JPH087299B2 - WDM multi-core optical rotary joint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention uses a trapezoidal prism to optically connect a plurality of optical fibers installed in a rotating body and a plurality of optical fibers respectively installed in a rotating body and a plurality of optical fibers. The present invention relates to a multi-core optical rotary joint capable of simultaneously transmitting with high performance.

[Prior Art] Conventionally, a multi-core optical rotary joint shown in FIG. 6 (Japanese Utility Model Publication No. 61-6818) is known. As shown, in the fixed body 1, the rotating body 2 and the trapezoidal prism 3 are provided.
And a prism holder 4 for supporting the same are provided coaxially and rotatably. The exit side optical fiber 5 is connected to the entrance surface 3a of the trapezoidal prism 3 by the ferrule 6 attached to the fixed body 1 and the collimating rod-shaped converging lens 9, and the entrance side optical fiber 14 is attached to the rotating body 2. Ferrule 13 and convergent lens 10 for collimation
Is coupled to the exit surface 3C of the trapezoidal prism 3. Between the rotating body 2, the prism holder 4 and the fixed body 1, a speed change gear 40 as a speed change gear mechanism for decelerating the rotation of the rotating body 2 to a predetermined 1/2 angular velocity and transmitting it to the prism holder 4. , 41, 42 and a speed change gear shaft 43 are provided. Note that 2
0,21 are cap nuts attached to ferrules 6,13, 15,1
6 is a receptacle for connecting the ferrules 6 and 13.

The light emitted from the output-side optical fiber 5 is collimated by the converging lens 9 and enters the entrance surface 3a of the trapezoidal prism 3, where it is bent and totally reflected by the bottom surface 3b, and further refracted by the exit surface 3c. And is then converged by the converging lens 10 and incident on the incident-side optical fiber 14.

In this optical rotary joint, even if the rotator 2 rotates, the trapezoidal prism 3 rotates in the same direction at an angular velocity of 1/2 of the rotator 2 and acts to optically cancel the rotation of the rotator 2. The connection relationship between each outgoing side optical fiber 5 and the corresponding incoming side optical fiber 14 is guaranteed.

As shown in FIG. 6, the trapezoidal prism 3 has an inverted mirror image relationship between the incident image and the outgoing image with respect to the optical axis. Material BK-7 (borosilicate glass)) l = 4.23 × S
Is.

However, as shown in FIG. 8, the coupling loss between the optical fibers rapidly increases when the converging lens interval L exceeds 50 mm. When 1 = 63.5 to 84.6 mm, the coupling loss increases significantly to 3 to 7 dB. If there is a slight angle bend when the ferrule 6 is attached to the receptacle 15, the light beam will be trapezoidal prism 3
Is enlarged by the incident surface 3a, the bottom surface 3b, and the emission surface 3c, and the rotation characteristics of the multi-core optical rotary joint are deteriorated. In particular, as the length l of the trapezoidal prism 3 becomes longer, the expansion of the light flux due to the angle breaking becomes more remarkable, and the prism length l should be as short as possible. Therefore, the multi-core optical rotary joint shown in FIG. 6 is limited to four cases, and it is difficult to realize a multi-core optical rotary joint having a number of core wires larger than that in view of transmission characteristics and dimensions.

The applicant of the present application has proposed a multi-core optical rotary joint shown in FIG. 7 (Actual No. Sho 63-195304) in order to realize a multi-core optical rotary joint having 6 or more cores. This is a modification of the multi-core optical rotary joint shown in FIG. 6, in which a reflector 30 such as a long rhombic prism is arranged between the outgoing side optical fiber 5 and the trapezoidal prism 3, and similarly, the incoming oblique side optical fiber 14 and the trapezoidal side are formed. A reflector 31 such as a long rhombic prism is installed between the prisms 3. Then, in addition to the receptacles 15 and 16 located inside the aperture of the trapezoidal prism 3, the receptacles 11 and 12 housing the converging lenses 7 and 8 are arranged outside the aperture of the trapezoidal prism 3. Between the rotating body 2 and the prism holder 4 and the fixed body 1, as in FIG. 6, a speed change gear mechanism 22 for decelerating the rotation of the rotating body 2 to an angular velocity of 1/2 and transmitting it to the prism holder 4. As such, transmission gears 23, 24, 25, 26 and a transmission gear shaft 27 are provided.

In the multi-core optical rotary joint shown in FIG. 7, the light emitted from the optical fiber 17 belonging to the outer receptacle 11 is collimated by the converging lens 7 and enters the long rhombic prism of the reflector 30. After being reflected twice in the reflector 30, the emitted light enters the trapezoidal prism 3. The light emitted from the trapezoidal prism 3 enters the long orthorhombic prism of the reflector 31, is reflected twice, and then is emitted.
Are converged by and are incident on the incident side optical fiber 18.

In the multi-core optical rotary joint shown in FIG. 7, by interposing the reflectors 30 and 31 between the trapezoidal prism 3 and the optical fiber 5, the optical fibers 17 and 18 outside the aperture of the trapezoidal prism 3 are optically coupled. Connection is possible, and as a result, a trapezoidal prism with an aperture smaller than that of the trapezoidal prism 3 of the multi-core optical rotary joint shown in FIG. 6 is used to realize a 6-core multi-core optical rotary joint, greatly increasing the actual phase density. I was able to improve. Further, the trapezoidal prism 3 shown in FIG.
When using a trapezoidal prism having the same size as the above, an 8-core type could be easily realized.

[Problems to be Solved by the Invention] However, in the multi-core optical rotary joint shown in FIG. 7, even if the trapezoidal prism 3 shown in FIG. Without it, it is difficult to make more cores. When increasing the information transmission capacity of an optical fiber, so-called wavelength multiplex transmission using a plurality of wavelengths at the same time may be performed, and the emergence of a more multiple core wavelength multiplex optical rotary joint is desired.

A problem when performing wavelength division multiplexing transmission using a conventional multi-core optical rotary joint will be described with reference to FIG.

This figure shows an optical path when two lights of wavelengths λ1 and λ2 are incident on the central axis of the trapezoidal prism 3 from the left side. As indicated by the solid line, the light of wavelength λ1 is refracted at the entrance surface 3a of the trapezoidal prism 3, totally reflected at the bottom surface 3b, refracted again at the exit surface 3c, and emitted to the right. It is assumed that the aperture S of the trapezoidal prism 3 and its length 1 are determined so that the emitted light at this time is on the central axis of the trapezoidal prism 3. In such a case, even if light is incident on an arbitrary position with respect to the wavelength λ1,
Multiple optical rotary joints can be constructed as described above. On the other hand, the wavelength λ2 shorter than the wavelength λ1
The light is different from the refractive index of .lamda.1 due to chromatic aberration, and therefore the outgoing light is offset by .DELTA. As shown by the broken line, unlike the solid line optical path in which the refractive indexes at the entrance surface 3a and the exit surface 3b are .lambda.1. For example, if the material BK-7 (borosilicate crown glass) for the trapezoidal prism 3 is used and the aperture S = 20 mm and λ1 = 1.3 μm, then 1 = 85 mm, but if light of λ2 = 0.85 μm is incident on this. The offset Δ is 4 mm, and transmission is not possible at all unless the diameter of the micro convex lens is set to 4 mm or more. Even if a part of the light can be transmitted, the coupling loss becomes large and the rotation fluctuation becomes large, so that the conventional trapezoidal prism made of a single material cannot be used.

An object of the present invention is to provide a high-performance multi-core optical rotary joint capable of mounting an optical fiber having a larger number of cores than conventional ones without increasing the size of the device in view of the above-mentioned problems of the conventional art. .

[Means for Solving the Problem] A wavelength-multiplexed multi-core optical rotary joint of the present invention is an achromatic trapezoidal prism that is provided between a rotating body and a fixed body and is rotated at a predetermined angular velocity with the rotating body. A plurality of pairs of converging lenses installed on the rotating body and the fixed body such that they are optically faced and optically opposed to the entrance surface and the exit surface of the trapezoidal prism, respectively, and the entrance surface of the trapezoidal prism. Of the plurality of pairs of converging lenses, the reflector having an outer reflection surface facing the outer pair and an inner reflection surface facing the trapezoidal prism, and An interference film filter provided between an outer reflecting surface and an inner reflecting surface so as to face an inner pair of the converging lenses, wherein the outer pair of the converging lenses moves to the reflecting pair. Is incident on the outside An interference film filter that transmits the light of the first wavelength reflected by the reflecting surface and reflects the light of the second wavelength that is incident on the reflector from the inner pair of the converging lenses. Is.

Instead of providing the interference film filter between the outer reflection surface and the inner reflection surface of the reflector, the inner reflection surface of the reflector reflects the light of the first wavelength and the light of the second wavelength is reflected. It is also possible to provide an interference film filter that transmits light.

[Operation] (1) An achromatic trapezoidal prism that corrects chromatic aberration is used, and a first prism is provided between the outer reflection surface and the inner reflection surface of the reflector.
In the mode in which the interference film filter that transmits the light having the wavelength λ1 and reflects the light having the second wavelength λ2 is provided, it operates as follows.

The light of the first wavelength λ1 emitted from the outside of the converging lens, for example, the converging lens of the first emission side optical fiber (17) outside the aperture of the trapezoidal prism, is reflected on the outer reflection surface of the reflector. First, it is reflected inward, and the interference filter (5
After passing through 1), it is reflected by the inner reflecting surface of the reflector and becomes light along the axial direction of the trapezoidal prism, which enters the entrance surface of the trapezoidal prism.

On the other hand, the light of the second wavelength λ2 emitted from the convergent lens inside the converging lens, for example, the converging lens of the second emission side optical fiber (5) within the aperture of the trapezoidal prism, is generated by the interference film filter (51 ), Is reflected by the inner reflecting surface of the reflector and enters the entrance surface of the trapezoidal prism.

The paths of the λ1 and λ2 lights that enter the trapezoidal prism from its entrance surface are changed so as to create an inverted mirror image relationship between the incident image and the outgoing image with respect to the optical axis. The light is emitted along the line and is emitted from the emission surface.

Of the light emitted from the emission surface of the trapezoidal prism, the light of the first wavelength λ1 is reflected by the inner reflection surface of the reflector, passes through the interference film filter (52), and then is reflected by the outer reflection surface. It is guided to an outer converging lens located in a region outside the aperture of the trapezoidal prism and is coupled to the first incident optical fiber (18) by the outer converging lens. Meanwhile, the second
The light of wavelength λ2 is reflected by the inner reflection surface of the reflector and then by the interference film filter (52) in the same manner as the light of the first wavelength described above, and enters the area within the aperture of the trapezoidal prism. It is guided to the inner converging lens located and is coupled to the second incident side optical fiber (14) by the inner converging lens.

(2) Next, an achromatic trapezoidal prism for correcting chromatic aberration is used, and the first wavelength λ1 is applied to the outer reflection surface of the reflector.
In the mode in which the interference film filter that reflects the light of (1) and transmits the light of the second wavelength λ2 is provided, it operates as follows.

The light of the first wavelength λ1 emitted from the outside of the converging lens, for example, the converging lens of the first emission side optical fiber (17) outside the aperture of the trapezoidal prism, is reflected on the outer reflection surface of the reflector. The light is reflected and then reflected by the inner reflection surface, that is, the interference film filter (50) and is incident on the incident surface of the trapezoidal prism as light along the axial direction of the trapezoidal prism.

On the other hand, the light of the second wavelength λ2 emitted from the convergent lens inside the converging lens, for example, the converging lens of the second emission side optical fiber (5) within the aperture of the trapezoidal prism, is generated by the interference film filter (50). ) Is transmitted as it is and is incident on the incident surface of the trapezoidal prism.

The paths of the λ1 and λ2 lights that have entered the trapezoidal prism are changed so as to cause an inverted mirror image relationship between the incident image and the outgoing image with respect to the optical axis, and the light along the axial direction of the trapezoidal prism is changed. Then, the light is emitted from the emission surface.

Of the light emitted from the trapezoidal prism, the light of the first wavelength λ1 is reflected by the inner reflection surface, that is, the interference film filter (60) and then by the outer reflection surface, and is positioned outside the aperture of the trapezoidal prism. To the outer converging lens,
Coupled to the first incident optical fiber (18). Meanwhile, the second
Of the wavelength λ2 is transmitted through the interference film filter (60) as it is, and is guided to the inner converging lens located in the area within the aperture of the trapezoidal prism. Is coupled to the incident side optical fiber (14).

In any of the above (1) and (2), the trapezoidal prism is rotated at a predetermined angular velocity, for example, half the rotational velocity of the rotating body, so that the rotating image on the rotating body side becomes a still image by the trapezoidal prism. And transmitted to the fixed body side. Alternatively, the stationary image on the fixed body side is converted into a rotational image having the same angular velocity as the rotating body by the trapezoidal prism and transmitted to the rotating body side. Therefore, even if the rotator rotates, the connection between the corresponding incoming and outgoing optical fibers on the rotator side and the fixed body side facing each other via the trapezoidal prism is maintained.

If the trapezoidal prism is an achromatic prism, the trapezoidal prism is formed by an achromatic prism consisting of two types of glass structures, a flint and a crown, from the entrance / exit surface to the anti-slope surface of the bottom surface. Even if the refractive index is different, the chromatic aberration can be corrected so that the same incident light and the same outgoing light can be obtained, and the loss can be suppressed even if wavelength division multiplexing transmission is performed.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory view showing an embodiment of the present invention. First
In the figure, reference numeral 1 denotes a fixed body, in which a part of the rotating body 2 is inserted and rotatably supported. Inside the fixed body 1, one end side of a prism holder 4 supporting the achromatic trapezoidal prism 32 is rotatably supported by a bearing 29, and the other end side of the prism holder 4 is rotatably supported inside the rotating body 2. ing.

On the fixed body 1 and the rotating body 2, a large number of receptacles for connecting the ferrule of the optical connector are arranged in a plurality of groups. Here we divide it into two groups,
The first group is a group of receptacles 11 and 12 arranged along an outer circle having a diameter larger than the diameter of the achromatic trapezoidal prism 32, and the second group is larger than the diameter of the achromatic trapezoidal prism 32. Receptacles 1 arranged along a small diameter inner circle
There are 5,16 groups. First group of receptacles 11, 12 and second
The receptacles 15 and 16 of the group house one converging lens 7, 8 or 11, 12 respectively, so that these rod-shaped converging lenses for collimating also have an outer converging lens.
It is divided into 7,8 and inner converging lenses 9,10. However, although there is a difference in which one of the outer and inner circles is arranged, the converging lenses 7 to 10 are optically arranged on the entrance surface a and the exit surface e of the achromatic trapezoidal prism 32, respectively. They are installed facing each other and optically facing each other.

Reference numerals 30 and 31 denote reflectors, which are long rhombic prisms having outer reflecting surfaces 30a and 31a facing the outer converging lens 7 and inner reflecting surfaces 30b and 31b facing the achromatic trapezoidal prism 32. The incident-side reflector 30 is provided between the individual converging lens 7 on the outer side and the individual converging lens 9 on the inner side between the incident surface a side of the achromatic trapezoidal prism 32 and the receptacles 15 and 16 sides. The outer reflecting surface 30 is provided so as to extend in the radial direction so as to be bridged and faces the converging lens 7 on the outer side thereof.
The converging lens 7 and the achromatic trapezoidal prism 32 can be optically coupled by a and the inner reflecting surface 30b facing the achromatic trapezoidal prism 32. On the other hand, the reflector 31 on the exit side is provided between the individual converging lens 8 on the outer side and the individual converging lens 10 on the inner side between the exit surface e side of the achromatic trapezoidal prism 32 and the receptacles 15 and 16 sides. Are provided so as to extend in the radial direction so as to bridge, and the converging lens 8 is provided by the outer reflecting surface 31a facing the converging lens 8 on the outer side and the inner reflecting surface 31b facing the achromatic trapezoidal prism 32. And the achromatic trapezoidal prism 32 can be optically coupled.

In particular, in the present embodiment, the reflectors 30 and 31 formed of these rhomboid prisms have inner reflection surfaces 30b and 31b on the optical axis connecting the inner converging lenses 7 and 10 and the achromatic trapezoidal prism 32, respectively. Is located and its inner reflective surface 30b, 31
On the back surface of b, the interference film filters 40 and 50 that respectively reflect the light of the first wavelength λ1 and transmit the light of the second wavelength λ2.
Is provided.

The outer receptacle 11 is the ferrule 6 holding the optical fiber 17, and the receptacle 12 is the optical fiber 6.
The ferrules 13 holding 18 are cap nuts 20 and 21 respectively.
It is attached by. Similarly, the inner receptacle 1
Ferrules of optical fibers 5, 14 (Fig. 6) are attached to 5,16.

Inside the fixed body 1 outside the prism holder 4, the rotating body 2
There is provided a speed change gear mechanism 22 for decelerating the rotation of No. 1 to a predetermined 1/2 angular velocity (rotation in the same direction) and transmitting it to the prism holder 4. The speed change gear mechanism 22 includes a gear 23 mounted on the outer circumference of the rotating body 2, a gear 24 mounted on a shaft 27 rotatably supported in the fixed body 1 and meshing with the gear 23, and a shaft 27.
It is mainly composed of a gear 25 provided above and meshing with a gear 26 on the outer peripheral portion of the center of the prism holder 4. The gears 24 and 25 of the intermediate gear are divided into two parts 24a, 24b and 25a and 25b so that there is a relative rotational deviation in the rotation direction, and between the two divided gears, there is a direction in which a rotational deviation is caused in them. An elastic member such as an elastic spring is provided. Reference numeral 28 is a rotary blade which is transmitted to the rotating body 2 of the rotating portion for optical transmission.

Next, the structure of the achromatic prism will be described with reference to FIG.

In FIG. 2, reference numeral 32 denotes an achromatic trapezoidal prism, the diameter of which is S, the length thereof is 1, and the base angle is φ1. This achromatic trapezoidal prism 32 is an isosceles triangular prism 33 having a base angle φ2 and a base l, and two isosceles rectangular prisms 34, 34 with the two slopes of the isosceles triangular prism 33 being bonded surfaces b and d, respectively.
35 are bonded together, and the overall diameter S, emission surface e, bottom surface c
It is configured as a trapezoidal prism having.

The isosceles triangular prism 33 and the quadrangular prisms 34, 35 may be those having a refractive index capable of correcting chromatic aberrations of different wavelengths. For example, the isosceles triangular prism 33 is a low-dispersion crown glass, an isosceles quadrilateral prism 34, The reference numeral 35 is composed of a fritton glass having a higher refractive index and a higher dispersion than the isosceles triangular prism.

 Next, the operation will be described.

The light of wavelength λ1 emitted from the emission side optical fiber 17 is
The light is collimated by the converging lens 7 and is incident on the side surface of the reflector 30 formed of a rhomboid prism. The incident light is totally reflected at a right angle by the outer reflecting surface 30a, travels along the axis of the rhomboid prism 30a, and reaches the inner reflecting surface 30b within the aperture of the achromatic trapezoidal prism 32. Here, since the interference film filter 50 that reflects the light of the wavelength λ1 is provided on the back surface of the inner reflection surface 30b, the light of the wavelength λ1 is totally reflected at a right angle and achromatic from the side surface of the oblong prism 30. The light is emitted as light parallel to the optical axis of the trapezoidal prism 32 and is incident on the achromatic trapezoidal prism 32.

Further, the light of wavelength λ2 emitted from the emission optical fiber (not shown) attached to the receptacle 7 is collimated by the converging lens 9 and the inner reflection surface of the reflector 30 formed of a long rhomboid prism. 30b, that is, the interference film filter 50
Reach Here, since the interference film filter 50 transmits the light having the wavelength λ2, the light having the wavelength λ2 is directly incident on the achromatic trapezoidal prism 32.

Wavelength λ1 incident from the right side of the achromatic trapezoidal prism 32
Light is first refracted at the incident surface a, refracted in the opposite direction at the next first bonding surface b, totally reflected at the bottom surface c, and refracted again at the second bonding surface d and the exit surface e. And emits to the left. On the other hand, the light of wavelength λ2 is refracted to a greater extent than λ1 on the incident surface a, but is greatly refracted in the opposite direction on the first bonding surface b, so that the gap between the optical paths is corrected. When the light is totally reflected by the bottom surface c and refracted by the second bonding surface d and the emission surface e, it is emitted on the same optical path as the light of wavelength λ1.

In the above example, the isosceles triangular prism 33 is a crown glass, and the isosceles rectangular prisms 34, 35 are flint glass, but they may be used in reverse.

Next, as a material for the unequal-sided square prisms 34 and 35, SF-
6 (heavy flint glass), isosceles triangular prism 33
An example of calculation of the dimensions of the achromatic trapezoidal prism 32 when LaK21 (lanthanum crown glass) is used as the material will be described below. The wavelengths are λ1 = 1.3 μm and λ2 = 0.85.
Calculated in μm. The refractive index at this time was 1.68222 and 7.78169 for SF-6 and 1.62410 and 1.63149 for LaK21, respectively.

Base angle φ1, when the trapezoidal prism 32 has an aperture S = 20 mm
The relationship between φ2 and the base length l is shown in FIG. For example, if the base angle φ1 of the achromatic trapezoidal prism is 45 °, the base angle φ2 of the isosceles triangular prism is about 13 ° and the length l is about 87 mm. Since the optical path length becomes longer as l becomes longer, it is desirable to make the base angle φ1 of the achromatic trapezoidal prism as small as possible within a manufacturable range. Further, the trapezoidal prism (length l≈85 mm) of the conventional example shown in FIG. 5 need only be made longer by 2 mm, so that it can be directly incorporated in the conventional multi-core optical rotary joint.

Light emitted from the emission surface e of the achromatic trapezoidal prism is separated into light of wavelength λ1 and light of wavelength λ2 by the interference film filter 60 provided on the reflector 31 formed of a rhomboidal prism. The light of λ1 is totally reflected by the inner reflecting surface 31b and the outer reflecting surface 31a, and propagates to the incident side optical fiber 18 through the converging lens 8. In addition, the light of wavelength λ2 passes through the interference film filter 60, passes through the converging lens 10, and is incident on the incident side optical fiber 14 attached to the receptacle 6.
(Fig. 6).

When the rotating body 2 rotates at the angular velocity ω, the prism holder 4 and the trapezoidal prism 32 are moved by the speed change gear mechanism 22 to 1 /.
It is designed to be rotationally driven in the same direction at an angular velocity of 2ω, and as described in detail in Japanese Utility Model Publication No. 61-24961,
Since the image on the side of the rotating body 2 is in a stationary state when viewed from the side of the fixed body 1, it is possible to connect a plurality of pairs of outgoing / incoming side optical fibers 117 and 18 regardless of the rotation of the rotating body 2.

Receptacle 11 outside the aperture of the achromatic trapezoidal prism 32
If eight optical fibers 17 are attached, that is, four cores 15 or four optical fibers 5 can be attached in the aperture of the achromatic trapezoidal prism 32.
It is possible to realize a 12-core type optical rotary joint, which was impossible in the past. An optical fiber having about 18 cores can be mounted by changing the dimensions of the reflectors 30 and 31 formed of the long rhomboid prism.

Up to now, it has been explained that the light of wavelength λ2 is within the aperture of the achromatic trapezoidal prism 32. However, by adopting a configuration in which the light of wavelength λ2 is incident from the outside of the aperture, it is possible to further increase the number of cores. As shown in FIG. 4 and FIG.
It becomes possible by providing in the middle of 0 and 31.

In FIGS. 4 and 5, the reflectors 30 composed of twelve oblong rhombic prisms are arranged radially from the center of the fixed body 1, and the outermost ends of the respective long rhombic prisms are connected to the outer receptacle 11
It faces the converging lens 7 inside and is coupled with a 12-core optical fiber that transmits the wavelength λ1. Also, a long rhombic prism 30
An interference film filter 51 that transmits light of the first wavelength and reflects light of the second wavelength is provided in the middle of the so as to face the converging lens 9 inside the receptacle 15 inside. Although not shown, the rotating body 2 side has the same configuration, and the interference film filter 52 faces the converging lens 10 in the inner receptacle 15 in the middle of the long rhombic prism in which 12 radial elements are arranged. It is provided.

Therefore, the light having the wavelength λ1 which is incident on the reflector 30 from the outer converging lens 7 is first reflected by the outer reflecting surface 30a and transmitted through the interference film filter 51, and then is transmitted from the inner converging lens 9 to the reflector 30. The incident light of the second wavelength λ2 is reflected by the interference film filter 51, and the light of the respective wavelengths λ1 and λ2 is reflected by the innermost end anti-slope 30b of the reflector 30 and is incident on the achromatic trapezoidal prism 31. To be done. Following the reverse path, the wavelength λ
The light of No. 1 passes through the interference film filter 52 and enters the optical fiber 14 from the outer converging lens 8, and the light of wavelength λ2 is reflected by the interference film filter 52 and goes from the inner converging lens 16 to the optical fiber 18. enter.

Since the interference film filters 51 and 52 can be provided at arbitrary places, they can be placed at random positions as shown in FIGS. 4 and 5.
Twelve inner optical connector receptacles 15 that pass the wavelength λ2 can be installed. In this case, a total of 24 core optical fibers can be mounted together with the outer optical connector receptacle 9.

[Effects of the Invention] As described above, according to the present invention, the following excellent effects can be obtained.

(1) By using an achromatic structure for the trapezoidal prism, even when wavelength multiplexing transmission with a wide wavelength interval such as λ1 = 0.85 μm and λ2 = 1.55 μm, the displacement of the light beam at the entrance and exit sides of the trapezoidal prism Multi-core optical rotary joint with few and low loss can be realized.

(2) Since the optical fiber can be attached regardless of the inside or outside diameter of the trapezoidal prism, it is possible to realize a multicore optical rotary joint which has never been seen. According to the invention 24
Even core type can be realized.

(3) Since a small trapezoidal prism can be used, the optical transmission loss is small even if the number of cores of the optical fiber is increased, and the device can be made small and inexpensive. Further, since the transmission gear mechanism can be downsized, it has high reliability even at high speed rotation.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a wavelength division multiplexing optical fiber rotary joint according to an embodiment of the present invention, FIG. 2 is a detailed view showing the action of an achromatic trapezoidal prism, and FIG. 3 is a color diagram in FIG. Prism length l for base angle φ1 of erase trapezoidal prism
And the base angle φ2, FIG. 4 is a front view of a 24-core type embodiment of the present invention as seen from the side of the fixed body, FIG. 5 is a partial sectional view thereof, and FIGS. 6 and 7 are FIG. 8 is a cross-sectional view showing the configuration of a conventional multi-core optical rotary joint, FIG. 8 is a view showing the relationship between the distance between converging lenses and optical coupling loss,
FIG. 9 is a diagram for explaining the operation of the conventional trapezoidal prism. In the figure, 1 is a fixed body, 2 is a rotating body, 3 is a trapezoidal prism, 5,
14,17,18 are optical fibers, 7,8 are outer converging lenses, 9,1
0 is the inner converging lens, 11 and 12 are the outer receptacles,
Reference numerals 15 and 16 are inner receptacles, 30 and 31 are reflectors composed of long rhombic prisms, 30a and 31a are outer reflection surfaces, 30a and 31b are outer reflection surfaces, 32 is an achromatic trapezoidal prism, and 50 and 60 are interference films. Indicates a filter.

Claims (2)

[Claims] 1. An achromatic trapezoidal prism, which is provided between a rotating body and a fixed body and is rotated at a predetermined angular velocity along with the rotating body, and an entrance surface and an exit surface of the trapezoidal prism are optically faced respectively. And a plurality of pairs of converging lenses installed on the rotating body and the fixed body so as to be optically opposed to each other, and provided on the entrance surface side and the exit surface side of the trapezoidal prism respectively, and the plurality of pairs of converging characteristics are provided. A reflector having an outer reflecting surface facing the outer pair of lenses and an inner reflecting surface facing the trapezoidal prism, and the converging lens of the converging lens between the outer reflecting surface and the inner reflecting surface of the reflector. An interference film filter provided so as to face the inner pair of the converging lenses, the first wavelength light being incident on the reflection pair from the outer pair of the converging lenses and reflected by the outer reflection surface. Through the
A wavelength-multiplexed multi-core optical rotary joint, comprising: an interference film filter that reflects the light of the second wavelength incident on the reflector from the inner pair of the converging lenses. 2. Instead of providing the interference film filter between an outer reflection surface and an inner reflection surface of the reflector, the inner reflection surface of the reflector reflects the light of the first wavelength and the second reflection light.
The wavelength-multiplexed multi-core optical rotary joint according to claim 1, further comprising an interference film filter that transmits light of the wavelength.