KR20000027961A - Optical element using core in which erbium ion and thorium ion are added - Google Patents

Abstract

PURPOSE: An optical element using core in which erbium ion and thorium ion are added are provided to be suitable of a miniaturization by manufacturing an optical amplifier and an optical source having an optical band characteristic. CONSTITUTION: An optical pumping means is combined through a front WDM combiner(320) and a rear WDM combiner(322) located at both sides of a glass optical fiber(310). First and second optical pumps(330,332) for pumping an erbium ion and a thorium ion are installed to a front direction and a rear direction of the glass optical fiber(310). A first WDM combiner(340) and a second WDM combiner(342) combines pumping lights outputted from first and second optical pumps(330,332). First and second optical isolators(350,353) restrain a rear progressed reflective light.

Description

Optical device using core co-added with erbium ion and thulium ion

The present invention relates to an optical device, and more particularly, to an optical amplifier and a light source.

Currently, in the optical communication system, wavelength division multiplexing ("WDM") method is being studied as an important transmission method, and optical amplifier research is also actively conducted as an important component in this method. The characteristic of the optical amplifier required here is to have a wide gain band. To this end, research and development have been carried out in the following directions.

First, there is a method of using an EDFA (Erbium Doped Fiber Amplifier) based on silica glass, but having a conventional gain band and a long wavelength gain band simultaneously by combining two parallel EDFA stages having gains in different wavelength bands. .

Second, as A. Mori et al. Announced at the Optical Fiber Communication in 1997 under the title of "1.5 μm wideband amplification using tellurium-based EDFAs", low phonon energy is based on TeO ₂ , a heavy metal oxide glass. There is a method to have a gain band of 1530 to 1610 nm using.

Third, as a Raman amplifier using Stimulated Raman Scattering, which converts pump photons into a stoke shift band, there is a method of having an optical gain band by using a plurality of high output pumps.

In addition to the above three methods, research on hybrid optical amplifiers combining them is being conducted.

However, the research directions have disadvantages. In the first case, various optical elements such as optical fiber gratings, circulators, etc. must be included in the amplifier, and 980 nm and 1480 nm are also required for optical pumping. Multiple laser diodes are required.

In the second case, due to the different glass composition, the connection with the common single-mode fiber for communication made of silica is mechanical. Therefore, since the fusion splicing with the stable and proven general optical fiber is impossible, the mechanical reliability may be lowered.

In addition, in the third case, since a nonlinear effect is used in the operation of the amplifier, a strong pump strength of 1 W or more is required, and when the gain band is widened, a plurality of pumps emitting pumping light of various wavelengths with such intensity are required.

Accordingly, an object of the present invention is to provide an optical amplifier and a light source having a wide band characteristic while employing a relatively small number of optical elements.

Another technical problem of the present invention is to provide an optical amplifier and a light source capable of effectively amplifying or emitting light even when a pumping means having a relatively weak intensity is used.

1 is a schematic view showing an optical fiber structure used in an embodiment of the present invention;

2 is a graph showing the spectrum of back amplified self-luminescence of a silicon oxide glass fiber co-added with Er and Tm, prepared for use in an embodiment of the present invention;

3 is a schematic diagram showing an optical fiber amplifier according to an embodiment of the present invention;

4 is a view for explaining the basic principle of the energy transfer from the Er ion to the Tm ion.

The optical amplifier and the light source of the present invention for achieving the above technical problem are a single wavelength in an optical waveguide having a core in which two rare earth ions having different gain bands, ie, erbium (Er) ions and thulium (Tm) ions are added simultaneously. Or optical pumping is performed by the optical pumping source of two wavelengths.

Specifically, the optical amplifier of the present invention comprises: a glass optical waveguide having a core in which Er and Tm ions are jointly added; Optical pumping means optically connected to the optical waveguide to excite the ions; Means for inputting light to be amplified into the optical waveguide; And means for outputting light amplified from the optical waveguide.

Here, the glass optical waveguide may be selected as the glass optical fiber to configure an optical fiber amplifier. In this case, the optical pumping means may be connected to at least one of both ends of the optical fiber such that the optical pumping means excites only Er ions and transfers its energy to the Tm ions. Alternatively, the optical pumping means may be separately provided so that the optical pumping means excites the Er ions and the Tm ions, respectively, and may be connected to at least one of both ends of the optical fiber.

In the case of providing the optical pumping means as described above, the optical pumping means for exciting the Er ions emits pumped light of any wavelength selected from the wavelength group consisting of 800, 980, and 1480 nm, and excites the Tm ions. The optical pumping means for 780, it is preferable to emit the pumping light of any one wavelength selected from the wavelength range of 1000 ~ 1200nm.

On the other hand, it is preferable that the concentration of Er and Tm ions added to the core is 100 to 3000 ppm, and the rare earth element composed of ytterbium (Yb), holmium (Ho), praseodymium (Pr) and terbium (Tb) in the core. The ion of any one element selected from the group may be further added.

On the other hand, the light source of the present invention comprises: a glass optical waveguide having a core to which the Er ions and the Tm ions are jointly added; Optical pumping means optically connected to the optical waveguide to excite the ions; And means for outputting light from the optical waveguide. At this time, an ion of any one element selected from the group of rare earth elements composed of Yb, Ho, Pr, and Tb may be further added to the core. The optical waveguide may be selected as a glass optical fiber to configure an optical fiber light source.

In addition, the optical waveguide may be a part of the resonator to emit laser output light. In this case, the optical waveguide may be selected as a glass optical fiber to implement a fiber laser.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention.

1 is a schematic view showing an optical fiber structure used in an embodiment of the present invention. FIG. 1 illustrates a state in which Er ⁺³ and Tm ⁺³ are added to the entire optical fiber core 10, and this portion is a glass portion having a high refractive index, and the cladding 20 to which the ions are not added has a low refractive index glass. Part. In some cases, Er ^{+ 3} and Tm ^{+ 3} may be added to only part of the core. The concentrations of Er and Tm ions added to the core were 100-3000 ppm, the numerical aperture of the optical fiber was 0.1-0.3, the LP11 mode blocking wavelength was 700-1200 nm, and the outer diameter of the core was 2-10 μm. .

2 is a graph showing the spectrum of back amplified self-luminescence of a silicon oxide (SiO 2) glass optical fiber prepared for use in an embodiment of the present invention. All or part of the core of the optical fiber was manufactured by Chemical Vapor Deposition using P ₂ O ₅ , Al ₂ O ₃ , GeO ₂ , where Er ₂ O ₃ and Tm ₂ O ₃ simultaneously It was added by the general rare earth element addition method. All or part of the cladding was prepared by chemical vapor deposition using P ₂ O ₅ , F, B ₂ O ₃ . Referring to FIG. 2, it can be seen that when optically pumped with a 980 nm laser diode, the intrinsic spectra of Er ions are combined in the intrinsic spectra of Tm ions at around 1480 nm and 1600 nm in addition to those in the 1530-1560 nm band. Can be.

3 is a schematic diagram showing an optical fiber amplifier according to an embodiment of the present invention.

Referring to FIG. 3, the optical pumping means is coupled through a front WDM coupler 320 and a rear WDM coupler 322 positioned at both ends of a glass optical fiber 310 having a core in which Er and Tm ions are added. For light pumping, two first and second light pumps 330 and 332 are respectively provided for pumping Er ions and Tm ions in front and rear of the optical fiber 310. 340 and second WDM combiner 342, respectively. The first optical pump emits pumped light with a wavelength of 800, 980, or 1480 nm to excite Er ions, and the second optical pump emits pumped light having a wavelength within a wavelength range of 780 or 1000 to 1200 nm to emit Tm ions. Here it is.

Unexplained reference numerals 350 and 352 in the drawings are optical isolators for blocking backward reflected light.

The optical fiber amplifier configured as described above can realize optical wavelength band characteristics due to Er and Tm ions having gains in different wavelength bands.

Of course, an optical amplifier may be configured to employ an optical pump that pumps only Er ions at the time of optical pumping. In this case, only the Er ions are pumped without directly pumping the Tm ions, and the energy is transferred from the Er ions to the Tm ions. Use a mechanism to In this case, there is an advantage that the optical pump structure of the optical amplifier can be simplified.

As such, the basic principle of the mechanism of transferring energy from the Er ion to the Tm ion is shown in FIG. 4. The pumping wavelength of Er ions is 800, 980 or 1480 nm, and by the pump photons, the Er ions are non- _radiative transition to the upper laser level ⁴ I _13/2 in the excited state. At this level, gain transition is made around 1.5 µm with a radiation transition to ground state ⁴ I _15/2 . However, when there is a Tm ion around the Er ion, energy may be transferred from the upper laser level ⁴ I _13/2 of the Er ion to the upper laser level ³ H ₄ of the Tm ion. That is, by exciting the Er ions with a pump of 800, 980 or 1480 nm, a wideband amplifier can be realized by gaining a gain of 1.5 탆 band from Er ions and a gain of 1.6 to 2.0 탆 band from Tm ions. In addition, a method of independently pumping Er ions and Tm ions is also possible, that is, when pumping Er ions to one of 800, 980 or 1480 nm wavelength light while simultaneously pumping Tm ions to one of 780 nm and 1.1 μm, 1.5 μm and 1.6 to A gain of 2.0 mu m band can be realized.

According to the present invention, an optical amplifier and a light source having a broadband characteristic can be made while employing a relatively small number of optical elements, which is suitable for miniaturization of the device.

In addition, when the mechanism of transferring energy from the Er ion to the Tm ion can be used, the number of the optical pumping means can be reduced, and the device can be effectively operated with the light pumping of low intensity.

Claims (12)

A glass optical waveguide having a core to which Er ions and Tm ions are jointly added; Optical pumping means optically connected to the optical waveguide to excite the ions; Means for inputting light to be amplified into the optical waveguide; And means for outputting light amplified from the optical waveguide. The optical amplifier according to claim 1, wherein the glass optical waveguide is a glass optical fiber. The optical amplifier according to claim 2, wherein the optical pumping means is connected to at least one of both ends of the optical fiber to excite the Er ions. The optical amplifier according to claim 2, wherein the optical pumping means is provided separately to excite the Er ions and the Tm ions, respectively, and is connected to at least one of both ends of the optical fiber. 5. The optical pumping means according to claim 4, wherein the optical pumping means for exciting the Er ions emits pumping light of any wavelength selected from a wavelength group consisting of 800, 980, and 1480 nm, and the optical pumping means for exciting the Tm ions. Is 780, and the optical amplifier which emits pumped light of any wavelength selected from the wavelength range of 1000-1200 nm. The optical amplifier according to claim 1 or 2, wherein the concentration of the Er ions and the Tm ions is 100 to 3000 ppm. The optical amplifier according to claim 1 or 2, wherein ions of any one element selected from the group of rare earth elements composed of Yb, Ho, Pr, and Tb are further added to the core. A glass optical waveguide having a core to which Er ions and Tm ions are jointly added; Optical pumping means optically connected to the optical waveguide to excite the ions; And a means for outputting light from the optical waveguide. The light source according to claim 8, further comprising ions of any one element selected from the group of rare earth elements composed of Yb, Ho, Pr and Tb. The light source according to claim 8 or 9, wherein the optical waveguide is a glass optical fiber. The light source according to claim 8 or 9, wherein the optical waveguide corresponds to a part of the resonator to emit laser output light. The light source according to claim 11, wherein the optical waveguide is a glass optical fiber.