JP5832418B2 - Optical amplifier and optical transmission system - Google Patents

Description

  The present invention relates to an optical amplifier having an automatic gain control (hereinafter referred to as “AGC”) circuit for controlling the output level of an optical signal and an optical transmission system using the optical amplifier.

  In the related optical amplifier, for example, as shown in FIG. 5, the optical input power and the optical output power of an optical fiber amplifier (OFA) 11 provided on the optical fiber 10 are branched by optical couplers 12 and 13, respectively. (PD) 14 and 15 convert the optical power into an electric signal, and the current of the pump laser diode (P-LD) 16 is supplied from the AGC circuit 17 so that the ratio (gain) of the power always becomes a desired value. By changing the gain, the gain of the OFA 11 is automatically controlled. As a result, it is possible to obtain a stable output light level at a constant value at an input light level within a certain range. This optical amplifier has been used when the output light level from the optical amplifier needs to be constant for system design, such as the FM batch conversion type optical video distribution system described in Non-Patent Document 1, for example.

  In this gain control of the optical amplifier, when an optical transmission line on the input side of the optical amplifier or an input side device has some trouble, and the input light level to the OFA 11 is lowered, the current of the pumping laser 16 is changed by the AGC circuit 17. The absolute rating may be exceeded and a failure of the OFA 11 may be induced. In order to avoid this, when the input light level is lowered to some extent, the current of the P-LD 16 is stopped and the optical output of the OFA 11 is also turned off.

  When the related optical amplifier described above is applied to an optical transmission system, the input optical level is lowered due to an abnormality in the optical transmission path or a failure of the host device, thereby turning off the optical output of the optical amplifier and causing a service interruption. In order to avoid this, service is stabilized by providing a detour route as a network configuration, taking a redundant configuration for the device, and selecting a normal system using an optical switch (SW). I was looking.

Shimoha et al., "Examination of optical repeater network design parameters in FM batch conversion type optical video distribution system", IEICE General Conference Proceedings 2010_Communications (2), 389 (2010)

  In the related technology, if the network does not have a redundant configuration, a decrease in the input optical level to the optical amplifier is directly connected to a service interruption. Moreover, when taking a redundant configuration as a network, there is a problem that the equipment cost increases.

  The present invention has been made in view of the above-mentioned problems. When the input signal of the optical amplifier is not completely disconnected due to an abnormality in the optical transmission path or a failure of the host device, the service is reduced. It is an object of the present invention to provide an optical amplifier capable of constructing a network at low cost while continuing the above, and an optical transmission system using the optical amplifier.

  For example, consider a case where an optical amplifier is installed in a station and an optical signal is distributed to a plurality of subscribers at different distances. In such a case, when the input light level to the optical amplifier is lowered to outside the normal operating range due to the above-described cause, the quality of the optical signal is deteriorated as compared with the case where it is in the normal operating range. At this time, if a certain level of output light level can be secured from the optical amplifier, a reception failure occurs in the subscriber farthest from the station, but the distance to the subscriber near the station is small. There is a case where the service can be continued without the occurrence of a failure as much as possible. Thus, it is a problem to be solved by the present invention to minimize the influence on the service even when the input level to the optical amplifier is lowered.

The optical amplifier of the present invention is
An optical amplifier for amplifying the input light;
A variable amplification control unit for controlling the gain of the optical amplification unit according to the output light level from the optical amplification unit;
A fixed amplification control unit for making the gain of the optical amplification unit constant;
When the input light level is less than the first threshold, which is the minimum value of the input light level that is the operation guarantee range of the optical amplifier, or less than the first threshold, the fixed amplification controller is operated, and the input light level A control selection unit that operates the fluctuation amplification control unit when is greater than or equal to the first threshold or exceeds the first threshold;
With
It is inserted into an optical fiber used for transmitting a section from the station building to the plurality of subscriber homes in an optical transmission system in which the office building and a plurality of subscriber homes are connected by optical fibers.

The optical transmission system of the present invention is
Are connected by the central office and a plurality of subscriber premises is optical fiber, after converting the plurality of analog signals into FM signals, an optical transmission system for transmitting FM batch conversion type optical analog signal where the optical carrier intensity-modulated by the optical fiber Because
The optical amplifier of the present invention is inserted in the optical fiber used for transmitting the section from the station building to the plurality of subscriber houses .

The control method of the optical amplifier of the present invention includes:
In an optical transmission system in which a station building and a plurality of subscriber houses are connected by an optical fiber, it is inserted into an optical fiber used to transmit a section from the station building to the plurality of subscriber houses, and amplifies input light. An optical amplifier control method comprising:

A determination procedure for determining whether the input light level is less than a first threshold value or less than or equal to the first threshold value;
When the input light level is equal to or higher than the first threshold value that is the minimum value of the input light level, which is the operation guarantee range of the optical amplification unit, or exceeds the first threshold value, the gain of the optical amplifier is controlled according to the output light level. And
A control procedure for making the gain of the optical amplifier constant when the input light level is less than the first threshold value or less than the first threshold value;
Have

  The present invention sets the first threshold value to a value that is not completely interrupted by the input signal of the optical amplifier but is reduced from the normal operating range, thereby temporarily or constantly reducing the input light level by a certain amount. In this case, it is possible to continue the service in a state where a certain quality is ensured. Therefore, the present invention uses an optical amplifier capable of constructing a network at low cost while continuing service when the input signal of the optical amplifier is not completely interrupted but falls from the normal operating range, and the optical amplifier. An optical transmission system can be provided.

The control selection unit included in the optical amplifier according to the present invention is configured so that, when the fixed amplification control unit is operating, when the second threshold value is greater than the first threshold value or exceeds the second threshold value, The fluctuation amplification control unit may be operated.
According to the present invention, when the input light level fluctuates up and down across the first threshold value in a short time, it is possible to prevent the control state of the optical amplifier from fluctuating frequently.

The optical amplifier of the present invention further includes an amplification stop control unit that stops the operation of the optical amplification unit, and the control selection unit is smaller than the first threshold value while the fixed increase control unit is operating. The amplification stop control unit may be operated when it becomes less than the third threshold.
According to the present invention, when the input light level to the optical amplifier falls below the third threshold value, that is, when almost no input light level is input, the optical amplifier can be stopped. Thereby, this invention can reduce unnecessary power consumption.

The optical amplifier of the present invention may include an output unit that outputs which one of the variable amplification control unit, the fixed amplification control unit, and the amplification stop control unit is operated.
Since the present invention includes an output unit, it is possible to specify a failure factor and repair a defective portion.

  The above inventions can be combined as much as possible.

  According to the present invention, when an input signal of an optical amplifier is not completely disconnected but falls from a normal operating range, an optical amplifier capable of constructing a network at low cost while continuing service, and the optical amplifier are used. An optical transmission system can be provided.

An example of the structure of the optical amplifier which concerns on this embodiment is shown. An example of the relationship between the OFA input level and the optical gain is shown. It is a flowchart for demonstrating the 1st example of control operation of an optical amplifier. It is a flowchart for demonstrating the 2nd example of control operation of an optical amplifier. An example of the structure of a related optical amplifier is shown.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

  FIG. 1 is a block diagram showing an example of an optical amplifier according to the present invention. The optical amplifier shown in this embodiment is similar to the related optical amplifier shown in FIG. 5, the optical fiber 10, the OFA 11 corresponding to the optical amplification unit, the optical coupler 12, the optical coupler 13, the PD 14, the PD 15, the P-LD 16, In addition to the AGC circuit 17 corresponding to the variable amplification control unit, the fixed amplification circuit 18 corresponds to the fixed amplification control unit and is set to operate so as to keep the gain of the optical amplifier constant. The control selection unit 19 selects whether control is performed, and an amplification stop circuit 20 corresponding to an amplification stop control unit for stopping optical amplification. As the fixed amplification control unit, there is a method of setting the operation so as to be automatic current control in which the drive current of the P-LD 16 is constant.

The control selecting unit 19, the threshold value of the input light level _{P IN} to OFA11 detected by PD14 has been set. In this embodiment, as shown in FIG. 2, for example, the input light level P1 is set to the first threshold value of the present invention, and the input light level P2 is set to the second threshold value of the present invention. Is set to the third threshold value. Control selecting section 19, when the input light level _{P IN} is above P1 are detected by PD14, the control current of the excitation laser 16 such that the output light level by the AGC circuit 17 is constant (P-LD 16) Let

Next, the control operation of this optical amplifier will be described based on the control state transition flowchart of FIG. In the figure, the control selecting unit 19, monitors the input light level _{P IN} detected by the PD 14 (S1), the input light level _{P IN} that the monitor determines whether a threshold value P1 or more (S2).

Here, when the input light level _PIN is equal to or higher than the threshold value P1, the control selection unit 19 determines that the input light level _PIN is within the operation guarantee range (S3), selects the AGC circuit 17 and performs excitation. The laser 16 (P-LD 16) is controlled (S4). The selected AGC circuit 17 controls the drive current of the P-LD 16 from the output monitor information from the PD 15 so that the output light level P _OUT always becomes a constant value.

If the input light level _PIN monitored in S2 is less than the threshold value P1, it is determined whether the input light level _PIN is less than the threshold value P3 (S5).
In the case of P3 or more, the control selection unit 19 determines that the input light level _PIN is within the range of the threshold values P1 to P3 (S6), selects the fixed amplifier circuit 18, and controls the excitation laser 16 (P-LD16). (S7). The selected fixed amplifier circuit 18 controls the drive current of the P-LD 16 so that the gain of the optical amplifier becomes constant.

If the input light level _PIN monitored in S5 is less than the threshold value P3, the control selection unit 19 determines that the light input level _PIN is less than the threshold value P3 (S9) and selects the amplification stop circuit 20 (S10). ) To stop the drive current of the excitation laser 16 (P-LD 16).

After the transition to S7 or S10, it is always monitored whether or not the input light level _PIN becomes equal to or higher than the threshold value P2 over time. If the input light level _PIN changes to the threshold value P2 or higher, the determination of S2 is sequentially performed. Moreover, when the determination of the threshold value P2 or more is No in S8, the process proceeds to S5.

In FIG. 3, after the transition to S10, only the determination of whether or not the threshold value P2 is greater than or equal to the threshold value P2 is performed in S11. However, if S11 is No as shown in FIG. It is determined whether or not it is P3 or higher (S12), and if an input light level _PIN equal to or higher than the threshold value P3 is confirmed, a flow transitioning to S7 can be added.

  In the present embodiment, the fixed amplifier circuit 18 is selected when it is less than the threshold value P1, and the AGC circuit 17 is selected when it is greater than or equal to the threshold value P1, but the present invention is not limited to this. For example, the configuration may be such that the fixed amplifier circuit 18 is selected when the threshold P1 or less, and the AGC circuit 17 is selected when the threshold P1 is exceeded. In the present embodiment, the AGC circuit 17 is selected when the threshold value P2 is greater than or equal to the threshold value P2, but the AGC circuit 17 may be selected when the threshold value P2 is exceeded.

  Further, by displaying or notifying the control state of the optical amplifier of the present invention, it is possible to investigate the fault location and implement countermeasures before the influence becomes large in the control state other than the automatic gain control.

  Furthermore, the optical amplifier of the present invention is used in an optical transmission system in which a plurality of analog signals are converted into FM (Frequency Modulation) signals, and then FM batch-converted optical analog signals obtained by intensity-modulating the optical carrier are transmitted by optical fibers. it can. For example, in the present system, the optical amplifier according to the present invention is inserted into an optical amplifier used for transmitting a section from a station building to a plurality of subscriber premises where a redundant configuration could not be obtained due to cost problems. . As a result, the system downtime when the input light level to the optical amplifier is reduced due to a failure of the host device of the optical amplifier, etc. can be shortened or the range of the affected area can be reduced more than before. Can do.

  The present invention can be applied to the information communication industry.

10: Optical fiber 11: OFA
12: Optical coupler 13: Optical coupler 14: PD (optical input monitor PD)
15: PD (light output monitor PD)
16: P-LD (excitation laser)
17: AGC circuit 18: Fixed amplifier circuit 19: Control selection unit 20: Amplification stop circuit 21: Control selection state notification / display unit

Claims (7)

An optical amplifier for amplifying the input light;
A variable amplification control unit for controlling the gain of the optical amplification unit according to the output light level from the optical amplification unit;
A fixed amplification control unit for making the gain of the optical amplification unit constant;
When the input light level is less than the first threshold, which is the minimum value of the input light level that is the operation guarantee range of the optical amplifier, or less than the first threshold, the fixed amplification controller is operated, and the input light level A control selection unit that operates the fluctuation amplification control unit when is greater than or equal to the first threshold or exceeds the first threshold;
With
Inserted into an optical fiber used for transmitting a section from the station building to the plurality of subscriber houses in an optical transmission system in which the station building and a plurality of subscriber houses are connected by optical fibers;
Optical amplifier.
The control selection unit operates the variable amplification control unit when the fixed amplification control unit is operated, when the second threshold value is larger than the first threshold value or exceeds the second threshold value. The optical amplifier according to claim 1.
An amplification stop control unit for stopping the operation of the optical amplification unit;
The control selection unit operates the amplification stop control unit when the fixed increase control unit is operated and when the control selection unit becomes less than a third threshold value smaller than the first threshold value. The optical amplifier according to claim 1 or 2.
4. The light according to claim 1, further comprising: an output unit that outputs which of the variable amplification control unit, the fixed amplification control unit, and the amplification stop control unit is operated. amplifier.
An optical transmission system in which a central office and a plurality of subscriber houses are connected by an optical fiber, and after a plurality of analog signals are converted into FM signals, an FM batch conversion type optical analog signal in which an optical carrier wave is intensity-modulated is transmitted by the optical fiber. Because
The optical transmission according to any one of claims 1 to 4, wherein an optical amplifier according to any one of claims 1 to 4 is inserted in the optical fiber used for transmitting a section from the station building to the plurality of subscriber houses. system.
In an optical transmission system in which a station building and a plurality of subscriber houses are connected by an optical fiber, it is inserted into an optical fiber used to transmit a section from the station building to the plurality of subscriber houses, and amplifies input light. An optical amplifier control method comprising:
A determination procedure for determining whether or not the input light level is less than or equal to the first threshold that is the minimum value of the input light level that is the operation guarantee range of the optical amplification unit ;
When the input light level is equal to or higher than a predetermined first threshold value or exceeds the first threshold value, the gain of the optical amplifier is controlled according to the output light level;
A control procedure for making the gain of the optical amplifier constant when the input light level is less than the first threshold value or less than the first threshold value;
An optical amplifier control method comprising:
In the determination procedure, it is determined whether the input light level is less than a third threshold value that is smaller than the first threshold value;
7. The method of controlling an optical amplifier according to claim 6, wherein the operation of the optical amplifier is stopped when the control procedure becomes less than the third threshold value.

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