JPH0836897A - Light frequency multiplex type random access memory - Google Patents

Abstract

PURPOSE:To output only an optical signal desired to output to an output highway using a channel selector by allotting an arbitrary channel which is not stored now to a loop type optical waveguide delay line by a frequency converter of a control circuit for an optical signal on an input highway. CONSTITUTION:A control circuit 7 decides an optical frequency channel of an optical signal to be outputted by a 1X2 frequency channel selector 5 and informs the selector 5 and a frequency converter 2 of it. Therefore, a frequency channel of a optical signal existing in a loop type optical waveguide delay line 4 can be grasped, inputted to the delay line 4 through a coupler 3 and made multiplex. Only the optical signal of a channel desired to output out of multiplex signals is outputted through the 1X2 frequency channel selector 5, and the other signals are switched to the delay line and circulated. Thus, an input optical signal can be outputted to a different time slot using an output frequency multiplex type random access memory. When optical signals are stored in all channels, an input optical signal is quenched by the frequency converter 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a random access memory such as a memory for accumulating signals awaiting processing in signal processing and a memory for time slot conversion in an exchange, and more particularly to processing high speed optical signals. The present invention relates to an optical frequency multiplex type random access memory used in an optical computer, an optical switch, or the like.

[0002]

2. Description of the Related Art As an optical memory using a broadband optical delay line, in particular, as an optical random access memory for connecting a signal from an input highway to an arbitrary time slot on an output highway, for example, a configuration shown in FIG. 5 is considered. To be
The optical random access memory shown in FIG. 5 includes an input highway 61, a 1 × R switch 62, a signal discarding output means 63, loop optical waveguide delay lines 64a to 64c, and 2 × 2.
The switches 65 a to 65 c, the R × 1 switch 66, and the output highway 67.

In this optical random access memory,
One loop length of each loop-shaped optical waveguide delay line corresponds exactly to a time slot of an optical signal, and one loop-shaped optical waveguide delay line functions as one memory cell. The newly arrived signal is connected to an empty loop-shaped optical waveguide delay line using the 1 × R switch 62, and the 2 × 2 switch is crossed to be stored in the loop-shaped optical waveguide delay line.

While being accumulated, the 2 × 2 switch is kept in a bar state and circulated on the loop optical waveguide delay line. For the signal to be output, the 2 × 2 switch of the loop-shaped optical waveguide delay line stored is also set to the cross state,
Connect to output highway 67 using Rx1 switch 66. A signal input in a state where all the memories are filled is discarded through the discarding output means 63 using the 1 × R switch 62.

[0005]

In the conventional optical random access memory, a plurality of loop-shaped optical waveguide delay lines are required to satisfy a predetermined discard rate, and the number of loop-shaped optical waveguide delay lines increases as a whole. There was a problem.

The present invention has been made in view of the above,
It is an object of the present invention to provide an optical frequency multiplex type random access memory capable of forming an optical random access memory with one loop optical waveguide delay line.

[0007]

In order to solve the above-mentioned problems, the present invention firstly provides an arbitrary time slot on an output highway that is time-division multiplexed an optical signal on a time-division multiplexed input highway. An optical frequency multiplex type random access memory for outputting the optical signal from the input highway to a predetermined optical frequency channel, and one loop optical waveguide delay line for accumulating signals having different optical frequency channels. A frequency converter, a coupler for inputting an optical signal converted into a predetermined optical frequency channel by the frequency converter to the loop-shaped optical waveguide delay line, and an input terminal to one of the loop-shaped optical waveguide delay line. 1 × 2 with output terminal connected and the other output terminal connected to the output highway
The frequency channel selector and the optical frequency channel of the optical signal output from the other output terminal of the 1 × 2 frequency channel selector are selected, and the optical frequency channel of the optical signal currently stored in the loop optical waveguide delay line is selected. And a control circuit for allocating an optical frequency channel which is stored and is not accumulated in the loop-shaped optical waveguide delay line to an optical signal converted by the frequency converter.

Secondly, in the above-mentioned first structure, an optical amplifier for amplifying an optical signal circularly accumulated in the loop-shaped optical waveguide delay line is provided in the loop-shaped optical waveguide delay line. Is the gist.

[0009]

In the above structure, first, an optical frequency channel which is not stored in the loop optical waveguide delay line by the frequency converter is assigned to each optical signal input from the input highway. Then, it is input to the loop-shaped optical waveguide delay line by the coupler, is subjected to optical frequency multiplexing, and the input optical signals are collectively stored in one loop-shaped optical waveguide delay line.

Second, although the optical waveguide is generally a loss medium, an optical signal is circularly accumulated in one loop optical waveguide delay line by providing an optical amplifier in the loop optical waveguide delay line. Attenuation is prevented.

[0011]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram of an optical frequency multiplexing type random access memory. The optical frequency multiplexing type random access memory shown in FIG. 1 includes an input highway 1 into which an optical signal is input after time division multiplexing, a frequency converter 2, a coupler 3, a loop-shaped optical waveguide delay line 4, and a 1 × 2 frequency channel selector. 5, an output highway 6 for outputting a time-division multiplexed optical signal, and a control circuit 7 for outputting a control signal to the frequency converter 2 and the 1 × 2 frequency channel selector 5.

Based on the control signal from the control circuit 7, the optical signal on the input highway 1 is output by the frequency converter 2 to an arbitrary optical frequency of the optical frequency channels not currently stored in the loop optical waveguide delay line 4. Channels are allocated.

That is, the control circuit 7 determines the optical frequency channel of the optical signal to be output by the 1 × 2 frequency channel selector 5, notifies the 1 × 2 frequency channel selector 5 of this, and the frequency converter 2 converts the optical frequency channel. The optical frequency channel to be determined is determined and this is notified to the frequency converter 2. As described above, the control circuit 7 determines the optical frequency channel of the optical signal input to and output from the loop-shaped optical waveguide delay line 4, so that the optical frequency channel of the optical signal currently existing in the loop-shaped optical waveguide delay line 4 must be grasped. You can

The optical signal whose frequency has been converted by the frequency converter 2 is input to the loop-shaped optical waveguide delay line 4 via the coupler 3 and subjected to optical frequency multiplexing. If there is an optical frequency channel to be output among the optical frequency multiplexed signals stored in the loop optical waveguide delay line 4, only the optical signal of that optical frequency channel is set to 1 based on the control signal from the control circuit 7.
Output to the output highway 6 using the × 2 frequency channel selector 5. The optical signals of the other optical frequency channels are switched to the loop optical waveguide delay line 4 and circulated. In this way, the optical signal from the input highway 1 can be output to different time slots by using the optical frequency multiplexing type random access memory. When the optical signal is stored in all the optical frequency channels, the input optical signal is extinguished by the frequency converter 2.

Further, since the optical waveguide is generally a loss medium, an optical amplifier (not shown) is installed in the loop-shaped optical waveguide delay line 4, and the optical amplifier is circularly accumulated in the loop-shaped optical waveguide delay line 4. By amplifying the existing optical signal, the attenuation of the optical signal can be prevented.

FIG. 2 shows a configuration example of the frequency converter 2. The frequency converter 2 shown in FIG. 2 includes an input highway 1a before optical frequency conversion, a light receiver 21, a frame synchronization detection circuit 22, a first variable frequency oscillation semiconductor laser 23, a second variable frequency oscillation semiconductor laser 24, It is composed of a high-speed optical switch 25, a control signal line 26 from the control circuit 7, a frequency conversion control circuit 27, an external modulator 28, and an input highway 1b after frequency conversion.

The time-division signal from the input highway 1a is converted into a high-speed electric signal by the photodetector 21 and drives the external modulator 28. A frame is detected from the electric signal by using the frame synchronization detection circuit 22, and the frame is input to the frequency conversion control circuit 27 together with the control signal from the control circuit 7. The frequency conversion control circuit 27 controls the first and second variable frequency oscillation semiconductor lasers 23 and 24 and the high speed optical switch 25.

Specifically, the optical frequencies of the two variable frequency oscillation semiconductor lasers 23 and 24 are alternately converted so that a predetermined optical frequency channel can be set at high speed, and the high speed optical switch 25 selects them alternately. . This is because the optical frequency conversion speed of the laser is slower than the switching guard time of the time slot. Thereafter, the driven external modulator 28 carries a signal and outputs the signal to the input highway 1b. In this configuration, if the frame detection of the optical signal and the optical control direct modulation of the optical control external modulator or the variable frequency oscillation laser are possible, the all-optical configuration is also possible.

FIG. 3 shows a configuration example of the 1 × 2 frequency channel selector 5. In FIG. 3, the 1 × 2 frequency channel selector 5 is connected to an input terminal 51 connected to the loop-shaped optical waveguide delay line 4, one output terminal 52 connected to the loop-shaped optical waveguide delay line 4, and an output highway 6. The other output terminal 53, the ring-shaped optical resonator 54, the directional couplers 55 and 56, the phase shifter 57, the phase shifter setting power supply 58, and the control signal line 59 from the control circuit 7.

Of the optical frequency multiplexed signals input from the input terminal 51, only the signal in the optical frequency channel that matches the resonance frequency determined by the optical path length of the ring-shaped optical resonator 54 is output from the other output terminal 53, The other signals are output from one output terminal 52. The resonance frequency is based on the control signal input via the control signal line 59, and the phase shifter setting power supply 58 is used to adjust the phase shifter 57 to change the optical path length of the ring-shaped optical resonator 54. Can be adjusted to any channel. That is, it becomes possible to connect only the signal of an arbitrary optical frequency channel to the output highway 6 and allow the other signals to stay in the loop optical waveguide delay line 4 again. Signals can be selected at high speed by adjusting the phase shifter 57 for each time slot.

FIG. 4 shows an operation time chart of the optical frequency multiplex type random access memory. First, signal A,
When the signal C is input where B is stored,
The frequency is converted to f3 which is an empty channel and stored in the loop. The next input signal D is also converted into the empty channel f4 and stored. At this time, when the signal B is output, the next input signal E is converted into f2. In this way, a plurality of signals can be accumulated in one loop-shaped optical waveguide delay line 4 by converting the input signal into the optical frequency channel which is always free.

[0022]

As described above, according to the invention described in each claim, the following effects are obtained.

According to the first aspect of the present invention, one loop-shaped optical waveguide delay line for accumulating signals having different optical frequency channels and a frequency for converting an optical signal from the input highway into a predetermined optical frequency channel. A converter, a coupler for inputting an optical signal converted into a predetermined optical frequency channel by the frequency converter to the loop-shaped optical waveguide delay line, an input terminal and one output terminal of the loop-shaped optical waveguide delay line Is connected and the other output terminal is connected to the output highway, and the optical frequency channel of the optical signal output from the other output terminal of the 1 × 2 frequency channel selector is selected and the loop The optical frequency channel of the optical signal stored in the loop optical waveguide delay line and stores the optical frequency channel not stored in the loop optical waveguide delay line. Since a control circuit for allocating a channel to an optical signal converted by the frequency converter is provided, an optical frequency channel not stored in the loop optical waveguide delay line is allocated and optical frequency multiplexed for each input optical signal. Therefore, the input optical signals can be collectively stored, and the optical random access memory can be configured by one loop optical waveguide delay line.

According to the second aspect of the invention, one optical amplifier is provided in the loop-shaped optical waveguide delay line for amplifying the optical signal circularly accumulated in the loop-shaped optical waveguide delay line. It is possible to prevent the attenuation of the optical signal accumulated in the loop optical waveguide delay line.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an optical frequency multiplex type random access memory according to the present invention.

FIG. 2 is a block diagram showing a configuration example of a frequency converter in the above embodiment.

FIG. 3 is a diagram showing a configuration example of a 1 × 2 frequency channel selector in the above embodiment.

FIG. 4 is an operation time chart of the above embodiment.

FIG. 5 is a block diagram of a conventional optical random access memory.

[Explanation of symbols]

 1 Input Highway 2 Frequency Converter 3 Coupler 4 Loop Optical Waveguide Delay Line 5 1 × 2 Frequency Channel Selector 6 Output Highway 7 Control Circuit

Claims (2)

[Claims] 1. An optical frequency multiplexing type random access memory for outputting an optical signal on a time-division multiplexed input highway to an arbitrary time slot on a time-division multiplexed output highway, wherein the optical frequency channels are different. One loop-shaped optical waveguide delay line for accumulating a signal, a frequency converter for converting an optical signal from the input highway into a predetermined optical frequency channel, and a frequency converter for converting the optical signal into a predetermined optical frequency channel by this frequency converter A coupler for inputting an optical signal to the loop-shaped optical waveguide delay line, and an input terminal and one output terminal connected to the loop-shaped optical waveguide delay line, and the other output terminal connected to the output highway 1 × 2 When the frequency channel selector and the optical frequency channel of the optical signal output from the other output terminal of the 1 × 2 frequency channel selector are selected, In addition, the optical frequency channel of the optical signal currently stored in the loop-shaped optical waveguide delay line is stored, and the optical frequency channel not stored in the loop-shaped optical waveguide delay line is converted by the frequency converter. An optical frequency multiplex type random access memory, comprising: 2. The optical amplifier according to claim 1, wherein an optical amplifier for amplifying an optical signal circularly accumulated in the loop-shaped optical waveguide delay line is provided in the loop-shaped optical waveguide delay line. Optical frequency multiplexing random access memory.