JPH0443845Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical rotary joint for transmitting and receiving light between a rotating body and a fixed body.

[Prior Art] Various optical rotary joints have been proposed as means for transmitting optical signals from optical fibers in a fixed body to optical fibers in a rotating body. , and the optical fiber on the rotating side is held by a rotating system such as a bearing with a slight gap. (For example, Utility Model Application Publication No. 58-13509) (2) Alternatively, lenses are provided at the ends of opposing optical fibers to expand the diameter of the light beam, alleviate mutual optical axis misalignment, and rotate the fibers via bearings. (for example, Japanese Patent Application Laid-open No. 57-100407), or one that aligns the integrated optical fiber and collimating lens with screws to reduce processing accuracy and assembly accuracy (for example, Japanese Patent Application Laid-Open No. 59-94726). be.

However, when using a single mode fiber (hereinafter referred to as SM fiber) with a core diameter of 8 to 10 μm in a rotary joint, the fiber facing type described in (1) above, the misalignment of the ball bearing that drives the rotation is at the highest level. However, it is 3.5 to 4 μm, and the eccentricity of the fiber holding ferrule is 1 to 2 μm.
With an eccentricity of 5 μm, when these are placed facing each other and rotated, there is a 50% variation in core area, resulting in an insertion loss of 5 to 6 dB, including a rotational variation of at least 3 dB.

Furthermore, when the collimating lens described in the previous item (2) is used, the optical axis deviation is significantly alleviated, but the optical axis deviation between the collimating lens and the SM fiber has the same characteristics as in the previous item (1). Also, as shown in Figure 3, angular misalignment between collimating lenses increases loss.
To keep it within 1 dB, the axis misalignment is as gentle as 40 μm, but the angular misalignment needs to be less than 0.07 degrees.
An adjustment mechanism for the SM fiber is also required, which increases cost.

SUMMARY OF THE INVENTION An object of the present invention is to provide a single-core optical rotary joint that solves the problems of the prior art described above and can significantly reduce loss between optical fibers and loss during rotation.

[Means for solving the problem] The gist of the present invention is to align the collimating lens and the SM fiber, and to simultaneously adjust the angular misalignment and axial misalignment between the rotating and stationary optical fiber collimators. , an optical fiber collimator with a convex spherical surface and a ring in line contact with the convex spherical surface are installed, and YAG
Laser welding or solder fixation is used to significantly reduce insertion loss such as axial misalignment and angular misalignment between opposing SM fibers.

[Example] In FIG. 1, the left end of the holder 4a with a convex spherical seat has a collimating lens 8 facing the optical fiber 6.
The right end forms a pigtail type fixed side optical fiber collimator 4 which is terminated to a ferrule 21, and the ferrule side is attached to a receptacle 19 installed in a receptacle holder 17 with a set screw 23. Holder 4 with convex spherical seat
A conical ring 10 is inserted between a and the fixed body 2. A ball bearing 13 and a V ring 12 are provided between the fixed body 2 and the rotating body 3, and a ball bearing 14 is also provided between the outer periphery of the rotating body 3 and the fixed flange 1.
is intervening. A rotation stopping plate 11 for stopping the rotation of the fixed body 2 is screwed to the fixed flange 1. A pigtail type rotary-side optical fiber collimator 5 formed by a collimating lens 9, an optical fiber 7, a holder with a convex spherical seat 5a, and a ferrule 22 is installed on the rotating body 3 via a conical ring 10, and the ferrule 22 holds a receptacle. body 18
A set screw 24 is attached to the receptacle 20 attached to the
It is fixed at

Figure 3 shows the axis misalignment between SM fiber collimators.
Shows angular deviation characteristics. 1dB loss fluctuation during rotation
Considering the following, if the axis misalignment is 40 μm, the angular misalignment needs to be 0.07 degrees or less. In FIG. 1, a holder 5a with a convex seat incorporating a collimating lens 9 and a fiber 7, which have been aligned and fixed in advance, is pressed against the rotating body 3 through a conical ring 10 and rotated around the fixed body 2, resulting in an angular deviation of 0.07 degrees. As shown in Fig. 2, the abutting parts of the holder 5 and the conical ring and the rotating body 3 and the conical ring 10 are welded using, for example, a YAG laser beam. At this time, θb must be 90° or more. If there is a line contact, the positional deviation during welding will be small, and if θc is 90°C or less, the laser beam can be irradiated from a direction with little positional deviation. in this case,
Since the light beam emitted from the rotating collimator 5 is not necessarily parallel to the rotation axis of the rotating body 3, the fixed collimator 4, which is composed of a collimating lens 8, an optical fiber 6, and a convex spherical seat holder 4, also has a conical ring 1.
0, the angle and axis are aligned in accordance with the output beam of the rotating side collimator 4, and as before, the abutment surface of the convex spherical seat holder 4a and the conical ring 10,
For example, the abutting surface of the conical ring 10 and the fixed body 2 is
Irradiate it with YAG laser light and weld it in place. Fixed body 2
When a V-ring made of an elastic material such as rubber is inserted between the outer circumferential surface of the rotating body 3 and the inner circumferential surface of the rotating body 3, the
This prevents oil, dirt, moisture, etc. from getting into the bearing.

The outer side of the rotating body 3 is held via a bearing 14 to a fixing flange 1 for fixing the present rotary joint. The fixed body 2 is held loosely (with a slight play) by the rotation stop plate fixed to the fixed flange 1, and even if the rotational torque to the rotating body 3 applies a force in the direction of shifting the optical axis, this The backlash has the effect of absorbing the force that shifts the optical axis. Furthermore, even if an abnormal force that bends the fixed flange 11 is applied when installing the optical rotary joint to the relevant equipment, if the bearing 14 is fixed loosely, the above-mentioned backlash will prevent this force from being applied to the optical axis of the collimator. Don't go so far as to shift it. Furthermore, by incorporating the receptacles 19 and 20 into this rotary joint, optical signals can be easily connected to the fixed body 2 and the rotary body 3 using optical connectors.

Note that oil with a buckling rate greater than 1.0 (matching oil) is placed inside the conical ring 10 and the fixed body 2.
25 and sealed with the V ring 12, it becomes a completely sealed type, and an optical rotary joint can be constructed that prevents water from entering from the outside even under ultra-high water pressure such as in a deep sea basin.

[Effects of the invention] As explained above, the optical rotary joint of the invention can adjust and fix the angular misalignment and axial misalignment between the collimators of the rotating body and the fixed body with high precision, so it has the following remarkable effects: play.

(1) A single-core optical rotary joint of an SM fiber with a core diameter of about 10 μm can be constructed with low resistance loss and low rotational fluctuation.

(2) Since angular and axial misalignment can be adjusted, parts with low machining accuracy can be used, making it economical.

(3) Since the fixed body 2 and the fixed flange 1 are fixed with a gap in the radial direction as well (with play), torsional force or other force that shifts the optical axis acts on the rotating body 3. Also, since the bearing 14 is provided to loosen, the rotary body 3 and the fixed body 2 are tilted coaxially, so there is little loss fluctuation during rotation.

(4) The rotating body collimator and the fixed body collimator are fixed to the rotating body 3 and the fixed body 2 by laser welding or soldering, respectively, so they are stable even when installed in places with significant temperature changes or strong vibrations. You can get the following behavior.

[Brief explanation of the drawing]

FIGS. 1 and 2 are longitudinal sectional views showing an embodiment of the optical rotary joint of the present invention, and FIG.
FIG. 3 is an explanatory diagram showing changes in characteristics due to axial deviation and angular deviation of an SM fiber collimator. 1... Fixed flange, 2... Fixed body, 3... Rotating body, 4, 5... Holder with convex spherical seat, 6, 7...
Fiber, 8, 9... Rod lens, 10... Conical ring, 11... Rotation stop plate, 12... V ring, 13, 14... Ball bearing, 15, 1
6... Bearing presser, 17, 18... Receptacle holder, 19, 20... Receptacle, 2
1, 22...Ferrule for fiber, 23, 24
...Set screw.

Claims (1)

[Scope of utility model registration request] In an optical rotary joint configured to perform optical transmission between an optical fiber provided on the rotation center axis of a rotating body and an optical fiber provided on a fixed body with their end faces facing each other, A holder with a convex spherical seat having a collimating lens is attached to each end of the optical fiber to form an optical fiber collimator. Between the fixed body and the convex spherical seat of the optical fiber collimator on the fixed body side, a ring is provided which makes an annular line contact with the convex spherical seat, and the rings and each of the parts in contact with the convex spherical seat are provided. An optical rotary joint characterized in that the contact part is welded or soldered.