JPH0482335A - Fail safe type optical transmission reception system and its optical circuit - Google Patents

Abstract

PURPOSE:To keep the communication between a station and a subscriber by using an optical switch provided on a station side and a subscriber side when a fault of an optical fiber transmission line is detected by an optical test circuit so as to change over the optical fiber transmission line from the main system into the standby system. CONSTITUTION:A optical output of an electric/optic conversion circuit 1a of a master system of a station side is monitored by an optical monitor circuit 3a of the master system to monitor a fault state as to whether its optical output is reduced or zero. When the optical monitor circuit 3a detects a fault, an electric/optic conversion circuit 1b of a standby system is activated in place of the electric/optic conversion circuit 1a of the master system and the optical switch 4 is changed over. Thus, the optical output of the electric/optic conversion circuit 1b of the standby system is fed to the subscriber side through an optical multiplexer/demultiplexer circuit 2b, the optical switch 4, an optical multiplexer/demultiplexer circuit 5b, and an optical fiber transmission line 6a. A switching control circuit is easily realized by employing a conventional electric comparator circuit.

Description

[Detailed Description of the Invention] Field of Industrial Use] The present invention provides a circuit for monitoring an outgoing optical signal in a transmission system in which a station and a subscriber are connected by an optical fiber transmission line, and a circuit for testing and monitoring the transmission line. circuit.

The present invention relates to an optical transmission/reception system including an optical switch for switching optical paths in the event of a failure, and its optical circuit.

``Prior Art'' Optical subscriber transmission systems that connect a station and a subscriber with a single optical fiber and perform bidirectional transmission are being researched around the world.

In realizing this system, it is important to ensure the reliability of the optical transmitter/receiver and the optical fiber transmission line.

As a method to ensure this reliability, the configuration shown in Figure 3 is being considered (Japanese Patent Laid-Open No. 62-273428).
. In the figure, 32 is an electrical-to-optical converter, 33 is an optical signal, 34 is an optical demultiplexer, 35 is an optical test circuit, 36 is an optical fiber transmission line, 37 is an optical demultiplexer, and 38 is an optical-to-electrical converter. vessel, 3
9 is a terminal device, 44 is an optical-electrical converter, 45 is a monitor device, 46 is an optical branch circuit, 47 is an optical pulse tester, and 48 is an optical junction path.

Optical signal sent from the electrical-to-optical converter 32 of the station <arrow 33
is monitored by the monitor device 45 via the optical branch circuit 46. In addition, to search for a fault point in the optical fiber transmission line 36, a test light pulse is sent from the optical pulse tester 47 to the optical fiber transmission line 36 via the optical junction path 48 of the reflection mirror, and the test light pulse generated by this test light pulse is The backscattered light in the optical fiber transmission line 36 is transmitted through the optical coupling shallow concave FI? 14
The optical pulse test circuit 47 receives the signal through the optical pulse test circuit 8 and performs the test.

! Problems to be Solved by the Invention] With the configuration shown in FIG. 3, it is possible to monitor the optical signal sent out and the state of the optical fiber transmission line based on the local f law. but,
There is no provision for switching to a spare device to maintain communication between the station and the subscriber in the event of a failure.

The purpose of the present invention is to solve the problems of the prior art described above,
The object of the present invention is to provide a fail-safe optical transmission/reception system including not only a circuit for testing and monitoring an optical fiber transmission line but also an optical switch for switching the optical path in the event of a failure, and an optical circuit thereof.

[Means for Solving the Problems] The fail-safe optical transmission/reception system of the present invention connects a station and a subscriber with a main system and a protection optical fiber transmission line. As a system circuit, the wavelengths λ1 and λ
An optical transmitter/receiver circuit that sends and receives optical signals of 2, an optical multiplexer/demultiplexer circuit that multiplexes and demultiplexes the optical signals, and a wavelength λ to the optical fiber transmission line.
An optical test circuit is installed to test and monitor failures in the optical fiber transmission line by sending out optical pulse signals (3), and an optical switch is installed to switch between the main and backup circuits. An optical switch that switches the optical fiber transmission line of the system, an optical multiplexing/demultiplexing circuit, and an optical transmitting/receiving circuit that sends and receives optical signals of wavelengths λ2 and λ1 are installed: When a fault in the optical fiber transmission line is detected by the above optical test circuit. teeth,
The optical switches provided on the station side and the subscriber side are used to switch the optical fiber transmission line from the main system to the backup system.

In this case, it is preferable that the switching of the optical fiber transmission line from the main system to the standby system is performed by feedback control of the output of the optical test circuit to the optical switch on the station side.

In addition, an optical monitor circuit is further provided on the station side to monitor the transmitted optical signal in the optical path of the main system and the backup system, and when the optical monitor circuit detects an abnormality in the optical output of the optical transmitter/receiver circuit of the main system, The optical transmitter/receiver circuit can be switched to a standby system, and the optical switch can also be switched to a standby system. In this case as well, the switching of the optical transmitter/receiver circuit and optical switch to the standby system at the central office is achieved by feedback control of the output of the optical monitor circuit to the optical switch at the central office and the control circuit of the optical transmitter/receiver circuit at the central office. It is preferable to do so.

The fail-safe optical circuit including the optical circuits on the station side and the subscriber side can be constructed of optical waveguides.

[Two functions] The gist of the present invention is to additionally provide a backup optical transmission circuit, an optical multiplexing/demultiplexing circuit, an optical test circuit, and an optical switch on the central office side, and an optical switch on the subscriber side, and to provide a backup optical fiber transmission line. is installed between the station and the subscriber, and when a failure occurs in the transmission line, an optical switch installed at the station and subscriber side switches to a backup optical fiber transmission line.

Furthermore, if an optical monitor circuit is provided in the main system and the backup system on the station side, and when an optical output abnormality in the main system is detected by the optical monitor circuit, the optical transmitter/receiver circuit and the optical switch are switched to the backup system. It is.

Therefore, in the event of a failure, it is possible to switch to a spare device and maintain communication between the station and the subscriber.

In these forms, the output of the optical fiber transmission line or the optical transceiver circuit is controlled by feeding back the output of the optical test circuit to the optical switch at the station side, or by feeding back the output of the optical monitor circuit to the optical switch and the control circuit. Switching from the main system to the standby system can be performed automatically.

"Example] Hereinafter, the present invention will be explained based on illustrated embodiments.

Figure 1 shows the system configuration of a subscriber transmission system with an optical test circuit.This system allows optical signals of different wavelengths λ1 and λ2 to be transmitted within one optical fiber transmission R (6a or 6b).
This is an example of a configuration in which data is transmitted in both directions as shown by arrows 17 and 18, and the a and b added after the numbers in the figure indicate whether the data is for the main system or for the backup system.

From the station side shown on the left side of FIG. 1, an optical signal of wavelength λ1 is sent out from the electrical-to-optical conversion circuit 1a of the main optical transceiver circuit. This optical signal is sent to the optical multiplexing/demultiplexing circuit 2a, the optical switch 4.
After passing through the optical multiplexing/demultiplexing circuit 5a, the main optical fiber transmission line 6
a, and is sent to the subscriber side as shown by arrow 17.

On the subscriber side, this optical signal is received by an optical-to-electrical conversion circuit 9 of an optical transmitting/receiving circuit via an optical switch 7 and an optical multiplexing/demultiplexing circuit 8.

On the other hand, from the subscriber side, an optical signal with wavelength λ2 is transmitted from the electro-optical conversion circuit 10 of the optical transmitting/receiving circuit to the optical multiplexing/demultiplexing circuit 8. After passing through the optical switch 7, the signal is sent to the office side as indicated by an arrow 18 through the main optical fiber transmission line 6a. Then, an optical multiplexing/demultiplexing circuit 5a, an optical switch 4. The signal is received by the optical-to-electrical conversion circuit 11a via the optical multiplexing/demultiplexing circuit 2a.

In this configuration, the main electrical-to-optical conversion circuit 1a on the station side
The light output of the main system is monitored by the main optical monitor circuit 3a, and abnormal conditions such as whether the light output has decreased or become zero are monitored. When an abnormality is detected by the optical monitor circuit 3a, the backup electric-optical converter circuit 1b operates instead of the main electric-optical converter circuit 1a, and the optical switch 4 is also switched. The optical output of the backup electrical conversion circuit 1b or the optical multiplexing/demultiplexing circuit 2
b. Optical switch 4. Optical multiplexing wave cycle #I5. It is sent to the subscriber side through the optical fiber transmission line 6a.

Note that the switching control circuit for switching to the standby system according to the output signal of the optical monitor circuit 3a, that is, switching from the electric-to-optical conversion circuit 1a to 1b and switching the optical switch 4, is omitted from this figure. However, it can be easily realized by using an ordinary electrical comparator circuit.

Next, to search for a fault point in the main optical fiber transmission line 6a, a test optical pulse signal of wavelength λ3 is sent from the main optical test circuit 23a to the optical fiber transmission R6a via the optical multiplexing/demultiplexing circuit 5a. This is performed by receiving backscattered light in the optical fiber transmission line 6a caused by this test light pulse by the optical test circuit 23a via the optical multiplexing/demultiplexing circuit 5a. This method of testing loss increase locations and breakage points depending on disconnections, bends, etc. of the optical fiber transmission line 6a is a commonly used method.

If a failure in the main optical fiber transmission line 6a is detected using the above method and it is confirmed that an abnormality will occur in communication, the optical switch 4 on the station side and the optical switch 7 on the subscriber side are activated and the backup system is activated. The optical fiber transmission line 6b is switched to the optical fiber transmission line 6b, and the optical output signal (wavelength λ1) of the electrical-optical conversion circuit 1a is transferred to the optical multiplexing/demultiplexing circuit 2a, the optical switch 4. It is sent to the subscriber side via the optical multiplexing/demultiplexing circuit 5b and the optical fiber transmission line 6b. Then, on the subscriber side, the optical signal received through the backup optical fiber transmission N6b is
The signal is received by a photoelectric conversion circuit 9 through an optical switch 7 and an optical multiplexing/demultiplexing circuit 8.

Although the switching control circuit for the optical switches 4 and 7 based on the output signal of the optical test circuit 23a is also omitted in this figure, it can be easily realized by a normal electrical comparator circuit.

As described above, in the bidirectional transmission system of the present invention, the output signal of the optical monitor circuit 3a allows the electrical signal to be transmitted from the main optical transmitter/receiver circuit composed of the electrical-optical converter circuit 1a and the optical-electrical converter circuit 11a. It is switched to a backup optical transmission/reception circuit composed of an optical conversion circuit 1b and an optical-electrical conversion circuit 11b, and the optical switch 4I:J switches from the main optical fiber transmission line 6a to the backup optical fiber transmission line 6b. can be switched to. Furthermore, when the optical test circuit 23a detects an abnormality in the main optical fiber transmission line 6a, its output signal causes both the optical switch 4 on the central office side and the optical switch 7 on the subscriber side to The fiber transmission line 6a is switched to the backup optical fiber transmission line 6b.

FIG. 2 shows an embodiment of a fail-safe type central office optical circuit. Here, it is configured as a waveguide type optical circuit, and can be realized by either a glass optical waveguide 1, a ferroelectric optical waveguide, a semiconductor optical waveguide, or a combination thereof. This optical waveguide is a buried type, a lodge type.

Any one of a loaded type, a raised type, a diffused type, or a combination thereof can be used.

Next, individual optical circuits will be explained.

2a is a main optical multiplexing/demultiplexing circuit, and 2b is a backup optical multiplexing/demultiplexing circuit, each having a function of multiplexing/demultiplexing optical signals of wavelengths λ1 and λ2. Here, the main optical multiplexing/demultiplexing circuit 2a is an optical directional coupling circuit 15a having the same structure.

A standby optical multiplexing/demultiplexing circuit 2b consisting of 16a and 24a.
is an optical directional coupling circuit 15b having the same structure.

It consists of 16b and 24b. That is, the electrical-optical conversion circuit 1
The optical signal with the wavelength λ1 from the source a<lb) passes through the optical directional coupling circuits 15a (15b) and 24a (24b) and is directed to the arrow 17a (19a).

17b (19b), and the arrow 18a (20
The optical signal of wavelength λ2 propagated as shown in a) is sent to the optical directional coupling circuit 24a (24b).

16a (16b) as shown by the arrow 18b (20b), and is converted into an electrical signal by the optical-to-electrical conversion circuit 11a (llb>).

The optical directional coupling circuits 15a and 15b also serve as optical monitor circuits that monitor the optical signal of wavelength λ1. That is,
The optical output signal of the electrical-optical conversion circuit 1a (lb) is converted into an arrow 17a (1) by the optical directional coupling circuit 15a (15b).
9a), but an optical signal attenuated by about -20 dB also leaks and propagates in the direction of arrow 17c (19c). Therefore, the light intensity of this leaked light is
By detecting it with the electrical conversion circuit 30a (30b), it is possible to determine the abnormal state of the electrical-optical conversion circuit 1a (lb). And the above light monitoring light -
The output signal of the electrical conversion circuit 30a (30b) is fed back to the driving voltage source 13 of the optical switch 4 and used as a switching control signal for the optical switch 4, and is also fed back to the control circuit 100 of the optical transmitting/receiving circuit.
Main electrical-optical conversion circuit 1a and optical-electrical conversion circuit 11
a is used as a switching control signal Xl to the backup electric-optical conversion circuit 1b and optical-electrical conversion circuit 11b.

In addition, 14 is a ground electrode', 4a is a main system optical directional coupling circuit, and 4b is a backup system optical directional coupling circuit, which receives an optical signal of wavelength λ3 propagating as shown by arrow 22a (22b). , arrow 17b (19b),
18a (20a>) and propagate the wavelength λ
The optical signals of λ1 and λ2 are of a structure in which they are not demultiplexed.

The output signal of the optical test circuit 5a (5b) is transmitted to the control circuit 60a.
(60b) is fed back to the voltage source 13.

Next, the optical switch 4 will be explained.

In this method, two single mode optical waveguides having exactly the same structural dimensions are placed close to each other, and the coupling region is provided with a planar electrode 21a.
, 21b (Nishihara, Haruna, Suhara, “
“Optical Integrated Circuit” published by Ohmsha, February 25, 1985, No. 1
First edition published, pp. 304-306).

By applying the applied voltage V from the voltage source 13, the propagation constant difference Δ
For example, an optical signal propagating in the optical waveguide 2woa can be propagated into the optical waveguide Fl@26a or 26b. Furthermore, the optical signal propagating within the optical waveguide 26a can be propagated into the optical waveguide 25a or 25b. That is, the optical waveguide 25a (2
6a) is the optical signal propagating in the optical waveguide 26b (2
5b) As a condition for switching to Δβ=0゜L/j'=2α〒1 (α=o, 1, 2.)''
... (1) The applied voltage V is adjusted to satisfy the following conditions, and the conditions for the optical signal propagating in the optical waveguide 25a (26a) to be switched into the optical waveguide 25a (26a) are: ...(2) However, 1. l! : Length of joint.

L: complete bond length.

By adjusting the applied voltage ■ to satisfy
Optical switching operations can be performed.

In the above embodiment, for example, the wavelength λ1=1.3μm1λ
2=1.55 μm and λ3=1.65 μm are used.

The present invention is not limited to the above embodiments. For example, λ1 =
1.52μm, λ2=1.56μm, λ3=1.65
When μm is used, the optical multiplexing/demultiplexing diagrams R2a, 2b can be realized by using, for example, a Matsuhara Kneader type optical multiplexing/demultiplexing circuit.

In addition to the configuration of the above embodiment, the optical switch 4 may be, for example, a cross-type optical switch using a semiconductor material, an optical fiber type mechanical optical switch, or the like. Further, the optical multiplexing/demultiplexing circuits 4a and 4b may also be of optical fiber type.

Although FIG. 2 describes the optical circuit on the central office side, the optical circuit on the subscriber side (optical switch 7, optical multiplexing/demultiplexing circuit 8, optical-to-electrical conversion circuit 9, and electric-to-optical conversion circuit 10) is similar. It is clear that it can be constructed from optical waveguides.

[Effects of the Invention 1 As described above, the present invention can produce the following excellent effects.

(1) It has a completely redundant fail-safe configuration, so if a failure occurs in the optical fiber transmission line, it can switch to the pre-anchor system and maintain communications between the station and subscribers. . In addition, in the case where an optical monitor circuit is provided, even if a failure occurs in the transmitter/receiver circuit, it is possible to switch to a subband system and maintain communication between the station and the subscriber. Therefore,
A highly reliable optical transmission and reception system can be realized.

(2) A fail-safe optical transmission/reception system using feedback control can be implemented without disconnecting communication between the station and the subscriber.

(3) In the optical circuit, since the optical transmitter/receiver circuit on the central office side can be constructed with a leading waveguide structure on a single substrate, mass production is possible and a significant cost reduction can be expected.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of the fail-safe optical transceiver system of the present invention, Fig. 2 is a configuration diagram of the optical circuit of the optical transmitter/receiver section on the central side which is an embodiment of the present invention, and Fig. 3 is a diagram showing a conventional optical transceiver system. 1 is a diagram showing the configuration of an optical transmission/reception system. In the figure, 1a and 1b are electrical-optical conversion circuits (optical transceiver circuits)
, 2a, 2b are optical multiplexing/demultiplexing circuits, and 3a. 3b is an optical monitor circuit, 4 is an optical switch, and 5a. 5b is an optical multiplexing/demultiplexing circuit, 6a and 6b are optical fiber transmission lines,
7 is an optical switch, 8 is an optical multiplexing/demultiplexing circuit, 9 is an optical-electrical conversion circuit, 10 is an electrical-optical conversion circuit, and 11a and llb are optical-
Electrical conversion circuit (optical transceiver circuit IN), 13 is a driving voltage source, 14 is a ground electrode, 23a and 23b are optical test circuits, 1
00 indicates a control circuit of the optical transmitter/receiver circuit. Patent applicant: Nobuo Sekitani, Patent Attorney, Hitachi Cable Co., Ltd.

Claims (1)

[Claims] 1. A main system and a protection optical fiber transmission line connect the station and the subscriber, and the station side receives optical signals of wavelengths λ1 and λ2 as the main system circuit and the protection system circuit. An optical transmitting/receiving circuit for transmitting and receiving, an optical multiplexing/demultiplexing circuit for multiplexing and demultiplexing the optical signals, and an optical test circuit for testing and monitoring failures in the optical fiber transmission line by transmitting an optical pulse signal of wavelength λ3 to the optical fiber transmission line. At the same time, an optical switch is installed to switch between the main and protection circuits, and on the subscriber side, there is an optical switch to switch between the main and protection optical fiber transmission lines, an optical multiplexing/demultiplexing circuit, and optical signals with wavelengths λ2 and λ1. An optical transmitter/receiver circuit is installed to send and receive optical fibers, and when a fault in the optical fiber transmission line is detected by the optical test circuit, the optical switch installed on the station side and the subscriber side switches the optical fiber transmission line to the main system. A fail-safe optical transmission/reception system that is characterized by switching from 1 to 2 to a standby system. 2. The switching from the main system to the backup system of the optical fiber transmission line according to claim 1 is performed by feedback control of the output of the optical test circuit to the optical switch at the central office side. Fail-safe optical transmission and reception method. 3. The office side according to claim 1 is further provided with an optical monitor circuit that monitors the transmitted optical signal in the optical path of the main system and the protection system, and the optical monitor circuit detects abnormalities in the optical output of the optical transmitter/receiver circuit of the main system. 2. The fail-safe optical transmitting and receiving system according to claim 1, wherein when the optical transmitting and receiving circuit is detected, the optical transmitting and receiving circuit is switched to a standby system and the optical switch is also switched to a standby system. 4. Switching the optical transmitting/receiving circuit and the optical switch on the central office side to the standby system according to claim 3 is achieved by feedback control of the output of the optical monitor circuit to the optical switch on the central office side and the control circuit of the optical transmitting/receiving circuit on the central office side. 4. The fail-safe optical transmission/reception system according to claim 3, wherein the fail-safe optical transmission/reception system is carried out by: 5. A fail-safe optical circuit, characterized in that the optical circuits on the station side and the subscriber side according to claim 1 or 3 are constituted by optical waveguides.