E. Leaird and co-workers, Purdue University, Bell Labs and NTT Photonics Laboratories
A new use for an AWG. When a short pulse is fired into an AWG, a burst of 21 shorter pulses comes out the other end. It's an important step towards making a pulsed source capable of more than 500 GHz.

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CThH7 -- A multi-level subcarrier modulation technique for 10 Gbit/s installed base multimode fiber links
M. Webster and co-workers, University of Bristol
When 10-gigabit Ethernet comes along, it won't reach very far over existing multimode fiber. Standard signalling methods will limit transmission distance to just 50 meters. Webster's team has demonstrated a technique that pushes 10-gig signals out to 300 m using both multilevel signalling and subcarrier multiplexing.

— Pauline Rigby, Senior Editor, Light Reading, http://www.lightreading.com

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