JPH1127214A - Repeater light amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light amplifier for a repeater that can stop and amplifying function, depending upon whether an input signal light is sent or not. SOLUTION: A light amplifier 3 having a rare earth dope fiber 21 wherein a rare earth element is added to a core part and an exciting light source 23 for sending an exciting light to this rare earth dope fiber are located in the central part of an optical transmission line 5-1, and at the input side of the light amplifier, a light receiver 13 for monitoring an input light signal is provided which is connected by way of a light branching device 11. Here, the exciting light source 23 is connected by way of a wave length multiplex coupler 22 provided between the light branching device 11 and an input terminal 21-1 of the rare earth dope fiber 21, and an exciting light Lp to be sent to the rare earth dope fiber 21 is sent in the same direction as the transmission direction of an input optical signal Lsi. Meanwhile, at the input part of the light receiver 13 is located a light band pass filter 12 which allows a wave length of the input optical signal Lsi to pass but prevents a wave length of non-input optical signals, from passing wherein it is determined by the light receiver 13 whether there is an input optical signal or not and a control device 3 is provided so that an output of the exciting light source 23 is not generated when the input optical signal is not detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relay optical amplifying device capable of stopping an amplifying function depending on whether or not an input signal light is being transmitted.

[0002]

2. Description of the Related Art As optical communication becomes full-scale and an optical communication network expands, the development of a relay optical amplifier having a monitoring function and an output monitoring function of an optical amplifier has been advanced (for example, see Japanese Patent Application Laid-Open No. H05-1993). No. 292036).

The functions required of such an amplifier include the following. When transmitting an optical signal amplified by an optical amplifier using a rare earth doped fiber,
The configuration is such that high-level excitation light is sent to the rare-earth-doped fiber and also supplied to the transmission line. For such high-level pump light, when the input optical signal is not transmitted, stopping the supply of the pump light saves energy and also prevents unnecessary light from being transmitted to the transmission line. Is also desired. However, a method of stopping the supply of the pump light when the input optical signal is not transmitted has not been realized yet.

[0004]

Incidentally, an optical signal transmitted over a long distance has a low light receiving level due to transmission loss, and an amplified high level optical signal or pump light is generated nearby. It is not easy to detect accurately.

Accordingly, the present invention provides a relay optical amplifying device capable of stopping supply of pumping light when input signal light is not being transmitted in order to meet such a demand.

[0006]

A first relay optical amplifier according to the present invention is arranged so that the direction in which the pumping light is supplied and the direction in which the input optical signal propagates are the same, and the core unit An optical amplifier having a rare-earth-doped fiber doped with a rare-earth element and a pump light source for sending pump light to the rare-earth-doped fiber is disposed at an intermediate portion of the optical transmission line,
In a repeater optical amplifying device provided with a photodetector for monitoring an input optical signal coupled to an optical transmission line via an optical splitter on an input side of an optical amplifier, an excitation light source is an input end of an optical splitter and a rare-earth doped fiber. The pumping light sent to the rare-earth-doped fiber is sent in the same direction as the transmission direction of the input optical signal, while the input light is input to the input part of the photodetector. An optical band that passes the wavelength of the optical signal but blocks wavelengths other than the input optical signal
A pass filter is provided, and a control device is provided for detecting presence / absence of an input optical signal by a light receiver, and performing control so that output of the excitation light source is not generated when the input optical signal is not detected.

According to the repeater optical amplifying device of the present invention, the pump light of high level power is supplied to the rare earth doped fiber by the wavelength multiplex coupler having the directionality opposite to that of the input side of the photodetector. Can be significantly reduced. In addition, an optical band-pass filter, which passes the wavelength of the input optical signal but blocks wavelengths other than the input optical signal, is arranged at the input of the photodetector, so that the effect of sufficiently eliminating the mixing of the pump light can be obtained. There is.

Further, when an optical isolator is provided between the optical splitter and the wavelength division multiplexing coupler such that the forward direction coincides with the transmission direction of the input optical signal, the pumping light or the amplified optical signal is received. Since there is an effect of preventing the function of trying to mix into the device, the presence or absence of the low-level input optical signal can be accurately detected.

In the second relay optical amplifier according to the present invention, the direction in which the pumping light is supplied is opposite to the direction in which the input optical signal propagates, and the rare-earth element is added to the core. An optical amplifier having an added rare earth-doped fiber and an excitation light source for sending excitation light to the rare earth-doped fiber is arranged in the middle of the optical transmission line. In a repeater optical amplifier having a light receiver coupled to a transmission line and monitoring an input optical signal, a forward direction between an optical splitter and an input end of a rare earth doped fiber coincides with a transmission direction of the input optical signal. And a pumping light source is coupled via a wavelength division multiplexing coupler disposed on the output side of the rare earth doped fiber, and the pump light source is fed into the rare earth doped fiber. The light is sent in the direction opposite to the transmission direction of the input optical signal, while an optical band-pass filter is installed at the input of the optical receiver that passes the wavelength of the input optical signal but blocks wavelengths other than the input optical signal. In addition, a control device is provided which detects the presence or absence of an input optical signal by a light receiver, and performs control such that output of the excitation light source is not generated when the input optical signal is not detected.

According to the relay optical amplifying device of the present invention, high-level power pumping light is supplied to the photodetector through the rare-earth doped fiber, but the optical signal is transmitted between the optical splitter and the wavelength division multiplexing coupler. Since the isolator is provided, it is possible to remarkably reduce the influence of the pump light or the amplified optical signal entering the light receiver. In addition, an optical band-pass filter, which passes the wavelength of the input optical signal but blocks wavelengths other than the input optical signal, is arranged at the input of the photodetector, so that the effect of sufficiently eliminating the mixing of the pump light can be obtained. There is. Also,
In the first and second relay optical amplifiers according to the present invention, the use of a directional optical coupler as the optical splitter can prevent the pump light from being mixed.

[0011]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

FIG. 1 is a block diagram of a first relay optical amplifier according to the present embodiment, in which a direction in which the pump light _Lp is supplied and a direction in which the input optical signal _Lsi propagates are the same. Optical amplifying device. The line optical amplifying apparatus shown in FIG. 1, a light receiving unit 1 for receiving an input optical signal L _si, the optical amplifier 2 for amplifying an input optical signal L _si sends this, feeding the input optical signal L _si And a control device 3 for stopping the function of the optical amplifying section 2 when not performed.

[0013] receiving unit 1 includes an optical splitter 11 that branches an input optical signal L _si propagated through the optical transmission path 5-1, the photodetector for receiving the input optical signal L _si branched by the optical splitter 11 13, the wavelength of which is other than the input optical signal L _si passing wavelength of the input optical signal L _si is the input portion of the light receiver 13 and an optical band-pass filter 12 for blocking.

The optical band-pass filter 12 is formed of a dielectric multilayer film having sharp rising and falling characteristics at the boundary between the transmission region and the blocking region. Is used.

The optical splitter 11 receives the input optical signal L _si
Is passed through the amplifying section 2 and a part of the signal is branched to monitor the input optical signal level.
It is preferable to use an optical coupler. Optical coupler 1
2, for example, as shown in FIG. 2, two optical fibers A and B have a coupling portion 110-1 with an interval S at an intermediate portion thereof.
Having. When the light propagates through the coupling section 110-1, the light can gradually move from one optical fiber to the other optical fiber. Optical coupler 1 having such a configuration
When the input optical signal L _si is input from the input terminal A-1 of the ten,
The input optical signal L _si gradually _changes from the optical fiber A to the optical fiber B.
Move to Therefore, the ratio of branching from the optical fiber A to the optical fiber B can be determined by selecting the interval S of the coupling unit 110-1 to a predetermined length.

Further, when the optical coupler 110 is normally manufactured, the light input to the input terminal A-1 as described above is output to the output terminal A-2, and the light branched to the optical fiber B is output as described above. The signal is sent to the output terminal B-2 and is not output to the input terminal B-1. Similarly, the light input to the output terminal A-2 is
-1 and sent to the input terminal B-1 and not output to the output terminal B-2. Therefore, when the input optical signal L _si to the input terminal A-1 is input, the input optical signal L _si is sent branches to the output terminal A-2 and the output end B-2, the output end B-2 Input optical signal L _si reaches the light receiver 13. On the other hand, even it has occurred that reflected light of the excitation light L _p is incident from the output terminal A-2, the reflected light propagates to the input terminal A-2 and the input terminal A-1, the output end B-2 Is not propagated, so that it hardly reaches the light receiver 13. This means that the amplified optical signal L
_{Even if} the reflected light of _so enters from the output terminal A-2 of the optical coupler 110, it hardly reaches the light receiver 13 for the same reason, and the input optical signal L _si can be accurately monitored.

Next, the optical amplifier 2 will be described. The optical amplifier 2 has a function of amplifying the input optical signal _Lsi that has passed through the optical splitter 11 and transmitting the amplified output optical signal _Lso to the optical transmission line 5-2. -Doped rare-earth doped fiber 21 and rare-earth-doped fiber 2
Wavelength for feeding an excitation light source 23 for feeding the excitation light L _p to 1 and send the excitation light L _p transmitted from the pumping light source 23 to the rare earth-doped fiber 21 to the input optical signal L _si simultaneously to the rare earth-doped fiber 21 Multiplexer 22
And

The rare earth-doped fiber 21 supplies excitation light having a wavelength of 1.48 μm by adding erbium to the core portion of a silica glass fiber, and emits a 1.5-μm wavelength light.
An optical signal of 5 μm can be amplified. Further, when neodymium is used as a rare earth element, an excitation signal having a wavelength of 0.8 μm can be supplied to amplify an optical signal having a wavelength of 1.33 μm.

As the optical transmission line 5, a single-mode optical fiber is usually used as a long-distance line, and a multi-mode optical fiber is used as a short-distance line.

As shown in FIG. 3, for example, as shown in FIG. 3, the optical wavelength multiplexing coupler 22 has a coupling section 22-1 with an interval S between two optical fibers C and D, and when light propagates between them. It is possible to gradually move from one optical fiber to the other. If such configuration of the light from the input end C-1 of the wavelength lambda ₁ of the optical wavelength multiplexing coupler 22 is incident, the incident light is gradually migrating to an optical fiber D from the optical fiber C, optical fiber again after finishing moving all The movement from D to the optical fiber C is repeated until the coupling length S ends. On the other hand, when light having a wavelength of λ ₂ enters from the input terminal D- 1 of the optical wavelength division multiplexing coupler 22, it similarly moves between the optical fibers C and D. At this time, since the wavelengths of the light incident from the input terminals C-1 and D-1 are different, the periods at which the two move between the optical fiber C and the optical fiber D are different. Therefore, by selecting the coupling interval S to a predetermined length, both the light having the wavelength λ _{1 and} the light having the wavelength λ ₂ can be emitted to the output end C-2 of the optical fiber C.

Further, when the optical coupler 110 is manufactured normally, the wavelength λ ₁ input to the input terminal C-1 and the wavelength λ ₂ light input to the input terminal D-1 as described above. Are sent to the output terminal C-2. The wavelength λ ₁ input to the output terminal C-2 and the wavelength λ ₂ light input to the output terminal D-2 are both transmitted to the input terminal C-1.

[0022] Thus, the input optical signal L _si incident on the input end C-1 is sent to the output terminal C-2, also is input to the input terminal D-1 pumping light L _p is also the output end C-2 Sent to On the other hand, even when a part is caused to be reflected excitation light L _p sent to the output terminal C-2, the reflected light propagates to the input terminal D-1, input light receiver 13 is connected It hardly propagates to the end C-1. This means that the reflected light of the amplified optical signal L _so is output from the output terminal A-
Even if light is incident from the light receiving device 13 for the same reason,
Is rarely reached. Since the wavelength multiplexing optical coupler 22 having such a directionality is used, the wavelength multiplexing optical coupler 22 has a function of preventing the pump light _Lp and the amplified optical signal _Lso from being mixed into the light receiver 13.

The relay amplifying device according to the present embodiment comprises a photodetector 1
3 and is detected whether the input optical signal L _si is the light receiver 13 between the excitation light source 23, when the input optical signal L _si is not detected the control unit 3 for controlling so that the output of the pumping light source 23 does not occur Is provided. Thus, the control device 3
Can save energy by stopping the supply of high-level pump light when an input optical signal is not being transmitted, and prevent unnecessary light from being transmitted to the transmission line. be able to.

According to the relay optical amplifier of this embodiment,
Since the pumping light Lp of the high-level power is supplied in the direction opposite to the direction in which the light receiver 13 is disposed by the wavelength multiplexing coupler 22, the pumping light L _p can significantly reduce the effect of contamination on the light receiver 13 . An optical band-pass filter 1 which passes the wavelength of the input optical signal L _si but blocks wavelengths other than the input optical signal L _si is applied to the input portion of the light receiver 13.
Because 2 is arranged, it is possible to prevent contamination of sufficiently excited light L _p.

Furthermore, since the optical coupler 13 is arranged so as the light receiver 13 faces the direction of the opposite direction to the excitation light L _p, it can be excited light L _p is prevented from being mixed into the light receiver 13 .

FIG. 4 is a diagram showing a configuration related to an improvement of the first repeater amplifying device shown in FIG. 1. In FIG. 4, an optical isolator 4 is disposed between an optical branching device 11 and a wavelength division multiplexing coupler 22 in the order shown. They are arranged so that the direction matches the transmission direction of the input optical signal _Lsi . By arranging the optical isolator 4 in this manner, there is an effect of preventing the pump light _Lp or the reflected light of the amplified optical signal _{Lso from} being mixed into the photodetector 13, so that the low-level input optical signal L _si can be detected more accurately.

The optical isolator 4 has a large loss in the reverse direction in addition to a small loss in the forward direction of the input optical signal _Lsi , and the pump light L _p to be mixed into the light receiver 13 or the amplified light. It is preferable to effectively block the reflected component of the subsequent optical signal L _so .

FIG. 5 is a block diagram of a second relay optical amplifying device according to this embodiment. The light receiving unit 1, the optical amplifying unit 2-1, the control device 3, and the optical isolator 4 are connected to each other. The light receiving unit 1, the control device 3, and the optical isolator 4 are the same as the first relay amplification device. In this relay optical amplifier, the direction in which the pump light _Lp is supplied and the input optical signal L _si
Is the direction opposite to the direction in which the light propagates.

The optical amplifying section 2-1 in FIG. 5, a rare-earth doped fiber 21, the pumping light source 23 for feeding the excitation light L _p in the rare earth-doped fiber 21, the output side 21-2 of the rare earth-doped fiber 21 The wavelength multiplexing coupler 22 is arranged. Pumping light L _p emitted from the excitation light source 23 output 21 of the rare-earth doped fiber 21
-2 to the input end 21-1 of the rare earth doped fiber 21. This high-level power pump light L
When _p is sent to the optical splitter 11 directly, since the excitation light L _p is more likely to leak light to the light receiver 13 is configured to block the passage in the reverse direction by the optical isolator 4.

According to the relay optical amplifier of the present embodiment,
The pump light L _{p of} high level power by the optical isolator 4
Can be prevented from propagating in the direction of the photodetector 5 through the rare-earth-doped fiber 1, and the effect of the amplified optical signal L _so entering the photodetector 13 can be significantly reduced.
Further, since the optical band-pass filter 12 is the input wavelength of the input optical signal L _si passes wavelengths other than the input optical signal L _si is to prevent the light receiver 13 is arranged, sufficiently excited light Can be removed.

[0031]

The present invention is embodied in the form described above and has the following effects.

According to the first relay optical amplifying device of the present invention, since the pumping light is supplied by the directional wavelength multiplexing coupler, the influence of the pumping light mixed into the input optical signal is significantly reduced. be able to. In addition, since an optical band-pass filter is provided at the input of the receiver, it is necessary to prevent the reflected light, which is likely to reflect the excitation light and leak into the receiver, if this occurs. Thus, it is possible to accurately detect the presence or absence of the input optical signal and control the oscillation of the excitation light source.

According to the second relay optical amplifying device of the present invention, the optical isolator prevents the pump light from being incident on the light receiver, and the directional optical coupler converts the input optical signal. Since the light is introduced into the light receiver, the influence of the excitation light entering the light receiver can be significantly reduced. Further, since the optical band-pass filter is arranged at the input part of the light receiver, the mixing of the excitation light can be sufficiently removed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first relay optical amplifier according to an embodiment.

FIG. 2 is a diagram illustrating the operation of an optical coupler.

FIG. 3 is a diagram illustrating the operation of a wavelength division multiplexing coupler.

FIG. 4 is a diagram showing a configuration relating to an improvement of a first relay optical amplifier.

FIG. 5 is a configuration diagram of a second relay optical amplifier according to the present embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light receiving part, 2 ... Optical amplification part, 3 ... Control device, 4 ... Optical isolator, 5 ... Optical transmission line, 11 ... Optical splitter, 1
2 ... optical bandpass filter, 13 ... receiver, 21 ...
Rare earth element doped fiber, 21-1 ... input end, 21
-2: output end, 22: wavelength multiplex coupler, 22-1 ...
Coupling part, 23 ... excitation light source, 110 ... optical coupler, 110
-1: coupling portion, L _si: input optical signal, L _so: amplified optical signal, L _p: excitation light, A, B, C, D: optical fiber,
S: interval, A-1, B-1, C-1, D-1: input terminal, A-2, B-2, C-2, D-2: output terminal

Claims (4)

[Claims] An optical amplifier having a rare earth doped fiber having a core doped with a rare earth element and an excitation light source for sending excitation light to the rare earth doped fiber is arranged at an intermediate portion of an optical transmission line. On the input side of the relay optical amplifier having a light receiver coupled to the optical transmission line via an optical splitter and monitoring an input optical signal, the pumping light source is the optical splitter and the rare earth doped fiber. The pumping light, which is coupled through a wavelength multiplexing coupler arranged between the input end and the rare earth-doped fiber, is sent in the same direction as the transmission direction of the input optical signal, while the light receiver An optical band-pass filter is disposed at the input portion for transmitting the wavelength of the input optical signal but blocking wavelengths other than the input optical signal. And detecting the presence or absence of signal, the input optical signal relay optical amplifier when not detected, wherein the control device is provided for controlling so that the output of the excitation light source is not generated. 2. An optical isolator arranged between the optical splitter and the wavelength multiplex coupler such that a forward direction coincides with a transmission direction of the input optical signal. 3. The relay optical amplifier according to 1. 3. An optical amplifier having a rare earth doped fiber having a core doped with a rare earth element and an excitation light source having an excitation light source for feeding excitation light to the rare earth doped fiber is disposed in an intermediate portion of an optical transmission line. An input side of the relay optical amplifying device having a light receiver coupled to the optical transmission line via an optical splitter to monitor an input optical signal, wherein the optical splitter and the input end of the rare earth doped fiber are An optical isolator whose forward direction is oriented so as to coincide with the transmission direction of the input optical signal is disposed between them, and the pumping light source is provided via a wavelength multiplexing coupler disposed on the output side of the rare earth doped fiber. The pump light, which is coupled and sent to the rare-earth doped fiber, is sent in a direction opposite to the transmission direction of the input optical signal, while the input of the light receiver is provided at the front. An optical band-pass filter is disposed that passes the wavelength of the input optical signal but blocks wavelengths other than the input optical signal, and detects the presence or absence of the input optical signal by the photodetector, and does not detect the input optical signal. The relay optical amplifying device is provided with a control device for controlling the output of the pumping light source so as not to be generated at the time. 4. The relay optical amplifier according to claim 1, wherein the optical splitter is an optical coupler having directionality.