JPS5935034A - Preparation of side pit type optical fiber having constant polarized wave - Google Patents

Abstract

PURPOSE:To make it possible to carry out easily the joining, by forming protruding ridges or grooves on the outer peripheral surface of an optical fiber by adjusting the internal pressure applied to hole parts in drawing a preform of the side pit type optical fiber having constant polarized waves. CONSTITUTION:A pair of holes (2a) and (2b) are provided in a core part in the long direction in a process for preparing a preform, which is then drawn while applying an internal pressure to the hole parts (2a) and (2b) not to collapse the holes (2a) and (2b) to prepare a side pit type optical fiber having constant polarized waves and the holes (2a) and (2b) on both sides of the core 1. The internal pressure applied to the hole parts (2a) and (2b) is set at a pressure for expansion or contraction to form protruding ridges (3a) and (3b) or grooves (4a) and (4b) on the outer peripheral surface in the long direction of the drawn optical fiber. In joining the optical fibers, a pair of the optical fibers are butted to make the protruding ridges (3a) and (3b) or grooves (4a) and (4b) in agreement with each other and further the plane of polarization of each other. The joining is then carried out by welding, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a fixed bit polarization optical fiber.

Polarization-controlled optical fibers are being considered for application as sensors in interferometric systems and also in communication systems.

When used as a sender, a relatively short optical fiber is used, but when used for communications, a long optical fiber is used to take full advantage of the characteristics of a fixed polarization optical fiber. become.

However, to obtain a long optical fiber, several optical fibers must be connected.

Furthermore, even in the event of an accident in which the optical fiber is cut, the optical fiber must be connected.

As described above, the connection of optical fibers is required in various cases, but in the case of a constant polarization optical fiber, unlike a normal optical fiber, it is necessary to make the mutual polarization planes coincide with each other for connection.

In order to facilitate the matching of the plane of polarization, one step has conventionally been adopted in which the direction of polarization is represented by the outer shape of the optical fiber.

In other words, using an elliptical clad optical fiber, the outer shape of the optical fiber is rubbed into an ellipse, a rectangle, or a rhombus.

However, in order to make the outer shape of the optical fiber into the above shape, it is necessary to add the same shape to the optical fiber in advance at the preform stage, but such addition is very time-consuming. .

Moreover, in order to maintain the pressurized shape of the preform even after drawing, the drawing humidity must be increased by F, but this increases the transmission loss of the optical fiber.

The present invention solves the above problem by forming protrusions or grooves on the outer peripheral surface of the optical fiber by adjusting the internal pressure applied to the hole when drawing a preform of a side pit type polarization constant optical fiber. To explain this with reference to the embodiment shown in the drawings, the optical fiber shown in FIG. 1 has a pair of holes (21a, 21a, (2) It is a side-hole type redundant polarized optical fiber with b, and in order to make such an optical fiber kH11i, a pair of holes are formed along the length of the core 1flll at the preform stage ('l, When drawing the line Ic, the four soliforms are drawn.
Is there internal pressure in the hole to prevent it from soaking? i: ll1l
E'5) We are drawing lines.

If the internal pressure is appropriate, holes f21 a and f21 b with circular cross sections can be obtained as shown in the figure.
Figure 2 shows the optical fiber after it has been drawn while applying a pressure greater than the internal pressure applied to obtain the optical fiber shown in Figure 1.Due to the internal pressure, the hole swells and the optical fiber becomes A pair of protrusions t31 a on the middle and outer peripheral surfaces along the length direction
, f31 b are formed.0 Figure 3 shows the optical fiber after drawing with the applied pressure lower than the above-mentioned appropriate internal pressure, contrary to the case of Figure 2, and the holes are The part is recessed and contains many optical fibers.
A pair of grooves (4)a and (4)b are formed on the outer peripheral surface along the direction.

In order to connect such optical fibers to each other, after a pair of optical fibers are butted together, one of them is rotated 14 times, and the protrusions (3)a, (3)b or groove phases rL are aligned with each other. If so, the polarization plane of the house will match.

After this, connection is made by appropriate means such as welding.

Here, to describe a more specific example: 1. Outer diameter 20 mm with a pair of holes located at symmetrical positions I with respect to part A.
A single mode preform was drawn at a temperature of 2050°C and a drawing speed of 30 m' while applying internal pressure to the hole.

At an internal pressure of 40 to 60 MH20, a constant polarization optical fiber as shown in FIG. 3 was obtained, and at an internal pressure of 70 to 100 MH20, a constant polarization optical fiber as shown in FIG. 2 was obtained.

In addition, when the internal pressure is below 40+a+820, the hole is completely submerged.
When the internal pressure exceeded 100mm820, the foam burst.

When the thus obtained constant polarization optical fiber was inserted into a glass pipe (5) as shown in Figure 4, aligned, and connected by welding +C, the connection loss was the same as that of a normal single mode optical fiber connection. The polarization plane was well preserved.

As described above, in the present invention, C is drawn while applying an internal pressure different from the appropriate pressure to the hole formed in the preform,
Long length of optical fiber after drawing.

Since the protrusions or γ7+'/ are formed on the outer circumferential surface along the direction, when connecting the optical fibers to each other, it is only necessary to match the protrusions 47- or grooves with each other, so that the connection can be performed mechanically. Easy on-site connection.

Further, the holes are simply formed at the preform stage, and forming the holes is easier than forming the outer shape into an ellipse or the like, thus saving time and effort.

In addition, there is no need to adjust the drawing temperature, and the drawing temperature can be kept the same as the spinning temperature of ordinary optical fibers, without increasing transmission loss.

[Brief explanation of drawings]

Figure i1 is a cross-sectional view of a conventional polarization-controlled optical fiber with appropriate internal pressure, Figures 2 and 3 are cross-sectional views of a polarization-controlled optical fiber obtained by the method according to the present invention, and Figure 4 is a cross-sectional view of a polarization-controlled optical fiber obtained by the method according to the present invention. and FIG. 4 is a perspective view of a glass pine used when connecting the optical fibers shown in FIG. 3. [31a, (3113... protrusion (4) a, +
411) ...Mizotoku 1)'[Applicant's agent Patent attorney Tsukifuji Ashi Figure 1 Figure 21y! J Figure 3 @ 4 N

Claims (1)

[Claims] 17. In a method for controlling a side-bit type polarization-controlled optical fiber, in which a pair of holes are provided along the 1,000-direction direction of the core length of the reform, and drawing is performed while applying a predetermined internal pressure to the holes, A fluid bit type constant deflection device characterized in that the internal pressure is set to a pressure that causes the hole to expand or contract during drawing, and a protrusion or groove is formed on the outer periphery along the longitudinal direction of the optical fiber after drawing. Method of manufacturing wave optical fiber.