JP2002350669A - Connecting method for optical fiber and optical fiber element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a connecting method for optical fibers which can actualize target wavelength loss characteristics without inserting any optical component other than the optical fibers to be connected. SOLUTION: The fusion-spliced optical fiber 10 is fixed to optical fiber fixation parts 3a and 3b. Then the fusion-spliced part of the optical fiber 10 is heated by microtorches 4a and 4b. The quantity of heat conducted to the fusion- spliced part of the optical fiber 10 is so adjusted as to obtain target wavelength loss characteristics of the optical fiber having been spliced by properly adjusting heating conditions. Consequently, the spliced optical fiber has prescribed wavelength loss characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for connecting optical fibers and an optical fiber device composed of the connected optical fibers.

[0002]

2. Description of the Related Art Conventionally, when an optical fiber is connected, another optical fiber or an optical attenuator is inserted between two optical fibers to be connected. By this insertion, the connected optical fiber is adjusted to have a desired wavelength loss characteristic.

[0003]

In the conventional connection method as described above, since other optical components (optical fiber or optical attenuator) are inserted in addition to the optical fiber to be connected, two optical fibers are connected. When connecting, two connections had to be made. That is, the number of connection points has increased due to insertion of other components. Therefore, there is a problem that the connection loss increases. In addition, since the number of connection points is increased, there is a problem that the operation is troublesome or the cost of other optical components is increased.

The present invention has been made to solve such a problem, and an optical fiber capable of achieving a target wavelength loss characteristic without inserting optical components other than an optical fiber to be connected. And an optical fiber element connected by the connection method.

[0005]

An optical fiber connecting method according to the present invention is a method for connecting an optical fiber by fusing first and second optical fibers together.
A fusing step of bringing the end faces of the first and second optical fibers into contact with each other and fusing, and (2) a heating step of applying heat to a fusing portion including the fusing point after the fusing step. Provided, the amount of heat applied to the fused portion in the above heating step,
It is characterized in that the optical fiber after connection has a heat amount adjusted so as to have a target wavelength loss characteristic. With this configuration, the optical fiber after connection has the target wavelength loss characteristic without adjusting the wavelength loss characteristic by inserting an optical attenuator or another optical fiber between the optical fibers to be connected. I can do it. Further, since the number of connection points does not increase unnecessarily, an increase in loss due to the increase in connection points is also suppressed.

Further, the heating step comprises a first sub-heating step of applying a smaller amount of heat to the fused portion than the adjusted amount of heat, and the total amount of heat applied to the fused portion is adjusted. The method may be characterized in that the first sub-heating step is repeatedly performed until the heat amount becomes equal to the heat amount. With this configuration, the amount of heat applied to the fused portion can be finely adjusted, so that the predetermined amount of heat can be reliably applied. Therefore, it is possible to ensure that the optical fiber after connection has the target wavelength loss characteristic.

Further, the heating step includes a first step of performing the first sub-heating step once or a predetermined number of times, and a second step of measuring a wavelength loss characteristic after the first step. The method may be characterized in that the first step and the second step are alternately repeated until the measured value obtained in the second step becomes equal to or less than a target value. Thereby, the connected optical fiber can more reliably have the target loss characteristic.

Furthermore, the above-mentioned heating step comprises a second sub-heating step of applying heat to a heating range including a fusion zone and having a predetermined heating length, and the distribution of the amount of heat applied to the heating range after connection is determined. The optical fiber may be characterized by having a calorific value distribution adjusted to have a target wavelength loss characteristic. Thereby, the connected optical fiber can more reliably have the target loss characteristic.

An optical fiber element according to the present invention is characterized in that a plurality of optical fibers are connected by an optical fiber connecting method. The optical fiber element referred to here is one in which two or more optical fibers are fused and sequentially connected. For example, the optical fiber element includes a form such as an optical fiber transmission line constructed by laying two or more single mode fibers (SMFs). In addition, SMF and dispersion compensation fiber (Dispersion Co.
A dispersion compensator configured by connecting a mpensation fiber (DCF), an SMF and an erbium-doped fiber (Erbium-doped fiber).
Optical fiber amplifiers and the like configured by connecting with Doped Fiber (EDF) are also included in the optical fiber element.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for connecting optical fibers according to the present invention will be described below. The method for connecting optical fibers according to the present embodiment mainly includes a fusion operation for fusing two optical fibers and a heating operation for heating the fusion portion. First, an optical fiber heating device suitably used for this heating operation will be described with reference to the drawings.

FIG. 1A is a front view schematically showing an optical fiber heating apparatus suitable for performing the heating operation of the optical fiber connecting method according to the present embodiment. FIG. 1B is a plan view schematically showing the optical fiber heating device.

1 (a) and 1 (b), an optical fiber heating device 1 includes a base 2 and an optical fiber fixing device provided on the base 2 for fixing an optical fiber 10 fused in a fusion operation. It has parts 3a and 3b, micro torches 4a and 4b for heating the fused part of the optical fiber 10, and micro torch fixing parts 5a and 5b provided on the base 2 for fixing the micro torches 4a and 4b. Optical fiber fixing parts 3a, 3b
Are provided so that they can move in a direction approaching and moving away from each other. If the optical fiber fixing portions 3a and 3b are moved in a direction away from each other, a predetermined tension can be applied to the optical fiber 10 fixed to the optical fiber fixing portions 3a and 3b.

The micro torches 4a and 4b are
Are fixed to the anchor portions 5a and 5b. Micro torch 4
In a and 4b, propane (C not shown)_ThreeH₈) Gas container
Our C_ThreeH₈C that guides gas to micro torches 4a, 4b_Three
H₈The gas pipes 6a and 6b are connected to oxygen (O_Two) Gas volume
O from the container_TwoO to guide gas to micro torches 4a, 4b _Two
The gas pipes 7a and 7b are connected. Also a microphone
The torches 4a and 4b are optical fibers as shown in FIG.
It is arranged symmetrically with respect to the bar 10. This allows
The pressure of the flame radiated from the micro torches 4a and 4b is
The fiber 10 is symmetrically added to the fused portion.
Therefore, the optical fiber 10 is bent by the pressure of the flame.
And can be connected without.

[0014] C ₃ H ₈ gas pipe 6a, in a predetermined position of 6b, and C ₃ H ₈ gas regulators 8a, 8b are provided for adjusting the flow rate of the C ₃ H ₈ gas. O ₂ gas pipe 7
a, the predetermined position of 7b, O ₂ gas flow controller 9a for adjusting the flow rate of O ₂ gas, 9b is provided. As a result, C ₃ H ₈ gas and O ₂ gas at predetermined flow rates are supplied to the micro torches 4a and 4b.

The micro torch fixing parts 5a and 5b are provided so as to be movable in a direction approaching or moving away from each other. Therefore, the micro torches 4a, 4b fixed to the micro torch fixing parts 5a, 5b are also movable, whereby the distance between the micro torches 4a, 4b and the fusion part of the optical fiber 10 is appropriately adjusted. You. Also,
The micro torch fixing portions 5a and 5b are provided so that they can be moved in a direction along the longitudinal direction of the optical fiber 10. Thus, the amount of heat applied to the fused portion of the optical fiber can be adjusted along the longitudinal direction of the optical fiber 10.

Next, an embodiment of a method for connecting optical fibers will be described with reference to the drawings. FIG. 2 is a flowchart showing steps of an optical fiber connection method according to the present embodiment.

First, a fusion operation is performed using a predetermined arc discharge fusion device. First, two optical fibers to be connected were prepared (step 1). These two optical fibers are optical fibers in which the periphery of a glass fiber made of quartz glass is covered with a coating film. The coating film is removed a predetermined distance from the end of each of these optical fibers (step 2). Then, one of the two optical fibers is fixed to one of the optical fiber fixing portions of the fusion device, and the other optical fiber is fixed to the other of the optical fiber fixing portions (step 3). At this time, the optical fibers are fixed so that the end faces of these optical fibers face each other. Subsequently, the end faces of the two optical fibers are brought sufficiently close by moving the optical fiber fixing portion, and then the optical fibers are adjusted so that their respective central axes coincide with each other. After this adjustment, the optical fiber fixing portion is moved to bring the end faces of the two optical fibers into contact with each other. As a result, the two optical fibers are held in a state where the center axes thereof coincide with each other and the end faces are in contact with each other (step 4).

Thereafter, the contact portions of the optical fibers are fused by heating by arc discharge. After it is confirmed that the contact portion of the optical fiber has been fused, the arc discharge is stopped to end the fusion work (step 5). This allows
The fusion spliced optical fiber 10 is obtained.

Subsequently, using the optical fiber heating device 1,
The fused portion of the optical fiber 10 is heated (Step 6). The amount of heat applied to the fused portion of the optical fiber 10 can be adjusted by heating conditions. The heating conditions include the supply amounts of the C ₃ H ₈ gas and the O ₂ gas supplied to the micro torches 4a and 4b, the distance between the connection part and the micro torches 4a and 4b,
And heating time. By appropriately determining these heating conditions, the amount of heat is adjusted so that the loss characteristic of the optical fiber after connection becomes a target value. This amount of heat is
It can be determined by preliminary experiments and the like.

Further, the predetermined time is set to once or one unit,
It is more preferable to repeat the heating operation for a predetermined time a plurality of times. By doing so, the optical fiber 10
Can be adjusted in more detail. Further, it is more preferable to measure the loss characteristics of the connected optical fiber for each heating operation for a predetermined time. This ensures that the connected optical fiber has the target loss characteristics.

Further, when heating the fused portion, the micro torch fixing portions 5a and 5b are moved along the longitudinal direction of the optical fiber 10 so that a predetermined heating range including the fused portion of the optical fiber 10 is achieved. May be heated.
The heating length of this heating range can be, for example, in a range of 5 mm or more and 20 mm or less. When heating such a heating range, it is more preferable that the amount of heat to be applied has a predetermined distribution and is adjusted so that the connected optical fiber has a target loss characteristic. As described above, after a predetermined amount of heat is applied to the fusion splice, the connection operation of the optical fiber 10 ends.

Next, an experiment 1 performed to confirm the effect of the optical fiber connection method according to the present embodiment will be described. As the optical fiber to be connected, length, outer diameter,
And four sets of optical fibers with almost the same light propagation characteristics (one set of two)
Prepared.

First, the coating film at the end of each set of optical fibers was removed over a predetermined length. Next, one of these optical fibers was fixed to one of the optical fiber fixing portions of the arc discharge fusion device, and the other optical fiber was fixed to the other of the optical fiber fixing portions. Thereafter, the positions of the two optical fibers fixed to the optical fiber fixing portion were adjusted. As a result, the central axes of the two optical fibers were matched with each other. After the position adjustment was completed, the end faces of the two optical fibers were brought into contact with each other by bringing the optical fiber fixing portions closer to each other. Subsequently, the contact portion of the optical fiber was heated and fused by arc discharge. When fusion was confirmed, the arc discharge was stopped, and the fusion operation was terminated.

Next, the fused optical fiber 10 was removed from the arc discharge fusion device and attached to the optical fiber fixing portions 3a and 3b of the heating device 1. Then, the heating operation was performed eight times. Here, one heating operation means that the supply amount of the C ₃ H ₈ gas is 18 cm ³ / min and the supply amount of the O ₂ gas is 3
In the state of 0 cm ³ / min, the micro torch 4a,
It was defined that the distance between 4b and the fused portion of the optical fiber 10 was maintained at 0.5 cm, and the fused portion was heated for 20 seconds. The end of one heating operation is determined by the micro torches 4a, 4
b was kept sufficiently away from the optical fiber 10. When the heating operation was repeatedly performed, an interval time of about 10 seconds was provided between each heating operation. Thereafter, the heating operation was performed eight times according to such a procedure. Thus, the connection of the two optical fibers has been completed. Here, the connected optical fiber is referred to as an optical fiber A for convenience of description.

Next, another set of the prepared optical fibers was connected. The connection method was substantially the same as that of the optical fiber A, except that the number of heating operations was eleven.
The optical fiber thus connected is referred to as an optical fiber B. Further, another set of optical fibers was connected. The connection method is almost the same as that of the optical fiber A, except that the number of heating operations is fourteen. The optical fiber thus connected is referred to as an optical fiber C. Further, the other set of optical fibers was connected. At the time of connection, the connection method of the optical fiber A was followed except that the heating operation was not performed. The optical fiber thus connected is connected to an optical fiber D
And

Hereinafter, comparison will be made regarding the wavelength loss characteristics of the optical fibers A to D. FIG. 3 is a graph showing the wavelength loss characteristics of the optical fibers A to D. In FIG. 3, reference numerals A to D show the results of the optical fibers A to D. As can be seen from the figure, the value of the wavelength loss and the wavelength dependence are shown in the optical fibers A to
D varies greatly. The wavelength loss of the optical fiber D not subjected to the heating operation has a larger value in the measured wavelength range than the optical fibers A to C subjected to the heating operation. This confirms the effect of the heating operation performed after the fusion.

As compared with the optical fibers A to C that have been subjected to the heating operation, the loss at the wavelength of 1550 nm decreases as the number of heating operations increases from 8 (optical fiber A) to 11 (optical fiber B), It can be seen that the number increases when the number of heating operations is further increased to 14 (optical fiber C). The loss at a wavelength of 1550 nm at the time of 11 heating operations is about 0.12 dB. From this, the wavelength 1550
In order to obtain an optical fiber having a loss in nm of about 0.12 dB, it can be seen that the heating operation may be performed 11 times under the above heating conditions. Further, when actually connecting the optical fibers, heat having substantially the same amount of heat as the total amount of heat for 11 heating operations may be applied at a time.

As can be seen from FIG. 3, in the optical fiber C, the wavelength loss at a wavelength of about 1559 nm is minimized. That is, it is possible to change the wavelength at which the wavelength loss is minimized depending on the number of times of the heating operation. The optical fiber connection method of the present embodiment also has such an advantage.

Next, Experiment 2 in which the loss at a wavelength of 1550 nm is dependent on the number of heating operations will be described. In this experiment, first, after the fusion of the connection end faces was completed, the loss was measured without performing a heating operation. After that, the heating operation was performed for one heating operation under substantially the same heating conditions as described above.
Loss was measured after each run. The loss value after heating work loss value L ₀ and n-th after fusing (n is a positive integer) L _n
L ₀ / L _n was determined. The value of this ratio expressed in decibels was defined as the loss improvement. The two optical fibers to be connected are substantially the same as those in Experiment 1. The loss was measured with the two optical fibers to be connected fixed to the optical fiber fixing portions 3a and 3b.

FIG. 4 is a graph showing the dependence of the loss at a wavelength of 1550 nm on the number of heating operations. The vertical axis in the figure shows the loss improvement amount, and the horizontal axis shows the number of times of heating. From the figure,
It can be seen that the loss improvement amount decreases up to three heating times, but increases after the fourth heating time. Then, the loss improvement amount becomes maximum when the heating number is eleventh, and the loss improvement amount decreases as the heating number is further increased. From this result, if the number of times of heating is set to 11, the loss improvement amount can be maximized, that is, the wavelength loss can be minimized.

Since the heating operation and the measurement of the loss are alternately repeated, the number of heating operations can be adjusted according to the wavelength loss required for the optical fiber after connection. That is, when an optical fiber is actually connected, the heating operation may be terminated when the wavelength loss at a predetermined wavelength becomes equal to or less than a desired value as a result of the loss measurement for each heating operation.

From the results of the experiment described above, the effect of the optical fiber connection method of the present embodiment is understood. Further, if an optical fiber element is manufactured by sequentially connecting a plurality of optical fibers according to the optical fiber connecting method of the present embodiment, an optical fiber element with reduced loss due to connection can be obtained. If an optical fiber transmission line as such an optical fiber element can be prepared, when laying the optical fiber communication line over a long distance, it is not necessary to lay the connection while performing connection, so that the laying work can be simplified and shortened. There is an advantage.

A standard single-mode optical fiber having a wavelength of 1.3 μm and zero dispersion and a wavelength of 1.55 μm and a positive wavelength dispersion, and a dispersion compensating fiber having a wavelength of 1.55 μm and a negative wavelength dispersion. And wavelength 1.55μm
In some cases, an optical fiber element with dispersion compensation may be manufactured. In such a case, if the connection is made by the optical fiber connection method of the present embodiment, it is possible to manufacture an optical fiber element having a desired wavelength loss.

As described above, in the optical fiber connecting method of the present embodiment, the connecting end faces of the two optical fibers are brought into contact with each other, and the contact portion is fused by arc discharge. Subsequently, in the optical fiber heating device 1, heat whose amount of heat is adjusted so that the optical fiber after connection has a target loss characteristic is applied to the fused portion of the optical fiber. Therefore, the connected optical fiber can have the target loss characteristic without inserting another component such as an optical fiber or an optical attenuator between the optical fibers to be connected. Therefore, the number of connection points does not increase unnecessarily, and there is no possibility that the connection loss accompanying the increase in the number of connection points increases. In addition, since the number of connection locations does not increase unnecessarily, there is no need to perform extra connection work. Therefore, the number of working steps or the working time can be reduced. Further, since there is no need to use other components, an increase in connection cost can be suppressed.

Further, when applying heat to the fused portion, the operation of heating for a predetermined time is repeated a plurality of times.
The amount of heat applied to the fused portion can be adjusted in more detail. Therefore, it is effective to set the loss characteristic of the optical fiber after connection to the target characteristic. Further, if the loss characteristic of the connected optical fiber is measured every time the heating is performed for a predetermined time, it is possible to ensure that the connected optical fiber has the target loss characteristic.

Although the optical fiber connection method of the present invention has been described with reference to the embodiment, the present invention is not limited to this, and various modifications can be made. For example, the heating conditions are not limited to the above conditions, and may be appropriately determined depending on the type, outer diameter, melting temperature, and the like of the optical fiber to be connected. The number of micro torches used is not limited to two, and may be three or more.

Further, in the above embodiment, a micro torch is used, but another oxyhydrogen flame burner may be used. Further, for example, heat may be applied to the welded portion by another heating method such as heating by carbon dioxide laser light or heating by arc discharge.

[0038]

As described above, according to the optical fiber connecting method of the present invention, the optical fiber which can achieve the target wavelength loss characteristic without inserting optical components other than the optical fiber to be connected. A fiber connection method is provided.

[Brief description of the drawings]

FIG. 1A is a front view schematically showing an optical fiber heating apparatus suitable for performing a heating operation of an optical fiber connecting method according to the present embodiment. FIG. 1B is a plan view schematically showing the optical fiber heating device.

FIG. 2 is a flowchart showing steps of an optical fiber connection method according to the present embodiment.

FIG. 3 is a graph showing a wavelength loss characteristic of an optical fiber.

FIG. 4 is a graph showing the dependence of the wavelength loss at a wavelength of 1550 nm on the number of heating operations.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical fiber heating device, 2 ... Base, 3a, 3b ... Optical fiber fixing part, 4a, 4b ... Micro torch, 5a, 5
b: micro torch fixing part, 6a, 6b: propane gas pipe, 7a, 7b: oxygen gas pipe, 8a, 8b: propane gas flow rate regulator, 9a, 9b: oxygen gas flow rate regulator,
10 ... optical fiber.

Claims (5)

[Claims] 1. A method of connecting optical fibers, wherein the first and second optical fibers are connected by fusing, wherein the end faces of the first and second optical fibers are brought into contact with each other and fused. A fusing step, and after the fusing step, a heating step of applying heat to the fusing part including the fusing point, wherein the amount of heat applied to the fusing part in the heating step is the amount of heat after connection. A method of connecting an optical fiber, wherein the amount of heat is adjusted so that the optical fiber has a target wavelength loss characteristic. 2. The heating step comprises a first sub-heating step of applying a smaller amount of heat to the fused portion than the adjusted amount of heat, and the total amount of heat applied to the fused portion is adjusted. 2. The optical fiber connection method according to claim 1, wherein the first sub-heating step is repeatedly performed until the heat amount becomes equal to the heat amount. 3. The first heating step, wherein the first sub-heating step is performed once or a predetermined number of times.
And a second step of measuring the wavelength loss characteristic after the first step. The first step until the measured value obtained in the second step becomes equal to or less than a target value. 3. The optical fiber connection method according to claim 2, wherein the step and the second step are alternately and repeatedly performed. 4. The heating step includes a second sub-heating step of applying heat to a heating range including the fusion portion and having a predetermined heating length, and a calorific value distribution of the heat applied to the heating range after the connection is established. 2. The optical fiber connection method according to claim 1, wherein the heat distribution is adjusted so that the optical fiber has a target wavelength loss characteristic. 5. An optical fiber device comprising a plurality of optical fibers connected by the optical fiber connecting method according to claim 1.