JP7037171B2 - Optical isolator module - Google Patents

Description

The present invention relates to an optical isolator module.

High-speed optical transceivers that handle large bit rates are attracting attention as applications for data centers. When a higher bit rate is required, many wavelengths are used, so a higher density wavelength interval grid is required. Therefore, the use of a planar lightwave circuit (PLC) used in the information and communication industry is being considered.

Therefore, Patent Document 1 has been filed as an optical isolator module that can be optically connected to a PLC without increasing the number of alignment points and can realize high optical isolation.

The optical isolator module (optical fiber block) according to FIGS. 20 to 22 in Patent Document 1 has a V-groove width W1 for fixing a graded index (GI) optical fiber (hereinafter, GIF) on the input side. , The width W2 of the V groove that fixes the GIF on the output side is changed. By changing the widths W1 and W2 of each V-groove, the opposing GIFs are arranged so as to be offset in the height direction.

JP-A-2016-206628

However, in the optical isolator modules according to FIGS. 20 to 22 in Patent Document 1, the optical axes are adjusted in the height direction between the GIFs facing each other by changing the widths of the two V-grooves. Therefore, it was necessary to position the GIF between the optical axes by controlling the width of the V-groove larger than the diameter of the GIF. Therefore, excessive precision is required in the processing process for forming each V-groove into a desired width, which has led to an increase in the manufacturing cost of the optical isolator module.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical isolator module capable of reducing manufacturing costs.

The above problems are solved by the following invention. That is, the optical isolator module of the present invention is an optical isolator in which a groove is formed on the surface of a substrate made of borosilicate glass or quartz, and the groove is composed of at least two or more polarizing elements and one or more Faraday rotors. The elements are arranged at an angle, at least one or more substituents are arranged face-to-face with respect to the two optical surfaces of the Faraday rotor, and two V-grooves are formed via the grooves facing the ligand. The first graded index optical fiber and the second graded index optical fiber, which are coaxial in the longitudinal direction of the two V-grooves and have the same depth and different outer diameters, are placed in the two V-grooves, respectively. Arranged, a height difference is formed in the depth direction of the V-groove between the core axis of the first graded index optical fiber and the core axis of the second graded index optical fiber, and each graded index optical fiber is formed. Each light inlet / output end face is formed perpendicular to the optical axis, and light is propagated to a first graded index optical fiber having a relatively thick outer diameter, converted into parallel light, and then emitted. Parallel light is incident on the element to change the optical path, then parallel light is incident on the second graded index optical fiber with a relatively narrow outer diameter and further propagated to the single-mode optical fiber, and each graded. The length of the indexed optical fiber is set to an odd multiple of one-fourth or one-fourth of the meandering period of the light propagating through the graded index optical fiber, and the clad of the second graded index optical fiber and the single. The cladding of the mode type optical fiber is made of the same material, the diameter of the parallel light propagating through the optical isolator element is 85 μm or more and 100 μm or less, and the inclination angle of the optical isolator element with respect to each optical input / output end face of each graded index optical fiber. Is 1.5 degrees or more and 3.5 degrees or less, the outer diameter of the first graded index optical fiber is 125 μm, the outer diameter of the second graded index optical fiber is 118.5 μm, and the height difference is 3.8 μm or more and 8.9. The optical isolator element is μm or less, the optical isolator element is composed of two deflectors and one Faraday rotor, and the thickness of the two spectrometers is both 0.2 mm and the thickness of the Faraday rotor is 0.42 mm. It is characterized by.

According to the optical isolator module of the present invention, the manufacturing cost can be reduced.

It is a front view schematically showing the optical isolator module which concerns on 1st Embodiment and Example of this invention. (a) It is a top view of the optical isolator module of FIG. (b) It is a left side view of the optical isolator module of FIG. (c) It is a right side view of the optical isolator module of FIG. It is a perspective view of the optical isolator module of FIG. (a) It is a top view of the substrate which constitutes the optical isolator module of FIG. (b) It is a front view of the substrate of FIG. 4 (a). (c) It is a left side view of the substrate of FIG. 4 (a). It is a perspective view which shows the state which arranges the optical isolator element in the groove of the substrate of FIG. It is a perspective view which shows the state which the graded index optical fiber and the single mode type optical fiber are arranged in the V groove of the substrate of FIG. 4 in which an optical isolator element is arranged. FIG. 3 is a side view showing the outer diameters of the first graded index optical fiber and the single-mode optical fiber, and the second graded index optical fiber and the single-mode optical fiber constituting the optical isolator module of FIG. 1. be. It is explanatory drawing which shows the propagation optical path of the light between two graded index optical fibers and the optical isolator element in the optical isolator module of FIG. It is explanatory drawing which shows the propagation state of the light between two graded index optical fibers and the optical isolator element in the optical isolator module of FIG. It is a front view schematically showing the junction state of the optical isolator module and PLC which concerns on 2nd Embodiment of this invention.

The first feature of this embodiment is that a groove is formed on the surface of a substrate made of borosilicate glass or quartz, and the groove is composed of at least two or more polarizing elements and one or more Faraday rotors. The optical isolators are arranged at an angle, at least one or more substituents are arranged face-to-face with respect to the two optical surfaces of the Faraday rotor, and two V-grooves facing the ligands are interposed through the grooves. The first graded index optical fiber and the second graded index optical fiber having the same depth as the coaxial and the same depth in the longitudinal direction of the two V-grooves have different outer diameters in the two V-grooves. A height difference is formed in the depth direction of the V-groove between the core axis of the first graded index optical fiber and the core axis of the second graded index optical fiber. Each optical input / output end face of the optical fiber is formed perpendicular to the optical axis, and light is propagated to the first graded index optical fiber having a relatively thick outer diameter, converted into parallel light, and then emitted. Parallel light is incident on the optical isolator element to change the optical path, and then parallel light is incident on the second graded index optical fiber having a relatively narrow outer diameter and further propagated to the single-mode optical fiber. The length of the graded index optical fiber is set to an odd multiple of one-fourth or one-fourth of the meandering period of the light propagating through the graded index optical fiber, and the clad of the second graded index optical fiber. , The clad of the single-mode optical fiber is made of the same material, the diameter of the parallel light propagating through the optical isolator element is 85 μm or more and 100 μm or less, and the optical isolator element for each optical input / output end face of each graded index optical fiber. The inclination angle is 1.5 degrees or more and 3.5 degrees or less, the outer diameter of the first graded index optical fiber is 125 μm, the outer diameter of the second graded index optical fiber is 118.5 μm, and the height difference is 3.8 μm. The light isolator element is 8.9 μm or less, and the optical isolator element is composed of two extruders and one Faraday rotator. It was a certain optical isolator module.

According to this configuration, the two V-grooves are set to the same height, and the substrate material is made of borosilicate glass or quartz, so that the jig blade in cutting is only at a certain height. It is possible to complete the formation of two V-grooves by setting and feeding the jig once. Therefore, the manufacturing cost of the optical isolator module can be reduced.

Furthermore, by forming two V-grooves on one flat substrate, the height of the two V-grooves (that is, the depth of the bottom from the surface of the substrate) can be obtained only by one measurement by taking advantage of the outer shape of the substrate. ) Can be derived. Therefore, in this respect as well, the manufacturing cost of the optical isolator module can be reduced.

Further, by forming each light input / output end surface of the first or second graded index optical fiber perpendicular to the optical axis, refraction of light at each light input / output end surface is prevented. Therefore, it is possible to eliminate the optical axis adjustment step between the first and second graded index optical fibers due to refraction. Further, positioning in the circumferential direction between the first and second graded index optical fibers becomes unnecessary, and the number of manufacturing steps is reduced. Therefore, the manufacturing cost of the optical isolator module can be further reduced.

Further, by forming the clad of the second graded index optical fiber and the clad of the single mode type optical fiber with the same material, the manufacturing cost of the optical isolator module can be further reduced.

Further, since the two V-grooves are set to the same depth, the optical axis adjustment due to the height difference between the core axes between the graded index optical fibers is smaller than the V-groove width. It is possible to adjust the outer diameter of the graded index optical fiber. Manufacture of an optical isolator module because an extremely precise adjustment process called optical axis adjustment between core axes can be performed quickly by reducing the diameter of the second graded index optical fiber, which is a smaller diameter optical component. It is possible to reduce time and manufacturing cost.

In the present invention, the "optical surface" refers to the boundary surface between the polarizing element and the Faraday rotator, and is also referred to as an optical surface.

Further , according to this configuration, it is possible to surely reduce the insertion loss (IL). Further, by configuring the optical isolator element with two polarizing elements and one Faraday rotator, it is possible to reduce the number of optical elements constituting the optical isolator element. Therefore, in this respect as well, the manufacturing cost of the optical isolator module can be further reduced.

Further , according to this configuration, even in an optical isolator module in which the outer diameters of the first and second graded index optical fibers and the diameters of parallel light are set, the distance between the two graded index optical fibers is increased. A reliable optical coupling can be realized.

The second feature of this embodiment is that the first graded index optical fiber is directly and optically connected to the light emitting source of the propagating light, and the first graded index optical fiber faces the light emitting source. It is an optical isolator module in which the light incident end face of the optical fiber and the light emitting source are joined by an adhesive matching the refractive index of the core of the first graded index optical fiber F.

According to this configuration, the manufacturing cost of the optical isolator module can be reduced by directly and optically connecting the first graded index optical fiber and the light emitting source. Further, since it can be directly optically connected to the light emitting source, it is possible to realize an optical isolator module in which the adjustment points of the optical axis with the light emitting source and the increase in the optical axis adjusting process are prevented.

Hereinafter, the first embodiment of the present invention will be described with reference to FIGS. 1 to 9. It is assumed that the X-axis, Y-axis, and Z-axis of each figure correspond to each other in all the figures. The optical isolator module 1 according to the first embodiment includes a flat plate-shaped substrate 2 made of borosilicate glass or quartz. As shown in FIG. 4, a groove 2a having a concave cross section is formed on the surface of the substrate 2 in parallel with the Y-axis direction, and two V-grooves 2b and 2c are formed in the X-axis direction via the groove 2a. Is formed in the longitudinal direction. The longitudinal directions of the two V-grooves 2b and 2c are coaxial. Further, the depths of the two V-grooves 2b and 2c (that is, the positions of the bottoms 2b1 and 2c1 of the respective V-grooves 2b and 2c in the -Z axis direction) are set to be the same.

The V-groove in the present invention is a groove having a V-shaped cross section when viewed from the X-axis direction, as shown in FIGS. 2 (b), 2 (c), and 4 (c). Is. Further, the opening angle of the bottom portions 2b1 and 2c1 of the V-groove 2b or 2c is set to 60 degrees in the embodiment of the present invention.

As shown in FIGS. 1, 2, and 5, the optical isolator element 3 is obliquely arranged in the groove 2a with an inclination angle θ. The optical isolator element 3 is composed of at least two or more polarizing elements and one or more Faraday rotators. In the optical isolator module 1, the optical isolator element 3 is composed of two splitters 3a and 3b and one Faraday rotator 3c.

The optical isolator element 3 of the optical isolator module 1 is a polarization-dependent optical element, and is arranged face-to-face so that the relative angles of the two polarizing elements 3a and 3b in the polarization transmission direction are about 45 degrees. Between these splitters 3a and 3b, one Faraday rotator 3c having a thickness such that the Faraday rotator angle is about 45 degrees at a predetermined wavelength in a saturated magnetic field is arranged. Therefore, at least one or more polarizing elements 3a or 3b are arranged so as to face each other with respect to the two optical surfaces of the Faraday rotator 3c. The optical isolator element 3 has a function of passing light in the forward direction (+ X-axis direction) and blocking light in the reverse direction (-X-axis direction). In the present invention, the "optical surface" refers to the boundary surface between the stators 3a and 3b and the Faraday rotator 3c, and is also referred to as an optical surface.

The polarizing elements 3a and 3b and the Faraday rotator 3c in the optical isolator element 3 are each formed into a square shape, but for example, they are formed into a rectangle whose Y-axis direction is a long side with respect to the X-axis direction. May be.

A ferromagnetic material is suitable for the Faraday rotator 3c, and a rare earth iron garnet-based single crystal can be used. In this case, as shown in FIGS. 1 to 3, it is possible to eliminate the magnet by using a self-saturating rare earth iron garnet-based single crystal that exhibits a Faraday rotation angle of about 45 degrees without a magnet. Will be. Therefore, it is preferable that the number of parts can be reduced.

Alternatively, a magnet may be arranged in the vicinity of the optical isolator element 3 to apply a saturated magnetic field to the Faraday rotator.

The optical isolator element 3 prepares a laminated substrate body by using two polarizing plates to be polarizing plates on both sides of a magneto-optical crystal plate to be a Faraday rotator and using an optical adhesive or the like while adjusting the deflection directions of each other. do. Next, the laminated body may be cut, and a plurality of optical isolator elements 3 may be cut out and manufactured.

In the state where the optical isolator element 3 is arranged in the groove 2a, the V grooves 2b and 2c are formed so as to face the polarizing elements 3a or 3b, respectively. Further, in the two V-grooves 2b and 2c, the first graded index optical fiber 4a (hereinafter, referred to as GIF4a or optical fiber 4a as required) and the second graded index optical fiber 5a (hereinafter, required), respectively. GIF5a or optical fiber 5a) is arranged according to the above. GIF4a or 5a is composed of a core and a clad whose refractive index distribution is adjusted so that the refractive index at the center is high and the refractive index is gradually lowered toward the outside.

The outer diameters of GIF4a and 5a are different from each other as shown in FIG. 7, and the outer diameter d4a of GIF4a is formed to be larger than the outer diameter d5a of GIF5a. Therefore, when these GIF4a and 5a are arranged in a two-point contact on the two slopes of each V-groove 2b or 2c, the relatively thin core axis ca2 on the GIF5a side becomes the core axis on the GIF4a side, as shown in FIG. It is arranged in the -Z axis direction as compared with the axial position of ca1, and a height difference H is formed between the core axes ca1 and ca2 in the depth direction of the V grooves 2b and 2c.

GIF5a is immersed in an etching solution and its diameter is reduced by etching. As an example, a mixed aqueous solution of ammonium fluoride (NH ₄ F), hydrofluoric acid (HF), and pure water (H ₂ O) or a mixture of hydrogen peroxide solution (H ₂ O ₂ ) is used as the etching solution. It's fine. While keeping the core diameter as it is with the core as a non-etched part, only the clad diameter is etched to reduce the diameter of GIF5a. The outer diameter d4a of GIF4a is set to 125 μm, and the outer diameter d5a of one GIF5a is reduced to 118.5 μm by the etching.

Further, each light input / output end face of each GIF 4a and 5a is formed perpendicular to the optical axis oa as shown in FIG. Further, the optical inlet / output end faces of the GIFs 4a and 5a and the optical isolator element 3 are sealed with an optical adhesive (not shown). As the optical adhesive, an adhesive having a refractive index that matches the refractive index of the core portion of each GIF4a and 5a is used, and for example, a resin optical adhesive that is cured by ultraviolet light (wavelength 200 nm to 400 nm) is preferable. Is.

From FIG. 7, the length L4a or L5a in the longitudinal direction in the length X-axis direction (that is, the optical axis oa direction) of each GIF4a or 5a is a quarter of the meandering period of the light propagating in each GIF4a or 5a. It is set to an odd multiple of 1 or 1/4.

Further, a single mode (SM: Single Mode) type optical fiber 4b or 5b is bonded to the end of each GIF 4a or 5a that does not face the polarizing elements 3a and 3b (hereinafter, simply, if necessary, optical fiber). Notated as fiber 4b or optical fiber 5b). The ends of the optical fibers 4a and 4b or the ends of the optical fibers 5a and 5b are joined by an adhesive or fusion. As the adhesive, an adhesive having a refractive index that matches the refractive index of the core of each optical fiber may be used. For the optical fiber 4b or 5b, for example, a quartz-based optical fiber can be used. The outer diameter of each optical fiber 4b or 5b is set to 125 μm or 118.5 μm, which is the same outer diameter as each GIF 4a or 5a to be joined. The outer diameter of the optical fiber 5b can also be reduced by etching in the same manner as GIF5a.

Further, regardless of the joining method such as adhesive or fusion, after joining each optical fiber, GIF4a or 5a is cut at a desired length of L4a or L5a.

Further, the clad of GIF5a and the clad of the optical fiber 5b are made of the same material, and the clad of GIF4a and the clad of the optical fiber 4b are also made of the same material.

As shown in FIG. 6, optical fibers 4b and GIF4a or optical fibers 5b and GIF5a bonded to each other are arranged in each V-groove 2b or 2c, and then an adhesive is applied to each optical fiber in each V-groove 2b. Or it sticks to 2c. Since an ultraviolet light-curing adhesive is used as the adhesive, it is necessary to use a light-transmitting material such as borosilicate glass or quartz as the material constituting the substrate 2.

Further, a light emitting source (not shown) is arranged at the laser beam incident side end portion (left side in FIG. 1) of the optical fiber 4b. Light (laser light) is incident on the optical fiber 4b from the light emitting source. The light emitting source is a semiconductor laser element called a laser diode (LD).

The light from the light source is propagated through the optical fiber 4b, and then the light is propagated to the relatively thick outer diameter GIF4a. As described above, GIF4a is set to an odd multiple of one-fourth or one-fourth of the meandering period of the light propagating by the length L4a. Therefore, the light incident from the optical fiber 4b is converted into parallel light by GIF4a and emitted from the light emitting end face 4a1.

The parallel light emitted from the light emitting end surface 4a1 of the GIF4a is then incident on the optical isolator element 3 as shown in FIG. As shown in FIG. 8, the optical path of the parallel light incident on the optical isolator element 3 is changed by refraction on the optical surface of the polarizing elements 3a arranged to face each other. Due to this refraction, parallel light is incident on the light incident end surface 5a1 of the GIF5a having a relatively small outer diameter, which is deviated by the height difference H in the -Y direction. As mentioned above, since the length L5a of GIF5a is set to an odd multiple of one-fourth or one-fourth of the meandering period of the propagating light, the parallel light converges to the core of GIF5a by propagating GIF5a. Is emitted. The focused light is then propagated through the optical fiber 5b.

The V-grooves 2b and 2c and the grooves 2a are formed by cutting. In the optical isolator module 1, as shown in FIGS. 1 to 3, two V grooves 2b and 2c are formed on one substrate 2. By setting the two V-grooves 2b and 2c to the same height and using borosilicate glass or quartz as the material for the substrate 2, the blade of the jig in cutting is set to a certain height only. It is possible to complete the formation of the two V-grooves 2b and 2c by feeding the jig once. Therefore, the manufacturing cost of the optical isolator module 1 can be reduced.

Further, in the optical isolator module 1, as shown in FIGS. 1 to 3, two V grooves 2b and 2c are formed on one flat plate-shaped substrate 2, so that the outer shape of the substrate 2 is utilized for one measurement. It is possible to derive the heights of the two V-grooves 2b and 2c (that is, the depths of the bottoms 2b1 and 2c1 from the surface of the substrate 2) only by themselves. Therefore, in this respect as well, the manufacturing cost of the optical isolator module 1 can be reduced.

Further, by forming each light input / output end surface 4a1 or 5a1 of each GIF4a or 5a perpendicular to the optical axis oa, refraction of light at each light input / output end surface 4a1 or 5a1 is prevented. Therefore, it is possible to eliminate the optical axis adjustment process between GIF4a and 5a due to refraction, and positioning in the circumferential direction between GIF4a and 5a becomes unnecessary, so that the number of manufacturing processes is reduced. It will be reduced. Therefore, the manufacturing cost of the optical isolator module 1 can be further reduced.

Further, by forming the clad of GIF5a and the clad of the optical fiber 5b with the same material, the manufacturing cost of the optical isolator module 1 can be further reduced.

It is necessary to shift the opposing GIFs 4a and 5a in the thickness direction (Z-axis direction) of the substrate 2 so that the IL of the optical isolator element 3 is minimized. The opening angles and widths of the outer diameters d4a and d5a and the V grooves 2b and 2c are adjusted so that the height difference H that minimizes IL is set.

According to the optical isolator module 1, the two V-grooves 2b and 2c are set to the same depth, so that the optical axis adjustment of the height difference H between the core axes between GIF4a and 5a is the V-groove 2b and 2c. It is possible to adjust with the outer diameter d5a of GIF5a, which is a smaller dimension than the width of. The extremely precise adjustment process of adjusting the optical axis between the core axes can be performed quickly by reducing the diameter of GIF5a, which is a smaller diameter optical component, reducing the manufacturing time and cost of the optical isolator module 1. It becomes possible to do.

From FIG. 9, the diameter dL of the parallel light propagating through the optical isolator element 3 is set to 85 μm or more and 100 μm or less. Therefore, the size of one side of the optical isolator element is set to be equal to or larger than the diameter dL of the propagating parallel light. Further, the inclination angle θ of the optical isolator element 3 with respect to each light input / output end surface 4a1 or 5a1 of each GIF4a or 5a is 1.0 degree or more and 4.0 degrees or less.

By setting the numerical value of θ above, the height difference H is set to 2.5 μm or more and 10.2 μm or less. Further, the thickness t3a and t3b of the two splitters 3a or 3b are both set to 0.2 mm, and the thickness t3c of the Faraday rotator 3c is set to 0.42 mm. Therefore, the total thickness of the optical isolator element 3 is 0.82 mm, but if the diameter dL of the parallel light is 85 μm or more and 100 μm or less even with the total thickness of 0.82 mm, the parallel light can be propagated and transmitted to the optical isolator element 3. The applicant found that by verification.

From the above parallel light diameters dL and θ, the total thickness of the optical isolator elements 3, and the height difference H, the outer diameter d4a of GIF4a is set to 125 μm and the outer diameter d5a of GIF5a is set to 118.5 μm as described above. According to such a configuration of the optical isolator module 1, it is possible to realize a reliable reduction of IL by optimizing the design of each part. Further, by configuring the optical isolator element 3 with two polarizing elements 3a and 3b and one Faraday rotator 3c, it is possible to reduce the number of optical elements constituting the optical isolator element 3. Therefore, in this respect as well, the manufacturing cost of the optical isolator module 1 can be further reduced.

More preferably, the inclination angle θ of the optical isolator element 3 is set to 1.5 degrees or more and 3.5 degrees or less, and the height difference H is set to 3.8 μm or more and 8.9 μm or less. According to the configuration of the optical isolator module 1 as described above, even in the optical isolator module 1 in which the outer diameters d4a and d5a of the GIFs 4a and 5a and the diameter dL of the parallel light are set, the space between the two GIFs 4a and 5a is set. More reliable optical coupling can be realized.

Next, the optical isolator module 8 according to the second embodiment of the present invention will be described with reference to FIG. The same parts as those of the optical isolator module 1 are designated by the same reference numerals, and the same or overlapping description will be omitted.

The difference between the optical isolator module 8 and the optical isolator module 1 is that the optical incident side end of GIF4a (the end on which the opposite end surface of the optical emission end surface 4a1 is formed) is joined to the optical fiber 4b. However, it is a point that is optically directly connected to face at least a part of the light emitting source 6.

Examples of the light emitting source 6 include a silicon photonics element and a PLC. When the light emitting source 6 is a PLC, the light emitting end surface or the light emitting port of the optical waveguide in the PLC is optically directly connected to the end portion of the GIF 4a. Further, the GIF 4a and the light emitting source 6 are sealed and bonded with an adhesive (for example, a resin optical adhesive that is cured by the ultraviolet light) that is consistent with the core of the GIF 4a. When the light emitting source 6 is a PLC, it is more desirable that the adhesive is consistent with the refractive index of the core of the optical waveguide of the PLC.

According to such a configuration of the optical isolator module 8, it is not necessary to use the optical fiber 4b by directly and optically connecting the GIF 4a and the light emitting source 6. Therefore, the manufacturing cost of the optical isolator module 8 can be reduced. Further, since it can be directly optically connected to the light emitting source 6, it is possible to realize the optical isolator module 8 in which the adjustment point of the optical axis with the light emitting source 6 and the increase of the optical axis adjusting process are prevented. It becomes.

The optical isolator module 1 or 8 according to the present invention can be variously changed depending on the technical idea thereof, and for example, the optical isolator element 3 can be a polarization-independent type. When the optical isolator element is a polarization-independent type, as an example, the optical isolator element can be formed of two birefringent crystals, one Faraday rotator, and one half-wave plate. However, in order to reduce the manufacturing cost of the optical isolator module by suppressing the number of optical elements constituting the optical isolator element, it is desirable that the optical isolator element is a polarization-dependent type. When a birefringent crystal is used, when parallel light is incident on the optical isolator element, the abnormal light is shifted by the birefringence, and the optical path is changed by this shift.

Further, in the groove 2a, instead of the concave groove, the optical isolator element 3 may be arranged by forming the inclination angle θ at the bottom of the groove. Further, the entire groove may be formed obliquely with respect to the plane perpendicular to the optical axis oa at the inclination angle θ.

1, 8 Optical isolator module 2 Substrate
2a groove
2b, 2c V-groove
2b1, 2c1 Bottom of V-groove 3 Optical isolator element
3a, 3b Polarizer
3c Faraday rotator
4a 1st graded index optical fiber
4a1 Light emission end face of the first graded index optical fiber
4b, 5b single mode optical fiber
5a Second graded index optical fiber
5a1 Light incident end face of second graded index optical fiber 6 Light source 7 Adhesive
ca1 1st graded index optical fiber core axis
ca2 2nd graded index optical fiber core axis
d4a Outer diameter of first graded index optical fiber
d5a Outer diameter of second graded index optical fiber
dL Diameter of parallel light H Height difference
L4a Length of first graded index optical fiber
L5a Second graded index fiber optic length
oa optical axis
t3a, t3b Polarizer thickness
t3c Faraday rotator thickness θ tilt angle of optical isolator element

Claims (2)

Grooves are formed on the surface of the borosilicate glass or quartz substrate.
An optical isolator element composed of at least two or more polarizing elements and one or more Faraday rotators is inclinedly arranged in the groove.
At least one or more transducers are arranged face-to-face with respect to the two optical planes of the Faraday rotator.
Two V-grooves are formed via the grooves facing the polarizing element, and the longitudinal directions of the two V-grooves are coaxial and have the same depth.
The first graded index optical fiber and the second graded index optical fiber having different outer diameters are arranged in two V grooves, respectively, and the core axis and the second graded of the first graded index optical fiber are arranged. A height difference is formed in the depth direction of the V-groove between the core axes of the index optical fiber.
Each optical input / output end face of each graded index optical fiber is formed perpendicular to the optical axis.
Light is propagated to the first graded index optical fiber having a relatively thick outer diameter, converted into parallel light and emitted, and then parallel light is incident on the optical isolator element to change the optical path.
Next, parallel light is incident on the second graded index optical fiber having a relatively small outer diameter and further propagated to the single-mode optical fiber.
The length of each graded index optical fiber is set to an odd multiple of one-fourth or one-fourth of the meandering period of light propagating through the graded index optical fiber.
The clad of the second graded index optical fiber and the clad of the single mode type optical fiber are made of the same material.
The diameter of the parallel light propagating through the optical isolator element is 85 μm or more and 100 μm or less .
The inclination angle of the optical isolator element with respect to each optical input / output end face of each graded index optical fiber is 1.5 degrees or more and 3.5 degrees or less.
The outer diameter of the first graded index optical fiber is 125 μm, and the outer diameter of the second graded index optical fiber is 118.5 μm.
The height difference is 3.8 μm or more and 8.9 μm or less,
The optical isolator element is composed of two polarizing elements and one Faraday rotator.
An optical isolator module in which the thickness of the two stators is 0.2 mm and the thickness of the Faraday rotator is 0.42 mm . The first graded index optical fiber is directly optically connected to the light emitting source of the propagated light, and the light incident end face and the light emitting source of the first graded index optical fiber facing the light emitting source. The optical isolator module according to claim 1, wherein the optical isolator module is joined by an adhesive matching the refractive index of the core of the first graded index optical fiber.

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