Masaaki Kawai

Smart optical receiver with automatic decision threshold setting and retiming phase alignment

The requirements for a smart optical receiver are discussed, and a design architecture suitable for introducing ICs based on automatic decision threshold setting and retiming phase alignment using digital/analog signal processing feedback is proposed. With the proposed architecture, the decision threshold level and the retiming clock phase of received data in the decision circuit are automatically adjusted to the optimum position. This obviates the need for decision threshold level and retiming clock phase adjustments in production testing, and it reduces the power penalty (receiver sensitivity degradation) on the received optical waveform variation. The power penalty caused by temperature and supply-voltage variations and aging in installation is also reduced. The performance of the proposed architecture is estimated; the power penalty as compared with the manual optimum adjustment is less than 0.4 dB, and the robustness to avalanche photodiode multiplication factor variations and crosstalk are improved. >

Advanced LiNbO/sub 3/ optical modulators for broadband optical communications

This paper describes advanced lithium niobate (LiNbO3) optical modulators for broadband optical communications. It includes 40-Gb/s ultralow voltage modulators, compact modulators and modulators for frequency comb generator and short pulse generation

Spatial Light Phase Modulator With Bidirectional Tilt–Piston Micromirror Array—Part II: Fabrication and Experiment

In part I of this paper, we have proposed a novel structure of microelectromechanical-systems-based 1-D spatial light phase modulator (SLPM). We have discussed the design of the device and derived the optimum parameters to satisfy the target specifications. In part II, we focus on the fabrication process and experimental results of the device. We show that this device configuration allows us to use a simple fabrication process. We fabricated the device consisted of 24 micromirrors and realized the tilt and piston motions successfully. The measured dc (rotation angle and displacement on driving voltage) and ac (frequency response) characteristics matched well to the simulated data derived in part I. We also examined the distribution of the resonant frequencies over 24 micromirrors and verified that the variance was kept within 2%. As one of the applications of the device, we applied the device to optical beam shaping and succeeded in shaping the optical beam properly depending on the surface patterns of the SLPM. With these achievements, we show that the device can be adopted to a wide variety of applications in optical communication systems and optical signal processing.

Suppression of thermal drift in an ultra-high-speed LiNbO 3 optical modulator

We have succeeded in suppressing the thermal drift of an ultra-high-speed LiNb03 optical modulator by using domain inversion. This low thermal drift modulator can be used by a low-voltage, low-cost bias source.

Novel Spatial Light Phase Modulator with Bidirectional Tilt-Pistonmicromirror Array

We have proposed a novel structure of one dimensional spatial light phase modulator (SLPM) that consists of a micromirror array on an SOI wafer and ITO (Indium Tin Oxide) electrodes on a glass plate. Each micromirror can exhibit bidirectional single-axis rotation, as well as up- and down- translation motion. We have fabricated the device, and confirmed its motion experimentally.

Spatial Light Phase Modulator With Bidirectional Tilt–Piston Micromirror Array—Part I: Principle and Design

This paper proposes a novel structure of microelectromechanical-systems-based 1-D spatial light phase modulator (SLPM) that consists of a micromirror array on a silicon-on-insulator (SOI) wafer and indium tin oxide (ITO) electrodes on a glass plate. Each micromirror can exhibit bidirectional single-axis tilt, as well as up-and-down piston motions by combining the applied voltage on two ITO electrodes placed over the micromirror and the substrate of SOI (in the case that the substrate is energized, all micromirrors go down simultaneously). This device configuration enables SLPM to be fabricated by a simple process. Part I of this paper focuses on the principles and the design of the device. The optimum parameters of the device are derived to realize both tilt and piston motions, considering ways to reduce mirror warpage and crosstalk from the ITO electrode from the adjacent mirror. We simulate the dc and ac characteristics of the device and confirm that the designs that we optimized satisfy the target specifications to be widely used in optical communication systems.

Optical beam shaping by spatial light phase modulator with bidirectional tilt-piston micromirror array

We have succeeded in controlling the optical beam profile by MEMS spatial light phase modulator experimentally. The modulator proposed by our group has 1-D array of bidirectional tilt-piston micromirrors driven by electrostatic force.

Optical switching technologies for optical routing

We developed the optical switching technologies of 3-dimentional micro-electro mechanical system switch, acousto-optic tunable filter, PLZT electro-optics deflector switch, and optical parametrically amplified fiber switch. We evaluated their potentials for application to photonic networks based on their optical switch characteristics.