JP2662288B2 - Optical sampling memory device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] An optical sampling memory device that selectively extracts only desired data from a data string on an optical communication channel multiplexed on a time axis and performs a duty conversion thereof is provided. Selective extraction of an optical signal and conversion of duty (pulse width), which are the basis for branching, inserting, and cross-connecting, without converting the optical signal on the communication path into an electric signal without changing the optical signal. An optical threshold element to which an optical data stream is input from an optical communication path and an optical frame pulse to be selectively superimposed on a desired bit of the optical data stream are input to the optical threshold element. An optical frame pulse generating means, an optical bistable element to which an output optical pulse from the optical threshold element is input, and a duty variable by superimposing on an input optical pulse from the optical threshold element. Optical clock generating means for inputting an optical clock to be converted to an optical bistable element.

[Industrial applications]

The present invention relates to an optical sampling memory device for selectively extracting only desired data from a data string on an optical communication path multiplexed on a time axis and performing duty conversion.

With the development of optical communication networks, various methods for exchanging signals by light have been studied in recent years. In the meantime, optical fiber was introduced to subscribers,
The realization of an optical subscriber transmission network for delivering high-speed and large-capacity optical signals, such as image signals, to subscribers or exchanging such information among subscribers will be one of the challenges for optical communication networks in the future. ing.

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

[Conventional technology]

In the conventionally proposed optical subscriber network, a transmission processing node is placed on the optical highway in order to gain access between the optical highway and the optical subscriber. An example of such a configuration of the transmission processing node is disclosed in, for example, "Fujimoto et al., IEICE Technical Report, CS87-90".

 The basic processing functions are the following three.

Branch processing for extracting desired data from an optical trunk line to an optical subscriber terminal.

Insertion processing for transmitting data from optical subscribers on empty time slots of the optical highway.

Cross-connect processing for exchanging time slots of data on the optical highway.

In the conventionally proposed example, all of the above processing is based on the processing of an electric signal. Specifically, for example, in the branching process, after converting the optical signal of the optical highway into an electrical signal in the photoelectric conversion unit of the transmission processing node,
The signal is branched at the level of the electric signal, converted into an optical signal for the subscriber in the electric / optical converter for the subscriber, and transmitted.
In addition, in the insertion process, the optical signal from the subscriber is converted into an electric signal by the photoelectric conversion unit, merged with the data of the optical highway, and then converted into an optical signal by the electric / optical conversion unit for the optical highway. They are sent to the Hikari Highway.

[Problems to be solved by the invention]

However, in order to handle ultra-high-speed optical signals on the optical highway and to perform branching, insertion, cross-connect, etc. on multi-channel optical subscriber lines by electrical processing, ultra-high-speed, multi-channel photoelectric conversion processing is required. Unit and an electric signal processing unit. Therefore, as the signals to be handled are increased in capacity, the processing units become bottlenecks in terms of processing speed, and the processing device becomes larger due to the increase in the number of channels. there were.

The present invention solves such a conventional drawback, and converts an optical signal on an optical communication path into an electric signal without converting the optical signal into an optical signal. It is an object of the present invention to provide an optical sampling memory device capable of selectively extracting a signal and converting a duty (pulse width).

[Means for solving the problem]

To achieve the above object, the optical sampling memory device of the present invention, as shown in FIG. 1, has an optical output without optical output when an optical data stream is input from an optical communication path and the optical input is below a threshold value. When the input exceeds the threshold value, an optical threshold element 2 that provides a large optical output and an optical frame pulse to be selectively superimposed on a desired bit of the optical data string are input to the optical threshold element 2. An optical frame pulse generating means 3, an optical bistable element 4 to which an optical output has a hysteresis characteristic with respect to an optical input and to which an output optical pulse from the optical threshold element 2 is inputted; An optical clock generating means 5 for inputting an optical clock for superposing the input optical pulse from the element 2 and converting the duty thereof to the optical bistable element 4 is provided.

[Action]

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, only the optical data of the bit on which the optical frame pulse is superimposed exceeds the threshold value, so that only the optical data is output from the optical threshold element 2. In this way, only the optical data of the desired bit can be extracted from the optical data stream.

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, when the input power of the optical clock pulse is between the rising threshold value and the falling threshold value of the optical bistable element 4 and the output optical pulse from the optical threshold element 2 is superimposed thereon, the optical bistable state is obtained. By exceeding the rising threshold value of the element 4, the input optical pulse from the optical threshold element 2 is converted into the duty of the optical clock pulse 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〕

 Embodiments will be described with reference to the drawings.

FIG. 2 shows an embodiment of an optical sampling memory device for branching optical data from an optical communication path. here,
In the optical communication path (optical highway) 1, for example, an optical data train of 1 to n pulses, that is, n-channel optical data is transmitted. 11 and 12 are first and second optical couplers,
An optical data stream is branched from the optical communication path 1 and extracted. An optical clock extraction circuit 13 is connected to an optical output terminal of the first optical coupler 11, and extracts an optical clock from a bit rate of an optical data string.

The optical output terminal of the optical clock extraction circuit 13 is connected to the optical frame pulse generator 3 and the optical clock generator 5. 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 frequency (for example, B / B) determined by the bit rate B and the multiplicity N of the optical data sequence
The optical clock N) is generated and output, and the power Pc of the optical clock pulse is smaller than the rising threshold Pon of the optical bistable element 4 described later and larger than the falling threshold Poff. The power Pb of the bias component between the clock pulses is smaller than the falling threshold value Poff, and the power Pc of the light obtained by superimposing the data light pulse on the clock pulse.
+ Pdata is larger than the rising threshold value Pon.

 That is, Poff <Pc <Pon Pc + Pdata> Pon and Pb <Poff.

In the optical frame pulse generator 3, a channel selection circuit
According to 3a, data of an arbitrary channel (for example, the i-th channel) is selected from the n-channel optical data train, and an optical frame pulse is output in accordance with the bit timing of the channel. The power Pf (height) of the optical frame pulse is smaller than the threshold value Pth of the optical threshold element 2 described later, and the power (height) Pf + Pdata of the optical pulse obtained by superimposing the optical data pulse on the optical frame pulse.
Is set to be larger than the threshold value Pth.
That is, Pf, Pdata <Pth, and Pf + Pdata> Pth.

The optical threshold terminal 2 is connected to the optical output terminal of the second optical coupler 12. As shown in FIG. 4 (A), the light threshold element 2 has no light output when the light input Pin is equal to or less than the threshold Pth, and generates a large light when the light input exceeds the threshold Pth. It has a characteristic (differential gain characteristic) from which an output Pout can be obtained.

The optical threshold element 2 includes an optical data pulse input from the second optical coupler 12 and an optical frame pulse generator 3.
4B, the optical frame pulse is superimposed on the data of the i-th channel alone to form a pulse having a power exceeding the threshold value Pth, as shown in FIG. 4B. Become. As a result, the optical threshold element 2 outputs only optical data obtained by superimposing an optical frame pulse on the bit (data) of the i-th channel as shown in FIG. 4C.

In this way, only desired optical data can be extracted from the optical data string. An example of an element having such characteristics and a physical phenomenon is, for example, a differential gain characteristic of a semiconductor laser amplifier.
et al., Jpn. J. Appl. Phys. 22 , L130 (1983) ".

Output light from the optical threshold element 2 is input to the optical bistable element 4. As shown in FIG. 5A, for example, the optical bistable element 4 has an optical output Pout with respect to an optical input Pin having a hysteresis characteristic. In the 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 combined as shown in FIG.
Are superimposed as shown in FIG. Then, the optical bistable element 4 is excited from the “L” state to the “H” state by the optical data. Then, even if the optical data is lost, it remains at “H” until the optical clock falls due to the hysteresis characteristic.

As a result, as shown in FIG. 5C, 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.
In this way, the duty of the light pulse is expanded.
In this way, the output duty of the optical data is arbitrarily converted according to the pulse width of the optical clock, and
Can be sent to 10.

Examples of devices and physical phenomena having such characteristics include, for example, hysteresis characteristics of optical bistable semiconductor lasers and optical memory operation using the same. For the characteristics, see, for example, Kuno et al., Autumn 1987. Equivalent, 29p-Z
H-7, 1987 "and" Suzuki et al., Spring 1984, IEICE, S17-13 ".

FIG. 3 shows an embodiment of a circuit for inserting an optical signal into the optical communication path 1. In the figure, reference numeral 21 denotes a timing adjustment circuit for outputting an optical frame pulse in accordance with the timing of an empty time slot on the optical communication path 1 into which an optical signal is inserted. Here, the optical frame pulse is input from the optical frame pulse generator 3 described above, the output of the optical frame pulse is waited according to the timing information from the optical communication path 1 side, and the timing is adjusted to an empty time slot on the optical communication path 1. To output an optical frame pulse. The optical frame pulse is superimposed on the optical input signal j input from the optical subscriber terminal 10, and
It is input to the light threshold element 2.

In this optical threshold element 2, contrary to the case of FIG.
The duty conversion of the optical signal acts in the direction of reducing the duty, and the data j is output with the same pulse width as the data on the optical communication path 1 after the duty is reduced. To join. At this time, since the time slot containing the data j has the data i,
This must be removed. Therefore, the optical data erasing circuit 23 is used. There are several ways to realize the optical erasing circuit 23, but they are not directly related to the present invention.
Here, the description is omitted.

In this manner, the optical signal on the optical communication path 1 can be dropped and inserted without converting the optical signal into an electric signal.

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 electric signal). The clock may be extracted at the level of the electric signal using the data receiving circuit. In order to recover the loss of the optical signal in this node, an optical amplifier may be inserted, or an optical repeater may be placed on the optical communication path 1.

〔The invention's effect〕

According to the optical sampling memory device of the present invention, a desired optical signal on the optical communication path can be selectively extracted as it is without converting it into an electric signal, and the insertion of the optical signal can be performed by the reverse operation. It can be carried out. Therefore,
In the transmission processing node, it is possible to realize an all-optical processing transmission processing node that can perform processing without converting an optical signal into an electric signal.

[Brief description of the drawings]

 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 an optical threshold element, and FIG. 5 is an operation of an optical bistable element. FIG. In the drawing, 1 ... optical communication path, 2 ... optical threshold element, 3 ... optical frame pulse generating means, 4 ... optical bistable element, 5 ... optical clock generating means.

Claims (1)

(57) [Claims] 1. An optical threshold element which receives an optical data stream from an optical communication path and has no optical output when the optical input is below a threshold, and provides a large optical output when the optical input exceeds the threshold. (2) 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) having an optical output having hysteresis characteristics and receiving an output optical pulse from the optical threshold element (2); and an input optical pulse from the optical threshold element (2). An optical clock generating means (5) for inputting an optical clock for converting the duty by superimposing the optical clock to the optical bistable element (4).