JP2004125711A - Method for determining connection status of light connector and excitation light source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine the connection status of a light connector including its optical connection status. <P>SOLUTION: The method determines the connection status of the light connector connecting an LD module and a light coupler combining signal light output from the module with an amplification light fiber based on the intensity of light reflected from the light connector. The excitation light source has a monitor generating a current corresponding to the intensity of the light reflected from the light connector connecting the LD module and a light coupler combining the excitation light output from the LD module with the amplification light fiber, a current voltage converter outputting a voltage corresponding to the current, and a control determinater determining the connection state of the optical connector based on the output voltage. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an excitation light source for an optical fiber amplifier.
[0002]
[Prior art]
The pumping light source used in the optical fiber type amplifier is at least a laser diode module having a laser diode that generates pumping light, and an amplifying light through which signal light, which is a target of amplifying the pumping light output from the module, is propagated. An optical coupler that multiplexes with the fiber, and the optical coupler is connected to the laser diode module via an optical fiber. Specifically, the output optical fiber on the laser diode module side and the input optical fiber on the optical coupler side are fusion-spliced or connected by an optical connector. In particular, when a new laser diode module is added, the latter is often used in order to save the time and effort of the fusion work. However, improper connection between the optical connectors adversely affects the existing laser diode module and causes leakage of the excitation light to the eyes of the operator. Therefore, when the optical connectors are properly connected to each other, an optical connector that emits a clicking sound is used so that a worker can check the connection state of the optical connector by sound or touch.
[0003]
[Problems to be solved by the invention]
The conventional excitation light source in which the output optical fiber on the laser diode module side and the input optical fiber on the optical coupler side are connected by an optical connector has the following problems.
(1) If an optical connector that emits a confirmation sound is used, the structural connection state of the optical connector can be confirmed, but it is not possible to confirm the optical connection state such as optical axis shift or burnt end face.
(2) Even if an optical connector that generates a confirmation sound is used, an accident such as driving the laser diode module without connecting the optical connector cannot be prevented.
[0004]
[Means for Solving the Problems]
The present invention has been made in view of the above problems, and has been made to solve the above problems by making it possible to determine the connection state of the optical connector based on the intensity of light reflected by the optical connector.
[0005]
One of the optical connector connection state determination methods of the present invention is to combine a pumping light source laser diode module and pumping light output from the module to an amplification optical fiber that forms a part of a signal light transmission line. A method for determining a connection state of an optical connector connected to an optical coupler, wherein the light intensity of reflected light reflected by the optical connector and returned to the laser diode module for an excitation light source is detected, and the detected light intensity is equal to or higher than a threshold value. If it is, it is determined that the connection of the optical connector is inappropriate, and if it is less than the threshold value, it is determined that it is appropriate.
[0006]
Another method of determining the connection state of an optical connector according to the present invention is to couple a pumping light source laser diode module and a pumping light output from the module to an amplifying optical fiber constituting a part of a signal light transmission line. A method for determining the connection state of an optical connector that connects an optical coupler to be waved, wherein the reflected light reflected by the optical connector and returned to the laser diode module for the excitation light source is branched before the laser diode of the module, The light intensity of the branched reflected light is detected, and if the detected light intensity is equal to or more than the threshold value, it is determined that the connection of the optical connector is inappropriate, and if the detected light intensity is less than the threshold value, it is determined that the connection is appropriate.
[0007]
Another method of determining the connection state of an optical connector according to the present invention is to couple a pumping light source laser diode module and a pumping light output from the module to an amplifying optical fiber constituting a part of a signal light transmission line. In a method for determining a connection state of an optical connector for connecting an optical coupler to be waved, an OTDR method is used to detect the light intensity of reflected light at an arbitrary position between the laser diode module for the excitation light source and the optical connector, and detect the intensity. If the detected light intensity is equal to or higher than the threshold value, it is determined that the connection of the optical connector is inappropriate, and if it is less than the threshold value, it is determined that the connection is appropriate.
[0008]
Another method for determining the connection state of the optical connector according to the present invention is to detect the light intensity of the reflected light while driving the laser diode in a pulsed manner at almost the maximum output.
[0009]
One of the pumping light sources of the present invention is a laser diode module that generates pumping light, and an optical coupler that multiplexes the pumping light output from the module to an amplification optical fiber that forms a part of a signal light transmission path. Is an excitation light source connected via an optical connector, a back facet monitor capable of generating a current corresponding to the intensity of reflected light reflected by the optical connector and returning to the laser diode module side, and a back facet monitor. A current-voltage converter that can output a voltage corresponding to the generated current, and a control determiner that can determine whether the optical connector is normally connected based on the voltage output from the current-voltage converter. It is provided.
[0010]
Another one of the pumping light sources of the present invention is a laser diode module that generates pumping light, and a light that multiplexes the pumping light output from the module to an amplification optical fiber that forms part of a signal light transmission line. A coupler and an excitation light source connected via an optical connector, and a branching portion capable of branching the reflected light reflected by the optical connector and returning to the laser diode module side before the laser diode of the module; A reflected light monitor capable of generating a current corresponding to the intensity of the reflected light branched by the branching unit, a current-voltage converter capable of outputting a voltage corresponding to the current generated by the reflected light monitor, and an output from the current-voltage converter And a control determiner capable of determining whether or not the optical connector is normally connected based on the applied voltage.
[0011]
Another one of the excitation light sources of the present invention is provided with a laser current driver capable of supplying a pulsed drive current to a laser diode.
[0012]
Another one of the excitation light sources of the present invention is provided with a display for displaying a judgment result by the control judgment unit.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
(Embodiment 1)
A first embodiment of an optical connector connection state determination method and an excitation light source according to the present invention will be described with reference to FIGS. FIG. 1 is a block diagram schematically illustrating an excitation light source described below, and FIG. 2 is a flowchart illustrating a connection state determination method of an optical connector according to the present invention performed in the excitation light source illustrated in FIG. The pump light source shown in FIG. 1 has necessary equipment in a housing 3 including an input optical connector 1 for inputting signal light to be amplified and an output optical connector 2 for outputting amplified signal light. The signal light input from the input side optical connector 1 is amplified while propagating through the amplification optical fiber 4 constituting a part of the signal light transmission path, and is output from the output side optical connector 2. Is done.
[0014]
In the housing 3, a laser diode module 5a for outputting pumping light, and an optical coupler (WDM coupler) for multiplexing the pumping light output from the module 5a to the amplifying optical fiber 4 and injecting energy. The laser diode module 5a and the WDM coupler 6 are connected via optical fibers 9 and 10 connected by a pair of optical connectors 7 and 8, respectively. Specifically, the output optical fiber 9 included in the laser diode module 5a and the input optical fiber 10 included in the WDM coupler 6 are PC-connected by the optical connectors 7 and 8, and the excitation light output from the laser diode module 5a is The light propagates to the WDM coupler 6. An optical isolator 11 is inserted in the input optical fiber 10 for the purpose of preventing the pump light reflected by the WDM coupler 6 from returning to the laser diode module 5a.
[0015]
The laser diode module 5a shown in FIG. 1 includes a laser diode (LD) 12 and a back facet monitor 13. The laser diode 12 receives a laser forward current supplied from a laser current driver 14 to generate pump light. Output. That is, the laser current driver 14 is driven to supply a laser forward current to the laser diode 12, whereby STEP (1) shown in FIG. 2 is performed. Here, most of the pumping light output from the laser diode 12 is multiplexed into the amplification optical fiber 4 by the WDM coupler 6, but part of the pumping light is caused by a difference in refractive index between glass and air. Is reflected at the end face of the laser diode 12 and returns to the laser diode 12 side.
[0016]
The back facet monitor 13 shown in FIG. 1 is constituted by a photodiode, and generates a current corresponding to the intensity of a part (reflected light) of the excitation light returning to the laser diode 12 as described above. That is, in the back facet monitor 13, the intensity of the reflected light is detected as a current level (STEP {circle around (2)} in FIG. 2). It is known that when the connection of the optical connectors 7 and 8 is inappropriate, the intensity of the reflected light is increased by several% to several tens% as compared with the case where the connection is appropriate. This is the same regardless of whether the joint end faces of the optical connectors 7 and 8 are flat or oblique. The back facet monitor 13 is conventionally mounted for the purpose of detecting the light output of the laser diode 12, but can also be used for detecting the reflected light as described above.
[0017]
As shown in FIG. 1, a current-voltage converter 15 and a control determiner 16 are also housed in the housing 3, and the current generated by the back facet monitor 13 is input to the current-voltage converter 15. The current-voltage converter 15 to which the current has been input generates a voltage corresponding to the input current, and outputs this to the control determiner 16. That is, in the current-voltage converter 15, the intensity of the reflected light is detected as a voltage level (STEP (3) in FIG. 2). The control determiner 16 to which the voltage output from the current-voltage converter 15 has been input compares the voltage level with a threshold value stored in advance (STEP 4 in FIG. 2). It is determined that the connections 7 and 8 are inappropriate (STEP 5 in FIG. 2), and if it is less than the threshold, it is determined to be appropriate (STEP 6 in FIG. 2). The determination result of the control determiner 16 is displayed on the display 17 (STEP {circle around (7)} in FIG. 2), and the operator can check the connection state of the optical connectors 7 and 8 based on the determination result displayed on the display 17. The determination result of the control determiner 16 can also be confirmed by the external centralized controller 18. The control determiner 16 also has a function of controlling the laser current driver 14, and the laser current driver 14 supplies a predetermined laser forward current to the laser diode 12 according to an instruction from the control determiner 16.
[0018]
As shown in FIG. 1, the housing 3 also houses laser diode modules 5b and 5c different from the laser diode module 5a. The pump lights output from the laser diode modules 5b and 5c are multiplexed by the optical coupler 19, and then multiplexed by the optical coupler 20 to the input optical fiber 10. That is, three pumping lights output from the laser diode modules 5a, 5b, and 5c are injected into the amplification optical fiber 4.
[0019]
(Embodiment 2)
Hereinafter, a second embodiment of the optical connector connection state determination method and the excitation light source according to the present invention will be described with reference to FIGS. FIG. 3 is a block diagram schematically illustrating an excitation light source described below, and FIG. 4 is a flowchart illustrating a method for determining a connection state of an optical connector of the present invention performed by the excitation light source illustrated in FIG.
[0020]
The basic configuration of the excitation light source shown in FIG. 3 is the same as that of the excitation light source shown in FIG. Therefore, the same reference numerals are given to those having the same names, and duplicate description will be omitted. The difference between the pumping light source shown in FIG. 1 and the pumping light source shown in FIG. 3 is that an optical coupler 19 is provided between the laser diode module 5a and the optical connector 7 (middle of the output optical fiber 9), and the reflected light is The point is that the light is branched before 5a and input to the reflected light monitor 22. Thus, even when the laser diode module 5a includes the optical isolator 21 for preventing the reflected light from entering the laser diode 12, the reflected light is detected, and the connection state of the optical connectors 7 and 8 is determined. Becomes possible. The reflected light monitor 22 functions similarly to the back facet monitor 13 shown in FIG.
[0021]
In addition, similarly to the one shown in FIG. 1, the housing 3 also houses laser diode modules 5b and 5c different from the laser diode module 5a. The pump lights output from the laser diode modules 5b and 5c are multiplexed by the optical coupler 6 and multiplexed to the input optical fiber 10. That is, the three pumping lights output from the laser diode modules 5a, 5b, and 5c are also injected into the amplification optical fiber 4 shown in FIG.
[0022]
Since the excitation light source shown in FIG. 3 has the above configuration, in the method for determining the connection state of the optical connector implemented in the light source, the reflected light is branched next to STEP (1) shown in FIG. A step (STEP-2-1 in FIG. 4) and a step of inputting the branched reflected light to the reflected light monitor 22 and detecting the intensity as a current level (STEP-2-2 in FIG. 4) are included. Join. Note that the connection state of the optical connector after STEP 2-2 is determined by the same process as that after STEP 3 shown in FIG.
[0023]
(Other embodiments)
The intensity of light reflected on the end face of the optical connector 7 shown in FIG. 1 or FIG. 3 increases as the output of the laser diode 12 shown in FIG. Further, as the intensity of the reflected light increases, the difference between the intensity of the reflected light when the connection of the optical connectors 7 and 8 is appropriate and the intensity of the reflected light when the connection is inappropriate is increased. Therefore, if the output of the laser diode 12 is increased, the determination accuracy of the connection state of the optical connectors 7 and 8 is improved. However, if the laser diode 12 is driven in a state where the connection of the optical connectors 7 and 8 is incomplete, there is a possibility that the leaked excitation light (laser light) is irradiated to the eyes of the worker, and before the connection state is confirmed. Driving the laser diode 12 with a large output is dangerous. Here, considering that the irradiation time and light intensity (generally referred to as “eye safe”) of the laser light, which is considered to be unlikely to have a significant effect on the human eye, are 1 mW for 8 hours of irradiation, If the light intensity is about 300 mW and the irradiation time is several hundred μs or less, there is no effect even if the light is irradiated to the eyes of all persons, and it is considered that the influence is further reduced if the irradiation time is shorter.
[0024]
Therefore, the laser current driver 14 shown in FIG. 1 or FIG. 3 is provided with a function of supplying a pulsed laser forward current of several tens of ns to the laser diode 12 so that the excitation light is pulsed for a short time of several hundred μs or less. Output at maximum intensity. As a result, it is possible to improve the determination accuracy while avoiding the danger. Furthermore, if the laser diode 12 is driven many times in a pulsed manner and the voltage level input to the control determiner 16 is subjected to averaging processing each time, the noise component is removed and the determination accuracy is further improved.
[0025]
The intensity of light reflected on the end face of the optical connector 7 shown in FIG. 1 can also be detected by using an OTDR (Optical Time Domain Reflection) method. FIG. 5 is a graph showing the result of measuring the intensity of the reflected light by the OTDR method. The vertical axis of the graph is a logarithmic representation of the intensity of the light pulse (reflected light) received by the back facet monitor 13 when the laser diode 12 shown in FIG. 1 is pulse-driven, and the horizontal axis represents the distance. . From the measurement results shown in this graph, the excitation light is output in a pulse form for several tens of ns from the laser diode 12 shown in FIG. 1, and the light pulse reflected by the optical connector 7 and returned is received by the back facet monitor 13. If the strength of the reception level at the time when the round-trip propagation time of the optical pulse corresponds to the position of z2 in the graph (the installation position of the optical connector 7 shown in FIG. 1) is determined, the connection state of the optical connectors 7 and 8 is determined. Can be determined.
[0026]
Here, the distance (total length of the optical fiber 9) from the laser diode module 5a to the optical connector 7 shown in FIG. 1 is z, the time for the optical pulse to reciprocate in the fiber 9 is T, the speed of light in vacuum is C, Assuming that the refractive index of the core of the optical fiber 9 is n, the relationship z = TC / 2n holds. Therefore, when the OTDR method is used for detecting the reflected light, a round-trip propagation time T of the optical pulse is provided between the laser diode module 5a and the optical connector 7 in addition to a fiber grating and a depolarizer having a length of several tens of meters. The total length of the optical fiber 9 is set to about 100 m by inserting a delace pool so that the optical fiber 9 can be identified. As a result, the time difference between the output of the excitation light from the laser diode 12 and the reception of the light pulse (reflected light) by the back facet monitor 13 is on the order of several hundred ns, and the reception level at the position z2 in the graph is shown. It is possible to determine the connection state of the optical connectors 7 and 8 shown in FIG. Specifically, a current having a level corresponding to the reception level is generated in the back facet monitor 13 and is converted into a voltage level by the current / voltage converter 15, and the control determiner 16 is connected to the optical connector 7 according to the voltage level. , 8 are determined.
[0027]
【The invention's effect】
According to the connection state determination method or the excitation light source of the optical connector of the present invention, an optical connector that connects a laser diode module for an excitation light source and an optical coupler that multiplexes signal light output from the module to an amplification optical fiber. Can be easily and reliably determined. In particular, when only a certain module is replaced or added among a plurality of modules, the connection state of the optical connector inserted / removed in the excitation light source can be easily and reliably determined.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an example of an embodiment of an excitation light source according to the present invention.
FIG. 2 is a flowchart illustrating an example of an embodiment of a method for determining a connection state of an optical connector according to the present invention.
FIG. 3 is a block diagram showing another example of the embodiment of the excitation light source of the present invention.
FIG. 4 is a flowchart showing another example of the embodiment of the optical connector connection state determination method of the present invention.
FIG. 5 is a diagram showing the result of measuring the intensity of reflected light by OTDR.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Input side optical connector 2 Output side optical connector 3 Case 4 Amplifying optical fiber 5a Laser diode module 5b Laser diode module 5c Laser diode module 6 Optical coupler 7 Optical connector 8 Optical connector 9 Output optical fiber 10 Input optical fiber 11 Optical isolator 12 Laser diode 13 Back facet monitor 14 Laser current driver 15 Current-voltage converter 16 Control determiner 17 Display 18 Centralized controller 19 Optical coupler 20 Optical coupler 21 Optical isolator 22 Reflected light monitor

Claims (8)

A method for determining a connection state of an optical connector for connecting a laser diode module for an excitation light source and an optical coupler for coupling the excitation light output from the module to an amplification optical fiber constituting a part of a signal light transmission path. Detecting the light intensity of the reflected light reflected by the optical connector and returning to the laser diode module for the excitation light source. If the detected light intensity is equal to or greater than the threshold value, it is determined that the connection of the optical connector is inappropriate, A method for determining a connection state of an optical connector, wherein the method is determined to be appropriate if the value is less than the predetermined value. A method for determining a connection state of an optical connector for connecting a laser diode module for an excitation light source and an optical coupler for coupling the excitation light output from the module to an amplification optical fiber constituting a part of a signal light transmission path. Then, the reflected light reflected by the optical connector and returned to the laser diode module for the excitation light source is branched before the laser diode of the module, and the light intensity of the branched reflected light is detected. A connection state of the optical connector is determined to be inappropriate if the value is equal to or larger than a threshold value, and is determined to be appropriate if the value is smaller than the threshold value. A laser diode module for an excitation light source and a connection state determination method of an optical connector that connects an optical coupler that couples the excitation light output from the module to an amplification optical fiber that forms a part of a signal light transmission line, Using the OTDR method, the light intensity of the reflected light at an arbitrary position between the laser diode module for the excitation light source and the optical connector is detected, and if the detected light intensity is equal to or higher than the threshold value, the connection of the optical connector is inappropriate. A connection state determination method for an optical connector, wherein the connection state is determined to be appropriate if the value is less than a threshold value. 4. The optical connector connection state determination method according to claim 1, wherein the light intensity of the reflected light is detected while driving the laser diode in a pulsed manner at substantially the maximum output. A laser diode module that generates pumping light, and an optical coupler that couples the pumping light output from the module to an amplification optical fiber that forms a part of the signal light transmission path, via an optical connector. A light source, a back facet monitor capable of generating a current corresponding to the intensity of the reflected light reflected by the optical connector and returning to the laser diode module side, and capable of outputting a voltage corresponding to the current generated by the back facet monitor An excitation light source comprising: a current / voltage converter; and a control determiner that can determine whether or not the optical connector is normally connected based on a voltage output from the current / voltage converter. A laser diode module that generates pumping light, and an optical coupler that couples the pumping light output from the module to an amplification optical fiber that forms a part of the signal light transmission path, via an optical connector. A light source, the light reflected by the optical connector and returning to the laser diode module side in accordance with a branch portion capable of branching before the laser diode of the module, and the intensity of the reflected light branched by the branch portion; A reflected light monitor capable of generating a reflected current, a current-voltage converter capable of outputting a voltage corresponding to the current generated by the reflected light monitor, and the optical connector normally operating based on the voltage output from the current-voltage converter. An excitation light source, comprising: a control determiner capable of determining whether or not the connection is established. 7. An excitation light source according to claim 5, further comprising a laser current driver capable of supplying a pulsed drive current to the laser diode. The excitation light source according to any one of claims 5 to 7, further comprising a display for displaying a determination result by the control determiner.

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