JP2011097648A - Optical transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmitter for preventing system down caused by Brillouin scattering. <P>SOLUTION: The optical transmitter 13 is incorporated in an optical transmission system that converts an electrical signal into an optical signal to transmit it through an optical fiber line. The optical transmitter 13 includes: an exciting laser 69 which excites an optical signal configured as an optical amplifier 60 for amplifying an optical signal; and an amplification control section 74 for acquiring a first optical signal and a second optical signal different from the first optical signal, the first and second optical signals being transmitted in the optical transmission system, and controlling the exciting laser 69 based on a level of the first optical signal and a level of the second optical signal acquired, to control the level of an optical signal into so as not to incur Brillouin scattering caused when the optical signal is input to the optical fiber line. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical transmission apparatus incorporated in an optical transmission system that converts an electrical signal into an optical signal and transmits the optical signal via an optical fiber line.

  2. Description of the Related Art Conventionally, a CATV system for a plurality of dwelling units such as an apartment house has been widely used. In general, the CATV system modulates and amplifies an RF signal received via an antenna, transmits the amplified RF signal via a transmission line, demodulates it at a receiver, and outputs it (for example, , See Patent Document 1).

  In particular, in recent years, with the progress of optical communication technology, optical transmission systems using optical cables are being introduced. According to this optical transmission system, relayless transmission of about several tens of kilometers can be performed, so that the transmission system can be easily widened. This optical transmission system is generally configured by connecting an optical transmitter and an optical amplifier arranged on the center side and an optical receiver arranged on the system manager side via an optical cable. Then, the optical transmitter converts the RF signal into an optical signal and transmits the optical signal. The optical amplifier amplifies the optical signal, and transmits the optical signal to the optical receiver via the long-distance transmission path. In this optical receiver, an optical signal is converted into an RF signal and output to a receiving terminal such as a TV receiver.

  Here, as one of the obstacle factors in such an optical transmission system, pump brilliant scattering (S B S: S t i m u l a te d B r i l l o u i n S c a t e r i ng, hereinafter referred to as brilliant scattering) is known. This brilliant scattering is caused by the interaction between signal light and brilliant scattered light. When this brilliant scattering occurs, the optical signal is reflected and incident on the upstream side, so that the level of the optical signal that can be input to the optical cable. Is limited, and may cause a malfunction of the optical transmission system. For this reason, the conventional optical transmission system detects the presence or level of brilliant scattering and has an automatic cutoff function that stops the optical transmission system when brilliant scattering occurs or when the level exceeds a predetermined level. It was provided.

JP 2002-101401 A

  However, when the optical transmission system is stopped using the automatic shut-off function as in the prior art, it is not preferable because it takes time to restore the optical transmission system. In particular, in a broadcasting system that needs to perform emergency broadcasting, there has been a demand for improving the reliability of the system by avoiding a situation that causes the system to stop.

The present invention has been made in view of the above, and an object of the present invention is to provide an optical transmission apparatus that can avoid a system stop due to brilliant scattering.

  In order to solve the above-described problems and achieve the object, the optical transmission device according to claim 1 is an optical transmission incorporated in an optical transmission system that converts an electrical signal into an optical signal and transmits the optical signal through an optical fiber line. An optical amplifier configured to amplify the optical signal, an excitation light source for exciting the optical signal, the optical signal transmitted in the optical transmission system, the first optical signal; By acquiring a second optical signal different from the first optical signal and controlling the excitation light source based on the acquired first optical signal level and second optical signal level, Anti-scattering means for controlling the level of the optical signal to a level at which no Brilliant scattering occurs when the optical signal is input to the optical fiber line.

  An optical transmission device according to claim 2 stores a reference value for a combination of the level of the first optical signal and the level of the second optical signal in the optical transmission device according to claim 1. Storage means, wherein the anti-scattering means acquires the first optical signal and the second optical signal, and a combination of the level of the acquired first optical signal and the level of the second optical signal Is obtained from the storage means, and the excitation light source is controlled based on the obtained reference value, whereby the level of the optical signal is controlled to a level at which the Brillouin scattering does not occur.

  An optical transmission device according to claim 3 is the optical transmission device according to claim 2, wherein the optical signal transmitted in the optical transmission system is input to the pumping light source. Level control means for controlling the optical signal, and the scattering preventing means controls the level control means so that the level of the third optical signal satisfies the reference value, thereby adjusting the level of the optical signal. The level is controlled so that brilliant scattering does not occur.

  The optical transmission device according to claim 4 is the optical transmission device according to any one of claims 1 to 3, wherein the first optical signal is an optical signal input to the optical amplifier. .

  The optical transmission device according to claim 5 is the optical transmission device according to any one of claims 1 to 4, wherein the second optical signal is output from the optical amplifier and reflected by the optical amplifier. Optical signal.

  According to the present invention, since the predetermined operation for suppressing the brilliant scattering is automatically performed, the output level of the optical transmitter or the optical amplifier is automatically controlled so that the level of the optical signal is set to a level at which brilliant scattering does not occur. Since it can be adjusted, the reliability of the optical transmission system can be improved.

  In addition, according to the present invention, since the level of the optical signal is controlled to a level at which brilliant scattering does not occur, the brilliant scattering can be automatically suppressed, and a situation in which the optical transmission system is stopped can be automatically avoided. The reliability of the transmission system can be improved.

  Further, according to the present invention, by adjusting the input level to the pumping light source of the optical amplifier, it is possible to automatically suppress brilliant scattering, and it is possible to automatically avoid a situation where the optical transmission system is stopped, and to transmit the optical signal. The reliability of the system can be improved.

It is a block diagram which shows the structure of the optical transmission system which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of an optical receiver. 6 is a block diagram showing a configuration of an optical transmitter according to a second embodiment. FIG. 6 is a block diagram illustrating a configuration of an optical transmitter according to Embodiment 3. FIG. It is a flowchart of the control processing by a transmission control part. FIG. 6 is a block diagram illustrating a configuration of an optical amplifier according to a fourth embodiment.

  Hereinafter, embodiments of an optical transmission apparatus according to the present invention will be described in detail with reference to the accompanying drawings. First, [I] the basic concept common to each embodiment was explained, then [II] the specific contents of each embodiment were explained, and [III] finally, a modification to each embodiment was explained. To do. However, the present invention is not limited by these embodiments.

[I] Basic concept common to the embodiments First, the basic concept common to the embodiments will be described. Each of the embodiments generally relates to an optical transmission device incorporated in an optical transmission system that converts an electrical signal into an optical signal and transmits the optical signal via an optical fiber line. Here, examples of the optical transmission apparatus include an optical transmitter that converts an electrical signal into an optical signal and transmits the optical signal, and an optical amplifier that amplifies the optical signal. The first to third embodiments relate to an optical transmitter, and the fourth embodiment relates to an optical amplifier.

  In these optical transmitters and optical amplifiers, a predetermined operation for preventing the occurrence of brilliant scattering is performed. This operation is roughly classified into an output operation related to the possibility of occurrence of brilliant scattering and a control operation for reducing brilliant scattering. In the case of the output operation, for example, the possibility of occurrence of brilliant scattering is determined, and the determination result is displayed to notify the possibility to the system administrator. Upon receiving this, the system administrator can perform control to avoid the brilliant scattering before the brilliant scattering occurs and the system is stopped. On the other hand, in the case of a control operation, for example, by monitoring a predetermined characteristic value in an electric signal or an optical signal, the possibility of occurrence of brilliant scattering is determined, and an electric signal in an optical transmitter or optical amplifier is determined according to the result. And controlling the input value of the optical signal can prevent brilliant scattering or reduce the level of brilliant scattering. Accordingly, it is possible to prevent a situation in which the system is stopped due to Brillouin scattering.

  In such an output operation or feedback operation, various values can be given as the characteristic values of the electrical signal and the optical signal acquired as the operation reference. That is, Brillouin scattering is proportional to the length of the optical cable, the level (power) of the optical signal, and the sharpness of the wavelength of the optical signal (ratio of the level to the length of the wavelength), and the modulation degree (amplitude) of the optical signal. It is known to occur in inverse proportion to Therefore, in each embodiment, the output operation or the feedback operation is performed by detecting at least one of parameters related to the occurrence of the Brillouin scattering and its level.

[II] Specific Contents of Each Embodiment The specific contents of each embodiment will be sequentially described in detail below with reference to the accompanying drawings.

[Embodiment 1]
First, specific contents of the first embodiment will be described in detail. The first embodiment is a form in which display regarding the possibility of occurrence of brilliant scattering is performed in an optical transmitter.

(Basic configuration of optical transmission system)
First, the basic configuration of the optical transmission system according to Embodiment 1 will be described. FIG. 1 is a block diagram showing the configuration of the optical transmission system according to the first embodiment. The optical transmission system 1 includes a UHF / VHF antenna 10, a BS / CS antenna 11, a head end 12, an optical transmitter 13, an optical amplifier 14, an optical splitter 15, an optical receiver 16, and a TV receiver 17 that is a receiver. Are connected via a coaxial cable line 18 and an optical fiber line 19 as shown in the figure.

  Then, an RF signal (television channel signal) wirelessly transmitted from a broadcast station (not shown) or its relay station is received by the UHF / VHF antenna 10 or the BS / CS antenna 11 of the head end 12 arranged on the center side, This RF signal is transmitted to the optical transmitter 13 via the coaxial cable line 18. The optical transmitter 13 E / O converts this RF signal into an optical signal, and transmits this optical signal to the optical amplifier 14 via the optical fiber line 19. The optical amplifier 14 amplifies this optical signal and transmits it to the user side via an optical fiber line 19 laid over a long distance of about several kilometers. The optical splitter 15 distributes this optical signal to a required distribution system, and the optical signal distributed to each distribution system is O / E converted into an RF signal by the optical receiver 16, and this RF signal is converted into a coaxial cable line 18. Via the user's TV receiver 17.

(Basic configuration of the optical transmitter 13)
Next, the basic configuration of the optical transmitter 13 will be described. FIG. 2 is a block diagram showing the configuration of the optical receiver. The optical receiver 13 corresponds to the optical transmission device in the claims, and includes an input terminal 20, a separator 21, signal adjustment units 22, 23, a mixer 24, a laser diode (a semiconductor diode for CATV, hereinafter referred to as LD). 25, a laser controller 26, and an output terminal 27 are connected as shown in the figure.

  Then, the RF signal input to the input terminal 20 is distributed by the separator 21 into an RF signal in the CATV band (70 to 770 MHz) and an RF signal in the BS / CS band (1000 to 2602 MHz), respectively. 22 and 23 are individually input. The signal adjustment unit 22 adjusts the level of the RF signal in the CATV band. The signal adjustment unit 22 includes a gain controller (hereinafter referred to as GC) 22a, an amplifier 22b, a signal controller (hereinafter referred to as SC) 22c, and an amplifier 22d. The level is adjusted to a predetermined level and output. The signal adjustment unit 23 adjusts the level of the RF signal in the BS / CS band. The signal adjustment unit 23 includes a GC 23a, amplifiers 23b, SC23c, and an amplifier 23d, and outputs the RF signal after adjusting the level to a predetermined level. The RF signal output in this way is mixed by the mixer 24 and input to the LD 25. The LD 25 converts the RF signal into an optical signal by performing light emission driving by luminance modulation according to the amplitude level of the input RF signal, and corresponds to the electrical / optical converting means in the claims. Then, this optical signal is output to the subsequent stage via the output terminal 27.

  Next, the laser controller 26 will be described. The laser controller 26 is a driving means for the LD 25, and includes a temperature control unit (ATC: Auto Temperature Control) 26a, a power control unit (APC: Auto Power Control) 26b, a liquid crystal monitor 26c, and a transmission control unit 26d. Has been. The temperature control unit 26a operates the LD 25 by controlling the temperature of the LD 25 so that the temperature of the LD 25 becomes constant, thereby preventing a decrease in slope efficiency and an increase in the threshold current in the LD 25, thereby stably operating the LD 25. Let Specifically, the temperature control unit 26a includes a thermistor (not shown), and controls the current supplied to the LD 25 so that the temperature of the LD 25 detected by the thermistor falls within a predetermined range. The power control unit 26b energizes the LD 25 so that the output level of the optical signal of the LD 25 is constant, thereby maintaining the output level below the maximum rating of the optical transmitter 13 and protecting the LD 25. Stabilize the output level. Specifically, the power control unit 26b receives the monitor light from the LD 25 with a photodiode (not shown) and controls the operating current of the LD 25 so as to be inversely proportional to the output level of the photodiode, thereby feedback controlling the LD 25. To do. The liquid crystal monitor 26c displays the control state in the laser controller 26, and corresponds to the display means in the claims. The liquid crystal monitor 26c displays the status of the temperature control unit 26a and the power control unit 26b, for example. The transmission control unit 26d controls each unit of the laser controller 26, and corresponds to the conversion control means in the claims. The transmission control unit 26d includes, for example, a CPU (Central Processing Unit) and a control program that is interpreted and executed by the CPU.

(Brillouin scattering suppression structure)
Next, a structure for suppressing or preventing brilliant scattering will be described. As shown in FIG. 2, a duplexer 28 is provided on the upstream side of the LD 25 (between the mixer 24 and the LD 25), and a detector 29 is connected to the duplexer 28. Then, the RF signal demultiplexed by the demultiplexer 28 is input to the detector 29. The detector 29 is configured as a linear detector, for example, and outputs a DC voltage proportional to the execution voltage of the RF signal to the transmission control unit 26 d of the laser controller 26. In this transmission control unit 26d, the voltage value of the detector 29 that may cause brilliant scattering is stored in advance as a threshold value (reference value), and the transmission control unit 26d uses the voltage input from the detector 29 as the threshold value. To determine the possibility of occurrence of brilliant scattering. When brilliant scattering occurs (that is, when the voltage of the detector 29 is equal to or higher than the threshold value), the transmission control unit 26d displays that the brilliant scattering has occurred via the liquid crystal monitor 26c. That is, in the first embodiment, the transmission control unit 26d constitutes the scattering prevention means in the claims, the liquid crystal monitor 26c constitutes the determination result output means in the claims, and the detector 29 is claimed. The level detection means in the range is configured.

  As specific contents to be displayed on the liquid crystal monitor 26c in this way, for example, text indicating that brilliant scattering has occurred may be displayed, or a predetermined warning lamp indicating this may be blinked or lit. . By performing such a display, the system administrator can be notified of information relating to the occurrence of the Brillouin scattering, and the system administrator can prompt the system administrator to take action to avoid stopping the optical transmission system 1.

(Effect of Embodiment 1)
As described above, according to the first embodiment, it is possible to automatically notify the system administrator that brilliant scattering has occurred inside the optical transmitter, and therefore, the system management manages the action for avoiding the stop of the optical transmission system 1. Since the system administrator can take necessary measures in advance, the reliability of the optical transmission system 1 can be improved. Further, since the transmission control unit 26d as the conversion control unit is used as the scattering determination unit and the liquid crystal monitor 26c as the display unit is used as the determination result output unit, There is no need to provide a dedicated configuration for display, and the optical receiver 13 can be configured simply and inexpensively.

[Embodiment 2]
Next, the specific content of Embodiment 2 which concerns on this invention is demonstrated in detail. In the second embodiment, information on the possibility of occurrence of brilliant scattering is output from an optical transmitter to an external device. However, unless otherwise specified, the configuration is the same as that of the first embodiment, and the same components as those of the first embodiment are denoted by the same reference numerals as those used in the first embodiment, if necessary. To do.

  FIG. 3 is a block diagram showing a configuration of the optical transmitter according to the second embodiment. In the optical transmission system of the second embodiment, the optical receiver 30 of FIG. 3 is arranged instead of the optical transmitter 13 of the first embodiment. The optical receiver 30 is provided with a laser controller 31 instead of the laser controller 26 of the first embodiment. The laser controller 31 includes a temperature control unit 31a, a power control unit 31b, a liquid crystal monitor 31c, and a transmission control unit 31d.

  Each part of the laser controller 31 is configured in substantially the same way as each part having the same name in the laser controller 26 of the first embodiment. However, the transmission control unit 31d is provided with an SNMP agent 31e and this transmission. The control unit 31 d is connected to the SNMP manager 33 via the LAN network 32.

  The SNMP manager 33 monitors and manages the optical receiver 30 by SNMP (Simple Network Management Protocol) which is a network system monitoring protocol. For example, the SNMP manager 33 includes a personal computer and an SNMP manager program executed on the personal computer. It is configured. Further, the SNMP agent 31e is periodically called by polling or the like by the SNMP manager program, acquires the status information of the optical receiver 30, and transmits it to the SNMP manager program. Specifically, the SNMP manager program refers to a management information base (MIB) stored in itself and identifies an object ID assigned to necessary information (object). Then, this object ID is transmitted to the SNMP agent 31e via the LAN network 32.

  The SNMP agent 31e identifies the requested object by referring to the management information base stored in itself based on the transmitted object ID. Then, the SNMP agent 31e acquires the requested object and transmits it to the SNMP manager program. Here, the object acquired from the optical transmitter 30 can include any parameter that can be acquired via the transmission control unit 31d among the parameters related to the occurrence of the brilliant scattering and its level. For example, the level of the optical signal acquired through the detector 29 and the optical output level of the APC 31b can be included.

  In the SNMP manager 33, a parameter that can cause brilliant scattering is stored in advance as a threshold value (reference value), and the SNMP manager 33 compares the object acquired from the optical transmitter 30 with this threshold value, so that The presence or absence of scattering is determined. For example, this determination is performed by comparing the level of the optical signal acquired via the detector 29 with a predetermined reference level at which brilliant scattering can occur. Alternatively, since the RF power level from the detector 29 is proportional to the modulation degree of the optical signal, and the optical output level of the APC 31b is inversely proportional to the modulation degree of the optical signal, the level of the detector 29 and the APC 31b This determination is performed by determining the degree of modulation of the optical signal based on the optical output level of the optical signal and comparing the degree of modulation with a predetermined reference degree of modulation that can cause brilliant scattering. When brilliant scattering occurs (that is, when the level of the optical signal or the modulation degree of the optical signal is equal to or greater than the threshold value), the SNMP manager 33 indicates that the brilliant scattering has occurred via a liquid crystal monitor (not shown). indicate. That is, the SNMP manager 33 constitutes a scattering prevention unit, a determination result output unit, and an external device in the claims.

(Effect of Embodiment 2)
As described above, according to the second embodiment, it is possible to automatically notify the system administrator that the occurrence of brilliant scattering has occurred outside the optical transmitter. Therefore, an action for avoiding the stop of the optical transmission system 1 is performed. The system administrator can be automatically prompted and the system administrator can take necessary measures in advance, so that the reliability of the optical transmission system 1 can be improved. In particular, by outputting via an external device such as the SNMP manager 33, the occurrence of brilliant scattering can be notified to a system administrator located far away from the optical transmission system.

[Embodiment 3]
Next, specific contents of the third embodiment according to the present invention will be described in detail. The third embodiment is a mode in which dynamic control for suppressing brilliant scattering is performed in an optical transmitter. However, unless otherwise specified, the configuration is the same as that of the first embodiment, and the same components as those of the first embodiment are denoted by the same reference numerals as those used in the first embodiment, if necessary. To do.

  FIG. 4 is a block diagram showing the configuration of the optical transmitter according to the third embodiment. In the optical transmission system of the third embodiment, the optical receiver 40 of FIG. 4 is arranged instead of the optical transmitter 13 of the first embodiment. The optical receiver 40 is provided with a laser controller 41 instead of the laser controller 26 of the first embodiment. The laser controller 41 includes a temperature control unit 41a, a power control unit 41b, a liquid crystal monitor 41c, and a transmission control unit 41d.

  Each part of the laser controller 41 is configured in substantially the same manner as each part having the same name in the laser controller 26 of the first embodiment, but the transmission controller 41d is connected to the GCs 22a and 23a in addition to the detector 29. ing. Then, the transmission control unit 41d performs A / D conversion on the output of the detector 29 (the voltage of the RF signal demultiplexed by the demultiplexer 28 and output from the detector 29). Then, the A / D conversion value is compared with a predetermined aptitude value (reference value) stored in advance in the transmission control unit 41d, and a control signal corresponding to the comparison result is D / A converted to obtain a GC 22a, 23a. To adjust the level of the RF signal input to the LD 25 to a level that suppresses brilliant scattering. That is, the transmission control unit 41d corresponds to the scattering prevention unit in the claims, and the GCs 22a and 23a correspond to the level control unit in the claims.

  Such a control process will be described more specifically. FIG. 5 is a flowchart of control processing by the transmission control unit. After the optical transmitter 40 is activated, the transmission control unit 41d initializes the D / A values input to the GCs 22a and 23a with the initial value (minimum value 0) in order to avoid over-input to the LD 25 (Step S1). SA-1). Then, an A / D conversion value of the RF signal input from the detector 29 is acquired (step SA-2), and this A / D conversion value is compared with a predetermined aptitude value (steps SA-3 and SA-4). ). This suitability value is a value for setting the level of the RF signal input to the LD 25 to a level that suppresses brilliant scattering, and the specific value of this suitability value can vary depending on individual differences in the LD 25. The optical transmitter 40 is determined by measurement before shipment and set in the transmission control unit 41d. When the A / D conversion value is smaller than the appropriate value (Yes at Step SA-3), the transmission control unit 41d increments the A / D conversion value by a predetermined value (for example, 1) (Step SA- 5) The A / D conversion value after the increment is D / A converted and output to the GCs 22a and 23a. As a result, the outputs of the GCs 22a and 23a are increased, and the RF signal input to the LD 25 is increased. On the other hand, when the A / D conversion value is larger than the appropriate value (step SA-3, No, step SA-4, Yes), the transmission control unit 41d sets the A / D conversion value to a predetermined value (for example, 1). (Step SA-6), the A / D converted value after this subtraction is D / A converted and output to the GCs 22a and 23a. As a result, the outputs of the GCs 22a and 23a are lowered, and the RF signal input to the LD 25 is lowered. Thereafter, the transmission control unit 41d repeats the same processing to maintain the signal input to the LD 25 at an appropriate level and suppress brilliant scattering. Although a specific value is used as the suitability value here, the RF signal level may be adjusted so that it falls within the suitability range having a specific width.

(Effect of Embodiment 3)
As described above, according to the third embodiment, the feedback control is performed on the GCs 22a and 23a based on the level of the RF signal input to the LD 25, so that the level of the RF signal input to the LD 25 is automatically set to an appropriate value. Since it can be adjusted and brilliant scattering can be suppressed, a situation where the optical transmission system stops can be automatically avoided, and the reliability of the optical transmission system can be improved.

[Embodiment 4]
Next, the specific content of Embodiment 4 which concerns on this invention is demonstrated in detail. In the fourth embodiment, dynamic control for suppressing Brillouin scattering is performed in an optical amplifier rather than an optical transmitter. However, unless otherwise specified, the configuration is the same as that of the first embodiment, and the same components as those of the first embodiment are denoted by the same reference numerals as those used in the first embodiment, if necessary. To do.

  FIG. 6 is a block diagram showing a configuration of an optical amplifier according to the fourth embodiment. In the optical transmission system according to the fourth embodiment, the optical amplifier 60 of FIG. 6 is arranged instead of the optical amplifier 14 of the first embodiment. The optical amplifier 60 includes an input terminal 61, photocouplers 62 to 65, isolators 66 and 67, an erbium ion doped fiber (hereinafter referred to as EDF) 68, a pumping laser 69 as a pumping light source, and a photodiode (Photo Diode). Hereinafter, the PDs 70 to 72, the output terminal 73, and the amplification controller 74 are connected as shown in the figure.

  Then, the optical signal input from the input terminal 61 and the excitation light of the excitation laser 69 are incident on the EDF 68, whereby the optical signal is amplified by the induction amplification action of erbium (Er) ions in the EDF 68, and the output terminal The output is output via 73. The amplification control unit 74 includes a CPU and a program interpreted and executed on the CPU. The amplification control unit 74 performs A / D conversion on an optical signal immediately after output from the EDF 68 acquired through the photodiode 70, and The output level of the excitation laser 69 is determined according to the A / D conversion value. Then, the amplification control unit 74 determines a control signal corresponding to this output level so as to drive the excitation laser 69 at this output level, performs D / A conversion, and performs excitation using this D / A conversion value. By driving the laser 69, the output from the EDF 68 is controlled. That is, the amplification control unit 74 corresponds to the level control means in the claims. The isolators 66 and 67 block back-injection of backscattered light to each part.

  The amplification control unit 74 controls the level of the optical signal output from the optical amplifier 60 to a level at which brilliant scattering does not occur, and corresponds to the scattering preventing means in the claims. Specifically, the amplification control unit 74 acquires an optical signal input to the input terminal 61 and incident on the EDF 68 via the photodiode 71, and A / D converts this optical signal. Then, the amplification control unit 74 compares the A / D conversion value with a predetermined aptitude value (reference value) stored in advance in the amplification control unit 74, and the A / D conversion value exceeds the aptitude value. In this case, the output level of the excitation laser 69 is determined so as to lower the output level of the excitation laser 69. Then, the amplification control unit 74 determines a control signal corresponding to this output level so as to drive the excitation laser 69 at this output level, performs D / A conversion, and performs excitation using this D / A conversion value. The laser 69 is driven. By adjusting the amplification degree of the EDF 68 according to the input level of the optical signal in this way, brilliant scattering can be suppressed.

  In addition to the control based on the input level of the optical signal, the amplification control unit 74 performs control based on the reflection level from the optical cable on the rear stage side of the optical amplifier 60. Specifically, the amplification control unit 74 acquires the reflected light that is back incident on the output terminal 73 via the photodiode 72, and A / D converts the optical signal from the reflected light. Then, the amplification control unit 74 compares the A / D conversion value with a predetermined suitability value stored in advance in the amplification control unit 74, and if the A / D conversion value exceeds the suitability value, excitation is performed. The output level of the excitation laser 69 is determined so that the output level of the laser 69 is lowered. Then, the amplification control unit 74 determines a control signal corresponding to this output level so as to drive the excitation laser 69 at this output level, performs D / A conversion, and performs excitation using this D / A conversion value. The laser 69 is driven. Thus, by adjusting the amplification degree of the EDF 68 according to the reflection level, brilliant scattering can be suppressed.

As described above, the amplification controller 74 controls the output level of the excitation laser 69 based on the outputs from the three photodiodes 70 to 72. More specifically, the relationship between outputs from the photodiodes 70 to 72 will be described. The amplification control unit 74 first acquires two A / D conversion values for the outputs from the photodiodes 71 and 72. The amplification control unit 74 stores suitable A / D conversion values of the photodiode 70 for the combination of these two A / D conversion values in a table format or the like. The amplification control unit 74 stores the two acquired A / D conversion values. By referring to this table based on the A / D conversion value, an appropriate A / D conversion value of the photodiode 70 is determined. Then, the excitation laser 69 is driven so that the A / D conversion value for the output from the photodiode 70 becomes the appropriate A / D conversion value. As a result, when the level of the input optical signal detected via the photodiode 71 is high, or when the reflection level detected via the photodiode 72 increases (that is, when reflection occurs), The appropriate A / D conversion value of the photodiode 70 is lowered, and the output of the excitation laser 69 is lowered. Alternatively, the output level of the excitation laser 69 may be adjusted in consideration of only one of the level of the optical signal input to the input terminal and the level of the reflected light. For example, the level of the input optical signal detected via the photodiode 71 is irrelevant to the control of the pump laser 69, and when this level falls below the specified input level, the optical amplifier 6
0 may be shut down or the like.

(Effect of Embodiment 4)
As described above, according to the fourth embodiment, the amplification degree of the EDF 68 is adjusted according to the input level of the optical signal input to the input terminal, or is adjusted according to the level of the reflected light. By doing so, brilliant scattering can be suppressed, so that a situation where the optical transmission system stops can be automatically avoided, and the reliability of the optical transmission system can be improved.

[Modifications to Embodiment]
Although the embodiments of the present invention have been described above, the specific configuration and means of the present invention may be arbitrarily modified and improved within the scope of the technical idea of each invention described in the claims. Can do. Hereinafter, such a modification will be described.

(About problems to be solved and effects of the invention)
First, the problems to be solved by the invention and the effects of the invention are not limited to the above-described contents, and the present invention solves the problems not described above or has the effects not described above. There are also cases where only some of the described problems are solved or only some of the described effects are achieved. For example, even when the occurrence of brilliant scattering cannot be completely prevented, the problem of the present invention is achieved when the possibility of occurrence and the level at the time of occurrence can be slightly reduced as compared with the prior art.

(About mutual combination of each embodiment)
The configuration of each embodiment can be applied to other embodiments. For example, the optical amplifier according to the fourth embodiment may be further applied to the optical transmission system according to the first embodiment in addition to the optical transmitter according to the first embodiment.

(About judgment and control goals)
In the first and second embodiments, when brilliant scattering occurs, the fact is displayed and output. However, before the occurrence of brilliant scattering, the fact is output when the possibility increases. Alternatively, after the occurrence of brilliant scattering, the fact may be output when the level approaches a predetermined level that causes the optical transmission system to stop. That is, it is possible to output arbitrary information related to the possibility of occurrence of brilliant scattering. Similarly, in the third and fourth embodiments, the RF signal and the optical signal are adjusted so that brilliant scattering does not occur. However, even if brilliant scattering occurs, the level thereof is the same as that of the optical transmission system. The RF signal and the optical signal may be adjusted so as not to reach a predetermined level that causes a stop. Such a change can be easily made by adjusting a threshold value or aptitude value to be compared with an RF signal or an optical signal.

(About control means and output means)
In the first embodiment, information on the possibility of occurrence of brilliant scattering is output using the transmission controller of the laser controller and the liquid crystal monitor. However, dedicated control means and display means for performing this output are provided. May be. Further, as output means for outputting information on the possibility of occurrence of brilliant scattering, in addition to display means such as a liquid crystal monitor, audio output means and signal output means for outputting a transfer signal to an arbitrary external device are provided. It may be used.

  The present invention can be applied to an optical transmission system that converts an electrical signal into an optical signal and transmits the signal, and is useful for avoiding system stoppage due to Brillouin scattering.

(Appendix)
The optical transmission device according to attachment 1 is an optical transmission device incorporated in an optical transmission system that converts an electrical signal into an optical signal and transmits the optical signal via an optical fiber line, and the electrical signal transmitted in the optical transmission system Or an anti-scattering means that obtains an optical signal and performs a predetermined operation for suppressing brilliant scattering caused by the optical signal being input to the optical fiber line based on the electrical signal or the optical signal. And

  Further, in the optical transmission device according to appendix 2, in the present invention according to appendix 1, the scattering preventing unit compares the electrical signal or the optical signal with a predetermined reference value, and based on the comparison result, The possibility of occurrence of scattering is determined, and when it is determined that there is a possibility of occurrence of the Brillouin scattering, information on the possibility of occurrence of the scattering is output.

  The optical transmission device according to attachment 3 is configured as an optical transmitter that converts the electrical signal into the optical signal and transmits the optical signal in the invention according to attachment 2, and converts the electrical signal into the optical signal. Electrical / optical conversion means, level detection means for detecting the level of the electrical signal input to the electrical / optical conversion means, and determination result output means for outputting the determination result of the scattering determination means, The scattering prevention means determines the possibility of the occurrence of the Brillouin scattering by comparing the level of the electric signal detected by the level detection means with the predetermined reference value, and provides information on the possibility of the occurrence. It outputs through the said determination result output means, It is characterized by the above-mentioned.

Further, the optical transmission device according to appendix 4 includes, in the present invention according to appendix 3, conversion control means for controlling the electrical / optical conversion means, and display means for performing display regarding the control contents of the conversion control means. And the scattering determination means is constituted by the conversion control means, and the determination result output means is constituted by the display means.

  The optical transmission device according to appendix 5 is configured as an optical transmitter that converts the electrical signal into the optical signal and transmits the optical signal in the invention according to appendix 2, and converts the electrical signal into the optical signal. An electrical / optical converting means that detects the level of the electrical signal input to the electrical / optical converting means, and the scattering preventing means detects the level detected by the level detecting means. The possibility of the occurrence of the Brillouin scattering is determined by comparing the level of the electric signal with the predetermined reference value, and information regarding the possibility of the occurrence is connected to the optical transmission device via a predetermined network. Output via a predetermined external device.

  The optical transmission device according to attachment 6 includes level control means for controlling a level of the electric signal or the optical signal in the present invention according to attachment 1, wherein the scattering prevention means The level control means is controlled based on the level of the signal or the optical signal, thereby controlling the level of the electrical signal or the optical signal to a level at which the Brilliant scattering does not occur.

  The optical transmission device according to appendix 7 is configured as an optical transmitter that converts the electrical signal into the optical signal and transmits the optical signal in the invention according to appendix 6, and converts the electrical signal into the optical signal. The level control means controls the level of the electric signal input to the electric / optical conversion means, and the scattering prevention means is input to the electric / optical conversion means. Obtaining the electrical signal, and controlling the level control means based on the obtained level of the electrical signal, thereby controlling the level of the electrical signal to a level at which the Brilliant scattering does not occur. To do.

  Further, the present invention described in appendix 8 is configured as an optical amplifier that amplifies the optical signal in the present invention described in appendix 6, and includes an excitation light source that excites the optical signal. By acquiring an optical signal input to the pumping light source or an optical signal output from the optical amplifier and reflected by the optical amplifier, and controlling the pumping light source based on the level of the optical signal The level of the optical signal is controlled to a level at which the Brillouin scattering does not occur.

  The optical transmission apparatus according to the supplementary note automatically performs a predetermined operation for suppressing brilliant scattering, so that the possibility of occurrence of brilliant scattering is output to avoid stopping the optical transmission system. Can improve the reliability of the optical transmission system because the optical signal level can be adjusted to a level that does not cause brilliant scattering by automatically controlling the output level of the optical transmitter and optical amplifier. .

  In addition, when the optical transmission device according to the supplementary note determines that there is a possibility of occurrence of brilliant scattering, information on the possibility of the occurrence is output, so an action for avoiding the stop of the optical transmission system is performed. The system administrator can be automatically prompted, and the system administrator can take necessary measures in advance, so that the reliability of the optical transmission system can be improved.

  In addition, the optical transmission device according to the appendix automatically determines the possibility of occurrence of brilliant scattering in the optical transmitter and outputs the result to automatically cause the system administrator to take action to avoid the stop of the optical transmission system. Since the system administrator can take necessary measures in advance, the reliability of the optical transmission system can be improved.

  In addition, the optical transmission apparatus according to the supplementary note is configured such that the scattering determination unit is configured by the conversion control unit, and the determination result output unit is configured by the display unit. Therefore, the optical receiver can be configured easily and inexpensively.

  In addition, since the optical transmission device according to the supplementary information can output information on the possibility of occurrence of brilliant scattering via an external device, brilliant scattering can also occur for system administrators located far away from the optical transmission system. Since the system administrator can take necessary measures in advance, the reliability of the optical transmission system can be improved.

  Further, the optical transmission device according to the supplementary note controls the level of the electrical signal or optical signal to a level at which brilliant scattering does not occur, so that brilliant scattering can be automatically suppressed and a situation where the optical transmission system stops automatically. Therefore, the reliability of the optical transmission system can be improved.

  Further, the optical transmission device according to the supplementary note can automatically suppress the Brillouin scattering by adjusting the input level to the electrical / optical conversion means of the optical transmitter, and the situation where the optical transmission system stops automatically. This can be avoided and the reliability of the optical transmission system can be improved.

  In addition, the optical transmission device according to the supplementary note can automatically suppress brilliant scattering by adjusting the input level to the excitation light source of the optical amplifier, and can automatically avoid a situation where the optical transmission system stops, The reliability of the optical transmission system can be improved.

DESCRIPTION OF SYMBOLS 1 Optical transmission system 10 UHF antenna 11 BS / CS antenna 12 Head end 13, 30, 40 Optical transmitter 14 Optical amplifier 15 Optical splitter 16 Optical receiver 17 TV receiver 18 Coaxial cable line 19 Optical fiber line 20 Input terminal 21 Separator 22, 23 Signal adjustment unit 24 Mixer 25 Laser diode (LD)
26, 31, 41 Laser controller 26a, 31a, 41a Temperature controller 26b, 31b, 41b Power controller 26c, 31c, 41c Liquid crystal monitor 26d, 31d, 41d Transmission controller 27 Output terminal 28 Distributor 29 Detector 31e SNMP agent 32 LAN network 33 SNMP manager

Claims (5)

An optical transmission device incorporated in an optical transmission system that converts an electrical signal into an optical signal and transmits the optical signal via an optical fiber line,
Configured as an optical amplifier for amplifying the optical signal;
An excitation light source for exciting the optical signal;
The optical signal transmitted in the optical transmission system, the first optical signal and a second optical signal different from the first optical signal are acquired, and the acquired first optical signal By controlling the excitation light source based on the level and the level of the second optical signal, the level of the optical signal is controlled to a level at which brilliant scattering due to the input of the optical signal to the optical fiber line does not occur Anti-scattering means
Optical transmission device. Storage means for storing a reference value for a combination of the level of the first optical signal and the level of the second optical signal;
The scattering preventing means is
Obtaining the first optical signal and the second optical signal, obtaining a reference value for the combination of the obtained first optical signal level and second optical signal level from the storage means; By controlling the excitation light source based on the acquired reference value, the level of the optical signal is controlled to a level at which the Brillouin scattering does not occur.
The optical transmission device according to claim 1. Level control means for controlling a third optical signal which is the optical signal transmitted in the optical transmission system and input to the excitation light source,
The scattering preventing means is
By controlling the level control means so that the level of the third optical signal satisfies the reference value, the level of the optical signal is controlled to a level at which the Brilliant scattering does not occur.
The optical transmission device according to claim 2. The first optical signal is an optical signal input to the optical amplifier.
The optical transmission device according to any one of claims 1 to 3. The second optical signal is an optical signal output from the optical amplifier and reflected by the optical amplifier.
The optical transmission device according to any one of claims 1 to 4.

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