JPH01115237A - Optical fiber communication LAN - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for connecting nodes in an optical fiber communication LAN in which the outbound and return routes are the same route.

Conventional technology In general, loop networks represented by LAN etc.
As shown in FIG. 2, nodes are installed along the outer periphery, and the nodes are connected in cascade using, for example, optical fibers. Normally, it is configured with a single loop, but a loop is formed using a loopback function as a protection in the event of a failure (indicated by 8 points).

When constructing a loop network by installing nodes on a route E that connects a starting point and an ending point, such as on a railway or road, the third
As shown in the figure, optical fibers are connected in cascade from the starting point, node 1, to the ending point, node N, to form an outgoing path. In FIG. 3, it is assumed that the intervals between each node are equal to L. On the other hand, the return route connects the end point node N to the start point node 1, but if the distance between the start point and the end point is a long distance (several 10 to 10,100 km), a repeater is required on the way.

In optical fiber IS, the possible distance for non-repeater transmission is limited by the loss characteristics and band characteristics of the optical fiber.

For example, the optical fiber is a multimode fiber (GE-5
0), the transmission loss is approximately 1 (dB/km) when the wavelength used is 1.3 [μm] band, and the characteristics are as shown in Fig. 4. The fiber input power is -20 (dBll),
Assuming that the minimum light receiving level of the light receiving element is -40 [d-], the non-relay transmission distance is approximately 20 (kn+).

Next, the transmission band of the fiber F DlHz) is determined by the fiber band characteristic f (MHz-km) and the distance L (km
), it is expressed as F=fXL-" (MHz), where X is an index determined by the fiber, and is generally 0.6 to 0.8.

Band characteristic f = 600 (MHz-km), index x =
FIG. 5 shows the relationship between distance and transmission band when the angle is 0°7.

Problems to be Solved by the Invention Now, when a LAN is configured at 100 (Mbps), the maximum non-relay transmission distance is 12 (km) from FIG.

For example, if the distance between each node is limited to 6 (km) or less, a repeater will be required at every other node in the return loop from the end point to the start point.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a loop connection method that does not require a repeater in a return loop.

Means for Solving the Problems The present invention connects every other node in a cascade from the starting point node to the ending point (however, the ending point N and (N-1)
(the nodes connected adjacent to each other), and on the return route, starting from the end point node, nodes that are not connected on the outward route are connected in cascade to form a loop to return to the starting point.

Effect The present invention has the above-described configuration to connect the nodes to the outgoing system and 1ti.
A loop configuration that does not require repeaters can be realized by separating the lines into separate systems.

Example An embodiment of the present invention will be described with reference to FIG.

When starting point l and ending point N are located in a straight line and multiple nodes are installed on that line to construct a loop network using optical fibers, the interval between nodes should be L or less, and the interval between every other node should be 2L or less. Specifically, the transmission loss and band characteristics when using a multimode fiber (GI-50) and a wavelength band of 1.3 [μm] are shown in FIGS. 4 and 5, and will therefore be omitted. Now, assuming that L = 6 (km) or less and transmission band F = 100 (Mbps), odd-numbered (3, 5, 7
, . . ) can be connected in cascade, and even-numbered nodes (not connected on the outbound path) can be connected in cascade on the return journey from the end point N to the starting point 1.

Effects of the Invention The present invention connects odd-numbered nodes (3, 5, 7, etc.) in cascade on the outgoing route from the starting point l to the ending point N, and connects the even-numbered nodes (connected on the outgoing route) on the returning route from the ending point N to the starting point 1. By cascade-connecting the nodes (which were not installed), a repeater on the return route is not required, making it possible to simplify the system and reduce the cost.

[Brief explanation of the drawing]

Fig. 1 is a system block diagram of an optical fiber communication LAN according to an embodiment of the present invention, Figs. 2 and 3 are system block diagrams of a conventional optical fiber communication LAN, and Fig. 4 shows the loss characteristics of the optical fiber. The graph shown in FIG. 5 is a graph showing the band characteristics of the optical fiber. 1--N...φ node. Name of agent: Patent attorney Toshio Nakao Haka1 person No. 21!
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Claims (1)

[Claims] In a LAN in which N nodes (N≧4) including the start point and end point are connected in a loop with at least two optical fibers on a path (for example, on a straight line) connecting the start point and the end point, the start point The outbound route starting from a node and going to the destination point is connected in cascade to every other node (however, the nodes at the destination point N and (N-1) are connected adjacently), and the return route starts from the destination node and connects nodes that are not connected on the outbound route. Optical fiber communication L characterized in that it is configured such that it connects in cascade and returns to the starting point.
A.N.