High-speed Mach-Zehnder Modulator Research Articles

Compact, High-Speed Mach-Zehnder Modulator With On-Chip Linear Drivers in Photonic BiCMOS Technology

Compact, High-Speed Mach-Zehnder Modulator With On-Chip Linear Drivers in Photonic BiCMOS Technology

Optimizations of thermo-optic phase shifter heaters using doped silicon heaters in Rib waveguide structure

Thermo-optic phase shifter (TOPS) based on doped silicon (Si) heaters is commonly used to compensate for device structure imbalance of high-speed Mach-Zehnder modulator (MZM) due to fabrication errors. However, this functionality required more electrical power for setting the MZM to be active around the linear transfer function at π/2 phase shift. To solve this issue, we proposed an optimal design of doped Si heaters using the standard commercial 220 nm Si layer in rib waveguide structure which can improve the electrical energy efficiency and reduce optical losses. Numerical simulations and optimizations were carried out on the key parameters, heater locations, doping concentration, etching depth, and laser wavelength drift. Results show that the optimal design has a low power consumption of 19.1 mW for obtaining a phase shift of π with a good time constant of 2.47 µs and low optical losses of 2.37 dB/cm at the 1550 nm operated wavelength. Thus, an excellent figure of merit (FOM) of 47.2 mWµs is obtained for the optimal design. Also, the proposed device has good stability to the laser wavelength drift effect in the C-band range. This TOPS can be very useful for improving the transmitter system performances based on high-speed MZM technology.

Optical Pulse-Drive for the Pulse-Driven AC Josephson Voltage Standard

We developed an optical pulse-drive for the operation of the Josephson Arbitrary Waveform Synthesizer (JAWS) using a fast photodiode (PD) operated at 4 K, close to the JAWS chip. The optical pulses are transmitted to the PD by an easily removable optical fiber attached to it. A bare-lensed PD is mounted by flip-chip technique to a custom-made silicon-carrier chip. This carrier chip is equipped with coplanar waveguides to transmit the electrical pulses from the PD to the JAWS chip mounted on a separate printed circtuit board (PCB). The main components of this optical setup are a laser source, a high-speed Mach–Zehnder modulator, and the modulator driver. The waveform pattern is supplied by a commercial pulse pattern generator providing up to 15 GHz electrical return-to-zero (RTZ)-pulses. Unipolar sinusoidal waveforms were synthesized. Using a JAWS array with 3000 junctions, an effective output voltage of 6.6 mV root mean square (RMS) at the maximum available clock-frequency of 15 GHz was achieved. Higher harmonics were suppressed by more than 90 dBc at laser-bias operation margins of more than 1 mA.

Calibration-free measurement of high-speed Mach-Zehnder modulator based on low-frequency detection.

A calibration-free electrical method is demonstrated for measuring the frequency response of high-speed Mach-Zehnder modulators (MZMs) based on low-frequency detection. The method achieves the high-frequency modulation index and half-wave voltage measurement of MZMs by the low-frequency electrical spectrum analysis of the two-tone and bias-modulated optical signal. Moreover, it eliminates the need for correcting the responsivity fluctuation in the photodetector through setting a specific frequency relationship between the two-tone and bias modulation. Both absolute and relative frequency response of MZMs are experimentally measured with our method and compared with those obtained with conventional methods to check for consistency.

Distributed electrode Mach-Zehnder modulator with double-pass phase shifters and integrated inductors.

A novel high-speed Mach-Zehnder modulator (MZM) fully integrated into a 90 nm CMOS process is presented. The MZM features 'double-pass' optical phase shifter segments, and the first use of integrated inductors in a 'velocity-matched' distributed-electrode configuration.

Integrated Lithium Niobate Mach-Zehnder Interferometers for Advanced Modulation Formats

We present recent progress of high-speed Mach-Zehnder modulator technologies for advanced modulation formats. Multi-level quadrature amplitude modulation signal can be synthesized by using parallel Mach-Zehnder modulators. We can generate complicated multi-level optical signals from binary data streams, where binary modulated signals are vectorially summed in optical circuits. Frequency response of each Mach-Zehnder interferometer is also very important to achieve high-speed signals. We can enhance the bandwidth of the response, with thin substrate. 87 Gbaud modulation was demonstrated with a dual-parallel Mach-Zehnder modulator.

Cost-effective and dispersion-tolerant cascade modulation for millimeter-wave-over-fiber applications

In millimeter-wave-over-fiber (MWoF) feeder systems, the received millimeter-wave signals at the remote antennas (RAs) can suffer from signal fading by chromatic dispersion of optical fiber. This can be substantially mitigated by Mach–Zehnder modulator (MZM) based photonic up-conversion technique. In this technique, the data signals at intermediate frequency (IF) are frequency up-converted to millimeter-wave frequency by an MZM biased at its transmission null point. However, this scheme requires a costly, high-speed MZM, which will hinder the widespread of this technique for cost-sensitive MWoF applications. Hence, we propose and demonstrate a cost-effective way of reducing the cost of MWoF optical transmitters based on photonic up-conversion technique. We employ a dual wavelength source composed of a directly modulated laser and a polarimetric filter. This source is used to generate a millimeter-wave tone signal and to frequency up-convert the IF data signals to millimeter-wave frequency. The dual wavelength source is also shared with numerous RAs for further cost reduction. Our experimental demonstration performed with 30Msymbol/s 16-quadrature amplitude modulation signals shows that we can transmit the 20GHz millimeter-wave signals over 25km standard single-mode fiber without any transmission penalty.