Raman Amps: Key to Optical Future

Raman amplifiers, which use specialized pump lasers to increase the power of light signals on optical fiber, will help transform the market for long-haul and metro gear within the next three years.

So says a report titled "Optical Amplifiers: Raman, EDFA, EDWA, and SOA," published by Strategies Unlimited. The report describes how demand for new optical applications has pushed Raman amps into the spotlight. This trend, the report states, will help boost the growth of Raman amp worldwide revenues more than 170 percent by 2004, when Raman amps will represent nearly half of the total $7.3 billion of amp market revenues. (Today, the firm says, Raman comprises about 6 percent of a $3.3 billion amplifier market.) "Raman's been in development for years. But its use is speeding up now. Manufacturers think that for 40-Gbit/s apps, you've got to have Raman. For ultralong haul, you've got to have Raman," says Tom Hausken, Strategies Unlimited senior analyst and author of the report.

Up to now, most optical networking gear has relied on erbium-doped fiber amplifiers (EDFAs) for amplification. EDFAs use specially treated fiber, packed with a pump laser inside a small box that's spliced into the network fiber itself, to boost signals every few meters. But carriers' growing demand for multichannel DWDM (dense wavelength-division multiplexing) over ever greater distances has led component makers to turn to Raman amps for a boost of up to 100 kilometers.

These companies are creating hybrid amps in which the pump lasers of Raman amps are glommed onto the pre-amp portion of the EDFA. This results in a powerful amp that's cheaper to put into products than two separate amplifiers, particularly for metropolitan area network gear that still use EDFAs but require long-haul connectivity to edge devices.

"There's no reason these amplifiers can't be put into the same box, and it's happening now," says Hausken. "Raman and EDFA components will become virtually indistinguishable."

The emphasis on Raman tallies with other research (see CIBC Bullish on Raman). But the report says other amplifiers are on the rise, such as erbium doped waveguide amplifiers, in which a substrate instead of a fiber is doped with a special substance to boost light signals. Also growing in popularity are semiconductor optical amplifiers (SOAs), which are already appearing in some startups' prototypes (see Ultra Fast Optical Systems Inc.).

-- Mary Jander, senior editor, Light Reading http://www.lightreading.com