Effect of chip area limitation on gain and noise of erbium-doped waveguide amplifiers

Gain and noise of spiral erbium-doped waveguide amplifiers (EDWAs), arranged at a limited chip area, are studied employing a rate-propagation equation model that takes into account bend-induced losses. Performances of the limited area spiral EDWAs are compared to those of the straight EDWAs, with the same parameters. It is shown that dense spirals with small bend radii are required in order to extract the maximal gain from an assigned chip area. This gain maximum is considerably smaller than the gain of the corresponding straight EDWA and depends on the chip area value. Optimal design parameters are obtained. The effect of amplified spontaneous emission along with gain degradation on the noise figure in the limited area spiral EDWAs is analyzed. It is found that the dependence of the optimized limited area EDWA noise figure on the chip area attains a maximum at some definite area value. It is also found that there is a range of areas, where the optimized limited area EDWA noise figure is subjected to pronounced changes under small variations of the chip area.