JPH04343331A - Optical amplifying device - Google Patents

Abstract

PURPOSE:To execute the fault detection and the operation check by using light (back scatter) in the reverse direction against a signal light even in an optical transmission system having an isolator by providing a bypass in the isolator. CONSTITUTION:In the optical amplifying device constituted by inserting an optical amplifier 1 and an isolator 2 for preventing an oscillation into an optical waveguide 3, a bypass device 4 is provided so that a back scatter of the optical waveguide 3 does not pass through the isolator 2. That is, a through circuit 5 is provided in parallel to the isolator 2, and a switch SW is provided in the through circuit 5, and when the switch SW is turned off, a signal light passes through the isolator 2 and is subjected to optical transmission, and when the switch SW is turned on, the back scatter bypasses the isolator 2 and transmitted to an input terminal of the optical waveguide 5. Accordingly, the back scatter is not subjected to attenuation of the isolator 2.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical amplification device using a fiber amplifier, a laser amplifier, etc., which exhibits an optical amplification effect by excitation of light.

0002

2. Description of the Related Art In recent years, research has been actively conducted on optical amplification devices that utilize the optical amplification effect of fluorescent substances such as rare earth elements mixed into the core of silica-based optical fibers during optical excitation. As an optical amplification device using a rare earth element-doped optical waveguide, an Er-doped quartz-based optical fiber is used to
Optical amplification in the 5 μm band has been confirmed. Such an optical amplification device basically has a configuration as shown in Fig. 3, and includes a pumping light source A for optical pumping, a multiplexer B for combining signal light and pumping light, and a rare earth element, etc. and a fiber amplifier C mixed with a fluorescent substance. In order to obtain high gain with such an optical amplification device, it is necessary to prevent unstable oscillation due to light reflection. However, when this optical amplification device is incorporated into an optical transmission system, connection points are created by connecting optical transmission lines to each other or connecting optical equipment to the optical transmission lines. The presence of this connection point causes misalignment and reflection of light, making the operation of the optical transmission system unstable. Conventionally, in order to prevent this reflection, it has been common to insert an optical isolator E at one or both ends of the optical transmission line D, as shown in FIGS. 3 and 4. The optical amplifier shown in FIG. 4 uses a laser amplifier F instead of the fiber type amplifier C shown in FIG.

0003

[Problem to be solved by the invention] However, optical isolators
The amount of attenuation for light in the opposite direction of data E is usually 20 to 60 db.
Therefore, when optical isolator E is inserted into an optical transmission system, optical transmission from the opposite direction becomes impossible. Backscattered light or backreflected light of optical transmission line D is used to detect failure points in optical transmission systems or check the operation of the same system.
It is common to measure backscatter. This measurement method is commonly known as OTDR (Optical Time
This is called the Domain Reflection method), in which an optical pulse is sent out from the input end of the optical transmission line D, and the time change in backscatter generated by it is measured at the same input end to identify failure points and defects in the optical transmission system. This is a method of measuring the position etc. However, when isolator E is inserted in series with fiber amplifier C as shown in Figures 3 and 4, backscatter is reduced by 20 to 60 db due to isolator E.
is attenuated, making it difficult for the signal to be transmitted to the input end of the optical waveguide D. For this reason, when the isolator E is inserted, it becomes difficult to perform various measurements, detect a failure point in the optical transmission system, check the operation of the system, monitor the system, etc. using backscatter.

0004

[Object of the Invention] An object of the present invention is that even in an optical transmission system in which an optical isolator is inserted, backscatter can be used to detect failure points in the optical transmission system, check the operation of the system, etc. The object of the present invention is to realize an optical amplifying device as described above.

[0005]

[Means for Solving the Problems] As shown in FIGS. 1 and 2, the optical amplifying device of the present invention is a fiber-type amplifier that obtains gain by stimulated emission of a fluorescent substance such as a rare earth element mixed into the core. , an optical amplifier 1 such as a laser amplifier, an optical isolator 2 for preventing oscillation, etc. are inserted into an optical waveguide 3. A detour device 4 is provided to prevent light (backscatter) from passing through the optical isolator 2.

[0006]

[Function] In the optical amplification device of the present invention, the optical waveguide 3 is provided with the detour device 4 that prevents backscatter from passing through the optical isolator 2. passes through the detour device 4 to the optical isolator.
It is not affected by the attenuation of data 2. Therefore, even in an optical transmission system provided with the optical isolator 2, backscatter can be used to detect a failure point in the optical transmission system, check the operation of the system, etc.

[0007]

Embodiments FIGS. 1 and 2 show various embodiments of the optical amplification device of the present invention. In these figures, 1 is an optical amplifier such as a fiber amplifier or a laser amplifier, 2 is an optical isolator inserted into the optical waveguide 3 to prevent unstable oscillation,
Reference numeral 4 denotes a detour device that prevents light in the opposite direction to the signal light from passing through the optical isolator 2. The detour device 4 in FIG. 1 is provided with a through circuit 5 in parallel with the optical isolator 2, and a switch SW is provided in the through circuit 5. When the switch SW is turned off, the signal light is routed through the optical isolator. Ta 2
When the switch SW is turned on, backscatter passes through the through circuit 5, bypasses the optical isolator 2, and is transmitted to the input end of the optical waveguide 3. . The switch SW may be a mechanical switch or an electronic switch. The detour device 4 in FIG. 2 has a through circuit 6 in parallel with the optical isolator 2, and also has a multiplexer or filter 7 on the input side of the optical isolator 2 and a demultiplexer or filter 8 on the output side. The signal light is optically transmitted from the multiplexer or filter 7 through the optical isolator 2, and the backscatter is taken out by the demultiplexer or filter 8 and passed through the through circuit 6 to the optical isolator 2. The signal is detoured, multiplexed into the optical waveguide 3 by a multiplexer or filter 7, and transmitted to the input end of the optical waveguide 3.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a first embodiment of an optical amplification device of the present invention.

FIG. 2 is an explanatory diagram showing a second embodiment of the optical amplification device of the present invention.

FIG. 3 is an explanatory diagram showing an example of a conventional optical amplification device.

FIG. 4 is an explanatory diagram showing another example of a conventional optical amplification device.

[Explanation of symbols]

1 Optical amplifier 2 Optical isolator 3 Optical waveguide 4 Detour device

Claims (1)

[Claims] 1. An optical amplifier 1 such as a fiber amplifier or a laser amplifier that obtains gain by stimulated emission of a fluorescent substance such as a rare earth element mixed into the core, an optical isolator 2 for preventing oscillation, etc. In the optical amplification device in which the optical waveguide 3 is inserted into the optical waveguide 3, the optical waveguide 3 is provided with a detour device 4 that prevents light in the opposite direction to the signal light from passing through the optical isolator 2. Characteristic optical amplification device.