JPH02226235A - Optical sampling memory device - Google Patents

Abstract

PURPOSE:To convert duty by setting the input power of a clock pulse between the rise threshold value and fall threshold value of an optical bistable element and superposing the output light pulse from an optical threshold value element thereupon. CONSTITUTION:An optical frame pulse is inputted to the optical threshold value element 2 while superposed upon a desired bit of an optical data sequence on an optical communication line. Then only the light data of the bit where the light frame pulse is superposed is allowed to exceed a threshold value and only the light data is outputted. The output of the element 2 is inputted to the optical bistable element 5 while the light clock is superposed. Here, the input power of the light clock pulse is between the rise threshold value and fall threshold value of the element 5 and allowed to exceed the rise threshold value of the element 5 when the output light pulse from the element 2 is superposed thereupon, so that the input light pulse from the element 2 is converted into the duty of the light clock pulse, which is outputted. Consequently, the duty is made large and, therefore, the pulse width is widened to facilitate subsequent processing.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention selectively extracts only desired data from a data string on an optical communication path that is multiplexed on the time axis, and performs duty conversion on the data. The present invention relates to an optical sampling memory device.

With the development of optical communication networks, various studies have been conducted in recent years on methods for exchanging signals using light. Among these, optical fibers are being introduced to subscribers to deliver high-speed, large-capacity optical signals such as image signals to subscribers, and optical subscriber transmission networks are being developed to exchange such information between subscribers. Realization is one of the challenges for realizing optical communication networks in the future.

For this purpose, it is necessary to perform signal processing such as signal branching, signal insertion, and cross-connection between the optical highway (optical communication path) and the optical subscriber.

[Conventional technology]

In conventionally proposed optical subscriber networks, transmission processing nodes are placed on the optical highway to provide access between the optical highway and optical subscribers. An example of the configuration of such a transmission processing node is disclosed in, for example, [Fujimoto et al., IEICE Technical Report, C387-90].

There are three basic processing functions:

■Branch processing to retrieve desired data from the optical trunk line to the optical subscriber terminal.

■Insertion processing that transmits data from optical subscribers into empty time slots on the optical highway.

■Cross-connect processing that swaps time slots of data on the optical highway.

In conventionally proposed examples, all of the above processes are
It relies on processing electrical signals. Specifically, for example, in branching processing, an optical signal on an optical highway is converted into an electrical signal at a photoelectric conversion unit of a transmission processing node, and then branched at the electrical signal level and sent to an electrical/optical conversion unit for subscribers. It is converted into an optical signal for subscribers and transmitted. In addition, in the insertion process, an optical signal from a subscriber is converted into an electrical signal by a photoelectric conversion unit, merged with optical highway data, and then converted into an optical signal by an electrical/optical conversion unit for the optical highway. It takes the form of sending it out on the optical highway.

[Problem to be solved by the invention]

However, handling ultra-high-speed optical signals on the optical highway,
Moreover, in order to electrically perform branching, insertion, cross-connection, etc. for multi-channel optical subscriber lines, ultra-high-speed, multi-channel photoelectric conversion processing units and electrical signal processing units are required. Therefore, as the capacity of the signals handled increases, these processing units become a bottleneck in terms of processing speed, and as the number of channels increases, the processing equipment becomes large-scale. there were.

The present invention eliminates such conventional drawbacks and provides an optical signal that is the basis for performing branching, insertion, and cross-connection without converting the optical signal on the optical communication path into an electrical signal. An object of the present invention is to provide an optical sampling memory device capable of selectively extracting data and converting the duty (pulse width).

[Means to solve the problem]

In order to achieve the above object, the optical sampling memory device of the present invention, as shown in FIG. An optical threshold element 2 that produces a large optical output when the input exceeds a threshold value, and an optical frame pulse that is selectively superimposed on desired bits of the optical data string are input to the optical threshold element 2. Optical frame pulse generating means 3
, the optical output has hysteresis characteristics with respect to the optical input,
An optical bistable element 4 into which the output optical pulse from the optical threshold element 2 is input, and an optical bistable element 4 which superimposes the input optical pulse from the optical threshold element 2 to convert its duty. It is characterized in that it has an optical clock generation means 5 which is input to the stable element 4.

[Effect]

An optical frame pulse is input to the optical threshold element 2 so as to be superimposed on a desired bit of an optical data string on an optical communication path. Then, by making only the optical data of the bit on which the optical frame pulse is superimposed exceed the threshold value, only that optical data is outputted from the optical threshold element 2. In this way, only the desired bits of optical data can be
It can be extracted from the optical data string.

Next, an optical clock is superimposed on the output optical pulse from the optical threshold element 2 and input to the optical bistable element 4 . Here, the input power of the optical clock pulse is applied to the optical bistable element 4.
is between the rising threshold and the falling threshold of , and when the output optical pulse from the optical threshold element 2 is superimposed on it, the rising threshold of the optical bistable element 4 is exceeded. An input optical pulse from the optical threshold element 2 is converted into an optical clock pulse duty and output. As a result, the duty can be increased, that is, the pulse width can be increased, and subsequent processing can be easily performed electrically.

〔Example〕

Examples will be described with reference to the drawings.

FIG. 2 shows an embodiment of an optical sampling memory device that branches optical data from an optical communication path.

Here, for example, an optical data string of 1-n pulses, that is, n-channel optical data is transmitted on the optical communication path (optical highway) (2). 11 and 12 are first and second optical couplers, which branch and take out the optical data string from the optical communication path l. An optical clock extraction circuit 13 is connected to the optical output end of the first optical coupler 11, and extracts an optical clock from the bit rate of the optical data string.

An optical frame pulse generator 3 and an optical clock generator 5 are connected to the optical output end of the optical clock extraction circuit 13. Then, based on the optical clock extracted by the optical clock extraction circuit 13, an optical frame pulse and an optical clock are generated.

In the optical clock generator 5, the bit rate B of the optical data string is
and the frequency determined by the multiplicity N (for example, B/N
) is generated and outputted, and the power Pc of the optical clock pulse is smaller than the rising threshold Pon of the optical bistable element 4, which will be described later, and the falling threshold Po.
larger than ff. Further, the power Pb of the bias component between clock pulses is smaller than the falling threshold Poff, and the power Pc + Pdata of the light obtained by superimposing the data light pulse on the clock pulse is larger than the rising threshold POn.

That is, POff < Pc < Pon
Pc + Pdata) Ponkatsu Pb
<Poff.

In the optical frame pulse generator 3, the channel selection circuit 3
data of an arbitrary channel (for example, the first channel) is selected from the n-channel optical data string by a, and an optical frame pulse is output in accordance with the timing of the bit of that channel. The power Pf (height) of this optical frame pulse is smaller than the threshold value Pth of the optical threshold element 2, which will be described later, and the power (height) Pf of the optical pulse obtained by superimposing the optical data pulse on the optical frame pulse.
+Pdata is set to be larger than the threshold value pth. That is, Pf, Pda'ta < Pth.

and Pf + Pdata > Pth It is.

An optical threshold element 2 is provided at the optical output end of the second optical coupler 12.
is connected. This optical threshold element 2 is shown in FIG.
As shown in A), the optical input Pin is the threshold value pth
When below, there is no optical output and the optical input is at the threshold pth
If it exceeds Pout, it has a characteristic (differential gain characteristic) that allows a large optical output Pout to be obtained.

This optical threshold element 2 receives an optical data pulse inputted from the second optical coupler 12 and an optical frame pulse generator 3.
The 41st optical frame pulse is superimposed with the optical frame pulse input from the 41st
As shown in J(B), the optical frame pulse is superimposed only on the data of the i-th channel, and the threshold value pt
It becomes a pulse with a power exceeding h. As a result, the optical threshold element 2 outputs only optical data in which an optical frame pulse is superimposed on the bit (data) of the i-th channel, as shown in FIG. 4(C).

In this way, only desired optical data can be extracted from the optical data string. Examples of elements and physical phenomena with such characteristics include the differential gain characteristics of semiconductor laser amplifiers, examples of which are rT, Nak
ai, et am.

Jpn, J., Appl, Phys.
22° Li2O (1983) J.

The output light from the optical threshold device 2 is input to the optical bistable device 4 . The optical bistable element 4 has a hysteresis characteristic in the optical output P out with respect to the optical input Pin, as shown in FIG. 5(A), for example. In this optical bistable element 4, the input optical pulse from the optical threshold element 2 and the optical clock pulse from the optical clock generator 5 are superimposed as shown in FIG. 5(B). Then, the optical bistable element 4 is excited from the "L" state to the "H" state by the optical data. Even if there is no optical data, it remains "H" until the optical clock falls due to the hysteresis characteristic.

As a result, the optical bistable element 4 outputs an optical pulse in which the pulse width of the input optical pulse is expanded to the pulse width of the optical clock pulse, as shown in FIG. 5(C). In this way, the duty of the optical pulse is expanded. In this way, the output duty of optical data is arbitrarily converted according to the pulse width of the optical clock, and the optical subscriber terminal
It can be sent to O.

Examples of elements and physical phenomena with such characteristics include the hysteresis characteristics of optical bistable semiconductor lasers and optical memory operations that utilize them. Object, 29 pages
-ZH-7, 1987'' and ``Suzuki et al., Spring 1981, IEICE University, 517-13J.

FIG. 3 shows an embodiment of a circuit for inserting an optical signal into the optical communication path l. In the figure, 21 is a timing adjustment circuit that outputs an optical frame pulse in accordance with the timing of an empty time slot on the optical communication path l into which an optical signal is inserted. Here, an optical frame pulse is input from the optical frame pulse generator 3 mentioned above, waits for the output of the optical frame pulse according to timing information from the optical communication path 1 side, and adjusts the timing to an empty time slot on the optical communication path 1. outputs an optical frame pulse. The optical frame pulse is superimposed on the optical input signal j input from the optical subscriber terminal IO and input to the optical threshold element 2.

In this optical threshold element 2, the duty conversion of the optical signal acts in the direction of reducing the duty, contrary to the case shown in FIG. It is output with the same pulse width as the data, and merges into the optical communication path l by the optical coupler 22. At this time, since data i exists in the time slot where data j enters,
This must be removed. Therefore, an optical data erasing circuit 23 is used. There are several possible ways to implement the optical erasing circuit 23, but since they are not directly related to the present invention, their explanation will be omitted here.

In this way, the optical signals on the optical communication path 1 can be branched and added as they are without converting them into electrical signals.

In the above embodiment, the optical clock extraction circuit 13 extracts the optical clock signal directly from the data light (without converting it into an electrical signal); A data receiving circuit may be used to extract the clock at the level of the electrical signal. Furthermore, in order to recover optical signal loss within this node, an optical amplifier may be inserted, or an optical repeater may be placed on the optical communication path l.

〔Effect of the invention〕

According to the optical sampling memory device of the present invention, a desired optical signal on an optical communication path can be selectively extracted as an optical signal without converting it into an electrical signal, and an optical signal can also be inserted by the reverse operation. It can be carried out. Therefore, it is possible to realize an all-optical processing type transmission processing node that can process optical signals without converting them into electrical signals.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the present invention, Figs. 2 and 3 are block diagrams of an embodiment, Fig. 4 is a diagram showing the operation of the optical threshold device, and Fig. 5 is the operation of the optical bistable device. FIG. In the figure, ■--optical communication path, 2--optical threshold element, 3--optical frame pulse generating means, 4-- optical bistable element, 5-- optical clock generating means. ■6

Claims (1)

[Claims] An optical threshold value where an optical data string is input from an optical communication path, and when the optical input is below the threshold value, there is no optical output, and when the optical input exceeds the threshold value, a large optical output is obtained. an element (2); an optical frame pulse generating means (3) for inputting an optical frame pulse to be selectively superimposed on a desired bit of the optical data string to the optical threshold element (2); an optical bistable element (4) whose optical output has a hysteresis characteristic and into which the output optical pulse from the optical threshold element (2) is input; and the input light from the optical threshold element (2). An optical sampling memory device characterized by comprising an optical clock generating means (5) for inputting an optical clock that is superimposed on a pulse to convert its duty into the optical bistable element (4).