Nobuhiro Kikuchi

80-Gb/s Low-Driving-Voltage InP DQPSK Modulator With an n-p-i-n Structure

We present a traveling-wave-electrode InP-based differential quadrature phase-shift keying modulator with a novel n-p-i-n waveguide structure. The structure features low electrical and optical propagation losses, which allow the modulator to operate at a high bit rate together with a low driving voltage and a low insertion loss. We successfully demonstrate 80-Gb/s modulation with a driving voltage of only 3 Vpp in a push-pull configuration. The chip size is just 7.5 mm times 1.3 mm.

Monolithically integrated 100-channel WDM channel selector employing low-crosstalk AWG

A 100-channel wavelength-division-multiplexing channel selector monolithically integrated on an InP substrate is demonstrated. The selector consists of two arrayed waveguide gratings (AWGs), two semiconductor-optical-amplifier (SOA)-gate arrays, and a multimode interference coupler. The selector employs improved AWGs whose crosstalk is reduced with higher order mode filters. Successful channel selection and lossless operation for all channels are achieved. Error-free operation at 10 Gb/s and small sensitivity penalties between 1.8 and 3.3 dB are obtained.

High-Speed InP-Based Mach-Zehnder Modulator for Advanced Modulation Formats

We present a traveling-wave-electrode InP-based Mach-Zehnder (MZ) modulator that employs an n-p-i-n waveguide structure. The structure provides low electrical and optical propagation losses, which enables the modulator to operate at a high baud rate with a low driving voltage and a low optical insertion loss. We developed a compact 40-Gb/s differential phase shift keying (DPSK) tunable wavelength transmitter module, which incorporates a full C-band tunable laser and the MZ modulator in one package. The RF driving voltage for the MZ modulator is 3 Vpp in a push-pull drive configuration. Using the same design for the MZ modulator, we also developed a differential quadrature phase shift keying (DQPSK) modulator or optical IQ modulator, and acheived 80-Gb/s DQPSK modulation. Furthermore, we fabricated a compact dual-polarization (DP) QPSK modulator by using the hybrid integration of an InP twin-IQ modulator and a planar lightwave circuit (PLC) polarization multiplexing circuit (PMC). We successfully demonstrated 112-Gbit/s DP-QPSK signal generation.

Full C-Band Tunable DFB Laser Array Copackaged With InP Mach–Zehnder Modulator for DWDM Optical Communication Systems

We fabricated a compact 10-Gb/s-wavelength tunable laser module by integrating a tunable DFB laser array and an InP-based n-i-n Mach-Zehnder modulator in one package. We developed a multichip assembly technology to realize high optical coupling efficiency and achieved a continuous-wave output power of +6.5 dBm. We demonstrated a full C-band 10-Gb/s optical duobinary transmission with a constant modulation voltage of 2.4 Vpp. And we achieved a 200-km single-mode-fiber transmission with a power penalty of less than 1.0 dB over the entire C-band range.

Monolithically integrated parallel-amplifier structure for filter-free wavelength conversion

A parallel-amplifier structure (PAS) is proposed for filter-free wavelength conversion based on the cross-gain-modulation of a semiconductor optical amplifier. The PAS is a symmetric Mach-Zehnder interferometer having a polarization insensitive semiconductor optical amplifier in each arm, and was fabricated monolithically by butt-coupling of high-mesa and buried waveguides. Filter-free wavelength conversion in the co-propagative mode is demonstrated at a bit rate of 10 Gbit/s using the fabricated PAS. Clear eye opening and a power penalty as low as 0.9 dB were achieved.

Compact Wavelength Tunable Laser Module Integrated with n-i-n Structure Mach-Zehnder Modulator

A compact wavelength tunable laser module is fabricated by integrating a wavelength tunable laser array and an n-i-n structure Mach-Zehnder modulator. Without the need to change the driving condition of the Mach-Zehnder modulator, the module can operate at 10 Gb/s in the 32 nm C-band range.

Lossless 10-Gbit/s InP n-p-i-n Mach-Zehnder Modulator Monolithically Integrated with Semiconductor Optical Amplifier

Full C-band 10-Gbit/s 100-km SMF transmission of NRZ signals is demonstrated using a lossless InP n-p-i-n Mach-Zehnder modulator monolithically integrated with a semiconductor optical amplifier. A power penalty of less than 1.5 dB is confirmed.

Monolithically integrated 64-channel WDM channel selector on InP substrate

A monolithically integrated 64-channel selector on InP substrate is demonstrated using a novel configuration that allows it to handle a large number of WDM channels. Based on this configuration, the 64-channel WDM channel selector is realized with only 16 optical gates. Zero insertion loss was achieved for almost all channels in the fabricated device.

Surface Mountable 10-Gb/s InP Mach–Zehnder Modulator Module for SFF Transponder

We have developed a small, surface mountable InP-based Mach-Zehnder modulator module. New designs for the electrical ports enable the modulator to be directly mounted on a printed circuit board. We demonstrated a 100-km transmission through single-mode fiber with a 10-Gb/s nonreturn-to-zero signal and a 220-km transmission with a 10-Gb/s optical duobinary signal to confirm the applicability of this device as an ultralong-haul small form factor transponder.

10-Gb/s 100-km SMF Transmission Using InP Mach–Zehnder Modulator Monolithically Integrated With Semiconductor Optical Amplifier

An InP n-p-i-n Mach-Zehnder modulator and a semiconductor optical amplifier were monolithically integrated to compensate for the modulators insertion loss. The device gain exceeded 10 dB, and fiber-to-fiber lossless operation was demonstrated for the full C-band region. The error-free transmission of a 10-Gb/s nonreturn-to-zero signal over a 100-km single-mode fiber was also demonstrated across the full C-band region. A power penalty of less than 1.5 dB was confirmed.