JP2006317614A - Light incident/exit part of optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light incident/exit part of an optical device that reduces the number of constituting optical elements and that realizes easy alignment or assembling operation, low cost, simplified manufacturing, etc. <P>SOLUTION: The light incident/exit part of an optical device is constituted of a plurality of waveguides and a single lens, wherein the light incident/exit end face of each waveguide is formed oblique so that the exiting light from each waveguide is made incident on the lens, by transversely propagating the optical axis of the lens and that the optical axis of each propagating light exiting from the lens is made parallel to each other. In addition, the waveguides are constituted of optical fibers, with a ferrule provided holding the optical fibers, and with the ferrule holding all optical fibers, in such a manner that the center axes of all optical fibers are equidistant with respect to the lens optical axis. Also, the light incident/exit end face of all optical fibers is formed oblique at identical tilt angle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light incident / exit section of an optical device.

  An optical circulator is one of important optical devices in fields such as optical communication and optical measurement, and an optical isolator has a two-port configuration on an incident side and an emission side, whereas a non-circulator having at least three or more ports. It is a reciprocal optical device. For example, in the case of having three ports represented by numbers 1, 2, and 3, propagating light traveling in the forward direction 1 → 2, 2 → 3, 3 → 1 has low loss and 2 → 1 in the reverse direction. , 3 → 2, 1 → 3 propagates as high loss output.

  As an example of such an optical circulator, an optical circulator having a structure in which a reflector is arranged at the other end on the light incident / exit side has been devised (for example, see Patent Document 1).

Japanese Unexamined Patent Publication No. 2000-39590 (page 3-5, FIG. 1)

  FIG. 5 is a perspective view showing an example of an optical circulator in which the reflectors are arranged. The optical circulator 100 in FIG. 5 is roughly divided into a main body portion 101, a light incident / exiting portion 102, and a reflecting portion 103. The main body 101 has a configuration in which a first birefringent element 104 and a second birefringent element 105, a 45 degree Faraday rotator 106 and a half-wave plate 107 inserted therebetween are arranged in a line. The crystal axes of the birefringent elements 104 and 105 are set so that the angle with the optical axis is 45 degrees, and the crystal axes of each other are perpendicular to each other when viewed in the optical axis direction. The crystal axis of the half-wave plate 107 is set to ± 22.5 degrees from the horizontal axis when viewed in the optical axis direction, and the polarization plane rotation direction of the Faraday rotator 106 is the port on the left hand side of the drawing (optical fiber 108). ) And set it to 45 degrees counterclockwise.

  The light incident / exit section 102 includes an array of a three-core ferrule 109 having three optical fibers 108, an optical fiber coupling lens 110, and an optical path correction element 111 common to them. The optical path correction element 111 converts the light axis of incident light from the optical fiber 108 through the lens 110 into collimated light or convergent light parallel to the optical axis, and returns light (collimated light or convergent light parallel to the optical axis). Light) enters the optical fiber 102 through the lens 110 and is optically coupled.

  The reflection unit 103 includes a polarization plane rotating element 112 and a mirror (reflector) 113 that rotate the polarization plane of propagating light 90 degrees in a reciprocating manner. As this polarization plane rotation element 112, for example, a quarter wave plate can be applied. When a quarter-wave plate is used, its crystal axis is set to a direction of 45 degrees from the horizontal axis when viewed in the optical axis direction.

  The operation of such an optical circulator 100 will be described below. Light incident from the port 108a is separated into an ordinary ray and an extraordinary ray by the first birefringent element 104, and passes through the Faraday rotator 106 and the half-wave plate 107. At that time, the plane of polarization of extraordinary rays is rotated by 90 degrees, whereas the plane of polarization of ordinary rays does not rotate because the plane of polarization returns to its original state. Next, since it becomes an extraordinary ray with respect to the second birefringent element 105, the propagating light propagates with an optical path shift. The quarter wave plate 112 converts linearly polarized light into circularly polarized light, and the return light reflected by the mirror 113 is converted again into linearly polarized light by the quarter wave plate 112. After all, in the quarter-wave plate 112, the plane of polarization rotates by 90 degrees while the propagating light reciprocates, and becomes an ordinary ray with respect to the second birefringent element 105. Each of the propagating lights is rotated by 90 degrees on the polarization plane by the half-wave plate 107 and the Faraday rotator 106, but the other is not rotated. Then, the first birefringent element 104 combines the ordinary ray and the extraordinary ray into a single propagation light, which is emitted to the center port 108b. The case where the propagation light is propagated from the port 108b to the outer port 108c is exactly the same as the case where the propagation light is propagated from the port 108a to the port 108b.

  On the other hand, even if propagating light enters from the port 108c, it can pass back through the optical path of passing through the main body 101, etc., reflected by the mirror 113, and again passing through the main body 101, etc., but is coupled. There is no port and it does not couple to ports 108a and 108b.

  The light incident / exit section 102 will be further described with reference to FIG. The optical path correction element 111 converts the incident light from the outer optical fiber into oblique propagation light by the lens 110 into collimated light or convergent light having a light axis parallel to the optical axis, and offset of return light. That propagates light (collimated light or convergent light) with a light axis parallel to the optical axis (distant from the optical axis) incident on the lens 110 at an angle and optically couples to the outer optical fiber It is. Further, the incident light from the central optical fiber toward the center of the lens 110 is changed to the propagation light along the optical axis without changing the angle as it is, and the propagation light along the optical axis toward the center of the lens 110 among the return light is also It also has a function of emitting light to a central optical fiber without changing the angle and optically coupling it. The optical path correction element 111 uses a prism that transmits the light on both sides through the inclined surface and transmits the light on the center through the vertical surface.

  In addition, an optical circulator having a structure in which reflectors are arranged at the other end on the incident / exit side has been devised (see, for example, Patent Document 2).

Japanese translation of PCT publication No. 2002-528765 (pages 38-39, FIG. 12)

  An optical circulator 114 of Patent Document 2 shown in FIG. 7 is an optical circulator using a non-row type optical fiber bundle 115 at an input / output side port (light input / output part), and includes two birefringent elements 116a and 116b, Two Faraday rotators 117 and 118 (or a polarization plane rotating element 119) and a reflecting prism 120 as a reflector are provided. The two Faraday rotators 117 and 118 are arranged so that the rotation directions are opposite to each other.

  Further, paying attention to the incident / exit side port, the light axes of the propagating light are made parallel to each other by the two lenses 121 and 122.

  However, each of the light incident / exit portions of the conventional reflection type optical circulator requires two optical elements (the lens 110 and the optical path correction element 111 or the lenses 121 and 122). Even if the size is reduced, the number of constituent elements in the light incident / exit section is increased, making it difficult to achieve a significant reduction in size compared to a transmission type circulator.

  In addition, the increase in the number of constituent elements has complicated the assembly work of the optical circulator and increased the cost. As a result, the entire optical circulator 100 or 114 has become larger in the optical path direction of the propagation light.

  The present invention has been made in view of the above-mentioned problems, and its purpose is to reduce the number of constituent optical elements, facilitate alignment work and assembly work, reduce costs, simplify production, and the like. It is to provide a light incident / exit part of the realized optical device.

The invention according to claim 1 of the present invention comprises a plurality of waveguides and a single lens,
The outgoing light from each waveguide propagates across the optical axis of the lens and enters the lens,
Further, the light incident / exit section of the optical device is characterized in that the light incident / exit end faces of the respective waveguides are formed obliquely so that the light axes of the propagating lights emitted from the lenses are parallel to each other.

  Furthermore, the invention according to claim 2 of the present invention is such that the waveguide is an optical fiber, and further includes a ferrule that holds the optical fiber, and the central axis of all the optical fibers is equal to the optical axis of the lens. In the light incident / exit part of the optical device, all the optical fibers are held by the ferrule so that the distance is maintained, and the light incident / exit end surfaces of all the optical fibers are formed obliquely at the same inclination angle. is there.

  According to the light incident / exit part of the optical device according to the first aspect of the present invention, the light incident / exit part of the optical device can be configured only by the waveguide and the single lens. Therefore, it is possible to reduce the number of constituent elements of the light incident / exit section.

  Furthermore, the number of optical surfaces is reduced as the number of constituent elements is reduced, so that the loss is reduced, the entire optical device is downsized, the light input / output part is assembled, and the optical device is aligned with the constituent elements. Ease of work and cost reduction can be realized.

  Further, by forming the light incident / exit end face of the waveguide obliquely with respect to its central axis, recombination between the return light from the optical device and the waveguide can be prevented, and loss due to the return light can be improved.

  Furthermore, according to the light incident / exit part of the optical device according to claim 2, the light incident / exit end face of each optical fiber is formed obliquely at the same inclination angle, whereby the manufacturing can be simplified.

  Also, by holding each optical fiber with a ferrule so that the central axes of all optical fibers are equidistant with respect to the optical axis of the lens, the light input / output end face of each optical fiber, the optical axis of the lens, Can be set to be equidistant. Thereby, it is possible to set the beam diameter of the light emitted from the lens and incident on the lens 2 to the same size. Therefore, the alignment work between the constituent elements of the light incident / exit section and the constituent elements of the optical device can be further facilitated.

  Hereinafter, a light incident / exit section 1 according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic configuration diagram of the light incident / exit section 1, and FIG. 2 is a configuration diagram of a ferrule 3 for inserting and holding optical fibers P1 to P3. Note that the x-axis to z-axis shown in FIGS. 1 and 2 correspond to each other.

  As shown in FIG. 1, the light incident / exit section 1 includes a plurality of optical fibers P1 to P3 used as waveguides and a single lens 2, and the light incident / exit end faces of the optical fibers P1 to P3. Are formed so as to be non-perpendicular to the central axis fc of each of the optical fibers P1 to P3.

  The optical fibers P1 to P3 are inserted and held in the holes of the three-core ferrule 3. As shown in FIG. 2A, the center from each hole to the center point C of the ferrule 3 is formed at equal intervals. Accordingly, since the center point on the diagonal line connecting the center axes fc of the optical fibers P1 to P3 inserted into the holes comes on the center point C, all the optical fibers P1 to P3 are held by the ferrule 3. Are arranged at equal intervals from the center point C.

  Further, as shown in FIG. 1, the lens 2 and the ferrule 3 are arranged with each other and positioned so that the optical axis oa of the lens 2 and the center point C of the ferrule 3 are on the same straight line in the z-axis direction. . By arranging the lens 2 and the ferrule 3 in this way, the center point of each of the optical fibers P1 to P3 (the center point C) and the optical axis oa of the lens 2 are arranged on the same straight line, and the light of the lens 2 It is held by the ferrule 3 so that the central axes fc of all the optical fibers P1 to P3 are equidistant with respect to the axis oa.

  Further, the light incident / exit end faces of all the optical fibers P1 to P3 are formed obliquely at the same inclination angle φ as shown in FIG. In FIG. 2, in consideration of ease of manufacture, the ferrule 3 end face is formed of four planes so that the center point C is the apex, so that the light incident / exit end faces of the optical fibers P1 to P3 are formed. The example which forms diagonally was given.

  Such a light incident / exit section 1 is applied to an optical device such as an optical circulator 100 instead of the light incident / exit section 102 shown in FIG.

Next, the operation of the light incident / exit section 1 will be described. When light is incident on the optical fiber P1, the light propagates through the optical fiber P1 and is emitted from a light incident / exit end face formed obliquely. At the time of emission, the emitted light is emitted obliquely according to the inclination angle φ, and propagates across the optical axis oa of the lens 2 while the beam diameter expands at a constant spread angle θ≈λ / (πω ₀ ). Then, it is incident on the surface of the lens 2.

  The light incident on the lens 2 is refracted outward from the optical axis oa on the left convex surface of the lens 2 shown in FIG. 1, and is emitted from the lens 2 so that the light axis ba1 is parallel to the z axis. . The emitted light B1 is converted into collimated light or convergent light.

  When the light incident / exit section 1 is applied to the optical circulator 100, the light B1 emitted from the lens 2 passes through each optical element of the optical circulator 100, is reflected by the reflector 113, and enters the lens 2 again. Is done. At this time, the light axis ba2 of the light B2 re-entering the lens 2 is also kept parallel to the z axis. The light B2 is also collimated light or convergent light. In the present invention, the central axis of light is defined by the term “ray axis”.

  The light B2 incident on the lens 2 is refracted inward by the convex curved surface on the right side of the lens 2, and further refracted inward by the convex curved surface on the left side of the lens, and obliquely toward the light incident / exit end surface of the optical fiber P2. The light is emitted from the lens 2.

  The light coupled to the light incident / exit end face of the optical fiber P2 is refracted at the light incident / exit end face and propagates into the optical fiber P2.

  Similarly, the light emitted from the optical fiber P2 propagates across the optical axis oa of the lens 2, enters the lens 2, is emitted as the light B2 from the lens 2, is reflected by the reflector 113, and is reflected by the lens 2. After being re-entered into the optical fiber, it is coupled to the optical fiber P3.

  In addition, since the light incident / exit part 1 of this invention is a reciprocal optical device, it can be said that the reverse of the above-mentioned description regarding the incident / exit of the optical fibers P1 to P3. Accordingly, the light incident / exiting section 1 of the present invention propagates the light emitted from the optical fibers P1 to P3 so as to cross the optical axis oa of the lens 2, enters the lens 2, and further exits from the lens 2. The light incident / exit end faces of the optical fibers P1 to P3 are formed obliquely with a certain inclination angle φ so that the light axes of the propagating light (corresponding to B1 and B2 in FIG. 1) are parallel to each other. . According to the light incident / exiting portion 1 of the present invention, the light incident / exiting portion of the optical device can be basically composed of only a waveguide and a single lens. Therefore, it is possible to form the light incident / exit part by reducing the number of constituent elements as compared with the conventional light incident / exit part.

  Furthermore, the number of optical surfaces is reduced as the number of constituent elements is reduced, so that the loss is reduced, the entire optical device is downsized, and the assembly work and the alignment work with the constituent elements of the optical device are facilitated. In addition, cost reduction can be realized.

  In addition, by forming the light incident / exit end faces of the waveguides (optical fibers P1 to P3) obliquely with respect to the central axis (axis corresponding to fc), the return light from the optical device and the waveguide can be reproduced. Coupling is prevented and loss due to return light is also improved.

  Furthermore, if the light incident / exit end faces of the respective waveguides (optical fibers P1 to P3) are formed obliquely at the same inclination angle φ as in this embodiment, the manufacturing can be simplified.

  Further, by holding the optical fibers P1 to P3 by the ferrule 3 so that the central axes fc of all the optical fibers P1 to P3 are equidistant with respect to the optical axis oa of the lens 2, each of the optical fibers P1 to P3 is held. It is possible to set an equal distance between the light incident / exit end face of the lens 2 and the optical axis oa of the lens 2. As a result, the beam diameters of the light B1 and B2 emitted from the lens 2 and incident on the lens 2 can be set to the same size. Therefore, the alignment work between the constituent elements of the light incident / exit section and the constituent elements of the optical device can be further facilitated.

  The present invention can be variously modified depending on its technical idea. For example, the waveguide (optical fibers P1 to P1) is changed by processing into a conical shape as shown in FIG. 3 instead of the end face shape of the ferrule 3 in FIG. The light incident / exit end face of P3) may be formed obliquely with the same inclination angle φ, or may be formed with three planes according to the number of waveguides and formed obliquely with the same inclination angle φ. Also good. Alternatively, as shown in FIG. 4, the optical fibers P1 to P3 may be protruded from the end face of the ferrule 3, and only the input / output end faces of the optical fibers P1 to P3 may be polished and formed obliquely.

  Further, the inclination angle is formed to be an uneven angle with respect to the center point C, the inclination angle of the light incident / exit end face is changed for each waveguide, and the center point C of the ferrule 3 and the optical axis of the lens 2 are changed. It is also possible to change so that oa is offset.

  The number of waveguides is not limited to three, and may be changed to four or more or less than two.

  Needless to say, the light incident / exit section 1 according to the present invention can be applied not only to an optical circulator but also to other optical devices such as an optical isolator.

  The light incident / exit section of the present invention can be used for optical devices such as an optical circulator and an optical isolator.

The schematic block diagram of the light incident / exit part of this invention. The block diagram of the ferrule which inserts and hold | maintains an optical fiber. The block diagram which shows the example of a change of FIG. The block diagram which shows the other example of a change of FIG. The perspective view which shows the structure of the optical circulator provided with the reflector. The block diagram which shows the light incident / exit part of FIG. The block diagram which shows the other structure of the optical circulator provided with the reflector.

Explanation of symbols

1 Light entrance / exit 2 Lens 3 Ferrule

Claims (2)

Composed of a plurality of waveguides and a single lens,
The outgoing light from each waveguide propagates across the optical axis of the lens and enters the lens,
Further, the light incident / exiting portion of the optical device is characterized in that the light incident / exit end surfaces of the respective waveguides are formed obliquely so that the beam axes of the propagating light emitted from the lens are parallel to each other. The waveguide is an optical fiber, and further includes a ferrule that holds the optical fiber,
All the optical fibers are held by the ferrule so that the central axes of all the optical fibers are equidistant with respect to the optical axis of the lens,
2. The light incident / exit section of an optical device according to claim 1, wherein the light incident / exit end faces of all optical fibers are formed obliquely at the same inclination angle.

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