JP4060130B2 - Optical module - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is an optical module applied for optical communication. The present invention relates to an optical module that separates necessary optical signals from optical signals having different wavelengths assigned to video signals, Internet signals, audio signals, and the like in, for example, wavelength division multiplexing transmission.
[0002]
[Background]
In recent years, optical communication has been performed using optical fiber networks to transmit dozens of channels of CATV video signals from the station side to the subscriber side and to exchange bidirectional signals for the Internet and data transmission. ing. In general, a signal transmitted from the station side to the subscriber side is called a downlink signal, and a signal transmitted from the subscriber side to the station side is called an uplink signal.
[0003]
In the optical communication as described above, light of different setting wavelengths is used for each signal. For example, one wavelength λ1 in the wavelength range of 1.55 to 1.56 μm is used for the video signal, and one wavelength λ2 in the wavelength range of 1.48 to 1.50 μm is added to the downlink signal from the station side to the subscriber. One signal λ3 in the wavelength range of 1.26 to 1.36 μm is used for the upstream signal from the person to the station side.
[0004]
Usually, in such a system, wavelength division multiplex transmission (wavelength division multiplex communication) using a single optical fiber as an optical transmission line is performed in order to reduce network costs such as laying and downsize components and equipment. .
[0005]
In such a communication system, since there is a single fiber as a transmission medium, the three wavelengths (λ1, λ2, λ3) to be transmitted are multiplexed and demultiplexed at the station side and the subscriber side, respectively. .
[0006]
That is, on the side of the station, the optical signals of wavelengths λ1 and λ2 are combined using a single fiber by the headend device, the transmission / reception device of the optical router device, etc., and transmitted to the subscriber side as a downstream signal. Simultaneously with the transmission, the upstream signal from the subscriber, that is, the optical signal having the wavelength λ3 is demultiplexed and received by a light receiving element such as a PIN photodiode to obtain an electric signal.
[0007]
On the subscriber side such as a home or office, the optical subscriber terminal device provided at the subscriber's home separates the optical signals of wavelengths λ1 and λ2 using a single fiber, and these wavelengths are separated. The light of λ1 and λ2 is received by a light receiving element such as a PIN photodiode to obtain an electrical signal, and an optical signal of wavelength λ3 is sent to the station side.
[0008]
For the purpose of realizing the above functions, for example, an optical module as shown in FIG. 8A has been proposed. This proposed optical module is described in Japanese Patent No. 3099167.
[0009]
As shown in FIG. 8 (a), this optical module has a first optical fiber 1 and a second optical fiber 2, and the connection end faces 11 and 12 of these optical fibers 1 and 2 are arranged on the optical axis. It is inclined with respect to it. The first and second optical fibers 1 and 2 face each other at the connection end faces through the wavelength selective reflection filter 4, and the connection end faces 11 and 12 are substantially in close contact with the wavelength selective reflection filter 4. .
[0010]
The wavelength selective reflection filter 4, for example, transmits only an optical signal having a set wavelength (for example, λ 1) out of wavelength multiplexed light (for example, light having λ 1 and λ 2) incident on the wavelength selective reflection filter 4 with respect to the incident light. The reflected light is radiated from the side surface of the first optical fiber 1 to the outside of the first optical fiber 1. The reflected light is converged by the spherical lens 10 disposed with a distance from the first optical fiber 1 and guided to the light receiving element 5.
[0011]
In this configuration, in order to guide the light reflected by the wavelength selective reflection filter 4 to the outside of the first optical fiber 1 and to the light receiving element 5, the reflected light is reflected at the boundary between the first optical fiber 1 and air. It is necessary to avoid total reflection.
[0012]
For example, when the refractive index of the cladding of the optical fiber is 1.44, the critical angle at which total reflection occurs at the boundary between the optical fiber and air (the minimum angle formed with the plane perpendicular to the boundary when total reflection occurs) is Since it is about 44 °, in order to avoid the total reflection, it is necessary to arrange the wavelength selective reflection filter 4 so that the incident angle (γ in the figure) to the side surface of the optical fiber shown in FIG. 6 is less than about 44 °. There is.
[0013]
Here, if the incident angle of the light incident on the wavelength selective reflection filter 4 is θ, γ = 90−2θ. Therefore, in order to make γ less than about 44 °, the incident light on the wavelength selective reflection filter 4 is incident. The angle θ needs to be larger than approximately 23 °. That is, as shown in FIG. 8B, when the incident angle θ to the wavelength selective reflection filter 4 is 23 ° or less, the light reflected by the wavelength selective reflection filter 4 is the side surface of the first fiber 1. Since light is totally reflected at the boundary between the air and the air, light cannot be guided to the light receiving element 5.
[0014]
[Problems to be solved by the invention]
However, the wavelength selective reflection filter 4 is formed of a dielectric multilayer film, and when the incident angle θ of light incident on the wavelength selective reflection filter 4 is small, as shown in FIG. The filter 4 can obtain a steep wavelength separation characteristic. However, if the incident angle of light incident on the wavelength selective reflection filter 4 is large, the influence of polarization increases. For example, as shown in FIG. It becomes difficult to obtain steep wavelength separation characteristics.
[0015]
In the graphs shown in FIGS. 7A and 7B, the characteristic line a indicates the reflectance when the incident angle spread width is 0, and the characteristic line b indicates the incident angle spread width of 1 °. The reflectance is shown.
[0016]
In the optical module shown in FIG. 8, the optical fiber is formed of a single mode optical fiber, and the light emitted from the single mode optical fiber to the wavelength selective reflection filter has a spread of several degrees. When the light incident angle of the reflection filter 4 is large, the wavelength separation characteristic becomes gentler than that indicated by the characteristic line b in FIG.
[0017]
Therefore, in the optical module shown in FIG. 8A, it is difficult to design a wavelength selective reflection filter when the wavelengths of light are close, and it is difficult to separate optical signals having close wavelengths with good characteristics. There was a problem.
[0018]
The present invention has been made to solve the above conventional problems, and an object of the present invention is to provide an optical module having excellent wavelength separation characteristics even if the wavelengths of light to be separated are close to each other. is there.
[0019]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has the following configuration as means for solving the problems. That is, in the first invention, the connection end face of the first light transmission path and the connection end face of the second light transmission path are arranged to face each other via the wavelength selective reflection filter. , Incident light incident on the wavelength selective reflection filter through the first light transmission path. The light incident angle is set to 8 ° to 25 °, and the wavelength selective reflection filter The setting wavelength light is configured to be reflected in an oblique direction with respect to the incident light, and the reflected light by the wavelength selective reflection filter is outside the first light transmission path. Through space A light receiving portion for receiving light is provided, and a transparent member having a refractive index close to the refractive index of the cladding portion of the first light transmission passage is provided substantially in close contact with the first light transmission passage. Is the reflected light of the set wavelength reflected by the wavelength selective reflection filter Let it propagate in the air A light guide portion that leads to the light receiving portion is formed, and an emission end face of the light guide portion is formed at an angle that intersects an optical axis of light incident on the wavelength selective reflection filter. The reflected light from the wavelength selective reflection filter incident on the output end face of the light guide unit is propagated in the air toward the light receiving unit without being totally reflected. The structure is a means to solve the problem.
[0020]
According to a second aspect of the present invention, in addition to the configuration of the first aspect, the connection end surface of the first light transmission path is inclined with respect to the optical axis of the first light transmission path. The connection end surface of the light transmission path is inclined corresponding to the inclined connection end surface of the first light transmission path, and the connection end surface of the first light transmission path and the connection end surface of the second light transmission path have wavelengths. A structure that is substantially in close contact with the selective reflection filter serves as a means for solving the problem.
[0021]
Furthermore, in the third invention, in addition to the configuration of the first or second invention, a wavelength selective reflection filter is formed in close contact with at least one connection end face of the first light transmission path and the second light transmission path. It is a means to solve the problem with the configuration.
[0022]
Furthermore, in a fourth aspect of the present invention, in addition to the first, second, or third aspect of the invention, at least one of the first light transmission path and the second light transmission path is formed of an optical fiber. As a means to solve the problem.
[0023]
Furthermore, in addition to the configuration of the fourth aspect of the present invention, the fifth invention is such that the optical fiber is formed by integrally forming a gradient index lens on the tip side of the single mode fiber, A configuration in which the front end surface forms an inclined connection end surface serves as a means for solving the problem.
[0024]
Further, the sixth invention is the above-described fourth invention, wherein the optical fiber is formed by integrally forming a graded index fiber on the tip side of the single mode fiber, and the tip surface of the graded index fiber. Is a means for solving the problem with the configuration formed by the inclined connection end face.
[0025]
Further, the seventh invention is a means for solving the problems with a configuration in which the optical fiber is inserted into a passage insertion groove formed in the substrate in addition to the configuration of the fourth or fifth invention.
[0026]
Further, according to an eighth aspect of the invention, in addition to the structure of the seventh aspect, the passage insertion groove is formed on a bottom surface side of the substrate, and at least the first light transmission passage is formed by an optical fiber so that the passage is inserted. Inserted in the groove, the substrate is formed by a transparent member having a refractive index close to the refractive index of the cladding portion of the first light transmission path, Instead of the configuration in which the transparent member is provided substantially in close contact with the first light transmission path, A transparent light guide member having a refractive index close to the refractive index of the cladding portion of the first light transmission path is provided on the upper surface of the substrate, and the reflected light reflected by the wavelength selective reflection filter is coupled to the substrate. A structure for guiding the light receiving unit through the light guide member serves as means for solving the problem.
[0027]
Furthermore, in addition to the configuration of the eighth invention, the ninth invention is a means for solving the problems with a configuration in which the light guide member is formed integrally with the substrate by processing the substrate.
[0028]
Further, the tenth aspect of the invention has the problem that, in addition to the configuration of the eighth or ninth aspect, the substrate is formed of any one transparent member of quartz glass, glass, polycarbonate, and polymethyl methacrylate. As a means to solve.
[0029]
Furthermore, in an eleventh aspect of the invention, in addition to the configuration of any one of the first to tenth aspects of the invention, wavelength selective transmission that selectively transmits setting wavelength light to at least one light passage surface of the light guide section. A configuration in which a filter is formed serves as means for solving the problem.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the present embodiment, the same reference numerals are assigned to the same names as those in the conventional example, and the duplicate description is omitted or simplified.
[0032]
FIG. 1 shows a first embodiment of an optical module according to the present invention. 1A shows a perspective view of the optical module, and FIG. 1B shows a cross-sectional view of the optical module taken along the line AA.
[0033]
As shown in these drawings, the optical module of the present embodiment includes a first optical fiber 1 as a first light transmission path and a second optical fiber 2 as a second light transmission path. is doing. The first optical fiber 1 and the second optical fiber 2 are inserted into an optical fiber insertion groove 9 as a passage insertion groove formed in a quartz substrate 7 and are disposed to face each other via a wavelength selective reflection filter 4. Yes. The optical fiber insertion groove 9 has a V-shaped cross section in a direction perpendicular to the optical axes of the optical fibers 1 and 2.
[0034]
The first optical fiber 1 has a connection end face 11 that is inclined with respect to the optical axis, and the second optical fiber 2 is a connection end face that is inclined corresponding to the inclined connection end face 11 of the first optical fiber 1. 12. The connection end faces 11 and 12 are inclined by 15 ° with respect to the plane perpendicular to the optical axis of the first and second optical fibers 1 and 2, respectively. The first and second optical fibers 1 and 2 are formed to have a diameter of about 125 μm, for example.
[0035]
The connection end face 11 of the first optical fiber 1 and the connection end face 12 of the second optical fiber 2 are substantially in close contact with the wavelength selective reflection filter 4. The wavelength selective reflection filter 4 transmits the set wavelength light (light of wavelength λ1 in this case) out of the incident light incident on the wavelength selective reflection filter 4 through the first optical fiber 1 in an oblique direction with respect to the incident light. The wavelength selective reflection filter 4 has a light incident angle (θ in FIG. 1B) of 15 °.
[0036]
In addition , The inventor has determined the light incident angle of the wavelength selective reflection filter 4 to be 15 ° based on the following examination.
[0037]
As the light incident angle of the wavelength selective reflection filter 4 is smaller, the influence of the polarization on the wavelength separation characteristic and the fluctuation characteristic of the separation characteristic with respect to the fluctuation of the incident angle are reduced, so that the wavelength selective reflection filter 4 can be easily designed. .
[0038]
For example, in order to obtain good separation characteristics even when the wavelengths to be separated are close, it is necessary to reduce the light incident angle of the wavelength selective reflection filter 4.
[0039]
On the other hand, the wavelength selective reflection filter 4 has a poor return loss characteristic as the light incident angle is smaller. That is, if the light incident angle of the wavelength selective reflection filter 4 is small, the amount of light that is reflected by the wavelength selective reflection filter 4 and returns to the first optical fiber 1 increases. Noise increases and crosstalk occurs, degrading the quality of the optical transmission line.
[0040]
As in the optical module of this embodiment, an optical module applied for wavelength division multiplex transmission usually requires a return loss of 50 dB or more. In this sense, it is necessary to determine the incident angle within a range in which the characteristics of the wavelength selective reflection filter 4 can be realized, and the light incident angle of the wavelength selective reflection filter 4 needs to be approximately 8 ° or more.
[0041]
As a result of the simulation, it was found that the wavelength selective reflection filter 4 can satisfy the above separation characteristics when the light incident angle of the wavelength selective reflection filter 4 is 25 °.
[0042]
Therefore, the light incident angle of the wavelength selective reflection filter 4 is set to 15 ° in consideration of the return loss amount and a margin for the feasibility of the wavelength selective reflection filter 4, and the first and second optical fibers 1 are associated with this value. The angle of the connection end faces 11 and 12 is also 15 °. And the filter insertion groove | channel 24 was formed in the board | substrate 7 so that this incident angle might be obtained, and the wavelength selection reflection filter 4 was inserted.
[0043]
In this embodiment, the first and second optical fibers 1 and 2 are fixed to the optical fiber insertion groove 9 of the substrate 7 by an appropriate means such as an adhesive. A light receiving unit 5 that receives light reflected by the wavelength selective reflection filter 4 is provided outside. The light receiving unit 5 includes a light receiving element such as a PIN photodiode, and is mounted on a rectangular parallelepiped ceramic block body 20.
[0044]
A transparent member 6 having a refractive index close to the refractive index of the cladding portion of the first optical fiber 1 is provided on the substrate 7 substantially in close contact with the first optical fiber 1. The cladding portion of the first optical fiber 1 is made of pure quartz, and the transparent member 6 is a prism made of quartz glass. The transparent member 6 can be formed of a transparent member having a refractive index of about 1.4 to 1.6 other than quartz glass.
[0045]
An optical fiber insertion groove 9 on the lower side of the region where the transparent member 6 is disposed has an optical index close to that of the cladding portion of the first optical fiber 1 (having a refractive index of about 1.4 to 1.6). The adhesive 18 is filled, and the transparent member 6 is fixed to the substrate 7 with the optical adhesive 18. The transparent member 6 forms the light guide 3 that guides the reflected light of the set wavelength reflected by the wavelength selective reflection filter 4 to the light receiver 5.
[0046]
The exit end face (that is, the exit end face of the transparent member 6) 8 of the light guide unit 3 is formed obliquely, and is formed at an angle that intersects the optical axis of the light incident on the wavelength selective reflection filter 4. Yes. A wavelength selective transmission filter 14 that selectively transmits the set wavelength light (here, light of wavelength λ1) is formed on the emission end face 8 that is one light passage surface of the light guide 3.
[0047]
By appropriately setting the angle of the emission end face 8 of the transparent member 6 according to the size and position of the light receiving portion 5, the light guide direction of the light emitted from the transparent member 6 is changed and the light guide path is appropriately set. be able to.
[0048]
The first and second optical fibers 1 and 2 are formed by integrally forming a graded index fiber 15 on the tip side of a single mode fiber 25. The graded index fiber 15 and the single mode fiber 25 are fusion-spliced, and the tip surface of the graded index fiber 15 forms an inclined connection end surface.
[0049]
The length of the graded index fiber 15 is set so that the graded index fiber 15 substantially forms a parallel optical system, that is, enters the wavelength selective reflection filter 4 from the first and second optical fibers 1 and 2. It is determined that the light to be substantially parallel light.
[0050]
The wavelength selective reflection filter 4 and the wavelength selective transmission filter 14 are formed by laminating about 200 layers or more of silicon oxide, titanium oxide or the like alternately on the surface of a polyimide film having a thickness of several μm to have a thickness of several tens of μm. .
[0051]
This embodiment is configured as described above. For example, as shown in FIG. 1B, when wavelength multiplexed light (for example, light having λ1 and λ2) is incident on the first optical fiber 1, The wavelength selective reflection filter 4 reflects only the optical signal of the set wavelength λ1 out of the wavelength multiplexed light obliquely toward the side of the first optical fiber 1. Then, the light having the wavelength λ 1 that has reached the side surface of the first optical fiber 1 is guided to the light receiving unit 5 through the light guide unit 3 and the wavelength selective transmission filter 14.
[0052]
The light of wavelength λ2 passes through the wavelength selective reflection filter 4 and propagates through the second optical fiber 2 toward the emission side (the right side of FIG. 1B). For example, a PIN photodiode or the like Is received by a light receiving element (not shown).
[0053]
Further, for example, when light having a wavelength λ3 different from λ1 and λ2 is incident on the second optical fiber 2 from the right side of FIG. 1B, the light passes through the wavelength selective reflection filter 4 and passes through the second optical fiber 2. It propagates toward the incident side of one optical fiber 1.
[0054]
According to the present embodiment, since the light incident angle of the wavelength selective reflection filter 4 is formed as small as 15 °, the wavelength selective reflection filter 4 is not easily affected by the polarization of the incident light, and has a steep wavelength. Separation characteristics can be obtained, and the separated set wavelength light can be reflected by the wavelength selective reflection filter 4 and efficiently guided to the light receiving unit 5.
[0055]
As described above, in the case of the conventional example shown in FIG. 8 that does not have the light guide unit 3 in the present embodiment, if the light incident angle of the wavelength selective reflection filter 4 is formed to be smaller than 23 °, FIG. As shown in FIG. 8B, the light reflected by the wavelength selective reflection filter 4 is totally reflected by the side surface of the first optical fiber 1, so that the light having the wavelength λ1 is received by the light receiving unit 5. It is not possible to perform the function as in the present embodiment example.
[0056]
Further, according to the present embodiment example, the first and second optical fibers 1 and 2 form the graded index fiber 15 on the connection end faces 11 and 12 side, so the first and second light beams Since the light emitted from the fibers 1 and 2 is substantially parallel, the wavelength selective reflection filter 4 can receive this parallel light and exhibit a better wavelength separation function.
[0057]
Furthermore, according to the present embodiment, the wavelength selective transmission filter 14 that selectively transmits the set wavelength light is formed on the emission end face 8 of the transparent member 6, and the wavelength selective reflection filter 4 is light having a wavelength other than the set wavelength. Even if the light is partially reflected, the extra light cannot pass through the wavelength selective transmission filter 14, so that only the set wavelength light can be guided to the light receiving unit 5 more reliably.
[0058]
Hereinafter, operations and effects when the optical module of this embodiment is applied to a wavelength division multiplexing transmission system will be described.
[0059]
The optical module of the present embodiment is applied to various optical communication systems. As an example, a CATV video signal of several tens of channels from a station side to a subscriber side by a single optical fiber. Is transmitted as an optical signal of one wavelength λ1 in the wavelength range of 1.55 to 1.56 μm, and a digital signal for the Internet and data transmission is transmitted as an optical signal of one wavelength λ2 in the wavelength range of 1.48 to 1.50 μm. It is applied to the wavelength division multiplexing transmission system to send.
[0060]
In addition, this system may be a system for sending a digital signal for the Internet or data transmission from the subscriber side to the station side as an optical signal having a wavelength λ3 in the wavelength range of 1.26 to 1.36 μm. it can.
[0061]
The optical module of this embodiment can be applied to, for example, a device that separates and receives video signals on the subscriber side. In this case, the first optical fiber 1 is connected to an optical fiber for optical transmission. An optical signal having a wavelength λ1 and an optical signal having a wavelength λ2 transmitted from the station side are incident on the first optical fiber 1.
[0062]
Then, the optical signal having the wavelength λ1 is substantially collimated by the action of the graded index fiber 15 of the first optical fiber 1 and enters the wavelength selective reflection filter 4, and most of the optical signal is the first light. The side surface of the fiber 1 is reflected obliquely toward the alley.
[0063]
The reflected light having the wavelength λ1 enters the transparent member 6, exits through the wavelength selective transmission filter 14 provided on the exit end face 8, enters the PIN photodiode forming the light receiving unit 5, and is converted into an electrical signal. Converted.
[0064]
On the other hand, the light having the wavelength λ 2 incident on the first optical fiber 1 is substantially converted into parallel light and incident on the wavelength selective reflection filter 4 by the lens action of the graded index fiber 15 of the first optical fiber 1. Most of it is transparent. This transmitted light is incident on the second optical fiber 2, and is further incident on the core of the single mode fiber 25 by the lens action of the graded index fiber 15 of the second optical fiber 2, and is digitally transmitted and received at the subscriber's home. It is emitted toward the device.
[0065]
Even if the wavelength λ 2 is slightly reflected by the wavelength selective reflection filter 4, the light is blocked by the wavelength selective transmission filter 14 provided on the emission end face 8 of the transparent member 6. do not do.
[0066]
As shown in FIG. 1B, when light having a wavelength λ 3 is incident from the second optical fiber 2, the light passes through the wavelength selective reflection filter 4 and passes through the first optical fiber 1 to be stationed. Sent to the side.
[0067]
As described above, this embodiment can accurately operate as a wavelength separation module in wavelength division multiplex transmission.
[0068]
FIG. 2 is a sectional view showing a second embodiment of the optical module according to the present invention. The optical module of the second embodiment is configured in substantially the same manner as the first embodiment, and redundant description with the first embodiment is omitted in the description of the second embodiment. The second embodiment is different from the first embodiment in that the shape of the transparent member 6 is a rectangular parallelepiped.
[0069]
In the second embodiment, since the transparent member 6 has a rectangular parallelepiped shape, the emission end face 8 is a plane substantially orthogonal to the optical axis of the light incident on the wavelength selective reflection filter 4.
[0070]
The second embodiment is configured as described above, and the second embodiment can also achieve the same effect by the same operation as the first embodiment.
[0071]
FIG. 3 is a sectional view showing a third embodiment of the optical module according to the present invention. The third embodiment is configured in substantially the same manner as the first embodiment, and a duplicate description with the first embodiment is omitted.
[0072]
The third embodiment is different from the first embodiment in that the first and second optical fibers 1 and 2 are each formed by a single mode fiber 25.
[0073]
When the first and second optical fibers 1 and 2 are formed by the single mode fiber 25, the light incident on the wavelength selective reflection filter 4 becomes divergent light. Therefore, the wavelength separation characteristics are inferior to those of the first and second embodiments in which the first and second optical fibers 1 and 2 are formed by providing the graded index fiber 15 on the tip side. .
[0074]
However, also in the third embodiment, the light incident angle of the wavelength selective reflection filter 4 can be made smaller than that of the conventional example, so that the wavelength separation characteristic is better than that of the conventional example, and the wavelength of light to be reflected and separated is By appropriately setting the wavelength of light to be transmitted, a good wavelength separation function can be achieved.
[0075]
The optical module of the third embodiment is, for example, at a subscriber's house, a video signal having a wavelength (λ1) in the range of 1.48 to 1.50 μm is reflected by the wavelength selective reflection filter 4 and separated. This is applied to a case where a digital signal having a wavelength (λ2) in the range of 26 to 1.36 μm is received through the wavelength selective reflection filter 4.
[0076]
FIG. 4 shows a fourth embodiment of an optical module according to the present invention by a perspective view shown in (a) and a cross-sectional view along the optical axis of an optical fiber shown in (b). In the description of the fourth embodiment, the same reference numerals are assigned to the same name portions as those in the first embodiment, and the duplicate description is omitted.
[0077]
Similar to the first embodiment, the fourth embodiment has first and second optical fibers 1 and 2 and a substrate 7 into which these optical fibers 1 and 2 are inserted. The insertion groove 9 is formed on the bottom surface side of the substrate 7, and the first and second optical fibers 1 and 2 are inserted into the optical fiber insertion groove 9 and fixed.
[0078]
The substrate 7 is formed of quartz glass as a transparent member having a refractive index close to the refractive index of the cladding portion of the first optical fiber 1, and a light guide member of the transparent member 6 is provided on the upper surface of the substrate 1. In the fourth embodiment, the reflected light reflected by the wavelength selective reflection filter 4 is guided to the light receiving unit 5 through the substrate 7 and the transparent member 6. That is, in the fourth embodiment, the light guide unit 3 includes the light passage region of the substrate 7 and the transparent member 6.
[0079]
The fourth embodiment is configured as described above, and the fourth embodiment can also achieve the same effect by the same operation as that of the first embodiment.
[0080]
In the fourth embodiment, since the optical fiber insertion groove 9 is formed on the bottom surface side of the substrate 7 and the transparent member 6 is provided on the upper surface of the substrate 7, stability when the transparent member 6 is fixed to the substrate 7 is achieved. The optical module can be more easily assembled.
[0081]
In the fourth embodiment, the material of the substrate 7 is quartz glass, but the substrate 7 is substantially transparent in the transmitted light wavelength region and is close to the refractive index of the clad of the optical fiber (the refractive index is approximately It may be formed of a transparent member (from 1.4 to 1.6), and glass or the like can be used. In addition, when the optical module is used for household appliances that are used under mild environmental conditions, the substrate 7 may be formed of polycarbonate, polymethyl methacrylate, or the like.
[0082]
FIG. 5 shows a fifth embodiment of an optical module according to the present invention by a perspective view shown in (a) and a cross-sectional view along the optical axis of an optical fiber shown in (b). In the description of the fifth embodiment, the same reference numerals are given to the same name portions as those in the above embodiments, and the duplicate description will be omitted.
[0083]
The fifth embodiment is configured in substantially the same manner as the fourth embodiment, and the fifth embodiment is different from the fourth embodiment in that the light guide member of the transparent member 6 is different. The substrate 7 is processed and formed integrally with the substrate 7. That is, in the fifth embodiment, the portion 16 projecting to the upper surface side of the substrate 7 is a light guide member.
[0084]
The fifth embodiment is configured as described above, and the fifth embodiment can achieve the same effects as those of the fourth embodiment. In the fifth embodiment, the light guide member 16 of the transparent member 6 is formed integrally with the substrate 7 by processing the substrate 7, and can be integrally formed with a resin such as polycarbonate. It is small in number, easy to assemble, mass-productive, and economical. Therefore, the fifth embodiment is suitable as an optical module applied for home use, for example.
[0085]
In addition, this invention is not limited to the said embodiment example, Various aspects can be taken. For example, in the above embodiment, the wavelength selective reflection filter 4 is sandwiched between the first optical fiber 1 and the second optical fiber and bonded with an optical adhesive, but the wavelength selective reflection filter 4 is The first optical fiber 1 and the second optical fiber 2 may be formed in close contact with the connection end face.
[0086]
In this case, the first and second optical fibers 1 and 2 may be fixed to the grooves by means such as adhesive or soldering at appropriate portions, or the first optical fiber 1 and the second light. The connection end faces 11 and 12 of the fibers may be bonded together with an optical adhesive or the like, and the whole may be fixed in the groove by means such as an adhesive or soldering.
[0087]
In the first, second, fourth, and fifth embodiments, the first and second optical fibers 1 and 2 are each formed by providing the graded index fiber 15 on the tip side of the single mode fiber 25. In the third embodiment, the optical fibers 1 and 2 are formed by the single mode fiber 25.
[0088]
However, the types of the first and second optical fibers 1 and 2 are not particularly limited, and are set as appropriate. The first and second optical fibers 1 and 2 are the tips of the single mode fiber 25. A refractive index distribution type lens may be integrally formed on the side. In this case, the gradient index lens is formed so that the front end surface thereof is an inclined connection end surface.
[0089]
Furthermore, in the above first to third embodiment examples, the substrate 7 may be formed of stainless steel, titanium, glass, silicon, or the like. It may be formed.
[0090]
Further, in each of the above-described embodiments, the optical fiber insertion groove 9 is a V-groove having a V-shaped cross section, but the optical fiber insertion groove 9 may be a groove having a U-shaped cross section.
[0091]
Further, in each of the above embodiments, the wavelength selective reflection filter 4 and the wavelength selective transmission filter 14 are formed by alternately laminating silicon oxide, titanium oxide, etc. to a thickness of several tens of μm on the surface of a polyimide film having a thickness of several μm. Although the one in which the dielectric multilayer film is formed is used, the wavelength selective reflection filter 4 and the wavelength selective transmission filter 14 may be those in which the dielectric multilayer film is formed on the surface of a thin glass plate.
[0092]
Moreover, in each said embodiment, although the wavelength selection transmission filter 14 was provided in the output end surface of the light guide part 3, the wavelength selection transmission filter 14 should just be provided in the at least 1 light passage surface of the light guide part 3, For example, it may be provided on the incident end face of the transparent member 6. In this case, an antireflection film may be formed on the emission end face of the transparent member 6.
[0093]
Further, when the leakage amount requirement for the reflected light by the wavelength selective reflection filter 4 is not strict (that is, for example, in the application example of each embodiment described above, a small amount of light having a wavelength other than the wavelength λ1 is incident on the light receiving unit 5 side If there is no problem, the wavelength selective transmission filter 14 can be omitted.
[0094]
Furthermore, in each of the embodiments described above, the exit end face 8 of the light guide unit 3 is a flat surface. However, for example, the exit end face 8 may be a convex spherical surface. In this case, the emitted light from the exit end face 8 It is also possible to have a function of converging and guiding the light to the light receiving unit 5.
[0095]
Further, in each of the above embodiments, the connection end surfaces 11 and 12 of the first and second optical fibers 1 and 2 are connection end surfaces inclined with respect to the optical axis. For example, the first and second optical fibers 1 , 2 connection end faces 11, 12 are connection end faces substantially orthogonal to the optical axis, and the wavelength selective reflection filter 4 and the first and second optical fibers 1, 2 are arranged obliquely with respect to the optical axis. An optical adhesive may be provided between the end surfaces 11 and 12.
[0096]
Furthermore, the optical module of the present invention is a light receiving element such as a PIN photodiode for photoelectrically converting light of wavelength λ2 on one end side (right side in each figure) of the second optical fiber 2 in each of the above embodiments. Or a light emitting element that emits light of wavelength λ3 may be integrated.
[0097]
【The invention's effect】
According to the present invention, a transparent member having a refractive index close to the refractive index of the cladding portion of the first light transmission path is provided substantially in close contact with the first light transmission path. Since the light guide unit guides the reflected light of the reflection filter to the light receiving unit, even if the light incident angle of the wavelength selective reflection filter is reduced, the reflected light is prevented from being totally reflected by the first light transmission path and reflected. Light can be accurately guided to the light receiving unit.
[0098]
Therefore, the optical module of the present invention is not easily affected by the polarization of light incident on the wavelength selective reflection filter, and can obtain a steep wavelength separation characteristic. The wavelength selective reflection filter reflects and separates the set wavelength light. It can be efficiently guided to the light receiving unit.
[0099]
Further, in the present invention, the connection end surfaces of the first and second light paths are used as connection end surfaces inclined with respect to the optical axis, and the connection end surfaces of the first and second light transmission paths are substantially used as the wavelength selective reflection filter. According to the configuration in close contact with each other, the optical connection between the first and second light transmission paths and the wavelength selective reflection filter can be made low loss, and an optical module with small loss can be realized.
[0100]
Furthermore, in the present invention, according to the configuration in which the wavelength selective reflection filter is formed in close contact with at least one connection end surface of the first light transmission path and the second light transmission path, the wavelength selective reflection filter is formed in close contact. The connection loss between the light transmission path and the wavelength selective reflection filter can be made extremely small, and the assembly workability of the optical module can be reduced. The It can be made even better.
[0101]
Furthermore, in the present invention, according to the configuration in which at least one of the first light transmission path and the second light transmission path is formed of an optical fiber, an optical module can be easily formed using the optical fiber, for example, When applied as an optical separation module for wavelength division multiplex transmission, the optical fiber of the optical module can be connected to the optical fiber for optical transmission, for example, with low connection loss.
[0102]
Furthermore, in the present invention, the optical fiber has a configuration in which a gradient index lens is integrally formed on the distal end side of the single mode fiber, or a graded index fiber is integrally formed on the distal end side of the single mode fiber. According to this, the light emitted from the single mode fiber can be converted into parallel light by a gradient index lens or a graded index fiber and can be incident on the wavelength selective reflection filter.
[0103]
Therefore, the optical module with this configuration can make the parallel light incident on the wavelength selective reflection filter and exhibit a more excellent wavelength separation function.
[0104]
Furthermore, in the present invention, according to the configuration in which the optical fiber is inserted into the passage insertion groove formed on the substrate, the optical fiber can be positioned well, the assembly workability of the optical module can be improved, and the yield can be improved. Can be improved.
[0105]
Further, in the present invention, the channel insertion groove is formed on the bottom surface side of the substrate, and the substrate is formed by a transparent member having a refractive index close to the refractive index of the cladding portion of the first light transmission path, and the wavelength selective reflection filter According to the configuration in which the reflected light reflected by the light is guided to the light receiving part through the substrate and the light guide member provided on the substrate, the light guide member can be fixed on the substrate in a very stable state, and the assembly workability is further improved. Can be good.
[0106]
Furthermore, according to the present invention, the light guide member is formed by processing a substrate and integrally forming the substrate, so that the number of components is small, the assembly is easy, the mass productivity is good, and the economy is excellent. Modules can be realized.
[0107]
Furthermore, in the present invention, the passage insertion groove is formed on the bottom surface side of the substrate, and the substrate is formed of any one transparent member of quartz glass, glass, polycarbonate, or polymethyl methacrylate. The substrate can be easily formed and the above effects can be achieved.
[0108]
Furthermore, in the present invention, according to the configuration in which the wavelength selective transmission filter that selectively transmits the set wavelength light is formed on at least one light passage surface of the light guide unit, even if the wavelength selective reflection filter is used, an unnecessary wavelength is obtained. Even if some of the light is reflected, since this light does not pass through the wavelength selective transmission filter, the wavelength separation characteristics of the optical module can be further improved.
[0109]
Furthermore, in the present invention, according to the configuration in which the light incident angle of the wavelength selective reflection filter is set to 8 ° or more and 25 ° or less, both the return loss characteristic and the wavelength separation characteristic of the wavelength selective reflection filter can be improved. Therefore, an optical module having a small return loss and an excellent wavelength separation function can be realized.
[Brief description of the drawings]
FIG. 1 is a main part configuration diagram showing a first embodiment of an optical module according to the present invention.
FIG. 2 is a main part configuration diagram showing a second embodiment of an optical module according to the present invention.
FIG. 3 is a main part configuration diagram showing a third embodiment of an optical module according to the present invention.
FIG. 4 is a main part configuration diagram showing a fourth embodiment of an optical module according to the present invention.
FIG. 5 is a main part configuration diagram showing a fifth embodiment of an optical module according to the present invention;
FIG. 6 is an explanatory diagram for explaining the relationship between the light incident angle θ to the wavelength selective reflection filter and the incident angle γ incident on the side surface of the optical fiber.
FIG. 7 is a graph showing the reflectance (a) when the light incident angle is small and the reflectance (b) when the light incident angle is large in the wavelength selective reflection filter, corresponding to the divergence angle of the incident light. .
FIG. 8 is an explanatory diagram showing a proposed example (a) of a conventional optical module and an operation example (b) when the light incident angle of the wavelength selective reflection filter is reduced in this example.
[Explanation of symbols]
1 First optical fiber
2 Second optical fiber
3 Light guide
4 Wavelength selective reflection filter
5 Light receiver
6 Transparent members
7 Substrate
8 Output end face
9 Optical fiber insertion groove
14 Wavelength selective transmission filter

Claims (11)

Connection end face and connection end face of the second light transmission path of the first light transmission path is arranged to face through the wavelength selective reflection filter, it enters the wavelength-selective reflective filter through the first light transmitting path The incident light angle of the incident light is set to 8 ° to 25 °, and the wavelength selective reflection filter is configured to reflect the set wavelength light of the incident light in an oblique direction with respect to the incident light. A light receiving portion that receives light reflected by the wavelength selective reflection filter through a space is provided outside the first light transmission path, and is substantially in close contact with the first light transmission path. A transparent member having a refractive index close to the refractive index of the cladding portion of the light transmission path is provided, and the transparent member guides the reflected light of the set wavelength reflected by the wavelength selective reflection filter in the air and guides it to the light receiving portion. The light section is formed and emitted from the light guide section. The end face is formed at an angle intersecting the optical axis of the light incident on the wavelength selective reflection filter, so that the reflected light from the wavelength selective reflection filter incident on the output end face of the light guide is totally reflected. An optical module characterized in that the optical module propagates in the air toward the light receiving unit without any problem .   The connection end surface of the first light transmission path is inclined with respect to the optical axis of the first light transmission path, and the connection end surface of the second light transmission path is at the inclined connection end surface of the first light transmission path. 2. The first light transmitting passage connecting end face and the second light transmitting passage connecting end face are substantially in close contact with the wavelength selective reflection filter. The optical module as described.   3. The optical module according to claim 1, wherein a wavelength selective reflection filter is formed in close contact with at least one connection end face of the first light transmission path and the second light transmission path.   The optical module according to claim 1, wherein at least one of the first light transmission path and the second light transmission path is formed by an optical fiber.   5. The optical fiber is formed by integrally forming a gradient index lens on the tip side of a single mode fiber, and the tip surface of the gradient index lens forms an inclined connection end surface. The optical module as described.   The optical fiber is formed by integrally forming a graded index fiber on the tip side of a single mode fiber, and the tip surface of the graded index fiber is formed as an inclined connection end surface. Optical module.   7. The optical module according to claim 4, wherein the optical fiber is inserted into a passage insertion groove formed in the substrate. The passage insertion groove is formed on the bottom surface side of the substrate, at least the first light transmission passage is formed of an optical fiber and is inserted into the passage insertion groove, and the substrate is a cladding portion of the first light transmission passage. Instead of the configuration in which the transparent member is provided with a refractive index close to the refractive index of the first optical transmission path and the transparent member is provided substantially in close contact with the first light transmission path , the first light transmission is provided on the upper surface of the substrate. A transparent light guide member having a refractive index close to the refractive index of the cladding portion of the passage is provided, and the reflected light reflected by the wavelength selective reflection filter is guided to the light receiving portion through the substrate and the light guide member. The optical module according to claim 7, characterized in that:   9. The optical module according to claim 8, wherein the light guide member is formed integrally with the substrate by processing the substrate.   The optical module according to claim 8 or 9, wherein the substrate is formed of any one transparent member of quartz glass, glass, polycarbonate, and polymethyl methacrylate.   11. The wavelength selective transmission filter that selectively transmits light having a set wavelength is formed on at least one light passage surface of the light guide unit. 11. Optical module.

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