JPS6343010B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for controlling a redundant electrical-to-optical conversion circuit used in an optical transmission device, and more specifically, an optical output signal for switching the optical output signals of two electrical-to-optical conversion circuits. Regarding switching circuits.

Conventionally, optical output signal duplication methods used to improve the reliability of optical transmission equipment include a method in which the optical output signals of two electrical-to-optical conversion circuits are combined using an optical switch, and a method in which the optical output signals are combined using an optical switch. There is a method of combining the two using an optical multiplexer.

Among the redundant systems, those using optical switches constantly operate two electrical-to-optical conversion circuits to obtain optical output, so if one electrical-to-optical conversion circuit deteriorates, the other electrical-to-optical conversion circuit is activated. Since the circuit is considered to have undergone the same history as the deteriorated circuit, there was a drawback in that the guarantee of lifespan was not sufficient.

In addition, there are two types of optical multiplexers: one in which the optical outputs of two electrical-to-optical conversion circuits are constantly operated, and the other in which the two electrical conversion circuits are switched with a sufficiently long time constant.

The former has the same drawbacks as the optical switch mentioned above, and also has the drawback that the optical output level will be reduced by half if the electrical-to-optical conversion circuit fails and the optical output is cut off. There is.

The latter method is based on the optical-to-electrical conversion circuit on the receiving side.
The time constant for switching must be selected depending on the AGC time constant, so it is not necessarily universal.

In addition, the AGC time constant is set to a large value, from several hundred milliseconds to several seconds, in order to cope with changes over time, etc., and the time constant of the switching circuit is even larger, and the scale of the elements in the circuit used is also increasing. It had the disadvantage of being large.

An object of the present invention is to provide a device with a simple configuration in which a redundant electric-to-optical converter circuit can be switched to a spare electric-to-optical converter circuit without momentary interruption when the current electric-to-optical converter circuit deteriorates. An object of the present invention is to provide an optical output signal switching circuit.

In order to achieve the above object, the optical output signal switching circuit according to the present invention branches a clock signal into two in a switching circuit for switching a redundant electrical-to-optical conversion circuit that converts a data signal into an optical output signal. , a first branch circuit whose two branched clock signal output terminals are connected to the two electrical-to-optical conversion circuits, a second branch circuit that branches the data signal into two, and the electrical-to-optical conversion circuit. a first delay circuit that delays a first switching signal for using one of the two for a certain period of time that is sufficiently shorter than the time constant of the AGC circuit of the receiving side optical-to-electrical conversion circuit;
a second delay circuit that delays a second switching signal for using the other of the electro-optical conversion circuits by a constant time comparable to that of the first delay circuit; and a set input of the first switching signal. a first flip-flop circuit whose reset input is the second switching signal delayed by the second delay circuit; and a first flip-flop circuit whose reset input is the second switching signal delayed by the second delay circuit; A second flip-flop receives as a reset input the first switching signal delayed by the second flip-flop, and has a gate input as the first flip-flop output and one of the data signals branched by the second branch circuit. A first AND circuit connected to one of the electrical-to-optical conversion circuits, the second flip-flop output, and the other data signal branched by the second branch circuit are gate inputs, and the output thereof is and a second AND circuit connected to the other side of the electric-to-optical conversion circuit, and the AGC circuit of the optical-to-electrical conversion circuit on the receiving side has a short time delay determined by the first and second delay circuits. The circuit is constructed with a time constant that can sufficiently absorb changes in optical output.

According to the above configuration, when switching from one side of the redundant electrical to optical conversion circuit to the other, the electrical current of the other is switched like a continuous contact in a relay.
After the optical signal from the optical conversion circuit is output, the optical signal from one of the electrical-to-optical conversion circuits is cut off.
No momentary interruption of optical output occurs during switching. At the time of switching, the optical output is doubled, but this time is a short time range that does not affect the optical transmission system compared to the time constant of the AGC circuit of the optical-to-electrical conversion circuit on the receiving side, and it does not affect the characteristics of the optical transmission system. Without detracting from this, the object of the invention is fully achieved.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of an optical output signal switching circuit according to the present invention.

A data signal serving as an input electrical signal for electrical-to-optical conversion is branched by a second branch circuit 11 . Further, the clock signal is sent to the first branch circuit 12.
The signal is branched by , and input to electric-to-optical conversion circuits 2 and 3 .

A second switch is connected to the switching signal terminal of the optical output signal switching circuit 1.
When the first switching signal as shown in the figure is applied,
The first flip-flop circuit 5 is set, and at the same time the switching signal is transmitted by the first delay circuit 8 to
The second flip-flop circuit 7 is reset with a delay of time τ. The outputs Q 1 _and Q 2 of the first and second flip-flop circuits 5 and 7 operate before and after the time _τ , and the outputs Q 1 and Q 2 of the first and second flip-flop circuits 5 and 7 operate back and forth by a time τ,
The signal is input to first and second AND circuits 9 and 10 together with the data signal branched into two by signals 1 and 12, and the data signal is controlled. The outputs of the first and second logic circuits 9 and 10 maintain the time relationship shown in FIG. 2 and are input to the electrical-to-optical conversion circuits 2 and 3 as data signals of the optical output signal switching circuit.

The optical output signals subjected to electrical-to-optical conversion in the switching circuits 2 and 3 are duplicated in a multiplexer 4.

Next, when a second switching signal as shown in FIG. 2 is applied to the switching signal terminal of the optical output signal switching circuit 1, the second switching signal is The optical output of the first electric-to-optical conversion circuit 2 is turned on, and after a time τ, the optical output of the first electric-to-optical conversion circuit 1 is turned off.

Therefore, at the time of switching, the duplicated optical output signals of the optical multiplexer overlap for a time τ as shown in FIG. 2, so that no data is lost due to switching.

In other words, the optical output signal can be switched without momentary interruption.

In addition, when one electrical-optical conversion circuit is operating, the other electrical-optical conversion circuit is in a dormant state, so the lifespan of the optical device used as a light source is not impaired, and the duplex system is Able to achieve purpose.

Note that the time τ during which the optical output level increases during switching is sufficiently shorter than the time constant of the AGC circuit of the optical-to-electrical conversion circuit on the receiving side, so it does not impair the characteristics of the optical transmission system.

As described above in detail, according to the present invention,
When the input clock signals of two electrical-to-optical conversion circuits are connected in a duplex optical repeater system,
Furthermore, by switching the data signals with a time difference between the data signals, it is possible to perform the switching operation without momentarily interrupting the optical output signal of the electro-optical conversion circuit.

Since the switching circuit according to the present invention always puts one of the electro-optic conversion circuits in a dormant state, the life of the electro-optic conversion element in the standby state is not impaired.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the optical output signal switching circuit according to the present invention, and FIG. 2 is a time chart for explaining the operation of the embodiment of FIG. DESCRIPTION OF SYMBOLS 1... Optical output signal switching circuit, 2, 3... Electrical-optical conversion circuit, 4... Optical multiplexer, 5... First flip-flop circuit, 6... Second delay circuit, 7... Second flip-flop circuit, 8... First delay circuit, 9... First AND circuit, 10... Second AND circuit, 11
...Second branch circuit, 12...First branch circuit.

Claims (1)

[Claims] 1. In a switching circuit for switching a redundant electrical-to-optical conversion circuit that converts a data signal into an optical output signal, the clock signal is branched into two, and the two branched clock signal output terminals are connected to the two electrical output terminals, respectively. -The first connected to the optical conversion circuit
a branch circuit, a second branch circuit that branches the data signal into two, and a first switching signal for using one of the electric-to-optical conversion circuits when the AGC circuit of the optical-to-electrical conversion circuit on the receiving side a first delay circuit that delays a certain period of time that is sufficiently short compared to the constant;
a second delay circuit that delays a second switching signal for using the other of the optical conversion circuits by a constant time comparable to that of the first delay circuit; a first flip-flop circuit whose reset input is a second switching signal delayed by a second delay circuit; and a first flip-flop circuit whose reset input is a second switching signal delayed by the first delay circuit; A second flip-flop receives the first switching signal obtained as a reset input, and one data signal branched from the first flip-flop output and the second branch circuit serves as a gate input, and its output is connected to the electrical circuit. A first AND circuit connected to one side of the optical conversion circuit, the second flip-flop output and the other data signal branched by the second branch circuit are gate inputs, and the output thereof is connected to the electrical circuit. - a second AND circuit connected to the other side of the optical conversion circuit;
An optical output signal switching circuit comprising a circuit having a time constant that can sufficiently absorb short-term optical output changes determined by the second delay circuit.