JPS63100833A - Optical communication system - Google Patents

Abstract

PURPOSE:To improve the data transmission speed by selecting a fiber between a reception coupler and a transmission coupler to a prescribed length. CONSTITUTION:The time required for the propagation in an optical communication system having a length (l) between a branch point 19 and a summing point 20 of each terminal station is expressed as l/v, where (v) is the signal transmission speed in the optical fiber 12. On the other hand, the signal processing time from the branch point 19 till the terminal station then the summing point 20 as an output is tau. In selecting the length (l) as l=v.tau since the data is sent from the transmission section of the terminal station simultaneously with the passing delimiter of being propagated through the optical fiber 12 at the summing point, that is, a bent part 35 without being branched at the branch point 19, that is, a bent part 34, no space is caused in the data field and the slot is utilized effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical communication system using an optical fiber as a transmission medium. The present invention relates to an optical communication system in which an optical transmission path is coupled to the terminal station and bypasses between a receiving section and a transmitting section of a terminal station.

2. Description of the Related Art Conventionally, in an optical communication system in which a plurality of terminal stations are coupled to an optical fiber, an optical signal propagating on the optical fiber is first converted into an electrical signal at the terminal station, and then the central processing unit in the terminal station converts the optical signal to an electrical signal. (hereinafter abbreviated as CPLI), the electrical signal is converted into an optical signal again, and the optical signal is then transmitted over an optical fiber. In such an optical communication system, when a failure occurs in one terminal station, the effect spreads to the entire system, and eventually the entire system stops functioning. Therefore, each terminal station must be equipped with an optical switch to bypass the optical signal when a failure occurs, and in that case, the system must have the ability to detect a failure at the terminal station and drive the optical switch. Inevitably, a complex structure had to be adopted.

On the other hand, a system using a coupler has been proposed as a simple optical communication system that does not require an optical switch. Figure 3 shows
An example of such an optical communication system is shown below. The optical fiber 2 extending from the transmitting section of the control terminal station 1 extends in a loop shape and is coupled to the receiving section of the control terminal station 1 . The optical fiber 2 has terminal stations 3A to 3C connected to a receiving branch coupler 4.
They are coupled via A to 4C and transmission branch couplers 5A to 5C, respectively. And the receiving branch coupler 4A~
One of the outputs of 4C is sent to the receivers 6A to 6A of each terminal station 3A to 3C.
6C, and one of the inputs of the transmission branch couplers 5A to 5C is coupled to the outputs of the transmission units 78 to 7C of the terminal stations 3A to 3C. Further, the outputs of the receiving sections 6A to 6C are C
Connected to the inputs of PU8A to PU8C, respectively, and transmitting section 7A
The human power of ~7C is connected to the output of CPU8A~8C, respectively.

In such an optical communication system, when an optical signal propagated through an optical fiber enters a terminal station, it is first branched into two by a receiving coupler, one of which propagates through the optical fiber as it is, and the other which is converted into an electrical signal by the receiving section. After being converted into an optical signal and processed by the CPU, it is again converted into an optical signal at the transmitting section, and then merged into an optical fiber at a transmitting coupler.

In such an optical communication system, even if a failure occurs in one terminal station, there is an optical signal that propagates as it is on the optical fiber without reaching the receiving section of that terminal station, so an optical switch for bypass is required. This has the advantage that the system configuration is relatively simple.

Problems to be Solved by the Invention However, on the other hand, the optical communication system shown in FIG.
There was a problem that the slots could not be used effectively.

The problem will be explained below using FIG. 4.

FIG. 4 is an example of a frame format used in an optical communication system. The illustrated frame is composed of a preamble, an address, a delimiter, a data field, and a delimiter, and a time slot is located between the two delimiters with the data field in between.

Such an optical communication system operates as follows. First, the terminal station receives the preamble and synchronizes the clocks of the receiving circuits. Next, the address is received and it is determined whether or not the destination of the data field prepared later is the local station. If the assignment destination is your own station,
After receiving the following delimiter, data transmission begins.

However, at the terminal station, from the time the delimiter is received to the start of data transmission, there is conversion from an optical signal to an electrical signal, processing by the CPU, and conversion from an electrical signal to an optical signal.
．． A signal processing delay time of 1 to 1 μsec occurs. As a result, there is a blank space in the data field, which has the disadvantage that slots with limited time widths cannot be used effectively.

Means for Solving the Problems According to the present invention, in an optical communication system in which a plurality of terminal stations are coupled to an optical fiber serving as a transmission medium, the receiving section of the terminal station receives signals via a receiving coupler. The transmitting section of the terminal station is coupled to the optical fiber and detects a part of the optical signal propagating through the optical fiber, and the transmitting section of the terminal station is coupled to the optical fiber via the transmitting coupler and detects a part of the optical signal propagating through the optical fiber. The optical signal emitted from the terminal is injected into the optical fiber, and the length l of the optical fiber between the receiving coupler and the transmitting coupler of the same terminal station is For the resulting signal processing delay time and for the signal transmission speed V in the optical fiber,! An optical communication system is provided that is characterized by the relationship: =V·τ.

Operation The operation of the above-described optical communication system according to the present invention will be explained with reference to the frame format shown in FIG.

After the receiving coupler branches and the delimiter is input to the receiving section of the terminal station, until the data is sent from the transmitting section,
A signal processing delay time τ occurs, but on the other hand, if the length of the optical fiber from the branch point of the receiving coupler to the confluence of the transmitting coupler is l, and the signal transmission speed of the optical fiber is After passing through and before passing through the confluence,
It takes a time of 12/V. Therefore, as in the present invention, β
When set to =■・τ, at the transmitting coupler, that is, the confluence of the optical signal propagating through the optical fiber and the optical signal from the transmitting section of the terminal station, the signal is not sent to the terminal station by the receiving coupler, but remains as it is. Since the data is transmitted from the transmitter at the same time as it passes through the delimiter after propagating through the optical fiber, there are no blank spaces in the data field, and slots can be used effectively.

Thus, in the optical communication system according to the present invention described above,
This solves the conventional problem of creating blank spaces in data fields and not being able to use slots effectively.

Furthermore, it goes without saying that in the optical communication system of the present invention, there is no need to prepare an optical switch in case a failure occurs at a terminal station.

Embodiments Hereinafter, embodiments of an optical communication system according to the present invention will be described with reference to the accompanying drawings.

FIG. 1(a) illustrates an embodiment of an optical communication system according to the present invention. The illustrated optical communication system includes a control terminal station 11 and a plurality of terminal stations 13A to 13C. One optical fiber 12 extending from the transmitting section of the control terminal station 11 extends in a loop shape and is coupled to the receiving section of the control terminal station 1, and the terminal stations 13A to 13C are coupled to the optical fiber 12. has been done. Therefore, after being transmitted from the control terminal station 11, the optical signal propagates through the optical fiber 12 in the direction of the arrow in the figure while being processed by the terminal stations 13A to 13C, and returns to the control terminal station 11.

FIGS. 1A and 1B are enlarged views of the vicinity of the terminal station 13A in FIG. One of the outputs of the receiving branch coupler 14 is connected to the receiving section 1 of the terminal station 13A.
6, and one of the inputs of the transmission branch coupler 15 is
It is coupled to the output of the transmitter 17 of the terminal station 13A. Further, the outputs of the receiving section 16 are respectively connected to the inputs of the CPU 18, and the human power of the transmitting section 17 is respectively connected to the outputs of the CPU 18.

For convenience, the branch point of the optical signal within the receiving coupler 14 is indicated by reference number 19, and the confluence point of the optical signal within the transmitting coupler 15 is indicated by reference number 20. And turning point 19
Optical fiber 1 between and confluence point 20? length! , terminal 1
If the signal processing delay time in step 3 is τ, and the signal transmission speed in the optical fiber 12 is V, then 1=v・τ...(
1) The length β of the optical fiber 12 between the branch point 19 and the confluence point 20 is set so as to satisfy the following relationship.

FIG. 2 is an example of a receiving coupler and a transmitting coupler used in the optical communication system of the present invention. The optical fiber 12 is bent at a constant curvature to provide bent portions 34 and 35 for each terminal station. A light receiving element 37 of the receiving section is coupled to the bent portion 34 via a transparent block 36 having a shape complementary to the bent portion and having a refractive index similar to that of the optical fiber. Similarly, a light emitting element 39 of the transmitting section is coupled to the bent portion 35 via a transparent block 38 having a shape complementary to the bent portion and having a refractive index similar to that of the optical fiber.

Since the bent portion 34 is bent at a constant curvature, one of the optical signals propagated through the optical fiber 12 leaks out of the fiber, enters the light receiving element 37 via the block 36, and is detected. Furthermore, since the bent portion 35 is also bent at a constant curvature, the optical signal from the light emitting element 39 is injected into the optical fiber 12 via the block 38. That is, the bent portion 3
4.35 are a receiving coupler and a transmitting coupler, respectively. Here, the length of the optical fiber between the bent portions 34 and 35 is set to the length defined by the above equation (1).

In the optical communication system as described above, the time required for propagation through the optical communication system of length l between the branch point 19 and the confluence point 20 of each terminal station is j7/v. On the other hand, branch point 19
Since the signal processing delay time at the terminal station from input to the terminal station to output to the confluence point 20 is τ, the above formula [
1], when β=V·τ is set, the optical fiber propagates through the optical fiber 12 as it is at the confluence point 20, that is, the bending part 35 in FIG. 2, without being branched at the branching point 19, that is, the bending part 34 in FIG. Since data is transmitted from the transmitting section of the terminal station at the same time as the primic passes, there are no blank spaces in the data field, and slots can be used effectively.

In this way, the signal processing delay time that occurs at the terminal station is
Since compensation is provided by the optical fiber between the branching point of the receiving coupler and the confluence point of the transmitting coupler, the same effect can be obtained even if a frame structure other than that shown in FIG. 2 is used in the optical communication system described above. can.

In addition, as the receiving coupler and the transmitting coupler, it is also possible to use an optical fiber coupler, a coupler formed of an optical waveguide, etc., in addition to the structure illustrated in FIG. The effects of the present invention can be achieved by setting the length of the optical fiber between the two to the length defined by equation (1).

As described in detail, the optical communication system of the present invention compensates for the signal processing delay time by simply setting the fiber between the receiving coupler and the transmitting coupler to a predetermined length. Since the slots can be used effectively, it is useful for substantially increasing the data transmission speed.

Furthermore, since the two signals branched by the receiving coupler are synchronized at the merging point, it is possible to determine whether the terminal station is receiving not only the data, but also the preamble, address delimiter, and signals received by other stations. regenerates and amplifies all the signals
It is also possible to send. In other words, this eliminates the restriction on the number of connectable terminal stations due to coupler loss, which was inevitable in conventional optical communication systems using couplers, and greatly contributes to the spread of optical communication.

[Brief explanation of the drawing]

FIG. 1(a) is a diagram showing an embodiment of the optical communication system of the present invention, FIG. 1(b) is an enlarged view of the vicinity of the terminal station in FIG. 1(a), and FIG. 2 is a diagram showing an embodiment of the optical communication system of the present invention. Figure 3 is a diagram showing an example of a conventional optical communication system having multiple terminal stations; Figure 4 is a frame used in the optical communication system. It is a figure showing an example of composition. (Main reference numbers) 1.11...Control terminal station, 2.12...Optical fiber, 4A, 4B, 4C, 14...Receiving coupler, 5A, 5B
, 5C115... Transmission coupler, 6A, 6B, 6C, 1
6. Receiving section, ? A, 7B, 7C, 17... Transmitter, 8A, 8B, 8C, 18... CPU 19... Branch point, 20... Merging point, 34. 35... Bend part, 37... Light receiving element, 39...・Light emitting element

Claims (5)

[Claims] (1) In an optical communication system in which a plurality of terminal stations are coupled to an optical fiber serving as a transmission medium, the receiving section of the terminal station is coupled to the optical fiber via a receiving coupler and propagates through the optical fiber. The transmitting section of the terminal station is configured to detect a part of the optical signal, and the transmitting section of the terminal station is coupled to the optical fiber via the transmitting coupler and injects the optical signal emitted from the transmitting section of the terminal station into the optical fiber. The length l of the optical fiber between the receiving coupler and the transmitting coupler of the same terminal station is determined by the signal processing delay time occurring within the terminal station, and the length l of the optical fiber between the receiving coupler and the transmitting coupler of the same terminal station. For signal transmission speed, l
An optical communication system characterized by a relationship of =v·τ. (2) The optical communication system according to claim 1, wherein the receiving coupler is configured to bend an optical fiber and detect a part of the optical signal from the bent portion. (3) The optical communication system according to claim 1, wherein the transmission coupler is configured to bend an optical fiber and inject an optical signal into the bent portion. (4) The optical communication system according to claim 1, wherein the receiving coupler and the transmitting coupler are optical fiber couplers. (5) The optical communication system according to claim 1, wherein the receiving coupler and the transmitting coupler are formed of optical waveguides.