Kazuhiro Noguchi

Three-dimensional board-to-board free-space optical interconnects and their application to the prototype multiprocessor system: COSINE-III

A prototype multiprocessor system using three-dimensional board-to-board free-space optical interconnects is constructed for the first time to our knowledge. In the system, 64 processing units form a three-dimensional mesh processor network with the help of bidirectional board-to-board free-space optical interconnects. A theoretical analysis shows that the three-dimensional board-to-board freespace optical interconnects effectively solve common interconnection problems such as wiring congestion, signal delay, and clock skew. The prototype system, COSINE-III, is confirmed to work well as a multiprocessor system. The system is also shown to be easy to extend to a larger and more flexible system.

A rearrangeable multichannel free-space optical switch based on multistage network configuration

A rearrangeable 128*128-channel optical switch based on a multistage network configuration is demonstrated. The properties of optical components required for achieving up to 1000*1000-channel switches are discussed, taking into account the diffraction limit and liquid crystal light modulator (LCLM) crosstalk. An examination of the insertion loss and crosstalk properties of the switch reveals an average loss and crosstalk of 7.9 and -21.2 dB, respectively, and worst-case loss and crosstalk of 11.0 and -12.8 dB, respectively. Such low-loss and low-crosstalk properties indicate that the proposed switch structure is suitable for a large-scale rearrangeable switch. >

Loss increase for optical fibers exposed to hydrogen atmosphere

Loss spectrum changes for optical fibers exposed to a hydrogen atmosphere in the 15-200\deg C temperature range are measured. Loss increase due to molecular hydrogen dissolved into fibers is investigated from the loss peak at 1.24 μm, and that due to hydroxyl group formation from the loss peak at 1.41 μm. The loss increase due to molecular hydrogen is fully explained by physical solubility theory and diffusion equation. The empirical formula for time, temperature, and hydrogen-pressure dependences of the loss increase due to hydroxyl group formation is evaluated from the experimental results. The loss increase at 1.3- and 1.5-μm wavelength band at room temperature are estimated.

A three-dimensional mesh multiprocessor system using board-to-board free-space optical interconnects: COSINE-III

A prototype multiprocessor system using board-to-board free-space optical interconnects distributed over the processor boards is constructed for the first time. The system consists of 64 processing units interconnected in a three-dimensional (3D) mesh network with the help of bi-directional free-space optical interconnects. Theoretical analysis of signal delay and wiring congestion characteristics in the 3-D mesh network using free-space optical interconnects concludes that the network is superior to that using a conventional backplane interconnects. In the prototype system, signal transmission of all 96 free-space optical interconnects is stable even after repeated extraction and insertion of the processor boards, and system operation without error for 100 h is performed. The system is also shown to be easy to extend to a larger and more flexible system.<<ETX>>

Optical free-space multichannel switches composed of liquid-crystal light-modulator arrays and birefringent crystals

Transparent optical multichannel switches composed of liquid-crystal light modulator arrays and polarization beam routers composed of birefringent crystals are reported. For suppressing diffraction loss and stabilizing loss property, lens waveguide arrays are established in the switch body by inserting Fresnel lenslet arrays. The highly improved loss and crosstalk properties of the switch are confirmed.

Design and performance of a multiprocessor system employing board-to-board free-space optical interconnections: COSINE-1.

A practical thirty-six processor computer system employing manually reconfigurable board-to-board free-space optical interconnections has been built. The free-space optical interconnection section employs collimated beams that have 90 cm of transmission length at the maximum. It acts as a reconfigurable optical backplane that accommodates 144 input/output ports. The processors applied to the system are Transputers, each of which has four bidirectional links to communicate with other Transputers. This paper describes the design concept and the optical interconnection performances of the optical interconnection section employed in the constructed system.

Raman scattering spectrum analyses for fluorine‐doped silica optical fibers

Raman scattering spectra for fluorine‐doped silica fibers are measured. A Raman scattering peak, assigned to be the Si–F bond in the fibers, is observed at a wave number of 930 cm−1. Heat tests in a hydrogen gas atmosphere are carried out. The result shows that the fiber loss due to the hydroxyl group, which is produced by the heat test, decreases by fluorine doping. These phenomena show that the Si–O–Si bond defects are filled with doped fluorine atoms, and oxygen atoms positioned at the defects are exchanged by the fluorine atoms.

Selective stimulated Raman scattering in highly P 2 O 5 -doped silica single-mode fibers

Selective generation of the stimulated Raman Stokes wave in highly P(2)O(5)-doped silica single-miode fibers has been experimentally observed for the first time to our knowledge. It is assumed from the experimental results that the Stokes wave from P = O vibration interacts with the third Stokes wave from Si-O-Si vibration and is selectively amplified by Raman gain from the Si-O-Si vibration.

Optical limits for spatial interconnection networks using 2-D optical array devices.

An optical spatial interconnection network consisting of a 2-D source array, a lens array, and a detector array is suitable for use as the interconnection device in multiprocessor systems and neural networks. This paper describes the theoretical limits on the maximum channel numbers of these networks derived from optical restrictions. These results yield optimum design parameters for an interconnection network.

Demonstration of optical burst data switching using photonic MPLS routers operated by GMPLS signaling

We demonstrate, for the first time, optical burst data switching using photonic MPLS routers controlled by GMPLS. Optical burst data can be transmitted at a bit rate of 10 Gb/s without burst data loss, and high network throughput is achieved.