JPH04323528A - Spun string tension measurement method for optical fiber - Google Patents

Abstract

PURPOSE:To measure the spun string tension of an optical fiber directly at high accuracy in a non-contact way. CONSTITUTION:An optical fiber 2 extracted from a string spunning device 2 is vibrated, and the optical fiber 2 can be seen as a vibrating chord. The vibration frequency of the chord is a function of tension, and by detecting the vibration frequency, the tension is calculated. Since the vibration frequency of the optical fiber 2 can be determined by measuring the position of the optical fiber 2 in a non-contact way, a problem of degraded intensity due to the contact to an uncoated optical fiber can be avoided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring spinning tension of an optical fiber.

0002

[Prior Art] The spinning tension of an optical fiber is a factor that greatly affects the refractive index distribution of the optical fiber.
This is one of the important manufacturing conditions in controlling the characteristics of optical fiber.

Conventionally, the spinning tension of this optical fiber is
As shown in FIG. 2, measurements are taken on a resin-coated optical fiber, and then the tension of the optical fiber itself is estimated. Adopting this indirect measurement method is
This is because if a tool for tension measurement or the like is brought into contact with an optical fiber that is not coated with resin, there is a risk of mechanical strength deterioration.

[0004] In the optical fiber spinning process, as shown in FIG. 2, an optical fiber preform 1 made of transparent glass is heated and melted in a spinning device 4, and an optical fiber 2 is drawn out and spun in the form of a fine thread. Immediately thereafter, the optical fiber is passed through a resin bath of a coating device 5 to be coated with a resin, thereby forming a resin-coated optical fiber 3. Therefore, conventionally, the tension of the resin-coated optical fiber 3 is measured by winding it around the drum of the tension measuring device 6 at the stage of the resin-coated optical fiber 3, and the tension borne by the resin is subtracted from the measured value. The spinning tension of the optical fiber 2 is estimated.

[0005]

[Problem to be Solved by the Invention] However, it is not possible to use an indirect measurement method in which the spinning tension of the optical fiber is estimated by subtracting the tension due to the resin from the measured tension value of the resin-coated optical fiber as in the past. , there is a problem of poor measurement accuracy. That is, since the tension borne by the resin easily changes depending on the viscosity and pressure of the resin, the feed speed in the linear direction, etc., accuracy cannot be improved.

[0006] This invention makes it possible to measure the spinning tension of an optical fiber with high accuracy by directly measuring the tension of the optical fiber in a non-contact manner before it is coated with a resin. The purpose is to provide a measurement method.

[0007]

[Means for Solving the Problems] In order to achieve the above object, in the optical fiber spinning tension measurement method of the present invention, the optical fiber drawn out from the spinning device is stretched between the next coating device. By focusing on the fact that it is thought to be a string, and by detecting its vibration, the spinning tension can be directly determined.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. In FIG. 1, an optical fiber preform 1 made of transparent glass is heated by a spinning device 4 to be in a molten state, and an optical fiber 2 is drawn out from there in the form of a fine thread, thereby being spun. The optical fiber 2 spun in this manner is immediately passed through a resin bath of a coating device 5, thereby being coated with a resin to become a resin-coated optical fiber 3.

[0009] Here, the optical fiber 2 between the spinning device 4 and the coating device 5 vibrates in the transverse direction by being sent in the linear direction (see dotted line). In this case, the optical fiber 2 can be considered to be a string stretched between the spinning device 4 and the coating device 5. The reference vibration frequency ω of the string is expressed by the following equation 1.

[Equation 1] However, L is the length of the string, that is, the distance between the spinning device 4 and the coating device 5 here, and c in Equation 1 is expressed by Equation 2.

[Equation 2] In Equation 2, T is tension and ρ is linear density. Therefore, from these equations 1 and 2, the following equation 3 is derived, and the tension T can be determined from this equation.

[Math 3]

In this embodiment, as shown in FIG. 1, a position detection device 7 is used to detect the position of the optical fiber 2 during vibration. This position detection device 7 detects the lateral position of the optical fiber 2 using, for example, a laser beam, and detects the position of the optical fiber 2 at a sampling period of, for example, about 200 times/second. Outputs a position signal. This position signal is transmitted to the data processing device 8
The optical fiber 2 is sent to a fast Fourier transform (FFT), and the vibration frequency of the optical fiber 2 is determined. Then, the tension is calculated from the measured vibration frequency using Equation 3 above.

[0011] When we actually measured the spinning tension of the optical fiber in this way, it matched well with the data measured using a conventional contact-type tension measuring device without coating with resin, confirming that highly accurate measurements can be made. did it. The accuracy was approximately ±3%.

[0012] As the position detection device 7 for the optical fiber 2, devices other than those using a laser beam can be used, and the vibration frequency can be determined using a configuration other than the configuration in which the vibration frequency is determined from the measured position. You can also do it.

[0013]

[Effects of the Invention] As described above with respect to the embodiments,
According to the optical fiber spinning tension measuring method of the present invention, the tension of the optical fiber being spun can be directly measured with high precision, and it can be measured without contact. Strength deterioration can be avoided.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional example.

[Explanation of symbols]

1 Transparent glass optical fiber base material 2
Optical fiber 3 Resin coated optical fiber 4
Spinning device 5 Coating device 6 Contact type tension measuring device 7
Position detection device 8 Data processing device

Claims (1)

[Claims] 1. A method for measuring spinning tension of an optical fiber, which comprises detecting the vibration frequency of an optical fiber drawn out from a spinning device and calculating the tension from the vibration frequency.