Gain control in double-pass L-band EDFA using a ring resonator and two-stage configuration
Abstract:A gain-clamped double-pass long wavelength band erbium-doped fiber amplifier with high clamped-gain and low noise figure is demonstrated using a ring laser. The optical circulator is used at output end of the amplifier to retro-pass the test signal back into the system for enhanced gain. A length of forward pumped erbium-doped fiber is incorporated in front of the double-pass amplifier to achieve a low noise figure. The gain clamping is achieved by routing the backward amplified spontaneous emission into the feedback loop via optical circulator and C/L-band wavelength selective coupler to create a ring laser, which operates outside the L-band region. The gain is clamped at 10.6 dB for all input signal powers from –40 dBm to –4 dBm with a gain variation of less than ±0.4 dB, when the variable optical attenuator (VOA) is set at 0 dB. The clamped-gain level can be tuned from 10.6 to 21.6 dB by varying the VOA settings from 0 to 12 dB. The corresponding noise figure varies from 9.1 to 5.2 dB.
Document Type: Research Article
Affiliations: Photonics Laboratory, Department of Physics, University of Malaya, 50603 Kuala Lumpur, Malaysia
Publication date: 2004-12-01