JP4970664B2 - ASE light source - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ASE light source including a light emitting means and a light adjusting means using a rare earth element-doped optical waveguide.
[0002]
[Prior art]
Conventionally, as an incoherent broadband light source, an ASE (Amplified Spontaneous Emission) light source using spontaneous emission has been used. As an ASE light source, an optical waveguide such as an optical fiber to which a rare earth element such as erbium (Er), praseodymium (Pr), or neodymium (Nd) is added has a specific wavelength (for example, 1.48 μm band or 0.98 μm). A light source that excites the rare earth element by inputting the excitation light in the band and outputs high power light in a wide band is known. 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 and 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 excitation 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-reflective terminal. A part of the spontaneous emission light also travels in the same direction as the excitation light, but is not reflected by the non-reflective terminal 6, and therefore 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 required. . In order to obtain a predetermined spectrum, until now, only necessary light has been transmitted using a filter. FIG. 5B shows an example of the configuration of the 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. For example, a dielectric multilayer interference filter or a Fabry-Perot interference filter is used as the optical filter 7.
[0004]
[Problems to be solved by the invention]
However, in order to obtain a predetermined spectrum, the loss wavelength characteristic necessary for that purpose is complicated, so that the above-mentioned light source has to be used in combination with many filters. Therefore, the apparatus is complicated and large, the manufacturing cost is high, and the manufacturing time is long. Further, since the filter performs its function by allowing only light of a specific wavelength to pass and not allowing the remaining light to pass, the power of light that has passed through many filters is reduced.
[0005]
The present invention has been made in view of such circumstances, and an object thereof is to provide an ASE light source capable of obtaining light of a desired spectrum with a simple structure.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, an ASE light source configured to output spontaneous emission light emitted from the first rare earth element-doped optical waveguide after being incident on the second rare earth element doped optical waveguide is used.
[0007]
Specifically, the invention according to claim 1 is an ASE light source including a light emitting means and a light adjusting means,
The light emitting means comprises an excitation light source and a first optical waveguide added with a rare earth element that is excited by excitation light emitted from the excitation light source and emits spontaneous emission light,
The light adjusting means absorbs a part of the incident spontaneous emission light to output light of a predetermined spectrum, and adds a rare earth element that emits light having a wavelength different from the absorbed light. An ASE light source is characterized by comprising a waveguide.
[0008]
A part of the amplified spontaneous emission light (hereinafter referred to as ASE light) incident on the light adjusting means from the light emitting means is absorbed by the second optical waveguide, and light having a wavelength different from the absorbed light is emitted. Since it is synthesized with light that has been transmitted without being absorbed, it becomes light of a predetermined spectrum, so that light of a desired spectrum with high power can be obtained with a simple structure. Here, the light having a predetermined spectrum is light having a desired spectrum in each application / purpose in which the ASE light source is used.
[0009]
It is preferable that the rare earth elements added to the first optical waveguide and the second optical waveguide are the same because the light absorption and emission characteristics are the same and the output of a specific wavelength can be increased. The rare earth elements added to the first optical waveguide and the second optical waveguide may be different as long as light having a desired spectrum can be obtained. A plurality of types of rare earth elements may be mixed and added. Furthermore, a third and more optical waveguides in which rare earth elements are added to the light adjusting means may be provided.
[0010]
Next, the invention according to claim 2 is an ASE light source comprising a light emitting means and a light adjusting means,
The light emitting means comprises an excitation light source and a first optical waveguide added with erbium that is excited by the excitation light emitted from the excitation light source and emits spontaneous emission light having a spectrum having two large and small peaks,
In order to output light of a predetermined spectrum, the light adjusting means absorbs light having a small peak wavelength in the incident spontaneous emission light and adds erbium that emits light having a wavelength different from the absorbed light. An ASE light source comprising the second optical waveguide.
[0011]
In the above configuration, the first optical waveguide doped with erbium emits ASE light having a small peak near 1530 nm and a large peak near 1560 nm, and the second optical waveguide doped with erbium has a wavelength of 1530 nm. Since light in the vicinity is absorbed and light in the vicinity of 1560 nm is emitted, the output ASE light can be light having a predetermined spectrum having only one peak in the vicinity of 1560 nm.
[0012]
Since the first optical waveguide has an amplifying effect in a broad band by the excitation light, it emits light in the vicinity of 1530 nm and at the same time has an absorption action in the vicinity of 1530 nm by erbium, so that the ASE light emitted as a result of the subtraction of both is emitted. The spectrum has a small peak near 1530 nm.
[0013]
Next, the invention according to claim 3 is the invention according to claim 1 or 2,
An ASE light source characterized in that the second optical waveguide has a smaller concentration length product, which is the product of the concentration of the rare earth element in the optical waveguide and the optical waveguide length, than the first optical waveguide. is there.
[0014]
Since the concentration product is smaller in the second optical waveguide than in the first optical waveguide, attenuation of the ASE light emitted from the first optical waveguide in the second optical waveguide can be suppressed. . The optical waveguide length referred to here is the length of the light path in the optical waveguide.
[0015]
Next, the invention according to claim 4 is any one of claims 1 to 3,
An ASE light source characterized in that the first and second optical waveguides are optical fibers.
[0016]
If it is said structure, since an ASE light source can be comprised with an optical fiber, an ASE light source can be produced small and low cost.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
FIG. 1 is a configuration diagram of an ASE light source according to an embodiment of the present invention. The light emitting means of this embodiment includes a first rare earth element-doped optical fiber 8, a pumping light source 2, and a WDM coupler 3 placed between the two. The light adjusting means is the second rare earth element-doped optical fiber 9. The second rare earth element-doped optical fiber 9 is placed behind the WDM coupler 3, followed by the optical isolator 4 and the output port 5. These components are connected by an optical fiber for transmission.
[0019]
In the light emitting means, the pumping light emitted from the pumping light source 2 passes through the WDM coupler 3 and enters the first rare earth element-doped optical fiber 8 to generate ASE light. The rare earth element can be appropriately selected from Er, Pr, Nd and the like according to a desired optical spectrum. As the excitation light source 2, for example, various semiconductor lasers can be used. Moreover, as the WDM coupler 3, for example, a dielectric multilayer film type coupler, a melt stretch type coupler, or the like can be used. The melt-stretched coupler is preferably used because no internal reflection occurs. The ASE light generated in the first rare earth element-doped optical fiber 8 travels in the opposite direction to the excitation light, and is output from the output port 5 through the WDM coupler 3 and the optical isolator 4. A part of the ASE light also travels in the same direction as the excitation light, but is not reflected by the non-reflective terminal 6, and therefore a part of the ASE light is not output from the output port 5.
[0020]
The second rare earth element-doped optical fiber 9 as the 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 the wavelength of the absorbed light. To transmit light other than absorbed light. In addition, when a conventional optical filter such as a dielectric multilayer interference filter is used, internal reflection occurs, which causes inconvenience in measurement applications and the like. In the configuration of this embodiment, ASE light is emitted by excitation light. If the member, the WDM coupler 3, the light adjusting means, and the optical isolator 4 are optical fibers, it is preferable because internal reflection does not occur. In order to reduce the attenuation of the ASE light emitted from the first rare-earth element-doped optical fiber 8 in the second rare-earth element-doped optical fiber 9, the second rare-earth element-doped optical fiber 8 is less than the second rare-earth element-doped optical fiber 8. The concentration length product of the rare earth element-doped optical fiber 9 is reduced.
[0021]
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 optical spectrum is adjusted by absorption and emission by the second rare earth element-doped optical fiber 9. Thus, the spectrum of the output light is set as 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 having a complicated shape. When the element-doped optical fiber 9 is used, a desired optical spectrum can be obtained by adjusting the kind of rare earth element and the length of the optical fiber.
[0022]
This embodiment is an example, and the present invention is not limited to this example. 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. A plurality of rare earth elements may be added. Further, one or a plurality of other rare earth element-doped optical fibers may be installed behind the first rare earth element-doped optical fiber 8. In 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, or the optical isolator 4 may not be used. Another component such as an ASE optical monitoring branch coupler 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, or bidirectional excitation may be performed. An optical waveguide may be used instead of the optical fiber.
[0023]
【Example】
As an example, an ASE light source having the configuration shown in FIG. 1 was produced. An Er-doped silica 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 approximately the same as the first rare earth element doped optical fiber 8. The concentration length product was 1/3. As the excitation light source 2, an InGaAsP / InP quantum well laser that outputs 1.48 μm excitation light was used. As the WDM coupler 3, a melt-stretching coupler was used. A bulk isolator was used as the optical isolator 4.
[0024]
2 is a spectrum of the ASE light emitted from the first rare earth element-doped optical fiber 8. Reference numeral 11 indicated by a dotted line is a desired optical spectrum shape. The ASE light generated from the Er-doped silica fiber has a small peak at 1533 nm and a large peak at 1559 nm. The desired optical spectrum 11 is obtained using a large peak at 1559 nm. The desired optical spectrum 11 is used for reflection distribution measurement, and is a spectrum having a Gaussian distribution in which the short wavelength side and the long wavelength side are symmetrical with respect to the peak wavelength.
[0025]
When comparing the ASE light spectrum 10 of FIG. 2 with the desired spectrum 11, the ASE light spectrum 10 not only has an extra small peak at 1533 nm, but also has a large peak shape at 1559 nm with a short wavelength at the 1559 nm boundary. Compared to the long wavelength side, the side has a swelled shape. When such ASE light passes through the second rare earth element-doped optical fiber 9 and is output from the output port 5, the spectrum of 21 shown in FIG. 3 is obtained. The vertical axis in FIG. 3 is normalized by the intensity peak value. Reference numeral 22 denotes a spectrum having a Gaussian distribution shape. In the output light spectrum 21 of the present ASE light source, the short wavelength side and the long wavelength side are substantially the same and symmetric with respect to the peak wavelength, and have a substantially Gaussian distribution shape.
[0026]
The second rare earth element-doped optical fiber 9 absorbs light in the vicinity of 1533 nm and radiates light having a wavelength longer than 1559 nm. As a result, the output light spectrum 21 of the present ASE light source has a nearly Gaussian distribution shape. It is. Here, when 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 is shifted to the long wavelength side of 1562 nm, and the power on the long wavelength side is increased. In addition, as a characteristic calculated | required as output light, a peak wavelength may shift a little because a spectrum is a Gaussian distribution shape. 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]
【Effect of the invention】
The present invention is implemented in the form as described above, and has the following effects.
[0028]
Since the ASE light emitted from the first optical waveguide to which the rare earth element is added is incident on the second optical waveguide to which the rare earth element is added and the spectrum of the output light is adjusted, the output light of the predetermined spectrum is It can be set as the ASE light source which outputs with big power. Since the structure of the ASE light source is simple, the manufacturing cost 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 a light emitting unit.
FIG. 3 is a diagram illustrating a spectrum of output light from an ASE light source according to an embodiment.
FIG. 4 is a comparison diagram of spectra of ASE light and output light from the light emitting means of the example.
5A is a configuration diagram of a conventional ASE light source including only light emission means, and FIG. 5B is a configuration diagram of a conventional ASE light source including light emission means 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 Antireflection 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

Claims (4)

An ASE light source comprising light emitting means and light adjusting means for outputting light of a spectrum having a substantially Gaussian distribution shape in which the short wavelength side and the long wavelength side are substantially the same and symmetrical with respect to the peak wavelength ,
The light emitting means comprises an excitation light source and a first optical waveguide added with a rare earth element that is excited by excitation light emitted from the excitation light source and emits spontaneous emission light,
The light adjusting means adds a rare earth element that absorbs a part of the incident spontaneous emission light and emits light having a wavelength different from that of the absorbed light in order to output light having a spectrum of the approximately Gaussian distribution shape . An ASE light source comprising the second optical waveguide. An ASE light source comprising light emitting means and light adjusting means for outputting light of a spectrum having a substantially Gaussian distribution shape in which the short wavelength side and the long wavelength side are substantially the same and symmetrical with respect to the peak wavelength ,
The light emitting means comprises an excitation light source and a first optical waveguide added with erbium that is excited by the excitation light emitted from the excitation light source and emits spontaneous emission light having a spectrum having two large and small peaks,
The light adjusting means outputs light having a spectrum having a substantially Gaussian distribution shape , and therefore absorbs light having a small peak wavelength in the incident spontaneous emission light and emits light having a wavelength different from the absorbed light. An ASE light source comprising a second optical waveguide to which erbium is added. In claim 1 or 2,
An ASE light source characterized in that the second optical waveguide has a smaller concentration length product, which is the product of the concentration of rare earth elements in the optical waveguide and the optical waveguide length, than the first optical waveguide. In any one of Claims 1-3,
An ASE light source, wherein the first and second optical waveguides are optical fibers.

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