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Technology Stocks : Semi Equipment Analysis -- Ignore unavailable to you. Want to Upgrade?

To: robert b furman who wrote (3278)	5/24/2002 8:40:07 PM
From: Crossy	Read Replies (2) \| Respond to of 95622

Robert, sorry but I think that tunability and modulation is not directly related. The only relation is that a "modulator" is needed in any laser, also in a tunable laser. The question now is which method to use, what "material system" to use for modulation. In the past, Li-NbO was used (Lithium-Niobate). The huge disadvantage is the high bias voltage (>100V) needed to drive such a modulator at 40Gbit/sec. The voltage requirement increases with speed. Other "crystal property" types of modulators using Rutile and Garnet are being tested. What is already on the market is an "electro-absorption" modulator based on InP, which has a way lower bias voltage requirement. For the future, maybe a move to polymer-modulators will take place but that is just one of the options, albeit a good bet. For shorter distances (metro), "direct modulation" is usually applied, where the modulation is done in "electrics" instead of optics. This has disadvantages (called "chirp") in the form of quicker signal degradation and shorter spans.. rgrds CROSSY