JPH0624799A - Production of fluoride glass preform for optical waveguide - Google Patents

Abstract

PURPOSE:To obtain the subject preform capable of getting high gain by the excitation with a low-power laser beam by repeating the crushing, melting and casting of a specific glass several times. CONSTITUTION:A ZBLAN-type fluoride glass having a composition of ZrF4- BaF2-LaF3-AlF3-NaF is incorporated with about 2,000ppm of praseodymium (Pr) and optionally about 8mol% of Pb and the mixture is melted and cast to form a glass for core, etc. The glass is crushed to powder having particle diameter of 100-500mum, melted and cast. The procedures are repeated once or more to obtain the objective fluoride glass preform for optical waveguide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical amplification optical waveguide (including an optical fiber) used mainly in a repeater section of an optical communication system.

[0002]

2. Description of the Related Art An optical communication system comprises a light emitting section, a relay section and a light receiving section, and an optical waveguide is connected between them. This repeater is for compensating the transmission loss and the spread of the pulse when the signal light to be transmitted propagates in the optical waveguide. Conventionally, the configuration has been such that the signal light is once converted into an electric signal and compensated, and then the semiconductor laser is compensated. Was used to convert to signal light. However, this method has a drawback in that it is expensive because the structure of the apparatus is extremely complicated. Therefore, recently, a rare earth element such as Pr was used as a light emitting source, and a host glass was doped with this to form an optical waveguide, and a wavelength was generated by this optical waveguide.
Attempts have been made to directly amplify signal light of 1.3 μm or 1.55 μm.

[0003]

However, although a single mode optical waveguide of ZBLAN glass doped with Pr, specifically PrF _3, for example, is capable of optical amplification at 1.3 μm, a high output laser is used. There is a problem that only a low gain can be obtained unless it is excited by using it. Specifically, in order to obtain a gain of about 10 dB at 1.3 μm, the wavelength is 1.
It is necessary to put excitation light of 500-900mW at 02μm into the core. This output can be achieved by using a titanium sapphire laser, but a general-purpose semiconductor laser (output about 100-
It is a value that cannot be achieved at 150 mW).

[0004]

[Object] An object of the present invention is to provide a method of manufacturing a base material for obtaining an optical amplification optical waveguide having a high gain of 1.3 μm even when excited by a low-power laser.

[0005]

[Means for Solving the Problems] The present invention relates to a mother glass of a fluoride glass optical waveguide by melting and casting a fluoride glass raw material containing Pr in a ZBLAN type fluoride glass having a composition mainly. In the method of manufacturing a material, the glass after melting and casting is crushed, and then, a series of steps of melting it again and casting again is repeated one or more times, specifically, an optical waveguide base material, specifically, It is characterized in that rod-shaped glass or a pipe is manufactured if necessary.

[0006]

The technical background that led to the discovery of the present invention will be described below. For 1.3 μm optical amplification, pumping with a laser having a center wavelength of about 1.02 μm is necessary considering the Pr electron level, but absorption at this wavelength is essentially small. However, if Pr in the glass efficiently absorbs energy, the gain should be improved even when pumping at a lower output. The reason why Pr does not absorb energy efficiently is thought to be the formation of Pr clusters in the glass, which is why the proportion of Pr that absorbs energy is considered to be low. Then, the step of crushing the glass and melting and casting again is repeated several times to produce the glass for the core, whereby Pr is uniformly dispersed in the glass. Then, high gain can be obtained even with low-power laser light.

[0007]

EXAMPLE Example 1 of the present invention will be described in detail below.
In order to obtain a ZBLAN glass containing 2000 ppm of Pr and 8 mol% of Pb, the raw materials were weighed, melted, rapidly cooled, and cast.
The core glass (total weight 50 g) thus obtained was powdered.
(The particle size is about 100 μm to 500 μm), melted and quenched again, and cast into a mold to produce a core rod having an outer diameter of 15 mm. After mechanically polishing the rod, it was heated and stretched in an inert gas, specifically nitrogen gas, to obtain a core rod having an outer diameter of 3 mm. Also, in order to lower the refractive index, ZBLAN glass doped with 50 mol% of hafnium (Hf) was melted and cast into a mold to make a rod with an outer diameter of 15 mm, which was punched with an ultrasonic drill and clad. Got a pipe for. A preform for a single mode type optical waveguide was produced by repeating the process of heating both at about 300 ° C. and integrating them with the rod for the core inserted in this pipe. This preform was drawn by a conventional method to obtain an outer diameter of 125 μm and a core diameter of 3.1 μ.
m, and a fiber type optical waveguide having a relative refractive index difference Δ3% was obtained. When the optical amplification characteristics of this optical waveguide were examined using the measurement system shown in FIG. 1, as shown in Table 1, the gain at a wavelength of 1.3 μm was 42 dB.

FIG. 1 shows an apparatus used for examining the optical amplification characteristic of this optical waveguide. Excitation light (wavelength: about 1.02 μm) from the titanium sapphire laser 1 is incident on the single mode dummy fiber 7a via the lens 2a, and on the other hand, signal light of 1.3 μm from the semiconductor laser 3 is input to the dummy fiber 7a.
It was incident on b and was multiplexed by using the coupler 4. This light was made incident on the optical waveguide of the present invention, that is, the fiber 5 using the lens 2b, and was measured by the spectrum analyzer 6. As a result, as shown in Table 1, at the wavelength of 1.3 μm,
A gain of 42 dB was obtained.

[0009]

[Table 1]

As Example 2, as in Example 1, the fluoride glass obtained by weighing, melting and quenching the raw materials was crushed into a powder, and then melted, quenched and cast again, that is, crushed, 10 steps of melting and casting
By repeating this, a core rod having an outer diameter of 15 mm was finally manufactured. This rod was combined with a clad pipe prepared in the same manner as in Example 1 to prepare a preform and draw it. When the gain of the obtained fiber type optical waveguide was measured by the measurement system shown in FIG. 1, it was 55 dB.

As a comparative example, a core glass having the same composition as in Examples 1 and 2 was prepared, and then a glass rod for core was prepared by simply melting and casting without crushing and remelting. In the following steps, the gain of the fluoride glass optical waveguide manufactured by the same method as in Examples 1 and 2 was 24 dB.

[0012]

According to the present invention, by crushing, remelting, and recasting ZBLAN glass several times in the process of manufacturing an optical waveguide, a high gain can be obtained mainly by pumping with a low-power laser. An optical waveguide can be obtained. That is, it is possible to obtain a fluoride glass optical waveguide that can obtain a higher gain even when excited by the same output.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an optical amplification characteristic measurement system.

[Explanation of symbols]

 1 Titanium sapphire laser 2 Lens 3 Semiconductor laser 4 Coupler 5 ZBLAN fiber 6 Spectrum analyzer 7 Dummy fiber

Claims (1)

[Claims] 1. A fluorine glass whose composition is mainly ZrF ₄ -BaF ₂ -LaF ₃ -AlF ₃ -NaF (ZBLAN) type by melting and casting a raw material, and a fluoride glass containing praseodymium (Pr). In the method for producing a compound glass optical waveguide preform, crushing the glass after melting / casting, and then repeating the series of steps of remelting / recasting once or more to produce the optical waveguide preform. A method for producing a fluoride glass optical waveguide base material, comprising: