JPS61259235A - Optical shift register circuit - Google Patents

Abstract

PURPOSE:To miniaturize and integrate the device by connecting plural optical bistable semiconductor laser that operates as an optical D flip-flop circuit by positive and negative clock signals longitudinally and taking out as an output of each bit. CONSTITUTION:Optical D flip-flop circuits 2A-2D are driven by positive and negative radio clock signals Ik, the inverse of Ik through electrodes 7, 8 and an optical digital signal LD inputted to an optical entrance 16 becomes a signal L01 in the circuit 2A and inputted to the circuit 2B and at the same time, taken out as a optical signal L1 from an outputting section 23 through a branching part 17. Similarly, signals L2-L4 are obtained in circuits 2B-2D and each optical signal L1-L4 is delayed by 1 bit. Accordingly, the device can be miniaturized and integrated by connecting optical D flip-flop circuits 2 through optical guide paths 13-15 and optical branching parts 17-19.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical shift register circuit, and more particularly to an optical shift register circuit suitable for optical communications, optical information processing, optical switching systems, and optical computers.

[Prior art and its problems]

In recent years, with the development of optical technologies such as optical fiber technology and optical semiconductor technology, long-distance optical communication systems for the purpose of backbone transmission, optical LANs for connecting distributed processing devices with high efficiency, and the like have been put into practical use. In these systems, optical technology was mainly used as a means of connection between functional devices, and the functional devices themselves were comprised exclusively of electronic circuits, mainly LSI.

In the near future, processing information will become more diverse and large in volume, and ultra-high processing speeds and processing complexity will be required.In order to meet these demands, optical technology will not only be used as a means of connection. It becomes necessary to use it as a logical processing means. In other words, it is possible to digitally process the transmitted optical digital signal as it is, output the result as light, and transmit it to other devices, which is a feature of light such as its high speed, broadband property, and non-inductive nature. Optical processing equipment (optical information processing systems, optical switching systems, etc.) that takes advantage of this will become essential.

In order to realize such an optical processing device, an inverter circuit and an O
Optical logic functional blocks such as optical gates, optical flip-flop circuits, optical shift register circuits, and optical counters having various functions such as R circuits, AND circuits, and exclusive OR circuits must be constructed.

However, in the past, there were not enough optical logic functional blocks for practical use.

[Purpose of the invention]

An object of the present invention is to provide a highly practical optical shift register circuit that is realized using a plurality of optical bistable semiconductor lasers.

[Structure of the invention]

The optical shift register circuit according to the present invention has a first electrode on a first electrode.
A plurality of optical bistable semiconductor lasers that operate as an optical D flip-flop circuit by applying a clock signal and a second clock signal to a second electrode are connected in cascade, and each output of the optical bistable semiconductor laser is connected in series. The configuration is such that each bit is extracted as an output.

〔Example〕

The present invention will be described in detail below using the drawings.

FIG. 1 shows an optical shift register circuit showing one embodiment of the present invention, and FIG. 2 is a timing chart for explaining the operation of this optical shift register circuit.

In this embodiment, the optical shift register circuit 1 includes four optical D flip-flop circuits 2A and 2B.

Consists of 2C and 2D. Before explaining this optical shift register circuit 1, it is first necessary to clarify the configuration of the optical D flip-flop circuit 2. The optical D flip-flop circuit is an optical circuit having the function of a D flip-flop, and is realized by applying two types of current clock signals having the following predetermined values to an optical bistable semiconductor laser. This will be explained in detail based on FIGS. 3, 4, and 5.

FIG. 3 shows an optical bistable semiconductor laser that implements an optical D flip-flop circuit by applying the driving method according to the present invention,
Figures 4 and 5 are characteristic diagrams showing various optical bistable relationships between input and output of an optical bistable semiconductor laser, and Figure 6 is a waveform diagram for explaining the operating characteristics of an optical D flip-flop circuit. and its relationship characteristic diagram is shown.

In FIG. 3, the optical bistable semiconductor laser 3 includes electrodes 7 and 8 on the P side that are electrically insulated by a slit 6 provided parallel to the Fabelli-Perot cavity surface 4.5. When the currents applied to the electrodes 7.8 are II and I2, if the current It is set to a predetermined value, an optical bistable characteristic can be provided between the current 2 and the optical output Pout.

Figure 4 shows the optical bistable characteristics between the current I2 and the optical output PoutO, where I + = ICI, IC2 (I
Two types of optical bistability characteristics when CI>IC2) 9.10
It shows. In the figure, the horizontal axis is electrician 2, and the vertical axis is optical output Po.
It is assumed to represent ut. The optical bistable characteristic 9 occurs when the current 1 is set to a constant value Ic2, and when the current I2 increases and reaches the threshold value Ith2, the optical output Pout suddenly increases and reaches the point P1. Even if the current I2 is subsequently increased, the optical output Pout only increases gradually and remains at a substantially constant value. On the other hand, when the current I2 decreases and reaches the threshold value Ith+ in such a high value state, the optical output Pou decreases at the point P2.
t suddenly decreases. In this way, I tril of current I2
The optical output Pout takes two stable states based on the two values of l I th2.

The optical bistability characteristic 10 occurs when the current 11 is set to a constant value Ic2, and two threshold values I at the current I2
stomach. The optical output Pout takes two stable states based on +Ith4. In this case, the relationship 1c2<Ic+ holds, and the threshold I ch3. I tha is the threshold value Ith++
It takes a value larger than I th2.

Next, based on FIG. 5, the optical input P of the optical bistable semiconductor laser 3 is
The optical bistability characteristic between in and optical output Pout will be explained. In this case, the current 11. Both I2 take fixed values. First, the optical bistable characteristic 11 shows that the current I is equal to the ICI
This is the characteristic obtained when the current 2 is set to a value rb+ smaller than the threshold I thl. In this optical bistable characteristic 11, when the optical input Pin increases from the point Q1 and reaches the threshold value Pthl, the optical output Pout suddenly increases and takes a high value PH. After that, even if the optical power Pin increases, the optical output Pout remains at a substantially constant value P.

is maintained. On the contrary, if the optical input Pin is decreased in such a high state, the threshold Pth is smaller than the threshold Pthl.
At th2, the optical output Pout suddenly takes a low value PL.

Furthermore, the optical bistable property 12 is such that the current 11 is controlled by the above-mentioned process. 2, and the current I2 is set to the intermediate value I between the threshold value I th3 and I.
This is the characteristic obtained when setting b2. In the optical bistable characteristic 12, when the optical input Pln increases and reaches the threshold value P th3, the optical output Pout suddenly becomes a high value P)I, and thereafter maintains substantially constant values P and I. On the contrary, if the optical input Pin is decreased in a state where the high value PH is taken, in this case, even if the optical input Pin becomes zero, the optical output Pout is located at the point Q2 and is maintained at the high value Po. It will remain as it is.

In the above, each current value I C+,' IC2r Ib is set so that the threshold value Pthl of the optical bistable characteristic 11 is smaller than the threshold value P th3 of the optical bistable characteristic 12.
l+Ib2 is set.

Next, by utilizing the various optical bistable characteristics 9, 10, 11, and 12 occurring in the optical bistable semiconductor laser 3 as described above, the manually inputted optical digital signal is output in synchronization with the rising edge of the current clock signal. A driving method for causing the optical bistable semiconductor laser 3 to function as an optical D flip-flop circuit will be described.

In FIG. 6, an optical digital signal having an amplitude value A is inputted as an optical input pin of the optical bistable semiconductor laser 3. In FIG. The amplitude value A is the threshold value P of the optical bistability characteristic 11
It is set to an intermediate value between thl and the threshold value P th3 of the optical bistable characteristic 12. The current I applied to the electrode 5 is the positive current clock signal 1. (first clock signal), and the logic value "0" has a current value I. 2, and the logical value “1” is the current value ■. , set. On the other hand, the current 2 applied to the electrode 8 is used as a negative current clock signal Ig (second clock signal), and the logic value "0" has a current value Ibl,
The current value Ib2 is set to the logical value "1". In the phase of this negative current clock signal Ik, there is a positive current clock signal ■
It has an inverse relationship with the phase of 2. In the above signal relationship,
The optical digital signal 1 is synchronized by the current clock signal I8, and a signal Lo is obtained as the optical output Pout.

FIG. 6 will be explained with respect to time t in the order of t, to t. First, time 1=1. Earlier, the amplitude value of the optical digital signal RI was 0 (logical value "0"), the current clock signal Ix was IC2, and the current clock signal Ix was Ib2. Therefore, the relationship between the optical input Pin and the optical output pout is governed by the optical bistable characteristic 12, and therefore the optical output Pout is maintained at a low value PL. Hence the optical output signal. is a logical value “
Take 0”.

Time 1=1. Then, the optical digital signal Ln has an amplitude value of A
fl (logical value “1”). At this time, the IC remains under the positive current clock signal IK and the negative current clock signal.
2, rb2 is maintained, so the optical bistable semiconductor laser 3 is excited to point Q in the optical bistable characteristic 12, but the optical output Pout is still maintained at a low value Pt. That is, the optical digital signal L0 has the logical value "
Even if the optical output signal becomes "1", the optical output signal remains at the logical value "0".

Time 1=1. When the positive current clock signal IK changes to ICI and the negative current clock signal T changes to Ibl, the optical bistable semiconductor laser 3 is dominated by the optical bistable characteristic 11. Therefore, when the amplitude value of the optical digital signal is Ao, the operating point is point Q4, and the optical output Pout is at a high value P.
Changes to □. Therefore, the optical output signal Lo has a logical value of "1" at this point. This causes the optical output signal to rise cl on the positive current clock signal IM. This means that the rises of are synchronized.

At time 1=13, under the positive current clock signal, IC2
Then, the negative current clock signal Ti changes to Ib2. As a result, the optical bistable semiconductor laser 3 is dominated by the optical bistable characteristic 12, and the optical digital signal remains at a high value An, so its operating point changes from point Q4 to point Qs. However, the optical output pout is maintained at a high value Pa.

Therefore, the optical output signal. is held at logical value "1".

Time 1=1. In this case, each current clock signal 1*, Ix is kept at the same value as above, and only the optical digital signal Lo changes its amplitude value to zero. However, since the optical bistable semiconductor laser 3 is governed by the optical bistable characteristic 12, the operating point moves from point Q5 to point Q2, and the optical output Pout is maintained at a high pH value. This is an optical digital signal. There is no optical output signal even if the value changes to logic “0”. means that it is held at the logical value "1".

At time t=ts, the amplitude value of optical digital signal Lo is 0.
The positive current clock signal I8 remains unchanged. 1, the negative current clock signal T, changes to Ib+, respectively. As a result, the optical bistable semiconductor laser 3 has optical bistable characteristics 11.
The operating point changes from point Q2 to point Q. Therefore, at this point, there is no optical output signal. changes from the logical value “1#” to the logical value “0”. This means that in response to the rising edge C2 of the positive current clock signal I, the optical output signal Lo changes to the logical value “0#” in synchronization with this. It means to become.

Time 1=1. Thereafter, at t7+t, t9, the above-described operation is repeated.

According to the above operation, the signal which is the optical output Pout.

is the optical digital signal Ln, which is the optical input Pin, when the current clock signal Ig rises CIn C2+ C3+ C4
＋CS.

This occurs due to a certain period of delay in synchronization with... Therefore, the optical bistable semiconductor laser 3 is controlled by the currents I+Hz) and I2 (I) applied to the electrodes 7°8 by setting the predetermined current values to logical values "1" and "0".
and an optical digital signal having a predetermined amplitude value Al11. By using as an optical input, it is possible to operate as an optical D flip-flop circuit, that is, an optical circuit having the function of a D flip-flop.

Next, the optical D flip-flop circuit 2 realized as described above
A 4-bit optical shift register circuit constructed using four of the following will be explained based on FIG.

In FIG. 1, four optical D flip-flop circuits (2A, 2B, 2C, 2D in the figure) are connected to light guide paths 13°, 14, 15
connected in cascade through. 16 is a light entrance part. Also, the light guide path 13.14.15. There is a light branching part 17°18
, 19 are provided, branch light guide paths 20, 21, 22 are formed, and thus light output portions 23, 24, 25, 26 are provided. Optical D flip-flop circuits 2A, 2B, 2C.

2D has electrodes 7 and 8, each electrode 7 is supplied with a positive current clock signal from a clock power source 27 (voltage Ec) via an amplifier 28, and each electrode 8 is supplied with a positive current clock signal via an inverting amplifier 29. A negative current clock signal T is applied to the optical D flip-flop circuits 2A and 2.
B, 2C, and 2D are driven by positive and negative current clock signals IM, IM.

The optical digital signal Lo is input to the light input section 16, and in the first stage optical D flip-flop circuit 2A, a current clock signal is input as shown in FIG. When C1 rises, an optical output signal is generated by rising in synchronization with C1. 1 is obtained. This optical output signal. 1 is input to the second stage optical D flip-flop circuit 2B via the light guide path 13, and is guided to the branch light guide path 20 via the light branching section 17, and is output to the output section 2.
3, the optical output signal is collected and taken out. The second stage optical D flip-flop circuit 2B receives the optical signal provided from the optical D flip-flop circuit 2A. 1 as an input signal, an optical output signal is generated in synchronization with the current clock signal If, as in the case of the first stage. You can get 2. In this way, the third stage optical D flip-flop circuit 2
At C, an optical output signal LO3 can be obtained, and at the fourth stage optical D flip-flop circuit 2D, an optical output signal can be obtained.

As shown in FIG. 2, the result output units 23, 24, 25, 26 output optical output signals L l +L 2 . based on the input optical digital signal LIll. L! l, L
This means that you can get 4. In this case, wipe
Optical D flip-flop circuits 2A, 2B, 2C, 2 in each stage
In D, it is assumed that the level of the optical output Pout of the optical bistable semiconductor laser forming each optical D flip-flop circuit is appropriately adjusted so that the logical value "1" is reliably obtained as a signal.

Therefore, as is clear from the above explanation and FIG. 2, the optical circuit shown in FIG. Signal L l* L 21 L 3 r
It has a function of generating L4, and is thus configured as an optical shift register circuit l.

In the above explanation, the optical bistable semiconductor laser 3 and the branch portions 17, 18 and 19 that constitute the optical D flip-flop circuit 2 are treated as separate parts for convenience, but it is possible to integrate these functions on a single substrate. For example, it is possible to realize a small, economical, and practical optical shift register circuit. Further, although a directional coupler is assumed as the optical branching section 17, 18, 19, the present invention is not limited to this, and any means can be used as long as it has a similar function. Further, in the above embodiment, a 4-bit optical shift register circuit has been described, but the present invention is not limited to this, and by cascading an arbitrary number of optical D flip-flop circuits 2, an optical shift register circuit with an arbitrary number of bits can be formed. It is possible to realize this.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, an optical D flip-flop circuit is constructed by applying two predetermined types of current clock signals and using a predetermined value of optical input in an optical bistable semiconductor laser. By cascade-connecting optical D flip-flop circuits via a light guide path and an optical branching section, it is possible to realize a compact, highly practical optical shift register circuit suitable for integration.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an optical shift register circuit according to the present invention, FIG. 2 is a timing chart explaining the operation of the optical shift register circuit, and FIG. 3 is a perspective view of an optical bistable semiconductor laser realizing an optical D flip-flop circuit. Figure 4 is a diagram showing the optical bistability characteristic that occurs between the current applied to the electrode and the optical output, Figure 5 is a diagram showing the optical bistable characteristic that occurs between the optical input and the optical output, FIG. 6 is a waveform diagram and a related optical bistable characteristic diagram for explaining the operating characteristics of the optical D flip-flop circuit. 1... Optical shift register circuit 2.2A, 2B, 2C, 2D... Optical D flip-flop circuit 3... Optical bistable semiconductor laser 7.8... Electrode 9, 10.11.12...・Optical bistable characteristics I,,I2・
...Current Pin...Optical input Pout...Optical output ■,...Positive current clock signal (first clock number) T,...Negative current clock signal (second clock number)

Claims (1)

[Claims] (1) An optical bistable semiconductor laser that operates as an optical D flip-flop circuit by applying a first clock signal to the first electrode and a second clock signal to the second electrode,
1. An optical shift register circuit, characterized in that a plurality of optical bistable semiconductor lasers are connected in series and each output of the optical bistable semiconductor laser is taken out as an output of each bit.