JP5763566B2 - Optical fiber connection member - Google Patents

Description

  The present invention relates to an optical fiber connecting member.

  In optical connection parts such as mechanical splices, the end face of the optical fiber is not strictly flat. Therefore, a matching material having a refractive index equivalent to that of the core of the optical fiber is applied in advance to the V-shaped groove. The material is filled in a very small gap of 1 μm or less (FIG. 12A). In such an optical fiber connecting member, the connection loss is 1.31 μm and is usually 0.3 dB or less.

  The state as shown in FIG. 12A is obtained as follows. That is, the alignment material is previously applied to the groove V of the substrate 1A shown in FIG. 13, and the two optical fibers A and B are inserted into the groove V by the operator, and the end faces are abutted against each other. Thereby, the alignment material is filled in a very small gap between the end faces of the optical fibers A and B.

JP 2011-154294 A

  In an optical fiber connection member used in an optical access network, a large gap between the end faces of the optical fiber is one of the causes of performance deterioration.

  For example, when there is a large gap of about 100 μm between the end faces of the optical fibers, the connection loss at the optical fiber connection member is about 1.5 dB by filling the large gap with the matching material at the beginning of connecting the optical fibers. (FIG. 12B). Usually, an allowable loss (loss budget) between transmission apparatuses in an optical access network is designed with a certain margin with respect to an optical line loss between transmission apparatuses. For this reason, even if an optical fiber connection member having a large gap between the end faces of the optical fibers as described above is used, the optical line loss between the transmission devices immediately exceeds the allowable loss and the communication disconnection state is reached. In most cases, communication can be normally performed between transmission apparatuses.

  However, since the matching material used in the optical fiber connecting member is an oil-like material, it flows due to a temperature change with time. As a result, the air layer and the matching material can be mixed in a large gap between the end faces of the optical fibers (FIG. 12C). When this phenomenon occurs, the characteristics (connection loss, return loss) of the optical fiber connection member are significantly deteriorated (FIGS. 14 and 15), and the connection loss may reach 30 dB or more. When such a remarkably large connection loss occurs, the optical line loss between the transmission devices greatly exceeds the allowable loss, resulting in a communication disconnection state.

  Further, as described above, the state in which the air layer and the matching material are mixed in the large gap between the end faces of the optical fibers greatly fluctuates the connection loss as the temperature changes. For this reason, there are cases in which the state where communication is possible and the state where communication is interrupted are repeated alternately between the transmission apparatuses, and sometimes it is interrupted (FIGS. 14 and 15). Such occasional interruptions generally make it difficult to identify the failure location, resulting in a problem that the time required from failure occurrence to failure recovery becomes longer.

  As described above, when connecting optical fibers, it is important to connect so that no large gap is generated between the end faces of the optical fibers. However, at present, even if a large gap is generated between the end faces of the optical fibers, the connection characteristics are not significantly degraded by filling the large gap as described above, and the connection loss measurement is large. The occurrence of a gap cannot be determined.

  Also, if you want to check the presence of a large gap, a large measuring instrument is required, and in an outdoor environment where optical fiber connection members such as mechanical splices are normally used, this occurs between the end faces of the optical fiber at the beginning of connection. It is very difficult to confirm the presence or absence of a large gap.

  The present invention has been made in view of the above problems, and the purpose of the present invention is to make sure that the connection performance deteriorates when there is a large gap between the end faces of the optical fibers to be connected. When the gap becomes a gap, the connection performance becomes good, so that it can be determined whether a large gap has occurred between the end faces of the optical fiber at the beginning of the connection. An object of the present invention is to provide an optical fiber connecting member that can be prevented.

In order to solve the above-described problems, the present invention includes a substrate having a groove and a translucent member that encloses the tips of two optical fibers disposed in the groove, and the central axis of one of the optical fibers is provided. at the intersection between the interface of the extension line and the translucent member, the normal to the angle between the center axis of the core of the light transmitting member is of a size not optical fiber connecting member than 0 degrees, in the optical fiber connecting member The connection loss of the optical fiber increases as the optical fiber recedes, and the rate of increase when the tip is separated from the light transmissive member is greater than the rate of increase when the tip is contained in the light transmissive member. It is large .

  For example, the translucent member is a solid having elasticity.

  For example, the substrate has a groove in which the translucent member is disposed.

  For example, the translucent member is configured integrally with a grip portion that is gripped when the translucent member is disposed in a groove in which the translucent member is disposed.

  For example, the translucent member is obtained by applying the raw material of the translucent member to a groove in which the translucent member is disposed and curing the raw material.

  For example, the translucent member is a translucent member having a central axis of two optical fibers facing each other and two interfaces intersecting the central axes, and the central axis of one of the optical fibers and the translucent light The angle formed by the normal to the interface of the member is different from the angle formed by the central axis of the other optical fiber and the normal to the interface of the translucent member.

  For example, the optical fiber is a hole fiber.

  According to the optical fiber connecting member of the present invention, at the intersection of the extension line of the central axis (optical axis) of the opposing optical fiber and the interface (boundary surface) of the light transmitting member disposed in the middle of the optical fiber, Since the angle formed between the normal of the optical member and the central axis of the core is greater than 0 degrees, if there is a large gap between the end faces of the optical fiber, the connection characteristics are always deteriorated. As a result, it is possible to prevent the occurrence of a large gap at the beginning of the connection by reconnecting. In addition, since a light-transmitting member that has elasticity and keeps its shape is used, the state can be maintained when the optical fiber connection is good.

It is a perspective view which shows schematic structure of the optical fiber connection member which concerns on this Embodiment. It is a figure which shows the 1st step of the optical fiber connection by an optical fiber connection member. It is a figure which shows the 2nd step of the optical fiber connection by an optical fiber connection member. It is a figure which shows the 3rd step of the optical fiber connection by an optical fiber connection member. It is a perspective view which shows the optical fiber connection member of the state to which the optical fiber was connected. FIG. 6A is a plan view showing the optical fibers A and B and the translucent member 4 in the state shown in FIG. FIG. 6B is a plan view showing the optical fibers A and B and the translucent member 4 in an unfavorable state. It is a figure which shows the relationship between angle (theta) and a connection loss in the state shown in FIG.6 (b). It is a figure which shows the relationship between the distance l between the end surfaces of the optical fibers A and B, and a connection loss. It is a figure which shows the shape of the translucent member 4 which concerns on the modification 1. FIG. FIG. 10A is a plan view showing the optical fibers A and B and the translucent member 4 according to the first modification. FIG. 10B is a plan view showing a state in which the tip of the optical fiber B is included in the light transmitting member 4 shown in FIG. 10A and there is a gap S between the optical fiber A and the light transmitting member 4. FIG. FIG. 10C is a plan view showing a state in which the tip of the optical fiber A is included in the light transmissive member 4 shown in FIG. 10A and there is a gap S between the optical fiber B and the light transmissive member 4. FIG. It is a perspective view which shows the form of the optical fiber connection which concerns on the modification 3. It is a figure which shows between the end surfaces of the optical fiber connected by the conventional optical fiber connection member. It is a fragmentary perspective view which shows a mode that an optical fiber is connected by the conventional optical fiber connection member. It is a figure which shows the relationship between the temperature change with a space | gap between the end surfaces of the optical fiber at the time of a temperature cycle test, and a connection loss. It is a figure which shows the relationship between the temperature change with a space | gap between the end surfaces of the optical fiber at the time of a temperature cycle test, and a return loss.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view showing a schematic configuration of an optical fiber connecting member according to the present embodiment.

  The optical fiber connection member according to the present embodiment (hereinafter simply referred to as an optical fiber connection member) optically connects two optical fibers (here, referred to as optical fibers A and B) like a mechanical splice, for example. 1, the substrates 1 and 2, the fixing member 3 that fixes the substrates 1 and 2 in a combined state, and the light-transmitting member 4 though omitted in FIG. 1.

  The length L in the longitudinal direction of the optical fiber in the substrates 1 and 2 is, for example, about 4 cm. The width W perpendicular to the longitudinal direction of the optical fiber in the substrates 1 and 2 is, for example, about 4 mm. The heights H1 and H2 perpendicular to the longitudinal direction of the optical fibers in the substrates 1 and 2 are, for example, about 2 mm.

  FIG. 2 is a diagram showing a first stage of optical fiber connection by the optical fiber connection member, and is an exploded perspective view showing the optical fiber connection portion C of FIG.

  The substrate 1 has a groove V having a V-shaped cross section and a groove G intersecting the groove V.

  The groove G is not perpendicular to the groove V, but intersects with an inclination.

  The groove G has a shape that matches the translucent member 4, and the translucent member 4 is disposed in the groove G. Therefore, the translucent member 4 can be easily disposed at a predetermined position. Moreover, the dimension of the groove | channel G is a little larger than the translucent member 4, and is substantially the same. Therefore, the movement of the translucent member 4 can be prevented in the optical fiber connecting member.

  The translucent member 4 has a property of transmitting light with a refractive index equivalent to that of an optical fiber, but does not have fluidity like a conventional matching material, and normally maintains the same shape. .

  More specifically, the translucent member 4 is made of an acrylic or silicon resin and has elasticity. The translucent member 4 made of an acrylic or silicon resin can generally be made so as not to change its shape even after a long period of time and does not contain bubbles.

  The width 4W of the portion intersecting the groove V of the translucent member 4 is, for example, about 115 μm, and the height 4H in the depth direction of the groove G in the translucent member 4 is, for example, about 500 μm. The depth of the groove G is slightly shallower than the height 4H of the translucent member 4, for example.

  The translucent member 4 is configured integrally with a grip portion 41 that is gripped when the translucent member 4 is disposed in the groove G. The grip 41 is, for example, circular, and the diameter 41D is, for example, about 1.44 mm. Since the translucent member 4 includes the grip portion 41, a part of the groove G has a shape that matches the grip portion 41.

  Since the translucent member 4 includes the grip portion 41, the translucent member 4 can be easily disposed in the groove G by gripping the grip portion 41 with tweezers or the like.

  For example, the worker arranges the translucent member 4 in the groove G and abuts the substrates 1 and 2 in such a manner.

  FIG. 3 is a view showing a second stage of optical fiber connection by the optical fiber connection member, and is a perspective view showing an optical fiber connection portion C in FIG.

  Since the depth of the groove G is slightly shallower than the height of the translucent member 4, the upper portion of the translucent member 4 protrudes from the groove G.

  The optical fiber A is inserted into the groove V by the operator and proceeds to the light transmitting member 4 from one side. On the other hand, the optical fiber B is also inserted into the groove V by the operator, and proceeds to the translucent member 4 from the other side. The central axes (optical axes) of the cores of the optical fibers A and B coincide with each other.

  4 is a diagram showing a third stage of optical fiber connection by the optical fiber connection member, and is a perspective view showing an optical fiber connection portion C in FIG.

  The tips of the optical fibers A and B that have traveled through the groove V to the light transmissive member 4 enter the light transmissive member 4, and thereby the light transmissive member 4 includes the tips (end surfaces) of the optical fibers A and B. It will be.

  The connection of the optical fibers A and B can be confirmed, for example, by bending the optical fibers A and B as shown in FIG.

  Thereafter, as shown in FIG. 1, the operator sandwiches the substrates 1 and 2 with the fixing member 3, and the positions of the substrates 1 and 2 are fixed. Further, the positions of the optical fibers A and B are fixed by the substrates 1 and 2 so as not to move.

  FIG. 6A is a plan view showing the optical fibers A and B and the translucent member 4 in the state of FIG.

  The translucent member 4 has an angle θ between the normal 4H of the translucent member 4 and the central axis of the core AC at an intersection AI between the extension line of the central axis of the core AC and the interface 4S of the translucent member 4. It is arranged to be larger than the degree. That is, the translucent member 4 is disposed obliquely with respect to the core AC. The same applies to the optical fiber B.

  Such an arrangement can be stably maintained by arranging the translucent member 4 in the groove G.

  The tips of the optical fibers A and B enter the translucent member 4 and are contained in the translucent member 4.

  Therefore, since the contact surface A1 between the optical fiber A and the translucent member 4 is the end surface of the optical fiber A, it is substantially perpendicular to the core AC of the optical fiber A. The same applies to the optical fiber B.

  The light K traveling through the core AC is sufficiently incident on the core of the optical fiber B without changing the traveling direction at the contact surface A1. That is, this figure is a figure in a good state. In this good connection state, the connection loss when the gap between the end faces of the optical fiber becomes a very small gap of 1 μm or less is 1.31 μm and 0.3 dB or less.

  FIG. 6B is a plan view showing the optical fibers A and B and the translucent member 4 in an unfavorable state.

  The tip of the optical fiber A is not enclosed in the translucent member 4, and a gap S is formed between them. The same applies to the optical fiber B.

  As described above, since the angle θ is larger than 0 degree, the interface 4S (including AI) of the translucent member 4 is inclined with respect to the extending direction of the core AC, that is, the traveling direction of the light K. Thereby, when the light K enters the translucent member 4, the traveling direction is changed by AI (incident position). As a result, the light K does not sufficiently enter the core BC of the optical fiber B, for example, and the connection loss increases.

  In other words, in the present embodiment, when the gap S is formed unexpectedly, the connection loss is large, that is, it is possible to determine such a poor connection state at the time of connection.

  FIG. 7 is a diagram showing the relationship between the angle θ and the connection loss in the state shown in FIG. From this figure, it can be seen that the connection loss increases as the angle θ increases. Therefore, in order to intentionally increase the connection loss in the state shown in FIG. 6B, the angle θ should be designed to be large, and the value of the connection loss can be changed by controlling the angle θ. For example, when the thickness d of the translucent member 4 on the central axis extension line of the core AC shown in FIG. 6B is 120 μm, if the angle θ is 15.1 degrees, the connection loss is about 20 dB. Therefore, when the angle θ is set to 16.0 degrees, if a connection loss of 20 dB or more is measured, it may be determined that the state shown in FIG.

  Since the connection loss changes with the thickness d and the angle θ, the connection loss according to the thickness d and the angle θ occurs when the state shown in FIG. 6B occurs. In that case, it may be determined that the state shown in FIG.

  FIG. 8 is a diagram showing the relationship between the distance l between the end faces of the optical fibers A and B and the connection loss.

  When the distance l is short, that is, when both ends of the optical fibers A and B enter the translucent member 4 and are included, the connection loss is small. The light traveling through the core of the optical fiber A is sufficiently incident on the core of the optical fiber B without changing the traveling direction.

  For example, the tips of the optical fibers A and B are not completely inserted into the transparent member 4, and the distance d is the thickness d of the transparent member 4 on the central axis of the optical fibers A and B. If they are the same, the connection loss rapidly increases at such a distance l. The light traveling through the core of the optical fiber A begins to change its traveling direction.

  For example, when the optical fiber A has not entered the translucent member 4 at all and a large gap is formed between the end faces of the optical fibers A and B, the distance l is longer, and the translucent member 4 It becomes longer than the thickness d. At such a distance l, the connection loss is even greater. Although not shown in the drawing, the light traveling through the core of the optical fiber A changes its traveling direction, so that sufficient light does not enter the core of the optical fiber B.

  In the optical fiber connecting member, it is possible to determine whether the optical fiber connection state is good or not by setting the connection loss generated in each of the good connection state and the poor connection state as follows. In other words, the connection loss that occurs in a good connection state is set to a predetermined threshold (for example, 2 dB) or less, and the connection loss that occurs in an unsatisfactory connection state greatly exceeds the permissible loss between transmission devices. It is made more than such value (for example, 20 dB or more).

  Further, the return loss of light at the connection point of the optical fibers A and B needs to be equal to or greater than a prescribed return loss threshold. The return loss is an index indicating the amount of reflection of light at the connection point of the optical fiber. It is stipulated that the return loss of currently used mechanical splices, field assembly optical connectors, and factory-made optical connectors is 40 dB or more.

  Although not shown, when the connection between the optical fibers is good, the return loss is as large as 40 dB or more, and when the connection between the optical fibers is not good, the return loss is about 14.7 dB (air Fresnel). It is known that this is a reflection.

  Therefore, whether the optical fiber connection state is good or not can also be determined by comparing the return loss amount and the threshold value, and the determination can also be performed by setting the threshold value in the same manner as in the case of the connection loss.

(Modification 1)
As the shape of the translucent member 4, in addition to the shape of the translucent member 4 of the present embodiment, for example, as shown in FIGS. 9A to 9F, a parallelogram (a trapezoid may be used). ), A triangle (a right triangle or an isosceles triangle), a circle, a semicircle, and an ellipse.

  The angle θ in FIG. 9 corresponds to the angle θ in FIG. 6, and the same effect can be expected if the translucent member 4 is arranged so that the angle θ is greater than 0 degrees.

  Further, for example, as shown in FIG. 10A, an angle θA formed between the central axis of the core AC and the normal line 4HA of the translucent member 4, and the central axis of the core BC and the normal line 4HB of the translucent member 4 The angle θB formed by is an angle of 0 ° or more, but is not necessarily the same angle.

  As shown in FIG. 10A, when considering a shape in which the angle θA is close to 0 degrees and the angle θB is extremely large (90 degrees or less) compared to the angle θA, the optical fiber B is included in the translucent member 4 and When the gap S is generated between the optical fiber A and the translucent member 4 (FIG. 10B), the optical fiber A is included in the translucent member 4, and the optical fiber B and the translucent member 4 is different from the case where the gap S is generated between the four (FIG. 10C).

  Thereby, for example, when the connection loss is measured in the direction from the optical fiber A to the optical fiber B, the connection loss measured in the state of FIG. 10B is the connection loss measured in the state of FIG. Smaller than. Therefore, even when the connection location of the optical fiber cannot be confirmed, the connection state of the optical fiber can be predicted from the magnitude of the value by measuring the connection loss.

  In addition, what is necessary is just to make it match | combine with the shape of such a translucent member 4 about the groove | channel G in which the translucent member 4 is arrange | positioned. Moreover, although not shown in figure, if the translucent member 4 which has these shapes is also comprised integrally with the holding part 41, workability | operativity can be improved.

(Modification 2)
Further, instead of disposing the translucent member 4 having a certain shape in advance in the groove G, the raw material of the translucent member 4 (for example, an oily resin raw material) is applied to the groove G and cured by ultraviolet irradiation. The light transmissive member 4 may be formed in the groove G by performing processing such as curing due to high temperature, curing due to humidity, and curing due to chemical change. In this case, since it is not necessary to hold the translucent member 4, the holding part 41 is unnecessary, and the groove G may have such a shape.

  According to the second modification, for example, when a large number of optical fiber connection members are manufactured, it is not necessary to prepare a place where each light transmissive member 4 is placed, which is preferable.

  Further, since the raw material is, for example, oily, it is easy to make the translucent member 4 closely contact with the groove G, which is also preferable in this respect.

(Modification 3)
As a form for performing the optical fiber connection, for example, one optical fiber (for example, optical fiber A) is preliminarily shown in the mechanical splice mechanism inside the connector as a built-in fiber, such as a field assembly type connector having a mechanical splice mechanism. 11, and the tip is included in the translucent member 4. In this state, only the other optical fiber (for example, the optical fiber B) is inserted into the V-shaped groove by the operator, and as a result, it may be arranged as shown in FIG.

(Modification 4)
The target optical fiber to be connected with the optical fiber connecting member is not only a silica-based optical fiber such as a single mode fiber or a multimode fiber currently used, but also a hole fiber or a plastic such as a photonic crystal fiber or a holey fiber. It can also be used for fiber.

  In particular, in the case of a holey fiber, when a conventional oil-like matching material is used for a hole fiber connecting portion, there is a problem that the matching material penetrates into holes in the fiber and deteriorates connection and transmission performance. . If a translucent member that is a solid having elasticity is used, the above problem can be solved, which is more effective.

  As described above, according to the optical fiber connecting member of the present embodiment, as shown in FIG. 6A, the extension line of the central axis of the core (AC) and the interface (4S) of the translucent member 4 ), The angle (θ) between the normal line (4H) of the translucent member 4 and the central axis of the core (AC) is greater than 0 degrees, so that the tip of the optical fiber (A, B) Is contained in the translucent member 4, that is, when the gap between the end faces is below a certain level, good connection characteristics are obtained, and the good connection characteristics continue, whereas, as shown in FIG. Thus, when the tip of the optical fiber (A, B) is not encapsulated in the translucent member 4, that is, when there is a large gap between the end faces of the optical fiber (A, B), the connection characteristics are necessarily deteriorated. Such a connection state can be easily determined by measuring a connection loss or the like.

  Further, as illustrated, the translucent member 4 is, for example, an acrylic or silicon resin, so that it does not change its shape even after a long time has passed and can be made so as not to contain bubbles. Is preferable.

  Moreover, since the board | substrate 1 has the groove | channel where the translucent member 4 is arrange | positioned, the translucent member 4 can be easily arrange | positioned in a predetermined position, and the movement of the translucent member 4 can be prevented.

  Moreover, since the translucent member 4 is integrally formed with the grip portion 41 that is gripped when the translucent member 4 is disposed in the groove G, the translucent member 4 can be easily disposed in the groove G. it can. Of course, the gripping portion 41 is not necessary as long as the translucent member 4 can be disposed without providing the gripping portion 41.

  Further, by applying the raw material of the translucent member 4 to the groove in which the translucent member 4 is disposed and curing the raw material, for example, when manufacturing a large number of optical fiber connection members, each translucent member 4 is placed. It is not necessary to prepare a place to keep, which is preferable. In addition, since the raw material is, for example, oily, it is easy to make the translucent member 4 in close contact with the groove G, which is preferable.

DESCRIPTION OF SYMBOLS 1, 1A, 2 ... Board | substrate 3 ... Fixed member 4 ... Translucent member 41 ... Grip part 4H, 4HA, 4HB ... Normal of translucent member 4 4S ... Interface of translucent member 4 A, B ... Optical fiber A1 ... Light Contact surface of fiber A and translucent member 4 AC: core of optical fiber A AI: intersection of extension line of central axis of core AC and interface 4S of translucent member 4 BC: core of optical fiber B C: optical fiber Connection location d: thickness of translucent member 4 on the central axis extension line of core AC G, V ... groove K ... light 1 ... distance between end faces of optical fibers A, B S: optical fibers A, B and translucent member 4, the angle θ between the normal line 4H of the translucent member 4 and the central axis of the core AC at the intersection AI of the extension line of the central axis of the core AC and the interface 4S of the translucent member 4 large)
θA: Angle formed by the central axis of the core AC and the normal 4HA of the translucent member 4 (greater than 0 degrees)
θB ... Angle formed by the central axis of the core BC and the normal 4HB of the translucent member 4 (greater than 0 degrees)

Claims (7)

A substrate having a groove;
A translucent member containing the ends of two optical fibers arranged in the groove,
At the intersection between the interface of the extension line and the translucent member of the central axis of one of the optical fiber, the angle between the center axis of the normal to the core of the light transmitting member is greater than 0 degrees
An optical fiber connecting member,
When the optical fiber is retracted, the connection loss at the optical fiber connection member increases, and when the tip moves away from the light transmissive member than the rate of increase when the tip is included in the light transmissive member. The rate of increase is greater
An optical fiber connecting member .   The optical fiber connecting member according to claim 1, wherein the translucent member is a solid having elasticity. The optical fiber connection member according to claim 1, wherein the substrate has a groove in which the translucent member is disposed. The optical fiber connection according to claim 3, wherein the translucent member is configured integrally with a grip portion that is gripped when the translucent member is disposed in a groove in which the translucent member is disposed. Element. The optical fiber connecting member according to claim 3, wherein the light transmissive member is obtained by applying a raw material of the light transmissive member to a groove in which the light transmissive member is disposed and curing the raw material. The translucent member is a translucent member having a central axis of two optical fibers facing each other and two interfaces intersecting the central axes.
The angle formed between the central axis of one of the optical fibers and the normal to the interface of the light transmitting member is different from the angle formed between the central axis of the other optical fiber and the normal to the interface of the light transmitting member. The optical fiber connecting member according to any one of claims 1 to 5, wherein The optical fiber connecting member according to claim 1, wherein the optical fiber is a hole fiber.

Images