WO2018190254A1 - Plano-convex lens, fiber array module and light receiving module - Google Patents

Abstract

This disclosure relates to a plano-convex lens 20 provided with a flat surface 21A and a lens surface 23, wherein the lens surface 23 is provided with a first convex surface A1 and a second convex surface A2 that are disposed on a flat base surface 21B and have a spherical shape, and the diameter D1 of a first virtual circle formed on the base surface 21B by the first convex surface A1 and the diameter D2 of a second virtual circle formed on the base surface 21B by the second convex surface A2 are larger than a center-to-center distance dp between the first virtual circle and the second virtual circle.

Description

Plano-convex lens, fiber array module and light receiving module

The present disclosure relates to a plano-convex lens having two convex surfaces, a fiber array module including the same, and a light receiving module.

A light receiving module for optical communication has been proposed (see, for example, Patent Documents 1 and 2). The light receiving modules of Patent Documents 1 and 2 collimate the beam emitted from the first optical fiber by the lens array, reflect a part of the beam collimated by the lens array to the lens array by the filter, and pass to the second fiber. return. On the other hand, in order to monitor the light in the transmission path, a part of the beam branched by the filter is received by the light receiving element installed in the subsequent stage.

In Patent Document 1 published after Patent Document 2, the distance between the first optical fiber and the second optical fiber is 500 μm, and the distance between the lens arrays is also 500 μm. However, miniaturization of modules for optical communication has progressed, and it is required to arrange optical fibers at intervals smaller than 500 μm such as 250 μm and 127 μm.

JP 2009-093131 A JP 2005-037662 A

Since spherical lenses are easy to design and manufacture, it is desirable to use them for lens arrays. However, in the reflection type lens-optical fiber coupling system as in Patent Documents 1 and 2, if the interval between the optical fibers is narrowed, the coupling efficiency of the beam reflected by the filter to the second fiber decreases. Occurred. On the other hand, it is conceivable to reduce the lens diameter by increasing the refractive index of the lens array, but a lens material having a high refractive index is not practical.

The present disclosure provides a reflection-type lens-optical fiber coupling system that uses a filter without using a lens material having a high refractive index even when the distance between the first optical fiber and the second optical fiber is narrow. The object is to efficiently couple the reflected beam into the second fiber.

The plano-convex lens of the present disclosure is
A plano-convex lens having a flat surface and a lens surface,
The lens surface includes a first convex surface and a second convex surface having a spherical shape disposed on a flat base surface,
The diameter of the first virtual circle formed on the base surface by the first convex surface and the diameter of the second virtual circle formed on the base surface by the second convex surface are the first virtual circle and the It is larger than the distance between the centers of the second virtual circles.

The plano-convex lens of the present disclosure may further include a flange portion that relaxes a shape change at a boundary between the first convex surface and the second convex surface between the first convex surface and the second convex surface.

In the plano-convex lens of the present disclosure, the first convex surface and the second convex surface are respectively a first straight line passing through a vertex of the first convex surface and a center of the first virtual circle, a vertex of the second convex surface, and the second convex surface. Two lights emitted from the first position and the second position in a predetermined plane including two straight lines of the second straight line passing through the center of the two imaginary circles are converted into parallel light, and are incident from the first convex surface. When the light is reflected by the reflecting surface arranged on the flat surface, the second convex surface may collect the parallel light at the second position.

In the plano-convex lens of the present disclosure, the first convex surface and the second convex surface are respectively a first straight line passing through a vertex of the first convex surface and a center of the first virtual circle, a vertex of the second convex surface, and the second convex surface. A first position within a predetermined plane including two straight lines of a second straight line passing through the center of two virtual circles, and the light incident on the flat surface from the second position is converted into parallel light and the first position And the parallel light emitted from the first convex surface at a predetermined distance from the second position so as to converge on one point of the reflecting surface perpendicular to the first straight line and the second straight line. When the light is reflected at the one point, the second convex surface may collect the parallel light at the second position.

In the plano-convex lens of the present disclosure, a filter unit that transmits a part of the parallel light incident from the first convex surface and reflects a part of the parallel light to the second convex surface is provided on the reflective surface. Also good.

The fiber array module of the present disclosure includes a plurality of plano-convex lenses according to the present disclosure, and a plurality of the first convex surfaces and the second convex surfaces are arranged on a common base surface, and A fiber array having two optical fibers with respect to the plano-convex lens, and an end face of each optical fiber being disposed at the first position or the second position of each plano-convex lens. .

The fiber array module of the present disclosure includes a fiber array module according to the present disclosure and a plurality of through holes that transmit the parallel light transmitted from the reflection surface, and each of the parallel light transmitted from the reflection surface An optical component that is incident on one end of the different through-holes and emits parallel light after passing through the through-holes from the other end of each through-hole, and each light emitted from the other end of the plurality of through-holes A second lens array that collects light at a point determined for each through hole.

The light receiving module of the present disclosure includes a fiber array module according to the present disclosure and a light receiving element array that receives each light collected by the second lens array.

According to the present disclosure, in a reflection type lens-optical fiber coupling system, light that should be returned to the optical fiber after being partially branched for monitoring can be efficiently supplied to the optical fiber without using a lens material having a high refractive index. Can be combined.

It is a perspective view of the plano-convex lens of this indication. An example of the virtual circle formed on a base surface by a convex surface is shown. The 1st example of the metal mold | die of a planoconvex lens is shown. The 2nd example of the metal mold | die of a planoconvex lens is shown. An example of the twin peak plano-convex lens which concerns on 1st Embodiment is shown. The structural example of the fiber array module which concerns on 2nd Embodiment is shown. It is explanatory drawing about the optical system in 1st and 2nd embodiment. It is a figure explaining the difference with the two-piece form and the twin peak form of this indication, (a) shows a two-piece form, (b) shows a twin peak form. It is a figure explaining the variation of a buttocks, (a) shows the form where a buttocks is lower than a peak, and (b) shows the form where a peak and a peak are the same height. The 3rd example of the metal mold | die of a planoconvex lens is shown. In 1st and 2nd embodiment, it is a graph explaining the conditions which comprise the optical system without vignetting in case the period space | interval between fibers is 250 micrometers. In 1st and 2nd embodiment, it is a graph explaining the conditions which comprise the optical system without vignetting in case the period space | interval between fibers is 127 micrometers. An example of the angle dependence in a filter part is shown. An example of the single-peaked plano-convex lens according to the third embodiment is shown. The structural example of the fiber array module which concerns on 3rd Embodiment is shown. It is explanatory drawing about the optical system in 3rd Embodiment. An example of the twin peak plano-convex lens which concerns on 4th Embodiment is shown. The structural example of the fiber array module which concerns on 5th Embodiment is shown. It is explanatory drawing about the optical system in 4th and 5th embodiment. In 4th and 5th embodiment, it is a graph explaining the conditions which comprise the optical system without vignetting in case the periodic space | interval between fibers is 250 micrometers. In 4th and 5th embodiment, it is a graph explaining the conditions which comprise the optical system without vignetting in case the period space | interval between fibers is 127 micrometers. An example of the single-peaked plano-convex lens according to the sixth embodiment is shown. The structural example of the fiber array module which concerns on 6th Embodiment is shown. It is explanatory drawing about the optical system in 6th Embodiment. An example of the fiber array module which concerns on 7th Embodiment is shown. An example of the light reception module which concerns on 7th Embodiment is shown. An example of the fiber array module which concerns on 8th Embodiment is shown. An example of the light reception module which concerns on 8th Embodiment is shown. An example of the connection surface seen from the z direction of the fiber array in a 9th embodiment is shown. An example of the structure seen from the x direction of the light reception module in 9th Embodiment is shown.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In addition, this indication is not limited to embodiment shown below. These embodiments are merely examples, and the present disclosure can be implemented in various modifications and improvements based on the knowledge of those skilled in the art. In the present specification and drawings, the same reference numerals denote the same components.

(First embodiment)
FIG. 1 shows a perspective view of the optical system of the present embodiment. The optical system of the present disclosure includes a bimodal plano-convex lens 20, two optical fibers 11 </ b> A and 11 </ b> B, and a filter unit 4. The end face P1 of the optical fiber 11A is disposed at the first position, and functions as the first optical fiber. The optical fiber 11B has the end face P2 disposed at the second position, and functions as a second optical fiber. The surface of the filter unit 4 on the plano-convex lens 20 side functions as a reflecting surface.

First, the plano-convex lens 20 will be described. The plano-convex lens 20 of the present disclosure has a lens surface 23 on a base surface 21B of a flat substrate 21 made of a rectangular lens material having sides parallel to the xyz orthogonal coordinate axes in the drawing. The lens surface 23 includes a spherical convex surface A1 that functions as a first convex surface, a spherical convex surface A2 that functions as a second convex surface, and a flange A3.

The convex surface A1 is a part of a spherical surface having a first straight line R1 parallel to the z-axis as a rotation center and an intersection with the straight line R1 as a peak P6. The convex surface A2 is a part of a spherical surface having a second straight line R2 parallel to the z-axis as a rotation center and an intersection with the straight line R2 as a peak P8. The convex surface A2 is a part of a spherical surface having a shape obtained by translating the convex surface A1 in the x direction by the peak interval dp.

FIG. 2 shows an example of a virtual circle formed on the base surface 21B by the convex surfaces A1 and A2. On the base surface 21B, the convex surface A1 forms a first virtual circle centered on the point C1 on the straight line R1 and having a diameter D1. Also for the convex surface A2, a second virtual circle having a diameter D2 and a point C2 on the straight line R2 as the center point is formed on the base surface 21B. The vertex P6 of the convex surface A1 and the center point C1 of the first virtual circle pass through the first straight line R1, and the vertex P8 of the convex surface A2 and the center point C2 of the second virtual circle pass through the second straight line R2.

The lens diameters of the two convex surfaces A1 and A2 that perform these lens functions are set larger than the peak interval dp. That is, the peak interval dp is smaller than the diameters D1 and D2, and the first virtual circle and the second virtual circle are arranged so as to overlap each other. In the embodiment, an example in which the diameters D1 and D2 are equal is shown, but the present disclosure is not limited to this, and the diameters D1 and D2 may be different.

A first virtual circle overlap each other part of the second imaginary circle as shown in FIG. 1, is provided with saddle A3 width w _s. As can be seen from the contour lines indicated by the dotted lines in FIG. 1, the flange portion A3 also protrudes from the base surface 21B and is configured to smoothly connect the two convex portions A1 and A2. As a whole, the lens surface 23 composed of the convex surfaces A1 and A2 and the flange A3 has a straight line passing through the midpoint between the two peaks P6 and P8 and parallel to the z-axis as the lens center axis Ac. A straight line passing through the two peaks P6 and P8 and parallel to the x-axis is hereinafter referred to as a peak line Bc.

The optical fiber 11A having an optical axis parallel to the z-axis is disposed so that the optical axis intersects the peak line Bc at a predetermined distance outside the straight line R1 that is the center of the convex surface A1. The outgoing light from the optical fiber 11A is incident on the peak P6 of the convex surface A1 with an offset to the outside. The incident light is reflected by a predetermined amount of intensity by a mechanism described later, and is collected and incident on the optical fiber 11B arranged symmetrically with respect to the lens center axis Ac with respect to the optical fiber 11A. Yes.

Such a lens can be produced by a glass mold method using a mold. FIG. 3 shows a contour map of the mold viewed from the z-axis direction in the mold manufacturing process. First, as shown in FIG. 3, concave surfaces corresponding to the convex surfaces A1 and A2 are formed on the mold surface. In the concave shape manufacturing process, the overlapping parts become deeper concave surfaces of the other party, and a ridge line is formed at the boundary. When such a ridge line exists in the mold, there is a possibility that mass transfer during the molding operation is hindered. Therefore, as shown in FIG. 4, the boundary is cut away so as not to be projected onto the xy-plane projected portion Pd of the light intensity distribution pattern emitted from the optical fiber, and the shape change at the boundary is alleviated. As a result, a shape having a flange A3 as shown in FIG. 1 is obtained.

Next, in order to explain the optical system of the present embodiment more easily, it will be described with reference to FIG. 5 which is a cross-sectional view taken along a plane Pc including straight lines R1 and R2. In the present embodiment, the optical fibers 11A and 11B are disposed on the lens surface 23 side, and the filter unit 4 is disposed on the flat surface 21A side. The end face P1 of the optical fiber 11A and the end face P2 of the optical fiber 11B are disposed at the first position and the second position, respectively. Longitudinal direction of the optical fiber 11A and 11B are arranged in parallel to the lens center axis _{A C} plano 20 in the plane _{P C.} Plane _{P C} is a plane formed by the optical fibers 11A and 11B. Hereinafter, this embodiment is referred to as Type I.

The plano-convex lens 20 according to the present embodiment has two convex surfaces A1 and A2 on the lens surface 23. The convex surface A1 is a rotating curved surface that is parallel to the lens center axis Ac and has a straight line R1 included in the plane Pc formed by the optical fibers 11A and 11B, and the convex surface A2 is also parallel to the lens center axis Ac and light. It is a rotation curved surface with a straight line R2 included in a plane Pc formed by the fibers 11A and 11B as a rotation center, and the straight lines R1 and R2 are symmetrical with respect to the lens center axis Ac and are two fiber center lines. It is offset inward by a predetermined distance.

In such a configuration, the light emitted from the end face P1 of the optical fiber 11A enters the plano-convex lens 20 from the convex surface A1. The convex surface A1 makes the light emitted from the end surface P1 of the optical fiber 11A parallel light. The light that has become parallel light on the convex surface A1 passes through the plano-convex lens 20, and part of the light is reflected toward the convex surface A2 by the filter unit 4 disposed on the flat surface 21A. The convex surface A2 condenses the parallel light reflected by the filter unit 4 on the end surface P2 of the optical fiber 11B. Thereby, the parallel light reflected by the filter unit 4 enters the optical fiber 11B.

The plano-convex lens 20 according to the present embodiment collects the parallel light reflected by the filter unit 4 on the end face P2 of the optical fiber 11B. For this reason, the plano-convex lens 20 according to this embodiment can efficiently couple the light after the monitor light is partially branched (hereinafter expressed as tapped) to the optical fiber 11B.

(Second Embodiment)
FIG. 6 shows a configuration example of the fiber array module according to the present embodiment. This corresponds to the case where type I plano-convex lenses 20 are arrayed. The fiber array module according to this embodiment includes a fiber array 1 in which optical fibers 11A-1 to 11A-4 and 11B-1 to 11B-4 are alternately arranged, and a plurality of lens surfaces 23 of the first embodiment. And lens array 2 in which -1 to 23-4 are arranged. The lens array 2 functions as a first lens array.

In the lens array 2, spacers 22 are disposed on both ends of the plurality of lens surfaces 23-1 to 23-4. The spacer 22 may be formed in the mold by forming a spacer-corresponding recess at the same time as the lens-corresponding recess, and may be formed by a molding method at the same time as the lens is formed, or a plate having a predetermined thickness may be sandwiched.

Fiber array 1 and the lens array 2 has four fibers in the first embodiment - a lens optical system, are arranged in parallel on a plane P _C. Specifically, the lens array 2 includes the plurality of lens surfaces 23-1 to 23-4 of the first embodiment. Each twin peak plano-convex lens 20 provided in the lens array 2 includes the fiber lens optical system of the first embodiment as a basic unit. Lens center axis A _C of the lens surfaces 23 are arranged in parallel in a plane P _C. The fiber array 1 has two optical fibers 11A and 11B for each of the twin peak lens surfaces 23-1 to 23-4. The end faces PL11 of the fiber array 1 on which the end faces of the optical fibers 11A-1 to 11A-4 and the end faces of 11B-1 to 11B-4 are arranged are arranged in parallel with the peak line Bc.

The optical system in FIGS. 5 and 6 will be described with reference to FIG. Hereinafter, the directions will be described following the orthogonal xyz coordinate axes in the drawing. The left side of the figure, in the xz plane, is parallel to the z-axis, the fiber array 1 optical fibers 11A and 11B are arranged at intervals d _f in the x-axis direction is disposed. The fiber array 1 is configured to be held by a housing such as Tempax glass with a plane parallel to the x-axis and forming a predetermined angle with respect to the y-axis as an end surface.

lens surface 23 having the lens center axis A _C parallel to the z-axis, as a common plane plane perpendicular to the z-axis, the x-axis direction in the fiber array 1 times the spacing 2d _f, and a lens surface 23 adjacent They are arrayed at a distance between the adjacent d _n. The convex surface A1 is a rotating curved surface centered on a straight line R1 that is included in the plane Pc formed of the fiber array and is parallel to the z axis, and has a lens action. Moreover, it is offset inward (to the lens center axis Ac side) by a predetermined distance with respect to the optical axis of the optical fiber 11A. Convex A2 from the lens center axis Ac, is formed in a symmetrical shape with convex surface A1 across the saddle A3 width w _s. The distance _{d p} of the straight line R1 and the line R2 of the convex surface A1 and A2 (hereinafter referred to as peak interval _{d p),} is set to the interval _{d f} is less than the distance.

The end surface PL11 of the fiber array 1 and the lens surface 23 of the lens array 2 are disposed with an air layer 3 having a thickness equal to the convex focal length fv interposed therebetween. The distance between the lens surface 23 and the flat surface 21A, that is, the thickness t _l of the lens is set to a thick predetermined value than the concave side focal length f _c.

The relative position of the fiber array 1 and the lens array 2, x-axis direction, the lens center axis A _C is the center line of the adjacent fibers to each other of the fiber array 1 (in this figure, the center line of the optical fiber 11A and the optical fiber 11B) to as match, y direction is so formed with an array of lens center axis a _C plane is a plane with said matching formed at the centerline of the fiber array 1, and z directions, the end face of the fiber array 1 the distance between the peak P6 and P8 of PL11 and the lens array 2 is set such that the matching convex side focal length f _v plano 20.

A filter unit 4 having a function of reflecting / transmitting light of a predetermined wavelength at a desired ratio may be provided on the surface of the lens array 2 on the flat surface 21A side.

In such a configuration, the path of light emitted from the end face P1 of the optical fiber 11A will be considered by light ray approximation. The end face P1 of the optical fiber 11A is located on the convex focal plane PL23V, and the straight line R1 in the lens surface 23 is offset in the x direction with respect to the fiber center line as described above. the end face P1 of the fiber 11A as a point light source, and refracted light to the lens center axis a _C side incident on the convex surface A1 of the lens array 2 emitted therefrom, parallel constituting the lens center axis a _C at a predetermined angle φ It travels through the lens as a light beam. Among them, light or central ray in parallel to emit from the end of the optical fiber 11A to the z-axis is a lens center axis A _C is incident on the plano-convex lens 20, thus passing through the concave side focus.

Lens thickness t _l is thicker than the concave side focal length f _c, yet have been set to a predetermined value which is located a flat surface 21A at the point where the central ray of the above crosses the lens center axis A _c, on the flat surface 21A When the filter portion 4 is provided, a predetermined intensity component of the parallel light travels straight at an angle ψ relative to the lens center axis a _C passes through the filter portion 4, but the rest of the intensity component in the filter section 4 It reflected and reaches the convex A2 in a symmetric x position relative to the lens center axis a _C. The reflected light reaches the convex A2 is a parallel light having passed through the concave side focal, emitted from the optical fiber 11A, follows a symmetrical path with respect to twin-peak flat optical path incident on the convex lens 20 and the lens center axis A _C , it will be focused on the end surface P2 of the optical fiber 11B in the optical fiber 11A and symmetrical positions with respect to the end lens center axis a _C.

Here, if the lens thickness t ₁ is smaller than the predetermined value, the reflected light from the filter unit 4 reaches the surface of the convex surface A2 on the lens central axis _AC side, where the parallel light converges. Instead, it spreads at the end face P2 of the optical fiber 11B. On the other hand, when the lens thickness t ₁ is thicker than the above-mentioned predetermined value, the reflected light from the filter unit 4 reaches the outer surface of the convex surface A2, and the parallel light is excessively converged, so that the end surface of the optical fiber 11B. It spreads at P2. In either case, the optical axis of the reflected light beam at the filter unit 4 also deviates from the end face P2 of the optical fiber 11B. Therefore, the thickness t _l of the lens thicker than the concave side focal length f _c, moreover flat surface 21A to the point where the central ray of the above crosses the lens center axis A _c needs to be set to a predetermined value situated.

Note that light transmitted by the filter unit 4, the refractive index of the adjacent medium is given the same as the refractive index n _v of the air layer 3 is emitted at an angle [psi. Although not shown in the figure, if the refractive index of the adjacent medium is the same as the refractive index of the lens array 2, the light is emitted at an angle φ.

Next, the above description is formulated using mathematical expressions. 7, light rays are emitted from the optical fiber 11A and incident on the convex surface A1 of the lens surface 23 passes through the air layer 3 having an end face P1 to the convex side focal plane PL23V forms a lens center axis A _C and the angle φ It becomes parallel light. Among them light, for light incident on the peak P6 convex A1, since the lens stitched plane of incidence point perpendicular to the lens center axis A _C, a peak center angle of incidence of the ray angle [psi, an output angle Between a certain angle φ and the refractive indexes n _v and n _c , the Snell law expressed by the following equation is established.
(Equation 1)
n _v sinψ = n _c sinφ (1)
Here, n _v and n _c are each air refractive index and lens refractive index.

Further, in the fiber array 1 is distance d _f, since the lens array 2 is not being arrayed at the multiple of the spacing 2d _f, the focal length f _v to the convex side focal plane _PL23V, and concave focal plane the focal length _{f c} to PL23C includes a fiber spacing _{d f,} at the exit angle of peak intervals _{d p} of the convex surface A1 and convex A2, the angle is an incident angle to the peak P6 [psi, and the peak P6 to the lens array 2 From the value of a certain angle φ, it is determined by the following equations (2) and (3).
(Equation 2)
f _v = {(d _f −d _p ) cotφ} / 2 (2)
(Equation 3)
f _c = {(d _f −d _p ) cot φ} / 2 (3)

Similarly, the lens thickness t ₁
(Equation 4)
t ₁ = d _f cot φ / 2 (4)
Holds.

Further, the peak curvature radius R _p is given by the following equation.
(Equation 5)
R _p = (n _c −n _v ) f _v / n _v (5)

Convex A1 and convex A2 constituting the twin peaks are both but not may satisfy the equation (1) to (5), satisfy these relationships, symmetry axis parallel to the lens center axis A _C The rotation curved surface can be most easily approximated by a spherical surface having a radius of R _p obtained by Equation (5). Given the fiber spacing d _f , the lens peak spacing d _p , the lens refractive index n _c , the air refractive index n _v , and the angle φ that is the reflection angle at the filter unit 4, the equations (2) and (3) The focal lengths f _v and f _{c of the} convex / concave lens 20 of the plano-convex lens 20 are determined, that is, the distance between the optical fibers 11A and 11B and the plano-convex lens 20 and the lens thickness t ₁ are determined from the equation (4). Moreover, the peak curvature radius which becomes the shape standard of the mold used in the molding process, which is the lens manufacturing process, is also known from the equation (5).

Next, the conditions for establishing such an optical system will be described. In order to realize low-loss coupling between the optical fibers 11A and 11B, it is necessary to suppress vignetting on the lens surface 23 as much as possible. The outgoing light from the optical fiber 11A spreads according to the NA of the optical fiber, but the spread is often expressed as the propagation of a Gaussian beam with the end of the optical fiber as the beam waist position. The power distribution of the Gaussian beam emitted from the end face P1 of the optical fiber 11A and reaching the convex surface A1 is 99.75% of the total power in the range from the beam center to 1.73 times the beam radius ω. Therefore, if the range up to this point is the beam diameter BD of the beam that has reached the convex surface A1, it is given by the following equation.

Here, ω ₀ and λ are the mode radius of the optical fiber 11A and the wavelength of light, respectively.

Next, the conditions required for the beam diameter on the lens surface 23 from the configuration of the lens will be considered according to FIG. When the peak interval d _p between the convex surface A1 and the convex surface A2 is increased, as shown in FIG. 8A, the convex surface A1 and the convex surface A2 are overlapped to form two individual convex surfaces. That is, the flange portion A3 is disposed on the same plane as the base surface 21B. This is called a two-piece state, and is considered by comparing this with a twin peak state.

First, a two-piece state will be considered according to FIG. In the two-piece state, in order to realize low-loss fiber-fiber coupling without vignetting, the distance D _{E in} the x-axis direction between the fiber center line parallel to the z axis and the lens outer edge near the center line Must be larger than half of the beam diameter BD at the lens surface,
(Equation 7)
BD / 2 <D _E = d _p / 2-w _s / 2- (d _f −d _p ) / 2 = (2d _p −d _f −w _s ) / 2
BD <2d _p −d _f −w _s (7)
Must hold. This is a two-piece condition. Here, the following (2d _p −d _f −w _s ) is called a two-piece condition index. Contrary to the condition of Expression (7), if the beam diameter BD on the lens surface is larger than the two-piece condition index, it is necessary to take a twin peak configuration in order to construct an optical system without vignetting.

On the other hand, in the twin peak system shown in FIG. 8B, the condition without vignetting is that the distances D _C and D _E between the fiber center line and both ends of the outer edge of the lens in the x-axis direction in FIG. Must be larger than half of the beam diameter BD,
(Equation 8)
BD <d _f −max (d _n , w _s ) (8)
Must hold. As will be described later, this condition is a wider condition including conditional expression (7).

Here, it should be noted that the twin peak shape is not necessarily required. In both examples in FIG. 8, the beam area on the lens surface extends on both sides of the peaks P6 and P8, but as shown in FIG. 9A, the beam area is distributed only outside the peaks P6 and P8. If you want to. This case corresponds to a case where the beam diameter BD on the lens surface is sufficiently small to satisfy the conditions of the expressions (7) and (8) and the following expression.
(Equation 9)
BD <d _f −d _p (9)

In such a case, the lens shape does not need to be a twin peak, and may be a trapezoidal shape as shown in FIG. 9B or the contour map of FIG. 10, and this is easier to mold and more durable. high.

There is one more condition. It relates to a peak radius of curvature R _p, which is a formation condition of the mold represented by the following formula.
(Equation 10)
R _p = (n _c −n _v ) f _v / n _v ≧ 150 μm (10)

The reason is as follows. The plano-convex lens 20 which is the subject of the present disclosure can be manufactured by a molding method. This method is a method in which raw glass is pressed into a concave hole formed in a mold and the concave shape is transferred to the convex shape of the glass, and the radius of curvature of the lens surface 23 is that of the machine tool for producing the mold. Depending on the possible radius of curvature of the hole, it is assumed to be 150 μm or more. That is, it means that a depth of a small radius of curvature below this cannot be formed.

Next, the above description is shown in the graphs shown in FIG. 11 and FIG. First, numerical values adopted in the calculation will be described. The numbers adopted are listed below.
Fiber interval d _f : The fiber period interval often used in the fiber array 1 is 250 μm matched to a general-purpose 250 μm pitch tape fiber, and 127 μm arrayed by nesting it vertically. Again, these two values were examined.
-Wavelength [lambda]: 1.55 [mu] m, which is a typical value of the optical communication wavelength band.
Mode radius ω ₀ : It was set to 5.2 μm, which is a typical value at a wavelength of 1.55 μm of a single mode optical fiber.
Lens refractive index n _c : The refractive index of the optical glass used for the lens is distributed from 1.4 of the low refractive index side crown glass to 2.0 of the high refractive index side flint glass. Here, therefore, a lens refractive index _{n c} is considering to 2.0 from 1.4. Air refractive index n _v : The outside of the lens is usually air, so it was set to 1.0.
・ Wear width w _s and adjacent interval d _n : When a lens is manufactured by a glass mold method, a lens-shaped hole is dug into a mold, but a flat portion of about 10 to 20 μm is formed between adjacent holes. is required. The reason is that if the width is narrower than this, a narrow convex part is formed between the adjacent holes, and it deforms under high temperature and high pressure (1 MPa, 450 ° C. or higher) in the mold press process. This is because the durability as a mold is impaired. Therefore, here, the heel width w _s and the adjacent interval d _n are both set to 17 μm.
Angle φ: The filter portion 4 is assumed to be a dielectric multilayer film in which an optical thickness is λ / 4 and a low refractive index transparent material and a high refractive index transparent material are alternately laminated. In terms of structure, the multi-layer film is incident obliquely, but the problem here is the polarization dependence of the transmitted tap light. FIG. 13 shows a calculation example in the case of using SiO ₂ (refractive index 1.44) as the low refractive index material and Ta ₂ O ₅ (refractive index 2.12) as the high refractive index material. According to this calculation example, in order to make the polarization dependence of the transmitted tap light 0.05 dB or less, it is preferable to set the angle φ, which is the reflection angle at the filter unit 4, to 4 degrees or less. Therefore, here, the angle φ, which is the reflection angle at the filter unit 4, is set to 2 degrees in consideration of the influence of the refractive index and film thickness variation in actual fabrication.

Figure 11 is the structure of type I, for the case the fiber spacing d _f of 250 [mu] m, is a graph plotting the relationship between the lens refractive index n _c and the peak radius of curvature R _p for each peak interval d _p. By equation (1) to (5), for each peak interval d _p, a peak radius of curvature R _p for increasing light folding capability with increasing lens refractive index n _c is larger. As the peak distance d _p increases, the radius of curvature R _p decreases to keep the same refractive power because the rays are closer to the peak center.

The three dotted lines in the graph apply the conditions of equations (7) to (8) and (10) to this graph. The dotted line L _2C comes from the two-piece condition of Equation (7), and below this straight line is a region (n _c −R _p ) where a two-piece optical system without vignetting can be constructed. Dotted L _2K topmost are those coming from the twin peaks condition of Equation (8), is an area of the below the straight line can be constructed an optical system without twin peaks form vignetting (n c _{-R p)} . Parallel dashed lines L _PC in the graph horizontal axis and the bottom, which come from the mold processing conditions of the formula (10), above the the straight line is the region of possible configurations (n c _{-R p).}

Therefore, the two-piece configuration is possible only in the region surrounded by the dotted line L _2C and the dotted line L _PC , while the twin peak configuration is possible in the wide region surrounded by the dotted line L _2K and the dotted line L _PC. It can be seen that the degree of freedom in design is more than twice as wide. In particular, under twin peak conditions, it is possible to construct an optical system under conditions where the radius of curvature _Rp is larger, which means that the difficulty of mold processing is low.

12, in the configuration of type I, for the case the fiber spacing d _f of 127 [mu] m, is a graph plotting the relationship between the peak interval d lens refractive index for each _p n _c and the peak radius of curvature R _p. According to the formulas (1) to (5), as in FIG. 11, the peak curvature radius increases for each peak interval due to the increase in the refractive index of the light as the lens refractive index increases. With respect to the peak interval d _p , the ray becomes closer to the center of the peak as it increases, so that the radius of curvature R _p decreases to maintain the same refractive power.

As in FIG. 11, the three dotted lines in the graph apply the conditions of equations (7) to (8) and (10) to this graph. As can be seen at a glance, the region surrounded by the dotted line L _2K and the dotted line L _PC in the twin peak form is overwhelming compared to the region surrounded by the two-piece form the possible dotted line L _2C and the dotted line L _PC. Wide. In comparison with the case fiber distance _{d p} is 250μm shown in FIG. 11, also becomes narrower region of possible as distance _{d f} is narrowed _(n c -R _p), the possible twin peaks form, and dotted _{L 2K} becomes the area surrounded by a dotted line _{L PC,} lens refractive index _{n c} is not configured at 1.44 or less. However, the refractive index 1.501 of BK7, which is a representative of high borosilicate glass reliable, the width of the peak interval _{d p} is capable of an optical system configuration of 91.7 ~ 95.6μm and narrow, twin peaks form It can be seen that can cope with downsizing.

On the other hand it led to 2-piece condition, slightly _{n c} is only possible in a very limited area of 107μm from 1.81 or more in addition peak interval _{d p} also 105. The high refractive index region, in terms of reliability is a region where occurrence of scorch is a problem, it is inevitable said practical applicability is low, the fiber spacing d _f of 127 [mu] m, 2-piece form It can be said that it is not applicable.

(Third embodiment)
FIG. 14 shows the optical system of this embodiment. In the first embodiment, the light emitted from the optical fiber 11A and the incident light beam to the optical fiber 11B overlap each other on the surface and inside of the plano-convex lens in the first embodiment. This is because, in FIG. 7, the fiber spacing d _f narrow, thus corresponding to when the angle φ is the reflection angle at the filter section 4 is small. In this case, the convex surface A1 and the convex surface A2 naturally overlap and become a single-peak lens convex surface. Such a configuration is effective for reducing the reflection angle φ in order to reduce the wavelength dependence and polarization dependence of the transmitted light in the filter unit 4.

In the present embodiment, the first virtual circle and the second virtual circle formed on the base surface 21B by the convex surface A1 and the convex surface A2 are part of a common spherical surface, and the lens surface 23 does not include the flange portion A3. The distance between the centers of the first virtual circle and the second virtual circle is zero. As described above, the present disclosure may include a case where the distance between the centers of the first virtual circle and the second virtual circle is zero.

FIG. 15 shows a configuration example of the fiber array module according to the present embodiment. In the present embodiment, unlike the second embodiment, the fiber array 1 has an irregular pitch. This is in order to reduce the angle φ is the reflection angle, because the narrowed than half of the lens distance d _l of the lens array 2 to fiber distance d _f. In this case, the conditions required for the beam diameter BD on the lens surfaces of the optical fibers 11A-1 to 11 and 11B-1 to 4 are that the light beam does not reach the adjacent lens on the lens surface in FIG. Instead of (7)
(Equation 31)
BD <d ₁ −d _f (31)
It becomes.

(Fourth embodiment)
FIG. 17 shows the optical system of this embodiment. In the present embodiment, the optical fibers 11A and 11B are disposed on the flat surface 21A side of the twin peak plano-convex lens 20, and the filter unit 4 is disposed on the lens surface 23 side with the air layer 3 having a predetermined thickness interposed therebetween. The end face P1 of the optical fiber 11A is disposed at the first position, and functions as the first optical fiber. The optical fiber 11B has the end face P2 disposed at the second position, and functions as a second optical fiber. Longitudinal direction of the optical fiber 11A and 11B are arranged in parallel to the lens center axis _{A C} in the plane _{P C.} Hereinafter, this embodiment is referred to as Type II.

The plano-convex lens 20 according to the present embodiment has, on the lens surface 23, a convex surface A1 that functions as a first convex surface, a convex surface A2 that functions as a second convex surface, and a flange A3. The convex surface A1 is a spherical surface that is parallel to the lens center axis Ac and that is centered on the straight line R1 that is included in the plane Pc, and the convex surface A2 is also parallel to the lens center axis Ac and that is centered on the straight line R2 that is included in the plane Pc The straight lines R1 and R2 are symmetrical with respect to the lens center axis Ac and are offset by a predetermined distance inward.

In such a configuration, the light emitted from the end face P1 of the optical fiber 11A enters the plano-convex lens 20 from the flat surface 21A. The light incident on the plano-convex lens 20 is transmitted through the lens 20 and is emitted from the convex surface A1 into the air layer 3. At this time, the convex surface A1 makes the light emitted into the air layer 3 parallel light.

The light that has become parallel light on the convex surface A1 passes through the air layer 3, and part of the light is reflected toward the convex surface A2 at one point P3 of the partial transmission film 41 provided in the filter unit 4. The partial transmission film 41 functions as a reflection surface. The parallel light reflected by the filter unit 4 enters the plano-convex lens 20 from the convex surface A2. The convex surface A2 condenses the parallel light reflected by the filter unit 4 on the end surface P2 of the optical fiber 11B. Thereby, the parallel light reflected by the filter unit 4 enters the optical fiber 11B.

Since the plano-convex lens 20 according to the present embodiment condenses the parallel light reflected by the convex surface A2 by the filter unit 4 on the end surface P2 of the optical fiber 11B, the light after tapping the monitor light is efficiently applied to the optical fiber 11B. Can be combined.

(Fifth embodiment)
FIG. 18 shows a configuration example of the fiber array module according to the present embodiment. This corresponds to the case where the type II plano-convex lens 20 is arrayed. The fiber array module includes a fiber array 1 in which optical fibers 11A-1 to 11A-4 and 11B-1 to 11B-4 are alternately arranged, and a plurality of lens surfaces 23-1 to 23- of the fourth embodiment. And a lens array 2 in which 4 are arranged. Similarly to the second embodiment, the lens array 2 functions as a first lens array, and a spacer 22 is disposed.

Fiber array 1 and the lens array 2 has four fibers of the fourth embodiment - lens optical system, are arranged in parallel on a predetermined plane P _C. Specifically, the lens array 2 includes the plurality of lens surfaces 23-1 to 23-4 of the fourth embodiment. Each twin peak plano-convex lens 20 provided in the lens array 2 includes the fiber lens optical system of the fourth embodiment as a basic unit. Lens center axis A _C of the lens surfaces 23 are arranged in parallel in a plane P _C. The fiber array 1 has two optical fibers 11A and 11B for each lens surface 23-1 to 23-4. The end faces PL11 of the fiber array 1 on which the end faces of the optical fibers 11A-1 to 11A-4 and the end faces of 11B-1 to 11B-4 are arranged are arranged in parallel with the peak line Bc.

The optical system in FIGS. 17 and 18 will be described with reference to FIG. Hereinafter, the directions will be described following the orthogonal xyz coordinate axes in the drawing. The left end of the figure, in the xz plane, is parallel to the z-axis, the fiber array 1 the optical fiber are arranged at intervals d _f in the x-axis direction is disposed. The fiber array 1 is configured to be held by a housing such as Tempax glass with a plane parallel to the x-axis and forming a predetermined angle with respect to the y-axis as an end surface.

In FIG. 19, unlike the optical systems of the first to third embodiments, the flat surface 21A side of the twin peak lens array 2 is directly attached to the end surface PL11 of the fiber array 1, The lens surface 23 side having a period twice that of the fiber array 1 faces the opposite side. Lens surface 23, z has a lens center axis A _C parallel to the axis, a common plane plane perpendicular to the z-axis, the x-axis direction in the fiber array 1 times the spacing 2d _f, and and adjacent lenses They are arrayed at a distance between the adjacent d _n.

The lens surface 23 includes a convex surface A1 and a convex surface A2. The convex surface A1 is a rotating curved surface centered on a straight line R1 that is included in the plane Pc of the fiber array 1 and is parallel to the z axis, and has a lens action. Moreover, it is offset inward (to the lens center axis Ac side) by a predetermined distance with respect to the optical axis of the fiber 11A. Convex A2 from the lens center axis Ac, is formed in a symmetrical shape with convex surface A1 across the saddle A3 width w _s. Peak interval d _p is the distance between the straight line R1 and the line R2 is given is set by a small distance in length than the fiber spacing d _f.

On the lens surface 23 side of the lens array 2, a filter unit 4 having a partial transmission film 41 perpendicular to the z-axis with the air layer 3 interposed therebetween is disposed. The distance between the lens surface 23 and the partial transmission film 41, that is, the thickness t _r of the air layer is set to a thick predetermined value than the convex side focal length f _v.

The relative position of the fiber array 1 and the lens array 2, x-axis direction, the lens center axis A _C is the center line of the adjacent fibers to each other of the fiber array 1 (in this figure, the center line of the optical fiber 11A and the optical fiber 11B) to as match, y-direction, as formed by an array of lens center axis a _C plane coincides with the plane formed by the center line of the fiber array 1, and z directions, the end face of the fiber array 1 PL11 the distance between the peak P6 and P8 are set to match the concave side focal length f _c of plano-convex lens 20 and. On the right side of FIG. 19, across the air layer 3 of a predetermined distance, a partial transmission with perpendicular to the lens center axis A _C parallel z-axis light in a predetermined wavelength a function of reflecting / transmitting in a desired ratio A membrane 41 is installed. In the first to third embodiments, the partially transmissive film 41 is directly loaded on the flat surface 21A side of the lens array 2, but in this embodiment, the partially transparent film 41 has the same refractive index as that of the lens array 2 separately. The glass substrate 42 is loaded.

In such a configuration, the path of light emitted from the end face of the optical fiber 11A will be considered by light ray approximation. The end surface of the optical fiber 11A is located on the concave focal plane PL23C, and as described above, the straight line R1 that is the center line of the convex surface A1 of the lens surface 23 is offset in the x direction with respect to the fiber center line. ing. Therefore, emitted an end face of the optical fiber 11A as a point light source, transmitted through the lens array 2, light incident on the convex surface A1 is refracted in the lens center axis A _C side, the lens center axis A _C at a predetermined angle It travels through the air layer 3 as parallel rays forming φ. Among them, from the optical fiber 11A is a lens center axis A _C z axis center ray of the light beam i.e. the outgoing light was parallel to the exit, the after exiting the convex surface A1, is reflected by the filter unit 4, to pass through the convex surface A2 become.

The thickness t _r of the air layer is thicker than the convex side focal length f _v, and since the partial transmission film 41 in that the central ray of the above crosses the lens center axis A _c is configured to position, parallel light strength component is straight with an angle of ψ with respect to the partial transmission film 41 lens center axis a _C passes through the, remaining strength component is reflected by the partial transmission film 41, symmetrical with respect to the lens center axis a _C The convex surface A2 is reached at a position in the x direction. The reflected light reaches the convex A2 is a parallel light having passed through the convex side focal, emitted from the optical fiber 11A, follows a symmetrical path with respect to the optical path and the lens center axis A _C incident on the convex surface A1, eventually lens It will be focused on the end surface P2 of the optical fiber 11B in the optical fiber 11A and symmetrical positions with respect to the central axis a _C.

Here, if the if less than the predetermined value thickness t _r is the air layer, the light reflected at the filter section 4 is made to reach a lens center axis A _C-side surface of the convex A2, the parallel light is converged therein However, it spreads at the end face P2 of the optical fiber 11B. On the other hand, if the thickness t _r of the air layer 3 is thicker than a predetermined value, the light reflected at the filter section 4 is made to reach to the outer surface of convex A2, and the parallel light too is converged, the end face of the optical fiber 11B It spreads at P2. In either case, the optical axis of the reflected light beam at the filter unit 4 also deviates from the end face P2 of the optical fiber 11B. Therefore, the thickness t _r of the air layer is thicker than the convex side focal length f _v, yet is partially transmitting film 41 in that the central ray of the above crosses the lens center axis A _c has to be positioned.

Incidentally, the transmitted light in the partial transmission film 41, if the same as the refractive index n _c of the refractive index of the lens array 2 of the glass substrate 42, which is by adhering partially transmitting film 41, although not shown, the angle The light is emitted at ψ. If the glass substrate 42 to which the partially permeable film 41 is attached is a parallel substrate, when the light is finally emitted to the air layer 3, it is emitted at an angle φ.

Next, the above description is formulated using mathematical expressions. 19, parallel to form a light beam incident on the convex surface A1 of the concave focal plane lens surface 23 is emitted from the optical fiber 11A passes through the lens array 2 having an end face to PL23C, the lens center axis A _C and the angle φ It becomes light. Among them light, for light incident on the peak of the convex A1 P6 (the intersection of the straight line R1 and the convex A1 is the center line), since the lens stitched plane of incidence point perpendicular to the lens center axis A _C, light angle ψ is a peak center incident angle of the exit angle at which the angle φ and the refractive index n _v, between n _c is Snell law holds represented by the following formula.
(Equation 11)
n _c sinψ = n _v sinφ (11)

Further, in the fiber array 1 is distance d _f, since the lens array 2 is not being arrayed at the multiple of the spacing 2d _f, the focal length f _v to the convex side focal plane _PL23V, and concave focal plane the focal length f _c to PL23C includes a fiber spacing d _f, the peak interval d _p of the convex surface A1 and convex _A2, angle ψ is a lens central incident angle, and the value of the angle φ is the emission angle, the following formula ( 12), determined by equation (13).
(Equation 12)
f _c = {(d _f −d _p ) cotφ} / 2 (12)
(Equation 13)
f _v = ((d _f −d _p ) cotφ) / 2 (13)

Similarly, the following equation holds true for the thickness t _r of the air layer.
(Equation 14)
_{t r = d f cotφ / 2} (14)

Further, the radius of curvature R _p of the peak is given by the following equation.
(Equation 15)
R _p = (n _c −n _v ) f _c / n _c (15)

Convex A1 and convex A2 constituting the twin peaks are both but not may satisfy the above formula (11) to Formula (14) satisfies these relationships, symmetry axis parallel to the lens center axis A _C The rotation curved surface can be most easily approximated by a spherical surface having a radius of R _p obtained by Expression (15). Given the fiber spacing d _f , the lens peak spacing d _p , the lens refractive index n _c , the air refractive index n _v , and the angle φ that is the reflection angle at the filter unit 4, the equations (12) and (13) the focal length _f c of irregularities two lens surfaces 23, determines the _{f v,} the thickness _{t r} of the air layer from equation (14) is determined. Further, in the lens manufacturing process, the peak radius of curvature, which is a guide for the shape of the mold used in the molding process, can also be found from Expression (15).

Next, conditions for establishing such an optical system will be described. In order to realize low-loss coupling between the optical fibers 11A and 11B, it is necessary to suppress vignetting on the lens surface 23 as much as possible. The outgoing light from the optical fiber 11A spreads according to the NA of the optical fiber, but the spread is often expressed as the propagation of a Gaussian beam with the end of the optical fiber as the beam waist position. The power distribution of the Gaussian beam emitted from the end of the optical fiber and reaching the lens surface 23 is 99.75% of the total power in the range from the beam center to 1.73 times the beam radius ω. Therefore, if the range up to here is the beam diameter BD of the beam reaching the lens surface 23, it is given by the following equation.

Here, ω ₀ and λ are the mode radius of the optical fiber 11A and the wavelength of light, respectively.

Next, regarding the conditions required for the beam diameter BD on the lens surface in Type II, the same considerations as in Type I hold, and the conditions of Equation (7) and Equation (8) are exactly the same. It becomes. However, the condition required for the peak curvature radius R _p is (Equation 17)
R _p = (n _c −n _v ) f _c / n _c ≧ 150 μm (17)
Instead of

From the above, regarding the configuration of type II, as with type I, the relationship between peak interval d _p , beam diameter BD, peak curvature radius R _p (according to equation (15)), and the two-piece condition index is a graph. FIG. 20 and FIG. 21 are obtained. The value adopted in the calculation is the same as type I.

Figure 20 is in the configuration of Type II, the case is a fiber spacing _{d f} of 250 [mu] m, is a graph plotting the relationship between the lens refractive index _{n c} and the peak radius of curvature _{R p} for each peak interval _{d p.} Equation (11) to (13), the equation (16) to (17), for each peak interval _{d p,} a peak curvature in order to increase the light folding capability with increasing lens refractive index _{n c} the radius _{R p} Will grow. The peak interval, as increases, the beam becomes smaller peak radius of curvature R _p to keep the same refractive ability to become closer to the peak center.

The three dotted lines in the graph apply the conditions of equations (7) to (8) and equation (17) to this graph. The dotted line L _2C comes from the two-piece condition of Equation (7), and below this straight line is a region (n _c −R _p ) where a two-piece optical system without vignetting can be constructed. Dotted L _2K topmost are those coming from the twin peaks condition of Equation (8), is an area of the below the straight line can be constructed an optical system without twin peaks form vignetting (n c _{-R p)} . A dotted line L _PC parallel to the horizontal axis of the lowermost graph comes from the die machining conditions of the equation (17), and the region above this straight line is a configurable (n _c −R _p ) region.

Comparing the twin peak and the two-piece configuration, the two-piece configuration is possible only in the area surrounded by the dotted line L _2C and the dotted line L _PC , whereas the twin peak configuration is surrounded by the dotted line L _2K and the dotted line L _PC. It can be seen in a wide area, and the design freedom is about twice as wide. In particular, under twin peak conditions, it is possible to construct an optical system under conditions where the radius of curvature _Rp is larger, which means that the difficulty of mold processing is low.

21, in the configuration of Type II, the case is a fiber spacing _{d f} narrower 127μm than 20 is a graph plotting the relationship between the peak interval _d lens refractive index for each _{p n c} and the peak radius of curvature _{R p.} According to the equations (11) to (13) and (16) to (17), the peak curvature radius is increased because the refractive power of the light increases as the lens refractive index increases for each peak interval, as in FIG. _Rp increases. Regarding the peak interval d _p , the light beam approaches the center of the peak as it increases, so that the peak radius of curvature R _p decreases to maintain the same refractive power.

As in FIG. 20, the three dotted lines in the graph apply the conditions of equations (7) to (8) and (17) to this graph. As can be seen at a glance, the region surrounded by the dotted line L _2K and the dotted line L _PC capable of twin peak form is overwhelming compared to the region surrounded by the dotted line L _2C and the dotted line L _PC capable of two piece form. Wide. Compared with the case where the fiber period interval is 250 μm, the region of possible (n _c −R _p ) becomes narrower as the fiber interval d _f becomes narrower, and the twin peak form is possible because of the dotted line of the twin peak condition and the mold processing condition becomes a triangular area surrounded by the lens refractive index n _c is not configured at 1.44 or less. However, the refractive index 1.501 of a representative glass material reliable borosilicate glass BK7, the width of the peak interval _{d p} is capable of an optical system configuration of 103.5 ~ 106.1μm and narrow, Twin It can be seen that the peak shape can correspond to miniaturization.

While in two-piece condition, _{n c} is only possible a limited area from 1.64 or more in addition peak intervals also 111 of 116Myuemu. The high refractive index region, in terms of reliability also includes regions where occurrence of scorch is a problem, the practical applicability is forced to not give say much lower, the d _f 127 [mu] m, 2-piece form Can be said to have very limited application.

The following can be said by comparing the two-piece and twin peak configurations.
· Two lenses refractive index is a key parameter n _c and when considering the peak radius of curvature R _p, towards the twin-peak configuration, 2-3 times n _c -R _p region of the two-piece construction is wide, free design High degree.
- The direction of the twin-peak structure is also possible to correspond to a smaller fiber spacing d _f, is suitable for miniaturization.
- The direction of the twin peaks configurations, can select the peak radius of curvature R _p is a large value, since the lens diameter can be increased, fiber-to-fiber coupling efficiency can be kept high.
-The twin peak configuration is easier to make because the radius of curvature of the hole when making the mold is larger.

(Sixth embodiment)
FIG. 22 shows the optical system of this embodiment. In the fourth embodiment, the light emitted from the optical fiber 11A and the incident light beam to the optical fiber 11B are overlapped on the surface of the plano-convex lens and the outside in the fourth embodiment. This is 19, the fiber spacing d _f narrow, thus corresponds to when the reflection angle φ is small. In this case, the convex surface A1 and the convex surface A2 naturally overlap and become a single-peak lens convex surface. Such a configuration is effective for reducing the reflection angle φ in order to reduce the wavelength dependency and polarization dependency of the transmitted light in the partial transmission film 41.

In the present embodiment, the first virtual circle and the second virtual circle formed on the base surface 21B by the convex surface A1 and the convex surface A2 are part of a common spherical surface, and the lens surface 23 does not include the flange portion A3. The distance between the centers of the first virtual circle and the second virtual circle is zero. As described above, the present disclosure may include a case where the distance between the centers of the first virtual circle and the second virtual circle is zero.

FIG. 23 shows a configuration example of the fiber array module according to the present embodiment. In the present embodiment, unlike the fifth embodiment, the fiber array 1 has an irregular regular pitch. This is in order to reduce the angle φ is the reflection angle, because the narrowed than half of the lens distance d _l of the lens array 2 to fiber distance d _f. In this case, the condition required for the beam diameter BD on the lens surface of the optical fibers 11A-1 to 4 and 11B-1 to 4 is that in FIG. 24 the light beam does not reach the adjacent lens on the lens surface. The equation (31) described in the third embodiment is obtained.

(Seventh embodiment)
FIG. 25 shows an example of a fiber array module according to this embodiment. The fiber array module shown in FIG. 25 includes the fiber array module shown in FIG. 6, a light shielding plate 7, and a lens array 9. The light shielding plate 7 functions as an optical component, and the lens array 9 functions as a second lens array.

The light shielding plate 7 has a plurality of through holes 71. Each parallel light transmitted from the filter unit 4 enters one end of a different through hole 71. Then, the parallel light after passing through the through holes 71 is emitted from the other end of each through hole 71. The lens array 9 condenses each light emitted from the other end of the plurality of through holes 71 at a point determined for each through hole 71. At this point, the light receiving surface of the light receiving element 81 is disposed.

FIG. 26 shows an example of a light receiving module according to the present embodiment. The light receiving module shown in FIG. 26 includes the fiber array module shown in FIG. 25 and the light receiving element array 8. Each light receiving element 81 provided in the light receiving element array 8 receives each light condensed by the lens array 9. The light receiving module shown in FIG. 26 can be used as a four-array optical tap monitor module.

The application area of this embodiment is, for example, a wavelength 1.55 μm band optical communication system. The module includes a fiber array 1, a lens array 2, a filter unit 4, a light shielding plate 7, a lens array 9, and a light receiving element array 8 from the left side of the figure. The various parameters, including fiber spacing d _f adopts the value in line with the type I described so far.

First, the operation and function of the module will be explained. 95% of the light rays incident on the lens array 2 from the optical fiber 11A are reflected at an angle φ which is the reflection angle at the filter unit 4 and incident on the optical fiber 11B, and 5% of the incident light intensity is tapped to the main line. Return to. The tap light of 5% intensity is an air layer in the subsequent stage and is emitted at an angle ψ that is an emission angle. However, in the subsequent stage of the filter unit 4, the tap light transmitted through the space is mixed. In order to prevent a reduction in crosstalk, a light shielding plate 7 having a through hole 71 is provided. The light shielding plate 7 has a size that is the same as the outer shape of the lens array 2, and a through hole 71 having the beam diameter is formed in the center of the light shielding plate 7 in accordance with the tap optical path. A lens array 9, which is the same as the lens array 2, is installed in the rear stage of the light shielding plate 7 with the direction opposite to that of the lens array 2. The lens array 9 condenses the tap light beam that propagates through the space of the through hole 71 and spreads on the light receiving surface of the light receiving element 81.

The above components will be described below.
Fiber array 1: For the fiber array 1, eight arrays of wavelength 1.3 / 1.55 μm single mode tape fibers were used as optical fiber members. This was aligned with a 60-degree V-groove plate using Tempax glass, covered with an upper lid, fixed with UV adhesive, and end-face polished to produce a connecting fiber array 1. Fiber distance d _f is the same as the tape fiber used. The optical fiber optical axis is in the z direction, and the connection end surface with other elements is parallel to the x axis, and is set to be inclined by 8 degrees with respect to the y axis direction in order to reduce return light due to end surface reflection. . The 8 ° oblique end surface has an AR coating for a wavelength of 1.55 μm.

Lens array 2: made of borosilicate glass, and lens surfaces 23 are formed at a predetermined array interval. Spacers 22 that are integrally formed at the time of lens molding are installed at both ends of the lens array 2 in the x direction. The spacer 22 is a trapezoidal convex part, and the surface thereof is similarly inclined by 8 degrees in accordance with the 8 degree oblique end face of the fiber array 1. The height of the spacer 22 is preferably is set to be a predetermined convex side focal length f _v at the position of for example, a lens central axis Ac.

A filter unit 4 having an angle φ set to 2 degrees is attached to the flat surface 21A of the lens array 2. The reflection / transmission ratio is preferably 95% / 5%, and examples of the material include a SiO ₂ —Ta ₂ O ₅ multilayer film formed by ion beam assisted deposition.

Shading plate 7: The shading plate 7 is made of square infrared absorbing glass. In the central portion, a through hole 71 is formed in parallel with the xz plane and forming an angle ψ between the z-axis direction and the lens center incident direction in accordance with the optical path of the tap light. The x direction array pitch is the same as the lens array 2. The tap light beam propagates without contacting the wall of the through hole 71 of the light shielding plate 7, but irregular reflection components due to structural irregularities generated by reflection and transmission at the lens array 2 and the filter unit 4 in the previous stage are reflected by this light shielding plate. 7 to prevent the cross-talk from reaching the light receiving element array 8.

Lens array 9: Here, the same lens array 9 as the lens array 2 is used. Moreover, only one of the twin peaks is used. Usually, since the light receiving surface of the light receiving element 81 is separated from the package surface, a focal length adjusting resin 91 is inserted between the lens array 9 and the light receiving element array 8 to make the lens array 2 have a longer focal length. The light is collected on the light receiving surface of the light receiving element 81. The reason why the lens array 9 is opposite to the lens array 2 is that the focal length adjusting resin 91 fills the space between the lens array 9 and the light receiving element array 8. The lens array 9 is preferably AR coated only on the flat surface 21A side.

Light receiving element array 8: The light receiving element 81 is, for example, a four-array InGaAs photodiode array. The diode array is preferably sealed. As can be seen from the side view, the light receiving element array 8 is connected to the lens array 9 with an inclination of 8 degrees from the optical axis which is the z-axis direction.

As shown in the side view, since the connection interface from the fiber array 1 to the light receiving element array 8 is all kept oblique, it has a structure that prevents reflected return light.

Assembly process: The process has three processes.
The first step is connection between the fiber array 1 and the lens array 2. This is because the alignment light is incident from the optical fiber 11A-1 and the optical fiber 11A-4 at both ends of the fiber array 1 in the optical fiber waveguide connection device, and is transmitted from the optical fiber 11B-1 and the optical fiber 11B-4. The connection was made in the same process as the normal optical fiber waveguide connection in which the two-axis alignment was fixed while monitoring the light. The connection point is between the spacer 22 and the fiber array 1.
The second step is connection of the light shielding plate 7, the lens array 9, and the light receiving element array 8. These connections are placed in the order of the light receiving element array 8, the lens array 9, and the light shielding plate 7 under the microscope, and are aligned by a visual alignment method so that the light receiving surface of the light receiving element 81 can be seen from the through hole of the light shielding plate 7. Fix the adhesive.
In the third step, the lens array 2 with the fiber array 1, the light receiving element array 8, and the light shielding plate 7 with the lens array 9 are incident on the optical fiber 11A-1 and the optical fiber 11A-4. The connection is fixed while monitoring the output of the light receiving element array 8.

Characteristics: The characteristics of the fabricated 4-channel tap monitor module at a wavelength of 1.55 μm were an insertion loss of 0.4 to 0.5 dB, a return loss of 46 dB or more, and a light receiving sensitivity of 50 to 60 mA / W. Adjacent crosstalk was also 45 dB or more.

(Eighth embodiment)
FIG. 27 shows an example of a fiber array module according to this embodiment. The fiber array module illustrated in FIG. 27 includes the fiber array module illustrated in FIG. 18, the light shielding plate 7, and the lens array 9. The light shielding plate 7 functions as an optical component, and the lens array 9 functions as a second lens array.

The light shielding plate 7 has a plurality of through holes 71. Each parallel light transmitted from the filter unit 4 enters one end of a different through hole 71. Then, the parallel light after passing through the through holes 71 is emitted from the other end of each through hole 71. The lens array 9 condenses each light emitted from the other end of the plurality of through holes 71 at a point determined for each through hole 71. At this point, the light receiving surface of the light receiving element 81 is disposed.

FIG. 28 shows an example of the light receiving module according to the present embodiment. The light receiving module shown in FIG. 28 includes the fiber array module shown in FIG. 27 and the light receiving element array 8. Each light receiving element 81 provided in the light receiving element array 8 receives each light condensed by the lens array 9. The light receiving module shown in FIG. 28 can be used as a 4-array optical tap monitor module.

The application area is an optical communication system with a wavelength of 1.55 μm. The module includes a fiber array 1, a lens array 2, a filter unit 4, a light shielding plate 7, a lens array 9, and a light receiving element array 8 from the left side of the figure. The various parameters, including fiber spacing d _f adopts the value in line with the type II that have been described so far.

First, the operation and function of the module will be explained. 95% of the light beam directly incident on the lens array 2 from the flat surface 21A side and exits from the lens surface 23 without passing through the air layer from the optical fiber 11A is reflected by the filter unit 4 at an angle φ, and again the lens array 2 Then, the light enters the optical fiber 11B, and 5% of the incident light intensity is tapped to return to the main line. The tap light of 5% intensity is an air layer through the filter unit 4 at the subsequent stage and is emitted at an angle φ. However, the tap light transmitted through the space is mixed at the subsequent stage of the filter unit 4. In order to prevent crosstalk from being reduced, a light shielding plate 7 having a through hole 71 is provided. The light shielding plate 7 has a size that is the same as the outer shape of the lens array 2, and a through hole 71 having the beam diameter is formed in the center of the light shielding plate 7 in accordance with the tap optical path. A lens array 9, which is the same as the lens array 2, is installed behind the light shielding plate 7 with the same orientation as the lens array 2. The lens array 9 condenses the tap light beam that propagates through the space and spreads on the light receiving surface of the light receiving element 81.

The following will describe each of the above components that does not overlap with the seventh embodiment.
Fiber array 1: Unlike the seventh embodiment, the AR coating is not applied to the surface of the end face that is oblique by 8 degrees.
Lens array 2: It is made of borosilicate glass, and the lens surface 23 is formed in a positive direction of the z axis at a predetermined array interval. Spacers 22 are provided at both ends of the lens array 2 in the x direction. The spacer 22 is a flat plate of the same material as the lens thickness the sum of the thickness t _r and Renzusagu volume of air layer given by Equation (12).

The flat surface 21A of the lens array 2 is parallel to the end surface PL11 of the fiber array 1 and is inclined by 8 degrees with respect to the y-axis. The distance between the oblique flat surface 21A and the lens surface 23 on the lens center axis Ac. There has been set so that concave side focal length f _c.

Partial transmission film 41 and the glass substrate 42: In this configuration, the partial transmission film 41 and the lens array 2 as having separate transparent glass substrate 42 is provided that the same refractive index n _c, are by adhering to BK7 plate . On the glass substrate 42 whose both surfaces are parallel, a partial transmission film 41 having an angle φ is adhered. The reflection / transmission ratio is preferably 95% / 5%, and examples of the material include a SiO ₂ —Ta ₂ O ₅ multilayer film formed by ion beam assisted deposition.

Shading plate 7: The shading plate 7 is made of square infrared absorbing glass. In the central portion, a through hole 71 is formed parallel to the xz plane and having an angle φ between the z-axis direction and the lens center incident direction in accordance with the optical path of the tap light. The x-direction array pitch is 500 μm, which is the same as the lens array 2. The tap light beam propagates without contacting the wall of the through-hole 71 of the light shielding plate 7, but the irregular reflection component due to the structural irregularity generated by the reflection transmission through the lens array 2 or the partial transmission film 41 in the previous stage is blocked by this light shielding. It is blocked by the plate 7 and is prevented from reaching the light receiving element array 8 and causing crosstalk.

As shown in the side view, since the connection interface from the fiber array 1 to the light receiving element array 8 is all kept oblique, it has a structure that prevents reflected return light.

Assembly process: The difference from the seventh embodiment described above is that the lens array 2 and the partial transmission film 41 are first connected in the first process. This is because the partially permeable membrane 41 is just a flat plate, and therefore alignment work is unnecessary, and connection can be made only by mold matching work. Others are the same as those in the seventh embodiment.

Characteristics: The characteristics of the fabricated 4-channel tap monitor module at a wavelength of 1.55 μm were an insertion loss of 0.4 to 0.5 dB, a return loss of 46 dB or more, and a light receiving sensitivity of 50 to 60 mA / W. Adjacent crosstalk was also 45 dB or more.

(Ninth embodiment)
In the above-described embodiment, the array is a one-dimensional array, but a two-dimensional array is also possible. In that case, the fiber array modules shown in FIG. 6 or 18 are arranged in parallel in the y direction.

At that time, the most serious problem is the fiber array. The connection surface seen from the z direction is shown in FIG. The fiber array 1 shown in FIG. 29 includes V-groove plates 13-2 to 13-5 having 60-degree V-grooves 14 for the fiber array. The V-groove plates 13-2 to 13-5 are provided with V-grooves 15-1 and 15-2 for vertical alignment on both sides of the V-groove 14 array. Alignment grooves 15-3 and 15-4 are formed on the back surfaces of the V-groove plates 13-2 to 13-5 at the same position in the x direction as the front surface side. The alignment optical fiber 12 may be the same as the optical fibers 11A and 11B shown in the figure.

In that case, assuming that the opening width of the V-groove 14 is W ₁₄ and the opening width W ₁₅ of the alignment groove 15 is (Equation 18)
W ₁₄ = 2 (R√3-d / √3) (18)
(Equation 19)
W ₁₅ = (2R−d) / √3 (19)
Should be set. Then, when the alignment optical fiber 12 is just fitted into the alignment groove 15, the waveguide optical fiber 11 is pressed by the upper plate by the upper plate. Here, R is the radius of the optical fiber, and d is the distance between the V-groove plates 13-2 to 13-5 and the upper plate.

The alignment grooves 15-1, 15-2, 15-3, and 15-4 must have the same position in the x direction on the front and back of the V-groove plate. In this groove processing apparatus, the perpendicularity of the upper and lower focusing axes of the groove formation position observation lens barrel to the processing surface may be adjusted in advance.

Here, as shown in the side view of FIG. 30, the fiber array 1 is preferably subjected to partial oblique processing only in the vicinity of the optical fiber core. This is because, if the entire surface of the end face of the array is inclined, it is extremely difficult to make all the components after the lens array 2 and subsequent stages into a two-dimensional array. A dual head dicing saw can be used for processing. This is a device that is equipped with two dicing heads in tandem and can be continuously processed using two different blades in one process.

The lens arrays 2 and 9 other than the fiber array 1, the light shielding plate 7, and the light receiving element array 8 are also made into a 2D array, which is a 4 × 4 array. A side view of the produced 4 × 4 tap monitor module is shown in FIG. As for the external appearance, the top view is exactly the same as FIG. 26, and the side view has a form of being stacked in the y direction.

In the description so far, the plane P _C consisting convenience lens optical axis A _C and the fiber optical axis was parallel. However, when the fiber end face is set obliquely as shown in the explanatory diagram of the present disclosure to prevent reflection, in type I, the tilt adjustment around the axis parallel to the x axis is performed between the fiber array 1 and the lens array 2. It is desirable to do.

(Effects of the present disclosure)
As described above, the lens surface is twin-peaked as described in the present disclosure, so that the two peak positions can be divided into the input position and the output position even in the input / output structure offset from the lens center axis. Since it can be optimized for each, high-efficiency optical coupling can be realized. In addition, even if the device is miniaturized and integrated, the lens aperture on the working surface can be kept large, which is suitable for miniaturization. Since it has a plano-convex structure, there is an advantage that it is not necessary to perform front / rear double-sided positioning work such as a biconvex lens and mass production can be easily performed in a single-sided molding process. Since the flat surface 21A side of the plano-convex lens can directly connect front and rear elements, a small optical module can also be configured in this respect. From these facts, it is clear that it contributes greatly to the economics of optical communication devices.

This disclosure can be applied to the information and communication industry.

1, 10: Fiber arrays 11, 11A, 11A-1, 11A-2, 11A-3, 11A-4, 11A-11, 11A-12, 11A-13, 11A-14, 11A-21, 11A-31, 11A-41, 11B, 11B-1, 11B-2, 11B-3, 11B-4, 11B-11, 11B-12, 11B-13, 11B-14, 11B-21, 11B-31, 11B-41: Optical fibers 12-1, 12-2: Positioning optical fibers 13-1, 13-2, 13-3, 13-4, 13-5: V groove plate 14: V grooves 15-1, 15-2, 15-3, 15-4: Alignment grooves 2, 9: Lens array 20: Plano-convex lens 21: Flat substrate 21A: Flat surface 21B: Base surface 22: Spacer 23: Lens surface 3: Air layer 4: Filter unit 41: Partially permeable membrane 42: glass Substrate 7: shielding plate 71: through hole 8: photodetector array 81: light receiving elements 91: the focal length adjusting resin

Claims (8)

1. A plano-convex lens having a flat surface and a lens surface,
   The lens surface includes a first convex surface and a second convex surface having a spherical shape disposed on a flat base surface,
   The diameter of the first virtual circle formed on the base surface by the first convex surface and the diameter of the second virtual circle formed on the base surface by the second convex surface are the first virtual circle and the Greater than the center-to-center distance of the second virtual circle,
   Plano-convex lens.
2. Further comprising a ridge between the first convex surface and the second convex surface to relieve a shape change at a boundary between the first convex surface and the second convex surface,
   The plano-convex lens according to claim 1.
3. The first convex surface and the second convex surface pass through the first straight line passing through the vertex of the first convex surface and the center of the first virtual circle, and the vertex of the second convex surface and the center of the second virtual circle, respectively. The light emitted from the first position and the second position in a predetermined plane including the two straight lines of the second straight line is converted into parallel light,
   When the parallel light incident from the first convex surface is reflected by the reflective surface disposed on the flat surface, the second convex surface condenses the parallel light at the second position;
   The plano-convex lens according to claim 1 or 2.
4. The first convex surface and the second convex surface pass through the first straight line passing through the vertex of the first convex surface and the center of the first virtual circle, and the vertex of the second convex surface and the center of the second virtual circle, respectively. From the first position and the second position, the light incident on the flat surface from the first position and the second position in a predetermined plane including two straight lines of the second straight line is converted into parallel light. The light is emitted so as to be condensed at one point on the reflecting surface perpendicular to the first straight line and the second straight line at a predetermined distance.
   When the parallel light emitted from the first convex surface is reflected at the one point, the second convex surface condenses the parallel light at the second position.
   The plano-convex lens according to claim 1 or 2.
5. A filter portion that transmits a part of the parallel light incident from the first convex surface and reflects a part of the parallel light to the second convex surface is provided on the reflective surface.
   The plano-convex lens according to claim 3 or 4.
6. A first lens array comprising a plurality of plano-convex lenses according to claim 1, wherein a plurality of the first convex surfaces and the second convex surfaces are arranged on the common base surface;
   A fiber array having two optical fibers for each plano-convex lens, and an end face of each optical fiber being disposed at the first position or the second position of each plano-convex lens;
   A fiber array module comprising:
7. The fiber array module according to claim 6,
   A plurality of through-holes that transmit the parallel light transmitted from the reflective surface; each parallel light transmitted from the reflective surface is incident on one end of the different through-hole, and after passing through the through-hole; An optical component that emits parallel light from the other end of each through hole; and
   A second lens array for condensing each light emitted from the other end of the plurality of through holes at a point determined for each through hole;
   A fiber array module comprising:
8. A fiber array module according to claim 7,
   A light receiving element array for receiving each light condensed by the second lens array;
   A light receiving module comprising:

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