Linearized fiber-optic link with a high spurious free dynamic range over a wide frequency range

An all-optical linearized fiber-optic link is presented. It solves the problem in most reported structures where a high spurious free dynamic range (SFDR) can only be obtained in a limited frequency range. The link only involves a laser, an optical modulator, and a photodetector. The novel design in the modulator bias setting enables the third-order intermodulation distortion to be suppressed by controlling only one bias voltage of a dual-parallel Mach–Zehnder modulator (DPMZM) while the other two bias voltages are set to bias the sub-MZM and the main MZM of the DPMZM at the standard peak and null point, respectively. The link has a very simple structure and does not require any electrical component, and hence a high SFDR can be obtained over a wide frequency range. Techniques are proposed using off-the-shelf components for stabilizing the modulator bias setting to maintain high SFDR performance when the link is operated in practice. Measured results demonstrate a high SFDR of 120.5 dBHz ⁴ ∕ ⁵ 1.6 dB over a 2–20 GHz frequency range in an unamplified linearized fiber-optic link. To our knowledge, this is the first report of a linearized fiber-optic link with around 120 dBHz ⁴ ∕ ⁵ over such a wide frequency range.