JPS6141184B2 - - Google Patents

Abstract

PURPOSE:To make it possible to constitute many communication channels with one loop light line by applying the technique of light-wavelength multiplex transmission. CONSTITUTION:Center 1, and communication terminals 2, 3 and 4 are coupled in a loop via loop light line 10; and a light wave of wavelength lambda1 is permitted to propagate through line 10 clockwise, and that of lambda2 counterclockwise. At each communication terminal, light waves of lambda1 and lambda2 from light lines 10' and 10'' are partially extracted and applied to photoelectric converters 47 and 47' by light filter 31 that transmits partially the light wave of lambda1 while reflecting the rest and further provides the total reflection of the other light wave of lambda2 and light filter 32 that transmits part of the light wave of lambda2 while reflecting the rest and further provides the total reflection of the light wave of lambda1; and light waves lambda1 and lambda2 from electro- optic converters 46 and 46' are sent to light lines 10'' and 10' respectively, and partially supplied to photoelectric converters 47 and 47'.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical loop communication network using optical wavelength division multiplexing transmission technology.

The optical loop network has the basic configuration shown in FIG. 1
is a center, 2 to 4 are communication terminals, and 10 and 11 are optical (fiber) lines. The center and communication terminals are
They are connected in a ring by loop optical paths 10 and 11.
Conventionally, in this type of network, each communication terminal often had an optical/electrical coupler whose configuration is shown in FIG.
Reference numerals 21 and 21' are electrical/optical converters, 22 and 22' are optical system controllers, 23 and 23' are optoelectric converters, and 24 is a terminal controller. The optical signal propagating through the optical path 10 is converted into an electrical signal by the optical-to-electrical converter 23', and the signal from the terminal controller 24 is superimposed on it, and then changed into an optical signal again by the electrical-to-optical converter 21'. , propagates through the optical path 10. In such an optical loop network, if there is a failure in even one of the communication terminals connected in a ring, the entire loop becomes unable to communicate. In order to overcome this drawback, a double loop as shown in FIG. 1 has been conventionally used. That is,
Optical lines 10 and 11 are used to create two communication paths in opposite directions, and normally one of them is used for communication, but in the event of a failure, communication is performed using the two communication paths. There is. By forming a double loop in this way, communication can be performed not only when a communication terminal failure occurs but also when a line failure occurs. During normal operation, communication is performed through one communication path, but for example, as shown in FIG. 3, communication terminal 3
If a line failure occurs between the communication terminals 3 and 4, the communication terminals 3 and 4 turn back and communicate using two communication paths in opposite directions. Broken lines 12 and 13 in FIG. 3 indicate the communication paths. However, in this example, two optical lines are required, and if the loop length is long, the line cost will be relatively high. Furthermore, as the number of types of signals to be transmitted increases, the number of lines will further increase.

Therefore, the present invention is intended to improve the above-mentioned drawbacks of the conventional technology, and its purpose is to create an economical and inexpensive loop network by configuring a large number of communication paths with a single circular optical line using optical wavelength division multiplexing transmission technology. Our mission is to provide
Its feature is that in a communication system where a center and multiple communication terminals are connected in a ring via a single optical path, each communication terminal is connected to a light beam that partially transmits light waves of a specific wavelength and reflects light waves of other wavelengths. The center is coupled to the optical line using multiple types of filters, and the center is coupled to the optical line using multiple types of optical filters that transmit light waves of a specific wavelength and totally reflect light waves of other wavelengths.
It is an optical ring network using optical wavelength division multiplexing transmission, in which a plurality of communication paths are realized in a single ring optical path using a plurality of light waves having different wavelengths.

This will be explained in detail below with reference to the drawings.

FIG. 4 shows an embodiment of the present invention, in which 1 is a center, 2, 3, and 4 are communication terminals, 10 is a circular optical path,
λ ₁ and λ ₂ are the wavelengths of light waves. The center 1 and the communication terminals 2, 3, and 4 are connected in a ring shape by a ring optical path 10. A light wave with a wavelength λ ₁ propagates clockwise in the annular optical path 1, and a light wave with a wavelength λ ₂ propagates counterclockwise.

FIG. 5 shows the configuration of the optical system of the communication terminal. 1
0', 10'' are part of the circular optical transmission line, 31, 32
is an optical filter, 46, 46' are electrical/optical converters, 47, 47' are optical/electrical converters, 49, 4
9' is an optical system control section, and 48 is a terminal control system. As shown in FIG. 6, in the optical filter 31, the wavelength λ
Part of the light wave ₁ is transmitted and part of it is reflected. Furthermore, the light wave with wavelength λ ₂ is totally reflected. Conversely, the optical filter 32 transmits a portion of the light wave of wavelength λ ₂ and reflects the portion.
On the other hand, a light wave with wavelength λ ₁ is totally reflected. Wavelength λ ₁ incident on the optical filter 31 from the upper right transmission line 10'
A part of the light wave is reflected, a part passes through the optical filter 31, is converted into an electrical signal by the optical-to-electrical converter 47, and is sent to the terminal controller 48 via the optical system controller 49. On the other hand, from the transmission line 10' to the optical filter 31
The part of the optical path with wavelength λ ₁ that is incident on the annular optical path and reflected here is totally reflected by the optical filter ₃₂ and coupled to the transmission line 10''. The light wave of λ ₂ is on the lower left transmission line 1
0'' to the optical filter 32, part of it is reflected, and part of it passes through the optical filter 32 and enters the optical-to-electrical converter section 47', where it is converted into an electrical signal and sent to the optical system control section 49'. On the other hand, the wavelength λ reflected by the optical filter 32
_{The second} light wave is totally reflected by the optical filter 31 and coupled to the transmission line 10'. When there is a signal to be sent from the communication terminal, the signal is sent from the terminal control section 48 to the optical system control section 49 or 49', converted into an optical signal, and sent to the circular optical path. For example, in the case of transmitting an exchange wave with a wavelength λ ₁ , the signal is converted into an optical signal by an electric/optical converter 46 having a light source with a wavelength λ ₁ and enters the optical filter 31 . A part of the light is reflected here, and the light/electricity converter 47
incident on . This light is used to monitor the optical output level and timing of the electrical/optical converter 46. on the other hand,
The light transmitted through the optical filter 31 passes through the optical filter 32
When transmitting a light wave with a wavelength λ ₂ , the optical signal is transmitted from an electrical-to-optical converter 46' having a light source with a wavelength λ ₂ .

FIG. 7 shows the configuration of the optical system of the center 1. 33,
34, 35, and 36 are optical filters. The optical filters 34 and 36 transmit light waves of wavelength λ ₂ and transmit light waves of wavelength λ 2.
Reflects the light wave of ₂ . The optical filters 33 and 35 transmit light waves with a wavelength λ ₂ and reflect light waves with a wavelength λ ₁ . The light wave of wavelength λ ₁ that has been emitted from the optical transmission line 10 is reflected by the optical filter 33 , transmitted through the optical filter 34 , and enters the optical/electrical converter 46 . wavelength λ ₁
When transmitting an optical signal from the center, the optical signal is sent out from the electrical/optical converter 47 and passed through the optical filter 3.
6 and is coupled to the optical transmission line 10〓. On the other hand, the light wave of wavelength λ ₂ emitted from the optical transmission line 10 is reflected by the optical filter 36 and passes through the optical filter 35 as a light wave.
The light enters the electric converter 47'. On the other hand, the light wave of wavelength λ ₂ that exits the electric/optical converter 46' is filtered through the optical filter 3.
3 to the optical transmission line 10.

In this way, light waves propagating in the opposite direction along the annular optical transmission path are sent out from the center 1.

By transmitting the same information in the opposite direction within the same circular optical path, a highly reliable optical ring network can be constructed.
Also, a digital signal is transmitted using a light wave with a wavelength of λ ₁ , and a digital signal with a wavelength of λ
_2. Analog signals can be transmitted using light waves.

In the loop network shown in Figure 4, when communication between the center and communication terminals is performed at high speed and with high efficiency by time division multiplexing, the optical system of each communication terminal is synchronized with the optical signal propagating through the circular optical transmission path. There must be. FIG. 8 shows an example of the configuration of a communication terminal optical system control section for this purpose. 51 is an amplifier, 52 is a wavelength equalizer, and 53 is an amplifier.
AGC system, 54 is an identification circuit, 55 is a timing extraction circuit, 56 is a frame synchronization circuit, 57 is an automatic phase adjustment circuit, and 58 is a transmission signal gate. light·
The output of the electrical converter 46 is amplified by an amplifier 51, passed through an equalizer 52, and then reproduced by a discriminator 54. On the other hand, timing information and a frame synchronization signal are extracted from the output of the equalizer 52. The phases of these signals are adjusted by an automatic phase adjustment circuit so that the transmission optical signal is synchronized with the circular optical path.

In the embodiment shown in FIG. 4, there are two light waves, but if the number of types of optical filters at the center and each communication terminal is increased,
A larger number of communication transmission lines can be configured in one circular optical line. Digital signals with different modulation speeds and analog signals with different modulation frequencies can be transmitted through the same circular optical path. Figure 9
shows the configuration of an optical system of a communication terminal when five communication transmission lines are configured into a single circular optical transmission line.
37, 38, 39 are optical filters, and optical filter 3
7 transmits only the light wave of wavelength λ ₃ and reflects the others.
Each of the optical filters 38 and 39 partially transmits light waves with wavelengths λ ₄ and λ ₅ and reflects the others. Here, light waves with wavelengths λ ₁ , λ ₃ , λ ₅ and wavelengths λ ₂ , λ ₄ are used.
The light waves propagate in the opposite direction. For example, wavelength λ ₁ ,
Digital signals are converted into light waves of wavelengths λ ₂ and λ ₅ with wavelengths λ _{3 and} λ 5, respectively.
Analog signal signals can be transmitted using light waves of _λ4 .

By using two light waves with different wavelengths that propagate in a circular optical transmission line, it is possible to create a double loop and take measures against failures. For example, in the loop network in Figure 4, under normal conditions,
Communication can be performed using a light wave with a wavelength of λ ₁ , and the line and each communication terminal can be monitored using a light wave with a wavelength of λ ₂ propagating in the opposite direction. In the event of a failure, communication is performed using two optical waves with a broken length, as shown in FIG.
When the line is disconnected between the communication terminals 3 and 4, the clockwise and counterclockwise signals are converted in wavelength and returned at the communication terminals 3 and 4, respectively.

FIG. 11 shows an example of a frame structure of a light wave of wavelength λ ₁ when normal time division multiplex communication is performed using a light wave of wavelength λ ₁ and monitoring is performed using a light wave of wavelength λ ₂ .
70 is a time slot of a frame synchronization signal; 7;
71', 71'' are time slots for monitoring and control;
2, 72', 72'', 72 are signal transmission time slots. Supervisory control time slots 71,
Line and communication terminal monitoring signals are included in 71'71''.

FIG. 12 shows a procedure for loop network monitoring of an optical ring network in which normal communication is performed using a light wave of wavelength λ ₁ and monitoring is performed using a light wave of wavelength λ ₂ .

LC (λ ₁ ) is a monitoring signal carried by a light wave with a wavelength λ ₁ , LC′ (λ ₅ ) is a monitoring response signal carried by a light wave with a wavelength λ ₂ , and SW (λ ₁ ) is a monitoring signal carried by a light wave with a wavelength λ ₁ . The optical system control unit switching instruction signal, SW (λ
₂ ) is an optical system control section switching instruction signal sent by a light wave of wavelength λ ₂ . The monitoring signal LC (λ ₁ ) is shown in Fig. 1
The center sends the monitoring signal LC (λ 1 ) to each communication terminal at regular intervals, and each communication terminal receives the monitoring signal LC (λ ₁ ). ₁ ), the supervisory response signal CC' (λ ₂ ) is sent to the center.The center receives the supervisory response signal LC' (λ ₂ ) from each communication terminal.
is being monitored. When a line failure occurs between communication terminals 3 and 4, a monitoring response signal is sent from communication terminal 4.
LC′(λ ₂ ) is no longer received at the center. or,
The communication terminal 4 will no longer be able to receive the optical signal of wavelength λ ₁ . The optical system of the communication terminal 4 is switched so that normal signals are transmitted using light waves of wavelengths λ ₁ and λ ₂ . On the other hand, the center instructs each communication terminal to communicate using light waves of two wavelengths, and sends an optical system control switching signal SW (λ
₁ ), send SW(λ ₂ ). In this way, communication is performed using two wavelengths.

As explained above, according to the present invention, there is an advantage that a plurality of communication paths can be configured on one optical transmission line, and further, the line cost of the network can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a conventional optical loop network, FIG. 2 is a configuration diagram of an optical system in the communication terminal in FIG. 1, and FIG. 3 is a configuration diagram of a conventional optical loop network in a loopback state. 4 is a configuration diagram of an embodiment of the present invention, FIG.
is a diagram of the optical system configuration of the communication terminal in FIG. 4, FIG. 6 is a conceptual diagram of the wavelength dependence of the transmittance of the optical filter, FIG. 7 is a diagram of the optical system configuration of the center, and FIG. 8 is the configuration of the optical system control section of the communication terminal. Figure 9 shows an example of the configuration of another optical system of a communication terminal, Figure 1
0 is a configuration diagram of the loopback state,
FIG. 11 shows an example of a frame structure, and FIG. 12 shows an example of a fault monitoring system procedure. 1... Center, 2, 3, 4... Communication terminal, 1
0, 11, 10', 10''...Optical line, 21, 2
1', 46, 46', 46'', 46, 46〓...
Electrical/optical converter, 23, 23', 47, 47', 4
7〓... Optical/electrical conversion section, 49, 49'... Optical system control section, 48, 48'... Communication terminal control section, 51
...Amplifier, 52...Waveform equalization section, 53...
AGC, 54... Identification circuit, 55... Timing extraction section, 56... Frame synchronization detection section, 57...
automatic phase adjustment circuit, 58... gate circuit, 70...
...Frame synchronization signal time slot, 71, 7
1', 71''...Monitoring control time slot, 72,
72', 72'', 72...Time slot for information transmission, LC (λ ₁ )...Communication terminal monitoring signal,
LC' (λ ₂ )...Monitoring response signal, SW (λ ₁ ),
SW (λ ₂ )...Optical system control unit switching instruction signal.

Claims (1)

[Scope of Claims] 1. In a communication system in which a center and a plurality of communication terminals are connected in a ring via a single optical path, each communication terminal is configured to partially transmit light waves of a specific wavelength and reflect light waves of other wavelengths. The center is coupled to the optical path using multiple types of optical filters that transmit light waves of a specific wavelength and totally reflect light waves of other wavelengths, and An optical ring network using optical wavelength division multiplexing transmission, which is characterized by realizing multiple communication paths in a single ring optical path using a plurality of light waves with different wavelengths. 2. The invention according to claim 1, wherein at least one light wave propagates clockwise on the optical loop line, and the other light wave propagates counterclockwise. 3 Using two light waves that propagate in opposite directions on a circular optical line, during normal operation, one light wave performs communication between the center and each communication terminal, the other light wave monitors the communication network, and the line or The invention according to claim 2, wherein when a failure occurs in a communication terminal, communication between the center and each communication terminal is performed using both light waves. 4. Using two light waves that propagate in opposite directions through a circular optical path, such as transmitting the same information in opposite directions within the same circular optical path using the two light waves,
The invention according to claim 2.