Measuring the Chirp and the Linewidth Enhancement Factor of Optoelectronic Devices with a Mach–Zehnder Interferometer

In this paper, a technique based on the use of a Mach-Zehnder (MZ) interferometer is proposed to evaluate chirp properties, as well as the linewidth enhancement factor (_αH-factor) of optoelectronic devices. When the device is modulated, this experimental setup allows the extraction of the component´s response of amplitude modulation (AM) and frequency modulation (FM) that can be used to obtain the value of the _αH-factor. As compared with other techniques, the proposed method gives also the sign of the _αH-factor without requiring any fitting parameters and, thus, is a reliable tool, which can be used for the characterization of high-speed properties of semiconductor diode lasers and electroabsorption modulators. A comparison with the widely accepted fiber transfer function method is also performed with very good agreement.