JP2005227659A - Polarization-independent multicore optical isolator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve deficiency in which an optical isolator array requires time and labor in increasing/changing the number of input/output ports and in which the array is large in size. <P>SOLUTION: In the optical fiber array 2, two pairs of optical fibers 10, 11 and 12, 13 having a mutually parallel optical axis are arranged at equal spaces of 250 (μm) in parallel on the same surface and integrated. Optical fibers 10, 12 on side of each pair constitute an incident optical fiber on which optical signals in a forward direction are made incident. The other optical fibers 11, 13 in each pair constitute an exiting optical fiber from which the optical signals in the forward direction entered from the optical fibers 10, 12 are made to exit. In the optical fiber array 2, the number of optical signal paths can be adjusted, by merely increasing/decreasing the number of pairs of incident and exit light optical fibers, without changing functional components such as a rutile crystal 3, a half-wave plate 5, a focusing rod lens 6, a magnetizing garnet crystal 8 and a total reflection mirror 9. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an in-line polarization-independent optical isolator used for blocking (isolation) transmission of an optical signal in the reverse direction in an optical signal path of an optical communication system, an optical sensor system, etc. The present invention relates to an in-line polarization-independent type multi-fiber optical isolator that integrates the optical isolator functions.

  In general, an inline optical isolator is used in an optical communication system or an optical sensor system to prevent a reflected light signal of a transmitted optical signal from being input to a signal processing unit of an optical transmission apparatus. Usually, since the polarization state of the transmitted optical signal is not constant, a polarization-independent optical isolator is required. When the optical signal path transmits a plurality of optical signals, an array type optical isolator having a plurality of input / output ports is used.

Conventionally, as this type of array type optical isolator, a plurality of one polarization independent optical isolators are gathered and integrated, or a polarization independent optical isolator array disclosed in the following Patent Document 1 is used. is there. In this polarization-independent optical isolator array, in order to block transmission in the reverse direction, a multi-core optical fiber array (FA) equipped with lenses is arranged at an input port and an output port, and two duplex optical fibers are interposed between them. A refractive crystal plate (BP), two Faraday rotators (FR), and a plurality of polarizing plates (PR) are arranged. In this configuration, an input optical signal that propagates in the forward direction from the input optical fiber is emitted from the output optical fiber, but is not incident back into the input optical fiber in the reverse direction (isolation direction).
JP-A-5-188324 (paragraphs [0007] to [0010] and FIGS. 1 and 3)

  However, the conventional optical isolator array in which a plurality of polarization-independent optical isolators are integrated and configured integrally is increased in size by simply collecting the optical isolators. In addition, the conventional optical isolator array disclosed in Patent Document 1 must have a plurality of polarizing plates (PR) arranged vertically according to the number of optical isolator functions, and thus has a function common to a plurality of optical isolators. The functional component parts (BP) and (FR) to be integrated are enlarged. For this reason, the optical isolator array is also large. Further, when the number of input / output ports is increased, it is necessary to replace the polarizing plate (PR) with one according to the number of the additional polarizing plates (PR), and it takes time to change the expansion.

  The present invention has been made in order to solve such problems. An optical fiber having an optical axis parallel to each other and arranged in parallel, an incident optical fiber for receiving a forward optical signal, and a forward optical fiber incident from the incident optical fiber. A spatial displacement is applied to a plurality of pairs of outgoing optical fibers that emit optical signals and an extraordinary ray of the optical signal in a predetermined direction with respect to the crystal optical axis, so that the forward optical signal is converted into an ordinary ray and an extraordinary ray. And a polarization separating element that is separated into a normal beam and an optical axis side of each incident optical fiber or an optical axis side of each outgoing optical fiber, Polarization plane rotating elements that rotate the polarization directions of extraordinary rays in opposite directions, condensing means for converting the condensing state of ordinary and extraordinary rays of an optical signal, and the polarization directions of ordinary and extraordinary rays Constant rotation regardless of propagation direction Non-reciprocal polarization rotator that rotates in the direction of the light, and reflecting means that reflects the ordinary and extraordinary rays of the optical signal emitted from the non-reciprocal polarization rotator and causes the optical signal to enter the non-reciprocal polarization rotator again. Are aligned in this order, and the ordinary ray and extraordinary ray separated by the polarization separation element are rotated by the polarization direction rotation element and the polarization direction rotation element by the non-reciprocal polarization plane rotation element. The angle of the wave direction is the same rotation direction when the ordinary ray and the extraordinary ray are separated by the polarization separation element in the optical axis side portion of the incident optical fiber and propagate in the forward direction, and the angle of the optical axis side portion of the outgoing optical fiber The polarization separating element is subjected to a spatial displacement action that returns to the mutual position where the ordinary ray and extraordinary ray coincide with each other. The polarization separation element is offset so that the opposite rotation direction is canceled and the spatial separation action of the normal ray and the extraordinary ray is further separated by the polarization separation element on the optical axis side portion of the incident optical fiber. , The polarization plane rotating element and the non-reciprocal polarization plane rotating element are arranged mutually, and the crystal optical axis of the polarization separating element is such that the separation direction of the ordinary ray and the extraordinary ray is each light of the pair of the incident optical fiber and the outgoing optical fiber. It is oriented so that it is arranged in a plane perpendicular to the plane including the axis and parallel to each optical axis. An ordinary ray and an extraordinary ray of an optical signal propagating on the optical axis side of the incident optical fiber on the side facing the polarization plane rotation element of the condensing means, and the incident optical fiber Paired outgoing optical fibers A polarization-independent type multi-fiber optical isolator is provided, which is arranged at approximately the same distance from the optical axes of the four rays of the ordinary ray and the extraordinary ray of the optical signal propagating on the optical axis side.

  According to this configuration, the optical signal incident from each incident optical fiber is perpendicular to the plane including the optical axes of the pair of the incident optical fiber and the outgoing optical fiber in the polarization separating element. The optical axes of the ordinary ray and the extraordinary ray are separated from each other in a direction parallel to each optical axis, and the optical axis of the ordinary ray and the extraordinary ray is substantially parallel to the converging center optical axis of the condensing unit. And located at approximately the same distance from the focusing center optical axis. In addition, these ordinary rays and extraordinary rays of the reflected light signal reflected by the reflecting means are also focused on the side opposite to the polarization plane rotating element of the condensing means, with each optical axis being substantially parallel to the focusing center optical axis. Located at substantially the same distance from the central optical axis, the polarization beam splitting element is recombined in a direction perpendicular to the plane including the optical axes of the pair of the incident optical fiber and the outgoing optical fiber and parallel to the optical axes.

  For this reason, it is possible to make incidents without changing functional components such as a polarization separating element, a polarization plane rotating element, a condensing unit, a non-reciprocal polarization plane rotating element, and a reflecting unit that perform a function common to a plurality of optical isolators. The number of optical signal paths can be adjusted simply by increasing or decreasing the number of pairs of optical fibers and outgoing optical fibers. Therefore, even if an optical signal path is added, the functional components do not increase in size, and there is no need to replace the functional components when adding an optical signal path. An array is provided. In addition, there is almost no difference in the optical path lengths of the ordinary ray and the extraordinary ray propagating to the polarization separation element where recombination is performed between the pair of incident optical fibers and the outgoing optical fiber, and almost no occurrence of polarization mode dispersion occurs. No. Therefore, there is almost no difference in the time required for propagation of ordinary rays and extraordinary rays to the polarization separation element, and when this polarization-independent multi-fiber optical isolator is applied in a high-speed optical transmission device, There are no restrictions.

  Further, according to the present invention, a plurality of pairs of incident optical fibers and outgoing optical fibers are integrated as an optical fiber array, and an end surface of the optical fiber array includes a plane including each optical axis of the pair of incident optical fibers and outgoing optical fibers. The light input / output end faces of the polarization splitting element and the polarization plane rotating element, and the end face facing the polarization plane rotating element of the condensing means Is substantially parallel to the end face of the optical fiber array.

  According to this configuration, the optical signal incident from each incident optical fiber is perpendicularly incident on the end face of the polarization separation element, and the ordinary ray and the extraordinary ray separated by the polarization separation element The light propagates in a direction perpendicular to each light input / output end face of the wavefront rotating element and an end face facing the polarization plane rotating element of the condensing means. Further, the reflected signal reflected by the reflecting means also propagates in the direction perpendicular to the light input / output end faces of the end face facing the polarization plane rotation element of the light collecting means, the polarization plane rotation element, and the polarization separation element.

  Further, according to the present invention, a plurality of pairs of an incident optical fiber and an outgoing optical fiber are integrated as an optical fiber array, and the end face of the optical fiber array is in any optical axis of the incident optical fiber and the outgoing optical fiber. The surface that is inclined by a predetermined angle with respect to the vertical plane and that faces the optical fiber array of the light collecting means is substantially parallel to the end surface of the optical fiber array, and is perpendicular to the converging center optical axis of the light collecting means. The optical input / output end faces of the polarization separation element and the polarization plane rotation element are inclined and aligned in accordance with the inclination of the end face of the optical fiber array.

  According to this configuration, the optical signal incident from each incident optical fiber and the reflected optical signal obtained by reflecting the incident optical signal by the reflecting means are transmitted to the optical input / output end surfaces of the polarization separation element and the polarization plane rotating element, and to the collection. Reflected light generated by reflection at the end face facing the polarization plane rotation element of the optical means does not return to the original direction, and is not incident on the original incident optical fiber. For this reason, the influence of the reflected light generated by the reflection of the optical signal incident from each incident optical fiber and the reflected optical signal of the incident optical signal reflected by the reflecting means on each end face is reduced. Accordingly, unintended reflected light is less likely to be input to the optical device connected to each incident optical fiber and each outgoing optical fiber, and the reflected light becomes noise of the optical device when propagating in the forward direction. No longer.

  Further, according to the present invention, one of an optical signal propagating on the optical axis side of each incident optical fiber or an optical signal propagating on the optical axis side of each outgoing optical fiber is between the polarization separating element and the condensing means. A polarization plane rotation element is disposed at a position where the light passes, and an amorphous optical element is disposed at a position where the other light passes.

  According to this configuration, the polarization direction of the optical signal incident from each incident optical fiber is rotated by a predetermined angle by the polarization plane rotation element immediately after the ordinary ray and the extraordinary ray are separated by the polarization separation element. Alternatively, after being separated by the polarization separation element and reflected by the reflecting means, the polarization direction is rotated by a predetermined angle by the polarization plane rotation element. For this reason, even if the positions of the polarization plane rotating element and the amorphous optical element are switched, the effect on the optical signal is not changed, and these positions can be switched.

  Further, the present invention is characterized in that a heat insulating means is provided between the light collecting means and the non-reciprocal polarization plane rotating element.

  According to this configuration, even if the iron component of the nonreciprocal polarization rotator absorbs an optical signal having a predetermined wavelength and generates heat, the heat is collected by the heat insulating means adjacent to the nonreciprocal polarization rotator. It is no longer conducted to the light means. For this reason, there is no problem that the adhesive that adheres between the non-reciprocal polarization plane rotating element and the condensing means adjacent to the non-reciprocal polarization plane rotating element is deteriorated and deteriorated due to the temperature rise of the heat generation.

  Further, the present invention is characterized in that the reflecting means is formed by directly processing the surface opposite to the surface facing the light converging means of the non-reciprocal polarization plane rotating element.

  According to this configuration, the surface of the nonreciprocal polarization plane rotation element opposite to the surface facing the light condensing unit functions as the reflecting unit as it is. For this reason, it is not necessary to newly provide a separate reflecting means adjacent to the non-reciprocal polarization plane rotation element, and the polarization-independent type multi-core optical isolator can be configured compactly.

  Further, the present invention is characterized in that the nonreciprocal polarization plane rotation element is magnetized in advance.

  According to this configuration, the polarization direction of the optical signal passing through the nonreciprocal polarization plane rotating element can be rotated by the magnetic field of the nonreciprocal polarization plane rotating element. For this reason, it is not necessary to provide a device for applying a magnetic field to the non-reciprocal polarization plane rotation element from the outside, and the polarization-independent type multi-core optical isolator can be configured compactly.

  Further, according to the present invention, the optical fiber array is configured such that each incident optical fiber and each output optical fiber are inserted into capillaries opened in the array body, or each V groove formed in parallel in the array body. An incident optical fiber and outgoing optical fibers are mounted and fixed.

  According to this configuration, the polarization-independent multi-core optical isolator is connected to the plurality of optical fibers constituting the optical signal path and the optical fibers aligned with the capillaries or V grooves of the array body. . Therefore, the polarization-independent type multi-fiber optical isolator can be easily connected to a plurality of optical fibers. In addition, a polarization-independent multi-fiber optical isolator with a different number of input / output ports can be easily configured simply by exchanging with another optical fiber array with a different number of cores.

  According to the polarization-independent multi-core optical isolator according to the present invention, as described above, the configuration of the optical fiber pair is only changed without changing the functional components that exhibit the functions common to the plurality of optical isolators. Therefore, it is possible to provide a polarization-independent type multi-fiber optical isolator that can adjust the number of optical signal paths, is small, and does not require time and effort to add and change optical signal paths.

  Next, the best mode for carrying out the present invention will be described.

  FIG. 1A is a plan view of a polarization-independent multi-fiber optical isolator 1 according to a first embodiment in which the present invention is applied to an optical fiber communication system, and FIG. 1B is a side view thereof. The polarization-independent multi-core optical isolator 1 includes an optical fiber array 2, a rutile crystal 3, a quartz glass plate 4, a half-wave plate 5, a focusing rod lens 6, a gap 7, a magnetized garnet crystal 8, and a total reflection mirror 9. Are arranged in this order.

  In the optical fiber array 2, two pairs of optical fibers 10 and 11 and optical fibers 12 and 13 whose optical axes are parallel to each other are arranged in parallel at equal intervals of 250 [μm] on the same plane and integrated. One optical fiber 10 and 12 of each pair constitutes an incident optical fiber for receiving a forward optical signal, and the other optical fibers 11 and 13 of each pair are in the order of incidence from the optical fibers 10 and 12. An outgoing optical fiber that emits an optical signal in the direction is configured. Each end 10a, 11a, 12a and 13a of the optical fibers 10, 11, 12 and 13 is fixed by a multi-core or single-core ferrule (not shown), and an optical signal path made of an optical fiber via the optical fiber array 2 It is connected to the. The other ends 10 b, 11 b, 12 b and 13 b of the optical fibers 10, 11, 12 and 13 are arranged on the end surface 2 a of the optical fiber array 2. This end face 2a is formed by being polished perpendicularly to the plane including the optical axis of each of the optical fibers 10 to 13 and perpendicularly to any optical axis. In addition, the light input / output end faces 3a, 3b, 4a, 4b, 5a, 5b of the half-wave plate 5 and the end face 6a facing the quartz glass plate 4 and the half-wave plate 5 of the focusing rod lens 6 are respectively on the end face 2a. They are arranged almost in parallel.

  The rutile crystal 3 is a birefringent crystal having a thickness of 300 [μm] and constitutes a polarization separation element that separates the optical signal A and the optical signal B incident from the forward direction into the ordinary ray O and the extraordinary ray E, respectively. doing. The rutile crystal 3 causes a spatial displacement 3d to act on the ordinary ray O or extraordinary ray E of the optical signal A and the optical signal B having polarization in a direction parallel to the crystal optical axis 3c. The crystal optical axis 3c of the rutile crystal 3 is such that the separation direction of the ordinary ray O and the extraordinary ray E is perpendicular to the plane including each optical axis of the optical fibers 10-13 and parallel to each optical axis of the optical fibers 10-13. Oriented to be placed in-plane.

  Between the rutile crystal 3 and the converging rod lens 6, the ordinary light beam O and the normal light beam O and the light signal B incident from the optical fibers 10 and 12 pass through the forward or reverse propagation direction. A half-wave plate 5, which is a polarization plane rotation element that rotates the polarization direction of the extraordinary ray E in the reverse direction, is disposed. Further, a quartz glass plate 4 that is an amorphous optical element is disposed at a position where the reflected light signal A and the reflected light signal B reflected by the total reflection mirror 9 pass. In the forward movement, the quartz glass plate 4 passes only the optical signal A and the optical signal B incident from the input optical fibers 10 and 12 through the half-wave plate 5 and is reflected from the total reflection mirror 9. And the half-wave plate 5 is arranged in parallel so that only the reflected light signal B passes. The optical axis of the half-wave plate 5 is oriented at an angle of 22.5 ° counterclockwise with respect to the polarization direction of the ordinary ray O that is separated and travels in the forward direction. When A and the optical signal B propagate in the forward direction indicated by the arrow (a) in the figure, the polarization directions of the ordinary ray O and the extraordinary ray E are respectively rotated by 45 ° counterclockwise, and the optical signal A and the optical signal are transmitted. When B propagates in the reverse direction indicated by an arrow in FIG. 3A to be described later, the polarization directions of the ordinary ray O and the extraordinary ray E are respectively rotated by 45 ° in the clockwise direction.

  The converging rod lens 6 is composed of a gradient index rod lens having a phase difference of about π / 2, and constitutes a condensing unit that converts the condensing state of the ordinary ray O and the extraordinary ray E. When the ordinary ray O and the extraordinary ray E propagate in the forward direction, the converging rod lens 6 converts these rays O and E into parallel rays and then condenses them to propagate in the opposite direction. In some cases, on the side of the end face 6a, these light rays O and E are converted into parallel light rays and away. The converging center optical axis 6c of the converging rod lens 6 is parallel to the optical axes of the optical fibers 10 to 13 and is perpendicular to a plane including the optical axes of the optical fibers 10 to 13, and the optical fibers 10 to 10. It arrange | positions on the plane containing the centerline 2c between each 13 optical axes. Further, the converging center optical axis 6c has an ordinary ray O and an extraordinary ray E propagating on the optical axis side of one optical fiber 10 in the pair, and an optical axis side of the other optical fiber 11 in the pair on the end face 6a side. From the four rays of the ordinary ray O and the extraordinary ray E propagating in FIG. Further, the ordinary ray O and extraordinary ray E propagating on the optical axis side of one optical fiber 12 of the other pair, and the ordinary ray O and extraordinary ray propagating on the optical axis side of the other optical fiber 13 of the other pair. Also from the four light beams E, they are arranged at approximately equal distances.

  The magnetized garnet crystal 8 is pre-magnetized in this embodiment, and the polarization directions of the ordinary ray O and the extraordinary ray E are always 22.5 ° in a constant counterclockwise direction regardless of the propagation direction. A rotating non-reciprocal polarization plane rotating element is configured. Further, a gap 7 of about 200 [μm] is provided as a heat insulating means between the converging rod lens 6 and the magnetized garnet crystal 8. The total reflection mirror 9 is formed by vapor-depositing a surface of the magnetized garnet crystal 8 opposite to the surface facing the converging rod lens 6. The total reflection mirror 9 reflects the ordinary ray O and the extraordinary ray E of the optical signal emitted from the magnetized garnet crystal 8 into a reflected light signal, and reflects the reflected light signal into the magnetized garnet crystal 8 again. Is configured.

  Next, an operation in the case where the optical signal A and the optical signal B having a wavelength of 1.55 [μm] propagate through the polarization-independent multi-core optical isolator 1 in the forward direction in the above configuration will be described. In FIG. 1 described above, an optical signal path when the optical signal A is incident in the forward direction from the optical fiber 10 and an optical signal path when the optical signal B is incident in the forward direction from the optical fiber 12 are shown. ing. 2A to 2I show the ordinary ray O and the extraordinary ray E of the optical signal A at the positions FA, FB, FC, FD, FE, FF, FG, FH, and FJ shown in FIG. (J) to (r) show the polarization state and the arrangement relationship of the ordinary ray O and the extraordinary ray E of the optical signal B at each of these positions. It is shown. FIG. 2 is displayed with the rutile crystal 3 side viewed from the optical fiber array 2 side in FIG. 1, and the directions perpendicular to the paper surface are the optical axis directions of the optical fibers 10 to 13. In the figure, a dotted line drawn horizontally represents a plane including the optical axes of the optical fibers 10 to 13, and a one-dot chain line drawn vertically passes through the center line 2 c of the optical fiber array 2 and passes through the optical fiber. A plane perpendicular to a plane including 10 to 13 optical axes is shown. This plane includes the converging center optical axis 6 c of the converging rod lens 6.

  The optical signal A incident in the forward direction from the other end 10 b of the optical fiber 10 is first incident perpendicularly on the end face 3 a of the rutile crystal 3. FIG. 2A shows the polarization state and arrangement relationship of the optical signal A at this time, and the ordinary ray O and the extraordinary ray E are orthogonal to each other. As described above, since the crystal optical axis 3c of the rutile crystal 3 is oriented in a direction perpendicular to the plane including the optical axes of the optical fibers 10 to 13, the optical signal A passes through the rutile crystal 3. An extraordinary ray E having a polarization in a direction parallel to the crystal optical axis 3c receives a spatial displacement 3d from an ordinary ray O having a polarization in a direction perpendicular to the crystal optical axis 3c, and the ordinary ray O and the extraordinary ray E are 2 (b), the optical fibers 10 to 13 are separated in a direction perpendicular to the plane including the optical axes.

  The separated ordinary ray O and extraordinary ray E are perpendicularly incident on the end face 5 a of the half-wave plate 5. At this time, as described above, the optical axis of the half-wave plate 5 is oriented at an angle of 22.5 ° counterclockwise with respect to the polarization direction of the ordinary ray O in the state shown in FIG. Therefore, the polarization directions of the ordinary ray O and the extraordinary ray E are each rotated by 45 ° in the counterclockwise direction, as shown in FIG.

  The ordinary ray O and extraordinary ray E that have passed through the half-wave plate 5 are then incident perpendicularly on the end face 6 a of the converging rod lens 6. At this time, the ordinary ray O and the extraordinary ray E are parallel to the plane including the optical axes of the optical fibers 10 to 13 and the plane including the converging center optical axis 6c of the converging rod lens 6 is changed into the ordinary ray O and the extraordinary ray E. Are incident on the positions sandwiched between the top and bottom at substantially equal intervals. At this time, the ordinary ray O and the extraordinary ray E are substantially equidistant from the focusing center optical axis 6c. The ordinary ray O and the extraordinary ray E are converted into parallel rays in the converging rod lens 6, approaching each other as they travel and approaching the converging center optical axis 6 c, and from the lens end face at an exit angle of about 1 °. Emitted. The state of the ordinary ray O and the extraordinary ray E at this time is shown in FIG.

  The ordinary ray O and extraordinary ray E emitted from the lens end face of the converging rod lens 6 are then incident on the magnetized garnet crystal 8 through the gap 7 of about 200 [μm]. The polarization direction of the ordinary ray O and the extraordinary ray E is rotated by 22.5 ° counterclockwise by the magnetized garnet crystal 8. Next, the optical signal A from the magnetized garnet crystal 8 is reflected by the total reflection mirror 9. On the total reflection mirror 9, the positions of the ordinary ray O and the extraordinary ray E are shown in FIG. As shown, they are almost identical.

  Next, the ordinary ray O and the extraordinary ray E reflected by the total reflection mirror 9 are incident on the magnetized garnet crystal 8 again, and are further rotated by 22.5 ° counterclockwise by the magnetized garnet crystal 8. By reciprocating through the magnetized garnet crystal 8, the light beams O and E have their polarization directions rotated 45 ° counterclockwise, and the half-wave plate 5 rotates 45 °. Together, this results in a 90 ° counterclockwise rotation. This state is shown in FIG.

  Further, due to reflection by the total reflection mirror 9, an ordinary ray O and an extraordinary ray E are passed in a plane perpendicular to a plane passing through the converging center optical axis 6 c of the converging rod lens 6 and including the optical axes of the optical fibers 10 to 13. Although the physical positions are interchanged, the polarization states of each remain the same as before reflection. Further, in a plane parallel to the plane including the optical axes of the optical fibers 10 to 13, the ordinary ray O and the extraordinary ray E are emitted from the optical fiber 10 side across the focusing center optical axis 6 c of the focusing rod lens 6. The spatial position is switched to the fiber 11 side.

  Next, the ordinary ray O and the extraordinary ray E emitted from the magnetized garnet crystal 8 pass through the gap 7 of about 200 [μm] and enter the converging rod lens 6. Due to the effect of the converging rod lens 6, the ordinary ray O and the extraordinary ray E are converted into parallel rays, separated from each other as they travel, and away from the converging center optical axis 6c. The state at this time is shown in FIG. Subsequently, the ordinary ray O and the extraordinary ray E pass through the quartz glass plate 4, but the polarization direction of each ray is not affected. The state at this time is shown in FIG.

  Next, the ordinary ray O and the extraordinary ray E are perpendicularly incident on the end face 3 b of the rutile crystal 3. In the rutile crystal 3, the ordinary ray O is subjected to a spatial displacement action because its polarization direction is rotated by 90 ° and has a polarization in a direction parallel to the crystal optical axis 3 c of the rutile crystal 3. . However, since the polarization direction of the extraordinary ray E is rotated by 90 ° and has a polarization in a direction perpendicular to the crystal optical axis 3c of the rutile crystal 3, the extraordinary ray E passes through without being subjected to a spatial displacement action. . Therefore, the ordinary ray O that has undergone the spatial displacement is recombined with the extraordinary ray E as shown in FIG. The recombined ordinary ray O and extraordinary ray E enter the optical fiber 11 and are transmitted to an external optical signal path as a forward output optical signal.

  Further, the optical signal B incident in the forward direction from the other end 12b of the optical fiber 12 propagates along the same path as the optical signal A outside the optical signal A, as shown in FIGS. To do. That is, the optical signal B first enters the end face 3a of the rutile crystal 3 perpendicularly. FIG. 2 (j) shows the polarization state and arrangement relationship of the optical signal B at this time, and the ordinary ray O and the extraordinary ray E are orthogonal to each other. As shown in FIG. 2 (k), the ordinary ray O and the extraordinary ray E are separated in a direction perpendicular to the plane including the optical axes of the optical fibers 10 to 13 in the rutile crystal 3, and then, FIG. As shown in (l), each half-wave plate 5 is rotated 45 ° counterclockwise. Subsequently, the ordinary ray O and the extraordinary ray E that have entered the converging rod lens 6 are converted and emitted from the lens end face as shown in FIG. Then, after passing through the gap 7, it enters the magnetized garnet crystal 8, and the polarization direction is rotated 22.5 ° counterclockwise. Subsequently, the ordinary ray O and the extraordinary ray E are reflected by the total reflection mirror 9. As shown in FIG. 2 (n), the positions of the ordinary ray O and the extraordinary ray E substantially coincide on the total reflection mirror 9.

  Next, the ordinary ray O and the extraordinary ray E reflected by the total reflection mirror 9 are further rotated by 22.5 ° counterclockwise by the magnetized garnet crystal 8 again. This state is shown in FIG. Subsequently, after passing through the gap 7, the ordinary ray O and the extraordinary ray E are converted as shown in FIG. 2 (p) due to the effect of the converging rod lens 6. Thereafter, it passes through the quartz glass plate 4, but the polarization direction of each light beam is not affected. The state at this time is shown in FIG. Thereafter, in the rutile crystal 3, the ordinary ray O is subjected to a spatial displacement action by the rutile crystal 3, but the extraordinary ray E passes through without being subjected to the spatial displacement action. Therefore, as shown in FIG. Ray O and extraordinary ray E recombine. The recombined ordinary ray O and extraordinary ray E enter the optical fiber 13 and are transmitted to the external optical signal path as a forward output optical signal.

  Next, an operation when the optical signal A and the optical signal B having a wavelength of 1.55 [μm] propagate through the polarization-independent multi-core optical isolator 1 in the reverse direction will be described. FIG. 3 shows an optical signal path when the optical signal A is incident in the reverse direction from the optical fiber 11 and an optical signal path when the optical signal B is incident in the reverse direction from the optical fiber 13. 1A is a plan view of the polarization-independent type multi-core optical isolator 1, and FIG. 1B is a side view thereof. In the figure, the same parts as those in FIG. 4A to 4I show the ordinary ray O and the extraordinary ray E of the optical signal A at the positions BA, BB, BC, BD, BE, BF, BG, BH, BJ shown in FIG. (J) to (r) show the polarization state and the arrangement relationship of the ordinary ray O and the extraordinary ray E of the optical signal B at each of these positions. It is shown. 4 is displayed in a state in which the rutile crystal 3 side is viewed from the optical fiber array 2 side as in FIG. 2 described above, and the directions perpendicular to the paper surface are the respective optical axis directions of the optical fibers 10 to 13. ing. Also in this figure, the dotted line drawn horizontally is a plane including the optical axes of the optical fibers 10 to 13, and the alternate long and short dash line passes through the center line 2 c of the optical fiber array 2 and passes through the optical fiber 10. The plane perpendicular | vertical to the plane containing each optical axis of -13 is shown. This plane includes the converging center optical axis 6 c of the converging rod lens 6.

  As shown in FIG. 3, the optical signal A having a wavelength of 1.55 [μm] is incident in the opposite direction from the other end 11 b of the optical fiber 11, and is first incident perpendicularly on the end face 3 a of the rutile crystal 3. The state at this time is shown in FIG. 4A, and the ordinary ray O and the extraordinary ray E are orthogonal to each other. As described above, the optical signal A incident on the rutile crystal 3 has an extraordinary ray E having a polarization in a direction parallel to the crystal optical axis 3c in the rutile crystal 3, as shown in FIG. Upon receiving a spatial displacement 3d from an ordinary ray O having a polarization in a direction perpendicular to the crystal optical axis 3c, the ordinary ray O and the extraordinary ray E are perpendicular to the plane including the optical axes of the optical fibers 10 to 13. Separated in direction. Subsequently, the separated ordinary ray O and extraordinary ray E pass through the quartz glass plate 4, but the polarization directions of the ordinary ray O and extraordinary ray E are not affected and do not rotate. The state at this time is shown in FIG.

  Next, the ordinary ray O and the extraordinary ray E emitted from the quartz glass plate 4 are perpendicularly incident on the end surface 6 a of the converging rod lens 6. At that time, the ordinary ray O and the extraordinary ray E sandwich a plane parallel to the plane including the optical axes of the optical fibers 10 to 13 and including the converging center optical axis 6c of the converging rod lens 6 from above and below at substantially equal intervals. Incident on the position. At this time, the ordinary ray O and the extraordinary ray E are at substantially equal distances from the converging center optical axis 6 c of the converging rod lens 6. The ordinary ray O and the extraordinary ray E are converted into parallel rays in the converging rod lens 6, approaching each other as they travel and approaching the converging center optical axis 6 c, and from the lens end face at an exit angle of about 1 °. Emitted. The state of the ordinary ray O and the extraordinary ray E at this time is shown in FIG.

  The ordinary ray O and the extraordinary ray E emitted from the lens end face of the converging rod lens 6 pass through the gap 7 of about 200 [μm] and enter the magnetized garnet crystal 8. The incident ordinary ray O and extraordinary ray E are rotated by 22.5 ° in the counterclockwise direction by the magnetized garnet crystal 8. Next, the optical signal A from the magnetized garnet crystal 8 is reflected by the total reflection mirror 9. On this total reflection mirror 9, the positions of the ordinary ray O and the extraordinary ray E are shown in FIG. 4 (e). And so on. The ordinary ray O and the extraordinary ray E reflected by the total reflection mirror 9 become a reflected light signal A and enter the magnetized garnet crystal 8 again, and the magnetized garnet crystal 8 further counterclockwise 22.5 °. It is rotated. By passing back and forth through the magnetized garnet crystal 8, as a result, the polarization directions of the light beams O and E are rotated 45 ° counterclockwise. The state at this time is shown in FIG.

  Further, due to reflection by the total reflection mirror 9, an ordinary ray O and an extraordinary ray E are passed in a plane perpendicular to a plane passing through the converging center optical axis 6 c of the converging rod lens 6 and including the optical axes of the optical fibers 10 to 13. Although the physical positions are interchanged, the polarization states of each remain the same as before reflection. Further, in a plane parallel to the plane including the optical axes of the optical fibers 10 to 13, the ordinary ray O and the extraordinary ray E are emitted from the optical fiber 11 side across the focusing center optical axis 6 c of the focusing rod lens 6. The spatial position is switched to the fiber 10 side.

  Next, the ordinary ray O and the extraordinary ray E emitted from the magnetized garnet crystal 8 pass through the gap 7 of about 200 [μm] and enter the converging rod lens 6. The ordinary ray O and the extraordinary ray E are converted into parallel rays by the effect of the converging rod lens 6, and are separated from each other as they travel and away from the converging center optical axis 6 c. The state at this time is shown in FIG.

  Subsequently, the separated ordinary ray O and extraordinary ray E are perpendicularly incident on the end face 5b of the half-wave plate 5. The half-wave plate 5 is polarized by the ordinary ray O in the state shown in FIG. Since the optical axis is oriented at an angle of −22.5 ° with respect to the direction, the polarization directions of the ordinary ray O and the extraordinary ray E are rotated by −45 ° in the counterclockwise direction. As a result, the angle −45 ° of the polarization direction rotated by the half-wave plate 5 and the angle 45 ° of the polarization direction rotated by the magnetized garnet crystal 8 cancel each other, and the ordinary ray O and the extraordinary ray E The total rotation angle in the polarization direction is 0 °. This state is shown in FIG.

  The ordinary ray O and extraordinary ray E that have passed through the half-wave plate 5 are then incident perpendicularly on the end face 3 b of the rutile crystal 3. At this time, since the ordinary ray O is in a state of having a polarization in a direction perpendicular to the crystal optical axis 3c of the rutile crystal 3, it passes through without being subjected to a spatial displacement action. Further, the extraordinary ray E has a polarization in a direction parallel to the crystal optical axis 3c of the rutile crystal 3, and therefore undergoes a spatial displacement action away from the ordinary ray O as shown in FIG. As a result, the ordinary ray O and the extraordinary ray E are not recombined, and both are not incident on the optical fiber 10 because they are shifted from the optical fiber 10 by about 30 [μm]. For this reason, the isolation of the reverse direction about the optical signal A is implement | achieved.

  Further, the optical signal B incident in the reverse direction from the other end 13b of the optical fiber 13 propagates along the same path as the optical signal A outside the optical signal A, as shown in FIGS. To do. That is, the optical signal B first enters the end face 3a of the rutile crystal 3 perpendicularly. FIG. 4 (j) shows the polarization state and arrangement relationship of the optical signal B at this time, and the ordinary ray O and the extraordinary ray E are orthogonal to each other. The ordinary ray O and the extraordinary ray E are separated in the direction perpendicular to the plane including the optical axes of the optical fibers 10 to 13 in the rutile crystal 3 as shown in FIG. As shown in FIG. 4 (l), the separated ordinary ray O and extraordinary ray E pass through the quartz glass plate 4 in a state in which the polarization direction does not rotate, and then, by the converging rod lens 6, the convergent rod lens 6 causes FIG. ). Subsequently, after passing through the gap 7, the ordinary ray O and the extraordinary ray E are reflected by the total reflection mirror 9 after the polarization direction is rotated by 22.5 ° counterclockwise by the magnetized garnet crystal 8. As shown in FIG. 4 (n), the positions of the ordinary ray O and the extraordinary ray E substantially coincide on the total reflection mirror 9.

  Next, the ordinary ray O and the extraordinary ray E reflected by the total reflection mirror 9 are further rotated by 22.5 ° counterclockwise by the magnetized garnet crystal 8 again. This state is shown in FIG. Subsequently, the ordinary ray O and the extraordinary ray E pass through the gap 7 and are converted as shown in FIG. 4 (p) by the effect of the converging rod lens 6. Thereafter, as shown in FIG. 4 (q), the ordinary ray O and the extraordinary ray E are rotated by −45 ° counterclockwise by the half-wave plate 5, respectively. Thereafter, the ordinary ray O passes through the rutile crystal 3 without being subjected to the spatial displacement action. However, since the extraordinary ray E is subject to the spatial displacement action by the rutile crystal 3, as shown in FIG. The light beam O and the extraordinary light beam E are not recombined and are not incident on the optical fiber 12. For this reason, the isolation of the reverse direction about the optical signal B is implement | achieved.

  According to the polarization independent multi-fiber optical isolator 1 according to the first embodiment of the present invention, as described above, the optical signal A and the optical signal B emitted in the forward direction from the optical fibers 10 to 13 are provided. In the rutile crystal 3, the ordinary ray O and the extraordinary ray E are perpendicular to the plane including the optical axes of the two pairs of optical fibers 10 and 11 and the optical fibers 12 and 13, and are parallel to these optical axes. Separated. Further, on the end face 6a of the converging rod lens 6, the optical axes of the ordinary ray O and the extraordinary ray E are substantially parallel to the converging center optical axis 6c of the converging rod lens 6, and from the converging center optical axis 6c. Located approximately equidistant. Further, the ordinary ray O and the extraordinary ray E of the reflected light signal reflected by the total reflection mirror 9 also have their optical axes substantially parallel to the converging center optical axis 6c on the end face 6a of the converging rod lens 6. Located substantially equidistant from the focusing center optical axis 6c, the rutile crystal 3 is perpendicular to a plane including the optical axes of the two pairs of optical fibers 10 and 11 and the optical fibers 12 and 13, and is parallel to these optical axes. Recombine in any direction. Therefore, functional components such as a rutile crystal 3, a half-wave plate 5, a converging rod lens 6, a magnetized garnet crystal 8, and a total reflection mirror 9 that exhibit functions common to a plurality of optical isolators are changed. In addition, the number of optical signal paths can be adjusted simply by increasing or decreasing the number of pairs of incident optical fibers and outgoing optical fibers. Therefore, even if an optical signal path is added, the functional components do not increase in size, and there is no need to replace the functional components when adding an optical signal path. An array 1 is provided. Also, an ordinary ray O and anomaly that propagates to the rutile crystal 3 where recombination is performed between the optical fiber 10 and the optical fiber 11 of one pair and between the optical fiber 12 and the optical fiber 13 of the other pair. There is almost no difference in the optical path length of the light E, and there is almost no occurrence of polarization mode dispersion. Accordingly, the difference in time required for propagation of the ordinary ray O and the extraordinary ray E to the rutile crystal 3 is almost 0.01 [psec] or less, and there is almost no difference in the high-speed optical transmission apparatus of 10 [Gb / s] or more. When this polarization-independent type multi-fiber optical isolator 1 is applied, there is no limitation on the number of the use.

  Further, in the above embodiment, even if the positions of the half-wave plate 5 and the quartz glass plate 4 are switched, the effect on the optical signal is not changed, and these positions can be switched. That is, the half-wave plate 5 is located between the rutile crystal 3 and the converging rod lens 6 at a position where one of the incident optical signal A and optical signal B or reflected reflected optical signal A and reflected optical signal B passes. The quartz glass plate 4 should just be arrange | positioned in the position where it arrange | positions and the other passes. In any arrangement, the optical signal A incident from the optical fiber 10 and the optical signal B incident from the optical fiber 12 are polarized immediately after the ordinary ray O and the extraordinary ray E are separated by the rutile crystal 3. The direction is rotated by 45 ° by the half-wave plate 5, or after being separated by the rutile crystal 3 and reflected by the total reflection mirror 9, the polarization direction is rotated by 45 ° by the half-wave plate 5.

  In the above embodiment, since the gap 7 of about 200 [μm] is provided between the converging rod lens 6 and the magnetized garnet crystal 8, the iron component of the magnetized garnet crystal 8 has a wavelength of 0. Even when .98 [μm] light is absorbed and heat is generated, the heat is less likely to be conducted to the converging rod lens 6 adjacent to the magnetized garnet crystal 8 due to the gap 7. For this reason, the adhesive or the like that bonds the magnetized garnet crystal 8 and the converging rod lens 6 adjacent to the magnetized garnet crystal is not deteriorated and deteriorated due to a rise in temperature of heat generation, so that a characteristic change does not occur. When light of 100 [mW] was actually irradiated for 24 hours at a wavelength of 0.98 [μm], it was confirmed that there was no change in characteristics before and after irradiation.

  In the above embodiment, since the total reflection mirror 9 is formed by vapor-depositing the surface of the magnetized garnet crystal 8 opposite to the surface facing the converging rod lens 6, the magnetized garnet crystal The surface opposite to the surface facing the converging rod lens 6 of 8 functions as the total reflection mirror 9 as it is. For this reason, it is not necessary to newly provide a separate reflecting means adjacent to the magnetized garnet crystal 8, and the polarization-independent multi-core optical isolator 1 can be configured compactly.

  In the above embodiment, since the magnetized garnet crystal 8 is magnetized in advance, the polarization direction of the optical signal passing through the magnetized garnet crystal 8 is rotated by the magnetic field of the magnetized garnet crystal 8. Can do. For this reason, it is not necessary to provide a device for applying a magnetic field to the magnetized garnet crystal 8 from the outside, and the polarization-independent type multi-core optical isolator 1 can be configured compactly.

  Next, a polarization independent multi-fiber optical isolator 20 according to a second embodiment in which the present invention is applied to an optical fiber communication system will be described.

  FIG. 5A is a plan view of the polarization-independent multi-core optical isolator 20 according to the present embodiment, and FIG. 5B is a side view thereof. In the following description of the polarization independent multi-core optical isolator 20 according to the present embodiment, the same or corresponding components as those of the polarization independent multi-core optical isolator 1 according to the first embodiment. The same reference numerals are used for and the description thereof is omitted.

  The polarization independent multi-fiber optical isolator 20 includes an optical fiber array 22, a rutile crystal 3, a quartz glass plate 4, a half-wave plate 5, a focusing rod lens 26, an air gap 7, a magnetized garnet crystal 8, and a total reflection mirror 9. Are arranged in this order. As in the first embodiment, the optical fiber array 22 includes two pairs of optical fibers 10 and 11 and optical fibers 12 and 13 whose optical axes are parallel to each other arranged in parallel at equal intervals of 250 [μm] on the same plane. Have been integrated.

  The polarization-independent multi-core optical isolator 20 in the present embodiment is formed by tilting the end face 22a of the optical fiber array 22 by 8 ° with respect to a plane perpendicular to the optical axes of the optical fibers 10 to 13, The light input / output end faces 3a, 3b, 4a, 4b, 5a, 5b of the rutile crystal 3, the quartz glass plate 4 and the half-wave plate 5 are arranged parallel to the end face 22a of the optical fiber array 22, that is, inclined by 8 °. Has been. Further, the end face 26 a facing the quartz glass plate 4 and the half-wave plate 5 of the converging rod lens 26 is formed to be inclined by 8 ° so as to be substantially parallel to the end face 22 a of the optical fiber array 22. The half-wave plate 5 has the optical axis aligned when the optical signal A and the optical signal B are incident at an angle of 8 °. Other configurations are the same as those of the polarization-independent multi-core optical isolator 1 in the first embodiment.

  The operation when the optical signal A and the optical signal B having a wavelength of 1.55 [μm] propagate through the polarization-independent multi-core optical isolator 20 in the forward direction in the above configuration will be described. FIG. 5 described above shows an optical signal path when the optical signal A is incident in the forward direction from the optical fiber 10 and an optical signal path when the optical signal B is incident in the forward direction from the optical fiber 12. ing. 6A to 6I show the ordinary ray O and extraordinary ray E of the optical signal A at the positions FA, FB, FC, FD, FE, FF, FG, FH, and FJ shown in FIG. (J) to (r) show the polarization state and the arrangement relationship of the ordinary ray O and the extraordinary ray E of the optical signal B at each of these positions. It is shown. This figure is displayed in a state where the rutile crystal 3 side is viewed from the optical fiber array 22 side, as in FIGS. 2 and 4 described above, and each optical axis of the optical fibers 10 to 13 is in a direction perpendicular to the paper surface. It is in the direction. Also in this figure, the dotted line drawn horizontally is a plane including the optical axes of the optical fibers 10 to 13, and the alternate long and short dash line passes through the center line 2 c of the optical fiber array 22 and passes through the optical fiber 10. The plane perpendicular | vertical to the plane containing each optical axis of -13 is shown. This plane includes the converging center optical axis 6 c of the converging rod lens 26.

  As shown in FIG. 5, the optical signal A incident in the forward direction from the other end 10b of the optical fiber 10 is first incident on the end face 3a of the rutile crystal 3 at a predetermined angle. FIG. 6A shows the polarization state and arrangement relationship of the optical signal A at this time, and the ordinary ray O and the extraordinary ray E are orthogonal to each other. As described above, the crystal optical axis 3c of the rutile crystal 3 is oriented in a direction perpendicular to the plane including the optical axes of the optical fibers 10-13. Therefore, when the optical signal A passes through the rutile crystal 3, the extraordinary ray E having a polarization in a direction parallel to the crystal optical axis 3c is an ordinary ray having a polarization in a direction perpendicular to the crystal optical axis 3c. Upon receiving the spatial displacement 3d from O, the ordinary ray O and the extraordinary ray E are separated in a direction perpendicular to the plane including the optical axes of the optical fibers 10 to 13, as shown in FIG.

  The separated ordinary ray O and extraordinary ray E are incident on the end face 5a of the half-wave plate 5 at a predetermined angle. Since the optical axis of the half-wave plate 5 is oriented at an angle of 22.5 ° counterclockwise with respect to the polarization direction of the ordinary ray O in the state shown in FIG. The polarization direction of the light beam E is rotated by 45 ° counterclockwise as shown in FIG.

  Subsequently, the ordinary ray O and the extraordinary ray E are incident on the end face 26 a of the converging rod lens 26. At that time, the ordinary ray O and the extraordinary ray E sandwich a plane parallel to the plane including the optical axes of the optical fibers 10 to 13 and including the converging center optical axis 26c of the converging rod lens 26 from above and below at substantially equal intervals. Incident on the position. At this time, the ordinary ray O and the extraordinary ray E are substantially equidistant from the focusing center optical axis 6c. In the converging rod lens 26, the ordinary ray O and the extraordinary ray E are converted into parallel rays, approaching each other as they proceed and approaching the converging center optical axis 6c, and from the lens end face at an exit angle of about 1 °. Emitted. The state of the ordinary ray O and the extraordinary ray E at this time is shown in FIG.

  Next, the ordinary ray O and the extraordinary ray E emitted from the lens end face of the converging rod lens 26 pass through the gap 7 of about 200 [μm] and enter the magnetized garnet crystal 8. The polarization direction of the ordinary ray O and the extraordinary ray E is rotated by 22.5 ° counterclockwise by the magnetized garnet crystal 8. Next, the optical signal A from the magnetized garnet crystal 8 is reflected by the total reflection mirror 9, and on this total reflection mirror 9, the positions of the ordinary ray O and the extraordinary ray E are shown in FIG. As shown, they are almost identical.

  The ordinary ray O and the extraordinary ray E reflected by the total reflection mirror 9 enter the magnetized garnet crystal 8 again, and are further rotated by 22.5 ° counterclockwise by the magnetized garnet crystal 8. By reciprocating through the magnetized garnet crystal 8, the light beams O and E have their polarization directions rotated 45 ° counterclockwise, and the half-wave plate 5 rotates 45 °. Together, this results in a 90 ° counterclockwise rotation. This state is shown in FIG.

  Further, due to reflection by the total reflection mirror 9, the ordinary ray O and the extraordinary ray E are passed in a plane perpendicular to the plane including the respective optical axes of the optical fibers 10 to 13 through the converging center optical axis 6 c of the converging rod lens 26. Although the physical positions are interchanged, the polarization states of each remain the same as before reflection. Further, in a plane parallel to the plane including the optical axes of the optical fibers 10 to 13, the ordinary ray O and the extraordinary ray E are emitted from the optical fiber 10 side across the focusing center optical axis 6 c of the focusing rod lens 26. The spatial position is switched to the fiber 11 side.

  Next, the ordinary ray O and the extraordinary ray E emitted from the magnetized garnet crystal 8 pass through the gap 7 of about 200 [μm] and enter the converging rod lens 26. Due to the effect of the converging rod lens 26, the ordinary ray O and the extraordinary ray E are converted into parallel rays, separated from each other as they travel, and away from the converging center optical axis 6c. The state at this time is shown in FIG. Subsequently, the ordinary ray O and the extraordinary ray E pass through the quartz glass plate 4, but the polarization direction of each ray is not affected. The state at this time is shown in FIG.

  Next, the ordinary ray O and the extraordinary ray E are incident on the end surface 3 b of the rutile crystal 3 at a predetermined angle. In the rutile crystal 3, the ordinary ray O is subjected to a spatial displacement action because its polarization direction is rotated by 90 ° and has a polarization in a direction parallel to the crystal optical axis 3 c of the rutile crystal 3. . However, since the polarization direction of the extraordinary ray E is rotated by 90 ° and has a polarization in a direction perpendicular to the crystal optical axis 3c of the rutile crystal 3, the extraordinary ray E passes through without being subjected to a spatial displacement action. . Therefore, the ordinary ray O that has undergone the spatial displacement is recombined with the extraordinary ray E as shown in FIG. The recombined ordinary ray O and extraordinary ray E enter the optical fiber 11 and are transmitted to an external optical signal path as a forward output optical signal.

  Further, the optical signal B incident in the forward direction from the other end 12b of the optical fiber 12 propagates along the same path as the optical signal A outside the optical signal A, as shown in FIGS. To do. That is, the optical signal B is first incident on the end surface 3a of the rutile crystal 3 at a predetermined angle. FIG. 6 (j) shows the polarization state and arrangement relationship of the optical signal B at this time, and the ordinary ray O and the extraordinary ray E are orthogonal to each other. The ordinary ray O and the extraordinary ray E are separated in a direction perpendicular to the plane including the optical axes of the optical fibers 10 to 13 in the rutile crystal 3 as shown in FIG. As shown in (l), each half-wave plate 5 is rotated 45 ° counterclockwise. Subsequently, the ordinary ray O and the extraordinary ray E that have entered the converging rod lens 6 are converted as shown in FIG. 6 (m) and emitted from the lens end face. Then, after passing through the gap 7, it enters the magnetized garnet crystal 8, and the polarization direction is rotated 22.5 ° counterclockwise. Subsequently, the ordinary ray O and the extraordinary ray E are reflected by the total reflection mirror 9. As shown in FIG. 6 (n), the positions of the ordinary ray O and the extraordinary ray E substantially coincide on the total reflection mirror 9.

  Next, the ordinary ray O and the extraordinary ray E reflected by the total reflection mirror 9 are further rotated by 22.5 ° counterclockwise by the magnetized garnet crystal 8 again. This state is shown in FIG. Subsequently, after passing through the gap 7, the ordinary ray O and the extraordinary ray E are converted as shown in FIG. 6 (p) due to the effect of the converging rod lens 6. Thereafter, it passes through the quartz glass plate 4, but the polarization direction of each light beam is not affected. The state at this time is shown in FIG. Thereafter, in the rutile crystal 3, the ordinary ray O is subjected to a spatial displacement action by the rutile crystal 3, but the extraordinary ray E passes through without being subjected to the spatial displacement action. Therefore, as shown in FIG. Ray O and extraordinary ray E recombine. The recombined ordinary ray O and extraordinary ray E enter the optical fiber 13 and are transmitted to the external optical signal path as a forward output optical signal.

  Next, an operation when the optical signal A and the optical signal B having a wavelength of 1.55 [μm] propagate through the polarization-independent multi-core optical isolator 20 in the reverse direction will be described. FIG. 7 shows an optical signal path when the optical signal A is incident in the reverse direction from the optical fiber 11 and an optical signal path when the optical signal B is incident in the reverse direction from the optical fiber 13. (A) is a plan view of the polarization-independent multi-core optical isolator 20, and (b) is a side view thereof. In the figure, the same parts as those in FIG. 8A to 8I show the ordinary ray O and the extraordinary ray E of the optical signal A at the positions BA, BB, BC, BD, BE, BF, BG, BH, BJ shown in FIG. (J) to (r) show the polarization state and the arrangement relationship of the ordinary ray O and the extraordinary ray E of the optical signal B at each of these positions. It is shown. FIG. 8 is displayed in a state where the rutile crystal 3 side is viewed from the optical fiber array 22 side as in FIGS. 2, 4, and 6, and the direction perpendicular to the paper surface is that of the optical fibers 10 to 13. Each optical axis direction. Also in this figure, the dotted line drawn horizontally is a plane including the optical axes of the optical fibers 10 to 13, and the alternate long and short dash line passes through the center line 2 c of the optical fiber array 22 and passes through the optical fiber 10. The plane perpendicular | vertical to the plane containing each optical axis of -13 is shown. This plane includes the converging center optical axis 6 c of the converging rod lens 26.

  As shown in FIG. 7, an optical signal A having a wavelength of 1.55 [μm] is emitted from the optical fiber 11 in the reverse direction, and is first incident on the end face 3a of the rutile crystal 3 at a predetermined angle. The state at this time is shown in FIG. 8A, and the ordinary ray O and the extraordinary ray E are orthogonal to each other. As described above, the optical signal A incident on the rutile crystal 3 includes an extraordinary ray E having a polarization in a direction parallel to the crystal optical axis 3c in the rutile crystal 3, as shown in FIG. The ordinary ray O and the extraordinary ray E receive a spatial displacement from the ordinary ray O having a polarization in a direction perpendicular to the crystal optical axis 3c, and the ordinary ray O and the extraordinary ray E are perpendicular to the plane including each optical axis of the optical fibers 10-13. Separated. Subsequently, the separated ordinary ray O and extraordinary ray E pass through the quartz glass plate 4, but the polarization directions of the ordinary ray O and extraordinary ray E are not affected and do not rotate. The state at this time is shown in FIG.

  Next, the ordinary ray O and the extraordinary ray E emitted from the quartz glass plate 4 are incident on the end surface 26 a of the converging rod lens 26 at a predetermined angle. At that time, the ordinary ray O and the extraordinary ray E sandwich a plane parallel to the plane including the optical axes of the optical fibers 10 to 13 and including the converging center optical axis 6c of the converging rod lens 26 from above and below at substantially equal intervals. Incident on the position. At this time, the ordinary ray O and the extraordinary ray E are at substantially equal distances from the converging center optical axis 6 c of the converging rod lens 26. In the converging rod lens 26, the ordinary ray O and the extraordinary ray E are converted into parallel rays, approaching each other as they proceed and approaching the converging center optical axis 6c, and from the lens end face at an exit angle of about 1 °. Emitted. The state of the ordinary ray O and the extraordinary ray E at this time is shown in FIG.

  The ordinary ray O and the extraordinary ray E emitted from the lens end face of the converging rod lens 26 pass through the gap 7 of about 200 [μm] and enter the magnetized garnet crystal 8. The incident ordinary ray O and extraordinary ray E are rotated by 22.5 ° in the counterclockwise direction by the magnetized garnet crystal 8. Next, the optical signal A from the magnetized garnet crystal 8 is reflected by the total reflection mirror 9. On this total reflection mirror 9, the positions of the ordinary ray O and the extraordinary ray E are shown in FIG. 8 (e). And so on. The ordinary ray O and the extraordinary ray E reflected by the total reflection mirror 9 enter the magnetized garnet crystal 8 again, and are further rotated by 22.5 ° counterclockwise by the magnetized garnet crystal 8. By passing back and forth through the magnetized garnet crystal 8, as a result, the polarization directions of the light beams O and E are rotated 45 ° counterclockwise. The state at this time is shown in FIG.

  Further, due to reflection by the total reflection mirror 9, the ordinary ray O and the extraordinary ray E are passed in a plane perpendicular to the plane including the respective optical axes of the optical fibers 10 to 13 through the converging center optical axis 6 c of the converging rod lens 26. Although the physical positions are interchanged, the polarization states of each remain the same as before reflection. Further, in the plane parallel to the plane including the respective optical axes of the optical fibers 10 and 11, the ordinary ray O and the extraordinary ray E are located from the optical fiber 11 side across the converging center optical axis 6 c of the converging rod lens 26. The spatial position is switched to the optical fiber 10 side.

  Next, the ordinary ray O and the extraordinary ray E emitted from the magnetized garnet crystal 8 pass through the gap 7 of about 200 [μm] and enter the converging rod lens 26. The ordinary ray O and the extraordinary ray E are converted into parallel rays by the effect of the converging rod lens 26, and are separated from each other as they travel and away from the converging center optical axis 6c. The state at this time is shown in FIG.

  Subsequently, the separated ordinary ray O and extraordinary ray E are incident on the end surface 5b of the half-wave plate 5 at a predetermined angle, but the half-wave plate 5 has a polarization of the ordinary ray O in the state shown in FIG. Since the optical axis is oriented at an angle of −22.5 ° with respect to the wave direction, the polarization directions of the ordinary ray O and the extraordinary ray E are rotated by −45 ° counterclockwise. As a result, the angle −45 ° of the polarization direction rotated by the half-wave plate 5 and the angle 45 ° of the polarization direction rotated by the magnetized garnet crystal 8 cancel each other, and the ordinary ray O and the extraordinary ray E The total rotation angle in the polarization direction is 0 °. This state is shown in FIG.

  The ordinary ray O and the extraordinary ray E that have passed through the half-wave plate 5 are then incident on the end face 3b of the rutile crystal 3 at a predetermined angle. At this time, since the ordinary ray O is in a state of having a polarization in a direction perpendicular to the crystal optical axis 3c of the rutile crystal 3, it passes through without being subjected to a spatial displacement action. In addition, the extraordinary ray E has a polarization in a direction parallel to the crystal optical axis 3c of the rutile crystal 3, and thus undergoes a spatial displacement action away from the ordinary ray O as shown in FIG. As a result, the ordinary ray O and the extraordinary ray E are not recombined, and both are not incident on the optical fiber 10 because they are shifted from the optical fiber 10 by about 30 [μm]. For this reason, the isolation of the reverse direction about the optical signal A is implement | achieved.

  Further, the optical signal B incident in the reverse direction from the other end 13b of the optical fiber 13 propagates on the same path as the optical signal A outside the optical signal A, as shown in FIGS. To do. That is, the optical signal B is first incident on the end surface 3a of the rutile crystal 3 at a predetermined angle. FIG. 8J shows the polarization state and arrangement relationship of the optical signal B at this time, and the ordinary ray O and the extraordinary ray E are orthogonal to each other. The ordinary ray O and the extraordinary ray E are separated in the direction perpendicular to the plane including the optical axes of the optical fibers 10 to 13 in the rutile crystal 3 as shown in FIG. As shown in FIG. 8 (l), the separated ordinary ray O and extraordinary ray E pass through the quartz glass plate 4 in a state in which the polarization direction does not rotate, and then, by the converging rod lens 26, FIG. ). Subsequently, after passing through the gap 7, the ordinary ray O and the extraordinary ray E are reflected by the total reflection mirror 9 after the polarization direction is rotated by 22.5 ° counterclockwise by the magnetized garnet crystal 8. As shown in FIG. 8 (n), on the total reflection mirror 9, the positions of the ordinary ray O and the extraordinary ray E are substantially the same.

  Next, the ordinary ray O and the extraordinary ray E reflected by the total reflection mirror 9 are further rotated by 22.5 ° counterclockwise by the magnetized garnet crystal 8 again. This state is shown in FIG. Subsequently, the ordinary ray O and the extraordinary ray E pass through the gap 7 and are converted as shown in FIG. 8 (p) by the effect of the converging rod lens 26. Thereafter, as shown in FIG. 8 (q), the ordinary ray O and the extraordinary ray E are rotated by −45 ° counterclockwise by the half-wave plate 5, respectively. Thereafter, the ordinary ray O passes through the rutile crystal 3 without being subjected to the spatial displacement action. However, since the extraordinary ray E is subject to the spatial displacement action by the rutile crystal 3, as shown in FIG. The light beam O and the extraordinary light beam E are not recombined and are not incident on the optical fiber 12. For this reason, the isolation of the reverse direction about the optical signal B is implement | achieved.

  Also in the polarization independent multi-fiber optical isolator 20 according to the second embodiment of the present invention, the same operational effects as the polarization independent multi-fiber optical isolator 1 in the first embodiment can be obtained.

  Furthermore, according to the polarization-independent type multi-core optical isolator 20 according to the present embodiment, the end face 22a of the optical fiber array 22 is inclined by 8 ° with respect to a plane perpendicular to the optical axes of the optical fibers 10-13. The light input / output end faces 3a, 3b, 5a, 5b of the rutile crystal 3 and the half-wave plate 5 and the end face 26a of the converging rod lens 26 facing the half-wave plate 5 are substantially on the end face 22a of the optical fiber array 22. They are arranged and formed in parallel. Therefore, the incident light signal A and the incident light signal B incident from the optical fibers 10 to 13 and the reflected light signal A and the reflected light signal B reflected by the total reflection mirror 9 are the rutile crystal 3 and the half-wave plate 5. The light input / output end faces 3a, 3b, 5a and 5b and the end face 26a facing the half-wave plate 5 of the converging rod lens 26 do not return to the original direction, and return to the original direction. It is not incident on each of the optical fibers 10-13. For this reason, the incident light signals A and B incident from the optical fibers 10 to 13 and the reflected light signals A and B reflected by the total reflection mirror 9 are reflected by the end faces 3a, 3b, 5a, 5b and 26a and are generated. The effect of light is reduced. Therefore, it is less likely that reflected light is input to the optical device connected to the optical fibers 10 to 13, and the reflected light does not become noise of the optical device when the optical signal propagates in the forward direction.

  In each of the above embodiments, the case where the two pairs of optical fibers 10 and 11 and the optical fibers 12 and 13 are arranged in parallel in the optical fiber array 2 has been described. However, the present invention is not limited to this. Instead, the number of optical fiber pairs can be selected as required.

  9 shows an optical fiber in which the incident optical fibers 10, 12,... And the outgoing optical fibers 11, 13,... Are fixed at equal intervals on the same plane by capillaries opened in the array body, that is, capillary holes. It is sectional drawing which cut | disconnected the array 2 by the surface perpendicular | vertical to the optical axis of each optical fiber 10-13. The figure (a) shows a case where a total of 2n (n ≧ 2) n pairs of optical fibers are distributed to the left and right by n with the center between the two optical fibers 10 and 11 as the center line 2c. Show. FIG. 2B shows a case where a total of 2n n pairs of optical fibers are arranged in the left-right direction by n, with the optical axis of one optical fiber as the center line 2c. The optical fiber array 2 is configured by inserting the respective incident optical fibers 10, 12,... And the respective outgoing optical fibers 11, 13,... Into capillaries opened in the array body, or is cut into the array body. Each of the incident optical fibers 10, 12,... And each of the outgoing optical fibers 11, 13,.

  According to this configuration, the distance between the n pairs of incident optical fibers 10, 12,... And the outgoing optical fibers 11, 13,... Is symmetrical with one optical fiber of the optical fiber array 2 as the center line 2c. The distance between the two optical fibers arranged, or the distance between the two optical fibers arranged symmetrically with the center between the two optical fibers 10 and 11 of the optical fiber array 2 as the center line 2c. . Therefore, the distance between the pair of incident optical fibers 10, 12,... And the outgoing optical fibers 11, 13,. I can do it. The polarization-independent multi-fiber optical isolators 1 and 20 are connected to a plurality of optical fibers constituting an optical signal path and optical fibers aligned with capillaries or V grooves of the array body. For this reason, the polarization-independent multi-core optical isolators 1 and 20 can be easily connected to a plurality of optical fibers constituting the optical signal path. Further, the polarization-independent multi-fiber optical isolators 1 and 20 having different signal paths can be easily configured by simply replacing the optical fiber array 2 with another optical fiber array having a different number of cores.

  In each of the above embodiments, one pair of the incident optical fiber 10 and the outgoing optical fiber 11 and the other pair of the incoming optical fiber 12 and the outgoing optical fiber 13 are arranged in parallel on the same plane. However, these pairs of optical fibers 10 to 13 are not necessarily on the same plane. One pair of the incident optical fiber 10 and the outgoing optical fiber 11 and the other pair of the incoming optical fiber 12 and the outgoing optical fiber 13 are used. And may be arranged on different planes. Further, the optical fibers 10 to 13 do not necessarily have to be arranged at equal intervals, and the incident optical fiber and the outgoing optical fiber that form a pair need only be equidistant from the center line 2 c of the optical fiber array 2.

  In each of the above embodiments, the case where the half-wave plate 5 is disposed on the side through which the optical signal A emitted from the optical fiber 10 and the optical signal B emitted from the optical fiber 12 pass has been described. As described above, the reflection light signal A and the reflection light signal B reflected by the total reflection mirror 9 may be disposed on the side through which they pass. Further, instead of using the quartz glass plate 4 in pair with the half-wave plate 5, a medium that does not rotate the polarization direction may be used.

  In addition, although the magnetized garnet crystal 8 is used as the nonreciprocal polarization plane rotation element, other medium may be used as long as the nonreciprocal polarization plane rotation element rotates the polarization by 22.5 ° at the optical signal wavelength to be used. Is also possible. For example, a configuration in which a nonreciprocal polarization plane rotating element is covered with a magnetic material, that is, a magnet that applies a predetermined magnetic field to a non-reciprocal polarization plane rotating element that is not magnetized can be installed outside the element. is there. Further, although the refractive index distribution type converging rod lenses 6 and 26 are used as the condensing means, the optical signal A and the optical signal B incident from the respective optical fibers 10 to 13 are abnormal from the ordinary ray O by the rutile crystal 3. When the light beam E is separated from the light beam E, the crystal optical axis 3c of the rutile crystal 3 is set so that the separation direction of the ordinary light beam O and the extraordinary light beam E is perpendicular to the plane including the optical axes of the pair of optical fibers 10-13. Many different condensing means can be used as long as they are oriented and the ordinary ray O and the extraordinary ray E are arranged at approximately equal distances from the central optical axis of the lens.

  In the second embodiment, the end face 22a of the optical fiber array 22 and the light input / output end faces 3a, 3b, 4a, 4b, 5a, 5b of the rutile crystal 3, the quartz glass plate 4, and the half-wave plate 5 are used. In the above description, the end surface 26a of the converging rod lens 26 is tilted by 8 ° with respect to the plane perpendicular to the optical axis of the optical fibers 10, 11, 12, and 13. However, the end surface 26a is tilted within a range of 3 to 16 °. May be.

  In any of the above cases, the same effects as those of the above embodiments can be obtained.

  In each of the above embodiments, the case where the polarization-independent type multi-fiber optical isolator is applied to an optical communication system has been described. However, the present invention is not limited to this, and may be applied to an optical sensor system. Is possible. Even in such a case, the same effects as the above-described embodiments are obtained.

The polarization independent multi-fiber optical isolator according to the first embodiment of the present invention shows a configuration when an optical signal propagates in the forward direction, (a) is a plan view thereof, and (b) is a side view thereof. FIG. FIG. 3 is a state relationship diagram showing polarization states and arrangement relationships of ordinary rays and extraordinary rays propagating in the forward direction at each position in the polarization-independent multi-core optical isolator according to the first embodiment of the present invention. The polarization independent multi-core optical isolator according to the first embodiment of the present invention shows a configuration when an optical signal propagates in the reverse direction, (a) is a plan view thereof, and (b) is a side view thereof. FIG. FIG. 3 is a state relationship diagram showing polarization states and arrangement relationships of ordinary rays and extraordinary rays propagating in opposite directions at each position in the polarization-independent multi-core optical isolator according to the first embodiment of the present invention. The polarization independent multi-fiber optical isolator according to the second embodiment of the present invention shows a configuration when an optical signal propagates in the forward direction, (a) is a plan view thereof, and (b) is a side view thereof. FIG. FIG. 10 is a state relationship diagram showing polarization states and arrangement relationships of ordinary rays and extraordinary rays propagating in the forward direction at each position in the polarization-independent multi-core optical isolator according to the second embodiment of the present invention. The polarization independent multi-core optical isolator according to the second embodiment of the present invention shows a configuration when an optical signal propagates in the reverse direction, (a) is a plan view thereof, and (b) is a side view thereof. FIG. FIG. 6 is a state relationship diagram showing polarization states and arrangement relationships of ordinary rays and extraordinary rays propagating in opposite directions at each position in a polarization-independent multi-core optical isolator according to a second embodiment of the present invention. It is sectional drawing of the optical fiber array in the polarization independent type multi-core optical isolator by the modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,20 ... Polarization-independent type multi-core optical isolator 2,22 ... Optical fiber array 3 ... Rutyl crystal 3c ... Crystal optical axis 4 ... Quartz glass plate 5 ... Half wavelength plate 6,26 ... Focusing rod lens 6c ... Focusing Central optical axis 7 ... Air gap 8 ... Magnetized garnet crystal 9 ... Total reflection mirror 10, 11, 12, 13 ... Optical fiber

Claims (11)

A plurality of pairs of an incident optical fiber that inputs a forward optical signal and an outgoing optical fiber that emits a forward optical signal incident from the incident optical fiber, the optical axes of which are parallel and arranged in parallel, and a crystal optical axis A polarization separation element that applies a spatial displacement to an extraordinary ray of an optical signal in a predetermined direction to separate the forward optical signal into an ordinary ray and an extraordinary ray, and the light of each incident optical fiber Provided either on the axis side or on the optical axis side of each outgoing optical fiber, the polarization directions of the ordinary ray and the extraordinary ray are rotated in the reverse direction depending on the propagation direction of the forward direction and the opposite direction. A polarization plane rotating element that rotates in a direction, a condensing unit that converts a condensing state of the ordinary ray and the extraordinary ray of an optical signal, and a polarization direction of the ordinary ray and the extraordinary ray regardless of the propagation direction. Rotate in a certain direction of rotation Non-reciprocal polarization plane rotating element to be reflected, and reflecting means for reflecting the ordinary ray and the extraordinary ray of the optical signal emitted from the non-reciprocal polarization plane rotating element and causing the optical signal to enter the non-reciprocal polarization plane rotating element again Are arranged in this order,
The angle of the polarization direction rotated by the polarization plane rotation element and the angle of the polarization direction rotated by the non-reciprocal polarization plane rotation element, the ordinary ray and the extraordinary ray separated by the polarization separation element When the ordinary ray and the extraordinary ray are separated by the polarization separation element in the optical axis side portion of the incident optical fiber and propagate in the forward direction, the rotation direction is the same, and the optical axis side portion of the outgoing optical fiber The polarization separation element is subjected to a spatial displacement action of returning the ordinary ray and the extraordinary ray to a mutual position where the ordinary ray and the extraordinary ray coincide with each other, so that the ordinary ray and the extraordinary ray are in the optical axis side portion of the outgoing optical fiber When it propagates in the reverse direction after being separated by the light beam, it is reversed in the reverse rotation direction and canceled by the polarization separation element in the optical axis side portion of the incident optical fiber. To receive a spatial displacement action of mutual position of further apart, the polarization separating element, the polarization plane rotating element and said non-reciprocal polarization plane rotating element is arranged on each other,
The crystal optical axis of the polarization separation element is such that the separation direction of the ordinary ray and the extraordinary ray is perpendicular to a plane including each optical axis of the pair of the incident optical fiber and the outgoing optical fiber, Oriented to be arranged in parallel planes,
The converging center optical axis of the condensing means is disposed equidistant from each optical axis of the pair of incident optical fiber and outgoing optical fiber, and on the side facing the polarization plane rotation element of the condensing means, The ordinary ray and the extraordinary ray of the optical signal propagating on the optical axis side of the incident optical fiber, and the ordinary ray of the optical signal propagating on the optical axis side of the outgoing optical fiber paired with the incident optical fiber, and the A polarization-independent type multi-fiber optical isolator characterized by being arranged at approximately equal distances from the optical axes of the four extraordinary rays.   A plurality of pairs of the incident optical fiber and the outgoing optical fiber are integrated as an optical fiber array, and an end face of the optical fiber array is in a plane including each optical axis of the pair of the incident optical fiber and the outgoing optical fiber. Vertical to each optical axis, facing each light input / output end face of the polarization separation element and the polarization plane rotation element, and the polarization plane rotation element of the condensing means. The polarization-independent multi-fiber optical isolator according to claim 1, wherein an end face that is substantially parallel to the end face of the optical fiber array.   A plurality of pairs of the incident optical fiber and the outgoing optical fiber are integrated as an optical fiber array, and an end surface of the optical fiber array is perpendicular to any optical axis of the incident optical fiber and the outgoing optical fiber. A surface that is inclined at a predetermined angle with respect to the surface and that faces the optical fiber array of the light collecting means is aligned with the focusing central optical axis of the light collecting means so as to be substantially parallel to the end face of the optical fiber array. The optical input / output end faces of the polarization splitting element and the polarization plane rotating element are inclined at a predetermined angle with respect to a vertical plane, and are aligned in accordance with the inclination of the end face of the optical fiber array. The polarization-independent type multi-fiber optical isolator according to claim 1.   One of the optical signal propagating on the optical axis side of each incident optical fiber or the optical signal propagating on the optical axis side of each outgoing optical fiber passes between the polarization separation element and the condensing means. 4. The non-polarized wave according to claim 1, wherein the polarization plane rotation element is disposed at a position, and an amorphous optical element is disposed at a position where the other passes. 5. Dependent multi-fiber optical isolator.   5. The polarization-independent multi-core light according to claim 1, wherein a heat insulating means is provided between the condensing means and the non-reciprocal polarization plane rotating element. Isolator.   The said reflecting means is directly processed and formed in the surface on the opposite side to the surface which opposes the said condensing means of the said nonreciprocal polarization plane rotation element, It is any one of the Claims 1-5 characterized by the above-mentioned. 2. A polarization-independent multi-fiber optical isolator according to item 1.   The polarization-independent multi-core optical isolator according to any one of claims 1 to 6, wherein the non-reciprocal polarization rotator is magnetized in advance.   The polarization-independent multi-fiber optical isolator according to claim 7, wherein the non-reciprocal polarization plane rotation element is covered with a magnetic material and magnetized in advance.   9. The polarization-independent type multi-fiber optical isolator according to claim 1, wherein the condensing unit is configured by a gradient index rod lens. 10.   10. The optical fiber array according to claim 2, wherein each of the incident optical fibers and each of the outgoing optical fibers is inserted into a capillary opened in the array body. The polarization independent multi-fiber optical isolator as described.   3. The optical fiber array according to claim 2, wherein each of the incident optical fibers and each of the outgoing optical fibers is placed and fixed in a V-groove processed in parallel with the array body. 10. The polarization-independent type multi-core optical isolator according to any one of items 9 to 9.

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