Analog performance of an all-optical ultrafast wavelength converter is measured and reported for the first time. The wavelength-conversion process is based on nonlinear cross-phase modulation in an optical fiber combined with an optical filter to convert phase modulation to amplitude modulation. The spurious-free dynamic-range (SFDR) of the converter is measured to be 82 dB . Hz(2/3). We define a new metric called the SFDR power penalty, which measures the degradation in SFDR relative to baseline the back-to-back analog optical link. The SFDR power penalty was measured to be 5 dB. Hz(2/3) and is shown to be a function of the input optical power. This metric is used to characterize the linear region of the optical wavelength converter.