Nonlinear Effects in Semiconductor Optical Amplifiers,
Abstract
A traveling-wave semi-conductor laser amplifier (TWA) 1-4 can greatly simplify optical repeaters used in wavelength-division-multiplexed (WDM) systems, since its wide gain bandwidth width allows a single TWA to simultaneously amplify signals of different wavelengths. Even though such system performance in the linear gain regime is determined only by amplifier noise properties 5,6, the onset of nonlinear effects in optical amplifiers result in crosstalk 7. Nonlinear effects in optical amplifiers have opposite aspects; (1) unfavorable for linear amplifications where any nonlinearity impairs the performance and should be avoided, but (2) favorable for highly efficient nonlinear operation 8,9 due to a large optical gain compared with passive/absorptive nonlinear materials. Two significant nonlinear effects are signal gain saturation 10 occurring for a large input signal and nearly degenerate four-wave mixing (NDFWM) 11,12 occurring for multifrequency input signals, as summarized in Fig. 1 (13). The dominant nonlinearity in the semiconductor laser amplifiers (SLAs) restilts from changes in the injected-carrier density as a result of signal amplification. Signal gain saturation arises from the reduction in DC carrier component ndc, while the NDFWM is attributed to the generation of a carrier beat, component n omega at beat frequency omega.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 22, 1992
- Accession Number
- ADP007001
Entities
People
- Tadashi Saitoh
- Takaaki Mukai
Organizations
- NTT, Inc.