Optical communications – Transmitter and receiver system – Including optical waveguide
Reexamination Certificate
2000-09-05
2004-09-14
Sedighian, M. R. (Department: 2633)
Optical communications
Transmitter and receiver system
Including optical waveguide
C398S139000, C398S141000, C398S164000, C385S015000, C385S031000, C385S146000
Reexamination Certificate
active
06792213
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical signal transmitting apparatus, an optical data bus system and a signal processing apparatus, and more particularly to an optical signal transmitting apparatus for emitting incident optical signals in a plurally branched state, an optical data bus system using the optical signal transmitting apparatus, and a signal processing apparatus using the optical data bus system.
2. Description of the Related Art
As a result of very large scale integrated (VLSI) circuits, the range of circuit functions of daughter boards for use in a data processing system has substantially expanded. As the number of signals connected to each daughter board increases along with the increase in circuit functions, a parallel architecture requiring many connectors and connecting lines is adopted for the data bus board (mother board) for connecting the daughter boards in a bus structure. While the operating speed of the parallel bus has been enhanced by the use of multiple layers of fine connection lines in the parallel architecture, the processing speed of the system is sometimes limited by the operating speed of the parallel bus as a consequence of signal delays due to inter-wiring capacitance and the resistance of connection wiring. Also the problem of electromagnetic interference (EMI) due to the increased density of parallel bus wiring also poses a severe constraint to the enhancement of system processing speed.
In order to solve these problems and enhance the operating speed of the parallel bus, possible use of an intra-system optical connection technique known as optical interconnection is being studied. Various forms of optical interconnection, as its outlines described by Uchida, the Scientific Lecture Convention on Circuit Packaging 15C01, pp. 201-202(in Japanese) and H. Tomimuro et al, IEEE Tokyo Section Denshi Tokyo No. 33, pp. 81-86 (1994) reveal, are proposed, differing with the configuration of the system.
Of the various forms of optical interconnection technique so far proposed, an optical data transmission formula using a light emitting/receiving device is disclosed in Japanese Published Unexamined Patent Application No. Hei 2-41042. This patent application proposes a serial data bus for loop transmission among daughter boards in which light emitting/receiving devices are disposed on the top and bottom sides of each daughter board, and the light emitting/receiving device on adjoining daughter boards incorporated into a system frame are spatially coupled by light. According to this formula, an optical signal sent from any one daughter board is opto-electrically converted in an adjoining daughter board, on which the signal is further electro-optically converted to send the resultant optical signal to the next adjoining daughter board, so that the daughter boards are successively arranged in series and the signal is transmitted to every daughter board built into the system frame while repeating opto-electric and electro-optical conversions. As a result, the speed of signal transmission both depends on and is limited by the speed of opto-electric or electro-optical conversion of the light receiving/emitting device arranged on each daughter board. Furthermore, since data transmission between daughter boards uses optical coupling, in which free space intervenes, by the light receiving/emitting devices arranged on the daughter boards, interference between adjoining optical data transmission paths (cross talk) is likely to arise and invite faulty transmission of data. Faulty transmission of data may also arise from some environmental factor in the system frame, for instance the scattering of optical signals by dust or the like.
Japanese Published Unexamined Patent Application No. Sho 61-196210 proposes a formula by which daughter boards are coupled via an optical path including diffraction gratings and reflective elements arranged over the surface of a plate. According to this formula, since light emitted from one point can be connected to only one fixed point, it is impossible to comprehensively connect all the daughter boards as an electric bus does.
Also, a number of patents have been applied for regarding data transmission between daughter boards using an optical connecting device equipped with a branching element.
Japanese Published Unexamined Patent Application No. Sho 58-42333 discloses an instance of data transmission between daughter boards using plural half mirrors. However, where plural half mirrors are used, the overall hardware size tends to become large, and each mirror should be coordinated in optical position relative to the pertinent light emitting/receiving device. Moreover, since transmitted light having passed a half mirror is approximately halved in optical intensity compared with the incident light, repetition of branching and transmission more than once substantially weakens the optical intensity with the consequence that the light receiving device can obtain no sufficient light intensity and signal transmission is thereby made impossible.
Japanese Published Unexamined Patent Application No. Hei 4-134415 reveals a formula by which an optical signal is brought to incidence on a side of lens array in which plural lenses are formed and each lens emits the signal. According to this formula, the closer a lens is to the incident position of light, the greater the luminous energy emitted from the lens, and this may result in intensity fluctuations of the emitted signal depending on the positional relationship between incidence and emission. Furthermore, the utilization efficiency of the incident luminous energy is low because a considerable proportion of the light coming incidence from one side escapes from the opposite side.
There is also an optical bus formula using an optical fiber, as disclosed in Japanese Published Unexamined Patent Application No. Sho 63-1223, by which substantially uniform optical signals can be transmitted by successively increasing the ratio of branching from the input end onward. A method for forming a coupler adaptable to such a formula is described in the IEEE Photonics Technology Letters, Vol. 8, No. 12, December (1996)p1650. The coupler forming method described therein achieves branching with a V groove formed in the optical fiber. Conceivably, by adjusting the size of the V groove, the output luminous energy may be adjusted, but it is extremely difficult to produce such an arrangement, and utilization of the incident luminous efficiency would be inadequate, too.
Further, a star coupler for uniformizing the intensities of branched optical signals is disclosed in the Japanese Published Unexamined Patent Application No. Hei 9-184941. This star coupler schematically has plural optical fibers of which the ends on one side are bundled and fixed, and an optical waveguide large enough to cover the plural optical fibers brought into contact with one end face of the bundle, of which the other end face is provided with an optical reflector.
Where such a coupler is used for data transmission between daughter boards, an increase in the number of boards would result in a corresponding increase in the number of the fibers to be connected to a light receiving/emitting element, inviting a greater complexity of configuration and a consequent larger size of hardware.
SUMMARY OF THE INVENTION
The present invention, attempted in view of the above-described circumstances, is intended to provide an optical signal transmitting apparatus permitting easy laying out of connecting boards, an optical data bus system using more than one such optical signal transmitting apparatus, and a signal processing apparatus using that optical data bus to carry out signal processing including transmission and reception of data.
To achieve this intention, according to the invention, there are provided a light transmitting medium having plural level gaps at one end of the light transmitting medium, in which the plural level gaps correspond to plural incidence/emission portion and an optical signal
Hamada Tsutomu
Kyozuka Shinya
Okada Junji
Yamada Hidenori
Fuji 'Xerox Co., Ltd.
Sedighian M. R.
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