Masato Tsukada

Ultrafast photonic ATM switch with optical output buffers

An ultrafast photonic asynchronous transfer mode (ATM) (ULPHA) switch based on a time-division broadcast-and-select network with optical output buffers is presented. The ULPHA switch has an ultra-high throughput and excellent traffic characteristics, since it utilizes ultrashort optical pulses for cell signals and avoids cell contentions by novel optical output buffers. Feasibility studies show that an 80*80 ULPHA switch with 1-Gb/s input/output is possible by applying the present technology, and that more than 1 Tb/s is possible by making a three-stage network using such switches. As an experimental demonstration, 4-bit 40-Gb/s optical cells were generated and certain cells were selected at an output on a self-routing basis. With its high throughput and excellent traffic considerations, the ULPHA switch is a strong candidate for a future large-capacity optical switching node. >

An ultrafast photonic ATM switch based on bit-interleave multiplexing

An optical ATM switch is proposed in which cells from individual input channels are time-division multiplexed in a bit-interleave manner. This switch can easily handle multicast switching because it is based on a broadcast-and-select network. Compared to an alternative switch that uses a cell-interleave time-division multiplexing scheme, the proposed optical switch has a much simpler structure. It does not need a cell compressor at each input and a cell expander at each output, which greatly reduces hardware complexity. Feasibility analyzes showed that a 64/spl times/64 photonic ATM switch with 2.5 Gb/s input/output is possible using the proposed technology. In an experimental demonstration, 4 b cells were selected from a 55 Gb/s bit-interleave multiplexed cell stream by using a new nonlinear optical fiber switch. With its high switch throughput, our switch is a strong candidate for future large-capacity optical switching nodes.

A prototype broadcast-and-select photonic ATM switch with a WDM output buffer

A rack-mounted prototype of a broadcast-and-select (B and S) photonic ATM switch is fabricated. This switch has an optical output buffer utilizing wavelength division multiplexed (WDM) signals. The WDM technology solves. The cell-collision problem in a broadcast-and-select network and leads to a simple network architecture and the broadcast/multicast function. The prototype can handle 10-Gb/s nonreturn-to-zero (NRZ) coded cells and 5-Gb/s Manchester-coded cells and has a switch size of four. In this prototype, the level and timing design are key issues. Cell-by-cell level fluctuation is overcome by minimizing the loss difference between the optical paths and adopting a differential receiver capable of auto-thresholding. The temperature control of delay lines was successful in maintaining the phase synchronization. Using these techniques, we are able to provide a WDM highway with a bit error rate of less than 10/sup -12/. Fundamental photonic ATM switching functions, such as optical buffering and fast wavelength-channel selection, are achieved. We show our experimental results and demonstrate the high performance and stable operation of a photonic ATM switch for use in high-speed optical switching systems as an interconnect switch for a modular ATM switch and an ATM cross-connect switch.

Broadcast-and-select photonic ATM switch with frequency division multiplexed output buffers

A photonic ATM switch has been developed with frequency division multiplexed (FDM) output buffers. The switch has a broadcast-and-select network architecture using fixed-frequency-channel transmitters and a passive star configuration. Although it has a simple structure, it can provide either broadcast or multicast switching. The output buffers, which resolve cell contentions, are comprised of fiber delay lines that can easily handle signal speed of over 10 Gb/s. Experimental switching of two-multiplexed 10 Gb/s cells with a 2.8-dB power penalty demonstrated high-speed switching.

Optical output buffered ATM switch prototype based on FRONTIERNET architecture

We constructed a rack-mounted prototype photonic ATM switch based on the FRONTIERNET architecture. The advantages of the architecture are that its output-buffering scheme overcomes the bottlenecks that can occur when receiving and storing concurrent high-speed cells, and that there is no need to deal with contention resolution between input highways. The prototype has 16 input/output ports and 2.5 Gb/s transmission speed. Actually, six input ports and one output port are mounted in two racks. We demonstrated successful cell routing and buffering, and its stable operation, with 24-h bit-error-free switching operation. We also discussed problems to be solved in increasing the throughput of FRONTIERNET.

Ultrafast photonic ATM (ULPHA) switch and a video distribution experiment

We describe the hardware implementation and experimental results for each function of our ultrafast photonic ATM (ULPHA) switch, which is an output buffer type ATM switch based on a time-division broadcast-and-select network. The hardware description focuses on the cell coder for generating ultrafast optical cells, the cell buffer with cell selection function, and the cell decoder for detecting ultrafast optical cells. Experiments demonstrate the generation and detection of 23 Gb/s, 4 b optical cells, including bit-error-rate measurements, and the operation of the cell buffer with the cell selector function. In a video distribution switching experiment, the switching of two time-division-multiplexed channels (25 Gb/s, 4 b optical cells) was achieved.

Terahipas: a modular and expandable terabit/second hierarchically multiplexing photonic ATM switch architecture

A terabit/second hierarchically multiplexing photonic asynchronous transfer mode (ATM) switch network architecture, called Terahipas, is proposed. It combines the advantages of photonics (a large bandwidth for transport of cells) and electronics (advanced logical functions for controlling, processing, and routing). It uses a hierarchical photonic multiplexing structure in which several tens of channels with a relatively low bit rate, say 2.4 Gb/s, are first time-multiplexed on an optical highway by shrinking the interval between optical pulses, then a number of optical highways are wavelength-multiplexed (or space-division multiplexed). As a result, the switch capacity can be expanded from the order of 100 Gb/s to the order of 10 Tb/s in a modular fashion. A new implementation scheme for cell buffering is used for eliminating the bottleneck when receiving and storing concurrent optical cells at bit rates as high as 100 Gb/s. This new architecture can serve as the basis of a modular, expandable, high-performance ATM switching system for future broad band integrated service digital networks (B-ISDNs). >

Real-time phase demodulator for optical heterodyne detection processes

A real-time, wideband phase demodulator from which phase fluctuations extending over 2 pi radians can be taken out is designed for use in optical heterodyne detection processes. A phase-locked-loop (PLL) frequency multiplier, aided by compensation circuits to produce an unwrapped phase output, plays a major role in demodulating, in real time, the rapidly fluctuating phase from a generated beat photocurrent. The fabricated demodulator operates in the range 0 to 32 pi radians, with a minimum detectable phase (MDP) of 2 pi /128.

Correlation processing of fluctuating optical waves guided in an externally perturbed birefringent single-mode fiber by optical heterodyne interferometry

A description is given of experimental studies on the correlation processes for the optical waves guided in a birefringent single-mode fiber exposed to random vibrations. A laser beam with orthogonally polarized two-frequency components is launched into the fiber in such a way that the polarization directions of the two-frequency components coincide with the birefringent axes of the fiber. On leaving the fiber, its orthogonal components, modulated at random in phase and amplitude, are superimposed with a reference laser beam with two-frequency components; two beat photocurrents are produced from the combination of different frequency components of the signal and reference laser beams. The beat photocurrents can yield the fluctuating phase and amplitude components of the guided optical waves, which are statistically processed by use of a signal analyzer. Autocorrelation and cross-correlation functions for the fluctuation components are given together with their corresponding power spectra. Characteristic features extracted from the measured results are explained. >

Design of photonic ATM switch and a rack-mounted prototype

This paper describes large-capacity photonic ATM switching systems being developed that use FDM (or WDM) techniques. Our system is based on a simple star architecture with a modular structure. We show that it is possible to obtain a 320-Gb/s system that has enough S/N margin and can tolerate the polarization and frequency dependencies of optical devices. Our experiments using rack-mounted prototype modules to demonstrate the feasibility of our system, as well as successful 10-Gb/s 4/spl times/4 broadcast-and-select and 2.5-Gb/s 16/spl times/16 frequency-routing switch operations.