JPH088533B2 - Optical communication network - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a single-line bidirectional communication / branch type optical communication network using an optical fiber, and more particularly to this type of optical communication network having a relay function.

[Prior Art] FIG. 7 shows a block diagram of a conventional single-line two-way communication equipment as disclosed in, for example, Japanese Unexamined Patent Publication No. 56-761, "Data Highway Transmission Device".

In FIG. 7, 1 is an optical communication device, 2 is a terminal device (a combination of 1 and 2 is hereinafter referred to as a station), 3 is an electro-optical conversion device (hereinafter referred to as E / O), 4, 7, 8 and 11 are Lens 5 is an elastic coupler in the optical direction, 6 is a prism, 9 and 10 are optical fibers, and 12 is a photoelectric converter (hereinafter referred to as O / E).

The optical communication device 1 for single-wire bidirectional communication configured as described above operates as follows.

The signal transmitted from the terminal device 2 is electro-optically converted by the E / O3 and converted into a parallel beam by the lens 4, then passes through the directional coupler 5 and is branched left and right by the 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 the left and right directions. The signal transmitted from the right direction through the optical fiber 10 becomes a parallel beam in the lens 8, and then a part thereof passes in the left direction, is coupled to the optical fiber 9 by the lens 7, and is transmitted in the left direction. 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
Binds to O / E12. Similarly, the optical signal transmitted from the left side of the optical fiber 9 is also transmitted to the optical fiber 10 side.
It binds to O / E12. The O / E12 output is output to the terminal device 2.

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

In FIG. 8, 13 is a disconnection detection automatic restoration device, 14 is an optical fiber, 15 is an optical switch, 16 is an optical branching device, and 17 is a signal monitoring circuit.

The network is configured by connecting the optical communication devices 1 of stations A, B, C, D, and E and the disconnection detection automatic restoration device 13 with an optical fiber 14 in a loop. The access method is TDMA (time div
Consider the case of using the ision multple access) method. When there is no disconnection in the loop, the loop is opened by the optical switch 15 in the disconnection detection automatic restoration device 13. The optical signal transmitted from the optical communication device 1 of station A goes around the loop in both directions. The optical signal that circulates in the clockwise direction circulates in the loop while being optically branched in the optical communication device 1 of each station and reaches the disconnection detection automatic restoration device 13, and some signals are output from the optical splitter 16 to the O / E 12 to detect the disconnection. And the others are discarded from the bus in the optical switch 15. The optical signal that circulates counterclockwise circulates in a loop while being optically branched in the optical communication device 1 of station A, reaches the disconnection detection automatic restoration device 13, and is discarded from the bus by the optical switch 15. The TDMA system requires a reference station for transmitting a frame signal called a reference burst. In the conventional example, station A is the reference station. Each station transmits and receives using a signal transmission time slot determined with reference to the transmission signal of station A. In the disconnection detection automatic restoration device 13, the O / E 12 output is input to the signal monitoring circuit 17.
The signal monitoring circuit 17 is a reference station A included in the received signal.
Disconnection is detected by the presence or absence of station signal. The signal monitoring circuit 17 closes the optical switch 15 at the time of detecting the disconnection and sets the disconnected portion as an open point to reconfigure the network. However, the network cannot be reconfigured for disconnection at two or more locations.

As an access method, CSMA / CD (carrier sense mut
Other methods such as iple access with collision detection) and a token bus can be applied, but in order to implement the countermeasure against the disconnection, it is necessary to devise such that the signal for monitoring the disconnection state is transmitted from the A station.

Since the loop network of FIG. 8 is added / dropped by the passive branch circuit, high output is required for E / O3 and high sensitivity is required for O / E12 of the optical communication device 1. However, actually, the number of connectable stations is 8 to 20.

[Problems to be Solved by the Invention]

Since the conventional network is configured as described above, it is difficult to connect many stations in the loop, the optical communication device is expensive, and one disconnection is allowed, but more disconnection is possible. Then, there is a problem that the network does not operate, and even if the access method does not require the reference station, the station becomes necessary to transmit the disconnection monitoring signal and the network becomes complicated.

The present invention has been made under such circumstances, and a station that can connect a large number of stations and can operate regardless of an optical fiber disconnection or power failure of a station and that transmits a disconnection supervisory signal is provided. It is intended to provide an optical communication network that does not require it.

[Means for solving the problem]

In order to achieve the above object, in the present invention, an optical communication network is configured as in (1) below.

(1) A single-line bidirectional communication / branch type optical communication network in which a plurality of stations are connected by an optical fiber, wherein the station includes the following components a to i. network.

a. electro-optical converter.

b. Optoelectric converter.

c. N (N is multiple) optical fiber connection terminals.

d. The N optical coupling means provided between the optical fiber connection terminals and the electro-optical converter.

e. Optical coupling means provided between the N optical fiber connection terminals and the photoelectric converter.

f. Optical coupling means having a passage loss of 1 / (N · l + 1) or more provided between two of the N optical fiber connection terminals. (L
Is a predetermined value determined as the loss of the optical fiber connecting the plurality of stations) g. Recognizing the rising edge of the output pulse signal of the opto-electric converter, reproducing a pulse signal of a specified pulse width length, and sending it to the electro-optical converter. Supplying means for pulse width regeneration.

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

i. A means for stopping the relay operation by the pulse width reproduction means during the transmission period of the station.

[Action]

With the configuration of (1), the communication function can be maintained regardless of a part of the optical fiber disconnection and the power supply of the station by applying to various types of networks, and communication can be performed without requiring a disconnection monitoring signal.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to Examples.

FIG. 1 shows a block diagram of a station used in the "optical communication network" according to the first embodiment of the present invention. In the figure, 1
Is an optical communication device, 2 is a terminal device, 3 is E / O, 12 is O / E, 18,1
9,20 are first, second and third optical fiber connection terminals, 18a, 18
Reference numerals b, 18c, 19a, 19b, 20a and 20b denote thin fiber (optical coupling means), 21 a relay control circuit (means for stopping the relay operation), and 22 a pulse width regeneration circuit.

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

In FIG. 1, three optical fiber connection terminals 18, 19, 20
A bidirectional optical signal input / output from the optical communication device 1 is branched in the optical communication device 1, passes through E / O3 and O / E12, and is coupled to the opposing optical fiber. That is, the optical fiber connecting terminal 18 is coupled to the E / O3, O / E12 and the optical fiber connecting terminal 19 which passes through and is opposed to each other by the respective thin fiber 18a, 18b, 18c. The optical fiber connection terminal 19 is E / O3, O / by each thin fiber 19a, 19b, 18c.
It is coupled to E12 and the optical fiber connection terminal 18 passing through and opposite. The optical fiber connection terminal 20 is
It is bound to E / O3 and O / E12 by a, 20b.

The E / O 3 converts the electric signal output from the relay control circuit 21 into an optical signal and outputs the optical signal to the optical fiber connection terminals 18, 19, 20.

The O / E 12 photoelectrically converts the optical signals received from the optical fiber connection terminals 18, 19, 20 and outputs them to the pulse width reproduction circuit 22.
The output signal of the pulse width reproduction circuit 22 is output to the relay control circuit 21 and the terminal device 2.

The optical fiber 18c is an optical coupling unit that bidirectionally couples the optical signals transmitted bidirectionally through the optical fiber connection terminal 18 and the optical fiber connection terminal 19 and has a prescribed passage loss described later.

The pulse width reproduction circuit 22 catches the rising edge of the O / E12 output signal, reproduces it into a specified pulse width, and outputs it.

The relay control circuit 21 includes a terminal device 2 and a pulse width reproduction circuit 22.
Signal is input from the terminal device 2 during the transmission period of the station.
Of the pulse width regeneration circuit 22 during the non-transmission period.
Supply to E / O3.

FIG. 2 shows the "optical communication network" of the first embodiment.
Shows the configuration of. As shown in the figure, station B is used as a branch point for A and G
It is a network in which three buses are wired in three directions: station, C, D station, E, F station. In the figure, A, B, C, D, E, F and G stations are optical communication devices having the same configuration. However, the optical fiber connection terminals 20 of the A, G, C, and E stations are unused. Further, the optical fiber connection terminal 18 and the optical fiber connection terminal 19 of the optical communication device 1 of the B, C, and D stations are connected by the optical fiber 23, and the optical fiber connection terminal 20 and the optical fiber connection terminal of the B station and the E station are connected. 18 is connected by an optical fiber 24, the optical fiber connection terminal 19 of the E station and the F station and the optical fiber connection terminal 18 are connected by an optical fiber 23, and the optical fiber connection terminal 20 of the F station and the D station is connected by an optical fiber. They are connected by a fiber 24, and B, E, F, D, and C stations form a loop.

First, the transmission / reception / relay operation of the optical communication apparatus 1 will be described, ignoring the loop path.

Consider a case where transmission is started from the optical communication device 1 of station B. The signal transmitted from the terminal device 2 of station B is transmitted in both left and right directions by the optical fiber 23.

In the optical communication device 1 of the C station, the signal of the B station is received, the pulse width reproduced signal is transmitted to both the B and D stations, and
Bypass (pass through) the station signal to the D station.

In the D station, the optical communication device 1 of the C station among the signals from the B station
Both the signal bypassed with the signal and the signal regenerated and relayed by the optical communication device 1 of the C station are received, and the pulse width regenerated signal is transmitted to both the left and right directions of the F station and the D station.
Bypasses the station signal to the right of station D.

 Station A and station E operate in the same manner as station C.

The role of the pulse width reproduction circuit 22 in the optical communication device 1 is:
When an optical signal is regenerated and relayed to another station, the optical pulse signal sent from the local station is superposed and relayed in a phase-shifted state with the pass-through signal of the other station due to the response delay at the time of regenerative relay, and is continuously lit by this repetition. This is to reproduce the pulse width to a specified value at each reproduction in order to prevent a situation and communication failure.

The transmission / reception operation in station B will be described with reference to FIG.
Station B receives a signal that is a combination of the signals returned from stations A, C, and E after the start of transmission and the signals returned from stations D, F, and G. The transmission pulse width τo of station B is the RZ (return to zeto) pulse that continues for more than the time when the pulse rising of the signal returned from stations D, F, G is received and returns within bit interval T. used. The pulse width reproduction circuit 22 of the B station captures the rising edge of the combined signal and reproduces the pulse having the specified pulse width τo. However, in the B station, the terminal device 2 is transmitting and the E / O. Relay control circuit so that only signals from device 2 are input
Since 21 is controlled by the terminal device 2, it is not retransmitted by the combined signal. Although the D, F, G stations bypass the distant stations and the stations on the way and are delayed significantly, the signals are sent to the B station. However, if the passing loss of the optical communication device 1 (hereinafter referred to as pass-through) is more than the specified value. For example, the level of signals from these stations is below the receivable threshold value of station B (corresponding to the "silence detection light level" described later), so that the pulse width reproduction circuit 22 of station B should operate with this signal. There is no.

In this way, station B does not retransmit again based on the transmission from another station that has received the transmission from station B.

The stations other than the B station receive the signal from the B station as described above and transmit, but in this case also, similarly to the B station, the station does not receive the signal from another station and retransmit. This will be described by specifying it as one station (called own station).

Upon receiving the signal from the B station, the pulse width reproducing circuit 22 of its own station operates to transmit the signal having the pulse width τO. Although the local station receives a signal from another station that receives and transmits this signal, the rising edge of this received signal is within the transmission period of its own station, similar to station B. The station pulse width regeneration circuit 22 will not operate and will not be retransmitted. A signal that is far behind from your own station and passes through a station in the middle and is greatly delayed is sent to your own station, but since the level of this signal is below the threshold of receivability of your own station, this Pulse width regeneration circuit of own station based on signal
22 works and never resends.

In this way, each station transmits a pulse signal with a specified pulse width, and does not retransmit by receiving a signal from another station that receives and transmits this pulse signal. The signal is also limited to the specified pulse width, and the signal from other stations that is delayed greatly is less than the threshold of receivability of each station, that is, it corresponds to the extinguished state. Absent.

TDMA, token bus, CSMA / CD method, etc. can be used as the communication control method of the single line bidirectional bus.

The maximum value of the pass-through loss defined by the pass loss of the optical fiber connection terminal 18 and the optical fiber connection terminal 19 is the minimum received optical level of the O / E12 (O / E outputs a signal of specified quality above this optical level. However, the minimum value of pass-through loss has a limit value. O / E12 is generally a code error for the received optical signal between the minimum received optical level and the silence detection optical level (guaranteeing that the O / E is in the non-reception state below this optical level). Malfunction occurs. It does not respond to the received optical signal below the silence detection optical level, is in a non-reception state, and does not output a signal to the pulse width reproduction circuit 22. Therefore, the pass-through loss of the optical communication device 1 must be set to a value that allows a margin between the minimum received light level and the maximum silence light level generated in the optical bus.

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

The maximum silence light level referred to here is the maximum value of the optical signal transmitted over the required pass-through number k.

In FIG. 2, it is assumed that optical communication devices are connected indefinitely in the directions of stations A, C and E centering on station B. Further, let us consider the light receiving level when transmitting and receiving between the two stations that are farthest apart from each other within the required pass-through number 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 1, and the optical transmission level is Ptx, the minimum received light level Prmin is given by the equation (1).

For ^{Prmin = α k · l k +} 1 · Ptx (1) power off station continuous within the pass-through number k, it is possible to hold the network by pass-through.

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

Psmax = 3α ^{k + 2} · 1 ^{K + 2} · Ptx / (1-α) (2) Marg Marg between the minimum received light level and the maximum silence light level generated in the optical bus is calculated by the ratio of both. And is represented by equation (3).

When Marg ≧ 1 in the equation (3), it is possible to have a margin in setting the silence level threshold value in O / E12. From equation (3), equation (4) is derived as a pass-through loss condition that must be satisfied in order to have a silens level threshold setting margin.

α ≦ 1 / (3 · l + 1) (4) Expression (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 silenced light level calculated from the equation (4) and the pass-through loss α.

FIG. 5 shows a configuration diagram of a thin optical fiber having the pass-through loss. FIG. 5 shows the optical fiber connection terminals 18 and 19
The optical fiber has a smaller core diameter and clad diameter than the optical fiber, and is connected by bundling and inserting and passing through. In FIG. 5, the pass-through loss satisfying the expression (4) can be obtained by selecting the core diameter and the clad diameter of the thin fiber 18c.

The equation (2) can be derived from the maximum received light level Prmax, which is the response light level received by the transmitting station from all the other stations N.

Prmax = 3 (1−α ^N ) Ptx / (1−α) ≦ 3Ptx / (1−α) (N → ∞) (5) (Second embodiment) In FIG. 1, the branch is divided into three. The configuration of the optical communication device 1 in the case where the optical communication device 1 is present is shown, but the configuration of the optical communication device 1 in the case of dividing the optical communication device 1 into, for example, 5 is as shown in FIG.

Expression (4) is a pass-through loss condition for the case where the branch from the B station is divided into three branches. Generally, when the branch is divided into N branches, the pass-through loss condition is expressed by the expression (6). .

α ≦ 1 / (N · l + 1) (6) As described above, the minimum value of the pass-through loss can be calculated by the equation (6).
If selected under the condition given in, the network as shown in FIG. 2 can be configured 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 bus type has been described, but the present invention is not limited to this, and even if the network is configured in a tree shape or a loop shape, the same operational effect can be obtained. is there.

The operation in the case of the loop configuration will be described once. In FIG. 2, the signal transmitted from the B station reaches the D station and the F station, and the D station and the F station mutually transmit the signals via the optical fiber 24. The stations D and F have received the signals of the stations C and E at the time when they receive the signals of the other station, and the pulse width reproduction circuit 21 is not retriggered. By this operation, the F station and the D station terminate the signal of the partner station with each other. By this terminating operation, even if it is in a physically connected state, it becomes a logically opened state and the bus can be configured.

As for the disconnection, for example, when the signal does not reach the station E from the station B due to the disconnection of the optical fiber, the signal is automatically transmitted to the station E via the optical fiber 23 via the station F. No special monitoring signal is required for the automatic disconnection recovery operation.

〔The invention's effect〕

As described above, according to the present invention, the optical communication device of each station in the network is provided with N optical fiber connection terminals, of which two terminals directly pass the optical signal with a passage loss equal to or more than the specified loss. All other terminals were connected to E / O and O / E, and it was configured to reproduce and relay a signal with a specified pulse width for the rising edge of the O / E output.
Not only bus type but also tree type, loop type and mixed type networks can be freely configured, many stations can be connected, no station for transmitting disconnection supervisory signal is required, and optical switch is not used. An economical and highly reliable network can be configured such that the network can be maintained even if the optical fiber is disconnected or the station power is cut off.

[Brief description of drawings]

FIG. 1 is a block diagram of a 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. Relationship between level and maximum silence light level margin and pass-through loss, No. 5
1 is a block diagram of the pass-through section of the station shown in FIG. 1, FIG. 6 is a block diagram of the station used in the second embodiment of the present invention, FIG. 7 is a block diagram of a conventional optical communication apparatus, and FIG. 2 is a configuration diagram of the optical communication network of FIG. 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 and 20 are optical fiber connection terminals, and 18a, 18b, 18c, 19a, 19b, 20a. , 20b is a thin fiber, 21
Is a relay control circuit, and 22 is a pulse width reproduction circuit. 25,26
Is an optical fiber connection terminal, and 25a, 25b, 26a and 26b are fine line optical fibers. The same reference numerals in the drawings denote the same or corresponding parts.

Claims (1)

[Claims] 1. A single-wire bidirectional communication / branch type optical communication network in which a plurality of stations are connected by an optical fiber, wherein the station comprises the following components a to i. network. a. electro-optical converter. b. Optoelectric converter. cN (N is multiple) optical fiber connection terminals. d. Optical coupling means provided between the N optical fiber connection terminals and the electro-optical converter. e. Optical coupling means provided between the N optical fiber connection terminals and the photoelectric converter. f. Optical coupling means having a passage loss of 1 / (N · l + 1) or more provided between two of the N optical fiber connection terminals. (L
Is a predetermined value determined as the loss of the optical fiber connecting the plurality of stations) g. Recognizing the rising edge of the output pulse signal of the opto-electric converter, reproducing a pulse signal of a specified pulse width length, and sending it to the electro-optical converter. Supplying means for pulse width regeneration. h. A means for receiving a signal required by the station via the pulse width reproducing means and transmitting a signal from the station via the electro-optical converter. i. A means for stopping the relay operation by the pulse width reproducing means during the transmission period of the station.