JPS58123247A - Circuit monitoring device of optical transmission system - Google Patents

Abstract

PURPOSE:To detect the breaking and recovery of a circuit with extremely high accuracy by initializing a counter when a light signal is present. CONSTITUTION:The light signal SO is converted into an electric signal S1, which is applied to an inverter 6. Consequently, the output of the inverter 6 rises to ''1'' when the light signal is received and falls to ''0'' when not, and every time the signal ''1'' is inputted, the counter 7 is initialized. On the other hand, while the output signal S7 of the counter 7 is ''0'', a clock from a clock pulse generator 8 is applied to the input terminal K of the counter 7. Therefore, when the light signal s present, the counter 7 is reset immediately, but when not, it outputs the signal ''1'' continuously. For this purpose, the counted value of the counter 7 is preset properly to detect the breaking of a circuit accurately in the shortest time.

Description

[Detailed Description of the Invention] The present invention relates to an optical transmission system that transmits information using light, and in particular, a line monitoring device that monitors line disconnections accompanied by interruptions in optical signals (hereinafter simply referred to as line disconnections). Regarding.

Conventionally, a device of this type is shown in FIG. In the figure, (1) is a signal converter that converts an optical signal into an electrical signal, (2) is a signal converter that receives the output of (1),
An operational amplifier (hereinafter referred to as an operational amplifier) that generates a voltage of 0 (V) when a logic level 111 is input, and a voltage of 0 (V) when a logic level OI is input.
, <a) is a resistor, (4) is a capacitor, and (5) is a capacitor (4) that detects the voltage across its terminals and detects that this voltage has dropped below the set value, and then sets the logic level '11. signal(
(The logic levels are omitted below)] are shown below.

The operation of this line monitoring device will be explained below with reference to the time chart shown in FIG.

First, this device is applied to a system in which the code is configured such that at least one bit of optical signal is transmitted within one word or one frame.21. If a synchronization bit always exists at the beginning of one word, the time interval between occurrences of this synchronization bit is equal to two cycles in a code in which a 1-bit optical signal exists at the beginning and end of one word. take the time
When an optical signal cannot be received even after each period has elapsed, it is determined that the line is disconnected.

Here, the symbols SO to s5 attached to the signal lines in FIG. 1 correspond to 80 to B5 in FIG. 2, and the optical signals SO are applied to the signal converter (1). Then, a signal 81 is applied to the operational amplifier (2) so that the "presence" of light becomes the level %gl, and the "absence" of the light becomes the level 11'. The operational amplifier (2) has a level Jl of 0 [v] and a level %O.
A signal 82 which becomes m (v) with respect to y is output, and this signal 82 is applied to an integrating circuit consisting of a resistor (8) and a capacitor (4). , Therefore, the terminal voltage of the capacitor (4) increases when there is an optical signal, as shown in FIG. ].

By the way, if the line is normal, even if the time interval is the longest after receiving the optical signal at time t,
Since the code configuration is such that the optical signal is received at t8, the terminal voltage s3 of the capacitor (4) drops to E, It will rise.

However, if the optical signal is still not received even at time ts, this voltage continues to drop further.

In the level detection circuit (5), a voltage m, (v) lower than the voltage IcX, [v] is set as a threshold value, and the terminal voltage 86 of the capacitor (4) becomes the threshold value 18 (v). Time t.

A signal B5 whose level becomes '1' is generated.

That is, when an optical signal cannot be received within a scheduled time period □, this is determined to be a disconnection of the line and the signal B3 is generated.

On the other hand, when the line is restored and an optical signal is received, the terminal voltage of the capacitor (4) also increases, and this voltage becomes Z,
(V) at time t4, the output level of the level detection circuit also returns to 10'.

Since such conventional line monitoring devices detect the charging/discharging voltage of the capacitor, the time at which line disconnection is detected differs depending on the code structure, and the time at which line disconnection is detected differs depending on the code structure. The drawback was that it could not be detected accurately.

This invention was made in order to eliminate the above-mentioned drawbacks, and is a line monitoring device that can accurately detect line disconnection when a scheduled time has elapsed, and can also immediately detect line restoration. The purpose is to provide.

In order to achieve the above object, the line monitoring device of the present invention includes a signal converter that converts an optical signal into an electrical signal, a clock pulse generator, and counts and calculates the pulses of the clock pulse generator. and a counter which generates a signal when the numerical value increases to a set value and which is reset or preset by the output of the signal converter, and the counter is activated every time an optical signal is received. Reset or preset, count the pulses of the clock pulse generator from the time when the optical signal disappears, and generate an output to this counter when the optical signal cannot be received within the scheduled time, thereby preventing line disconnection. Configure it to judge.

- Hereinafter, the present invention will be explained based on one embodiment with reference to the accompanying drawings.

Figure 3 is a block diagram showing the configuration of the line monitoring device according to the present invention. , of the optical signal
Something that outputs a signal that becomes 111 for "No",
(6) is an inverter that inverts the output of the signal converter (1), (γ) is a counter usually called an N-ary counter, which is placed in a reset state when the output of the inverter (6) is 111; While the output of the inverter (6) is 1 ON, pulses are counted and when the count value reaches N, %1
1 signal, (8) is a clock pulse generator, (9) is an inverter that inverts the output of the counter (η), and (7) is a two-man-operated AND gate, with an inverter ( 9), and clock pulses are added to the other input terminal, respectively, and when the AND condition is satisfied, only the clock pulse of the clock pulse generator (8) is added to the counter (7).

The operation of the line monitoring device according to the present invention constructed as described above will be described below with reference to the time chart in FIG. Note that the symbols attached to the signal lines in FIG. 6 correspond to those in FIG.
Figure CO represents the contents of the counter (7).

First, the optical signal SO shown in FIG.
), this optical signal is converted into an electrical signal, and the signal S1 shown in FIG.
In addition to. The inverter (6) inverts this signal S1 and converts it to 11 when receiving the optical signal as shown in FIG. 686.
', and a signal S6 which becomes 10' when not receiving is applied to the reset terminal R of the counter (7). As a result, the counter (7) receives a signal 11' corresponding to the optical signal σ present. initial state KV-1 = 7) anbo.

Next, when the output signal S7 of the counter (7) becomes %Ol, the output of the inverter (9) becomes 11', and the clock pulse S8 of the clock pulse generator (8) passes through the AND gate to the counter ( γ) is added to the input terminal K of n.

In this way, the counter (7) counts the clock pulse signal S8 and increases sequentially for the time corresponding to the "absence" of the optical signal, but is immediately reset to the initial state based on the subsequent optical signal sent in. This state is shown in FIG. 4 CO.

By the way, even if the line is normal and the time interval is the longest since receiving the optical signal at time t□, time t
Even though the code is configured to receive the optical signal again at time t2, if optical signal 16 cannot be received at time t2, the count value of the counter (7) gradually increases and the value At time t when becomes N, a signal of 11' is output. Note that when the counter (γ) outputs a signal of 11', the inverter (9) closes the AND gate;
No more than n clock pulses will be applied to the counter (γ). Therefore, the counter (γ) continues to output a signal of '1' unless an optical signal is sent again.

On the other hand, when the line is restored and an optical signal is received at time t4, the counter (7) is reset at the same time, and its output signal S7 also returns to -OI.

In this case, the oscillation frequency of the clock pulse generator (8) should be determined so that the count value of the counter (7) becomes exactly N at the time when the maximum interval time for receiving (or transmitting) optical signals has elapsed. For example, line disconnection can be detected accurately in the shortest possible time. Further, when the line is restored, the output of the counter (7) returns to O1 at the same time as the optical signal is received, so that the time when the line is restored can be accurately detected.

Although the preferred embodiment of the present invention has been described above, it is not limited to this embodiment. For example, if an up-down counter that can be preset by 1 is used instead of an N-ary counter, line disconnection can be detected. You can arbitrarily select the time and the time to detect line restoration.

As is clear from these descriptions, by using the line monitoring device of the present invention, it is possible to detect line disconnection and line restoration time extremely accurately, and the main part thereof is composed of a counter and a clock pulse generator. Because of this, it has the effect of significantly reducing its cost compared to conventional ones.

Further, this line monitoring device is not limited to simply monitoring an optical transmission system, but can be applied to any other transmission line as long as the presence or absence of an information medium can be made to correspond to logical %11 or 0.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a line monitoring device of a conventional optical transmission system, FIG. 2 is a time chart for explaining the operation of this line monitoring device, and FIG. 6 is a block diagram of the optical transmission system according to the present invention. FIG. 4 is a block diagram showing the configuration of an embodiment of the line monitoring device, and a time chart for explaining the operation of the embodiment. (1): Converter to signal (2): Operational amplifier (8):
Resistor (4): Capacitor (5) Two-level detection circuit (a) s (9): Inverter (7): Counter (8): Clock pulse generator (to): AN
D gate

Claims (1)

[Claims] An optical signal of at least 1 bit is transmitted within a certain period n
In a line monitoring device for an optical transmission system, which automatically determines that the line is disconnected if an optical signal is not received within a scheduled time, Ri uses a tsuta pulse generator and an optical signal to convert it into an electrical signal. Counts the pulses of the signal converter to be converted and the digital pulse generator, generates K11 when the counted value rises to a set value, and resets or resets by the output of the signal converter. and a preset counter, which resets or puts the counter into a preset state upon receiving an optical signal, counts the pulses of the pulse generator from the time when the optical signal disappears, and counts the pulses of the pulse generator within nine hours. 1. An @ line monitoring device for an optical transmission system, characterized in that it is configured to determine that a line is disconnected by generating an output on this blank line when it cannot receive an optical signal.