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News and comments on community broadband networks, the communities deploying them and the technologies that support them. Published by Denise Frey and Al Bonnyman.

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Tuesday, February 03, 2004


Corning licenses key OFS fiber patent

Corning has been making a "low water peak" fiber (SMF-28e) for a while, but its' optical attenuation in the E-band (1360-1460 nanometers) has been higher than that of OFS's AllWave fiber, a "zero water peak" fiber. Now Corning has licensed the rights to use OFS technology covered by its' U.S. and foreign patents on zero water peak fiber.

Traditionally, trace impurities in the glass when making fiber caused high attenuations (known as the "water peak" across the E-band), making fibers effectively unusable at these wavelengths. The OFS patent covers any fiber for which the attenuation at 1385 nm is less than that at 1310 nm. (A "low water peak" fiber has slightly higher attenuation at 1385 nm. than at 1310 nm.)

Only low (or even better, zero) water peak fibers allow utilities to make full use of all the wavelengths available to a CWDM (coarse wavelength division multiplexing) system.

It's unclear whether Corning will extend the use of its' SMF-28e designation to zero water peak fibers or if it will use another designation.

I don't recommend buying any singlemode fiber that is not low or zero water peak.

If the fiber is zero water peak, users should make sure that the vendor is an OFS licensee (or else obtain a written agreement to defend the user against patent infringement claims). While I'm no patent attorney, the OFS fiber appears to cover the use of zero water peak fiber in a CWDM system and not just the manufacture of such a fiber.


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