Corrections to "Technique for suppression of pattern dependence in a semiconductor-optical-amplifier wavelength converter"

When a semiconductor-optical amplifier (SOA) wavelength converter is operated at high bit rates, the converted output can be degraded by pattern dependence; the amplitude of 1´s and 0´s depend on the pattern that preceded them. This is caused by the slow gain recovery time of the amplifier. In the above-named letter [ibid., vol. 9, pp. 1583??1585, Dec. 1997], the authors showed that passing the corrupted data through an optical filter whose transmission varies linearly with frequency sharpens the transitions between the bits and removes pattern dependence. Here, they correct inconsistencies in our statements1 regarding the required sign of the slope of the filter.