JP2001208923A - Image fiber and method for reducing its skew - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make improvable the transmission speed even if a bending part exists by reducing a skew caused by bending. SOLUTION: The skew generating in the bending part is reduced by giving a twist in an image fiber 1 having a structure in which plural cores are embedded in a clad.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image fiber having a structure in which a plurality of cores are embedded in a clad, and to a method for reducing skew of an image fiber for reducing skew generated in a bent portion of the image fiber. .

[0002]

2. Description of the Related Art FIG. 4 is a diagram showing a cross section of an image fiber. The image fiber 1 includes a screen 4 forming a main body and a jacket 5 on the outer periphery thereof. The screen 4 has a structure in which a large number of cores (waveguides) 4a are embedded in a clad (base material). This image fiber 1 has each core 4
Since a can independently transmit light, it is used as an image transmission path for an endoscope or the like.

[0003] Further, studies are being made to utilize the image fiber 1 as a two-dimensional optical data transmission path. By transmitting an optical signal from a two-dimensional laser diode array directly in a two-dimensional state, high-density, high-throughput optical data transmission is aimed at.

FIG. 5 is a diagram showing how an optical signal from a two-dimensional laser diode array is transmitted through an image fiber. In the figure, a two-dimensional laser diode array 2
Signal 3 is simultaneously propagated by the image fiber 1 as a parallel transmission path, but a difference occurs in the propagation time of the optical signal 3 due to non-uniformity of parameters of the image fiber 1 such as a refractive index and a core diameter. Would. Such a maximum value of the propagation time difference of the optical signal 3 is called skew.

[0005] If the skew is large, it becomes impossible to synchronize the signals on the receiving side. Therefore, the pulse width of the optical signal 3 needs to be sufficiently larger than the skew. That is, the skew of the parallel transmission line is a factor that limits the synchronous transmission speed of the transmission line. Therefore, in the two-dimensional optical data transmission by the image fiber 1, the skew is reduced by making the parameters of the image fiber 1 uniform, and high-speed data transmission is realized.

[0006]

However, in the two-dimensional optical data transmission using the conventional image fiber 1 as described above, the skew increases when the image fiber 1 is bent, and the transmission speed is reduced. was there.

FIG. 6 is a view showing how skew is generated by bending an image fiber. When the image fiber 1 is bent as shown in the figure, the outer core of the bent portion in the screen 4 of the image fiber 1 expands, the inner core compresses, and as a result, propagates through the outer core. The light propagation distance is longer than that on the inner peripheral side.
In addition, the refractive index changes in each core due to the photoelastic effect according to the deformation. Due to these factors, the optical signal 3 propagating on the outer peripheral side of the bent portion becomes the optical signal 3 propagating on the inner peripheral side.
Arrival time to the receiving side is later than this, which causes skew.

As described above, if the image fiber 1 has a bent portion, the skew increases, and therefore, the transmission speed in the parallel transmission line is suppressed.

[0009] The present invention has been proposed in view of the above,
It is an object of the present invention to provide an image fiber capable of reducing the skew caused by bending and improving the transmission speed even if there is a bent portion, and a method of reducing the skew thereof.

[0010]

In order to achieve the above object, according to the first aspect of the present invention, in an image fiber having a structure in which a plurality of cores are embedded in a cladding, the image fiber is twisted and generated at a bent portion. The skew is reduced.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, an integral multiple of the twist pitch is equal to the length of the bent portion. .

According to a third aspect of the present invention, in addition to the configuration of the first aspect of the present invention, the image fiber is fixed in a twisted state.

According to a fourth aspect of the present invention, in addition to the configuration of the first aspect, the image fiber is pre-twisted.

Further, according to a fifth aspect of the present invention, there is provided an image fiber skew reduction method for reducing skew generated in a bent portion of an image fiber having a structure in which a plurality of cores are embedded in a clad. It is characterized in that the skew generated at the bent portion is reduced by applying torsion.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, a first embodiment will be described with reference to FIG.

FIG. 1 is a schematic diagram for explaining an image fiber of the present invention. In the drawing, the image fiber 1 is twisted at a bent portion, and both ends of the bent portion are fixed by a fixing jig 6 to fix the twist.
Is bound by. By twisting the bent part in this way, the outer peripheral side of the bent part moves to the inner peripheral side, and then becomes the outer peripheral side again, in this way, the propagation distance of light propagating through each core is made uniform, and The photoelastic effect in each core is also made uniform. Therefore, the skew generated at the bent portion can be reduced, and the transmission speed can be improved even if the bent portion exists.

In FIG. 1, the image fiber 1 has 2
Rotational torsion is applied, and twice the pitch of the torsion generated by the torsion corresponds to the length of the bent portion. As described above, when the integral multiple of the twist pitch becomes equal to the length of the bent portion, the skew due to bending can be completely canceled. However, even when such a condition is not completely satisfied, the skew is sufficiently reduced.

FIG. 2 is a schematic view showing a second embodiment of the present invention. In the above-described first embodiment, in order to apply a twist to the image fiber 1, both ends of the bent portion are restrained by the fixing jigs 6. However, the image fiber 1A according to the second embodiment has Twisting is applied in advance in the manufacturing stage, and the twisted state is maintained in a free state, and therefore, a fixing jig for restraining is unnecessary.

FIG. 3 is a diagram showing an example of a method for manufacturing an image fiber according to the second embodiment. The image fiber 1A according to the second embodiment can be manufactured by a drawing process as shown in the figure. That is, the pre-rod 8 is in a state in which a large number of cores 4a are wrapped in the clad preform heated in the heating furnace 9, and in the drawing step, the image fiber 1A
Is drawn and wound on a take-up drum 10. At the time of the take-up, the pre-rod 8 or the take-up drum 10
Is rotating. In accordance with this rotation, the image fiber 1 </ b> A capable of holding a twisted state in a free state is sequentially wound around the winding drum 10. And the image fiber 1A twisted in advance in this way
With the use of, it is possible to impart a twist to the bent portion without constraining. Therefore, similarly to the case of the first embodiment described above, it is possible to reduce the skew generated in the bent portion, and Even if there is a portion, the transmission speed can be improved.

[0020]

Since the present invention has the above-described configuration,
The following effects can be obtained.

According to the first and fifth aspects of the present invention, the torsion is applied to the bent portion, so that the outer peripheral side of the bent portion moves to the inner peripheral side, and then becomes the outer peripheral side again.
In this way, the propagation distance of the light propagating through each core is made uniform, and the photoelastic effect at each core is also made uniform. Therefore, the skew generated at the bent portion can be reduced, and the bent portion can be removed. However, the transmission speed can be improved.

According to the second aspect of the invention, since the integral multiple of the twist pitch is made equal to the length of the bent portion, the skew due to bending can be completely canceled.

Further, in the invention according to the fourth aspect, since the image fiber is twisted in advance, it is possible to impart a twist to the bent portion without restraining the image fiber, thereby reducing the skew at the bent portion. Thus, the transmission speed can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining an image fiber of the present invention.

FIG. 2 is a schematic diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram illustrating an example of a method for manufacturing an image fiber according to a second embodiment.

FIG. 4 is a diagram showing a cross section of an image fiber.

FIG. 5 is a diagram illustrating a state in which an optical signal from a two-dimensional laser diode array is transmitted through an image fiber.

FIG. 6 is a diagram illustrating a state in which skew is generated by bending an image fiber.

[Explanation of symbols]

 Reference Signs List 1 image fiber 1A image fiber 2 two-dimensional laser diode array 3 optical signal 4 screen 4a core 5 jacket 6 fixing jig 8 pre rod 9 heating furnace 10 winding drum

Claims (5)

[Claims] 1. An image fiber having a structure in which a plurality of cores are embedded in a clad, wherein skew generated in a bent portion is reduced by applying a twist. 2. The image fiber according to claim 1, wherein an integral multiple of the twist pitch is equal to the length of the bent portion. 3. The image fiber according to claim 1, wherein the image fiber is fixed in a twisted state. 4. The image fiber according to claim 1, wherein the image fiber is twisted in advance. 5. An image fiber skew reduction method for reducing skew generated in a bent portion of an image fiber having a structure in which a plurality of cores are embedded in a clad, wherein the image fiber is twisted by applying a twist. A method for reducing skew of an image fiber, comprising: