JPH04319830A - Optical bypass system - Google Patents

Abstract

PURPOSE:To attain the correct transmission of an optical signal without attenuating the level of the optical signal even though plural adjacent nodes are continuously bypassed in a network. CONSTITUTION:The input optical signal received from an optical transmission line 11 of the upstream side is led by a 1st optical switch 12 to the reception terminal of a node end office device 15 of an optical loop type local area network as long as the device 15 is normal. Meanwhile the switc 12 outputs an input optical signal with bypass when the deivce 15 is nor normal. An optical amplifier 13 is added to amplify the bypassed optical signal of the switch 12. Then a 2nd optical switch 14 lends the optical signal transmitted from the device 15 to the line 11 of the downstream side when the device 15 is normal and then leads the bypassed optical signal amplified by the amplifier 13 to the line 11 of the downstream side when the device is not normal.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical bypass method for bypassing a transmitted optical signal when a node terminal equipment used in a node of an optical loop type local area network (LAN) is abnormal.

0002

2. Description of the Related Art In an optical loop type LAN, as shown in FIG. 3, a plurality of nodes 1 to 10 are connected in a loop, and communication is provided between terminal devices connected to a node terminal device of each node. It is something that Each of the nodes 1 to 10 is provided with a bypass function that disconnects the node terminal device from the loop and bypasses the transmitted optical signal when the node terminal device is abnormal (for example, the device input power is cut off).

As a conventional optical bypass system of this type, an optical bypass system in which a 2×2 optical switch 16 as shown in FIG. 2 is provided has been used. Node terminal equipment 1
5 is normal, the optical input signal from the optical fiber transmission line 11 passes through the optical switch 16 to the node terminal equipment 15.
The optical transmission signal of the node terminal device 15 is input to
The signal is output to the optical fiber transmission line 11 via the optical switch 16. On the other hand, when the node terminal equipment 15 is abnormal, the optical input signal from the optical fiber transmission line 11 is transferred to the optical switch 16.
It is bypassed as it is via the optical fiber transmission line 1
1 is output.

0004

[Problems to be Solved by the Invention] In the conventional optical bypass system described above, the adjacent node in FIG.
.about.6 are all in the bypass state, the optical output signal of the node terminal equipment 15 of node 10 is attenuated by the passage loss of the optical switch 16 each time it is bypassed at nodes 1 to 6, and the optical output signal of the node terminal of node 7 There is a problem in that the optical input signal level of the station device 15 drops considerably, making it impossible to receive the optical signal correctly.

[0005]

[Means for Solving the Problems] The optical bypass system of the present invention is such that when a node terminal device of an optical loop type local area network is normal, an input optical signal from an upstream optical transmission path is received by the node terminal device. a first optical switch that bypasses and outputs the input optical signal when there is an abnormality in the node terminal equipment; an optical amplifier that amplifies the bypass optical signal of the first optical switch; and an optical amplifier that amplifies the bypass optical signal of the first optical switch; When the device is normal, the transmitted optical signal from the node terminal device is guided to the downstream optical transmission path, and when the node terminal device is abnormal, the bypass optical signal amplified by the optical amplifier is guided to the downstream optical transmission path. and a second optical switch that leads to.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention. When the node terminal equipment 15 is normal, the optical input signal from the optical fiber transmission line 11 is transmitted to the 2×1 type optical switch 12.
The optical output signal of the node terminal device 15 is input to the node terminal device 15 via the 2×1 type optical switch 1.
4 and is output to the optical fiber transmission line 11. On the other hand, when the node terminal equipment 15 is abnormal, the optical input signal from the optical fiber transmission line 11 is outputted to the optical fiber transmission line 11 via the optical switch 12, the optical amplifier 13, and the optical switch 14. . At this time, the passage loss at the optical switches 12 and 14 is compensated by the amplification effect of the optical amplifier 13.

[0008]

As explained above, according to the present invention, even if a plurality of adjacent nodes in a network are in a bypass state in succession, the optical signal level can be transmitted without attenuation, and correct optical signal transmission can be carried out. can.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a block diagram of a conventional bypass method.

FIG. 3 is a block diagram of an optical loop type LAN to which the present invention and a conventional system are applied.

[Explanation of symbols]

1 to 10 nodes 11 Optical fiber transmission line 12, 14, 16 Optical switch 13 Optical amplifier 15 Node terminal equipment

Claims (1)

[Claims] Claim 1: When the node terminal equipment of an optical loop type local area network is normal, the input optical signal from the upstream optical transmission line is guided to the receiving end of the node terminal equipment, and when the node terminal equipment is abnormal, a first optical switch that sometimes bypasses and outputs the input optical signal; an optical amplifier that amplifies the bypass optical signal of the first optical switch; and a transmission from the node terminal device when the node terminal device is normal. a second optical switch that guides the optical signal to the downstream optical transmission line, and also guides the bypass optical signal amplified by the optical amplifier to the downstream optical transmission line when the node terminal equipment is abnormal. Optical bypass method is characterized by: