Kazuhisa Kaede

12-channel parallel optical-fiber transmission using a low-drive current 1.3- mu m LED array and a p-i-n PD array

Twelve-channel 14-Mb/s/channel 1-km parallel optical-fiber transmission using a 1*12 low-drive-current 1.3- mu m light-emitting diode (LED) linear array and an InGaAs p-i-n photodiode linear array, with the LED drive current as low as 12 mAp-p/channel, is discussed. No receiver sensitivity degradation has been observed under simultaneous 12-channel operation. The skew was less than 6 ns after transmission through a 1-km-long 12-channel optical-fiber cable, which was sufficiently small for 14-Mb/s parallel transmission. >

A coherent photonic wavelength-division switching system for broad-band networks

A coherent photonic wavelength-division (WD) switching system, utilizing a coherent wavelength switch ( lambda switch), is proposed. In the proposed coherent lambda switch, the tunable wavelength filter function is accomplished using coherent optical detection with a wavelength tunable local oscillator. The coherent photonic WD switching system has the following features; (1) low crosstalk switching for dense WDM signal, and (2) large line capacity capability. Design considerations show that 32 wavelength division channels can be available with a coherent lambda switch. It is also shown that a broadband metropolitan-area-network with over 1000 line capacity is possible, using a multistage connection in the coherent lambda switches. The switching function of the coherent lambda switch is demonstrated in a two-channel wavelength-synchronized switching experiment, using 8-GHz-spaced, 280-Mb/s optical FSK signals. >

Frequency separation locking and synchronization for FDM optical sources using widely frequency tunable laser diodes

A laser diode (LD) frequency separation locking method (called the reference pulse method) is proposed. This method has advantageous features for frequency division multiplexing (FDM) networks from the viewpoint of frequency separation stability with a strict frequency separation standard, modulation format independence, controllability over a large number of LDs, and frequency synchronization capability. Frequency locking experiments, using four and ten controlled LDs, confirmed that the control system using the method can stabilize frequency spacing for more than 100 LDs. The frequency fluctuation is suppressed to less than 10 MHz. Frequency synchronization, utilizing the reference pulse method, is proposed and demonstrated experimentally for two controlled LD groups, each consisting of three LDs. Frequency discrepancy between two LD groups was only 2.7% of the frequency separation. Required frequency-swept light power and controlled LD power at the detector input for frequency synchronization indicate that more than 50000 LD groups within a 10 km area, each having 100 LDs, can be synchronized simultaneously. >

A new architecture of photonic ATM switches

A photonic asynchronous transfer mode (ATM) switch architecture for ATM operation at throughputs greater than 1 Tbit/s is proposed. The switch uses vertical-to-surface transmission electrophotonic devices (VSTEPs) for the optical buffer memory, and an optical-header-driven self-routing circuit in contrast with conventional photonic ATM switches using electrically controlled optical matrix switches. The optical buffer memory using massively parallel optical interconnections is an effective solution to achieve ultra-high throughput in the buffer. In the optical-header-driven self-routing circuit, a time difference method for a priority control is proposed. For the optical buffer memory, the write and read operations to and from the VSTEP memory for 1.6 Gbit/s, 8-bit optical signal are confirmed. The optical self-routing operation and priority control operation by the time difference method in the 4*4 self-routing circuit were performed by 1.6-Gbit/s 256-bit data with a 10-ns optical header pulse.<<ETX>>

Optical Switching in Coherent Lightwave Systems

Broad-band networks providing various kinds of services, such as video and high — speed data communications, have received increasing attention in not only local-area networks(LANs) but also wide-area networks(WANs). The possible architecture of a global WAN is illustrated in fig.1. With such a network, broadband communication/distribution services may be offered all over the globe. Optical communications utilizing both inland and under-sea optical fiber transmissions, together with satellite communication, will play an important role in broad-band global WANs. Recent progress in optical fiber transmission has already made worldwide point-to-point transmission links possible. Coherent transmission technology would further enhance transmission length and information capacity. Optical switchihg would be a key technology for achieving all-optical broad-band WANs, where switching and routing functions,as well as transmission, will be accomplished in optical domain.

InGaAsP planar buried heterostructure laser diode for optical communications

Buried heterostructure-type lasers are particularly attractive as light sources for optical fiber communications because of their low threshold current and stable single-mode operation. Problems, however, still remain regarding the current confinement and the device production yield. We have realized a new planar buried heterostructure laser diode (PBH-LD), which is characterized by a unique current confining structure and a flat device surface, in addition to low threshold current and stable oscillation mode characteristics of BH-type lasers.1,2 In this paper, the fabrication and basic characteristics of InGaAsP PBH-LDs at 1.3 and 1.5 μm are described.

150-Mbit/s/ch 12-channel optical parallel transmission using an LED and PD array

High speed optical parallel transmissions are attractive for various computer interface and interconnections because of their advantages in transmission capacity, distance, and small cable size over electrical parallel transmission due to low skew and low signal loss in fibers. Moreover, they have advantages in electrical component cost and size over optical serial transmissions, when the bit rate per channel increases to over 100 Mbit/s, because they do not need faster driver/receiver and MUX/DEMUX circuits. Monolithically integrated linear arrays of low drive current, high speed light emitting diodes (LEDs) are particularly useful because of their potential for low temperature sensitivity, high reliability, and low component cost. However, the high speed linear LED arrays reported1,2 have been requiring large drive current of 100-150 mA/ch for sufficient fiber coupled power and speed. This paper reports a 12-channel 150-Mbit/s/ch 100-m optical parallel transmission, using a newly developed low drive current LED and PD array, with as low as 15-mA p-p/ch LED drive current. This high speed optical parallel transmission should meet the demand for upgrading the performance of high speed channels and interfaces for supercomputers and other systems.