Kiyoto Takahata

Bio: Kiyoto Takahata is an academic researcher from Nippon Telegraph and Telephone. The author has contributed to research in topics: Distributed feedback laser & Optical modulation amplitude. The author has an hindex of 16, co-authored 66 publications receiving 843 citations.

Transmission of 214-Gbit/s 4-PAM signal using an ultra-broadband lumped-electrode EADFB laser module

Abstract: Using a lumped-electrode EADFB laser with a modulation bandwidth of ∼59 GHz, we demonstrated single-wavelength single-polarization direct-detection 4-PAM transmission with the record net data rate of 200 Gbit/s.

Ultrafast optoelectronic packet processing for asynchronous, optical-packet-switched networks [Invited]

Abstract: Feature Issue on Optical Interconnection Networks (OIN). We describe hybrid optical-electrical systems that perform header processing and buffering of ultrafast, asynchronous optical packets. Our systems are enabled by three key, novel devices: an all-optical serial-to-parallel converter, an optical clock-pulse generator, and a photonic parallel-to-serial-converter. These devices allow utilization of complementary metal-oxide semiconductor technology for compact, highly functional optical packet processing. A simplified node architecture for asynchronous, optical- packet-switched networks is made possible by these systems with all the necessary node functions integrated compactly. We also demonstrate an optical label swapper and a photonic random access memory for 40-Gbit/s, 16-bit, asynchronous optical packets.

1.3-μm, 4 × 25-Gbit/s, EADFB laser array module with large-output-power and low-driving-voltage for energy-efficient 100GbE transmitter

Abstract: A 1.3-μm, 4 × 25-Gbit/s, EADFB laser array module with large output power and low driving voltage is developed for 100GbE. A novel rear grating DFB laser is introduced to increase the output power of the laser while keeping the single mode lasing, which is desirable for a monolithic integration. Also, InGaAlAs-based electroabsorption modulators make very-low-driving-voltage operation possible due to their steep extinction curves. With the module, very clear 25-Gbit/s eye openings are obtained for four wavelengths with the driving voltage of only 0.5 V while securing the dynamic extinction ratio required by the system. These results indicate that the presented module is a promising candidate for energy-efficient future 100GbE transmitter.

1.3 μm, 50 Gbit/s electroabsorption modulators integrated with DFB laser for beyond 100G parallel LAN applications

Abstract: A 1.3 µm, 50 Gbit/s electroabsorption modulator integrated with a DFB laser for future parallel LAN, the total data rate of which is over 100 Gbit/s, is developed. Very clear eye openings after 40 km transmission under 50 Gbit/s operation on singlemode fibre are demonstrated for eight wavelengths with discrete packages for the first time.

A Compact EADFB Laser Array Module for a Future 100-Gb/s Ethernet Transceiver

Abstract: A compact electroabsorption modulators integrated distributed feedback (EADFB) laser array module has been developed for 100-Gb/s Ethernet. Four 25-Gb/s EADFB lasers and an optical multiplexer are monolithically integrated on one chip in an area of only 2 mm × 2.6 mm. As a result, a compact 12 mm × 20 mm EADFB laser array module is achieved. A bridge-type RF circuit board is employed to transmit high-frequency, 4 × 25-Gb/s, electrical signals effectively in a narrow package and improve the electrical/optical response of the module. The module has a 3-dB frequency bandwidth of 20 GHz for the four lanes assigned in 100-Gb/s Ethernet. Furthermore, the possibility of realizing low-driving voltage operation is investigated to reduce the power consumption of the module. An error-free transmission through 10 km of single-mode fiber at 100 Gb/s with a modulation voltage of only 1 V is demonstrated.

Microwave photonics

Abstract: An overview of analog microwave photonics will be presented. The performance requirements for externally-modulated analog microwave photonic links will be reviewed with specific emphasis placed on modulator efficiency, laser noise, detected photocurrent, and link linearity.

Optical Packet and Burst Switching Technologies for the Future Photonic Internet

Abstract: This paper reviews advanced optical burst switching (OBS) and optical packet switching (OPS) technologies and discusses their roles in the future photonic Internet. Discussions include optoelectronic and optical systems technologies as well as systems integration into viable network elements (OBS and OPS routers). Optical label switching (OLS) offers a unified multiple-service platform with effective and agile utilization of the available optical bandwidth in support of voice, data, and multimedia services on the Internet Protocol. In particular, OLS routers with wavelength routing switching fabrics and parallel optical labeling allow forwarding of asynchronously arriving variable-length packets, bursts, and circuits. By exploiting contention resolution in wavelength, time, and space domains, the OLS routers can achieve high throughput without resorting to a store-and-forward method associated with large buffer requirements. Testbed demonstrations employing OLS edge routers show high-performance networking in support of multimedia and data communications applications over the photonic Internet with optical packets and bursts switched directly at the optical layer

High-speed and high-output InP-InGaAs unitraveling-carrier photodiodes

Abstract: The unitraveling-carrier photodiode (UTC-PD) is a novel photodiode that utilizes only electrons as the active carriers. This unique feature is the key for its ability to achieve excellent high-speed and high-output characteristics simultaneously. To date, a record 3-dB bandwidth of 310 GHz and a millimeter-wave output power of over 20 mW at 100 GHz have been achieved. The superior capability of the UTC-PD for generating very large high-bit-rate electrical signals as well as a very high RF output power in millimeter/submillimeter ranges can lead to innovations in various systems, such as broadband optical communications systems, wireless communications systems, and high-frequency measurement systems. Accomplishments include photoreceivers of up to 160 Gb/s, error-free DEMUX operations using an integrated UTC-PD driven optical gate of up to 320 Gb/s, a 10-Gb/s millimeter-wave wireless link at 120 GHz, submillimeter-wave generation at frequencies of up to 1.5 THz, and photonic frequency conversion with an efficiency of -8 dB at 60 GHz. For the practical use, various types of modules, such as a 1-mm coaxial connector module, a rectangular-waveguide output module, and a quasi-optic module, have been developed. The superior reliability and stability are also confirmed demonstrating usefulness of the UTC-PD for the system applications.

Recent advances in optical technologies for data centers: a review

Abstract: Modern data centers increasingly rely on interconnects for delivering critical communications connectivity among numerous servers, memory, and computation resources. Data center interconnects turned to optical communications almost a decade ago, and the recent acceleration in data center requirements is expected to further drive photonic interconnect technologies deeper into the systems architecture. This review paper analyzes optical technologies that will enable next-generation data center optical interconnects. Recent progress addressing the challenges of terabit/s links and networks at the laser, modulator, photodiode, and switch levels is reported and summarized.

Ultrawide-band/high-frequency photodetectors

Abstract: The two main trends in the progress of ultrawide-band/high-frequency photodetectors (PD's), improving the bandwidth-efficiency product and obtaining a high saturation current, are reviewed. With respect to achieving large bandwidth-efficiency, the limiting factors and potentials of edge-coupled (waveguide, waveguide-fed, traveling-wave, periodic-traveling-wave), resonant-cavity, and refracting-facet photodiodes, as well as the avalanche photodiode are discussed. Regarding high-saturation current, the author estimated how much the space-charge effect limits the saturation current and two ways to reduce the space-charge effect are outlined. One way is to distribute the photocarriers along the edge-coupled PD's and the other is to increase the carrier velocity using a uni-traveling carrier structure. The waveguide-photodiode-based technologies that we have developed are also presented; namely the design and fabrication of a 100-GHz waveguide photodiode (WGPD), uni-traveling carrier WGPD, 60-GHz packaging, and a 20-GHz large-core WGPD for planar lightwave circuit integration. A 50-Gb/s receiver opto-electronic integrated circuit technology based on the WGPD is also presented.