In the last year, the tunable extinction ratio of dual-parallel Mach-Zehnder (DPMZM) modulator has been experimentally demonstrated. The working parameter of DPMZM can be measured by the characterization method. Precise bias control can be applied on MZMs to compensate the power imbalance of sub MZMs. Under this bias state, the extinction ratio can be enhanced and a typical two-tone signal. The outcome of this research is summarized in a preparing manuscript and will be submitted to IEEE Access.

Based on the proposed method, the application related to opto-electronic oscillator (OEO) can be investigated. The target of this research is to enhance the extinction ratio (ER) of the optical modulator used inside the OEO and investigate the performance improvement of the entire OEO. By improving the performance of the OEO, we aim to reduce the gain of the electric amplifier used inside the OEO, and eventually realize a low-cost OEO without the electric amplifier.

The theoretical background of OEO has also been reviewed. The most famous theory of OEO is the Yao and Maleki model. According to Yao and Melaki model, in order to reduce the gain of the electrical amplifier while maintaining the overall voltage gain, it is necessary to increase the optical amplification of the EDFA and improve the extinction ratio of the modulator. A serious of experiments has been established to verify this issue. The next step is to realize the close loop of OEO without electrical amplifier consider the suppression of phase noise. This work is support by the funding from Grant-in-aid for transformative research areas A“Photonic Computing” (JSPS KAKENHI Grant Number JP22H05196).

Another application based on precise measurement of DPMZM is real-time RF phase measurement using single sideband modulation of Mach-Zehnder modulators.  In this method, the phase measurement results can be derived from the ratio of the 1st order and -1st order sidebands, meaning the measurement of two data points. Moreover, the measurement method was experimentally demonstrated, and the calculation was conducted using a field-programmable gate array (FPGA) in the electrical signal domain. This type of measurement technique will be useful for key technologies, such as beamforming, thereby supporting the future beyond 5G networks. The outcome of this research has been accepted as oral presentation by the 29th Opto-Electronics and Communications Conference 2024 (OECC2024).