JPH04349151A - Optical fluoride fiber - Google Patents

Abstract

PURPOSE:To obtain optical fluoride fibers capable of optical amplification at 1.30mum wavelength and having high gain. CONSTITUTION:An optical fluoride fiber of claim 1 uses fluoride glass contg. BeF2 and Pr as at least the material of the core. An optical fluoride fiber of claim 2 contains >=60mol% BeF2 in the fluoride glass of the claim 1. An optical fluoride fiber of claim 3 contains Al in the fluoride glass of the claim 2. The optical fluoride fiber of the claim 1 has a compsn. of the core consisting of >=91mol% BeF2, <=2mol% PrF3 and <=7mol% AlF3. This optical fluoride fibers are fibers capable of optical amplification at 1.30mum and having high gain.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluoride optical fiber for optical amplifiers used primarily in relay sections of optical communication systems.

0002

2. Description of the Related Art An optical communication system is composed of a light emitting section, a relay section, and a light receiving section, which are connected by optical fibers. The relay section compensates for transmission loss and pulse spread when the transmitted signal light propagates through the fiber.
Conventionally, the configuration was such that signal light was once converted into an electrical signal and compensated, and then converted into signal light using a semiconductor laser. However, this relay section has the drawbacks of being extremely complex and expensive. Recently, attempts have been made to fabricate a fiber-type optical amplifier in which a rare earth element is used as a light emitting source and doped into a host glass, thereby directly amplifying signal light with a wavelength of 1.3 or 1.55 μm. ing.

0003

[Problem to be solved by the invention] However, 1.3
Nd-doped ZBLAN (ZrF4
-BaF2 -LaF3-AlF3 -NaF) type fluoride glass can amplify signal light of approximately 1.33 to 1.34 μm, but the 1.30 μm wavelength actually used in optical communications
There was a problem that a signal light of 1.31 μm could not be amplified.

0004

OBJECTS OF THE INVENTION An object of the present invention is to realize a fluoride optical fiber that can amplify light with a wavelength of 1.30 μm, which is actually used in optical communications, and has a higher gain.

[0005]

A fluoride optical fiber according to claim 1 of the present invention has at least a core made of fluoride glass containing beryllium fluoride (BeF2) and praseodymium (Pr). The fluoride optical fiber according to claim 2 of the present invention is characterized in that the fluoride glass according to claim 1 contains 60 mole percent or more of BeF2. The fluoride optical fiber according to claim 3 of the present invention is characterized in that the fluoride glass according to claim 2 contains aluminum (Al). In the fluoride optical fiber according to claim 4 of the present invention, the core composition is BeF2 (91 mole percent or more) + PrF3
(2 mole percent or less) + AlF3 (7 mole percent
cent or less). As a result of intensive research prior to the development of the fluoride optical fiber of the present invention, the inventors of the present invention found that by using beryllium fluoride (BeF2) glass doped with praseodymium (Pr), light at 1.30 μm was produced. We have discovered that amplification is possible. FIG. 3 shows the results of investigating the relationship between the BeF2 concentration in this glass and the wavelength that can be amplified, using a composition that yields a transparent Pr-doped glass without crystallization. ■■■■ of the same figure
(2) corresponds to the optical fibers having compositions (1) to (2) shown in Table 1.

[0006]

[Table 1]

As is clear from FIG. 3, when the BeF2 concentration is less than 60 mol percent (mol%), the wavelength that can be amplified shifts to the longer wavelength side due to the influence of other added cations. . The amplification wavelength is 1.
The reason for the shift from 30 to 1.31 μm or more is expected to be that cations other than Be in the glass affect the electronic level of Pr. Therefore, in order to amplify light at 1.30 μm, the BeF2 concentration is preferably 60 mol% or more.

[0008] The inventors of the present invention have conducted further research to increase the gain of the fluoride optical fiber of the present invention, and have found that adding Al may cause the Pr in the glass to be further dispersed, increasing the gain. Thought. As a result of confirming this through experiments,
As will be explained in detail in the examples below, an appropriate amount of AlF
By using BeF2 doped with PrF3 and PrF3, a high gain fiber could be obtained. As a result of investigating the composition of glass from which high-gain fibers can be obtained, the appropriate region is BeF2 (91 mol% or more) + PrF3
(2 mol% or less)+AlF3 (7 mol% or less). The gain increased as the PrF3 concentration in the glass increased, but it remained almost constant at 2 mol% or more. Considering that Pr is expensive, it is preferred industrially that the PrF3 concentration be 2 mol% or less. The reason why AlF3 is 7 mol % or less is that if more than this is added, the glass frequently becomes cloudy during dissolution and cooling. On the other hand, clad glass is made of Be with a suitable amount of AlF3 added together with PrF3.
F2, single BeF2, or other materials may be used. However, since light travels through the optical fiber, the material needs to have a refractive index smaller than that of the core glass.

[0009]

[Example 1] BeF2, AlF3 and PrF3 were mixed as raw materials, melted and rapidly cooled, and the composition was 94.0 mo.
1%BeF2 +5.5mol%AlF3 +0.5m
A glass lump for a core of ol%PrF3 was produced. This glass lump was crushed, remelted in an Ar atmosphere, and poured into a carbon mold to produce the core rod 1 shown in FIG. 1. This core rod 1 was drawn as shown in FIG. 1, and the outer periphery of the core rod 1 was coated with an ultraviolet curing resin 4 for cladding using a die 3 to produce a fiber 15 having an outer diameter of 125 μm. In FIG. 1, 2 is an electric furnace, 5 is an ultraviolet irradiation curing device for curing the ultraviolet curable resin 4 for cladding by irradiating it with ultraviolet rays, and 6 is a capstan.

0010

[Example 2] The composition was determined to be 99.9% by the same method as in Example 1.
A glass lump for a core containing 5 mol% BeF2 + 0.5 mol% PrF3 was prepared. The core glass lump produced in this way is crushed, remelted in an Ar atmosphere, and then
A core rod was produced by pouring it into a Bonn mold. This was drawn in the same manner as in Example 1, and the outer diameter was 125 μm.
A fiber was fabricated.

[0011]

[Comparative example] Using the same method as in Example 1, the composition was 500pp.
m Nd-doped ZBLAN (ZrF4-BaF
A glass lump for a core of 2-LaF3-AlF3-NaF)-based fluoride glass was produced. This core glass lump was crushed, remelted in an Ar atmosphere, and poured into a carbon mold to produce a core rod. Example 1
A fiber (conventional fiber using ZBLAN-based fluoride glass) having an outer diameter of 125 μm was produced by drawing in the same manner as described above. The optical amplification characteristics of the three types of fibers produced in Examples 1 and 2 and Comparative Example were measured using the measuring device shown in FIG. 2. By the way, 7 in the same figure is 1.064μm
Excitation light source, 8 is a 1.3 μm light source, 9 is a lens, 10
is a half mirror, 11 is a lens, 12 is an example 1, 2,
A fluoride glass optical fiber manufactured in a comparative example, 13 is a spectrum analyzer. As a result, as shown in Table 2, at 1.30 μm, the fiber of the comparative example could not obtain a gain, whereas the fiber of Examples 1 and 2 had a gain of 4 to 4 μm.
A gain of 13 dB could be obtained.

0012

[Table 2]

[0013]

[Effect of the invention] The fluoride optical fiber of the present invention has a 1.30
Optical amplification in μm is possible, and the gain is large.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a wire drawing device.

FIG. 2 is a schematic diagram of a fiber amplification characteristic measuring device.

FIG. 3 is an explanatory diagram showing the relationship between BeF2 concentration in glass and amplification wavelength.

[Explanation of symbols]

1 Glass rod for core 2 Electric furnace 3 Dice 4 Resin 5 Ultraviolet irradiation curing device 6 Capstan

Claims (4)

[Claims] Claim 1: At least the core is beryllium fluoride (
A fluoride optical fiber comprising a fluoride glass containing BeF2) and praseodymium (Pr). 2. The fluoride optical fiber of claim 1, wherein said fluoride glass contains 60 mole percent or more of BeF2. 3. The fluoride glass is made of aluminum (
The fluoride optical fiber according to claim 1 or claim 2, characterized in that the fluoride optical fiber contains Al). 4. The fluoride optical fiber according to claim 3, wherein the composition of the core is BeF2 (91 mole percent or more) + PrF3 (2 mole percent or less) + AlF3 (7 mole percent or less).