JPS61113199A - Optical shift register circuit - Google Patents

Abstract

PURPOSE:To calculate and process transmitted optical digital data as it is by setting an optical D flip-flop composed of an optical switch and optical bistable element to a basic circuit. CONSTITUTION:The optical D flip-flop circuits 101-104 are continuously connected, and respective connection parts are constituted of optical branching devices K1-K4 composed of directional couplers used for taking out optical output signals L1-L4 at respective D flip-flop stages. In the optical D flip-flop circuit, that is, the basic block of an optical shift register circuit, the directional coupler optical switch 8 and the optical bistable element 9 are continuously connected. Said switch 8 is arranged by the directional coupler 7 formed on a substrate (made of LiNbO3, GaAs, InP, etc.) and control electrodes 5 and 6. When a voltage signal is impressed to the control electrodes 5 and 6, the switch 8 can have two states.

Description

[Detailed Description of the Invention] <Industrial Application Fields> Optical communication systems, optical information processing systems, optical switching systems, optical combination systems, etc. (related to optical digital/digital logic circuits used).

<Prior Art> In recent years, with the development of optical fiber technology and optical semiconductor technology, long-distance optical communication systems for backbone transmission and optical LAN systems that connect distributed processing devices with high efficiency have been put into practical use.

In these systems, light wave technology is mainly used as a means of connection between functional devices, and the functionality is solely dependent on electronic circuit technology centered on LSI.

Reflecting the advent of a highly information-oriented society in the near future, as the information to be processed becomes more diverse and larger in volume, there are demands for ultra-high processing speeds and increasingly complex processing.

In order to meet these demands, it has become necessary to use light wave technology not only as a connection means but also as a logical processing means.

In other words, the transmitted optical digital signal.

It can perform digital arithmetic processing on the light itself, output the processing results as light, and transmit them to other devices. Optical processing equipment (
optical information processing systems, optical switching systems, etc.) will be essential.

To implement this type of device, optical logic functional blocks similar to those used in general electrical logic circuits, such as INVERTOR, OR, AND, are used.

(EXOR, etc.), an optical flip-flop circuit, an optical shift register circuit, an optical quantator, etc. must be constructed.

Until now, none of these optical logic functional blocks have been put to practical use.

<Object of the Invention> In view of the above, an object of the present invention is to provide a practical optical shift register circuit that is compact and suitable for integration.

<Configuration of the Invention> There are two original register circuits of the present invention, one of which is the first register circuit.
It has a configuration having an input end, a second input end, and an output end. The other is an optical flip-flop consisting of a 2×1 optical switch having a first input terminal, a second input terminal, and an output terminal, and an optical bistable element whose optical input is the optical output from the output terminal. Connect multiple circuits in cascade via optical splitters,
The optical flip-flop circuit of the optical splitter has a configuration in which the unconnected output end is the intermediate tap output end.

<Example> Next, one of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an optical shift register circuit showing a first embodiment of the present invention. In this circuit, optical D 7 +j block flop circuits 101, 102, 103, and 104 are connected in series.

Each connection part has an optical output signal L of each optical D flip 70-tube stage.
*-Lt-Ls, optical splitter Kt, Kt-Ks, Ka consisting of a directional coupler for taking out L4
It is made up of many things.

Before explaining the operation of the optical shift register circuit.

The configuration and operation of the optical D flip-flop circuit will be explained.

FIG. 2 shows an optical D flip-flop circuit which is a basic block of the original shift register circuit according to the present invention, in which a directional coupler type optical switch 8 and an optical bistable element 9 are connected in cascade. The directional coupler type optical switch 8 has a substrate (LiNbQ,
, GaAs, InP, etc.) and control core poles 5 and 6. By applying voltage signals to the control poles 5, 6, two states can be created in the switch 8. In other words, there is a state in which the optical signal from input end 1 is conducted to output end 4 and an optical signal from input end 2 is conducted to output end 3 (this is called a bar state), and an optical signal from input end 1 is conducted to output end 4. 3 and the original signal from the input end 2 is conducted to the output end 4 (this is called a cross state). As shown in FIG. 7, in the optical bistable element 9, the optical output pout shows a history with respect to changes in the optical input Pin, and within a certain input intensity range (a competition between the threshold P and the threshold PtM), Two stable output intensities PH and PL are taken.

As an example of a device having such optical bistable characteristics, an optical bistable semiconductor laser shown in FIG. 8 has been announced (National Conference of the Institute of Electronics and Communication Engineers, &937 (1983)).

Optical bistable semiconductor lasers are fabricated using a Fabelli-Perot cavity.
It has two divided P8 electrodes 31 and 32 that are electrically insulated by a slit 33 provided in parallel to P8. 1 each! Appropriate bias current I to poles 31, 32, 1. As a result, the relationship between the optical input pinY and the optical output pout can have an optical bistable characteristic as shown in FIG.

Now, the logical operation of the optical D flip-flop circuit used in the present invention will be explained with reference to FIG.

As shown in FIG. 5, the optical amplitude value of the optical digital data LD, which inputs the optical digital data LD to the input terminal 1 and the bias light LB to the input terminal 2, is zero in the logic "0" state and logic 11. ``In the state, it is PD.

On the other hand, the bias light LB is a DC light whose optical amplitude value is a DC amplitude value PB, as shown in FIG. By applying an electric clock Ect- to electrodes 5 and 6, optical switch 8 is controlled. When the electric clock EC is in the logic @1'' state, the optical switch 8 is set to the cross state, and when it is in the logic "0" state, the optical switch 8 is set to the bar state.

Here, the optical switch 8 is designed to have a coupling degree α (≦1) in the cross-shaped M4C. Therefore, depending on the logic state of the hypochondriacal clock EC, the light switch 8
The optical output signal LAW to the output end 3 of is determined as follows.

When the electrical clock EC is in the logic @0# state, the optical switch 8 is in the bar state, so the optical output signal Lsw is the bias light LB itself, and its optical amplitude value is PB. On the other hand, when the electric clock EC is in the logic "l#" state, the optical switch 8 takes a cross state, so the optical digital data L
An optical output signal Lsw depending on the logic state of D is obtained.

That is, when the optical digital data D is in the logic 111 state, a portion αPB of the optical amplitude value PR of the bias light LB is coupled to the output terminal 4, and a portion αPD of the optical amplitude value PD of the optical digital data LD is coupled to the output terminal 4. Since it is coupled to the output end 3, the optical amplitude value of the optical output signal L8W becomes PB-αPB+αPD. On the other hand, when the optical digital data LD is in the logic "0" state, the optical amplitude value of the optical digital data LD is zero, so there is no coupling from the optical digital data LD to the output terminal 3.
A part αPB of the optical amplitude value PB of the bias light LB is output at the output end 4.
It is only connected to Therefore, the optical output signal LI9W
The optical amplitude value of is P, -αPB.

The relationship between the above truth values and optical amplitude values is summarized in Figure 6. The optical amplitude value PB - αPIS + αPD is the DC amplitude value PB.
If the degree of coupling α and the optical amplitude value PD are selected so as to be large, the optical output signal L8WK becomes as shown in FIG.
A positive pulse P having +αPB and a negative pulse N having an optical amplitude value P and -αPB are obtained.

After all, in the optical output signal L3W, the baseline B is generated when the electrical clock Ec is in the logic "O" state, and when the electrical clock Ec is in the logic "1" state and the original digital data LD
When is in the logic "1" state, a positive pulse P is generated, and when the electric clock EC is in the logic @1' state and the optical digital data LD is in the logic "0" state, a negative pulse N is generated. Next, returning to FIG. 2, the optical output signal I'sw is input to the optical bistable element 9.

As shown in FIG. 7, if the characteristics of the optical bistable element 9 and the optical width value of the optical output signal Lsw satisfy the relationship of formula Fl), the optical bistable element 9 is set to a high value by the positive pulse P, The negative pulse N sets the low value PL, and the baseline B (bias light LB) biases it to either the stable point Q1 or Q, and the low value PL2>A high value P
It is held at H. As a result, the output optical digital data Lo
is obtained as shown in FIG. After all, the output optical digital data L.

K is, as shown in Fig. 5, when the optical digital data LD is Cr1 r Crt +... at the rising edge of the electric clock gc.
A highly synchronized optical signal can be obtained. Therefore, the circuit of FIG. 2 realizes the optical D flip 70 operation.

Now, returning to FIG. 1, the operation of the optical shift register circuit of the present invention will be explained.

By cascade-connecting the above-mentioned optical D flip 70 block circuits through optical splitters Kt, Kt, Ks, and K4 each consisting of a directional coupler, and applying an electric clock EC to each optical D71J block circuit in common, A post 4-bit optical shift register circuit is realized in the ts1 diagram.

Optical output signal L'61 yL of each party D7 lip-flop stage
As mentioned above, Ibt y L'j3 is sent to the next stage optical D flip 70 tubes 102, 103, 104! Electricity a
It is synchronized at the rise of y-Ec.

Therefore, the optical output signals Ln, Lt, Ls, L4 from *, Kt - Ks, 4 to the optical splitter are as follows:
As shown in FIG. 9, for optical digital data LD,
1bit delay, zbit delay, 3bit delay, 4bit
Delayed optical output signals are each obtained.

The above is a row in which 70 optical flip-flop circuits are connected via an optical splitter, but the optical splitter may be omitted and the flip-flop circuit 1 may be connected directly.However, in this case, the final stage Deba can only be obtained from Kara.

The same can be said of the second implementation column shown below.

Next, a second embodiment will be explained. FIG. 3 shows an optical shift register circuit showing a second embodiment of the present invention.

Similar to the first embodiment, the optical D flip-flop circuit 10
1, 102, 103, 104 as branch switches Ks, Kt
, Ks-Ka are connected in series.喀-
The difference from the embodiment described above is that, as shown in FIG. 4, a crossed waveguide optical switch 8 is used as the optical switch constituting the optical D flip-flop circuit.

Therefore, here, only the operation of the optical D flip-flop circuit using the crossed waveguide type optical switch 8' will be explained with reference to FIG. The crossed waveguide type optical switch 8' is composed of a crossed waveguide 10 formed on a substrate (LtNbOs #GaAs y InP, etc.) and control electrodes 5 and 6. When the electric clock EC applied to the control electrode 5.6 is in the logic "02" state, the optical digital data LD at the input terminal 1
is connected to the output end 4, and the bias light of the input end 2 is connected to the output end 3. Therefore, the optical output signal Lsw becomes the bias light LB itself.

On the other hand, when the electric clock EC applied to the control electrodes 5 and 6 is in the logic 11" state, the optical pickup width value PB of the bias light LB is A part of αPB is coupled to the output end 4, and the remaining light silkworm width ([P
B-αPB is output to the output terminal 3.

Further, to the output terminal 3, when the optical digital data Lo Z>"logic"1" state, a part αPD of the optical shaking value PD is output, and when the optical digital data LD is in the logic @O" state, nothing is output. Not done. Here, the degree of coupling of the optical switch 8 is α
(≦1).

As described above, as in the first embodiment, an optical output signal Ltsw having a positive pulse P and a negative whisper pulse N with the baseline B as an intermediate value is obtained. When the optical output signal LAW is input to the optical bistable element 9, the optical digital data LD is outputted optical digital data L synchronized with the electric clock EC. can be obtained.

Therefore, it is clear that FIG. 4 can operate as an optical D flip-flop. If optical D flip-flop circuits are connected in cascade, the first implementation column and 11511 in FIG. 3 operate as original shift register circuits.

Above, in the description of the first example and the second example A,
Although the original switch, optical bistable element, and optical splitter were treated as separate components, it is obvious that a compact and economical original shift register circuit can be realized by integrating these functions on a single board. It is.

In addition, in the above explanation, the optical switch is a directional coupling type optical switch and a crossed waveguide type optical switch.

Although an optical bistable semiconductor laser is used as an optical bistable element and a directional coupler is arranged as an optical splitter, the invention is not limited to these, and any optical device of the present invention can be used as long as it satisfies the functions described above. It is also obvious that a shift register circuit can be realized6.Furthermore, in the above embodiments, a 4-bit optical shift register has been explained as an example, but the optical D flip-flop circuit can be implemented in any number of numbers without being limited to this. It is obvious that a multi-bit optical shift register circuit can be realized by cascade connection.

<Effects of the Invention> As explained above, a practical optical shift register circuit that is compact and suitable for integration has been realized using an optical D flip-flop consisting of an optical switch and an optical bistable element as a basic circuit. Therefore, it becomes possible to perform digital calculation processing on the originally transmitted digital data without changing the optical state, making a major contribution to the construction of high-speed optical information processing systems, optical switching systems, and optical combinators.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an optical shift register according to a first embodiment of the present invention. FIG. 2 is a circuit diagram of an optical D flip 70 constituting the optical shift register circuit of the first embodiment. Fig. 3 is a circuit diagram of an optical shift register according to a second embodiment of the present invention, Fig. 4 is a circuit diagram of an original D flip-flop that is used as the original shift register circuit of the second embodiment, and Fig. 5 is an optical D7 circuit diagram. 'Logical waveform diagram of each part of the J-tube flop circuit, Figure 6 is the truth table of the original switch, Figure 7 is the characteristics of the optical bistable element and the optical input signal Ls to it.
w and Deba Hikari Digital Data L. 8 is a schematic diagram of an optical bistable semiconductor laser, and FIG. 9 is a timing chart of an optical shift register circuit. 101.102,103,104... Optical D flip-flop circuit 8... Source switch, 9... Optical bistable element LD.
...Optical digital data. EC...Electric clock, L8...Bias light. 4j4 Tei 7 Figure pout half 8 Figure Pout37 79 figure

Claims (2)

[Claims] (1) 2× having a first input terminal, a second input terminal, and an output terminal
An optical flip-flop circuit consisting of an optical switch and an optical bistable element whose optical input is the optical output from the output terminal is configured such that the optical output from the optical bistable element is input to the first input terminal of the next stage. An optical shift register circuit characterized in that a plurality of optical shift registers are connected in cascade. (2) 2× having a first input end, a second input end, and an output end
A plurality of optical flip-flop circuits each consisting of an optical switch and an optical bistable element whose optical input is the optical output from the output terminal are connected in cascade through an optical branching device, and the optical flip-flop circuit of the optical branching device is An optical shift register circuit characterized in that the output end not connected to the output end is an intermediate tap output end.