JP2005202200A - Optical fiber collimator and optical component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive optical fiber collimator with comparatively low loss manufactured, using a collimator lens optimized in a certain optical fiber and various optical fibers. <P>SOLUTION: An optical fiber collimator comprising a collimator lens 13 and the optical fiber fused and connected to the collimator lens includes refractivity distribution optimized in a first optical fiber 11 fusing and connecting it by the collimator lens. In the optical fiber collimator 10, one end of the first optical fiber is fused and connected to the collimator lens, a second optical fiber 12 having a structural parameter different from the first optical fiber is fused and connected to the other end of the first optical fiber, and the connection points are stored in a holder 14. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical fiber collimator used in an optical functional component used in the field of optical communication to make light emitted from an optical fiber enter an optical functional element or make light emitted from an optical functional element enter an optical fiber. And an optical component including the same.

  Collimator lenses such as GRIN (Gradient Index) lenses, ball lenses, and aspherical lenses are widely used to propagate light emitted from optical fibers in space. Among them, the GRIN lens can be easily handled, and the collimator lens mainly composed of quartz as described in Patent Document 1 is excellent in reliability because it can be directly fused and connected to the optical fiber.

FIG. 1 is a cross-sectional view showing an example of an optical fiber collimator in which an optical fiber and a collimator lens mainly composed of quartz are fusion-bonded. The optical fiber collimator 1 includes an optical fiber 2, a collimator lens 3 whose one end is fusion-connected, and an optical fiber bare wire 2 </ b> A portion at one end of the collimator lens 3 and the optical fiber 2. Holder 4 and adhesives 5 and 6 which are injected and cured at both ends of the holder 4 and fix the coated portion of the optical fiber 2 and the collimator lens 3 to the holder 4. The optical fiber 2 is a single mode optical fiber that is generally used in the field of optical communication. The outer diameter of the collimator lens 3 is about 0.4 mm, and the lens length is about 1.7 mm.
JP 2002-372604 A JP 2002-40290 A

  The GRIN lens has a refractive index distribution in which the refractive index decreases from the center of the lens toward the outer periphery. When designing a lens, this refractive index distribution is an important factor, and the optimum value is calculated according to the relative refractive index difference between the core and the cladding and the numerical aperture of the optical fiber to be used. Manufactured as follows.

  However, in response to the recent demand for miniaturization of optical components, special fibers having a smaller allowable bending diameter than general single mode optical fibers have come to be used. In a general single mode optical fiber, the relative refractive index difference between the core and the clad is about 0.3%, while the special fiber designed to allow the allowable bending diameter to be smaller The rate difference is designed to be about 0.6%. Further, in a general single mode optical fiber, the clad diameter is about 125 μm and the core diameter is about 10 μm. However, in the special fiber, there is an example in which the clad diameter is about 80 μm and the core diameter is about 7 μm. .

  As described above, the optical fiber used in the optical fiber collimator is no longer limited to one type, and the collimator lens used in the optical fiber collimator also has a relative refractive index difference in each optical fiber. It becomes necessary to design according to the characteristics. This not only increases the design and manufacturing costs of the collimator lens itself, but also increases the number of types of peripheral parts that are used to hold and protect the collimator lens. It becomes a factor to raise.

FIG. 2 uses a collimator lens having a refractive index profile optimized for a general single mode optical fiber (referred to as SM fiber in FIG. 2), and includes a single mode optical fiber and a structure thereof. It is a graph which shows the relationship between the optical fiber to be used and an insertion loss in the optical fiber collimator produced by melt-connecting two types of optical fibers (fiber A, fiber B) with different parameters.
As can be seen from FIG. 2, two types of optical fibers (fiber A and fiber B) having different structural parameters from the single mode optical fiber were connected to a collimator lens having a refractive index profile optimized for the single mode optical fiber. In this case, the insertion loss is higher than that in the case where the single mode optical fiber is fusion-spliced.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a relatively low-loss and low-cost optical fiber collimator manufactured using a collimator lens optimized for a certain optical fiber and various optical fibers.

  To achieve the above object, the present invention provides an optical fiber collimator comprising a collimator lens and an optical fiber fusion-bonded to the collimator lens, wherein the collimator lens is fusion-connected to the first optical fiber. A refractive index profile optimized for the first optical fiber, one end of the first optical fiber is fusion spliced to the collimator lens, and a structural parameter different from that of the first optical fiber is applied to the other end of the first optical fiber. There is provided an optical fiber collimator characterized in that a second optical fiber is fusion-connected and these connection points are accommodated in a holder.

  In the optical fiber collimator of the present invention, it is preferable that the bare optical fiber portion in the holder is recoated with a resin.

  In the optical fiber collimator of the present invention, the first optical fiber is a single mode optical fiber, the collimator lens has a refractive index profile optimized for the single mode optical fiber, and the second light The fiber is preferably configured as an optical fiber having a smaller allowable bending diameter than the first optical fiber.

  The present invention also provides an optical component comprising the optical fiber collimator according to the present invention and an optical functional element that can be optically coupled to the optical fiber collimator.

According to the structure of the optical fiber collimator of the present invention, when a lens optimized for a certain optical fiber is used, an optical fiber collimator having a relatively low loss can be manufactured even if various other optical fibers are used.
In addition, since a relatively low-loss optical fiber collimator can be manufactured even if various other optical fibers are used, it is possible to share lenses and other peripheral parts with respect to various optical fibers. An optical fiber collimator can be produced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 3 is a sectional view showing a first embodiment of the optical fiber collimator of the present invention. The optical fiber collimator 10 is fused and connected to the first optical fiber 11, a collimator lens 13 fused and connected to one end of the first optical fiber 11, and the other end of the first optical fiber 11, A second optical fiber 12 having a structural parameter different from that of the optical fiber 11, a tubular holder 14 that accommodates and reinforces these, and a portion of the second optical fiber 12 that is injected and cured at both ends of the holder 14 And the adhesives 16 and 17 that fix the collimator lens 13 to the holder 14.

  In the present invention, the first optical fiber 11 and the second optical fiber 12 can be appropriately selected from various optical fibers having different structural parameters. For example, the cladding diameter and the mode field diameter (MFD) ) And other silica-based single mode optical fibers. In the present embodiment, the first optical fiber 11 is a single mode light generally used in the optical communication field having a cladding diameter of 125 μm, a core diameter of about 10 μm, and a relative refractive index difference of about 0.3%. The first optical fiber 11 is different from the first optical fiber 11 in the cladding diameter and / or mode field diameter (hereinafter abbreviated as MFD), and is allowed to be bent more than the first optical fiber 11. A special fiber with a small diameter is used.

  The collimator lens 13 has a refractive index distribution optimized for the first optical fiber 11. When the single-mode optical fiber is used as the first optical fiber 11, the collimator lens 13 preferably has an outer diameter of about 0.4 mm and a lens length of about 1.7 mm. The collimator lens 13 does not need to be changed even when the second optical fiber 12 is changed, and the same lens having a refractive index distribution optimized for the first optical fiber 11 can be used in common. Compared with the case where the collimator lens 13 adapted to each of the two types of the optical fibers 12 is manufactured, a low-cost one can be used.

  The holder 14 accommodates at least a connection point 15 between the collimator lens 13 and the first optical fiber 11 and the second optical fiber 12, and injects and cures adhesives 16 and 17 at both end portions to cure the second. By fixing the optical fiber 12 and the collimator lens 13, it has mechanical strength that can protect them. Examples of the holder 14 include a glass tube, a hard plastic tube, a metal tube such as stainless steel, and the like.

  In this optical fiber collimator 10, the first optical fiber 11 is a short bare optical fiber from which the coating on the outer periphery of the cladding has been completely removed, and the second optical fiber 12 has the coating on one end side removed by a predetermined length. The covering removal portion is accommodated in the holder 14. A connection point between one end of the first optical fiber 11 and the collimator lens 13 and a connection point 15 between the first optical fiber 11 and the second optical fiber 12 are accommodated in a holder 14.

  In the optical fiber collimator 10, the connection points are accommodated in a holder 14, a part of a collimator lens 13 protrudes from one end side of the holder 14, and a second optical fiber 12 is drawn from the other end side. Therefore, it is an optical fiber collimator that uses a special fiber (second optical fiber 12) having a small allowable bending diameter in appearance, and can be handled as an optical fiber collimator that actually uses a special fiber.

The optical fibers 11 and 12 having different characteristics can be fused with each other by using a general fusion splicer and determining an optimum fusion condition, so that no special technique is required. For example, a special fiber (first optical fiber) designed so that the allowable bending diameter having a relatively large relative refractive index difference of about 0.6% can be made smaller than that of a general single mode optical fiber (first optical fiber 11). When the two optical fibers 12) are fusion spliced, the insertion loss at the connection point 15 can be 0.05 dB or less.
An example of a connection technique between the collimator lens 13 and the first optical fiber 11 is fusion splicing by irradiating a CO ₂ laser.

  As described above, for example, Patent Document 2 describes a method of reducing coupling loss with an optical device by using connection of optical fibers having different characteristics. The technique relates to a fiber array and is a technique different from the optical fiber collimator of the present invention.

According to this optical fiber collimator 10, a collimator lens 13 having a refractive index profile optimized for a first optical fiber 11 that is a general single mode optical fiber, and an allowable bending diameter more than that of the first optical fiber 11. The insertion loss can be reduced as compared with the structure in which the second optical fiber 12 which is a special fiber having a small length is directly connected.
In addition, since a relatively low-loss optical fiber collimator can be manufactured even if various other optical fibers are used, it is possible to share lenses and other peripheral parts with respect to various optical fibers. An optical fiber collimator can be produced.

  FIG. 5 is a sectional view showing a second embodiment of the optical fiber collimator of the present invention. The optical fiber collimator 10 includes the same components as those of the first embodiment described above, and the same components are denoted by the same reference numerals. The optical fiber collimator 10 according to the second embodiment has a structure in which the outer periphery of the coating removal portion (that is, the optical fiber bare wire portion) of the first optical fiber 11 and the second optical fiber 12 is covered with the resin recoat layer 18. It has become.

  Examples of the material of the resin recoat layer 18 include an ultraviolet (UV) curable resin. In order to form the resin recoat layer 18, an uncured resin liquid is applied to the outer surfaces of the coating removal portions of the first optical fiber 11 and the second optical fiber 12, and the resin is cured by irradiation with ultraviolet light. Can be easily formed.

  The optical fiber collimator 10 according to the second embodiment can obtain the same effect as the optical fiber collimator 10 of the first embodiment described above, and further, the coating removal portion of the first optical fiber 11 and the second optical fiber 12 can be obtained. Since the resin recoat layer 18 is provided on the outer periphery, the optical fiber bare wire portion, in particular, the connection point 15 between the first optical fiber 11 and the second optical fiber 12 is protected by the resin recoat layer 18, so that the durability and reliability are improved The sex can be further improved.

  The optical fiber collimator 10 shown in FIGS. 3 and 5 has a structure (single-core optical fiber collimator) in which one optical fiber 11 is fused and connected to a collimator lens 13. However, the present invention is not limited to this. Instead, a multi-fiber optical fiber collimator in which two or more optical fibers 11 are fusion-connected to the collimator lens 13 can be provided.

FIG. 6 is a cross-sectional view showing an example of the optical component of the present invention.
The optical component 20 includes the above-described optical fiber collimator of the present invention, and includes a two-core optical fiber collimator 21, a single-core optical fiber collimator 22, an optical functional element 23 disposed therebetween, and A cylindrical tubular holder 24 is accommodated.

  As described above, the two-core optical fiber collimator 21 and the single-core optical fiber collimator 22 have one or two first lights on one end side of a collimator lens having a refractive index distribution optimized for the first optical fiber. The fiber is fusion spliced, and the second optical fiber, which is a special fiber capable of reducing the allowable bending diameter, is fusion spliced to the other end of the first optical fiber, and these are housed and fixed in a holder. Yes. Two optical fibers 25A and 25B are drawn out from one end side of the holder 24 of the optical component 20 to form an A port and a B port. In addition, one optical fiber 26 is drawn from the other end side to form a C port.

  The optical component 20 exemplifies an optical multiplexer / demultiplexer, and a dielectric multilayer filter is used as the optical functional element 23. The light of wavelength λ1 and wavelength λ2 incident from the A port is reflected by the optical functional element 23 (dielectric multilayer filter), and the light of wavelength λ2 is transmitted. The reflected light of λ1 is emitted from the B port, and the light of wavelength λ2 that has passed through the optical functional element 23 is emitted from the C port. Thus, by using this optical component 20, light having different wavelengths can be demultiplexed. When used as an optical multiplexer, in contrast to the demultiplexing state shown in FIG. 6, the light of wavelength λ1 is incident from the B port and the light of wavelength λ2 is incident from the C port. And light including the wavelength λ2.

  Since the optical component 20 is configured using the optical fiber collimator according to the present invention described above as the optical fiber collimators 21 and 22, the optical component 20 is manufactured using various optical fibers as the optical fibers 25A, 25B, and 26. Even if it exists, a common collimator lens can be used and an optical component can be produced at low cost.

  In addition, although the said optical component 20 has illustrated the optical multiplexer / demultiplexer which used the dielectric multilayer film filter as the optical functional element 23, the optical component of this invention is not limited to this illustration, As the optical functional element 23 The present invention can be similarly applied to various optical components to which an optical fiber collimator can be applied, such as an optical component using an optical isolator core or the like.

An optical fiber collimator configured as shown in FIG. 3 was produced.
A single mode optical fiber bare wire having a cladding diameter of 125 μm was used as the first optical fiber 11, and one end thereof was fused and connected to the collimator lens 13. The length of the first optical fiber was about 2 mm.
As the collimator lens 13, a cylindrical collimator lens having a lens diameter of 0.4 mm and a lens length of 1.7 mm was used. The refractive index distribution of the collimator lens 13 is optimized for the first optical fiber.
At the other end of the first optical fiber 11, the same single mode optical fiber (referred to as SM fiber in FIG. 4), a special fiber (fiber A, fiber B) having a structural parameter different from this and a small allowable bending diameter (fiber A, fiber B). An optical fiber collimator in which each of the optical fiber collimators is fused and manufactured is accommodated in a holder having a diameter of 1.2 mm and a length of 6 mm, and an adhesive is injected into both ends of the holder and cured to form an optical fiber having a structure shown in FIG. A collimator was made.

The insertion loss was measured for the manufactured optical fiber collimators (1) to (3) below, and the results are shown in FIG.
(1) An optical fiber collimator in which the same single mode optical fiber as the first optical fiber is connected as the second optical fiber,
(2) As a second optical fiber, an optical fiber collimator to which fiber A (cladding diameter of 80 μm, MFD of about 8.5 μm) is connected,
(3) An optical fiber collimator to which a fiber B (cladding diameter: 125 μm, MFD: about 6 μm) is connected as the second optical fiber.

  When comparing the result shown in FIG. 4 with the result of FIG. 2 showing the result of measuring the insertion loss with an optical fiber collimator manufactured by directly fusing various optical fibers to the same collimator lens, the present invention As described above, a collimator lens optimized for the first optical fiber is used as a common lens, one end of the first optical fiber is fusion-bonded to the collimator lens, and the other end of the second optical fiber is It can be seen that a relatively low-loss optical fiber collimator can be produced by fusion-bonding a second optical fiber having a structural parameter different from that of the first optical fiber, such as the fiber A or B.

It is sectional drawing which illustrates the structure of the conventional optical fiber collimator. It is a graph which shows the result of having measured the insertion loss with the optical fiber collimator produced by directly melt-connecting various optical fibers to the same collimator lens. It is sectional drawing which shows 1st Example of the optical fiber collimator of this invention. It is a graph which shows the result of having measured insertion loss with the optical fiber collimator of the present invention. It is sectional drawing which shows 2nd Example of the optical fiber collimator of this invention. It is sectional drawing which shows an example of the optical component of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Optical fiber collimator, 11 ... 1st optical fiber, 12 ... 2nd optical fiber, 13 ... Collimator lens, 14 ... Holder, 15 ... Connection point, 16, 17 ... Adhesive, 18 ... Resin recoat layer, 20 DESCRIPTION OF SYMBOLS ... Optical component, 21 ... Two-core optical fiber collimator, 22 ... Single-core optical fiber collimator, 23 ... Optical functional element, 24 ... Holder, 25A, 25B, 26 ... Optical fiber.

Claims (4)

In an optical fiber collimator comprising a collimator lens and an optical fiber fused and connected to the collimator lens,
The collimator lens has a refractive index profile optimized for a first optical fiber fused to the collimator lens, and one end of the first optical fiber is fused to the collimator lens, and the first optical fiber is fused. A second optical fiber having a structural parameter different from that of the first optical fiber is fused and connected to the other end of the optical fiber, and these connection points are housed in a holder.   2. The optical fiber collimator according to claim 1, wherein a bare optical fiber portion in the holder is recoated with a resin.   The first optical fiber is a single-mode optical fiber, the collimator lens has a refractive index profile optimized for the single-mode optical fiber, and the second optical fiber is more than the first optical fiber. The optical fiber collimator according to claim 1 or 2, wherein the optical fiber has a small allowable bending diameter. An optical component comprising: the optical fiber collimator according to any one of claims 1 to 3; and an optical functional element that can be optically coupled to the optical fiber collimator.

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