Makoto Nishio

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>>

A photonic wavelength-division switching system using tunable laser diode filters

A photonic wavelength-division switching system using semiconductor tunable wavelength filters is proposed. Wavelength switches and multistage switching networks are used. The potential of 100 wavelength-division channel achievement in switching systems is estimated, based on InP optical integrated circuits. A wavelength network synchronization method is proposed, which will enable the network to utilize such a large number of wavelength-division channels without wavelength misalignment and drift. An eight-channel wavelength-division switching experiment, using phase-shift controlled distributed-feedback laser diodes as tunable wavelength filters, is reported.<<ETX>>

ATM flexible access node for subscriber feeder networks

In designing flexible access networks, we propose an ATM-based network node named ATM flexible access node. ATMFAN has capabilities of effective transport of user traffic in subscriber feeder networks based on the virtual path connections. The main goal of ATMFAN is to provide node and network level flexibilities with access feeder networks, such as flexible network topology configuration and flexible interface package accommodation. We also describe a prototyping model of ATMFAN and show its feasibility on the ring-shaped feeder network by connecting ATMFANs.

WD&MMT switching networks in combination with photonic and electronic switching technique

New photonic and electronic hybrid switching networks, wavelength division and memory matrix time (WD&MMT) switching networks, which are constructed from a combination of photonic wavelength-division switching and electronic memory matrix time switching techniques, are proposed. The WD&MMT switching networks can be used to construct large line-capacity switching networks with a small amount of hardware, because of their very large total multiplexity given by the product of wavelength-division, time-division, and space-division multiplexity. Growable WD&MMT switching network structures, which can increase the hardware in proportion to the required line-capacity, are also presented.<<ETX>>

Application of Optical FSK Signals to Wavelength-Division Switching Systems

A wavelength-division switching network, using optical FSK signals, has been proposed. It has low crosstalk characteristics and can achieve greater wavelength-division multiplexity than that using intensity-modulated signals.