JPH0211532B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method in which, when drawing an optical fiber base material at a constant speed, it is twisted before being covered with a coating material, and by covering it with the coating material, the circularly polarized light generated by the twisting is The present invention relates to a method of manufacturing an optical fiber for maintaining single circular polarization, which is characterized by fixing birefringence for a mode within the fiber.

Conventionally, as a manufacturing method of a single mode optical fiber that maintains a single polarization, an optical fiber base material 01 as shown in FIG. 04 is mechanically polished, covered with a glass tube different from the base material, and then drawn by a drawing device to produce an optical fiber with an elliptical core or stress birefringence, or a core as shown in Figure 2. - Connect the base material 11 for the cladding and the stress applying rods 12 and 13 to the jacket tube 14.
There are methods of manufacturing optical fibers that are drawn using a drawing machine after being inserted into the fiber to give it stress birefringence or an elliptical core/cladding. Therefore, there are disadvantages in that loss increases when connecting the fibers and the connection becomes unstable.

In order to eliminate this drawback, the present invention has been developed by twisting a normal single-mode fiber base material before applying a coating material to it, and then applying the coating material to reduce the stress caused by the twisting. By fixing the fiber within the fiber, the aim is to obtain a fiber that does not lose the axial symmetry of the refractive index distribution within the fiber and has improved retention of the circularly polarized light mode.

The present invention will be explained in detail below with reference to the drawings.

FIG. 3 is a diagram showing an embodiment of the present invention,
An optical fiber base material 1 is supported by a chuck 2,
The optical fiber 5 is gradually inserted into the electric furnace 3, heated and melted by the heater 10, and spun into an optical fiber 5. This optical fiber 5 is sandwiched between rotating rolls 31 and 32, and forcedly sent out by both rotating rolls. The sent-out optical fiber is wound up by a winder 34 that can rotate in the direction of arrow 35 and wind up in the direction of arrow 36. The fiber deflection suppressing section 33 suppresses the deflection of the fiber. In this way, the optical fiber is connected to the rolls 31, 32 and the winder 3.
Twist is given between 4. This twisted optical fiber is subjected to a primary coating using a primary coater 6, and is further baked and sealed using an electric furnace 7 for drying the primary coat. Next, a coating material is applied using an overcoat device 8, and baking is performed using an electric furnace 9 for drying the overcoat. Use silicone or nylon as the coating material. By carrying out such a process, stress caused by twisting occurring in the optical fiber is fixed within the fiber. Specifically, 2 to 90 rotations per meter are applied to fix the birefringence due to stress within the optical fiber. In this way, the birefringence for the circularly polarized light mode is increased, the beat length for the circularly polarized light mode can be made 15 to 700 mm, and an optical fiber for holding a single circularly polarized light that can hold a single circularly polarized light is manufactured. can.

As explained above, when the optical fiber base material of the present invention is drawn at a constant speed, the optical fiber is twisted before being covered with the coating material, and by covering the optical fiber with the coating material, the stress caused by the twisting is absorbed into the fiber. The manufacturing method of optical fiber for maintaining a single circularly polarized light, which has enhanced birefringence for the circularly polarized light mode by fixing the optical fiber in , the transmission loss at a wavelength of 1.5 μm can be reduced to 0.2 dB/Km, and it can be manufactured continuously.
It is also possible to extend the length beyond Km.

By using a minute λ/4 plate, the optical fiber for maintaining single circularly polarized light manufactured by this manufacturing method can be converted into linearly polarized light immediately after exiting the fiber, making it suitable for long-distance optical transmission systems and submarine optical cable transmission systems. This is effective for increasing the coupling efficiency to over 99% in relay systems consisting of elements mainly having a slab structure, such as optical amplifiers, and suppressing fluctuations to less than ±0.1%. In the optical transmission system of In combination with
It has the advantage of being applicable as an important fiber that enables stable bonding.

[Brief explanation of drawings]

Figure 1 is a diagram showing the base material in the conventional manufacturing method and the shape of the base material after polishing, Figure 2 is an inserted view of the base material and stress applying rod in the conventional manufacturing method, and Figure 3 is the diagram showing the shape of the base material after polishing. FIG. 3 illustrates an example of a method. 01,02... Base material, 03,04... Polished side surface of base material, 11... Synthetic core/clad base material, 12, 13... Base material for stress application, 14... Jacket tube, 1... ...Base material for optical fiber, 2...Chick, 3...Electric furnace, 4...Capstan, 5
...Optical fiber, 6...Primary coater,
7...Electric furnace for drying primary coat, 8...
Overcoat device, 9... Electric furnace for overcoat drying, 10... Electric furnace heater, 31, 32...
Rotating roll, 33...Fiber runout suppressing section, 3
4... Winder, 35... Arrow indicating the rotation direction of the winder main body, 36... Arrow indicating the rotation direction of the winder drum.

Claims (1)

[Claims] 1 Optical fiber in which a rod-shaped optical fiber base material is gradually inserted into the furnace from one end of the furnace, heated and melted and spun to the required diameter, and the spun optical fiber is pulled out at a constant speed from the other end of the furnace. In drawing, the fiber before the primary coating is forcibly fed out while applying pressure with rollers from both sides, and the fiber is twisted before being wound up with a winder, and the twisted fiber is treated with urethane, For single circularly polarized light, which is characterized by maintaining a single circularly polarized light by coating the fiber with a coating material such as silicone or nylon to fix the birefringence for circularly polarized light caused by twisting within the fiber. Method of manufacturing optical fiber.