JP2537960B2 - Optical interface circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical interface circuit in which an optical receiver is provided with a loopback function so that a failure can be accurately determined and an unnecessary alarm can be avoided. .

<Prior Art> FIG. 4 is a block diagram of a conventional optical interface circuit. 1 is a downstream optical fiber, 2 is an optical / electrical conversion circuit, 3 is a receiving side electric circuit, 4 is an optical receiving section, 5 is an optical receiving section. An optical signal input disconnection alarm, 6 is a frame out-of-sync alarm, 7 is a transmission side electric circuit, 8 is an electric / optical conversion circuit, and 9 is an optical transmission unit.

To explain the conventional basic operation, an electric signal with a frame synchronization pattern from the transmission side electric circuit 7 is converted into an optical signal with a frame synchronization pattern by an electric / optical conversion circuit 8, and this optical signal is used. Is transmitted from the optical transmitter 9 to the downstream optical fiber 1. In the receiving unit 4, the downstream optical fiber 1
The optical signal transmitted through the optical / electrical conversion circuit 2 is converted into an electrical signal by the optical / electrical conversion circuit 2, and the receiving side electrical circuit 3 that receives this electrical signal establishes frame synchronization. When the optical signal input disconnection occurs, the optical signal input disconnection alarm 5
Output from the electric conversion circuit 2, and when the frame synchronization loss occurs, the reception side electrical circuit 3 outputs the frame synchronization loss alarm 6. When no optical signal is input, the out-of-frame alarm 6 is output as one form of out-of-frame synchronization. Eventually, the alarms 5 and 6 are simultaneously output when the optical signal is not input, and only the alarm 6 is output when the optical signal is input but only out of synchronization occurs.

By using the interface circuit, for example, the optical transmitter 9 is installed in one telephone station and the optical receiver 4 is installed in the other telephone station, whereby information transmission by optical signals is performed between the two stations.

<Problems to be Solved by the Invention> By the way, when a failure occurs in the optical receiver 4, the alarms 5 and 6 may be erroneously output. Therefore, even if there is an alarm output, the downstream optical fiber 1 and the optical transmitter 9
It is impossible to discriminate whether the opposite transmission unit including the unit has a fault and the original alarm output is present, or the optical receiving unit 4 has a fault and an erroneous alarm output is generated, that is, the fault section cannot be determined. There was a flaw.

For this reason, although the above-mentioned failure section determination requires labor and time for the loopback test, a reliable section determination cannot be performed, and a cut-and-try recovery work such as replacement of the optical interface circuit is required.

Further, when the downstream optical fiber 1 is not connected while the optical interface circuit is mounted on the device, there is a drawback that an alarm is generated although it is not a failure. To avoid this, useless work such as folding the inside of the station with an optical fiber was required.

In a station in which the optical receiving unit 4 is installed, inputting an optical signal generated in the station to the optical receiving unit 4 installed in the station is called “folding back”.

The present invention, in view of the above-mentioned conventional technology, can be detected by clearly determining whether the optical receiving unit itself has failed, or whether the opposite transmission side including the downstream optical fiber and the optical transmitting unit has failed, and the downstream optical fiber is An optical interface circuit capable of avoiding generation of an alarm even when not connected to the optical receiver 4.

<Means for Solving the Problems> According to the present invention for achieving the above object, an optical coupler is arranged between a downstream optical fiber and an optical / electrical conversion circuit in an optical receiving section of an optical interface circuit, and self-diagnosis electric / electrical It is characterized in that the optical signal from the optical conversion circuit can be injected by the control circuit.

<Example> FIG. 1 shows an example of the present invention. In this embodiment, the optical receiver 4'includes an optical coupler 10, a self-diagnosis electric / optical conversion circuit 1 in addition to the optical / electrical conversion circuit 2 and the reception side electric circuit 3.
1. It has a control circuit 12 and a signal input terminal 13. In FIG. 1, 1 is a downstream optical fiber, 7 is an electric circuit on the transmission side, 8 is an electric / optical conversion circuit, and 9 is an optical transmitter.

Next, the operation will be described. The transmitting side is similar to the conventional one. That is, the optical signal with the frame synchronization pattern sent via the downstream optical fiber 1 is sent to the optical / electrical conversion circuit 2 via the optical coupler 10 received by the optical receiving unit 4'and converted into electrical power. Based on the signal, the receiving side electric circuit 3 establishes frame synchronization and detects an alarm.

When alarms 5 and 6 occur at the same time, the idle signal with frame sync pattern is input through the signal input terminal 13 under the control of the control circuit 12, and the self-diagnosis electric / optical conversion circuit 11 adds the frame sync pattern. The idle optical signal of is output. This idle optical signal is injected into the optical / electrical conversion circuit 2 via the optical coupler 10. When this self-diagnosis is executed, (a) when the alarms 5 and 6 are cleared, it can be determined that a failure has occurred on the opposite transmission side including the downstream optical fiber 1 and the transmission section 9, and the light receiving section 4 ' It can be seen that it is normal, and (b) when the alarm continues, it can be determined that the optical / electrical conversion circuit 2 of the optical receiver 4'has a failure.

When only the alarm 6 is generated, it can be determined that the optical / electrical conversion circuit 2 is normal, but the receiving side electric circuit 3
It is impossible to discriminate whether or not there is a failure and the frame synchronization is lost, or there is a failure in the transmission side electric circuit 7 and a frame pattern transmission abnormality occurs. At this time, when the above-mentioned self-diagnosis is executed, (c) When the alarm is cleared,
Can be determined to be faulty, and (d) if the alarm continues, the receiving side electric circuit 3
It can be determined that is broken.

When the optical interface 1 is mounted and the downstream optical fiber 1 is not connected to the receiving unit 4 ', a self-diagnosis operation is similarly performed and an idle optical signal with a frame synchronization pattern is returned from the self-diagnosis electric / optical conversion circuit 11 as a return signal. Then, the light is injected into the optical / electrical conversion circuit 2 via the optical coupler 10. This can avoid the generation of unnecessary alarms.

Optical / electrical conversion circuit 2 and optical coupler of the embodiment shown in FIG.
The elements 10 and the self-diagnosis electric / optical conversion circuit 11 specifically use elements as shown in FIG. In other words, the APD (avalanche photodiode) or P
D (photodiode), a spherical lens or a waveguide type optical coupler as the optical coupler 10, an electric / optical conversion circuit for self-diagnosis
For 11, a simple LED (Light Emitting Diode) drive circuit can be adopted for downsizing and economy.

FIG. 3 shows a second embodiment of the present invention. The second embodiment differs from the first embodiment in that the transmission side electric circuit 7'of the optical transmitter 9'installed in the station of the optical receiver 4'is
The electric signal with the frame synchronization pattern is input to the self-diagnosis electric / optical conversion circuit 11 through the signal input terminal 13. In FIG. 3, 1'is an upstream optical fiber and 8'is an electrical / optical conversion circuit. The other structure is the same as that of the first embodiment.

According to the second embodiment, the failure location can be determined by performing the self-diagnosis as in the first embodiment.
Further, in this embodiment, since the electric signal with the frame synchronization pattern outputted from the electric circuit 7'on the transmitting side in the receiving side device itself is used, it is not necessary to separately prepare an idle signal generating circuit, and the certainty of judgment can be ensured. The circuit configuration is improved and the circuit configuration is facilitated.

<Effect of the Invention> As described above, according to the optical interface circuit of the present invention, when an alarm occurs, it is possible to determine whether the optical receiving unit itself has failed or the opposite transmission side including the optical fiber has failed. Moreover, if the optical receiver fails,
Further, it is possible to specify which one of the optical / electrical conversion circuit of the optical receiving section and the receiving side electric circuit has failed.

As a result, the failure section can be automatically determined, and the conventional optical fiber test is not required, so that there is an advantage that the test time can be shortened and the maintainability can be improved. In addition, when the optical fiber is not connected or the game is in a non-signal state when the optical interface circuit is mounted, unnecessary alarms can be avoided by using the self-diagnosis electric / optical conversion circuit as a loopback function, and loopback is performed by the optical fiber. There is an advantage that wasteful work of things can be omitted.

[Brief description of drawings]

FIG. 1 is a block diagram showing an optical interface circuit according to the first embodiment of the present invention, FIG. 2 is a concrete circuit diagram showing a main part of an optical receiving section of the first embodiment, and FIG. Second of the present invention
FIG. 4 is a block diagram showing an optical interface circuit according to this embodiment, and FIG. 4 is a block diagram showing a conventional optical interface circuit. In the drawings, 1 is a downstream optical fiber, 1'is an upstream optical fiber, 2 is an optical / electrical conversion circuit, 3 is a receiving side electrical circuit, 4 is a conventional optical receiving section, 4'is an optical receiving section of the present invention, 5 Is an optical signal input disconnection alarm terminal, 6 is an out-of-frame alarm, 7 is an electric circuit on the transmitting side, 7'is an electric circuit on the transmitting side of the own station, 8 is an electric / optical conversion circuit, 8'is electric / optical of the own station Conversion circuit, 9 is an optical transmission unit, 9'is an optical transmission unit of its own station, 10 is an optical coupler, 11 is a self-diagnosis electric / optical conversion circuit, 12 is a control circuit, and 13 is a signal input terminal.

Claims (1)

(57) [Claims] 1. An optical signal with a frame synchronization pattern is input from an optical transmission unit via an optical fiber, the optical signal is converted into an electrical signal with a frame synchronization pattern, and an optical signal is input when the optical signal is no longer input. An optical / electrical conversion circuit that issues a disconnection alarm and an electrical signal with a frame synchronization pattern sent from this optical / electrical conversion circuit are input to establish frame synchronization, and a frame out of sync alarm is generated when frame out of sync occurs. A self-diagnosis electrical signal that outputs a diagnostic optical signal with a frame synchronization pattern when a diagnostic electrical signal with a frame synchronization pattern is input to the receiving section of the optical interface circuit that has a receiving side electrical circuit / Optical conversion circuit and electrical / optical conversion for self-diagnosis when optical signal input disconnection alarm or frame out of sync alarm is issued A control circuit for activating the circuit to input a diagnostic electric signal with a frame synchronization pattern to the conversion circuit, and an optical signal sent from an optical transmitter through an optical fiber and a self-diagnosis electric / optical conversion circuit An optical interface circuit comprising: an optical coupler that receives an optical signal output from the optical coupler and sends the optical signal to the optical / electrical conversion circuit.