JP4470799B2 - Optical module - Google Patents

Description

  The present invention relates to an optical module using a fiber stub.

An optical module having an optical element such as a light emitting element or a light receiving element and a fiber stub is known. The fiber stub has a tubular ferrule and an optical fiber inserted into the through hole of the ferrule. The fiber stub optically couples an optical fiber for transmission and an optical element attached from the outside (see, for example, Patent Documents 1 and 2).
JP 2002-250844 A JP 2003-107289 A

  However, in the conventional optical module, the transmission characteristics may be deteriorated.

  Accordingly, an object of the present invention is to provide an optical module using a fiber stub that can reduce deterioration of transmission characteristics.

  The inventor of the present application has found that the deterioration of the transmission characteristics of the optical module is due to stray light propagating through the cladding or ferrule of the fiber stub. For example, when the mode field diameter of the light emitted from the light emitting element is different from the mode field diameter of the fiber stub optical fiber, a part of the light enters the clad or ferrule in addition to the core of the optical fiber.

  Part of the light incident on the cladding is reflected at the interface between the cladding and the ferrule, and becomes stray light that propagates in the cladding. The other part of the light incident on the clad passes through the interface between the clad and ferrule and is reflected at the outer interface of the ferrule, and a part of the light passes through the interface between the clad and ferrule and passes through the clad. Propagating stray light. The light incident on the ferrule is reflected at the outer interface of the ferrule, and a part of the light passes through the interface between the clad and the ferrule and becomes stray light propagating in the clad.

  These stray lights enter the cladding of the transmission optical fiber connected to the optical module, enter the core of the transmission optical fiber, and couple with the signal light. Such coupling between the signal light and the stray light causes deterioration in transmission characteristics of the optical module.

  In order to prevent such stray light, the first optical module according to the present invention includes a fiber stub and an optical element optically coupled to one end of the fiber stub, the fiber stub includes a tubular ferrule, An optical fiber including a core and a clad covering the periphery of the core and inserted into the through hole of the ferrule, and at least one of one end face of the clad, the other end face of the clad, one end face of the ferrule, and the other end face of the ferrule And a light reflecting film provided on the surface.

  According to the first optical module, the light reflecting film reflects the light that can become stray light at the end face of the clad or ferrule, so that stray light coupled to the signal light is reduced. Therefore, the deterioration of the transmission characteristics of the optical module is reduced.

  The light reflectance of the light reflecting film is preferably 90% or more.

  A second optical module according to the present invention includes a fiber stub and an optical element optically coupled to one end of the fiber stub. The fiber stub includes a tubular ferrule, a core, and a clad covering the periphery of the core. And an optical fiber inserted into the through-hole of the ferrule, and a light absorbing film provided on at least one of the one end face of the clad, the other end face of the clad, the one end face of the ferrule, and the other end face of the ferrule. Have.

  According to the second optical module, the light absorption film attenuates the intensity of light that can become stray light at the end face of the clad or ferrule, so that stray light coupled to the signal light is reduced. Therefore, the deterioration of the transmission characteristics of the optical module is reduced.

  A third optical module according to the present invention includes a fiber stub and an optical element optically coupled to one end of the fiber stub. The fiber stub includes a tubular ferrule, a core, and a clad covering the periphery of the core. And an optical fiber inserted into the through-hole of the ferrule, and a light absorption film provided on at least one of the inner peripheral surface and the outer peripheral surface of the ferrule.

  According to the third optical module, since the light absorption film attenuates the intensity of light that can become stray light on the inner peripheral surface or outer peripheral surface of the ferrule, stray light coupled to the signal light is reduced. Therefore, the deterioration of the transmission characteristics of the optical module is reduced.

  The light absorption films of the second and third optical modules preferably attenuate the intensity of incident light to 10% or less.

  A fourth optical module according to the present invention includes a fiber stub and an optical element optically coupled to one end of the fiber stub. The fiber stub includes a tubular ferrule, a core, and a clad covering the periphery of the core. And an optical fiber inserted into the through hole of the ferrule, and the cladding diameter of the optical fiber is 500 μm or more.

  In the fourth optical module, since the cladding diameter is as large as 500 μm or more, the intensity of stray light per unit cross-sectional area in the cladding is reduced. Accordingly, stray light coupled to the signal light is reduced. Therefore, deterioration of the transmission characteristics of the optical module is reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the optical module which can reduce deterioration of a transmission characteristic is provided.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

  FIG. 1 is a longitudinal sectional view showing an optical module according to an embodiment of the present invention. An optical module 10 shown in FIG. 1 is a so-called coaxial light emitting module. The optical module 10 includes a support member 12, a plurality of lead terminals 14, a mounting member 16, a light emitting element (optical element) 18, a cap member 20, a lens 22, a first sleeve 24, a fiber stub 26, a tubular member 28, and A second sleeve 30 is provided.

  The support member 12 has a plurality of through holes extending in the axis X direction. Lead terminals 14 are inserted into the respective through holes. A sealing material 13 is filled between the inner peripheral surface 12 b defining the through hole and the lead terminal 14. For example, a low-melting glass can be used for the sealing material 13. Further, the support member 12 has a support surface 12 a that intersects the axis X. A mounting member 16 is mounted on the support surface 12a.

  The mounting member 16 has a mounting surface 16a extending in the axis X direction. A light emitting element 18 is mounted on the mounting surface 16a. The light emitting element 18 has a light emitting surface 18a for emitting signal light. The light emitting element 18 is mounted on the mounting surface 16a of the mounting member 16 so that the light emitting surface 18a intersects the axis X. The light emitting element 18 is electrically connected to the lead terminal 14 and is covered with a cap member 20.

  The cap member 20 is a substantially tubular member extending in the axis X direction. One end of the cap member 20 is fixed to the support surface 12 a of the support member 12. The cap member 20 has a lens holding portion 20a having a smaller diameter than other portions inside thereof. The lens holding unit 20 a holds the lens 22. A sealing material 13 is provided between the lens holding portion 20 a and the lens 22.

  The lens 22 has a first surface 22a on the light emitting element 18 side and a second surface 22b on the opposite side. The first surface 22 a is optically coupled to the light emitting element 18. The second surface 22b is optically coupled to one end surface 26f of the fiber stub 26. The lens 22 receives the light from the light emitting surface 18 a by the first surface 22 a and outputs the light from the second surface 22 b to the one end surface 26 f of the fiber stub 26. The fiber stub 26 will be described later.

  The first sleeve 24 is a substantially tubular member extending in the axis X direction. The first sleeve 24 optically couples the optical fiber in the fiber stub 26 and the transmission optical fiber 100 a in the transmission fiber stub 100. Therefore, the first sleeve 24 includes a first portion 24a and a second portion 24b in order along the axis X. A fiber stub 26 is held in the inner hole of the first portion 24a. The transmission fiber stub 100 is held in the inner hole of the second portion 24b. A tubular member 28 is provided on the outer periphery of the first portion 24a.

  The tubular member 28 is a tubular member extending in the axis X direction. A first portion 24 a of the first sleeve 24 is held in the inner hole of the tubular member 28. The tubular member 28 and the first sleeve 24 are covered with a second sleeve 30.

  The second sleeve 30 is a substantially tubular member extending in the axis X direction. The second sleeve 30 holds the tubular member 28. One end of the second sleeve 30 is fixed to the support surface 20 b of the cap member 20.

  Hereinafter, the fiber stubs 26A, 26B, 26C, and 26D that can be used as the fiber stub 26 will be described.

  FIG. 2 is a cross-sectional view showing a fiber stub according to the first embodiment of the present invention. The fiber stub 26A shown in FIG. 2 includes a ferrule 26a, an optical fiber 26b, and a light reflecting film 32.

  The ferrule 26a is a tubular member extending in the axis X direction. For example, zirconia can be used as the material of the ferrule 26a. An optical fiber 26b is inserted into the through hole of the ferrule 26a.

  The optical fiber 26b has a core 26c and a tubular clad 26d provided so as to cover the periphery of the core 26c. The optical fiber 26b emits light incident on one end to the transmission optical fiber 100a from the other end.

The light reflecting film 32 is provided on one end face 26p of the clad 26d, the other end face 26q of the clad 26d, one end face 26r of the ferrule 26a, and the other end face 26s of the ferrule 26a. The light reflecting film 32 preferably reflects incident light by 90% or more. Therefore, for example, a metal such as Au or Al can be used as the material of the light reflecting film 32. By depositing these metals, the light reflecting film 32 can be formed. The light reflecting film 32 may be a film in which a protective coating using, for example, MgF ₂ is applied on the Al film formed as described above. The light reflectivities of the Au film, the Al film, and the Al and MgF 2 film are about 98 percent, about 93 percent, and about 95 percent, respectively.

  The light reflecting film 32 may be provided only on at least one of the one end face 26p of the clad 26d, the other end face 26q of the clad 26d, the one end face 26r of the ferrule 26a, and the other end face 26s of the ferrule 26a. .

  In the fiber stub 26A, the light reflecting film 32 is formed on at least one of the one end face 26p of the clad 26d, the other end face 26q of the clad 26d, the one end face 26r of the ferrule 26a, and the other end face 26s of the ferrule 26a. Reflects more than a percentage. Therefore, in the optical module 10, the intensity of stray light that propagates to the transmission optical fiber 100a and couples to the signal light is reduced to 1/10 or less. Therefore, the deterioration of the transmission characteristics of the optical module 10 is reduced.

  FIG. 3 is a sectional view showing a fiber stub according to a second embodiment of the present invention. A fiber stub 26B shown in FIG. 3 is different from the fiber stub 26A in that a light absorbing film 34 is provided instead of the light reflecting film 32.

  The light absorption film 34 is provided on one end face 26p of the clad 26d, the other end face 26q of the clad 26d, one end face 26r of the ferrule 26a, and the other end face 26s of the ferrule 26a. The light absorption film 34 preferably attenuates the intensity of incident light to 10 percent or less. Therefore, as the material of the light absorption film 34, for example, a semiconductor material such as GaSb, InAs, or InSb can be used. The GaSb film, InAs film, and InSb film absorb light of 1.3 μm and 1.55 μm by the basic absorption of the semiconductor. This basic absorption is light absorption in the process where electrons in the valence band absorb energy of this light and excite it to the conduction band when light is incident on the semiconductor.

  The light absorption film 34 may be provided only on at least one of the one end face 26p of the clad 26d, the other end face 26q of the clad 26d, the one end face 26r of the ferrule 26a, and the other end face 26s of the ferrule 26a. .

  In the fiber stub 26B, the light absorption film 34 has light intensity on at least one of the one end face 26p of the clad 26d, the other end face 26q of the clad 26d, the one end face 26r of the ferrule 26a, and the other end face 26s of the ferrule 26a. Is attenuated to 10 percent or less. Therefore, in the optical module 10, the intensity of stray light that propagates to the transmission optical fiber 100a and couples to the signal light is reduced to 1/10 or less. Therefore, the deterioration of the transmission characteristics of the optical module 10 is reduced.

  FIG. 4 is a sectional view showing a fiber stub according to a third embodiment of the present invention. A fiber stub 26C shown in FIG. 4 includes a ferrule 26a, an optical fiber 26b, and a light absorption film 36.

  The light absorption film 36 is provided on the inner peripheral surface 26h and the outer peripheral surface 26i of the ferrule 26a. The light absorption film 36 preferably attenuates the intensity of incident light to 10 percent or less. Therefore, the same material as the light absorption film 34 can be used as the material of the light absorption film 36.

  The light absorption film 36 may be provided only on either the inner peripheral surface 26h or the outer peripheral surface 26i.

  In the fiber stub 26C, the light absorption film 36 attenuates the light intensity to 10% or less on at least one of the inner peripheral surface 26h and the outer peripheral surface 26i of the ferrule 26a.

  That is, the light absorption film 36 provided on the inner peripheral surface 26h of the ferrule 26a attenuates the intensity of light propagating through the clad 26d and reflected at the interface 26j between the clad 26d and the light absorption film 36 to 10% or less, The intensity of light propagating through the ferrule 26a and passing through the inner peripheral surface 26h of the ferrule 26a is attenuated to 10% or less. On the other hand, the light absorption film 36 provided on the outer peripheral surface 26i of the ferrule 26a attenuates the intensity of light propagating through the ferrule 26a and reflected by the outer peripheral surface 26i of the ferrule 26a to 10% or less.

  Therefore, in the optical module 10, the intensity of stray light that propagates to the transmission optical fiber 100a and couples to the signal light is reduced to 1/10 or less. Therefore, the deterioration of the transmission characteristics of the optical module 10 is reduced.

  FIG. 5: is sectional drawing which shows the fiber stub concerning the 4th Embodiment of this invention. A fiber stub 26D shown in FIG. 5 includes a ferrule 26m and an optical fiber 26n.

  The ferrule 26m is a tubular member extending in the axis X direction. For example, zirconia can be used as the material of the ferrule 26m. An optical fiber 26n is inserted into the through hole of the ferrule 26m.

  The optical fiber 26n has a core 26c and a tubular clad 26o provided so as to cover the periphery of the core 26c. The diameter of the clad 26o is 500 μm or more. The optical fiber 26n emits light incident on one end to the transmission optical fiber 100a from the other end.

  FIG. 6 is a diagram illustrating a calculation result of the intensity of stray light propagating through the cladding of the fiber stub. The horizontal axis represents the cladding diameter, and the vertical axis represents the relative ratio of stray light intensity per unit cross-sectional area propagating through the cladding. The relative ratio is a relative ratio when the stray light intensity is 1 when the clad diameter is 125 μm.

  As shown in FIG. 6, the light incident on the clad spreads over the entire clad. Therefore, the larger the clad diameter, the smaller the intensity of stray light per unit cross-sectional area propagating through the clad. The clad diameter of the optical fiber is generally about 125 μm. However, in the fiber stub 26D, the diameter of the clad 26o is 500 μm or more, so that the stray light intensity per unit cross-sectional area propagating through the clad 26o is 10 minutes. 1 or less.

  Here, the cladding diameter of the transmission optical fiber 100a is generally about 125 μm. Accordingly, the intensity of stray light that enters the clad of the transmission optical fiber 100a from the clad 26o and is coupled to the signal light is reduced to 1/10 or less. Therefore, the deterioration of the transmission characteristics of the optical module 10 is reduced.

  Note that since the refractive index of the transmission ferrule 100b is generally higher than the refractive index of the cladding of the transmission optical fiber 100a, most of the light incident on the transmission ferrule 100b from the cladding 26o is transmitted to the transmission ferrule 100b. Reflected at the interface with the optical fiber 100a. Therefore, the intensity of the stray light that enters the transmission ferrule 100b from the clad 26o and couples to the signal light can be ignored.

  As described above, according to the present invention, an optical module capable of reducing deterioration of transmission characteristics is provided.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the present invention can be applied not only to the light emitting module (optical element) 18 but also to a light receiving module having a light receiving element.

It is a longitudinal cross-sectional view which shows the optical module concerning embodiment of this invention. It is sectional drawing which shows the fiber stub concerning the 1st Embodiment of this invention. It is sectional drawing which shows the fiber stub concerning the 2nd Embodiment of this invention. It is sectional drawing which shows the fiber stub concerning the 3rd Embodiment of this invention. It is sectional drawing which shows the fiber stub concerning the 4th Embodiment of this invention. It is a figure which shows the calculation result of the intensity | strength of the stray light which propagates the cladding of a fiber stub.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Optical module, 12 ... Support member, 13 ... Sealing material, 14 ... Lead terminal, 16 ... Mounting member, 18 ... Light emitting element, 20 ... Cap member, 22 ... Lens, 24 ... First sleeve, 26 ... Fiber Stub, 26A to 26D ... fiber stub, 26a ... ferrule, 26b ... optical fiber, 26c ... core, 26d ... clad, 28 ... tubular member, 30 ... second sleeve, 32 ... light reflecting film, 34 ... light absorbing film, 36: Light absorbing film, 100: Transmission fiber stub, 100a: Transmission optical fiber, 100b: Transmission ferrule.

Claims (1)

With a fiber stub
An optical element optically coupled to one end of the fiber stub;
With
The fiber stub is
A tubular ferrule;
An optical fiber including a core and a cladding covering the periphery of the core, and inserted into the through-hole of the ferrule;
Have
A transmission optical fiber having a cladding diameter of 125 μm is optically coupled to the other end of the fiber stub,
A cladding diameter of the optical fiber is 500 μm or more;
Optical module.

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