CN110646959B

CN110646959B - Reflective circulator

Info

Publication number: CN110646959B
Application number: CN201911089958.1A
Authority: CN
Inventors: 陈国平; 刘晓远; 邱炳龙
Original assignee: Guangdong Sanshiyuan Technology Co ltd
Current assignee: Guangdong Sanshiyuan Technology Co ltd
Priority date: 2019-11-08
Filing date: 2019-11-08
Publication date: 2023-05-09
Anticipated expiration: 2039-11-08
Also published as: CN110646959A

Abstract

The invention provides a reflective circulator, which comprises an optical fiber array, wherein a lens array is arranged at the exit end of the optical fiber array, a light-combining and light-splitting crystal is arranged at one side of the lens array, which is far away from the optical fiber array, a wave plate component is arranged at one side of the light-combining and light-splitting crystal, which is far away from the optical fiber array, a first Faraday spinning piece, a Wollaston component and a second Faraday spinning piece are sequentially arranged at one side of the wave plate component, which is far away from the light-splitting crystal, and a reflecting mirror is arranged at one side of the second Faraday spinning piece, which is far away from the Wollaston component. The invention can reduce the difficulty of the production process of the circulator and reduce the production cost of the circulator.

Description

Reflective circulator

Technical Field

The invention relates to the technical field of optical devices, in particular to a reflective circulator.

Background

Circulators are a common type of optical device, typically having multiple ports, from which a beam can only exit from the next adjacent port after entering, and the optical path is fixed, irreversible, and is commonly used for control of the beam propagation path. Common circulators include three-port circulators, four-port circulators, and the like.

US6310989 discloses a three-port reflective circulator structure, which is provided with an array fiber (FiberArray) comprising a plurality of ports, which can be used as an incident end or an emergent end of light, a lens is arranged at one side of the array fiber, the light beam emerging from the first port passes through the lens to form three collimated light beams, and the three collimated light beams are distributed in symmetrical included angles. Three beams of collimated light are changed into three parallel collimated light after passing through a roof prism, each beam of collimated light is separated into two beams of ordinary light and two beams of extraordinary light with polarization directions perpendicular to each other through a first displacement crystal, one beam of collimated light passes through a wave plate, the polarization directions of the beams of collimated light are rotated by 90 degrees, and the polarization directions of the two beams of collimated light are consistent. Then, the two beams pass through the second displacement crystal and then pass through the Faraday rotation plate, the polarization direction is rotated by 45 degrees, pass through the reflecting mirror and then pass through the Faraday rotation plate again, the polarization direction of the beams is rotated by 45 degrees again, and at the moment, the polarization direction of the beams is deflected by 90 degrees relative to the initial polarization direction. Then, the light beam is displaced after passing through the second displacement crystal again, and finally converged to the second port after upwards displacing, passing through the displacement crystal and the roof prism again, and finally converged to the third port and emitted after the light beam is converged to the third port.

Existing circulators of this type have the following disadvantages: firstly, the circulator uses the displacement crystal and generates beam offset to enable the beam reflected from the reflector after exiting from the first port to be translated to the second port, namely, the translation of the beam is realized through the second displacement crystal, so that the distance between the reflected beams is required to be very accurate to match the distance between the cores of the array optical fibers because the distance between the cores of the array optical fibers is very accurate, the distance between the reflected beams is controlled by the thickness of the displacement crystal, thus the processing tolerance requirement on the thickness of the displacement crystal is very high, the production cost of the circulator is increased, and the production process requirement of the circulator is very high.

Secondly, the existing circulator needs to use a roof prism, the roof prism can meet the use requirement only when the angle precision of the roof prism is high, and the production material cost of the circulator is increased, so that the production cost of the circulator is very high.

Disclosure of Invention

The invention mainly aims to provide the reflective circulator with low production cost and simple production process.

In order to achieve the main purpose of the invention, the reflective circulator provided by the invention comprises an optical fiber array, wherein the emergent end of the optical fiber array is provided with a lens array, one side of the lens array, which is far away from the optical fiber array, is provided with a light-combining and light-splitting crystal, one side of the light-combining and light-splitting crystal, which is far away from the optical fiber array, is provided with a wave plate component, one side of the wave plate component, which is far away from the light-splitting crystal, is sequentially provided with a first Faraday rotator, a Wollaston component and a second Faraday rotator, and one side of the second Faraday rotator, which is far away from the Wollaston component, is provided with a reflecting mirror.

According to the scheme, the beam deflects in the propagation direction through the Wollaston assembly, so that the reflective circulator is only provided with the light-combining light-splitting crystal, and the light-combining light-splitting crystal can be a displacement crystal, and compared with the conventional reflective circulator, the reflective circulator reduces the use of one displacement crystal. Moreover, as the Wollaston assembly is used for replacing the second displacement crystal in front of the reflecting mirror in the existing circulator and the lens array is used for realizing the collimation of the light beams, the light beams emitted from the lens array are quasi-straight light, and the calibration of the roof prism is not needed, so that the processing difficulty of the circulator is obviously reduced, and the production cost of the circulator is further reduced.

Preferably, the Wollaston assembly comprises two adjacent prisms, and the optical axes of the two prisms are perpendicular to each other.

Therefore, the Wollaston assembly is formed by using the prisms with the optical axes perpendicular to each other, and the propagation direction of the light beam is deflected when the light beam passes through the Wollaston assembly, so that the displacement of the light beam is realized. Therefore, the Wollaston prism is used for replacing the displacement crystal of the existing circulator, and the problem that the circulator is realized by using the displacement crystal with high processing difficulty is solved.

The further scheme is that the wave plate component comprises a glass sheet and a half wave plate, and the glass sheet and the half wave plate are attached to the end face of the light-combining and light-splitting crystal.

It can be seen that the polarization direction of the light beam is not changed when the light beam passes through the glass plate, but is deflected when the light beam passes through the half-wave plate, and the polarization direction of a part of the light beam can be changed by using the assembly of the glass plate and the half-wave plate.

In a further scheme, the glass plate is arranged on a first optical path of the light-combining and light-splitting crystal, and the half-wave plate is arranged on a second optical path of the light-combining and light-splitting crystal.

Therefore, for one path of light beam needing to change the polarization direction, a half wave plate can be arranged on the light path, and for the other path of light beam needing not to change the polarization direction, a glass plate can be arranged, so that the requirement of light beam polarization direction adjustment is met.

Still further, the half-wave plate is a 45 ° half-wave plate.

The wave plate component comprises two half-wave plates, wherein the two half-wave plates are respectively attached to the end faces of the light-combining and light-splitting crystal, and the two half-wave plates are respectively positioned on two light paths of the light-combining and light-splitting crystal.

Therefore, if the polarization directions of the two paths of light beams are required to rotate and the rotation directions are different, half-wave plates with different deflection angles can be respectively arranged on the light paths of the two paths of light beams, so that the requirement of rotation of the polarization directions of the light beams is met.

Further, the optical fiber array has more than three ports, and the ports are parallel to each other.

The optical fiber array is provided with more than three ports, so that the requirement of using a plurality of ports of the circulator can be met.

In a further scheme, the lens array comprises lenses which are arranged in parallel, the number of the lenses is equal to that of the ports, and the lenses are arranged in one-to-one correspondence with the ports.

Because each port corresponds to one lens, the light beam emitted from each port is collimated by the lens, so that the light beam emitted from the lens is collimated, and the volume of the circulator is reduced.

Still further, each lens is a silicon lens. Because the refractive index of the silicon lens is higher, the formed light spots are smaller, so that the size of an optical device at the later stage is smaller, and the miniaturization of the circulator is facilitated.

Drawings

Fig. 1 is a schematic structural view of an embodiment of the present invention.

Fig. 2 is a schematic structural diagram of another view of an embodiment of the present invention.

Fig. 3 is a schematic view of an optical path in a top view according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of the optical path in a side view of an embodiment of the present invention.

Fig. 5 is a schematic view of the polarization direction of a light beam passing through various devices of an embodiment of the present invention.

The invention is further described below with reference to the drawings and examples.

Detailed Description

The reflective circulator of the invention has three ports, see fig. 1 and 2, the circulator has an optical fiber array 10, a plurality of optical fibers are arranged in the optical fiber array 10, and the optical fiber array 10 has three ports from which light beams can be incident into the circulator or can be emitted from the ports. A lens array 14 is provided on one side of the optical fiber array 10, in this embodiment the lens array 14 is provided with three

silicon lenses

15, 16, 17, preferably with the axes of the three

silicon lenses

15, 16, 17 parallel to each other. And, each of the

silicon lenses

15, 16, 17 corresponds to one port of the optical fiber array 10, that is, three ports of the optical fiber array 10 are arranged in one-to-one correspondence with the three

silicon lenses

15, 16, 17. Thus, the beam exiting from one port will become collimated light after passing through one silicon lens.

A displacement crystal 20 as a light-combining and light-splitting crystal is provided on a side of the lens array 14 away from the optical fiber array 10, and after the light beam enters the displacement crystal 20, the light beam is split into two linearly polarized light beams having mutually perpendicular polarization directions. A wave plate assembly 24 is disposed on a side of the crystal 20 away from the lens array 14, in this embodiment, the wave plate assembly 24 includes a glass plate 25 and a half-wave plate, and the glass plate 25 and the half-wave plate 26 are mounted on the end face of the crystal 20 and are respectively located on two different optical paths. Preferably, half-wave plate 26 is a 45 half-wave plate, and after the linearly polarized light passes through the half-wave plate, the polarization direction of the light beam is rotated, for example, by 90 °. Thus, since the polarization direction of the light passing through the glass plate is not rotated, the deflection directions of the two linearly polarized lights emitted from the displacer crystal 20 after passing through the wave plate assembly 24 are the same.

A first faraday rotator 28, a wollaston assembly 30 and a second faraday rotator 35 are sequentially arranged on one side of the wave plate assembly away from the displacement crystal 20, wherein the wollaston assembly 30 is composed of two

prisms

31 and 32 with mutually perpendicular optical axes. In this embodiment, the first faraday rotator 28, the prism 31, the prism 32, and the second faraday rotator 35 are adjacent to each other in order, and the light beam emitted from the wave plate assembly 24 passes through the first faraday rotator 28, the prism 31, the prism 32, and the second faraday rotator 35 in order. Of course, a magnetic field generator is provided radially outside the first faraday rotator 38 and the second faraday rotator 35.

After the light beam passes through the first faraday rotator 28, the polarization direction of the light beam will be rotated by 45 °, and when the light beam passes through the wollaston module 30, the propagation direction of the light beam will be deflected, for example, in the direction of fig. 1, assuming that the light beam is incident on the prism 31 from a direction perpendicular to the surface of the prism 31, and when the light beam is incident on the prism 32 from the prism 31, the light beam will be deflected downward by a certain angle, and thus, the propagation direction of the light beam is not perpendicular to the incident surface of the prism 31. When the light beam exits from the prism 32, the propagation direction of the light beam is deflected, and the light beam is deflected by a small angle when it enters the second faraday rotator than when it enters the prism 31. When the light beams are incident on the second faraday rotator 35, the polarization directions of the two light beams are rotated again, but the propagation directions of the light beams are not changed.

A mirror 40 is provided on the side of the second faraday rotator 35 remote from the wollaston module 30, preferably with a highly reflective film coated on the surface of the mirror adjacent to the second faraday rotator 35 so that the light beam incident on the surface of the mirror 40 can be reflected back. In this embodiment, the incident surface of the reflecting mirror 40 is parallel to the incident surface of the prism 31, and since the light beam is deflected in the propagation direction after passing through the Wollaston assembly 30, the light beam is not perpendicularly incident on the surface of the reflecting mirror 40, but is incident on the reflecting mirror 40 at a certain angle, as shown in fig. 1. Thus, the beam reflected by the reflecting mirror 40 does not return to the second faraday rotator 35 along the original incident light path, and the reflected light path is at a distance from the original incident light path, and at this time, the reflected beam is actually translated with respect to the incident beam, for example, to the light path corresponding to the beam exiting from the second port.

The reflected light beam first enters the second faraday rotator 35 and the polarization direction will be rotated again, i.e. the polarization direction of the light beam is rotated by 45 °, at this time the polarization direction of the light beam is rotated by 90 ° with respect to the first time the light beam enters the second faraday rotator 35. When the beam passes through the Wollaston assembly 30 again, the direction of propagation will be deflected, i.e. the direction of propagation of the beam is parallel to the direction of the first incidence of the beam on the Wollaston assembly 30, but the direction of propagation is opposite, i.e. towards the displacement crystal 20.

Thereafter, the light beam will be incident on the first faraday rotator 28 again, the polarization direction of the light beam will be rotated again, and the polarization direction of the light beam will be restored to the state when passing the first faraday rotator 28 for the first time, i.e. the polarization directions of the two light beams are parallel to each other. The light beams will then be incident on the wave plate assembly 24 again, wherein the polarization direction of one beam is rotated, and the polarization direction of the other beam is not rotated, at this time, the polarization directions of the two beams are mutually perpendicular, and when the light beams pass through the displacement crystal 20 again, the two beams with mutually perpendicular polarization directions will be combined to form one beam, and finally the beam is incident on the silicon lens 16 and exits from the second port of the optical fiber array 10.

The propagation path of the light beam within the optical circulator and the change in polarization direction are described below in connection with fig. 3 to 5. As shown in fig. 3, the light beam exiting from the first port passes through the silicon lens 15 to form collimated light L10, and the collimated light L10 may include two light components with polarization directions perpendicular to each other, and the polarization directions of the two light components are shown in fig. 5 (a). In fig. 5, 6 boxes of each group are arranged in two rows and three columns, the upper row and the lower row respectively represent the polarization directions of two separated light beams after exiting from one silicon lens, and the three columns respectively represent the polarization directions of the light beams on the corresponding light paths of the three silicon lenses from right to left.

After entering the displacement crystal 20, two light beams L11 and L21 with mutually perpendicular polarization directions are formed, wherein one light beam is the ordinary light and the other light beam is the extraordinary light, and the polarization directions of the two light beams are shown in fig. 5 (b). As can be seen from fig. 3, the light beam L10 is split into two light beams L11 and L12 after being incident on the displacement crystal 20 in a plan view, and the optical paths of the two light beams L11 and L12 are separated. Referring to fig. 4, in the side view direction, the propagation directions of the two light beams L11, L12 within the displacement crystal 20 are the same, and therefore, the optical paths of the two light beams L11, L12 are separated only in the top view direction.

The light beams L11, L21 will pass through the wave plate assembly 24, e.g. the light beam L11 passes through the glass plate 25 in the wave plate assembly 24 to form the light beam L12 without a change in polarization direction, while the light beam L21 passes through the half wave plate 26 in the wave plate assembly 24 to form the light beam L22 with a 90 ° deflection in polarization direction, as shown in fig. 5 (c). At this time, the polarization direction of the light beam L12 is the same as that of the light beam L22.

Subsequently, the light beams L12, L22 are respectively incident on the first faraday rotator 28 to form light beams L13, L23, and the polarization directions of the light beams L13, L23 are rotated by 45 ° compared with the polarization directions of the light beams L12, L22, as shown in fig. 5 (d). At this time, the polarization directions of the light beam L13 and the light beam L23 are also the same.

Next, the light beams L13 and L23 are respectively incident on the wollaston device 30 to form the light beams L14 and L24, and the light beams L14 and L24 are not vertically incident on the reflecting mirror 40 because the polarization direction of the light beams is not changed by the wollaston device 30, but the propagation direction of the light beams is changed, and the propagation directions of the light beams L14 and L24 are close to the direction of the second port after passing through the wollaston device 30, as shown in fig. 4. As shown in fig. 5 (e), the polarization directions of the light beams L14 and L24 are close to each other in the direction of the silicon lens 16.

After passing through the wollaston module 30, the light beams L14, L24 are incident on the second faraday rotator 35 to form light beams L15, L25, and the polarization directions of the light beams L15, L25 are rotated 45 ° compared with the polarization directions of the light beams L14, L24 because the polarization directions of the light beams L15, L25 are rotated by the second faraday rotator 35, as shown in fig. 5 (f), and the polarization directions of the light beams L15, L25 are parallel to each other.

The light beams emitted from the second faraday rotator 35 form light beams L16 and L26 and are incident on the mirror 40, and the reflected light beams do not return along the optical path of the incident light beams because the light beams L16 and L26 are not vertically incident. As shown in fig. 4, taking the light beam L16 as an example, the light beam L16 is incident on the reflecting mirror 40 to form the light beam L31, the propagation direction of the light beam L31 is biased toward the direction of the silicon lens 16, and the light beam L31 is incident on the second faraday rotator 35 to form the light beam L32. Due to the rotation of the polarization direction of the light beam by the second faraday rotator 35, the polarization direction of the light beam L32 is rotated by 45 °, as shown in fig. 5 (g). Similarly, the polarization direction of the light beam L41 formed by the light beam L26 passing through the reflecting mirror 40 is not changed, but the propagation direction of the light beam L41 is different from the direction of the light beam L26. After the light beam L41 enters the second faraday rotator 35, the polarization direction of the formed light beam L42 is also rotated by 45 °. At this time, the polarization direction of the light beam L42 is rotated by 90 ° from the polarization direction of the light beam L25.

Next, the light beams L32, L42 are incident on the wollaston module 30 to form light beams L33, L43, and the propagation directions of the light beams L33, L43 are deflected again, that is, the propagation directions of the light beams L33, L43 are parallel to the light beams L14, L24, but the propagation directions are opposite, that is, the propagation directions toward the displacement crystal 20, and the polarization directions of the light beams L33, L43 are as shown in fig. 5 (h).

Thereafter, the light beams L33, L43 are incident on the first faraday rotator 28 to form light beams L34, L44, and the polarization directions of the light beams L34, L44 are rotated again by 45 °, as shown in fig. 5 (i). It can be seen that the polarization direction of the light beams L34, L44 is the same as the polarization direction of the light beams L13, L23, i.e. the polarization direction of the light beams will return to the state when passing the first faraday rotator 28, and the polarization directions of the two light beams L34, L44 are parallel to each other.

The light beams L34, L44 will then again enter the wave plate assembly 24 to form light beams L35, L45, respectively, wherein the light beam L35 will pass through the half wave plate 26 with its polarization direction rotated 90 °, the light beam L45 will pass through the glass plate with its polarization direction not deflected, and at this time, the polarization directions of the light beams L35, L45 are perpendicular to each other as shown in fig. 5 (j). When the light beams L35, L45 pass through the displacement crystal 20 again, light beams L36, L46 are formed, and the two light beams L36, L46 with mutually perpendicular polarization directions are combined to form a light beam L37, the polarization directions of which are shown in fig. 5 (k), and finally the light beam L37 enters the silicon lens 16 and exits from the second port of the optical fiber array 10.

It can be seen that the light beam L10 enters from the first port of the optical fiber array, and exits from the second port after a series of changes such as light splitting, polarization direction rotation, reflection, light combination, and the like. Similarly, the light beam incident from the second port will also undergo the same change as the light beam L10, and will exit from the third port. Further, since the light beam can be deflected only in one direction when passing through the Wollaston module 30, the optical path is irreversible, that is, the light beam incident from the second port cannot exit from the first port but can exit from the third port, thereby ensuring the unidirectional property of the optical path.

In the above embodiment, the wave plate assembly is composed of a glass plate and a half-wave plate, and in practical application, two half-wave plates may be used to form the wave plate assembly, and if two half-wave plates are used, the two half-wave plates are respectively attached to the end faces of the displacement crystal, and each half-wave plate is respectively located on one optical path. Since the light beam forms an ordinary light beam and an extraordinary light beam when passing through the displacement crystal, the two half-wave plates are respectively positioned on the light paths of the ordinary light beam and the extraordinary light beam. Of course, when the light beams pass through the two half-wave plates, the rotation angles of the polarization directions are different, for example, one light beam rotates 45 degrees clockwise, and the other light beam rotates 45 degrees anticlockwise, so as to ensure that the polarization directions of the two light beams after passing through the wave plate assembly are the same.

Because the Wollaston assembly 30 is used for realizing the deflection of the optical path, namely, the optical path is translated by a distance of one lens, the invention does not need to realize the translation of the optical path through a displacement crystal, and therefore, a displacement crystal with very strict thickness requirement is not needed to be arranged, the processing difficulty of the circulator can be reduced, and the production cost of the circulator is also reduced. In addition, the invention does not need to arrange a roof prism with high angle precision for processing, and can further reduce the production cost of the circulator.

In addition, the lens array of the invention uses three mutually parallel silicon lenses, and the refractive index of the silicon lenses is very high, so that the formed light spot area is smaller, and therefore, the displacement crystal of the later stage can be realized by using a crystal with smaller volume, which is more beneficial to reducing the volume of the circulator.

Finally, it should be emphasized that the invention is not limited to the above embodiments, e.g. the use of a common lens instead of a silicon lens in the lens array of a reflective circulator, or the circulator being provided with more than four ports, such variations being intended to be included within the scope of the invention as claimed.

Claims

1. A reflective circulator, comprising:

an optical fiber array;

the method is characterized in that:

the optical fiber array comprises an optical fiber array, and is characterized in that a lens array is arranged at the emergent end of the optical fiber array, a light-combining and light-splitting crystal is arranged at one side of the lens array, which is far away from the optical fiber array, a wave plate component is arranged at one side of the light-combining and light-splitting crystal, a first Faraday rotator, a Wollaston component and a second Faraday rotator are sequentially arranged at one side of the wave plate component, which is far away from the light-combining and light-splitting crystal, and a reflecting mirror is arranged at one side of the second Faraday rotator, which is far away from the Wollaston component;

the polarization direction of the light beam after passing through the second Faraday rotator for the second time is rotated by 90 degrees compared with the polarization direction of the light beam after passing through the second Faraday rotator for the first time.

2. The reflective circulator of claim 1, wherein:

the Wollaston assembly comprises two prisms which are mutually adjacent, and optical axes of the two prisms are mutually perpendicular.

3. The reflective circulator of claim 1 or 2, wherein:

the wave plate component comprises a glass plate and a half wave plate, and the glass plate and the half wave plate are attached to the end face of the light-combination light-splitting crystal.

4. A reflective circulator according to claim 3, wherein:

the glass sheet is arranged on a first optical path of the light-combining and light-splitting crystal, and the half-wave plate is arranged on a second optical path of the light-combining and light-splitting crystal.

5. A reflective circulator according to claim 3, wherein:

the half-wave plate is a half-wave plate with the angle of 45 degrees.

6. The reflective circulator of claim 1 or 2, wherein:

the wave plate component comprises two half-wave plates, and the two half-wave plates are attached to the end face of the light-combining and light-splitting crystal.

7. The reflective circulator of claim 6, wherein:

the two half-wave plates are respectively positioned on two light paths of the light combination and light splitting crystal.

8. The reflective circulator of claim 1 or 2, wherein:

the optical fiber array is provided with more than three ports, and a plurality of the ports are arranged in parallel.

9. The reflective circulator of claim 8 wherein:

the lens array comprises lenses which are arranged in parallel, the number of the lenses is equal to that of the ports, and the lenses are arranged in one-to-one correspondence with the ports.

10. The reflective circulator of claim 9 wherein:

the lens is a silicon lens.