JP2597748B2 - Optical amplifier - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical amplifier incorporated in an optical fiber transmission system and capable of efficiently amplifying signal light transmitted through an optical fiber as it is.

<Conventional technology> When performing long-distance optical communication using an optical fiber, a repeater is interposed at regular intervals in consideration of attenuation of the signal light propagating through the optical fiber, and the signal light is electrically transmitted. Amplification is done.

In recent years, stimulated emission using the population inversion of electrons in ions of rare earth elements such as erbium and neodymium,
Technology for amplifying light has been developed. Based on this principle, signal light and pumping light are guided to an optical fiber doped with erbium, etc., and the signal light is amplified in this optical fiber to require electrical energy. With a simple repeater that does not
Realization of long-distance optical communication has been studied.

As shown in FIG. 2 showing the concept of a conventional optical transmission system incorporating such an optical amplifier, an optical cable 103 incorporating a transmission optical fiber 102 connected at one end to a signal light source 101 emitting signal light is provided. Also, a transmission optical fiber 105 connected at one end to an excitation light source 104 that oscillates excitation light is incorporated.Optical couplers 106 for multiplexing the signal light and the excitation light are provided at the other ends of the optical fibers 102 and 105. One end of the amplification optical fiber 107 to which a rare earth element such as erbium is added is connected via the. This amplification optical fiber 1
On the other end side of 07, a transmission filter incorporated in an optical cable 109 via an optical filter 108 that allows transmission of only signal light amplified in the amplification optical fiber 107 and blocks transmission of excitation light. One end of the optical fiber 110 is connected. To the other end of the transmission optical fiber 110, a distributor 111 for branching the amplified signal light into a large number is connected, and the distributor 111 has a plurality of receivers 112 respectively. Connected via 113.

Therefore, the signal light oscillated from the signal light source 101 propagates through the transmission fiber 102 and is input into the amplification optical fiber 107 via the optical coupler 106. On the other hand, the pumping light oscillated from the pumping light source 104 propagates in the transmission optical fiber 105, is multiplexed with the signal light by the optical coupler 106, and is then input into the amplification optical fiber 107. When the pumping light enters the amplification optical fiber 107, the amplification optical fiber 107 is excited, and the power of the pumping light moves to the signal light in the amplification optical fiber 107, and the optical power of the pumping light is reduced. It is converted into the optical power of the signal light, and the signal light is amplified.

The signal light thus amplified in the amplification optical fiber 107 passes through the optical filter 108, but the excitation light is blocked by the optical filter 108, and only the amplified signal light is transmitted through the transmission optical fiber 110. , Is split into a plurality of signal lights by the splitter 111, and is distributed to the respective receivers 112 via the transmission optical fiber 113.

<Problem to be Solved by the Invention> In the conventional optical transmission system shown in FIG.
1 and the excitation light source 104 independently blink the signal light and the excitation light. In other words, the transmission optical fiber 105 constituting the transmission path of the excitation light and the transmission optical fiber 110 constituting the transmission path of the signal light were disconnected due to some accident, disaster, or mistake of the worker performing the construction. However, since the excitation light oscillated from the excitation light source 104 is output irrespective of these disconnection states, there is a possibility that the following problems may be caused.

For example, when the transmission optical fiber 105 for guiding the excitation light from the excitation light source 104 is cut off or externally damaged, the excitation light is emitted from the cut or damaged part. Generally, the output of pump light is 20mW to 200m
Since there is also about W, this must be avoided as much as possible from the eyes of workers.

Also, the middle of the transmission optical fiber 110 that guides the signal light in the amplified state from the signal light source 101 is cut off,
In the case of external damage, the amplified signal light leaks from the cut or damaged portion, and it is necessary to minimize the possibility of the signal light being seen by the operator.

As described above, in the conventional optical transmission system, when the transmission optical fiber for guiding the pump light or the transmission fiber for guiding the amplified light is cut or externally damaged, these optical fibers are cut. There is a problem that a light beam with a large energy leaks from a location or a damaged location.

<Object of the Invention> The present invention provides a method for cutting an optical fiber transmitting an excitation light or an amplified optical light even if the optical fiber is cut or externally damaged. It is an object of the present invention to provide a safe optical amplifier in which strong optical energy does not leak from a damaged part.

<Means for Solving the Problems> An optical amplifier according to the present invention includes an excitation light source that oscillates excitation light, an amplification optical fiber capable of amplifying signal light from a signal light source by the excitation light, and an amplification optical fiber. An optical coupler provided at one end of the optical waveguide for guiding the excitation light and the signal light from the excitation light source into the amplification optical fiber, and an optical coupler provided at the other end of the amplification optical fiber. An optical filter that blocks transmission, an optical splitter that branches a part of the amplified signal light transmitted through the optical filter for disconnection detection, and a signal light for disconnection detection branched from the optical splitter And a control device for detecting that a detection signal from the light receiving element falls below a certain threshold level and stopping the oscillation of the excitation light.

<Operation> The pump light oscillated from the pump light source is introduced from one end of the amplification optical fiber through the optical coupler together with the signal light. In the amplification optical fiber, the signal light is amplified by the pump light, and emitted from the other end of the amplification optical fiber. The pump light is cut off by an optical filter provided on the other end of the amplification optical fiber. The amplified signal light passes through the optical filter, and a part of the signal light is transmitted from the optical splitter to the disconnection detection signal. The light is branched and guided to the light receiving element.

Here, if the middle of the transmission optical fiber between the pump light source and the optical coupler is cut off or externally damaged, the intensity of the signal light for disconnection detection decreases, When the light receiving element detects this state, the control device stops the oscillation of the excitation light from the excitation light source.

Also, if the optical fiber for transmitting the signal light that has been transmitted through the optical filter and amplified is cut off or is damaged externally, the intensity of the signal light for disconnection detection decreases. When the light receiving element detects this state, the control device stops the oscillation of the excitation light from the excitation light source.

<Embodiment> As shown in FIG. 1 showing the concept of an embodiment in which the optical amplifier according to the present invention is applied to the optical transmission system shown in FIG. 2, one end is connected to a signal light source 11 which emits signal light. In the optical cable 13 incorporating the optical fiber 12 for transmission, a transmission optical fiber 15 whose one end is connected to an excitation light source 14 that oscillates excitation light, and a detection optical fiber 17 whose one end is connected to a light receiving element 16 described later. It is incorporated together with the transmission optical fiber 12.

One end of an amplification optical fiber 19 doped with a rare earth element such as erbium is connected to the other end of these transmission optical fibers 12 and 15 via an optical coupler 18 for multiplexing signal light and pump light. The other end of the amplification optical fiber 19 has an optical filter 20 that allows transmission of only the signal light amplified in the amplification optical fiber 19 and blocks transmission of the pump light.
One end of a transmission optical fiber 22 incorporated in the optical cable 21 together with the detection optical fiber 17 is connected via the. At the other end of the transmission optical fiber 22, a part of the amplified signal light is branched as a disconnection detection signal light, and guided to the other end of the detection optical fiber 17, while the remaining signal is An optical splitter 24 for guiding most of the light to a distributor 23 to be described later is connected.

The splitter 23 splits the signal light in the amplified state into a large number, and one ends of a large number of transmission optical fibers 25 corresponding to the number of splits are connected to the splitter 23. A distributor 23 is provided at one end of the transmission optical fiber 25.
The receivers 26 respectively receiving the signal lights branched by the above are connected.

The light receiving element 16 is connected to a control device 28 that operates a driving device 27 of the excitation light source 14 based on an output signal from the light receiving element 16. Then, the control device 28 compares a preset threshold value and a detection signal from the light receiving element 16, and when the detection signal from the light receiving element 16 is smaller than the threshold value, stops the operation of the driving device 27, Otherwise, the driving device 27 is operated so that the operation of the driving device 27 is continued.
Control program is set.

Therefore, the pump light source 14 and the optical coupler 18 are connected to each other to transmit the pump light through the transmission optical fiber 15 or the optical filter 20.
When there is no break or external damage in the middle of the transmission optical fiber 22 for transmitting the amplified signal light by connecting the optical splitter 24 and the optical splitter 24, the signal light amplified by the amplification optical fiber 19 is For the most part, each receiver 26
Sent to A part of the amplified signal light extracted by the optical splitter 24 is guided to the light receiving element 16 via the optical fiber 17 for detection as signal light for disconnection detection, and the light of the signal light for disconnection detection is output. The power is constantly monitored by the controller 28.

Here, if the middle of the transmission optical fiber 15 for guiding the excitation light is cut off or is externally damaged,
As the pump light is no longer supplied to the amplification optical fiber 19 or the supply amount is reduced, the signal light is not sufficiently amplified and the intensity of the disconnection detection signal light is reduced. Is detected, the control device 28
Is stopped, and the oscillation of the excitation light from the excitation light source 14 is stopped.

Further, even when the transmission optical fiber 22 that guides the amplified signal light through the optical filter 20 is cut off or receives external damage, the intensity of the disconnection detection signal light is reduced. When the light receiving element 16 detects this state, the control device 28 stops the operation of the driving device 27 and stops the oscillation of the excitation light from the excitation light source 14.

If the middle of the transmission optical fiber 25 after the distributor 23 is cut off or externally damaged, the optical power of the signal light passing through the transmission optical fiber 25 is distributed. Since it has been distributed by the container 23, it has been reduced to such a level that there is almost no danger, and even if this gets into the eyes of the operator, it does not pose any particular problem.

<Effects of the Invention> According to the optical amplifier of the present invention, a part of the signal light amplified by the amplification optical fiber is guided from the optical splitter to the light receiving element as signal light for disconnection detection, and the light intensity is detected. Since the operation of the pump light source is controlled by the control device, if a cut portion or a damaged portion occurs in the middle of the transmission optical fiber for guiding the excitation light or the transmission optical fiber for guiding the amplified signal light, As a result of immediately stopping the oscillation of the excitation light from the excitation light source, there is no problem even if an operator or the like mistakenly looks into the cut or damaged portion of the transmission optical fiber.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a schematic configuration of an embodiment of an optical amplifier according to the present invention, and FIG. 2 is a conceptual diagram showing an example of a conventional optical amplifier. Also, in the reference numerals in the figure, 11 is a signal light source, 12, 15, 22 are transmission optical fibers, 14 is an excitation light source, 16 is a light receiving element, 17 is a detection optical fiber, 18 is an optical coupler, 19 is an amplification An optical fiber, 20 is an optical filter, 24 is an optical splitter, 27 is a driving device, and 28 is a control device.

Claims (1)

(57) [Claims] 1. An excitation light source for oscillating excitation light, an amplification optical fiber capable of amplifying a signal light from a signal light source by the excitation light, and an amplification optical fiber provided at one end of the amplification optical fiber. An optical coupler that guides the excitation light and the signal light into the amplification optical fiber; an optical filter that is provided on the other end side of the amplification optical fiber and that blocks transmission of the excitation light; A light-receiving element to which the signal light for disconnection detection is obtained by branching a part of the signal light in an amplified state that has passed through for detection of disconnection, and a detection signal from the light-receiving element being below a certain threshold level An optical amplifier, comprising: a control device that detects the occurrence of the excitation light and stops the oscillation of the pump light.