JPS6139777B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a link coupler that is used as a link coupler in an optical loop network and can have a loop back function with a single optical fiber.

FIG. 1 is a block diagram illustrating the principle of a conventional link coupler. In the figure, 1 and 2 are optical fibers forming a main loop, 3 and 4 are optical fibers forming a backup loop, 5 is an optical fiber connector, and 6 is an optical fiber connector.
is a 2:2 optical switch, 7 and 8 are electrical/optical converters that convert electrical signals to optical signals, 9 and 10 are optical/electrical converters that convert optical signals to electrical signals, and 11 is a loopback mode switch. 12 is a transmitting signal terminal, and 13 is a receiving signal terminal.

First, during normal operation, the optical signal input from the optical fiber 1 of the main loop passes through the connector 5 and is sent to the optical switch 6.
The signal passes through the optical/electrical converter 9, converts the signal into an electrical signal, and receives the signal at the receiving signal terminal 13. Further, the electrical signal sent out by the transmission terminal 12 is converted into an optical signal by the electrical/optical converter 7, and is transmitted to the downstream station via the optical fiber 2 of the main loop. Next, the electric switch 11 is a switch that operates in the loopback mode, and for example, if the optical fibers 2 and 3 on the left side in the figure are disconnected, the electrical switch 11 receives the optical signal through the optical fiber 1 of the main loop, and The received signal 13 is received as shown in FIG. On the transmitting side, a signal is transmitted from a transmission signal terminal 12, is converted into an optical signal by an electrical/optical converter 8 via an electric switch 11, and is used to construct and maintain a loop for performing so-called loopback using the optical fiber 4 of the backup loop. Further, the optical switch 6 is an optical switch for optically connecting the input terminals and output terminals of the main loop and the backup loop to each other in the bypass mode, so-called bypassing.

Figure 2 is an explanatory diagram of the loopback mode, where C ₁ , C ₂ , C ₃ , and C ₄ are link couplers connected to the station, L ₁ is the main loop optical fiber, and L ₂ is the main loop optical fiber. The fiber optic in the reserve loop is shown and the fiber optic is connected between link couplers C ₃ and C ₄ .
This shows the case where L ₁ and L ₂ are disconnected. In this case, link couplers _C3 and _C4 are in loopback mode to configure and maintain the loop.

As described above, bypass mode and loopback mode are necessary functions from the viewpoint of network reliability in the configuration of a loop network, and most systems have this function. However, 2
Since the loopback mode is configured using a regular optical fiber, there are economical problems due to the cost of the optical fiber, the number of optical fiber connectors, and the need for two 2:2 optical switches.

In order to solve these conventional problems, the present invention uses two light emitting sources with different wavelengths, and uses wavelength multiplexing technology to provide bypass mode and loopback mode functions with a single optical fiber. be. The present invention will be explained in detail below with reference to the drawings.

FIG. 3 is a block diagram explaining the principle of the wavelength division multiplexing link coupler of the present invention.
2 is a bidirectional optical fiber as a transmission line, 23
24 is an optical fiber connector, 24 is an optical switch in bypass mode, 25 is a multiplexer/demultiplexer circuit with two sets of multiplexer/demultiplexer that bidirectionally multiplexes and demultiplexes two wavelengths λ ₁ and λ ₂ , 26 and 27 are multiplexer/demultiplexer circuits. Light with respective wavelengths λ ₁ and λ ₂ /
Electrical converters 28 and 29 are electrical/optical converters for wavelengths λ ₁ and λ ₂ respectively, 30 is an electric switch operating in loopback mode, 31 is a receiving signal terminal, and 32 is a transmitting signal terminal.

Next, its operation will be described.

First, during normal operation, an optical signal of wavelength λ ₁ received from the optical fiber 21 passes through the connector 23 and the optical switch 24, passes through the multiplexing/demultiplexing circuit 25, is converted into an electrical signal by the optical/electrical transformer 26, and is received. The signal is received at the signal terminal 31. Further, the transmission signal is transmitted from the transmission signal terminal 32, converted into an optical signal by the light emitting element of wavelength λ ₁ of the electric/optical converter 28, and transmitted to the downstream station via the optical fiber 22 by the multiplexing/demultiplexing circuit 25. Ru.

Next, the operation in the loopback mode will be explained using an example in which the optical fiber 21 is disconnected.

First, on the transmitting side, the transmitting signal terminal 32 is connected as in normal operation.
The signal is then converted into an optical signal by a light emitting element with a wavelength λ ₁ in the electro/optical converter 28 and transmitted to a downstream station via the optical fiber 22. The receiving side uses the wavelength λ from the downstream station.
₂ optical signals are received, and the optical/demultiplexing circuit 25
The optical signal is guided to an electric converter 27, where the optical signal is converted into an electric signal and received by a reception signal terminal 31. Further, in the bypass mode, the 2:2 optical switch 24 can be used to set the bypass mode.

FIG. 4 is an explanatory diagram of the loopback mode based on the link coupler of the present invention, in which C ₂₁ , C ₂₂ , C ₂₃ ,
C ₂₄ is a link coupler of the present invention connected to each station, and L is one optical fiber. As shown in the figure, the optical fiber between Link Cutup Plas C ₂₃ and C ₂₄ is disconnected.
C ₂₃ and C ₂₄ each take a loopback mode to configure and maintain the loop. In the figure, → indicates the wavelength λ ₁ and 〓 indicates the wavelength λ ₂ .

FIG. 5 is a connection diagram showing an embodiment of the wavelength multiplexing link coupler of the present invention, in which the light emitting elements have wavelengths λ ₁ , λ 1 ,
A dielectric interference film filter is used as a multiplexer/demultiplexer for the λ ₂ LED. In the figure, 41 and 42 are bidirectional optical fibers as transmission paths, 43 is an optical fiber connector, 44 is a movable mirror that serves as an optical switch, and 45 is a long wavelength band, for example, for passing an optical signal of wavelength λ ₂ . Interference membrane filter (Iwp), 4
6 is an interference film filter (SWP) that passes an optical signal in a short wavelength band, for example, wavelength λ ₁ ; 47 is a photodiode that converts an optical signal with wavelength λ ₁ into an electrical signal; 4
8 is a photodiode that converts an optical signal with wavelength λ ₂ into an electrical signal, 49 is a light emitting element (LED) with wavelength λ ₂ , and 50 is a light emitting element (LED) with wavelength λ ₁ .

Next, its operation will be explained.

First, during normal operation, the movable mirror 44 is removed,
The optical signal of wavelength λ ₁ received by the optical fiber 41 is reflected by the Iwp 45 and sent to the photodiode 47.
is converted into an electrical signal and received. On the other hand, the transmission signal is converted into an optical signal of wavelength Aλ ₁ by the LED 50, passes through the SWP 46, and is transmitted to the downstream station via the optical fiber 42.

Next, the operation in loopback mode will be explained using an example where the optical fiber 41 is disconnected.
As for transmission, the optical signal is transmitted by the LED 50 to the downstream station via the optical fiber 42 as in the normal state. On the other hand, in reception, an optical signal of wavelength λ ₂ is received from the downstream station through the optical fiber 42, reflected by the SWP 46, converted into an electrical signal by the photodiode 48, and received. In addition, in the bypass mode, the movable mirror 44 is fixed at the position shown in the figure, and the optical fiber 4
1 and 42 are optically connected.

In this way, two optical fibers can be reduced to one, and the number of components such as optical fiber connectors and optical switches can be reduced, while maintaining the same functions as in the prior art. Moreover, if fiber transmission loss is ignored, lossless transmission is possible in principle, and a high-quality loop network can be realized in which crosstalk can be ignored even if there is reflection from the transmission path. Furthermore, conventionally, there are usually two loops: a main loop and a backup loop.
Since the core optical fiber is cabled into one cable, in most cases of an optical fiber breakage accident, two optical fibers are cut at the same time, so it is necessary to make one optical fiber. reliability will not be compromised.

As explained in detail above, according to the present invention, 1
Since the loop network with bypass and loop back functions is constructed using optical fibers, there is a great effect that the network can be constructed with fewer components and is economical.

[Brief explanation of the drawing]

FIG. 1 is a block diagram explaining the principle of a conventional optical link coupler, FIG. 2 is a diagram explaining the loopback mode thereof, and FIG. 3 is a block diagram explaining the principle of the wavelength division multiplexing link coupler of the present invention. Figure 4 is also an explanatory diagram of the loopback mode, Figure 5
The figure is a connection diagram showing an embodiment of the wavelength division multiplex link coupler of the present invention. 21, 22... Bidirectional optical fiber, 23... Optical fiber connector, 24... Optical switch, 25... Multiplexing/demultiplexing circuit, 26, 27... Optical/electrical converter, 28, 29
...Electronic/optical converter, 30... Electric switch, 31... Reception signal terminal, 32... Transmission signal terminal, C ₂₁ , C ₂₂ ,
C ₂₃ , C ₂₄ ...Link coupler, L...Bidirectional optical fiber, 41, 42...Bidirectional optical fiber, 43...
Optical fiber connector, 44...Movable mirror 45...Interference film filter that passes long wavelength band (λ ₂ ), 4
7... Interference film filter that passes short wavelength band (Aλ ₁ ), 47... Photodiode with wavelength λ ₁ , 48...
Photodiode with wavelength λ ₂ , 49...Light emitting element (LED) with wavelength λ ₂ , 50... Light emitting element (LED) with wavelength λ ₁ .

Claims (1)

[Claims] 1 Two light emitting elements with different wavelengths are used to form an optical loop network using one wavelength under normal conditions, and when a loopback mechanism is required due to an abnormality such as an optical fiber break, two wavelengths are used using wavelength multiplexing technology. In a wavelength multiplex link coupler that configures and maintains a loop network using a single optical fiber, a light-receiving element and a light-emitting element of different wavelengths are optically connected to the optical fiber by transmission or reflection. A wavelength link coupler characterized in that a filter is attached to each optical fiber, and a movable mirror that operates in a bypass mode and optically connects the optical fibers is attached.