JP2008292660A - Optical fiber and optical communication module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber which can be incorporated as an optical transmission means in the internal space of compact electronic equipment while keeping a wired shape resisting against the recovery force of a primary coated optical fiber. <P>SOLUTION: The optical fiber 10 has a bare optical fiber 13 composed of a core 11 and a clad 12 which surrounds the core 11. Further, a resin coat film 14 is formed around the bare optical fiber 13 and the bare optical fiber 13 and the resin coat film 14 compose the primary coated optical fiber 15. The core 11 is formed so as to have a diameter of 50 μm or larger and not larger than 62.5 μm, and of a material including at least quartz. The perimeter of the primary coated optical fiber 15 is covered by a first metallic coat 16. Further, the perimeter of the first metallic coat 16 is covered by a second metallic coat 17. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical fiber and an optical communication module formed by coupling a light emitting element and a light receiving element using the optical fiber.

  In recent years, in high-speed communication devices such as servers, video information devices such as game machines, or small electronic devices such as mobile phones, the transmission speed of information signals inside the devices has been dramatically increased with the increase in functionality. . For this reason, in order to exchange signals even faster and more reliably, optical wiring using optical fibers or the like instead of conventional metal wiring is being studied.

  In these devices, high-density mounting of electronic boards and integration of wiring are advancing, and there is a strong demand for space saving and thinning of optical transmission / reception modules that connect the inside and between the boards. For this reason, in addition to thinning of the optical transmission / reception unit, it is necessary to reduce the thickness of the optical fiber serving as the optical transmission path and to maintain the wiring shape of the optical fiber wired by bending between the components mounted at high density. .

  Conventionally, however, it has been difficult to maintain the shape of the optical fiber when the optical fiber is wired. In other words, unlike conventional metal wiring, optical fibers are less likely to be plastically deformed, and even when the optical fiber is bent according to the shape of the wiring at the time of wiring, it becomes a stable wiring shape (for example, a straight shape) by its own repulsive force. This is because the power to return is strong. For this reason, even if the optical fiber is wired in accordance with a predetermined wiring shape, the optical fiber floats up at an unintended place with time, which may hinder the use of the device.

In order to deal with such a problem, for example, Patent Document 1 discloses that an optical fiber is clothed by sandwiching the optical fiber with a resin sheet having an adhesive layer in a state where the optical fiber is bent into a predetermined wiring shape. An optical fiber sheet that is fixed in a linear shape is described.
However, in the invention disclosed in Patent Document 1, although the optical fiber sheet can be held in a desired wiring shape by suppressing the repulsive force of the optical fiber, it is extremely difficult to change the wiring of the optical fiber once it is manufactured. There is a problem that it is difficult, the degree of freedom in manufacturing is low, and the manufacturing cost is high.

As shown in FIG. 6, for example, in Patent Document 2, a resin tube 103 is covered in parallel with the optical fiber 101 and the metal wire 102, and the shape holding force (plastic deformation force) of the metal wire 102 causes the optical fiber 101. An invention for maintaining the wiring shape is described.
However, in the invention disclosed in Patent Document 2, the outer diameter is inevitably increased due to the structure in which the optical fiber 101 and the metal wire 102 are arranged in parallel and the resin tube 103 is further covered. There were restrictions on wiring to advanced electronic equipment.

Further, as shown in FIG. 7, for example, in Patent Document 3, a spiral metal tube 111 is arranged so as to surround the optical fiber 110, and the wiring shape of the optical fiber 110 is changed by the shape holding force of the metal tube 111. The invention to maintain is described.
However, in the invention disclosed in Patent Document 3, since the spiral metal tube 111 is surrounded around the optical fiber 110, it is inevitable that the outer diameter is increased as in Patent Document 2, and the small size is reduced. However, there has been a limitation in wiring to electronic devices that have become thinner.

As shown in FIG. 8, for example, in Patent Document 4, a thickness of 5 to 15 μm is provided around an optical fiber 122 of a resin coating 121 having an optical fiber core 120 having a diameter of 5.6 μm or less or 10 μm. An optical fiber coil sensor in which an optical fiber 125 in which a first metal film 123 and a second metal film 124 having a thickness of 5 to 50 μm are formed around the first metal film 123 is wound in a coil shape. Is described.
However, in the invention disclosed in Patent Document 4, since the diameter of the optical fiber core 120 is too small, for example, when connecting a light-emitting element or a light-receiving element for signal transmission / reception to both ends of the optical fiber 125, a condensing lens is used. Required. For this reason, when the optical fiber disclosed in Patent Document 4 is used as a signal transmission / reception means of various information devices, a condensing lens or the like is added, which hinders an increase in manufacturing cost, a reduction in size, and a reduction in thickness. .

Further, as shown in FIG. 9, for example, Patent Document 5 describes a metal coated optical fiber cable 132 including a metal coated portion 131 for signal transmission and power feeding around an optical fiber 130.
However, in the invention disclosed in Patent Document 5, the metal coating portion 131 surrounding the optical fiber 130 is formed for the purpose of signal transmission and power feeding, and functions such as maintaining the wiring shape of the optical fiber 130. Is not prepared.
JP 2001-255417 A JP 2001-116964 A JP 2005-114862 A JP 2005-208025 A JP-A 62-108412

  The present invention has been made in view of the above circumstances, and can be incorporated as an optical transmission means even in the internal space of a small electronic device while maintaining the wiring shape against the restoring force of the optical fiber. An object is to provide an optical fiber.

  Another object of the present invention is to provide an optical communication module in which a wired optical fiber is lifted by a restoring force so that no problem occurs in signal transmission.

An optical fiber according to claim 1 of the present invention includes an optical fiber core comprising at least a quartz-containing optical fiber core and a resin coating that covers the optical fiber core, and a first metal coating that covers the optical fiber strand. And an optical fiber having a second metal coating covering the first metal coating, wherein the optical fiber core has a diameter of 50 μm or more and 62.5 μm or less, and the first optical fiber is bent when the optical fiber is bent. The optical fiber is held in a bent state by a metal film and / or a second metal film.
An optical fiber according to a second aspect of the present invention is the optical fiber according to the first aspect, wherein the thickness of the first metal coating is in the range of 0.1 μm to 5 μm.
An optical fiber according to a third aspect of the present invention is the optical fiber according to the first or second aspect, wherein the thickness of the second metal coating is in the range of 50 μm or more and 95 μm or less.
An optical fiber according to a fourth aspect of the present invention is the optical fiber according to any one of the first to third aspects, wherein the first metal coating is a single element selected from Cu, Ni, Sn, Cr and Zn, or at least It is an alloy composed of two or more elements.
The optical fiber according to claim 5 of the present invention is the optical fiber according to any one of claims 1 to 4, wherein the second metal coating is a single element selected from Cu, Ni, Cr, Zn, Ag, and Au. Or an alloy composed of at least two elements.
An optical communication module according to claim 5 of the present invention includes a printed circuit board, a submount substrate in which one or both of a light emitting element and a light receiving element are mounted on a side surface, and between the light emitting element and the light receiving element. The light emitting element and the light receiving element are arranged such that their light emitting and light receiving directions are parallel to the printed circuit board via the submount substrate. The optical communication module is mounted on the printed circuit board so that the light emitting element and the light receiving element of the submount substrate and the end of the optical fiber adjacent to the light emitting element and the light receiving element are covered with a resin, The optical cable includes an optical fiber core including at least a quartz-containing optical fiber core and a resin coating that covers the optical fiber core, and a first gold covering the optical fiber core. And a second metal film covering the first metal film, wherein the diameter of the optical fiber core is not less than 50 μm and not more than 62.5 μm, and when the optical fiber is bent, the first metal film And / or a structure in which the bent state of the optical fiber is held by the second metal film.
The optical fiber strand according to claim 7 of the present invention is an optical fiber strand composed of an optical fiber core containing at least quartz and a resin coating that covers the optical fiber core, and the diameter of the optical fiber core is 50 μm. The above is 62.5 μm or less.

  According to the optical fiber of the present invention, even if the core has a relatively large diameter of 50 μm or more and 62.5 μm or less, and thus has a strong repulsive force (restoring force) against bending, Since the optical fiber strand is covered with the two metal coatings of the metal coating, the optical fiber element is caused by the plastic deformation property of the first metal coating and the second metal coating and the elastic limit stress exceeding the repulsive force of the core. It becomes possible to hold the wire in a bent state.

  For this reason, for example, even when an optical fiber is bent on a substrate as a light transmission body in a small electronic device and wired (wired), the optical fiber is lifted off the substrate in an attempt to restore the shape before bending. In addition, it is possible to reliably prevent problems such as bending on the substrate in an unexpected direction and causing a transmission failure.

  Also, in the process of wiring the optical fiber 10 on a substrate, for example, after the optical fiber 10 is bent into a predetermined wiring shape, the optical fiber 10 is pressed so as not to be restored to the original shape by a repulsive force. Even if it is not, the optical fiber 10 is kept in the wiring shape, so that the wiring process of the optical fiber 10 can be greatly facilitated.

  According to the optical fiber having such a configuration, since the core having a relatively large diameter of 50 μm or more and 62.5 μm or less and having an excellent information transmission amount is provided, for example, at both ends of the optical fiber for signal transmission / reception. When connecting the light emitting element and the light receiving element, it is not necessary to provide a condensing lens or the like. For this reason, it can contribute to thickness reduction and size reduction of the apparatus which wires an optical fiber.

  Further, according to the optical communication module of the present invention, the optical fiber for optically coupling the light emitting element and the light receiving element has a relatively large diameter of 50 μm or more and 62.5 μm or less, and therefore repulsive force (restoring force) against bending. ) Has a strong core, the optical fiber is covered with two layers of the first metal film and the second metal film, so that the first metal film and the second metal film are plastically deformed. The elasticity and the elastic limit stress exceeding the repulsive force of the core enable the optical fiber to be held in a bent state.

  For this reason, even if the optical fiber is wired almost horizontally and close to the printed circuit board, the optical fiber is held in the bent state, and the optical fiber is lifted from the printed circuit board by the repulsive force of the optical fiber. Therefore, it is possible to reliably prevent a problem such as bending in an unexpected direction and causing a transmission failure. As a result, the thickness of the optical communication module can be suppressed to within a few millimeters from the mounted printed board, and a highly reliable optical communication module that can be reduced in size and thickness can be provided.

  Hereinafter, an embodiment of an optical fiber according to the present invention will be described with reference to the drawings. The present invention is not limited to such an embodiment. In addition, in the drawings used in the following description, in order to make the features of the present invention easier to understand, there is a case where a main part is shown in an enlarged manner for convenience, and the dimensional ratio of each component is the same as the actual one. Not necessarily.

  FIG. 1 is a cross-sectional view showing the configuration of the optical fiber of the present invention. The optical fiber 10 has a bare optical fiber 13 composed of a core (optical fiber core) 11 and a clad 12 surrounding the core 11. Further, a resin coating 14 is formed around the bare optical fiber 13, and the bare optical fiber 13 and the resin coating 14 constitute an optical fiber strand 15.

  The core 11 has a diameter of 50 μm or more and 62.5 μm or less, and is made of a material mainly composed of quartz. The periphery of the optical fiber 15 is covered with a first metal coating 16. The periphery of the first metal film 16 is further covered with a second metal film 17.

  According to the optical fiber 10 having such a configuration, even if the core 11 having a relatively large diameter of 50 μm or more and 62.5 μm or less and thus having a strong repulsive force (restoring force) against bending, the first metal Since the optical fiber 15 is covered with two layers of the metal coating 16 and the second metal coating 17, the plastic deformability of the first metal coating 16 and the second metal coating 17, and the repulsive force of the core 11. It becomes possible to hold | maintain the optical fiber strand 15 in the bent state by the elastic limit stress exceeding this.

  For this reason, for example, even when the optical fiber 10 is bent as an optical transmission body in a small electronic device and wired (wired) on the substrate or the like, the optical fiber 10 tries to restore the shape before bending from the substrate. Problems such as floating or bending in an unexpected direction on the substrate to cause a transmission failure can be reliably prevented.

  Also, in the process of wiring the optical fiber 10 on a substrate, for example, after the optical fiber 10 is bent into a predetermined wiring shape, the optical fiber 10 is pressed so as not to be restored to the original shape by a repulsive force. Even if it is not, the optical fiber 10 is kept in the wiring shape, so that the wiring process of the optical fiber 10 can be greatly facilitated.

  According to the optical fiber 10 having such a configuration, the core 11 having a relatively large diameter of 50 μm or more and 62.5 μm or less and having an excellent amount of information transmission is provided. There is no need to provide a condensing lens or the like when connecting a light emitting element or a light receiving element for signal transmission / reception. For this reason, it can contribute to thickness reduction and size reduction of the apparatus which wires the optical fiber 10. FIG.

  The bare optical fiber 13 preferably has a larger diameter of the core 11 than that of the single mode fiber and can easily be optically coupled to the light emitting element and the light receiving element. As the bare optical fiber 13, it is also possible to use a bare GI optical fiber having a core 11 having an outer diameter of 62.5 μm and a cladding 12 having an outer diameter of 125 μm.

  For example, polyimide is preferably used for the resin coating 14 from the viewpoint of excellent heat resistance and chemical stability and durability against the coating treatment of the metal coating. Further, the resin coating 14 can be made of an ultraviolet curable resin or a silicone resin. The resin coating 14 may be not only a single layer but also a resin coating composed of two or more layers formed outside the bare optical fiber 13. The thickness of such a resin film 14 should just be formed in about 5-40 micrometers, for example.

  The first metal film 16 is formed, for example, with Cu as a main component. In addition, examples of the material constituting the first metal film 16 include a single element selected from Cu, Ni, Sn, Cr and Zn, or an alloy composed of at least two elements.

  When electroless plating is used to form the first metal coating 16, it is generally necessary to use Cu, Ni, or Sn as a metal that can be electrolessly plated. However, other formation methods are not limited thereto. However, in vacuum deposition and sputtering, it is practically difficult to increase the thickness of the coating as compared with electroless plating. Preferably mentioned.

  The thickness of the first metal coating 16 is preferably in the range of 0.1 μm or more and 5 μm or less, and particularly preferably about 1 μm. As an example of a method of forming such a first metal film 16, it is formed using electroless plating. The treatment chemical solution is an electroless copper plating bath chemical solution (trade name: OPC Copper (Okuno Pharmaceutical Co., Ltd.)) to which formalin is added as a reducing agent, and the chemical temperature is maintained at 30 ° C. until a predetermined film thickness is obtained. Plating treatment was performed.

  In addition to the electroless plating, the first metal film 16 can be formed by vacuum deposition or sputtering, and the first metal film 16 can be formed by combining two or more of these methods. You may do it. The first metal film 16 also serves as an underlayer for the second metal film 17 described later. Therefore, if the thickness is 0.1 μm or less, the thickness of the second metal film 17 tends to be non-uniform, which is not preferable. On the other hand, when the thickness is 5 μm or more, it takes a long time to form a film, resulting in poor productivity and high manufacturing cost.

  The second metal film 17 is formed, for example, with Cu as a main component. In addition, examples of the material constituting the second metal film 17 include a single element selected from Cu, Ni, Cr, Zn, Ag, and Au, or an alloy composed of at least two elements. A Cu—Zn alloy or a Cu—Ni alloy can also be used. The second metal coating 17 can be made of a metal that is considered preferable by an actual wiring operator in consideration of color and the like, but has a rigidity necessary to hold the optical fiber 15 in a bent state. It is desirable that The metal described above is suitable because of factors such as high rigidity and good color.

The thickness of the second metal coating 17 is preferably in the range of 50 μm or more and 95 μm or less, particularly preferably about 60 μm. As an example of a method for forming such a second metal coating 17, it is formed using electroless plating. As a treatment chemical solution, copper sulfate plating bath chemical solution (mixed in a weight ratio of sulfuric acid 4 to copper sulfate pentahydrate 1 and added with 50 ppm of chlorine ions, additive (trade name: cover cream, manufactured by Meltex) In the chemical solution, a current density of 2.5 A / dm ² is applied to the second metal film 17 in a chemical solution, and plating is performed until a predetermined thickness is reached.

  In addition, the chemical | medical solution can also use the copper bromide bath generally used for electrolytic copper plating, or a copper pyrophosphate bath other than what was mentioned above. Such a second metal coating 17 can efficiently increase the thickness of the metal coating using the first metal coating 16 as an underlayer, and the thickness required to maintain the bending state of the optical fiber 15. In addition, it can be reached in a relatively short time. If the thickness of the second metal coating 17 is less than 50 μm, the bending state of the optical fiber 15 may not be maintained due to insufficient plastic force. On the other hand, if the thickness of the second metal coating 17 exceeds 95 μm, the second metal coating 17 becomes too hard, and there is a possibility that the second metal coating 17 may crack when the optical fiber 10 is bent.

  It is also preferable to form an insulating film made of an insulating resin around the second metal film 17. As this insulating film, for example, it is only necessary to have softness and greenness to such an extent that plastic deformation of the first metal film 16 and the second metal film 17 is not hindered. Preferred examples of the insulating resin that covers the second metal film 17 include silicone resin and styrene rubber.

Next, the optical communication module of the present invention will be described. FIG. 2 is a schematic diagram showing the configuration of the optical communication module of the present invention.
The optical communication module 20 of the present invention includes a printed circuit board 21 and a submount substrate 24 on which one or both of the light emitting element 22 and the light receiving element 23 are mounted. Further, an optical fiber 25 is provided between the light emitting element 22 and the light receiving element 23 so as to be optically coupled to these elements.

  The light emitting element 22 and the light receiving element 23 are mounted on the printed circuit board 21 via the submount substrate 24 so that their light emission and light receiving directions are parallel to the printed circuit board 21. Further, the light emitting element 22 and the light receiving element 23 and the end portion of the optical fiber 25 adjacent to them are covered with a resin 26. The resin 26 is preferably a UV curable resin, for example.

  An optical fiber 25 that optically couples (transmits an optical signal) between the light emitting element 22 and the light receiving element 23 of such an optical communication module 20 includes a core (optical fiber core) 31, as shown in FIG. An optical fiber bare wire 33 including a clad 32 surrounding the core 31 is provided. Further, a resin coating 34 is formed around the bare optical fiber 33, and the bare optical fiber 33 and the resin coating 34 constitute an optical fiber 35.

  The core 31 has a diameter of 50 μm or more and 62.5 μm or less, and is formed of a material containing at least quartz. The periphery of the optical fiber 35 is covered with a first metal film 36. The periphery of the first metal film 36 is further covered with a second metal film 37. In addition, an insulating coating 38 made of an insulating resin such as styrene rubber is preferably formed around the second metal coating 37. The insulating coating 38 is formed with a thickness of about 100 μm, for example.

  According to the optical communication module 20 having such a configuration, the optical fiber 25 that optically couples the light emitting element 22 and the light receiving element 23 has a relatively large diameter of 50 μm or more and 62.5 μm or less, and thus repels bending. Even if the core 31 having a strong force (restoring force) is provided, since the optical fiber strand 35 is covered with the two metal coatings of the first metal coating 36 and the second metal coating 37, these first metal coatings are provided. Due to the plastic deformability of 36 and the second metal coating 37 and the elastic limit stress exceeding the repulsive force of the core 31, the optical fiber 35 can be held in a bent state.

  For this reason, even if the optical fiber 25 is wired substantially horizontally and close to the printed circuit board 21, the optical fiber 25 is held in the wired bending state, and the repulsive force of the optical fiber strand 35 causes the printed fiber 21 to move away from the printed circuit board 21. Problems such as floating or bending in an unexpected direction on the substrate to cause a transmission failure can be reliably prevented. As a result, the thickness of the optical communication module 20 can be suppressed to within 5 mm from the mounted printed circuit board 21, and the highly reliable optical communication module 20 corresponding to downsizing and thinning can be provided. Become.

The effect of the optical fiber of the present invention was verified. In the verification, the shape retention of the optical fiber of the present invention (Example) and the conventional optical fiber (Comparative Example) was measured.
First, a method for measuring the shape retention force will be described. As shown in FIG. 4A, a SUS mandrel M having an outer diameter of 30 mm was used, and the central portion of the optical fiber F having a total length of 1 m was wound around the mandrel M almost perpendicularly with an unreasonable force. In this state, the mandrel M was removed, and the optical fiber F was left for a predetermined time.

Then, as shown in FIG. 4B, with reference to the maximum inner diameter r1 of the ring-shaped bent portion of the optical fiber F immediately after being left for a predetermined time, the maximum inner diameter r2 after 24 hours and after 48 hours has elapsed. Each was measured and the strain release rate P was defined according to the following formula (a).
P = ((r2-r1) / r1) × 100 (%) (a)
It is defined that the strain retention is 5% or less, the maximum inner diameter after 24 hours and the maximum inner diameter after 48 hours are substantially unchanged, and the shape retention force is good.

  Examples 1 to 18 of the present invention shown in Table 1 and conventional optical fibers of Comparative Examples 1 to 5 were prepared.

The symbols shown in the table are as follows.
“Model name of bare optical fiber” A1: GI fiber “Material of resin coating structure” B1: Polyimide
B2: Silicone
B3: Acrylic UV resin

  Examples 1 to 18 are examples of the present invention in which the optical fiber was prepared by changing the metal type and thickness of the first metal coating or the second metal coating with respect to the GI optical fiber. Moreover, the comparative example 1 has shown the conventional optical fiber whose thickness of a 2nd metal film is less than 50 micrometers less than a preferable range. Comparative example 2 shows a conventional optical fiber in which the thickness of the first metal coating is smaller than the preferred range and less than 0.1 μm. Comparative Example 3 shows a conventional optical fiber in which the thickness of the second metal coating is 150 μm thicker than the preferred range. Furthermore, Comparative Example 4 shows a conventional optical fiber in which the thicknesses of the first metal coating and the second metal coating are both 5 μm and 95 μm, which are thicker than the preferred ranges. Comparative Example 5 shows a conventional optical fiber (optical fiber strand) in which neither the first metal coating nor the second metal coating is formed. Comparative Example 6 shows a conventional optical fiber in which only the first metal film is formed.

And the maximum height which the optical transmission / reception module which shows the strain release rate in Examples 1-18 and Comparative Examples 1-6 and the lift from the printed circuit board of an optical fiber occupied was measured. The shape of the optical transceiver module is the same as that shown in FIG.
According to the verification results shown in the evaluation items in Table 1, the shape retention strength of all of Examples 1 to 18 showed good characteristics with a strain release rate of less than 5%. On the other hand, Comparative Example 1, Comparative Example 5, and Comparative Example 6 had a large strain release rate and could not sufficiently maintain the wiring shape. Although Comparative Example 2, Comparative Example 3, and Comparative Example 4 have a strain release ratio of less than 5%, Comparative Example 2 is an optical fiber compared to Example 2 in which a metal coating is made of the same metal. The thickness of the intermediate part was only 30 μm, and the thickness of the second metal film was uneven. Compared with Example 3 in which the metal film is made of the same metal, Comparative Example 3 has a problem in productivity because the time required for electrolytic plating is three times longer. In Comparative Example 4, when the movement of bending and returning to the straight line was repeated three times, the metal coating and the optical fiber wire were cracked together, and there was a problem that they could not be used.

  Next, the wiring properties were verified using the optical fibers of Examples 1 to 18 and Comparative Examples 1 to 6. As shown in FIG. 5, in the method for verifying the wiring property, the optical fiber F was aligned to a length of 50 cm. Using this, an optical transceiver module 51 was produced. Separately, as an evaluation substrate, a 10 mm square (2 mm height) acrylic block 53 simulating an electronic component is provided on the outer periphery of a flat unprocessed glass epoxy substrate 52 (30 cm square, 1.6 mm thick). They were arranged in a row at 10 mm intervals and adhered with double-sided tape.

  Further, the optical transceiver module 51 is bent 90 degrees with a finger so that the central portion of the optical fiber F has a bending radius (inner diameter) of 15 mm (see R portion in FIG. 5), and the glass epoxy substrate 52 and the acrylic block 53. It was deformed so as to be wired along the line and left in this state for 24 hours. Thereafter, the amount of floating of the optical fiber F from the glass epoxy substrate 52 is measured, and an electric signal of 2.5 GHz is input to the optical transmitter by the pulse pattern generator, and the output from the optical receiver is measured as a bit error rate measuring device. The error rate was measured.

  The wiring properties were good in Examples 1 to 18 in which there was little lift of the optical fiber and the maximum height of the optical transceiver module was less than 5 mm. Furthermore, although not shown in the table, in both cases, an input signal of 2.5 GHz could be transmitted without error. On the other hand, in Comparative Example 1, Comparative Example 5, and Comparative Example 6, the optical fiber moved from the initial wiring state, contacted or climbed on the acrylic block, and the maximum height of lifting from the substrate exceeded 5 mm. In Comparative Examples 2 and 3, although the optical fiber has little lift, as described in the section of shape retention force, inconvenience in handling during wiring, low productivity, and low repeated bending strength. There was difficulty in that respect.

It is sectional drawing which shows an example of the optical fiber of this invention. It is the top view and sectional drawing which show an example of the optical communication module of this invention. It is sectional drawing which shows an example of the optical fiber used for the optical communication module of this invention. It is explanatory drawing which shows the verification method in the Example of this invention. It is explanatory drawing which shows the verification method in the Example of this invention. It is a perspective view which shows the conventional optical fiber. It is sectional drawing which shows the conventional optical fiber. It is sectional drawing which shows the conventional optical fiber. It is sectional drawing which shows the conventional optical fiber.

Explanation of symbols

10 optical fiber, 11 core, 12 clad, 13 optical fiber bare wire, 14 resin coating, 15 optical fiber strand, 16 first metal coating, 17 second metal coating.

Claims (7)

An optical fiber strand made of a silica-based optical fiber core and a resin coating covering the optical fiber core, a first metal coating covering the optical fiber strand, and a second metal coating covering the first metal coating An optical fiber,
The diameter of the optical fiber core is 50 μm or more and 62.5 μm or less,
An optical fiber having a structure in which when the optical fiber is bent, the optical fiber is kept bent by the first metal film and / or the second metal film.   The optical fiber according to claim 1, wherein the thickness of the first metal coating is in the range of 0.1 μm to 5 μm.   The optical fiber according to claim 2, wherein the thickness of the second metal coating is in the range of 50 µm or more and 95 µm or less.   The first metal film is a metal composed of a single element selected from Cu, Ni, Sn, Cr and Zn, or an alloy composed of at least two elements. An optical fiber according to claim 1.   The second metal film is a metal composed of a single element selected from Cu, Ni, Cr, Zn, Ag, and Au, or an alloy composed of at least two elements. 5. The optical fiber according to any one of 4 to 4. A printed circuit board, a submount substrate in which one or both of a light emitting element and a light receiving element are mounted on a side surface, and an optical fiber provided between the light emitting element and the light receiving element so as to be optically coupled to these elements; The light emitting element and the light receiving element are mounted on the printed circuit board via the submount substrate so that their light emission and light receiving directions are parallel to the printed circuit board, and An optical communication module in which a light emitting element and a light receiving element of a mounting substrate and an end portion of the optical fiber adjacent to these are covered with a resin,
The optical cable includes an optical fiber element comprising a silica-based optical fiber core and a resin film covering the optical fiber core, a first metal film covering the optical fiber element, and a second metal film covering the first metal film And the optical fiber core has a diameter of 50 μm or more and 62.5 μm or less, and when the optical fiber is bent, the optical fiber element is formed by the first metal film and / or the second metal film. An optical communication module having a structure in which a wire is bent. An optical fiber comprising a silica-based optical fiber core and a resin film covering the optical fiber core,
The diameter of the said optical fiber core is 50 micrometers or more and 62.5 micrometers or less, The optical fiber strand characterized by the above-mentioned.

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