JPH0322722A - Optical communication network - Google Patents

Abstract

PURPOSE:To connect many stations and enable the optical communication network to operate irrelevantly to an optical fiber disconnection and a station power-off state and to eliminate a station which needs to send a disconnection supervisory signal by forming a single-line duplex communication and branch type optical communication network of optical fibers. CONSTITUTION:An optical communication equipment 1 of each station in the network is equipped with N optical fiber connection terminals 18-20. Light signals are passed directly through two of the terminals with a passage loss larger than a prescribed loss, other terminals are all connected to an electrooptic converting device (E/O)3 and an optoelectric converter (O/E)12, and a signal with prescribed pulse width is pregenerated and repeated when the output of the O/E12 rises. Consequently, various type network can be applied, a communication function can be held without reference to a local optical fiber disconnection and a station power-off state, and a communication is made without requiring any disconnection supervisory signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a single line bidirectional communication/branch type optical communication network using optical fibers, and particularly to this type of optical communication network having a relay function.

(Prior Art) FIG. 7 shows a configuration diagram of a conventional single-line bidirectional communication facility as disclosed in, for example, Japanese Patent Application Laid-Open No. 56-761 "Data Highway Transmission Apparatus".

In FIG. 7, 1 is an optical communication device, 2 is a terminal device (hereinafter, the combination of 1 and 2 is referred to as a station), and 3 is an electro-optic converter (
(hereinafter referred to as E/O). 4, 7, 8, and 1l are lenses, 5 is an optical directional coupler, 6 is a prism, 9.10 is an optical fiber, and 12 is a photoelectric converter (hereinafter referred to as 0/E).

Optical communication device 1 for single-line bidirectional communication configured as above
works as follows.

The signal transmitted from the terminal device 2 is subjected to electro-optical conversion at E/03 and converted into a parallel beam by lens 4, passes through directional coupler 5, and is split into left and right beams by prism 6. The optical signals branched to the left and right are coupled to optical fibers 9 and 10 by lenses 7 and 8, respectively, and transmitted in both left and right directions. The signal transmitted through the optical fiber 10 from the right direction is
After becoming a parallel beam in the lens 8, a part of the beam passes to the left, is coupled to the optical fiber 9 by the lens 7, and is transmitted to the left. The remaining optical signal has its optical path bent by the prism 6 and is guided to the directional coupler 5. The directional coupler 5 bends the optical path of the signal coming from the prism direction toward the lens 11, and couples the signal to 0/E12 by the lens 11. The optical signal transmitted through the optical fiber 9 from the left direction is similarly coupled to the optical fiber 10 direction and 0/E 1 2. O/E
12 outputs are output to the terminal device 2.

FIG. 8 shows the configuration of a single-line bidirectional communication network using conventional stations.

In FIG. 8, 13 is a disconnection detection automatic recovery device, 14 is an optical fiber, 15 is an optical switch, 16 is an optical splitter, and 17
is the A-ε monitoring circuit.

The network consists of optical communication equipment 1 for each station A, B, C, D, and E.
and a disconnection detection automatic recovery device l3 are connected in a loop with an optical fiber 14. T as an access method
D M A (time division multi
Let us consider the case where the ``ple access'' method is used.

When there is no disconnection in the loop, disconnection detection automatic return device 13
The loop is opened by a light switch 15 inside.

The optical signal transmitted from the optical communication device 1 of station A circulates around the loop in both directions. The optical signal circulating clockwise is optically branched in the optical communication device 1 of each station, goes around the loop and reaches the disconnection detection automatic recovery device 13, and Ichiro's signal is sent from the optical splitter 16 to 0/0 for detecting a disconnection. E 1 2 and the others are discarded from the bus at the optical switch 15 . The optical signal circulating counterclockwise is optically branched in the optical communication device 1 of the A station, circulates around the loop, reaches the disconnection detection automatic recovery device 13, and is discarded from the bus by the optical switch 15. The TDMA system requires a reference station that transmits frame signals called reference bursts. In the conventional example, station A is the reference station. Each station transmits and receives signals using signal transmission time slots determined based on the station A transmission signal. In the disconnection detection automatic recovery device 13, 0/E
12 outputs are input to a signal monitoring circuit 17. The signal monitoring circuit 17 detects a disconnection based on the presence or absence of a station A signal, which is a reference station, included in the received signal. When the signal monitoring circuit 17 detects a disconnection, it closes the optical switch 15 and reconfigures the network by using the disconnected point as an open point. However, it is not possible to reconfigure the network if there are disconnections at two or more locations.

The access method is CSMA/CD (carrie
r sense a+uLiple access w
Although other methods such as a collision detection method or a token bus can also be applied, it is necessary to devise a method for transmitting a signal from the A station to monitor the disconnection state in order to implement the above-mentioned disconnection countermeasures.

Since the loop network shown in FIG. 8 is branched and added using passive branch circuits, the E/0 3 of the optical communication device 1 is required to have high output, and the O/E 1 2 is required to have high sensitivity. However, in reality, the number of connectable stations is 8 to 20 stations.

(Problems to be Solved by the Invention) Conventional networks were configured as described above, so it was difficult to connect many stations within a loop, optical communication equipment was expensive, and wire breaks were common. Although one point of disconnection is allowed, the network will not operate if there is more than one disconnection, and even if the access method does not require a reference station, it will require a station to transmit a disconnection monitoring signal, making the network complex.

This invention was made under these circumstances,
A large number of stations can be connected, and the optical fiber will be disconnected. It is an object of the present invention to provide an optical communication network that can operate even when the power of a station is cut off and that does not require a station to transmit a disconnection monitoring signal.

(Means for Solving the Problem) In order to achieve the above object, the present invention configures an optical communication network as shown in (1) below.

(1) A single-wire bidirectional communication/branch type optical communication network in which a plurality of stations are connected by a single-line bidirectional communication/branching optical fiber with respect to the maximum inter-station connection distance, and the said station is a Ni of the following a to i.
A single-line bidirectional communication/branched optical communication network that includes the following components.

a. Electro-optical converter.

b. Photoelectric converter.

c. 1st. second and third to Nth optical fiber connection terminals;

d. Optical coupling means provided between the first, second and third to Nth optical fiber connection terminals and the electro-optic converter.

e. Said 1st. Optical coupling means provided between second and third to Nth optical fiber connection terminals and the opto-electrical converter.

f. Optical coupling means provided between the first and second optical fiber connection terminals and having a passage loss of 1/(N·fi+1) or more.

g. Pulse width reproducing means for capturing the rising edge of the output pulse signal of the opto-electric converter, regenerating a pulse signal with a specified pulse width length, and supplying the pulse signal to the electro-optic converter.

h. Means for receiving a signal required by the station via the pulse width regeneration means and transmitting a signal for the station via the electro-optical converter.

1. Means for stopping the fiber operation by the pulse width regeneration means during the transmission period of the station.

[Function] With the configuration in () above, it can be applied to various types of networks, and the communication function can be maintained even if some optical fibers are disconnected or the power of the station is cut off, and communication can be performed without requiring a disconnection monitoring signal. .

〔Example〕

Hereinafter, this invention will be explained in detail with reference to Examples.

FIG. 1 shows a configuration diagram of a station used in an "optical communication network" which is a first embodiment of the present invention.

In the figure, l is an optical communication device, 2 is a terminal device, and 3 is an E/
0.1 2 is 0/E, 18, 19.20 are first, second and third optical fiber connection terminals, 18a, 18b, 18c
．． 19a, 19b, 20a, and 20b are thin fibers (optical coupling means), 21 is a middle N1 control circuit (means for stopping the relay operation), and 22 is a pulse width regeneration circuit.

Next, the operation of this optical communication device 1 will be explained.

In FIG. 1, three optical fiber connection terminals 18, 19
．． The bidirectional optical signal ε inputted and outputted from 20 is branched within the optical communication f3 device 1, passes through E/03 and O/E12, and is coupled to the opposing optical fiber. That is, the optical fiber connection terminal 18 connects each thin fiber 18a . 18b and 18c pass through E/03 and 0/E12 and are coupled to the opposing optical fiber 19. The optical fiber connection terminal 19 is
Each thin fiber 19a. E/03 due to 19b, 18c
, O/E 1 2 and is coupled to the opposing optical fiber connection terminal 18 through it. The optical fiber connecting terminal 20 is connected to E/03 and O/ by each thin fiber 20a, 20b.
It is coupled to E 1 2.

E/03 converts the electrical signal output from the relay control circuit 21 into an optical signal and connects the optical fiber connection terminals 18, 19.20.
Output to.

0/E 1 2 is the optical fiber connection terminal 18, 19.2
The optical signal received from 0 is photoelectrically converted and output to the pulse width regeneration circuit 22. The output signal of the pulse width regeneration circuit 22 is
It is output to the relay control circuit 21 and the terminal device 2.

The optical fiber 18c is an optical coupling means that bidirectionally couples optical signals transmitted bidirectionally through the optical fiber connecting terminal 18 and the optical fiber connecting terminal 19, and has a specified passage loss as described later. The pulse width regeneration circuit 22 captures the rising edge of the O/E 1 2 output signal, regenerates it into a specified pulse width, and outputs it.

The relay control circuit 21 connects the terminal device 2 and the pulse width regeneration circuit 2.
During the transmission period of the station, the output of the terminal device 2 is supplied to the E/03, and during the non-transmission period, the output of the pulse width regeneration circuit 22 is supplied to the E/03.

Figure 2 shows the configuration of the "optical communication network" that is the first embodiment. As shown in the diagram, A, G
This is a network in which three buses are wired in three directions: station, C, D, E, and F stations. In the figure, A, B, C, D
, E, F, and G stations are optical communication devices with the same configuration. However, A. The optical fiber connection terminals 20 of stations G, C, and E are in an unused state. Also, the optical fiber connection terminals 18 and optical fiber connection terminals of the optical communication devices 1 of B, C, and D stations! 9 are connected by an optical fiber 23, and the optical fiber connection terminals 20 and 18 of the B and E stations are connected by the optical fiber 24.
The optical fiber connection terminal 19 of E station and F station
and the optical fiber connection terminal 1B are connected by an optical fiber 23, and furthermore, the optical fiber connection and i terminal 20 of the F and D stations are connected by an optical fiber 24, and a loop is formed at the B, E, F, D, and C stations. It consists of

First, the transmission/reception/relay operations of the optical communication device 1 will be explained, ignoring the loop route.

Let us consider a case where transmission is started from the optical communication device 1 of the B station.

The signal transmitted from the terminal device 2 of the B station is transmitted through the optical fiber 2
3, it is transmitted in both left and right directions.

The optical communication device 1 of the C station receives the signal of the B station, and transmits the pulse width regenerated signal to both the B and D stations.
Pass station A No. 3 to station D eight times.

Station D receives both the signal from the B station that bypasses the optical communication device 1 of the C station and the signal that is regenerated and relayed by the optical communication device 1 of the C station, and receives the pulse width regenerated signal. is transmitted both to the left and right of the F and D stations, and the C station signal is bypassed to the right of the D station.

Station A. Station E performs the same operations as station C.

The role of the pulse width regeneration circuit 22 in the optical communication device l is as follows:
When regeneratively relaying an optical signal to another station, the optical pulse signal sent from the own station is superimposed and relayed out of phase with the pass-through signal of the other station due to the response delay during regenerative relaying, and this repetition causes continuous lighting. In order to prevent communication from becoming impossible, the pulse width must be regenerated to a specified value at each regeneration.

Transmission and reception operations at station B will be explained using FIG. B
After starting transmission, the station receives a signal that is a combination of the signals returned from stations A, C, and E and the signals returned from stations D, F, and G. The transmission pulse width τ0 of station B is D, F, G
R Z (return to zeto) that continues for a time longer than the time when the rising edge of the pulse of the signal returned from the station is received and returns within the bit interval T.
Pulse is used.

The pulse width regeneration circuit 22 of the B station captures the rising edge of the composite signal and regenerates a pulse with a specified pulse width τ0.

Note that at station B, while terminal device 2 is transmitting, E/03
The intermediate fiber control circuit 21 is controlled by the terminal device 2 so that only signals from the terminal device 2 are input manually. D,F,
Stations further away than G also send signals back to station B, but the optical communication device 1 operates normally as long as the transmission (hereinafter referred to as pass-through) loss is greater than a specified value.

As a communication control method for a single-wire bidirectional bus, DDMA. }
- Kumbath, CSMA/CD system, etc. can be used.

The maximum value of the pass-through loss defined by the passing loss between the optical fiber connection terminal 18 and the optical fiber connection terminal 19 is O/E
Although it is defined by the minimum received optical level of 12 (0/E can output a signal of specified quality above this optical level), it will be further explained that there is a limit value for the minimum value of pass-through loss. O/E 1 2 generally ranges from the minimum received light level to the siren detection light level (below this light level, the O/E is guaranteed to be in a non-receiving state)
Malfunctions such as code errors occur with respect to received optical signals between the two. For received optical signals below the silence detection optical level, a silence output is output. Therefore, the pass-through loss of the optical communication device 1 needs to be set to a value that provides a margin between the minimum received light level and the maximum silence light level generated within the optical bus.

Next, the minimum received light level and maximum silence light level are calculated to clarify the specified value of pass-through loss.

Note that the maximum silence light level referred to here is the maximum value of optical signals transmitted exceeding the required number of pass-throughs k.

In FIG. 2, it is assumed that an infinite number of optical communication devices are connected to stations A, C, and E around station B.

Also, consider the light reception level when transmitting and receiving between two stations that are farthest apart within the required number of pass-throughs k.

When the pass-through loss of each station is α, the loss of the optical fiber connecting the optical communication devices of each station is angle, and the optical transmission level is Ptx, the minimum received optical level Prmin is given by equation (1).

Prmin = a' - 1"' - PLx
(1) The network can be maintained by pass-through in the event of a power outage of consecutive stations within the number k of pass-throughs.

The maximum silence level Psmax is given by equation (2).

Psmax=3a"'-11"'l'tx /
(1-a) (2) Margin Ma between the minimum received light level and the maximum siren light level generated within the optical bus
rg is determined by the ratio of the two, and is expressed by equation (3).

When Marg≧1 in equation (3), a margin can be provided in the silence level threshold setting in the O/E 12. From equation (3), equation (4) is derived as the pass-through loss condition that must be satisfied in order to have a silence level threshold setting margin.

α≦1/(3・toz) (4) Formula (4
) is a condition that does not depend on the pass-through number k.

FIG. 4 shows the relationship between the margin Marg between the minimum received light level and the maximum silence light level calculated from equation (4) and the pass-through loss α.

Figure 5 shows a configuration diagram of a thin optical fiber having the above-mentioned pass-through loss. Figure 5 shows the optical fiber connection terminal 18.1.
Core diameter than 9 optical fiber. Branching/insertion and pass-through are performed by bundling and connecting fibers with small cladding diameters. In FIG. 5, the thin fiber 18
By selecting the core diameter and cladding diameter of c, it is possible to obtain a pass-through loss that satisfies equation (4).

Note that the above equation (2) can be derived from the maximum received light level Prmax, which is the response light level that the originating station receives from all other stations N.

Prmax = 3 (1-a')Ptx/ (1-a
)≦3PLx / (1-a) (N-+oo)
(5) (Second Embodiment) In Figure 1, the optical communication device l is divided into three branches.
However, the configuration of the optical communication device 1 in the case of dividing into five optical fibers, for example, is as shown in FIG.

Equation (4) is the pass-through loss condition for the case where the branch is divided into three from station B, but in general, when the branch is divided into N branches, the pass-through loss condition is expressed as Equation (6). expressed. α≦1/(N-J2-1-1) (6
) As above, the minimum value of pass-through loss can be calculated using equation (6)
If selected under the conditions given by , it is possible to configure a network as shown in FIG. 2 using the optical communication device 1 and the terminal device 2.

In each of the above embodiments, the case where the network is configured in the form of a bus has been described, but the present invention is not limited to this, and the same effects can be obtained even if the network is configured in the shape of a tree or loop. be.

The operation when configured in a loop will be briefly explained. In Figure 2, the signal transmitted from station B is transmitted to station D and F.
The D station and the F station send signals to each other via the optical fiber 24. At the time when stations D and F receive each other's signals, station C.. Since the signal from station E is being received, the pulse width regeneration circuit 2l is not retriggered. With this operation, station F. Station D mutually terminates the signal of the other station. This termination operation allows the bus to be configured as a logically open state even if it is physically connected. Regarding disconnection, for example, if the signal does not reach the E station from the B station due to an optical fiber disconnection, the signal is automatically transmitted to the E station via the F station via the optical fiber 23. No special monitoring signal is required for the automatic disconnection recovery operation.

〔Effect of the invention〕

As explained above, according to the present invention, the optical communication equipment of each station in the network is provided with N optical fiber connection terminals, and two of the terminals allow optical signals to be directly passed through with a passing loss greater than a specified loss. All other terminals are connected to E/0 and O/E, and the configuration is configured so that the signal ε with a specified pulse width is reproduced and relayed in response to the rising edge of the O/E output, so it can be used not only as a bus type. Tree-type, loop-type, and mixed-type networks can be configured freely, and a large number of stations can be connected. There is no need for a station to transmit a disconnection monitoring signal, and optical fiber disconnections and stations can be detected without using optical switches. It is possible to construct an economical and highly reliable network that can maintain the network even in the event of a power outage.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the station used in the first embodiment of the present invention, Fig. 2 is a block diagram of the same embodiment, Fig. 3 is a waveform diagram showing the operation of the same embodiment, and Fig. 4 is the minimum received light. Relationship diagram between level, maximum silence light level margin, and pass-through loss, 5th
1 is a block diagram of a pass-through part of the station shown in FIG. 1, FIG. 6 is a block diagram of a station used in the second embodiment of the present invention, FIG. 7 is a block diagram of a conventional optical communication device, and FIG. FIG. 1 is a configuration diagram of a conventional optical communication network. In the figure, 1 is an optical communication device, 2 is a terminal device, 3 is an electro-optical converter, 12 is an opto-electric converter, 18, 19.20 are optical fiber connection terminals, 18a. 18b. 18c, 19a, 19b
, 20a, 20b are thin fibers, and 21 is medium! The control circuit 22 is a pulse width regeneration circuit. 25, 26 are optical fiber connection terminals, 25a, 25b. 26a. 26b is a thin optical fiber. Note that the same reference numerals in the drawings indicate the same or corresponding parts. Figure 1

Claims (1)

[Claims] (1) A single-line bidirectional communication/branch type optical communication network in which a plurality of stations are connected by an optical fiber with a loss l for the maximum connection distance between stations, and the station is equipped with the following components a to i. An optical communication network characterized by: a. Electro-optical converter. b. Photoelectric converter. c, first, second and third to Nth optical fiber connection terminals; d. Optical coupling means provided between the first, second and third to Nth optical fiber connection terminals and the electro-optic converter. e. Optical coupling means provided between the first, second and third to Nth optical fiber connection terminals and the opto-electrical converter. f, an optical coupling means provided between the first and second optical fiber connection terminals and having a passage loss of 1/(N·l+1) or more; g. Pulse width reproducing means that captures the rising edge of the output pulse signal of the opto-electric converter, regenerates a pulse signal with a specified pulse width length, and supplies the pulse signal to the electro-optic converter. h. means for receiving a signal required by the station via the pulse width regeneration means and transmitting a signal from the station via the electro-optical converter; i. Means for stopping the relay operation by the pulse width reproducing means during the transmission period of the station.