JP2002344045A - Ase light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ASE light source which has a simple structure and is capable of obtaining the light of desired spectrum. SOLUTION: This ASE light source functions as follows. ASE light, which is generated due to an exciting light from an excitation light source 2 in a first rare earth element-loaded optical fiber 8, impinges on a second rare earth element-loaded optical fiber 9, and the light of desired spectrum, is outputted from the optical fiber 9. The second rare earth element-loaded optical fiber 9 absorbs a part of the impinged ASE light, radiates light different in wavelength from the absorbed light, and for turning the transmitted light and turning the radiating light into light of desired spectrum, this ASE optical source is made simple in structure and is capable of outputting a light of high power.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ASE light source provided with light emitting means and light adjusting means using an optical waveguide doped with a rare earth element.

[0002]

2. Description of the Related Art Conventionally, an ASE (Amplified SP) utilizing spontaneous emission has been used as an incoherent broadband light source.
Ontaneous Emission) light sources are used. As the ASE light source, rare earth elements such as erbium (Er),
By inputting excitation light of a specific wavelength (for example, 1.48 μm band or 0.98 μm band) into an optical waveguide such as an optical fiber doped with praseodymium (Pr), neodymium (Nd) or the like, the rare earth element There is known a light source that excites light to output broadband, high-power light. FIG. 5A shows an example of the configuration of such a light source. Light emitted from the excitation light source 2 passes through the WDM coupler 3,
The light enters the rare-earth element-doped optical fiber 1 to generate spontaneous emission light. The spontaneous emission light travels in the opposite direction to the pump light, and is output from the output port 5 through the WDM coupler 3 and the optical isolator 4. Reference numeral 6 denotes a non-reflection terminal. Note that a part of the spontaneous emission light travels in the same direction as the excitation light, but is not reflected by the non-reflection end 6, so that this part of the spontaneous emission light is not output from the output port 5.

[0003] The ASE light source as described above is used for various measurements and characteristic evaluations using light. In such a case, light having a predetermined spectrum corresponding to each measurement and evaluation is obtained. Will be needed. Until now, only necessary light has been transmitted using a filter in order to obtain a predetermined spectrum. FIG. 5B shows an example of the configuration of an ASE light source provided with the optical filter 7. An optical filter 7 is provided between the optical isolator 4 and the output port 5 of the light source in FIG. As the optical filter 7, for example,
A dielectric multilayer interference filter, a Fabry-Perot interference filter, and the like are used.

[0004]

However, in order to obtain a predetermined spectrum, since the loss wavelength characteristics required for that purpose are complicated, the above-mentioned light source must use a combination of many filters. Was. Therefore, the apparatus is complicated and large, the manufacturing cost is increased, and the manufacturing time is long. In addition, the filters exhibit their functions by allowing only light of a specific wavelength to pass and not allowing the remaining light to pass, so that light passing through many filters has low power.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an ASE light source capable of obtaining light of a desired spectrum with a simple structure.

[0006]

In order to achieve the above object, a structure is provided in which spontaneous emission light radiated from a first rare earth element-doped optical waveguide is made incident on a second rare earth element-doped optical waveguide and then outputted. ASE light source.

More specifically, the invention according to claim 1 is an ASE light source provided with light emitting means and light adjusting means, wherein the light emitting means emits light from an excitation light source and light emitted from the excitation light source. A first optical waveguide doped with a rare-earth element that emits spontaneous emission light when excited by the excitation light. The light adjusting means outputs light of a predetermined spectrum. An ASE light source comprising a second optical waveguide doped with a rare earth element that absorbs a portion and emits light having a wavelength different from that of the absorbed light.

[0008] The amplified spontaneous emission light (hereinafter referred to as ASE light) incident on the light adjusting means from the light emitting means is partially absorbed by the second optical waveguide, and light having a wavelength different from the absorbed light is emitted. The emitted light is combined with the light transmitted without being absorbed, and becomes light of a predetermined spectrum. Therefore, light of a desired spectrum having a large power and a large power can be obtained with a simple structure. Here, the light having a predetermined spectrum is light having a desired spectrum in each application and purpose in which the ASE light source is used.

When the same rare earth element is added to the first optical waveguide and the second optical waveguide, the light absorption and emission characteristics are the same and the output at a specific wavelength can be increased. preferable. As long as light having a desired spectrum can be obtained, the rare earth elements added to the first optical waveguide and the second optical waveguide may be different. Further, a plurality of kinds of rare earth elements may be mixed and added. Further, a third and a plurality of optical waveguides in which a rare earth element is added to the light adjusting means may be provided.

Next, the invention according to a second aspect is an ASE light source provided with light emitting means and light adjusting means, wherein the light emitting means comprises an excitation light source and excitation light emitted from the excitation light source. And a first optical waveguide doped with erbium that emits spontaneous emission light having a spectrum having two peaks, large and small, which is excited by the light control means. An ASE light source comprising an erbium-doped second optical waveguide that absorbs light having a small peak wavelength out of spontaneous emission light and emits light having a wavelength different from the absorbed light.

With the above configuration, the erbium-doped first optical waveguide emits ASE light having a spectrum having a small peak near 1530 nm and a large peak near 1560 nm, and the second erbium-doped optical waveguide. Absorbs light near 1530 nm and emits light near 1560 nm.
Light having a predetermined spectrum having only one peak near 0 nm can be obtained.

The first optical waveguide emits light near 1530 nm because of the amplification effect over a wide band by the excitation light, and at the same time emits light near 1530 nm due to erbium. The spectrum of the ASE light has a small peak near 1530 nm.

Next, according to a third aspect of the present invention, in the first or second aspect, the concentration strip product, which is the product of the concentration of the rare earth element in the optical waveguide and the length of the optical waveguide, is equal to the first optical waveguide. An ASE light source characterized in that the second optical waveguide is smaller than the waveguide.

Since the concentration product is smaller in the second optical waveguide than in the first optical waveguide, the attenuation of the ASE light emitted from the first optical waveguide in the second optical waveguide is suppressed. be able to. Here, the optical waveguide length refers to the length of the light passage in the optical waveguide.

Next, the invention according to claim 4 relates to claims 1 to
3. The ASE light source according to any one of 3), wherein the first and second optical waveguides are optical fibers.

With the above configuration, the ASE light source can be constituted by an optical fiber, so that the ASE light source can be made small and at low cost.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an ASE according to an embodiment of the present invention.
It is a block diagram of a light source. The light emitting means of the present embodiment includes a first rare earth element-doped optical fiber 8, an excitation light source 2, and a WDM coupler 3 interposed between the two. In addition, the light adjusting means includes a second rare earth element-doped optical fiber 9.
It is. The second rare earth element-doped optical fiber 9 is a WDM
Placed behind coupler 3, then optical isolator 4,
An output port 5 is provided. These components are connected by a transmission optical fiber.

In the light emitting means, the excitation light emitted from the excitation light source 2 passes through the WDM coupler 3 and enters the first rare-earth element-doped optical fiber 8 to generate ASE light. Rare earth elements can be formed of Er, Pr, N according to a desired optical spectrum.
It can be appropriately selected from d and the like. As the excitation light source 2, for example, various semiconductor lasers can be used. Further, as the WDM coupler 3, for example, a dielectric multilayer type coupler, a melt drawing type coupler, or the like can be used. It is preferable to use a melt-stretching coupler because reflection does not occur inside the coupler. The ASE light generated in the first rare earth element-doped optical fiber 8 travels in the direction opposite to the direction of the pump light, and is output from the output port 5 through the WDM coupler 3 and the optical isolator 4. In addition, AS
A part of the E light travels in the same direction as the pump light, but is not reflected by the non-reflection terminal 6, so that a part of the ASE light is not output from the output port 5.

The second rare-earth element-doped optical fiber 9 as a light adjusting means absorbs a part of the ASE light emitted from the first rare-earth element-doped optical fiber 8 and has a wavelength different from that of the absorbed light. It emits light of a wavelength and transmits light other than absorbed light. In addition, when an optical filter such as a conventional dielectric multilayer film interference filter is used, internal reflection occurs, causing a problem in measurement applications and the like. However, in the configuration of the present embodiment, ASE light is emitted by excitation light. Member, WDM coupler 3,
It is preferable that the light adjusting means and the optical isolator 4 be optical fibers, since internal reflection does not occur. Note that, in order to reduce the attenuation of the ASE light emitted from the first rare-earth-doped optical fiber 8 in the second rare-earth-doped optical fiber 9, the ASE light is more second than the first rare-earth-doped optical fiber 8. The concentration-length product of the rare-earth element-doped optical fiber 9 is reduced.

In the present embodiment, the difference between the spectrum of the ASE light emitted from the first rare earth element-doped optical fiber 8 and the desired light spectrum is determined by the absorption and emission of the second rare earth element-doped optical fiber 9. To make the spectrum of the output light a desired light spectrum. At this time, the spectrum of the difference between the spectrum of the ASE light emitted from the first rare earth element-doped optical fiber 8 and the desired optical spectrum is generally a spectrum of a complicated shape, but the spectrum of the second rare earth is When the element-doped optical fiber 9 is used, a desired optical spectrum can be obtained by adjusting the type of the rare earth element and the length of the optical fiber.

This embodiment is one example, and the present invention is not limited to this embodiment. The rare earth element added to the second rare earth element-doped optical fiber 9 may be the same as or different from the rare earth element added to the first rare earth element-doped optical fiber 8. Further, a plurality of rare earth elements may be added. Further, one or more other rare earth element-doped optical fibers may be provided behind the first rare earth element-doped optical fiber 8. As for the configuration as the ASE light source, for example, the positions of the second rare earth element-doped optical fiber 9 and the optical isolator 4 may be interchanged,
The optical isolator 4 may not be used. Further, another component such as a branch coupler for ASE light monitoring may be incorporated.
The direction in which the excitation light is incident on the first rare earth element-doped optical fiber 8 may be opposite to the direction indicated by the arrow in FIG. 1, and bidirectional excitation may be performed. Further, an optical waveguide may be used instead of the optical fiber.

[0023]

EXAMPLE As an example, an ASE light source having the structure shown in FIG. 1 was manufactured. An Er-doped quartz fiber is used for the first rare earth element-doped optical fiber 8 and the second rare earth element-doped optical fiber 9, and the second rare earth element-doped optical fiber 9 is used.
Is about 1/3 that of the first rare earth element-doped optical fiber 8. As the pumping light source 2, an InGaAsP / InP quantum well laser which outputs 1.48 μm pumping light was used. As the WDM coupler 3, a melt-stretching coupler was used. As the optical isolator 4, a bulk type isolator was used.

The solid line 10 in FIG. 2 indicates the spectrum of the ASE light emitted from the first rare earth element-doped optical fiber 8. Numeral 11 indicated by a dotted line indicates a desired optical spectrum shape. The ASE light generated from the Er-doped quartz fiber has a small peak at 1533 nm and 1559 nm.
It has a large peak at nm. The desired optical spectrum 11 is obtained using the large peak at 1559 nm. The desired optical spectrum 11 is used for reflection distribution measurement, and is a Gaussian distribution spectrum in which the short wavelength side and the long wavelength side are symmetrical with respect to the peak wavelength.

A comparison between the ASE spectrum 10 and the desired spectrum 11 shown in FIG.
Not only has an extra small peak at 1533 nm, but the shape of the large peak at 1559 nm is
The short-wavelength side has a shape that is flared and swelled as compared with the long-wavelength side with respect to nm. Such ASE light,
When the light passes through the second rare-earth element-doped optical fiber 9 and is output from the output port 5, the spectrum becomes 21 shown in FIG. The vertical axis in FIG. 3 is normalized by the intensity peak value. In addition, 22 is a spectrum of a Gaussian distribution shape.
The output light spectrum 21 of the present ASE light source has substantially the same shape and symmetry on the short wavelength side and the long wavelength side with respect to the peak wavelength, and has a substantially Gaussian distribution shape.

The second rare earth element-doped optical fiber 9
While absorbing light around 533 nm,
As a result of emitting light of a longer wavelength side, the output light spectrum 21 of the present ASE light source has a substantially Gaussian distribution shape. Here, comparing the ASE light spectrum 10 with the output light spectrum 21 of the present ASE light source (FIG. 4), the peak height of the output light spectrum 21 of the present ASE light source is smaller than that of the ASE light. However, the peak wavelength has shifted to the longer wavelength side of 1562 nm, and the power on the longer wavelength side has increased. Note that the characteristic required as the output light is that the peak wavelength may slightly shift because the spectrum has a Gaussian distribution shape. Further, the position of the peak wavelength can be adjusted by the lengths of the first and second rare earth element-doped optical fibers 8 and 9.

[0027]

The present invention is embodied in the form described above, and has the following effects.

Since the ASE light emitted from the first optical waveguide to which the rare earth element is added is made incident on the second optical waveguide to which the rare earth element is added, the spectrum of the output light is adjusted. An ASE light source that outputs output light with a large power can be used. Since the structure of the ASE light source is simple, manufacturing costs can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an ASE light source of the present invention.

FIG. 2 is a diagram showing a spectrum of ASE light emitted from light emitting means.

FIG. 3 is a diagram illustrating a spectrum of output light from an ASE light source according to an example.

FIG. 4 is a comparison diagram of spectra of ASE light and output light from the light emitting unit of the example.

FIG. 5A is a configuration diagram of a conventional ASE light source including only a light emission unit, and FIG. 5B is a configuration diagram of a conventional ASE light source including a light emission unit and an optical filter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Rare-earth element addition optical fiber 2 Excitation light source 3 WDM coupler 4 Optical isolator 5 Output port 6 Non-reflection termination 7 Optical filter 8 First rare-earth element addition optical fiber 9 Second rare-earth element addition optical fiber 10 First rare-earth element addition ASE light spectrum emitted from optical fiber 11 Desired light spectrum 21 Output light spectrum 22 Gaussian distribution shape spectrum

Continued on the front page (72) Inventor Masatoshi Tabira 4-3 Ikejiri, Itami-shi, Hyogo Mitsubishi Cable Industry Co., Ltd. Itami Works (72) Inventor Yasuhide Sudo 4-3 Ikejiri, Itami-shi, Hyogo Mitsubishi Cable Industries Itami F term in the factory (reference) 5F072 AB07 AB08 AB09 AK06 FF09 HH05 KK30 PP07 RR01 YY11

Claims (4)

[Claims] 1. An AS having a light emitting means and a light adjusting means.
An E light source, wherein the light emitting means includes an excitation light source, and a first optical waveguide doped with a rare earth element that emits spontaneous emission light when excited by the excitation light emitted from the excitation light source; The light adjusting means absorbs a part of the incident spontaneous emission light to output light of a predetermined spectrum, and a second optical waveguide doped with a rare earth element which emits light having a wavelength different from the absorbed light. An ASE light source, comprising: 2. An AS having a light emitting means and a light adjusting means.
An E light source, wherein the light emitting means is a first light source, comprising: an excitation light source; and an erbium that emits spontaneous emission light having a spectrum having two peaks, large and small, excited by the excitation light emitted from the excitation light source. An optical waveguide, wherein the light adjusting means absorbs light having a small peak wavelength among the incident spontaneous emission light and outputs light having a wavelength different from the absorbed light in order to output light having a predetermined spectrum. An ASE light source comprising a second optical waveguide doped with erbium for emission. 3. The second optical waveguide according to claim 1, wherein a concentration strip product, which is a product of a concentration of the rare earth element in the optical waveguide and a length of the optical waveguide, is larger than that of the first optical waveguide. An ASE light source characterized by having a smaller size. 4. The ASE light source according to claim 1, wherein the first and second optical waveguides are optical fibers.