Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1998-11-05
2002-04-02
Pascal, Leslie (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200
Reexamination Certificate
active
06366375
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an optical-signal transmission apparatus and a method for optical signal transmission, and a signal processing apparatus for signal processing including optical signal transmission.
The function of a circuit board used in a data processing system (daughter board) is increasing by virtue of development of very large-scale integrated circuit (VLSI). With the increase in circuit function, the number of signals connected to respective circuit boards increases, and therefore, a parallel architecture requiring a number of connectors and connection lines is adopted as a data bus board (mother board) connecting the respective circuit boards (daughter boards) with a bus structure. The parallel architecture is developed by multilayered and miniaturized connection lines so as to improve the bus operation speed. However, signal delay due to capacity between connection wires and resistance of the connection wire lowers bus operation speed, and the system processing speed is restricted by the bus operation speed. Further, a problem occurs when the apparatus heats with increase in electric consumption. Further, as transmission-waiting time due to bus occupation influences the system processing speed, there is a need for simultaneous transmission among a plurality of circuit boards. Furthermore, the problems of EMI (Electromagnetic Interference) noise due to high-density bus-connection wiring seriously disturb improvement in the system processing speed.
That is, as the bus operation speed is limited, the number of the bus wires is increased in correspondence with increase in data transmission amount. However, as the number of wires increases, the electric consumption increases, further, transmission speed reduces due to skew between wires and further, there is a problem in wiring space. Japanese Published Unexamined Patent Application No. Sho 64-14631 and Hei 8-328707 disclose analog bus connection to reduce the number of wires among devices and facilitate wiring.
FIG. 13
shows an example of the analog bus connection disclosed in Japanese Published Unexamined Patent Application No. Hei 8-328707.
Apparatuses
401
and
411
are interconnected by an analog bus
406
via two A/D converters
404
and
407
and two D/A converters
405
and
408
.
An n-bit signal generated from the apparatus
401
is introduced via a transmission path
403
into the D/A converter
405
, converted into analog data, and transmitted onto the analog bus
406
. The data passed through the analog bus
406
is converted into an n-bit digital signal by the A/D converter
407
, and transmitted via a transmission path
409
into the apparatus
411
. On the other hand, a signal transmitted from the apparatus
411
is transmitted via a transmission path
410
into the D/A converter
408
, converted into analog data, and transmitted onto the analog bus
406
. The data passed through the analog bus
406
is converted into a digital signal by the A/D converter
404
, and transmitted via a transmission path
402
into the apparatus
401
.
As described above, the analog bus
406
operates with a multilevel analog signal, and the apparatuses
401
and
411
operate with a digital signal.
In the analog bus connection as described above, as the signal that passes through the analog bus
406
is a multilevel analog signal, level change occurs due to a bus-line resistive component, a leak current and the like. If the analog bus line is prolonged or a number of apparatuses are connected to the analog bus, data transmission cannot be accurately performed without difficulty.
Further, microcomputers and the like often use a plurality of buses in addition to connection with a number of functional blocks. In such case, as communication cannot be made among the plurality of buses, the above-described analog bus connection cannot be realized without difficulty. To solve this problem, Japanese Published Unexamined Patent Application No. Hei 8-328707 proposes a circuit to compensate the level change of analog bus. However, since an electric wire is used as the bus line, this is not a substantial solution of the problem to prevent the level change due to wiring resistance. Further, the problems of increase in electric consumption in case of high-speed bus drive and the skew of parallel wiring for large-capacity transmission cannot be solved. Further, in the case where the electric wire is used as the bus line, even if a multilevel-logic analog bus is employed, although simultaneous multiplex transmission can be performed in the same direction, bidirectional simultaneous multiplex transmission cannot be performed.
To realize high-speed transmission, utilization of an intra-system optical connection technique, i.e., so-called optical interconnection, instead of electric transmission technique is studied. The optical interconnection technique has been proposed by Teiji Uchidata (in The 9th Circuit Packaging Scientific Lecture Meeting), H. Tomimuro, et al., (“Packaging Technology for Optical Interconnects”, IEEE Tokyo, No. 3, pp. 81-86, 1994), and Osamu Wada (Electronics 1993 April., pp. 52-55), as various applications in accordance with the content of system construction.
As one of the proposed various optical interconnection techniques, Japanese Published Unexamined Patent Application No. Hei 2-41042 discloses a data bus employing an optical data transmission method using high-speed and high-sensitivity light-emission/photoreception devices. In this example, a serial optical data bus for loop transmission between respective circuit boards is proposed. The circuit boards respectively have a light-emission/photoreception device on both front and rear surfaces, such that the light-emission/photoreception devices on adjacent circuit boards installed in a system frame are optically connected. In this method, signal light sent from one circuit board is photoelectric-converted by an adjacent circuit board, and the signal light is further electrolight-converted by the circuit board, and sent to the next adjacent circuit board. In this manner, the respective circuit boards, sequentially and serially arranged, transmit signal light through all the circuit boards by repeating photoelectric conversion and electrolight conversion. By this arrangement, the signal transmission speed depends on the conversion speed of the photoelectric conversion and electrolight conversion by the light-emission/photoreception devices on the circuit boards, and at the same time, is limited by the conversion speed. Further, as data transmission among the circuit boards is made by using optical connection via free space by the light-emission/photoreception devices on the respective circuit boards, all the circuit boards must be optically positioned with the light-emission/photoreception devices on both front and rear surfaces of the circuit boards and the circuit boards must be optically connected. Further, as the optical connection is made via the free space, interference (cross talk) occurs between adjacent optical transmission paths, which may disturb data transmission. Further, data transmission failure might occur by scattering of signal light due to conditions within the system such as dust. Further, as the respective circuit boards are serially arranged, the connection is released if any of the boards is removed, and a spare circuit board to compensate for the lack of removed is required. That is, the circuit boards cannot be freely added or removed, and the number of circuit boards is fixed.
Japanese Published Unexamined Patent Application No. Sho 61-196210 discloses a data transmission technique among circuit boards utilizing a two-dimensional array device. According to this technique, a plate is provided opposing to a light source having two parallel surfaces, and circuit boards are optically connected via a light path formed by a diffraction grating and a reflection device provided on the plate. However, this method merely connects light emitted from one point to one fixed point, and cannot connect all the circ
Fujimagari Hiroshi
Funada Masao
Hamada Tsutomu
Hirota Masaki
Ishida Hiroki
Fuji 'Xerox Co., Ltd.
Oliff & Berridg,e PLC
Pascal Leslie
Phan Hanh
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