Mixing EDFAs and Raman amplifiers improves long-haul transmission

April 1, 2000

Neil Savage

Wavelength-division multiplexing is rapidly moving to 10-Gbit/s modulation per wavelength. Increasing the number of wavelengths, however, makes reduction of the signal-to-noise ratio (SNR) and equalization of the optical amplifier gain important. Using Raman amplification in long-haul transmission has been shown to improve SNR, but the technique requires high pump power. Raman amplifiers also exhibit low gain compression and can cause performance of the system to become unstable. Researchers at Alcatel Submarine Networks (Clichy, France) have found that combining a 980-nm-pumped erbium-doped fiber amplifier (EDFA) with a Raman amplifier gives both an improvement in SNR and the high gain compression and output power common to EDFAs.

In their experiment, the researchers looked at 32 wavelengths with an amplifier output power of +10 dBm. To test a hybrid amplifier system, researchers built a 501-km-long recirculating loop composed of optical amplifiers spaced 45 km apart with a 10.5-dB span loss (see figure). When turned on, the Raman stage provides 100 mW of pump power. With a 4-dB Raman gain, the researchers saw 1.3-dB improvement. When taking into account an improvement of 0.2 dB without Raman gain while increasing output power from +10 to +11 dBm, and considering a 0.4-dB insertion loss from the 1450-nm multiplexer, the net improvement with the hybrid amplifier was 0.7 dB. For more information, contact Olivier Gautheron at olivier. [email protected].

Sponsored Recommendations

March 12, 2025
Join us for an engaging discussion with industry experts on the intersection of AI and optics. Moderated by Sean Buckley, editor-in-chief of Lightwave+BTR, this panel will explore...
March 25, 2025
Explore how government initiatives and industry innovations are transforming rural broadband deployments, overcoming cost and logistical challenges to connect underserved areas...
April 9, 2025
As transceiver speeds increase, so do thermal challenges. Discover key insights into innovative cooling solutions that ensure optimal performance and reliability.
March 7, 2025
In today’s hyperconnected world, rolling out and managing profitable, high-performance networks for access and transport will require innovative architectural approaches. The ...