JPH04371031A - Optical repeater - Google Patents

Abstract

PURPOSE:To obtain an optical repeater with the loop back function of stable characteristic where a reception signal is not leaked to a transmission signal. CONSTITUTION:The reception optical signal in an incoming transmission line is inputted to a reception circuit 11 and is converted to an electric signal to reproduce the waveform, and it is inputted to a next E/O transducer 12 and is converted back to an optical signal. The reception signal is inputted to an optical directional coupler 13 as the optical signal and is branched into two and is switched to the loop back side by an optical switch 14 and is sent to an outgoing transmission line. The reception optical signal on the down transmission line is inputted to a reception circuit 21 and is sent to the up transmission line through the same process. A control circuit 30 sends a switching signal to optical switches 14 and 24 by control signals from reception circuits 11 and 12 to switch them to loop back circuits.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical repeater, and more particularly to a loopback function of an optical submarine repeater.

0002

[Prior Art] In an optical cable system in which multiple optical repeaters are connected in cascade, when a failure occurs in the cable section,
Alternatively, in some cases, such as testing during construction, a circuit loopback test may be performed at a repeater designated by a control signal from a terminal station. This turning back is also called a loopback, and the optical repeater in this case is a bidirectional repeater that has repeating circuits in each of the upstream and downstream directions of the line. The loopback function is, for example, a function that switches the received signal from the upstream (or downstream) direction within the repeater using a control signal from the terminal station and loops it back to the transmitting side in the same upstream (or downstream) direction. means.

[0003] Conventionally, there is an optical repeater having this type of loopback function as shown in FIG. FIG. 3 is a block diagram showing the circuit configuration of a conventional example. The received optical signal from the upstream transmission path is input to the receiving circuit 11, where the optical signal is first converted into an electrical signal, then equivalently amplified with the electrical signal, the waveform is regenerated by the extracted clock, and the main signal is sent to the branching circuit. Sent on 15th. On the other hand, the control signal superimposed on the received signal is extracted from the signal sequence converted into an electrical signal and sent to the supervisory controller 30 as a control signal.

The splitter 15 branches the input main signal into two, sends the first output to the switch 16, and sends the second output to the switch 2. The switch 16 inputs the first output of the splitter 15 and the second output of the splitter 2, which branches the main signal from the downlink transmission line, selects one of them, and outputs the output as electrical/optical (hereinafter referred to as E). /O) to the converter 17. E
The /O converter 17 converts the electrical signal output from the switch 2 back into an optical signal and sends it out to the downstream transmission line.

[0005] The received optical signal from the downlink transmission path is transmitted to the receiving circuit 2.
E/O following the same conversion process as explained above in 1.
The signal is sent from the converter 27 to the upstream transmission path.

On the other hand, the supervisory controller 30 that receives the control signal output from the receiving circuit 11 performs various supervisory control functions using this control signal, but if there is a switching signal instructing loopback among these, , this switching signal is sent to switch 1
6 and switch 26. Switch 16 and switch 26 are normally connected to turnout 15 and turnout 25, respectively.
However, upon arrival of this switching signal, the second output is selected, and loopbacks are established for the uplink and downlink transmission paths, respectively. Further, the same operation is performed for the control signal from the receiving circuit 21. Note that this loopback is canceled by restoring the control signal to a normal signal.

[0007]

[Problems to be Solved by the Invention] In the conventional example described above, since the switches 16 and 26 are analog switches that switch electrical signals, crosstalk between the contacts causes the signal transmitted through the repeater to be distorted under normal conditions. There is a phenomenon in which the return signal during loopback causes crosstalk. This is due to crosstalk of the received signal from the other party to the transmitted signal, which poses a problem of adverse effects such as jitter on the transmitted signal.

[0008]

[Means for Solving the Problems] The optical repeater of the present invention has the function of transmitting a received optical signal in one direction during normal times and in the opposite direction during loopback.
After converting an electrical signal into an optical signal, the optical signal is branched into two optical signals, and the branched optical signals are input to the optical switch that selects one direction and the opposite direction.

For example, a first receiving circuit receives an optical signal from an upstream transmission line, converts the optical signal into an electrical signal, and outputs a main signal whose waveform is reproduced and a control signal extracted from the electrical signal; a first converter that converts the main signal output from the first receiving circuit into an optical signal again; and a first converter that branches the optical signal output from the first converter into a first output and a second output. a second receiving circuit that receives an optical signal from a downstream transmission line, converts the optical signal into an electrical signal, and outputs a main signal whose waveform is regenerated and a control signal extracted from the electrical signal. a second converter for converting the main signal output from the second receiving circuit back into an optical signal; and converting the optical signal output from the second converter into a first output and a second output. A second optical branching device for branching, a first output of the first optical branching device, and a second output of the second optical branching device are input, and one of them is selected and sent to the downlink transmission path. a first optical switch that
a second optical switch that inputs the first output of the second optical branching device and the second output of the first optical branching device, selects one of them, and sends the selected one to the upstream transmission path; Control signals output from the first and second receiving circuits are input to the first and second optical switches, and normally the first outputs of the first and second optical splitters are selected. and a control circuit that outputs a switching signal for selecting the second output of the first and second optical splitters during loopback.

0010

Embodiments Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the circuit configuration of the first embodiment. A received optical signal from the upstream transmission path is input to the receiving circuit 11 as in the conventional example, converted into an electrical signal, regenerated in waveform, and output. The output electrical signal is input to the E/O converter 12 and converted back into an optical signal. Next, this optical signal enters the optical splitter 13 and is split into two, with the output of one branch being output to the optical switch 14 and the output of the other branch being output for loopback to the optical switch 24 in the transmission direction of the upstream transmission path. Ru. A branch output for loopback is added to the optical switch 14 from an optical branching device 23 on the downstream transmission line side. This optical switch 14 selects the output from the optical branching device 13 in normal times according to a switching signal from the control circuit 30, and selects the loopback output of the optical branching device 23 during loopback, and sends that output down the transmission path. is being sent to.

On the other hand, the received optical signal from the downlink transmission path enters the receiving circuit 21, and then passes through the E/O converter 22 and the optical splitter 23.
The optical switch 2 follows the same conversion process as explained above.
4 to the upstream transmission path. Here, the optical splitter 13,
Reference numeral 23 uses an optical directional coupler or the like, and optical switches 14 and 24 use mechanical optical switches or the like with high isolation between switching circuits.

FIG. 2 is a block diagram showing the circuit configuration of the second embodiment. The difference from the first embodiment lies in the optical switch. That is, the optical switch 14 of the first embodiment is replaced with an optical switch section composed of optical interrupters 18 and 19 and an optical coupler 20 in the second embodiment. The same applies to the optical switch 24 of the first embodiment.

In FIG. 2, according to the switching signal from the control circuit 31, the optical interrupters 18 and 28 are in a normal state, and the optical interrupters 19 and 29 are in a cut-off state, but when looping back, the optical interrupter 18 is in a state of passing. , 28 is cut off, optical interrupter 19, 2
9 is in a passing state. The optical couplers 20 and 32 couple the optical signals from the optical breakers 18 and 28 and the optical breakers 19 and 29, respectively, and send the signals down to the up transmission line. This second embodiment is characterized in that since the optical circuit breakers constituting the switching circuits are independent, sufficiently high isolation can be achieved between the switching circuits, that is, between the optical circuit breakers.

In the configurations of the first and second embodiments described above, the received optical signals from the uplink and downlink transmission paths are normally relayed to the downlink and uplink transmission paths, respectively. Alternatively, when the control signal from the downlink transmission path changes from a normal signal to a loopback signal, the optical switch section is switched by the switching signal from the control circuits 30 and 31, and the received optical signals from the uplink and downlink transmission paths are respectively It is looped back to the upstream and downstream transmission paths. Note that this loopback is canceled by restoring the control signal to a normal signal.

[0015]

[Effects of the Invention] As explained above, the optical repeater of the present invention performs loopback switching using an optical switch with high isolation between switching circuits.
This has the effect of providing an optical repeater with a loopback function that has stable characteristics that prevent crosstalk between the received signal and the transmitted signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the circuit configuration of a first embodiment.

FIG. 2 is a block diagram showing a circuit configuration of a second embodiment.

FIG. 3 is a block diagram showing a circuit configuration of a conventional example.

[Explanation of symbols]

11, 21 Receiving circuit 12, 22, 17, 27 E/O converter 13, 2
3 Optical splitters 14, 24 Optical switches 30, 31 Controllers 15, 25 Branchers 16, 26 Switches 18, 19, 28, 29 Optical breakers 20, 32
optical coupler

Claims (4)

[Claims] Claim 1: In an optical repeater that has the function of transmitting a received optical signal in one direction during normal operation and transmitting it in the opposite direction during loopback, the optical repeater converts an electrical signal into an optical signal and then converts the optical signal into two optical signals. An optical repeater characterized by branching into signals and inputting the branched optical signals to an optical switch that selects the one direction and the reverse direction. 2. An optical receiving circuit that receives an optical signal, converts it into an electrical signal, and regenerates a waveform; a converter that converts the electrical signal outputted from the optical receiving circuit into an optical signal; and an optical signal outputted from the converter. a splitter that branches an optical signal into a first and a second optical signal; and a first light blocking means that passes the first optical signal output from the splitter in a first state and blocks it in a second state. and a second light blocking means that blocks the second optical signal in the first state and allows it to pass in the second state. 3. A first receiving circuit that receives an optical signal from an upstream transmission path, converts the optical signal into an electrical signal, and outputs a main signal whose waveform is regenerated and a control signal extracted from the electrical signal; a first converter that converts the main signal output from the first receiving circuit into an optical signal again; and a first converter that branches the optical signal output from the first converter into a first output and a second output. 1
a second receiving circuit that receives an optical signal from a downstream transmission line, converts the optical signal into an electrical signal, and outputs a main signal whose waveform is regenerated and a control signal extracted from the electrical signal; , a second converter for converting the main signal output from the second receiving circuit back into an optical signal; and branching the optical signal output from the second converter into a first output and a second output. Second to do
a first optical splitter, which inputs the first output of the first optical splitter and the second output of the second splitter, selects one of them, and sends it to the downlink transmission path. an optical switch; a second light that inputs a first output of the second optical splitter and a second output of the first optical splitter, selects one of them, and sends the selected one to an upstream transmission path; A control signal output from the switch and the first and second receiving circuits is inputted to the first and second optical switches. and a control circuit that outputs a switching signal that selects the output of the first and second outputs of the first and second optical splitters during loopback. 4. The first optical switch has first and second optical breakers and a first coupler, and the second optical switch has third and fourth optical switches and a second coupler. an optical coupler, a first output of the first optical splitter is applied to the first optical interrupter, a second output is applied to the fourth optical interrupter, and the second output of the optical splitter is applied to the fourth optical interrupter; A first output of the splitter is applied to the third optical interrupter, a second output is applied to the second optical interrupter, and the first and third optical interrupters are connected to the optical signal by the control circuit. The second and fourth optical interrupters are controlled by the control circuit to allow the optical signal to pass during the normal time and to pass during the loop back, The optical coupler is the first optical coupler.
and the second optical coupler sends the output of the second optical isolator to the downlink transmission line, and the second optical coupler sends the output of the third and fourth optical breakers to the uplink transmission line. The optical repeater according to claim 3.