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Technology Stocks : Spectran (SPTR)...Speaking of White Hot Lately -- Ignore unavailable to you. Want to Upgrade?

To: William D. Ivancic who wrote (1078)	3/27/1998 10:28:00 AM
From: Grant Lu	Read Replies (1) \| Respond to of 1147

LEAF fiber: Single mode optical fiber can operate at two wavelengths, 1310 and 1550 nm. 1310 was used first and the fiber is referred to as "standard single mode". This wavelength was used first because silica glass has "zero dispersion" naturally at 1310 nm; dispersion refers to the tendency of different wavelengths to travel at different speeds. Although ideally each pulse is a single wavelength only, in reality, each pulse contains a spread of wavelengths. As the pulse propagates down the fiber, the pulse broadens due to dispersion. Hence, it is necessary to have low dispersion. The problem with 1310 is that it is not the wavelength with the lowest attenuation so amplifiers are needed more often with 1310 systems. The second type of fiber is called "dispersion shifted fiber" which operates at 1550 nm where the lowest attenuation occurs. Manufacturers were able to design the fiber so that the zero dispersion wavelength was shifted from 1310 to 1550 nm. This is all old history. The new development is WDM (aka DWDM) which is wavelength division multiplexing. Instead of sending a train of pulses which all have the same wavelength down the fiber, the system can now send simultaneous trains of pulses, all with different wavelengths. So instead of using one wavelength, 8, 16 or 40 wavelengths can be transmitted simultaneously with the corresponding increase in capacity. WDM is a huge development and is worth billions in sales to all of the system and component companies. There are technical problems with applying WDM to conventional 1310 and 1550 fiber, although it can be done. However, the best long term solution is to use "non zero dispersion shifted fiber" (NZDF). Lucent has been very successful in offering their product, TrueWave. Corning has also had a product called LS. LEAF is a new version of NZDF. It permits somewhat greater spacing between amplifiers but cannot allow as many channels as TrueWave. Currently, only Lucent and Corning have NZDF. This fiber is about twice the price of standard fiber. I believe that competition in this area will remain limited because of patents from Lucent and Corning.