Super-linear modulator with extended bandwidth capability for broadband access applications

Ultra-linear modulators are critical components for broadband access applications in analog fiber-optic communication links, such as Radio-over-Fiber (RoF), Radio-over-Free Space (RoFS) and ultra-dense (cable television) CATV. In our previous work, it was shown that an ultra-linear optical modulator - composed of a phase modulator and ring resonator in a Mach-Zehnder (MZ) configuration, exhibited SFDR values > 130 dB. In this paper, we introduce a new configuration based on a lumped electrode design, in which the phase modulator (PM) is on one arm of the MZ and the ring resonator (RR) is located on the other arm. We also carefully control and monitor the power split ratio of an RF input to both the PM and the RR, in addition to the RF phase bias between the RR and PM. We report its unique and superior features such as superior linearity (SFDR ~ 133 dB), modulation bandwidth extension (as much as 70%) over the ring resonator-assisted Mach Zehnder design and high link gain. Lastly, we discuss the merits of the design flexibility, practicality and ease of use of the new modulator.