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A novel, compact, and tunable lithium niobate (LN) planar waveguide loop structure composed of two Y junction reflectors is proposed for optical and radio frequency signal processing applications. The preliminary device shows a high quality factor of 6.5 x 10(4), due to the low propagation loss of the titanium-diffused LN waveguide. The tunability of the loop by electric field is estimated.

We propose and demonstrate a reconfigurable multilevel transmitter using a monolithically-integrated quad Mach-Zehnder in-phase/quadrature (QMZ-IQ) modulator with binary driving electronics. Different from previous parallel-integrated quadrature amplitude modulation (QAM) transmitter solutions, only one electrode is required to adjust the relative phase offset among embedded sub-Mach-Zehnder modulators in the proposed IQ superstructure. By feeding different RF driving electronics and operating the integrated modulator as different bias conditions, different advanced multilevel modulation formats, such as QAM and 8-ary phase-shift keying (8-PSK), could be synthesized. In this paper, a 40-Gb/s 16-QAM and a 30-Gb/s 8-PSK are generated using the proposed multilevel transmitter, respectively. Offline digital processing is employed for bit-error rates estimation and constellation reconstruction.

We investigated an integrated optical modulator consisting of two Mach-Zehnder interferometers. The modulator can generate optical signals in various types of modulation formats, which have advantages for long-haul transmission, optical labeling, etc. By using a fabricated versatile optical modulator having traveling-wave electrodes designed for high-speed signals, we demonstrated generation of optical 40Gb/s frequency-shift-keying signals, which can be demodulated by an optical filter. 80Gb/s optical differential quadrature-shift-keying modulation was also demonstrated, where 40Gb/s in-phase and quadrature data were, simultaneously, fed to the modulator.