JP5491440B2 - Fan-out parts for multi-core fiber - Google Patents

Description

  The present application relates to a fan-out component for a multi-core fiber, and more specifically, is a type of optical fiber that individually inputs / outputs light to the plurality of cores of a multi-core fiber having a plurality of cores arranged in parallel. The present invention relates to a fan-out component for multi-core fiber for output.

  The demand for various services using wired networks, such as digital terrestrial broadcast distribution and on-demand distribution of high-quality content such as music and video, has increased, and IP-related networks such as the Internet and Next Generation Network (NGN) The capacity of construction and information transmission is increasing. The amount of information transmission in these networks is increasing every year, and further expansion of the transmission capacity is desired. Along with this, a large expansion of information transmission capacity is also expected in optical communication using an optical fiber as a transmission path. As a means for improving the transmission capacity per optical fiber, a wavelength division multiplexing communication system has been developed and used in the commercial network.

  One effective means for further increasing the transmission capacity per optical fiber is to use a multi-core fiber (MCF) as the optical fiber (see, for example, Non-Patent Document 1). The MCF has a plurality of cores, and these cores are arranged in parallel in the longitudinal direction. Basically, separate optical signals are transmitted along each core. It can be considered that one optical fiber has a plurality of transmission paths, and optical signals having the same wavelength can be transmitted simultaneously. In each core, transmission by the wavelength multiplexing method is also possible. In other words, it is common to lay a plurality of optical fibers and perform spatial multiplexing transmission. However, if MCF is used, spatial multiplexing transmission can be performed with one optical fiber.

  1 to 4 are diagrams showing typical configuration examples of the MCF (MCFs 120, 420, 520, and 620, respectively). Here, only the core (cores 120a, 420a, 520a, and 620a, respectively) and the clad (claddings 120b, 420b, 520b, and 620b, respectively) are shown, and the covering and the like are omitted. 1 and 2 show the configuration of an MCF having seven cores, FIG. 3 shows the configuration of an MCF having three cores, and FIG. 4 shows the configuration of an MCF having 13 cores. ing. In the MCF, generally, the cores are arranged so that the distance between adjacent cores (more specifically, the distance between the centers of adjacent cores) is equal. In order to facilitate understanding, in FIGS. 1 to 4, the diameter is equal to the interval dc between adjacent cores, and the center is a virtual circle that coincides with the center of the core (virtual circles 120c, 420c, and 520c, respectively). , And 620c) are indicated by broken lines. In the example of FIGS. 1, 3, and 4, the clad diameter D is set so that the shortest distance from the center of the core disposed on the outer side to the outer periphery of the clad is dc / 2. In other words, the cladding diameter D is 3 * dc when the number of cores in FIG. 1 is 7, and {1 + 2 / √3} * dc when the number of cores in FIG. When the number of cores is 13, {1 + 2√3)} * dc. In the example of FIG. 2, the cladding diameter D is slightly larger than 3d. The reason why the clad diameter D is slightly increased in this way is to reduce the propagation loss caused by the electric field distribution (mode field) of light propagating through each core disposed outside oozes out from the clad to the coating (not shown). It is to do. A typical value of the clad diameter D is 125 μm, which is the same as that of a normal optical fiber (only one core) in the example of FIG. The core interval dc is 41.7 μm. If the cladding diameter D is increased to, for example, 250 μm or more, the probability of breakage increases when the MCF is bent. In other words, the cladding diameter D is expected to be limited to about 200 μm or less, depending on the future development trend of MCF.

B. Zhu, TFTaunay, MFYan, JMFini, M. Fishteyn, EMMonberg, and FVDimarcello, "Seven-core multicore fiber transmissions for passive optical network", OPTICS EXPRESS, Vol.18, No.11, pp. 11117-11122, 24 May 2010

  In order to use the MCF as a transmission path for optical communication, a fan-out component is indispensable. The fan-out component is an optical component for inputting or outputting light independently from each core of the MCF. A fan-out component of the type in which light propagating through each core of the MCF is led to a plurality of ordinary optical fibers (equal to the number of cores of the MCF) (with one core per MCF) and output is particularly useful. is there. In order to be used in a commercial optical communication system, the fan-out component is required to be small, low cost, and highly reliable.

  However, as described above, the interval between the cores in the MCF is very small, and the cores are two-dimensionally arranged. Therefore, it is not easy to realize a fan-out component that can satisfy such requirements. . Even if a normal optical fiber (with a clad diameter of about 125 μm) is disposed, the core interval does not become small as described above. Therefore, for example, the position of a plurality of small diameter fibers (the same number as the number of cores of MCF) having an outer diameter (cladding diameter) smaller than the interval dc between adjacent cores in the MCF is individually controlled, and each of the MCF end faces is controlled. A method of coupling light from each core to each small-diameter fiber in accordance with the position of the core can be considered. However, this means requires as many fine movement stages as the number of the small-diameter fibers, and it becomes a large-scale and expensive system. Although it can be used in an optical transmission experiment using MCF, it should be used in a commercial optical communication system. Not suitable for.

  Accordingly, referring to FIGS. 1 to 4, a plurality of thin fibers (the same number as the number of cores of the corresponding MCF) having the clad diameter d substantially equal to the interval dc between the adjacent cores in the MCF are closest, that is, If it arrange | positions so that adjacent small diameter fibers may contact, the relative position of the core of each small diameter fiber will become equal to the relative position of each core of MCF. And it can be estimated comparatively easily that a fanout part can be constituted by positioning MCF and a small diameter fiber suitably, and abutting those end faces. However, it is unknown how to realize a fan-out component that can satisfy the above requirements, and it has not been realized yet.

  Accordingly, the present invention has been made in view of such problems, and an object thereof is to provide a fan-out component for MCF that is small in size, low in manufacturing cost, and high in reliability.

In order to achieve the above object, according to the present invention, the invention according to claim 1 inputs and outputs light individually to the three or more cores with respect to a multi-core fiber having three or more cores. Fan-out parts for multi-core fibers for
A first ferrule having a single first guide hole having a circular cross section;
A plurality of first optical fibers housed in the first guide hole, each having a single core and a small diameter less than 125 μm ;
A first fiber block made of glass containing the plurality of first optical fibers, wherein the first fiber block includes the same number of second optical fibers as the plurality of first optical fibers. The second optical fiber is bonded to the second optical fiber block, the first optical fiber is accommodated at the same pitch as the second optical fiber in the second optical fiber block, and the second optical fiber is a core. And a first fiber block having a cladding diameter of 125 μm,
The plurality of first optical fibers have a cladding diameter that is substantially equal to the interval between adjacent cores in the multi-core fiber, and are arranged closest to each other and fixed to the first ferrule.
The diameter of the first guide hole has a value approximately equal to the diameter of a circle circumscribing the plurality of first optical fibers arranged in the close proximity,
The relative position of each core of the plurality of first optical fibers is substantially equal to the relative position of each core of the multi-core fiber,
Input / output of light from the first optical fiber is performed with respect to the second optical fiber.

The invention according to claim 2 is a fan-out component for a multi-core fiber according to claim 1,
Further comprising a second ferrule having a second guide hole for accommodating the multi-core fiber,
The first ferrule and the second ferrule have a cylindrical structure in which a central axis substantially coincides with a central axis of the first guide hole and the second guide hole,
An inner wall has a cylindrical shape, and includes a split sleeve that accommodates the first ferrule and the second ferrule.

The invention described in claim 3 is the fan-out component for a multi-core fiber according to claim 2,
The end faces of the plurality of first second ferrule end face of the first ferrule, including the end face of the optical fiber and including an end face of the multicore fiber, the end face of the first optical fiber of said plurality of Having a smooth convex spherical shape so as to enable physical contact with the end face of the multi-core fiber,
Either or both of the first ferrule and the second ferrule can be inserted into and removed from the split sleeve.

The invention according to claim 4 is a fan-out component for a multi-core fiber according to claims 1 to 3,
The multi-core fiber has six or seven cores, and has seven first optical fibers in the first guide hole of the first ferrule,
The diameter of the first guide hole is approximately equal to a value that is three times the cladding diameter of the first optical fiber.

  The fan-out component for MCF of the present invention has a ferrule having a guide hole (inner diameter: D) having a circular cross-sectional shape and a predetermined number (corresponding to the number of cores of MCF) of a thin fiber (outer diameter: d) The small diameter fiber is inserted into the guide hole and fixed to the ferrule using an adhesive (resin or the like). The outer diameter d of the thin fiber is set to a value approximately equal to the interval between adjacent cores in the MCF. Further, the inner diameter D of the guide hole is equal to the diameter of a circle circumscribing a predetermined number (usually the same as the number of cores of the MCF) of fine fibers arranged closest to each core position of the MCF. It is set to be approximately equal. Specifically, the value of D is as follows. {1 + 2 / √3} * d for an MCF with 3 cores, 3 * d for 7 cores, and {1 + 2√3} * d for 13 cores. As described above, when the outer diameter d of the small-diameter fiber and the inner diameter D of the guide hole are set (actual values have some errors), the predetermined diameter of the small-diameter fiber is simply inserted into the guide hole. The fibers are arranged closest to correspond to the relative position of each core of the MCF. As described above, the relative position of each small-diameter fiber can be easily realized. As the ferrule, a commercially available ferrule for optical connectors can be used. These lead to the realization of low-cost fan-out components. In general, the outer dimension of the ferrule is several mm in the direction perpendicular to the guide hole, and the fan-out component can be made small. Furthermore, since the predetermined number of small-diameter fibers are in contact with the guide hole wall in the guide hole, or are arranged in close contact with each other, positional fluctuations with respect to the ferrule are suppressed, so that fluctuations in temperature and humidity On the other hand, or even in the long term, the relative position of the thin fiber to the ferrule is stable. This contributes to the high reliability of the fan-out component.

  In the MCF fan-out component of the present invention, as the ferrule for accommodating the above-mentioned small-diameter fiber, the outer shell is cylindrical and the center position of the cylindrical shape coincides with the center position of the guide hole. Both ferrules are inserted into the split sleeve so that the end faces of both ferrules face each other. In this configuration, the alignment of the small-diameter fiber in the guide hole and the MCF can be realized only by relatively rotating both ferrules. Positioning in the direction perpendicular to the guide hole axis is realized by inserting both ferrules into the split sleeve. Cylindrical ferrules and split sleeves as described above are used in general single-core optical connectors (SC connectors, MU connectors, etc.), and can be procured as a commercial product having a guide hole inner diameter of about 125 μm. Even if the inner diameter of the guide hole is a ferrule other than that, it can be manufactured relatively easily. This is because the diameter of the guide hole is controlled by polishing using a wire electrodeposited with diamond abrasive grains. As described above, the fact that the MCF and the small diameter fiber can be easily aligned and the ferrule can be manufactured at a low cost leads to a low-cost manufacturing of the fan-out component. Further, even in a configuration in which both ferrules are connected by a split sleeve, the outer dimension in a direction perpendicular to the longitudinal axis is several mm, and this fan-out component can be reduced in size. Furthermore, as a means for connecting ferrules with a split sleeve, a single-core optical connector has a good use record and high reliability is recognized. Therefore, high reliability can be obtained also in the present fan-out component.

  In the fan-out component for MCF of the present invention, the end face (including the end face of the small diameter fiber) of the ferrule that accommodates the predetermined number of small diameter fibers is made into a smooth convex spherical shape by using means such as polishing. The same applies to the ferrule that houses the MCF. Thereby, MCF and a thin fiber can be detachably connected. That is, the thin fiber and the MCF can be connected as a connector. In this connection, a PC (Physical Contact) connection can be realized and a good connection characteristic (low return loss) can be obtained. In this configuration, a portion for connecting the MCFs is not required (in the case of a fan-out component in which the MCF and the thin fiber are permanently connected, the MCFs need to be connected), and the longitudinal dimension of the fan-out component is reduced. Can be made at a lower cost. As means for processing the ferrule end face into a convex spherical shape, polishing means used in the manufacture of existing optical connectors can be used, so the processing cost is the same as the processing cost of the ferrule end face of the existing optical connector. Can be about. PC connection is also used in widely used optical connectors such as SC connectors and is a highly reliable connection means, and high reliability can be obtained for this component.

It is a figure which shows the structure of MCF used for Embodiment 1-3 of this invention. It is a figure which shows the structure of MCF used for Embodiment 4 of this invention. It is a figure which shows the structure of MCF used for Embodiment 5 of this invention. It is a figure which shows the structure of MCF used for Embodiment 6 of this invention. 1 is an overall configuration diagram of an MCF fan-out component according to Embodiment 1 of the present invention. FIG. It is a figure which shows the structure inside the housing | casing of the fanout part for MCF which concerns on Embodiment 1 of this invention, (a) is EE sectional drawing, (b) is AA sectional drawing, (c) is B- It is a figure which shows B sectional drawing. It is a cross-sectional enlarged view which shows the structure inside the housing | casing of the fanout part for MCF which concerns on Embodiment 1 of this invention, (a) is an enlarged view of MCF vicinity of the cross section AA, (b) is cross section BB. It is a figure which shows the enlarged view of thin fiber vicinity. It is a block diagram of the fiber block which accommodates the fiber of the fanout part for MCF based on Embodiment 1 of this invention, (a) is a structure of the fiber block which accommodates a thin fiber, (b) accommodates a normal fiber. It is a figure which shows the structure of a fiber block. It is a figure which shows the structure inside the housing | casing of the fanout part for MCF which concerns on Embodiment 2 of this invention, (a) is a cross section EE, (b) is an enlarged view of the ferrule vicinity of cross section AA, (c) ) Is an enlarged view of the vicinity of the ferrule of section BB. It is a block diagram of the whole MCF fan-out component which concerns on Embodiment 3 of this invention. It is a block diagram inside the housing | casing of the fanout part for MCF which concerns on Embodiment 3 of this invention, (a) is a plug connection state, (b) is a figure which shows a plug connection cancellation | release state. It is a cross-sectional enlarged view which shows the structure inside the ferrule of the fanout part for MCF which concerns on Embodiment 4 of this invention, (a) is a cross-sectional enlarged view near MCF, (b) shows a cross-sectional enlarged view near a thin fiber. FIG. It is a cross-sectional enlarged view which shows the structure inside the ferrule of the fanout part for MCF which concerns on Embodiment 5 of this invention, (a) is a cross-sectional enlarged view near MCF, (b) shows a cross-sectional enlarged view near a thin fiber. FIG. It is a cross-sectional enlarged view which shows the structure inside the ferrule of the fanout part for MCF which concerns on Embodiment 6 of this invention, (a) is a cross-sectional enlarged view of MCF vicinity, (b) shows the cross-sectional enlarged view of thin fiber vicinity. FIG.

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

Embodiment 1

  FIG. 5 is an overall configuration diagram of the MCF fan-out component according to the first embodiment of the present invention. The MCF fan-out component 100 is connected to the MCF 120 connected to the transmission path side MCF 121 via the MCF connection unit 113 and the light propagating through the plurality of cores of the MCF 120 to the plurality of normal fibers 130 (the same number as the number of cores of the MCF 120). And, conversely, light from the plurality of normal fibers 130 is guided to the plurality of cores of the MCF 120, respectively, the plurality of normal fibers 130, and the plurality of normal fibers 130. Optical connectors and plugs 131 for inputting and outputting are sequentially connected. Here, the MCFs 120 and 121 are MCFs of the type shown in FIG. 1 and have seven cores, and the cladding diameter D is the shortest distance from the center of the core disposed on the outer side to the outer periphery of the cladding. It is set to be half the interval dc between adjacent cores. Usually, the fiber 130 is quartz-based, has a cladding diameter of about 125 μm, and has a coating in a region outside the housing 106.

  6a to 6c show the internal structure of the housing 106 in cross-sectional views. The inside of the housing 106 has ferrules 101 and 102, and portions for guiding the light propagating through the cores 120a of the MCF 120 to the seven small diameter fibers 110 (connection portions between the MCF 120 and the small diameter fibers 110), respectively A portion having seven thin fibers 110 and fiber blocks 103 and 104 and guiding light propagating through each thin fiber 110 to a normal fiber 130 (a connecting portion between the thin fiber 110 and the normal fiber 130); Prepare. Here, the small-diameter fiber 110 is composed of one core and a clad in the cross-sectional direction, and has a smaller clad diameter than a normal optical fiber. The housing 106 can also guide light from the seven normal fibers 130 to the seven small diameter fibers 110 and further to the seven cores of the MCF 120.

  With such a configuration of the fan-out component 100, each light propagated along each core of the MCF 121 is coupled and propagated to each core 120 a of the MCF 120, and enters the seven small diameter fibers 110 inside the housing 106. Further, they are respectively guided to seven normal optical fibers 130 and output from the optical connector plug 131. On the other hand, the light input from the optical connector plug 131 to the normal fiber 130 is guided to the seven small diameter fibers 110, to each core 120 a of the MCF 120, and to each core of the MCF 121.

  Hereinafter, the internal structure of the housing 106 will be described in more detail.

  First, a connection portion between the MCF 120 and the thin fiber 110 will be described. The ferrules 101 and 102 have guide holes 101a and 102a, respectively. The ferrule 101 accommodates seven small-diameter fibers 110, and the ferrule 102 accommodates the MCF 120. That is, the small-diameter fiber 110 and the MCF 120 are inserted into the respective guide holes 101a and 102a, and are fixed to the ferrules 101 and 102 using an adhesive. The outer shape of the ferrules 101 and 102 is roughly a cube. The end face of the ferrule 101 including the end face of the small diameter fiber 110 and the end face of the ferrule 102 including the end face of the MCF 120 are processed into a smooth flat surface perpendicular to the longitudinal axis of the guide holes 101a and 102a by polishing. Hereinafter, as shown in FIG. 6a, the longitudinal direction of the guide holes 101a and 102a is referred to as the Z axis, the direction perpendicular thereto is referred to as the X and Y axes, and the rotation direction about the Z axis is referred to as the θz direction.

  7a and 7b are enlarged cross-sectional views of the vicinity of the MCF 120 in the ferrule 102 and the vicinity of the small-diameter fiber 110 in the ferrule 101, respectively. As shown in FIGS. 7a and 7b, the guide holes 101a and 102a of the ferrules 101 and 102 have a circular cross-sectional shape. In the MCF 120, the cladding diameter D is about 125 μm, and the distance dc between the centers of the adjacent cores 120a is about 41.7 μm (one third of 125 μm). The diameter of the guide hole 102a of the ferrule 102 into which the MCF 120 is inserted is set to about 126 μm. The outer diameter d of the thin fiber 110 (the region inserted into the guide hole 101a) is about 41.7 μm corresponding to the interval dc. The diameter of the guide hole 101a of the ferrule 101 into which the seven thin fibers 110 are inserted is a circle circumscribing the six thin fibers 110 arranged on the outside of the seven thin fibers 110. A value substantially equal to the diameter, that is, about three times the outer diameter d of the thin fiber 110 is set. With such a configuration, the seven small-diameter fibers 110 are arranged in the closest density (so that adjacent small-diameter fibers 110 are in contact or close to contact with each other) by being inserted into the guide hole 101a. The The position of each small-diameter fiber 110 is suppressed by the inner wall of the guide hole 101a and the adjacent small-diameter fiber, and the position is determined.

  The space other than the thin fiber 110 in the guide hole 101a is filled with an adhesive 109, and the thin fiber 110 and the ferrule 101 are fixed. In this state, the position of each core 110a of the small-diameter fiber 110 and the position of each core 120a of the MCF 120 are substantially coincident with each other.

  Note that the connection between the small-diameter fiber 110 and the MCF 120 (matching between the core 110a of each small-diameter fiber 110 and each core 120a of the MCF 120) is realized as follows. First, with the end faces of the ferrules 101 and 102 facing each other, the relative positions of the ferrules 101 and 102 are positioned in the X-axis, Y-axis, Z-axis (gap length of both end faces), and θz-axis directions. Next, both ferrules 101 and 102 are joined by filling the adhesive 109 between both end faces and curing it. The adhesive 109 used here is matched with the refractive index of the optical fiber. As the positioning (alignment) means for the ferrules 101 and 102, active alignment (for example, alignment is performed while light is input from the thin fiber 110 to the MCF 120 and the power of the light emitted from the MCF 120 is monitored). be able to. The joined ferrules 101 and 102 are fixed to the housing 106 (adhesives and the like for fixing are omitted in FIGS. 6a to 6c).

  Next, a connection portion between the thin fiber 110 and the normal fiber 130 will be described. 8a and 8b show the cross-sectional structures of the fiber blocks 103 and 104, respectively. The fiber block 103 accommodates seven small diameter fibers 110. Specifically, the V-groove substrate 103a and the flat substrate 103c are bonded in a state in which the thin fiber 110 is mounted in each V-groove 103b. The fiber block 104 accommodates seven normal fibers 130 (with no coating). Specifically, the V-groove substrate 104a and the flat substrate 104c are bonded in a state where the normal fiber 130 is mounted in each V-groove 104b. In both the fiber blocks 103 and 104, the pitch of the V-grooves 103b and 104b is equal, and the pitch of the small diameter fiber 110 of the fiber block 103 and the pitch of the normal fiber 130 of the fiber block 104 are substantially equal. The end faces of the fiber blocks 103 and 104 including the end face of the small-diameter fiber 110 or the normal fiber 130 are processed into a flat surface perpendicular to the longitudinal direction of the V grooves 103b and 104b by polishing or the like.

  In order to connect the small-diameter fiber 110 and the normal fiber 130, the end faces of the two fiber blocks 103 and 104 are opposed to each other, and the relative positions of the two fiber blocks 103 and 104 are aligned (the X and Y axes have small diameters). The positions of the core 110a of the fiber 110 and the core of the normal fiber 130 are matched, and an adhesive (not shown) is filled between the both end faces and cured, whereby the two fiber blocks 103 and 104 are joined. As alignment means for the fiber blocks 103 and 104, active alignment (for example, positioning is performed while monitoring the power of the light that is normally input from the fiber 130 and output) can be used. The bonded fiber blocks 103 and 104 are fixed to the housing 106 (adhesive and the like for fixing are omitted in FIGS. 8a and 8b).

  Also, an optical connector plug 131 is attached to one end of the normal fiber 130 in order to facilitate connection with other optical fibers and optical components.

  In addition, the mode field diameter (MFD) of light propagating through the cores of the MCFs 120 and 121, the MFD in the small-diameter fiber 110, and the MFD in the normal fiber 130 have a connection loss due to a mismatch of mode fields at the connection portions. In order to reduce, it is desirable to be as equal as possible. In general, the diameter of the guide hole 101a of the ferrule 101 and the outer diameter of the small diameter fiber 110 can be set with high accuracy, so that the relative position of the small diameter fibers in the guide hole 102 is also high. The accuracy can be set. Further, by connecting the optical fiber by joining components such as a ferrule and a fiber block using active alignment, the connection portion between the MCF 120 and the small-diameter fiber 110 by joining the ferrules 101 and 102, and the fiber block 103. , 104 can be reduced in connection loss (attenuation of the power of propagating light) at the connection portion between the small-diameter fiber 110 and the normal fiber 130. Thereby, in the fan-out component 100, the loss of the generated optical power can be reduced.

  Further, as described above, the positioning of the seven small diameter fibers 110 can be easily realized by inserting them into the guide holes 101a of the ferrule 101. For the ferrules 101 and 102, a resin optical connector ferrule (such as an MT ferrule) can be used, but it is preferable to use a glass optical connector ferrule. In the case of a resin optical connector ferrule, a thermosetting type is selected as an adhesive for joining both ferrules 101 and 102. In the case of an optical connector ferrule made of glass, an ultraviolet curable adhesive can be used as the adhesive, which improves workability for bonding. In general, an ultraviolet curable adhesive has a shorter curing time than a thermosetting adhesive or a room temperature curable adhesive.

  In the ferrules 101 and 102, the outer dimensions do not need to be highly accurate, and only the diameters of the guide holes 101a and 102a need only be highly accurate. Moreover, the glass ferrule which has a round hole can be manufactured by the shaping | molding method etc. which use glass as a material. Therefore, even if the ferrules 101 and 102 are made of glass, the cost is not high. Components such as the fiber blocks 103 and 104 are used for connecting an optical waveguide type optical component (such as a splitter or a wavelength demultiplexer) and an optical fiber, and are general components. The fiber blocks 103 and 104 are generally made of glass (the V-groove substrates 103a and 104a and the flat substrates 103b and 104b are made of glass). An agent can be used. Joining of ferrules 101 and 102 or joining with fiber blocks 103 and 104, including alignment by active alignment, is a means generally implemented in the manufacturing process of optical components. Since a thin fiber having an outer diameter of about 41.7 μm is not mass-produced, the manufacturing cost per meter is somewhat higher than a normal optical fiber. However, since a thin fiber does not use 1 m to manufacture one fan-out part, the cost of the thin fiber required to manufacture one fan-out part is not so high. From the above, it can be said that this fan-out component can be manufactured at low cost.

  In general, the outer (maximum) dimension of the ferrules 101 and 102 is 10 mm or less in the direction perpendicular to the longitudinal axis direction of the guide holes 101a and 102a, and 15 mm or less in the longitudinal axis direction of the guide holes 101a and 102a. . The same applies to the outer dimensions of the fiber blocks 103 and 104. Further, the length of the small-diameter fiber in the Z-axis direction, that is, the distance between the ferrule 101 and the fiber block 103 is sufficient to be 30 mm or less. From the above, the housing 106 part of the fan-out component 100 can be made small. The length of the MCF 120 and the length of the normal fiber 130 (the length from the housing 106 to the optical connector plug 131) are appropriately set according to the application.

  The small-diameter fiber 110 accommodated in the ferrule 101 is restrained from changing in position relative to the ferrule 101 due to the contact between the inner wall of the guide hole 101a and the small-diameter fibers 110. Therefore, the position of the thin fiber 110 with respect to the ferrule 101 is stable with respect to temperature / humidity fluctuations and long-term use. The connection using the adhesive between glass ferrules and glass fiber blocks has a proven configuration as described above. The small-diameter fiber 110 between the ferrule 102 and the fiber block 103 is protected by the housing 106. From the above, it can be said that the fan-out component 100 according to the present embodiment has high reliability.

  The connection between the MCF 121 and the MCF 120 includes means such as an optical connector, a mechanical splice, and a fusion connection. In the present embodiment, a plug of a single-core optical connector is usually attached to the fiber 130, but a plug of a multi-fiber optical connector may be used depending on the application. Alternatively, it may be fusion-spliced with another optical fiber. The light propagating through the cores of the MCFs 120 and 121, the small diameter fiber 110, and the normal fiber 130 may be single mode or multimode.

  In the above description, the MCF 120 has seven cores 120a, but there are MCFs with six cores. In such an MCF, the cross-sectional structure is the same as that of the MCF 120, but the core 120a located in the central portion of the cladding outer shape does not exist. With such an MCF, a fan-out component can be configured with the same structure as described above. Also in this case, in order to realize the close-packed arrangement of the thin fibers 110, the number of the thin fibers 110 inserted into the guide holes 101a of the ferrule 101 is seven. Generally speaking, the number of MCF cores and the number of small-diameter fibers do not always match. The number of small diameter fibers is determined so that the small diameter fibers are inserted into the guide holes of the ferrule and are packed most closely.

Embodiment 2

  9a to 9c show the configuration of the MCF fan-out component according to the second embodiment of the present invention. For ease of explanation, FIGS. 9a to 9c show the inside of the housing 206 and the vicinity of the housing in cross-sectional views, respectively, the EE cross-sectional view, the enlarged view of the vicinity of the ferrule of the cross-section AA, and the cross-section BB It is an enlarged view of the ferrule vicinity. The overall configuration of this fan-out component is the same as the overall configuration of the fan-out component 100 of the first embodiment shown in FIG. The MCF 221 (not shown) on the transmission line side and the MCF 220 connected thereto are MCFs of the type shown in FIG. 1 and have seven cores. The light propagating along each core of the MCF 220 is guided to the seven normal fibers 230 inside the housing 206.

  Inside the housing 206, there are ferrules 201 and 202 each having a guide hole 201a and a guide hole 202a. The ferrule 201 accommodates seven small-diameter fibers 210 in the guide hole 201a, and the ferrule 202 contains the MCF 220. It is accommodated in the guide hole 202a, that is, the thin fiber 210 and the MCF 220 are inserted into the respective guide holes 201a and 202a, and are fixed to the ferrules 201 and 202 using an adhesive. It is the same. The configuration in the vicinity of the guide holes 201a and 202a is the same as the configuration in the vicinity of the guide holes 101a and 102a in the first embodiment shown in FIG. The cladding diameter of the MCF 220, the cladding diameter of the thin fiber 210, and the diameter of the guide hole 201a are also the same as in the first embodiment. Similarly, the thin fibers 210 are arranged closest in the guide holes 201 a, and the relative positions of the cores of the thin fibers 210 substantially coincide with the relative positions of the cores of the MCF 220.

  However, the outer shape of both ferrules 201 and 202 is cylindrical, and in addition, a split sleeve 205 is further provided inside the housing 206. The cylindrical centers of the ferrules 201 and 202 and the centers of the guide holes 201a and 202a are substantially coincident. The outer diameters of both ferrules 201 and 202 are about 2.5 mm (the same as the ferrule of a normal single-core optical connector), and the end surfaces (including the end surfaces of the MCF 220 or the small-diameter fiber 210) are guide holes 201a and 202a. It is a flat surface perpendicular to the longitudinal axis. Both ferrules 201 and 202 are inserted into the split sleeve 205 so that their end faces face each other. The cores of the MCF 220 accommodated in the ferrule 202 and the cores of the small-diameter fibers 210 accommodated in the ferrule 201 are aligned by relatively rotating the ferrule 202 and the ferrule 201 (θz direction). The alignment in the X-axis and Y-axis directions is established by inserting both ferrules 201 and 202 into the split sleeve 205. Both ferrules 201 and 202 are bonded together by curing in a state where an adhesive (not shown) is filled between both end faces. The split sleeve 205 is fixed to the housing 206 by a fixing resin 212 on the side opposite to the portion having the slit.

  The thin fiber 210 is usually formed by etching the vicinity of the tip of the fiber 230 (region inserted into the ferrule 201) with hydrofluoric acid or the like to reduce the cladding diameter. Therefore, there is no connection portion between the small-diameter fiber 210 portion and the normal fiber 230 portion. At the end of the housing 206, the normal fiber 230 is fixed to the housing 206 via a fixing block 211. The ferrules 201 and 202, the small-diameter fiber 210, and the like are covered and protected by the housing 206.

  According to the present embodiment, positioning of each core of the MCF 220 and each core of the seven small diameter fibers 210 can be performed only by relatively rotating both the ferrules 201 and 202 within the split sleeve 205. An apparatus in which both ferrules 201 and 202 are relatively rotated can be easily configured, and active alignment can be used for the positioning. Further, as the ferrules 201 and 202 and the split sleeve 205, general single-core optical connector parts can be used. The configuration in which a cylindrical ferrule is inserted into the split sleeve and the optical fibers are connected to each other is adopted for a general single-core optical connector (connection loss is generally 0.3 dB or less and high reliability is recognized). Has been. For these reasons, the fan-out component according to the present embodiment can also reduce the connection loss (insertion loss of this fan-out component) in the connection between the MCF 220 and the small-diameter fiber 210. Further, the manufacturing cost can be reduced, and further high reliability can be obtained.

  The diameter of the ferrules 201 and 202 may be 1.25 mm. This diameter ferrule is employed in MU connectors and LC connectors.

Embodiment 3

  The entire configuration of the MCF fan-out component 300 according to the third embodiment of the present invention is shown in FIG. Also, the internal structure of the housing 306 is shown in cross-section in FIGS. 11a and 11b. The fan-out component 300 corresponds to the MCF of the type shown in FIG. 1 having seven cores, and guides the light propagating through the cores 320a of the MCF 320 to the seven normal fibers 330, respectively. As shown in FIG. 11 a, the inside of the housing 306 is roughly divided into a portion connecting the MCF 320 and the seven small diameter fibers 310, the seven small diameter fibers 310, the small diameter fibers 310 and the normal one. And a portion connecting to the fiber 330. The seven small diameter fibers 310 and the portion connecting the small diameter fiber 310 and the normal fiber 330 are the same as in the first embodiment. Hereinafter, the part which connects MCF320 and the seven small diameter fibers 310 is demonstrated in detail.

  The portion connecting the MCF 320 and the seven small diameter fibers 310 includes a plug 307 including a plug housing 307a, a ferrule 302, a flange 302b, and a spring 307b, a receptacle housing 308a, a ferrule 301, a flange 301b, and a split sleeve. And a receptacle 308 including 305. The receptacle 308 is fixed to the housing 306. The plug 307 can be attached to and detached from the receptacle 308. Thereby, connection and disconnection of the thin fiber 310 accommodated in the ferrule 301 and the MCF 320 accommodated in the ferrule 302 can be repeated.

  The ferrules 301 and 302 and the split sleeve 305 are the same as in the second embodiment, and the MCF 320 and the small-diameter fiber 310 are also accommodated in the ferrule by being inserted into the ferrule guide holes as in the second embodiment. However, the end surfaces of the ferrules 301 and 302 (including the end surfaces of the small-diameter fiber 310 and the MCF 320, respectively) are formed into a smooth (small surface roughness) convex spherical shape by polishing. In a state where the plug 307 is connected to the receptacle 308, the ferrule 302 is pressed toward the ferrule 301 by the spring 307b in the plug 307, and a PC (Physical Contact) between the end face of the MCF 320 and the end face of the small-diameter fiber 310 is realized. However, in FIG. 11, a mechanism for fixing the plug 307 to the receptacle 308 against the reaction when the ferrule 302 is pressed by the spring 307 b is omitted. By realizing this PC, the gap between both end faces disappears, and it is possible to suppress the occurrence of reflection when light passes through both end faces (to obtain a high return loss).

  Further, when the plug 307 is connected to the receptacle 308, the alignment of the ferrule 301 and the ferrule 302 in the relative axis (θz) direction is described below with reference to the technology of the optical connector for polarization maintaining optical fiber. This is realized as follows. When the thin fiber 310 is fixed to the ferrule 301 and the end face of the ferrule 301 is polished, the ferrule 301 and the flange 301b are relatively rotatable about the axis. After the thin fiber 310 is positioned at a predetermined position with respect to the flange 301b in the direction around the axis, the ferrule 301 is fixed to the flange 301b. The above positioning is performed by monitoring the image of the end face of the ferrule 301 (end face of the small diameter fiber 310). In this way, the position of the thin fiber 310 with respect to the flange 301b is determined about the axis. Next, the flange 301b is assembled into the receptacle housing 308a at a predetermined angle around the axis. Thereby, the position of the small diameter fiber 310 in the receptacle 308 is determined. Similarly, the position of the core 320a of the MCF 320 in the plug 307 is also determined. When the plug 307 is connected to the receptacle 308, the position of the plug 307 relative to the receptacle 308 is also determined with respect to the direction around the axis. Here, the means using the optical connector technology for polarization-maintaining optical fiber has been explained. However, a cylindrical ferrule and a split sleeve are used, and the optical fiber to be connected is precisely aligned and connected. The MCF connector technology may be used. In practice, it is desirable that the plug 307 and the receptacle 308 have compatibility in connection with the MCF connector.

  According to this embodiment, in the case of the fan-out components of the first and second embodiments, a connection portion between MCFs that is necessary can be omitted. As a result, the overall length of the fan-out component can be shortened, and the cost can be further reduced. Since the plug 307 and the receptacle 308 can be connected and disconnected manually, workability in construction and maintenance of the optical system using the MCF is improved.

Embodiment 4

  An MCF fan-out component according to Embodiment 4 of the present invention will be described. The configuration of this fan-out component is the same as that of the fan-out component described in the second embodiment shown in FIG. However, the MCF 420 is an MCF of the type shown in FIG. 2, and the cladding diameter is set to a value slightly larger than three times the interval dc between adjacent cores.

  12a and 12b are an enlarged cross-sectional view in the vicinity of the MCF and an enlarged cross-sectional view in the vicinity of the small-diameter fiber, respectively, showing the configuration inside the ferrule of the fan-out component according to this embodiment. The diameter of the guide hole 402 a of the ferrule 402 that accommodates the MCF 420 is substantially equal to the cladding diameter of the MCF 420. The diameter of the guide hole 401a of the ferrule 401 that accommodates the thin fiber is set to a value that is substantially equal to three times the clad diameter d (substantially equal to dc) of the thin fiber. Even if the ferrules 401 and 402 have different diameters of the guide holes 401a and 402a, their center axes substantially coincide with each other when inserted into the split sleeve. Thereby, alignment (positioning) between the ferrules 401 and 402 is established in the X-axis and Y-axis directions. The alignment in the θz direction is performed in the same manner as in the second embodiment.

  Further, this type of MCF 420 can also be applied to the fan-out parts of the first and third embodiments in the same manner as described above.

Embodiment 5

  An MCF fan-out component according to Embodiment 5 of the present invention will be described. This fan-out component is a fan-out component corresponding to an MCF having three cores as shown in FIG. The basic configuration of this fan-out component is the same as that of the second embodiment. The ferrule 502 accommodates an MCF 520 having three cores 520a, and the ferrule 501 accommodates three small-diameter fibers 510. The light propagating along each core 520a of the MCF 520 is guided to three normal fibers.

  13a and 13b are an enlarged cross-sectional view of the ferrule 502 of the fan-out component according to the present embodiment in the vicinity of the MCF 520 and an enlarged cross-sectional view of the ferrule 501 in the vicinity of the small-diameter fiber 510, respectively. An imaginary circle 520c in the cross section of the MCF 520 is a circle centered on the center of the core with the diameter dc between adjacent cores. The outer diameter d of the thin fiber 510 is set to be approximately equal to the interval dc. Further, the diameter D of the guide hole 501a of the ferrule 501 is set to be substantially equal to the value of {1 + 2 / √3} * d. The value of the diameter D is approximately equal to the diameter of a circle circumscribing the three small-diameter fibers 510 when they are arranged closest. When the three small diameter fibers 510 are inserted into the guide holes 501a, the relative positions of the three cores of the small diameter fiber 510 substantially coincide with the relative positions of the three cores 520a of the MCF 520. Regarding the alignment of the ferrule 502 with respect to the ferrule 501, when the ferrules 501 and 502 are inserted into the split sleeve, the alignment in the X-axis and Y-axis directions is established. Further, both the ferrules 501 and 502 can be relatively rotated in the θz direction, so that the positions of the core 520a of the MCF 520 and the core 510a of the small-diameter fiber 510 can be substantially matched.

  The configuration in which the three small-diameter fibers 510 are inserted into the guide holes 501a and the relative positions are determined can also be used in the fan-out components described in the first and third embodiments.

Embodiment 6

  An MCF fan-out component according to Embodiment 6 of the present invention will be described. This fan-out component is a fan-out component corresponding to an MCF having 13 cores as shown in FIG. 14a and 14b are an enlarged cross-sectional view of the ferrule 602 near the MCF 620 and an enlarged cross-sectional view of the ferrule 601 near the small-diameter fiber 610, respectively. It has a ferrule 602 that accommodates 13 MCFs 620 having 13 cores 620 a and a ferrule 601 that accommodates 13 small-diameter fibers 610. The outer diameter d of the small-diameter fiber 610 is substantially equal to the interval dc between adjacent cores, and the diameter D of the guide hole 601a is set to be substantially equal to the value of {1 + 2√3} * d. The value of the diameter D is such that when the 13 fine fibers 610 are arranged closest to the position of the core of the MCF 620, the circle circumscribing the six fine fibers 610 arranged on the outermost side Nearly equal to the diameter. By simply inserting the 13 small-diameter fibers 610 into the ferrule 601, the relative positions of the 13 cores of the thin-fiber 610 substantially coincide with the relative positions of the 13 cores 620a of the MCF 620. The overall configuration of the fan-out component according to this embodiment can be the same as the configuration described in the first to third embodiments.

100, 300 Fanout parts for MCF 120, 121, 220, 221, 320, 420, 520, 620 MCF
120a, 121a, 320a, 420a, 520a, 620a MCF core 120b, 320b, 420b, 520b, 620b MCF cladding 120c, 320c, 420c, 520c, 620c MCF virtual circle 110, 210, 310, 410, 510, 610 Thin fiber 110a, 410a, 510a, 610a Thin fiber core 110b, 410b, 510b, 610b Thin fiber cladding 130, 230, 330 Normal fiber 101, 102, 201, 202, 301, 302, 401, 402, 501, 502, 601, 602 Ferrule 101a, 102a, 201a, 202a, 301a, 302a, 401a, 402a, 501a, 502a, 601a, 602a Guide holes 106, 206, 30 Case 109, 409, 509, 609 Adhesive 131, 331 Optical connector / plug 205, 305 Split sleeve 103, 104 Fiber block 103a, 104a V-groove substrate 103b, 104b V-groove 103c, 104c Flat substrate 113 MCF connection 211 fixed Block 212 Resin for fixing 207b Boot 301b, 302b Flange 307 Plug 307a Plug housing 307b Spring 308 Receptacle 308a Receptacle housing

Claims (4)

A multi-core fiber fan-out component for individually inputting / outputting light to / from the three or more cores with respect to a multi-core fiber having three or more cores,
A first ferrule having a single first guide hole having a circular cross section;
A plurality of first optical fibers housed in the first guide hole, each having a single core and a small diameter less than 125 μm ;
A first fiber block made of glass containing the plurality of first optical fibers, wherein the first fiber block includes the same number of second optical fibers as the plurality of first optical fibers. The second optical fiber is bonded to the second optical fiber block, the first optical fiber is accommodated at the same pitch as the second optical fiber in the second optical fiber block, and the second optical fiber is a core. And a first fiber block having a cladding diameter of 125 μm,
The plurality of first optical fibers have a cladding diameter that is substantially equal to the interval between adjacent cores in the multi-core fiber, and are arranged closest to each other and fixed to the first ferrule.
The diameter of the first guide hole has a value approximately equal to the diameter of a circle circumscribing the plurality of first optical fibers arranged in the close proximity,
The relative position of each core of the plurality of first optical fibers is substantially equal to the relative position of each core of the multi-core fiber,
A fan-out component for a multi-core fiber, wherein light is input to and output from the first optical fiber with respect to the second optical fiber. A second ferrule having a second guide hole for accommodating the multi-core fiber;
The first ferrule and the second ferrule have a cylindrical structure in which a central axis substantially coincides with a central axis of the first guide hole and the second guide hole,
2. The fan-out component for a multi-core fiber according to claim 1, wherein an inner wall is cylindrical and includes a split sleeve that accommodates the first ferrule and the second ferrule. The end face of the first ferrule including the end face of the plurality of first optical fibers and the end face of the second ferrule including the end face of the multi-core fiber are the end faces of the plurality of first optical fibers. Having a smooth convex spherical shape so as to enable physical contact with the end face of the multi-core fiber,
The fan-out component for a multi-core fiber according to claim 2, wherein either or both of the first ferrule and the second ferrule can be inserted into and removed from the split sleeve. The multi-core fiber has six or seven cores, and has seven first optical fibers in the first guide hole of the first ferrule,
The fan-out component for a multi-core fiber according to any one of claims 1 to 3, wherein the diameter of the first guide hole is substantially equal to a value that is three times the cladding diameter of the first optical fiber. .

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