Nobuhiro Fujimoto

Skew-free parallel optical transmission systems

This paper proposes two kinds of parallel line codes based on multiplexing and nonmultiplexing, and a method of automatic skew suppression based on bit synchronization and frame synchronization. This achieves parallel high-speed optical transmission to overcome bottlenecks in parallel electronic transmission and to increase the distance of high-throughput interconnections. We have developed GaAs coder/decoder large-scale integrations (LSIs) for the coding algorithm and skew suppression, and analog LSIs for compact, low-power, highspeed parallel optical links. Experimental results show that our proposed parallel transmission methods and fabricated LSIs can play a key role in realizing high-speed, long-distance parallel transmission and in reducing the size and power consumption of high-throughput parallel optical links.

Flexible synchronous broad-band subscriber loop system: optical shuttle bus

A flexible, synchronous, broadband subscriber loop system called the optical shuttle bus is discussed. The emphasis is on the proposed design architecture and performance of a 1.8-Gb/s prototype system. The optical shuttle bus is constructed of multigigabit/second intelligent optical shuttle nodes (OSNs). The software-defined OSNs allow the bus to be configured as a synchronous transmission network with any topology and provides flexible channel allocation by means of a drop/insert/cross-connect function. The OSN can be configured as a highly reliable network by virtue of its self-healing functions such as line switch, bypass, and loop back. The proposed bus architecture has been successfully applied in a 1.8-Gb/s prototype in which three OSNs are connected by one 10-km and two 5-dm single-mode fibers in a ring configuration. Very compact and inexpensive equipment is realized by using high-speed ICs. Experimental results show the proposed architecture to be a powerful one for the realization of synchronous broadband subscriber loop systems. >

Gigabit single-mode fiber transmission using 1.3-µm edge-emitting LEDs for broad-band subscriber loops

This paper describes gigabit single-mode fiber transmission using 1.3-μm edge-emitting LEDs for broad-band subscriber loops, focusing on a method of calculation for maximum transmission distance and 1.2-Gbit/s and 600-Mbit/s transmission experiments. Gigabit single-mode fiber transmission is necessary for subscriber loops, especially in broad-band ISDN and optical CATV systems. Edgeemitting LEDs are excellent light sources because of their high power launched into the fiber compared with surface-emitting LEDs, and currently lower cost and higher reliability than laser diodes. The maximum transmission distance is carefully estimated by taking into account the wavelength dependence for both chromatic dispersion and loss of the single-mode fiber, and the possibility of gigabit transmission near the dispersion free wavelength 1.3 μm, is confirmed. Encouraged by the above results, we demonstrate 1.2-Gbi,t/s 10-km and 600-Mbit/s 20-km transmission experiments using a newly developed 1.3-μm edge-emitting LED and a new driver circuit with a simple response compensation circuit. These results show the proposed calculation method and the LED response compensation circuit to be powerful tools for the realization of low-cost gigabit single-mode fiber transmission using edge-emitting LEDs.

Photonic highway: broad-band ring subscriber loops using optical signal processing

The introduction of optical signal processing technology into transmission systems and basic experiments with optical drop/insert using bistable laser diodes are discussed. With broadband integrated services digital network (B-ISDN) architecture and technology now under study, optical signal processing (OSP) is being considered to increase network capacity and flexibility. B-ISDN will require over 40 Gb/s in the feeder loop that connects the central office and remote terminals having drop/insert function. Remote terminals will process large amounts of high-speed data. An OSP-based broadband subscriber loop photonic highway that uses a ring architecture linking photonic access nodes (PANs) that directly process optical signals is proposed. Each PAN has an optical drop/insert function and can synchronize optical frame signals using a proposed optical sampling memory. Optical drop/insert experiments confirmed the feasibility of the proposed method. >

Experimental broadband drop/insert/cross-connect system: 1.8 Gbit/s optical shuttle bus

An optical shuttle bus architecture to realize a flexible synchronous interoffice and subscriber-loop network is proposed. An experimental broadband drop/insert/crossconnect system with SONET interfaces, called the 1.8-Gb/s optical shuttle bus, is then described. The bus is constructed of multigigabit intelligent optical shuttle nodes (OSNs). The software-defined OSN can be configured as any synchronous transmission network topology and provides flexible channel allocation by means of the drop/insert/crossconnect function. The OSN can also be configured as a highly reliable network by using self-healing functions, such as line switch, bypass, and loop back. Laboratory testing of an experimental system, consisting of three OSNs with one 10-km and two 5-km single-mode fibers in a ring configuration, has confirmed the practicality of the proposed architecture.<<ETX>>

Gb/s array LSIs for parallel optical links

The authors develop four-channel GaAs transmitter and receiver LSI chips for parallel optical links. The transmitter and receiver LSI chips have uniform characteristics across the four channels. A transmission experiment using this chip set, and LD array, and a PD array confirmed that the parallel optical link provides simultaneous four-channel operation exceeding 1.2 Gb/s/ch.<<ETX>>

All-optical data-latch experiments for photonic access nodes in the photonic highway

Abstract A novel approach to direct access at the optical level is proposed. We conducted experiments on all-optical data-latch functions using bistable laser diodes (LDs) for all-optical droplinsert operation in a 50-Mbitls data highway.

Low-voltage gigabit optical transmitter using a direct logic gate modulation of a tandem-electrode laser

We propose a new direct-modulation scheme for use in a high-speed optical transmitter with a direct logic gate connection to a laser diode. We have confirmed gigabit-per-second operation with voltage modulation onto a tandem-electrode laser.

Consideration of Optical Channel Number and Data/Frame Phase Tolerance for the Photonic Ring Highway

This paper discusses the maximum channel number and allowable data/frame phase tolerance in a photonic ring highway and gives experimental results using a new high-speed bistable laser diode.