JPS61134995A - Optical memory - Google Patents

Abstract

PURPOSE:To eliminate the necessity of electrical and magnetic shielding and reduce the weight and size of an optical memory, by constituting the optical memory with optical fibers and optical devices only. CONSTITUTION:An optical switch 1 of 2X2 matrix has input side terminals 2 and 3 and output side terminals 4 and 5. The optical switch 1 is of a waveguide type utilizing an electrooptic effect and, when a change-over switch 6 is turned on and a voltage V is applied across the electrodes between the waveguides, becomes a crossed state. When the switch 6 is turned off and the voltage V is not applied, the optical switch 1 is switched to a through state one. A bus cable 7 is connected with the input side terminal 2 (terminal for writing signal) of the optical switch 1 and, at the same time, another bus cable 8 is connected with the output side terminal 4 (terminal for reading out signal). Moreover, an input side terminal 9 for storing signal is connected between the input terminal 3 and output terminal 5 of the optical switch 1 in the form of a loop.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a novel dynamic memory type optical memory in which an optical signal is circulated around a loop-shaped optical fiber and stored therein.

[Prior Art] Conventional optical memory is a static memory that stores information in a fixed or semi-permanent manner in a storage medium such as an optical disk memory using light irradiation or a pulsed electric field. By shining light onto the medium, changes in its reflection, transmission, refraction, etc. are read out. Also,
The mainstream storage method for conventional optical memories, as well as semiconductor memories, is electromagnetic.

[Problems to be Solved by the Invention] However, the electromagnetic memory described above is easily affected by the electric vi1 induction, and a shield is required to prevent this, resulting in a large device. Furthermore, when data is transferred between computers or memories using optical fibers, electrical/optical exchange and optical/electrical conversion are always required.

[Object of the Invention] The present invention was devised to solve the above-mentioned problems of the prior art, and an object of the present invention is to make the memory device lightweight and compact without the need for electrical/magnetic shielding, and to make the memory device lightweight and compact. /An object of the present invention is to provide an optical memory that can easily transmit light without performing optical conversion or optical/electrical conversion.

[Summary of the Invention] To achieve the above object, the present invention provides n×n (n≧
2) One of the input side terminals of the optical switch in the matrix is used as a signal writing terminal, and one of the output side terminals of the optical switch is used as a signal output terminal, and the signal is circulated and stored. For this reason, the optical switch is equipped with a signal storage optical fiber that is connected in a loop between the other input and output terminals of the optical switch, so that signals can be put in and out of the signal storage optical fiber loop by switching the optical switch. It is composed of

U example Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

In FIG. 1, 1 is a 2×2 matrix optical switch, which has an input terminal 2.3 and an output terminal 4.5. This optical switch 1 is of a waveguide type that utilizes the electro-optic effect. When the changeover switch 6 is turned on and a voltage V is applied to the electrodes between the waveguides, the terminals 2 and 5 are connected, and the terminals 3 and 5 are connected. 4 are connected. That is, it becomes a cross state. On the other hand, when the changeover switch 6 is turned OFF and the voltage (2) is not applied, the terminals 2 and 4E are connected, and the terminal 3.5 is connected to the through state.

A bus cable 7 is connected to the input terminal 2 (signal writing terminal) of the optical switch 1, and a bus cable 8 is connected to the output terminal 4 (signal reading terminal). Also,
A signal storage optical fiber 9 is connected in a loop between the input terminal 3 and output terminal 5 of the optical switch 1.

Next, the operation of this embodiment will be described.

When the changeover switch 6 of the optical switch 1 is turned on when a signal is transmitted to the optical switch 1 through the bus cable 7, the waveguide of the optical switch 1 becomes a cross state, and this signal is transmitted to the input terminals 2. The signal is input to the signal storage optical fiber 9 via the output terminal 5.

The optical signal input to the signal storage optical fiber 9 passes through the optical fiber 9 to the input terminal 31111I of the optical switch 1.
transmitted to.

Assuming that the length of the optical fiber 9 is Jl and the group refractive index is n, the time required for an optical signal from the output terminal 5 to the input terminal 3 is n - J/Q (where C is the speed of light). Therefore, if the changeover switch 6 is turned OFF before the period n - J2/C2 has passed after the signal is input from the output side terminal 5 of the optical switch 1 to the optical fiber 9, and the waveguide of the optical switch 1 is put into the through state, An optical signal transmitted through the optical fiber 9 and arriving at the input terminal 3 of the optical switch 1 is returned to the optical fiber 9 via the terminal 3.5. That is, the optical fiber 9. A closed-loop optical transmission path is formed by the optical switch 1, and the optical signal continues to circulate through this loop, thereby realizing storage of the optical transmission state.

Since the storage capacity ff1B of the optical fiber 9 is until the optical fiber 9 is completely filled with the pulse train of the optical signal, if fc is the clock frequency that determines the modulation speed of the pulse train of the optical signal, then the following equation is obtained. Further, the storage time TS is as follows, where N is the number of turns of the optical fiber 9. However, it is necessary that the following equation holds true regarding the intensity P of the optical signal after TS.

One unit P=Po10 ≧Pr Here, A−N (αS+α・Jl)+αOL, Pr is the minimum reception intensity of the receiver, and Po is the intensity of the input light to the optical memory.Furthermore, αS, αr.

α0 is the optical switch 1. Optical fiber9. It is the attenuation temperature or attenuation coefficient of the bus fiber 8, and L is the length of the bus fiber 8 to the receiver.

When reading a signal stored in the loop of the optical fiber 9, the optical switch 1 is turned on to put the waveguides in a crossed state. In this way, the optical signal coming to the input side terminal 3 of the optical fiber 9 is outputted from the output side terminal 4 to the bus fiber 8. The time at which the signal is read out is as follows, if to is the time at which reading of the pulse train signal into the optical fiber 9 is completed.
By setting to +m·(n −J ri /C (m is an integer), the pulse train can always be read from the beginning.

In the experiment, the length of optical fiber 9 was set to 10! When R was used, the optical switch 1 was made of LiNbO3, and the clock frequency was 1008H2, an optical memory of about 4.9 kilobits was possible.

In the above embodiment, the input side terminal 2 is a signal writing terminal, and the output side terminal 4 is a signal reading terminal. In the case of reading out data, the output side terminal 4 becomes a signal writing terminal, and the input side terminal 2 becomes a signal reading terminal. (In this case, the input side terminal 2.3 of the optical switch 1 becomes the output side terminal, and the output side terminal 4.5 becomes the input side terminal.) Note that the signal storage optical fiber 9 in the above embodiment
If an optical repeater amplifier 10 is provided as shown in FIG.
The storage time of optical signals can be extended.

Furthermore, in the above embodiment, the optical switch 1 is of a 2x2 matrix, and there is only one optical fiber 9 for signal storage as a main medium, but as shown in FIG. 11 and connect the signal storage optical fibers 9 and 9 between the two pairs of input and output terminals respectively, it is possible to store signals in the two optical fibers 9 and 9 using one optical switch 11. Can be done. Similarly, if an nxn matrix optical switch is used, 2x2
The memory capacity can be increased by (n-1) times compared to the matrix type.

[Effects of the Invention] As described above, the present invention provides the following excellent effects.

(1) Since it is composed only of optical fibers and optical devices, it is difficult to receive electromagnetic induction, and there is no need for electrical or magnetic shielding, making it possible to reduce the weight and size of the storage device.

(2) When transmitting signals between computers or between memories using optical fibers, this can be easily and quickly done by switching optical switches without performing electrical/optical conversion or optical/electrical conversion.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing one embodiment of the optical memory according to the present invention, and FIGS. 2 and 3 are schematic diagrams showing other embodiments of the optical memory according to the present invention. In the figure, 1 and 11 are optical switches, 2.3 are input terminals, and 4
, 5 is an output side terminal, 6 is a changeover switch, 7 and 8 are bus cables, 9 is an optical fiber for signal storage, and 10 is an optical repeater amplifier.

Claims (2)

[Claims] (1) One of the input terminals of the optical switch in the n×n (n≧2) matrix is used as a signal writing terminal, and one of the output terminals of the optical switch is used as a signal reading terminal. An optical memory further comprising a signal storage optical fiber connected in a loop between the other input and output terminals of the optical switch in order to circulate and store the signal. (2) The optical memory according to claim 1, wherein the signal storage optical fiber is provided with an optical repeater amplifier.