JP2500746B2 - Optical fiber amplifier - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber amplifier used as a repeater for an optical fiber communication system and provided with a rare earth-doped fiber as an amplifying element for amplifying an input optical signal.

[0002]

2. Description of the Related Art An input optical signal is superposed on a main optical signal which carries a main information signal representing communication information, and is superposed on the main optical signal to monitor a fault of a transmission line or a repeater of the system. And a sub-optical signal that carries one of a sub-interval information signal for indicating a fault section of the system and a sub-information signal for indicating a fault section.

A conventional repeater is an opto-electric converter that reproduces a main information signal and a fault monitoring sub-information signal or a fault section indicating sub-information signal from an input optical signal as an electrical signal, and amplifies and amplifies the electrical signal. It has an electric amplification element which outputs the electric signal thus amplified, and an electro-optical converter which converts the amplified electric signal into an output optical signal. The repeater further includes a failure section indicating sub-information signal assigned to the repeater to indicate the failure section when neither the failure monitoring sub-information signal nor the failure section indicating sub-information signal exists in the electrical signal. And a sub-information signal generation unit for supplying the electric power to the electric amplification element. As a result, the faulty section indicating sub-information signal assigned to the repeater is carried as an output optical signal.

[0004]

However, when an optical fiber amplifier equipped with a rare earth-doped fiber as an amplifying element is used as a repeater, the rare earth-doped fiber is directly amplified without converting an input optical signal into an electric signal. In the repeater, when neither the fault monitoring sub-information signal nor the fault section indicating sub-information signal is present in the input optical signal, the fault section indicating sub-information signal assigned to the repeater to indicate the fault section is transmitted. It has a drawback that it cannot be added to the output optical signal.

Japanese Patent Laid-Open No. 61-232733 discloses a transmitting station for transmitting a main signal as an optical signal, an optical cable connected to the transmitting station for transmitting an optical signal, and an optical cable connected to the optical cable for transmitting an optical signal. In a system having a receiving station for receiving, a specific signal for optical cable monitoring is transmitted from the transmitting station to the optical cable as an optical signal, and when the receiving station cannot receive the specific signal for optical cable monitoring,
It is disclosed that another optical cable is used to transmit a main signal and a specific signal for monitoring the optical cable. In this system, the specific signal for monitoring the optical cable may correspond to the sub-information signal for monitoring the failure, but since this system has a transmitting station and a receiving station connected to both ends of a pair of optical cables, The faulty section indicating sub-information signal shown is not necessary. Further, this system does not disclose a repeater for amplifying an optical signal, in which a transmitting station and a receiving station are connected to both ends of a pair of optical cables, and a rare earth-doped fiber is used as an amplifying element for amplifying an optical signal. It does not disclose the use of.

An object of the present invention is to eliminate the above-mentioned drawbacks, and in an optical fiber amplifier using a rare earth-doped fiber as a repeater, an input optical signal is a fault monitoring sub-information signal and a fault section indicating sub-information signal. It is an object of the present invention to provide an optical fiber amplifier capable of inserting a failure section indicating sub-information signal assigned to the repeater to indicate a failure section into an output optical signal when none of the above exists.

[0007]

According to the present invention, a main optical signal that is used as a repeater of an optical fiber communication system and carries a main information signal that represents communication information, and is superimposed on the main optical signal, An input optical signal having a sub-optical signal for carrying any one of a fault monitoring sub-information signal for monitoring a fault of the system and a fault section indicating sub-information signal indicating a fault section of the system, In an optical fiber amplifier for receiving, an optical coupler having a first coupler input terminal for receiving the input optical signal and a second coupler input terminal and outputting the input optical signal as a coupler output optical signal ( 12)
A rare earth-doped fiber (13) connected to the optical coupler to amplify the optical signal output from the coupler and output an amplified optical signal; and an optical signal amplified to be connected to the rare earth-doped fiber An optical branching circuit (1) for branching the optical signal into first and second optical branching signals and outputting the first optical branching signal as an output optical signal; An opto-electric conversion means (2) for converting a signal into an electric signal; connected to the opto-electric conversion means, and neither the fault monitoring sub-information signal nor the fault section instructing sub-information signal exists in the electric signal A detection means (50) for detecting the fact and outputting a detection signal; a natural frequency assigned to the optical fiber amplifier for indicating the fault section in response to the detection signal and connected to the detection means. Said obstacle having A sub information signal generating means (7) for generating a section indicating sub information signal; and a new sub information signal generating means connected to the sub information signal generating means and the second coupler input terminal for carrying the fault section indicating sub information signal. Sub-optical signal generating means (15 and 16) for generating a new sub-optical signal and supplying the new sub-optical signal to the second coupler input terminal. The input optical signal and the new sub-optical signal are combined in a state where the new sub-optical signal supplied to the input terminal of the second coupler is superimposed on the input optical signal, and the combined optical signal is combined with the new optical signal. An optical fiber amplifier characterized by outputting as a coupler output optical signal is obtained.

Furthermore, according to the present invention, the optical coupler comprises:
The optical fiber amplifier is obtained which is a wavelength division multiplexer.

Further, according to the present invention, the main optical signal is pulse-modulated by the main information signal having a predetermined bit rate, and each of the sub optical signals has the low-frequency fault monitoring slower than the main information signal. Amplitude-modulated by one of the sub-information signal for fault and the sub-information signal for fault section designation, and the sub-information signal for fault section designation is from a frequency band different from the frequency of the sub-information signal for fault monitoring. The sub-information signal generating means having a selected frequency, in response to the detection signal, generates the fault section indicating sub-information signal having the natural frequency included in the frequency band, and outputs the sub-optical signal. The optical fiber amplifier is characterized in that the signal generating means generates the new sub optical signal amplitude-modulated by the fault section indicating sub information signal.

Further, according to the present invention, the detecting means is
First detection / determination means (3 and 4) connected to the photoelectric conversion means and detecting / determining that the faulty section indicating sub-information signal does not exist in the electric signal; and the photoelectric conversion means. When connected to the first detection / determination means and the first detection / determination means detects / determines that the fault section indicating sub-information signal does not exist, the fault monitoring sub-signal is added to the electrical signal. Detects the absence of information signals
The above-mentioned optical fiber amplifier is obtained, which comprises: second detection / judgment means (5 and 6) for judging and outputting the detection signal.

According to the present invention, the detection means is connected to the photoelectric conversion means and detects the absence of the fault section indicating sub-information signal in the electric signal.
And a second signal detection circuit (24) connected to the opto-electric conversion means for detecting the absence of the fault monitoring sub-information signal in the electric signal.
When the first signal detection circuit is connected to the first and second signal detection circuits and the first signal detection circuit detects that the faulty section indicating sub-information signal does not exist, and the second signal detection circuit causes the fault. A determination means (25) for outputting the detection signal when it is detected that the monitoring sub-information signal does not exist.
And the optical fiber amplifier.

[0012]

The present invention will be described below with reference to the drawings.

Referring to FIG. 1, an optical fiber amplifier according to a first embodiment of the present invention is used as a repeater in an optical fiber communication system. The optical fiber amplifier includes a main optical signal that carries a main information signal representing communication information, a sub-information signal for superimposing a fault on the main optical signal for monitoring a fault of the system, and a fault section of the system. And a sub-optical signal carrying either one of the sub-information signal for indicating a fault section and the sub-optical signal. The main information signal and the fault-monitoring sub-information signal are generated by the transmitting terminal station of the system, and the fault-segment indicating sub-information signal is generated by the upstream repeater.

The present optical fiber amplifier has an amplifier input terminal 11 for receiving an input optical signal from a transmission line and an amplifier output terminal 14 connected to another transmission line. A wavelength division multiplexing (WDM) coupler 12 is connected to an amplifier input terminal 11 and has a first coupler input terminal for receiving an input optical signal and a second coupler input terminal. It acts as an optical coupler that outputs a signal as a coupler output optical signal. Rare earth doped fiber 1
3 is connected to the WDM coupler 12, amplifies the optical signal output from the coupler, and outputs the amplified optical signal.

The optical branching circuit 1 comprises a rare earth-doped fiber 13
And the amplifier output terminal 14 to branch the amplified optical signal into first and second branched optical signals, and the first branched optical signal is sent to the amplifier output terminal 14 as an output optical signal.
The light receiving element 2 is connected to the optical branching circuit 1 and functions as a photoelectric conversion element that converts the second branched optical signal into an electric signal.
The detection unit 50 is connected to the light receiving element 2 and detects that neither the fault monitoring sub-information signal nor the fault section instructing sub-information signal exists in the electrical signal, and outputs a detection signal. The oscillating circuit 7 is connected to the detection unit 50, and in response to the detection signal, sub information for generating a fault section indicating sub information signal having a natural frequency assigned to the optical fiber amplifier in order to indicate the fault section. Acts as a signal generator. The pumping laser drive circuit 16 is connected to the oscillation circuit 7, drives the pumping laser 15 with a fault section indicating sub-information signal having a natural frequency, and supplies a new sub-light for carrying the fault section indicating sub-information signal. A signal is generated and the new sub-optical signal is supplied to the second coupler input terminal of the WDM coupler 12. That is, the combination of the pumping laser drive circuit 16 and the pumping laser 15 is connected to the oscillation circuit (sub-information signal generation section) 7 and the second coupler input terminal, and carries a new section for carrying the fault section indicating sub-information signal. And generates a new sub-optical signal and supplies the new sub-optical signal to the second coupler input terminal of the WDM coupler 12 as a sub-optical signal generator.

The WDM coupler 12 as an optical coupler combines the input optical signal and the new sub optical signal in a state in which the new sub optical signal supplied to the second coupler input terminal is superimposed on the input optical signal. The combined optical signal is output as a coupler output optical signal.

Specifically, in the transmitting terminal station, the main optical signal is pulse-modulated by the digital main information signal having a predetermined bit rate, and in the transmitting terminal station, the sub optical signal is a low frequency analog slower than the main information signal. Amplitude modulation is performed by the sub-information signal for fault monitoring. As a result, in the transmitting terminal station, the main information signal is shallowly amplitude-modulated by the fault monitoring sub information signal. In the repeater upstream of this repeater, the sub-optical signal may be amplitude-modulated by a low-frequency analog fault section indicating sub-information signal having a slower frequency than the main information signal.
At this time, the failure section indicating sub information signal has a frequency selected from a frequency band higher than the frequency of the failure monitoring sub information signal. The oscillating circuit (sub-information signal generation unit) 7 responds to the detection signal to generate a fault section indicating sub-information signal having a natural frequency included in the frequency band, and to drive the pump laser drive circuit 16 and the pump laser. The combination of 15 (sub optical signal generation unit) generates a new sub optical signal amplitude-modulated by the fault section indicating sub information signal.

Attention is paid to the detector 50. The first detection circuit 3 detects the faulty section indicating sub-information signal from the electric signal from the light receiving element 2, and the first determination circuit 4 detects the faulty section indicating sub-information signal from the output of the first detection circuit 3. The presence or absence of is determined. The presence of the faulty section indicating sub-information signal indicates that a fault has occurred in the section in charge of the upstream repeater. If there is no fault section indicating sub-information signal, the system is normal, or the section in charge of this optical fiber amplifier (the transmission line connected to the amplifier input terminal 11 of this optical fiber amplifier and immediately before being connected to this transmission line) (A section with a repeater) is either faulty.
If there is no sub-information signal for indicating a faulty section, the second detection circuit 5
Receives an electric signal from the light receiving element 2 and detects a failure monitoring sub-information signal. The second determination circuit 6 checks the modulation degree of the failure monitoring sub-information signal with respect to the main information signal, and if the modulation degree is within a predetermined range, determines that the system is normal, and the modulation degree is within a predetermined range. If it is not within the range, it is judged that a failure has occurred in the section in charge of this optical fiber amplifier. When the second judging circuit 6 recognizes a failure in the section in charge of the optical fiber amplifier, it outputs the detection signal and operates the oscillation circuit 7. Here, if the output frequency of the oscillation circuit 7 is made different for each repeater of the system, the faulty relay section can be specified.

As described above, the combination of the first detection circuit 3 and the first determination circuit 4 is the light receiving element (photoelectric conversion element) 2
Connected as a first detection / determination unit for detecting / determining that there is no fault section indicating sub-information signal in the electrical signal, and the combination of the second detection circuit 5 and the second determination circuit 6 is A light receiving element (photoelectric conversion element) 2 and a first detection / determination unit, which detects / determines that there is no fault section indicating sub-information signal in the electrical signal and outputs the detection signal Acts as a detection / determination unit of.

Referring to FIG. 2, the optical fiber amplifier according to the second embodiment of the present invention is similar to that shown in FIG.
The optical fiber amplifier is the same as the optical fiber amplifier of FIG. The first signal detection circuit 23 is connected to the light receiving element (photoelectric conversion element) 2, detects that the electrical signal does not include the faulty section indicating sub-information signal, and does not include the faulty section indicating sub-information signal. A signal of logic "1" indicating that is output. When there is a faulty section indicating sub-information signal in the electrical signal, a signal of logic "0" indicating that the faulty section indicating sub-information signal is present is output. The second signal detection circuit 24 is connected to the light receiving element (photoelectric conversion element) 2 and detects that the failure monitoring sub-information signal does not exist in the electric signal, and detects that the failure monitoring sub-information signal does not exist. The signal of the logic "1" is output. When the fault monitoring sub-information signal exists, a signal of logic "0" indicating that the fault monitoring sub-information signal exists is output. At this time, since the failure monitoring sub-information signal has a different frequency for each optical fiber amplifier, it is necessary to sweep and detect the frequency.
The AND circuit 25 is connected to the first and second signal detection circuits 23 and 24, and when the first signal detection circuit 23 detects that the fault section indicating sub-information signal does not exist and the second signal detection. When the circuit 24 detects that the failure monitoring sub-information signal does not exist, it functions as a determination unit that outputs a signal of logic "1" as the detection signal.

That is, when the fault monitoring sub-information signal exists and the fault section indicating sub-information signal does not exist, it means that the system is normal. In this case, the AND circuit 25 outputs a signal of logic "0", and the oscillation circuit 7 does not operate. If the fault monitoring sub-information signal does not exist and the fault section indicating sub-information signal exists, a fault is detected by the upstream repeater,
This is a case in which the sub-information signal for indicating a faulty section has already been transmitted. Therefore, it is not necessary to newly send the fault section designating sub-information signal, the AND circuit 25 outputs a signal of logic "0", and the oscillation circuit 7 does not operate. If there is no fault monitoring sub-information signal and no fault section indicating sub-information signal, it means that there is a fault in the section in charge of this optical fiber amplifier. In order to inform the receiving end station, a sub-information signal for indicating a faulty section must be sent. In this case, the AND circuit 25 outputs a signal of logic “1” to operate the oscillation circuit 7.

[0022]

As described above, according to the present invention, in an optical fiber amplifier using a rare earth-doped fiber as a repeater, the input optical signal is either a fault monitoring sub-information signal or a fault section indicating sub-information signal. Thus, an optical fiber amplifier capable of inserting the faulty section indicating sub-information signal assigned to the repeater to indicate the faulty section into the output optical signal can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of an optical fiber amplifier according to a first embodiment of the present invention.

FIG. 2 is a block diagram of an optical fiber amplifier according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical branch circuit 2 Light receiving element (photoelectric conversion element) 3 1st detection circuit 4 1st determination circuit 5 2nd detection circuit 6 2nd determination circuit 7 Oscillation circuit (sub information signal generation part) 11 Amplifier input Terminal 12 WDM (wavelength multiplex) coupler 13 Rare earth doped fiber 14 Amplifier output terminal 15 Excitation laser 16 Excitation laser drive circuit 23 First signal detection circuit 24 Second signal detection circuit 25 AND circuit (decision section) 50 Detection section

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication H04B 10/17

Claims (5)

(57) [Claims] 1. A main optical signal that is used as a repeater of an optical fiber communication system and carries a main information signal that represents communication information, and a fault monitor for superimposing the main optical signal on the main optical signal. An optical fiber amplifier for receiving an input optical signal having a sub-optical signal carrying one of a sub-information signal for use and a sub-information signal for indicating a fault section of the system, wherein the input optical signal A first coupler input terminal for receiving
An optical coupler (12) having a coupler input terminal for outputting the input optical signal as a coupler output optical signal; and amplifying and amplifying the coupler output optical signal connected to the optical coupler. Rare-earth-doped fiber that outputs the generated optical signal (13)
And an optical branching circuit (1) which is connected to the rare earth-doped fiber, branches the amplified optical signal into first and second branched optical signals, and outputs the first branched optical signal as an output optical signal. An opto-electric conversion means (2) connected to the optical branch circuit for converting the second branch optical signal into an electric signal;
A detecting means (50) which is connected to the opto-electric converting means, detects that neither the fault monitoring sub-information signal nor the fault section indicating sub-information signal exists in the electric signal, and outputs a detection signal; A sub information signal which is connected to the detecting means and which, in response to the detection signal, generates the fault section indicating sub information signal having a natural frequency assigned to the optical fiber amplifier in order to indicate the fault section. Generating means (7); which is connected to the sub information signal generating means and the second coupler input terminal to generate a new sub optical signal for carrying the fault section indicating sub information signal, and to generate the new sub optical signal. Secondary optical signal generating means (15 and 16) for supplying an optical signal to the second coupler input terminal, wherein the optical coupler has the new optical signal supplied to the second coupler input terminal. A sub optical signal is input Combining the input optical signal and the new sub-optical signal in a state of being superimposed on the optical signal,
An optical fiber amplifier, which outputs a combined optical signal as an optical signal output from the coupler. 2. The optical fiber amplifier according to claim 1, wherein the optical coupler is a wavelength division multiplexer. 3. The main optical signal is pulse-modulated with the main information signal having a predetermined bit rate, and each of the sub optical signals has a low frequency slower than the main information signal, and the fault monitoring sub information signal and the sub information signal. Amplitude modulation is performed on one of the fault section indicating sub information signal, and the fault section indicating sub information signal has a frequency selected from a frequency band different from the frequency of the fault monitoring sub information signal. However, the sub-information signal generating means, in response to the detection signal,
The sub-interval signal for generating the fault section having the natural frequency included in the frequency band is generated, and the sub-optical signal generating means is the new sub-optical signal amplitude-modulated by the sub-information signal for fault section instruction. The optical fiber amplifier according to claim 1, wherein: 4. The first detecting / judging means (3 and 4) connected to the photoelectric conversion means, and detecting / judging that the faulty section indicating sub-information signal does not exist in the electric signal. 4) and; when connected to the photoelectric conversion means and the first detection / judgment means and the first detection / judgment means detects / judges that the faulty section indicating sub-information signal does not exist Detecting that the fault monitoring sub-information signal does not exist in the electrical signal,
The optical fiber amplifier according to claim 1, further comprising: second detection / determination means (5 and 6) for determining and outputting the detection signal. 5. A first signal detection circuit (23), said detection means being connected to said photoelectric conversion means and detecting the absence of said faulty section indicating sub-information signal in said electrical signal. A second signal detection circuit (24) connected to the opto-electric conversion means and detecting that the fault monitoring sub-information signal does not exist in the electrical signal.
And; connected to the first and second signal detection circuits,
When the first signal detection circuit detects that the sub-information signal for fault section indication does not exist and when the second signal detection circuit detects that the sub-information signal for fault monitoring does not exist, Judging means for outputting a detection signal (2
5. The optical fiber amplifier according to claim 1, which has 5) and 5;