JPH08148744A - Light source - Google Patents

Abstract

PURPOSE: To provide a power source capable of supplying nonpolarized light stably. CONSTITUTION: Spontaneously emitted light is generated inside a rare-earth added optical fiber 111 , by supplying light from an exciting LD 131 to the rare- earth added optical fiber 111 . Only light having a specific wavelength is extracted from the spontaneously emitted light by the optical filter 15, and the light extracted from the spontaneously emitted light is amplified to an appropriate level by the use of an AES amplifying section 22 (a rare-earth added optical fiber amplifier). The amplified light passes the optical filter 15, and is outputted as output light 25 after that. Since the spontaneously emitted light is nonpolarized, this constitution makes it possible to obtain nonpolarized, appropriate-level output light of a specific wavelength stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source and, more particularly, to a light source used for evaluating transmission characteristics such as light loss and polarization dependence of optical components and the like.

[0002]

2. Description of the Related Art When evaluating the transmission characteristics of optical components,
Light from a light source is made incident on an optical component to be evaluated, and the level of light emitted from the optical component to be evaluated is measured. As such a light source for evaluating transmission characteristics, conventionally, a light emitting diode (LED) or a Fabry-Perot semiconductor laser (FP-L) having both ends of a crystal as resonators has been used.
D), a distributed reflection type DBR (Distributed Bragg Reflector) in which a wavy diffraction grating is provided near an active layer which is an optical amplification unit.
or) a semiconductor laser (LD) represented by an LD, a distributed feedback type DFB (Distributed Feed Back) -LD using a Bragg waveguide as a resonance path, or the like.

[0003]

All of the above-mentioned conventional light sources output light having a polarization plane and a low side mode suppression ratio due to the principle of light emission. In the evaluation of the transmission characteristics used, it was necessary to consider that the light from the light source had a plane of polarization, and the procedure for evaluating the transmission characteristics was complicated.

Accordingly, an object of the present invention is to provide a light source capable of stably supplying non-polarized light.

[0005]

According to the first aspect of the present invention,
(A) a first rare-earth-doped optical fiber, (b) light output means for outputting light of a predetermined level, (c) a first port to which light output by the light output means is input, and a first port A second port for supplying the input light to the first rare-earth-doped optical fiber, and a spontaneous emission generated in the first rare-earth-doped optical fiber by the light from the second port, which is emitted to the second port side. An optical coupler having a third port for emitting spontaneous emission light, and (d) a rare earth-doped optical fiber amplifier using a second rare earth-doped optical fiber for amplifying and outputting the spontaneous emission light emitted from the optical coupler. And

That is, in the first aspect of the present invention, the first
By introducing a predetermined level of light into the rare-earth-doped optical fiber, spontaneous emission light, which is unpolarized light, is generated in the first rare-earth-doped optical fiber. Then, by amplifying the spontaneous emission light, which is also low-level light, using a rare-earth-doped optical fiber amplifier, an appropriate level of non-polarized output light is obtained.

The invention according to claim 2 is characterized in that (a) a first rare earth-doped optical fiber, (b) light output means for outputting light of a predetermined level, and (c) light output from the light output means. A second port for supplying light input from the first port to the first rare-earth-doped optical fiber;
An optical coupler having a third port for emitting the spontaneous emission light emitted to the second port side out of the spontaneous emission light generated in the first rare earth-doped optical fiber by the light from the port; A first optical filter connected to the third port of the coupler and transmitting only light of a specific wavelength; and (e) a second rare earth-doped optical fiber for amplifying and outputting light from the first optical filter. (F) a second optical filter connected to the output end of the rare earth-doped optical fiber amplifier and transmitting only light of a specific wavelength.

That is, in the invention according to claim 2, the first
By introducing a predetermined level of light into the rare-earth-doped optical fiber, spontaneous emission light, which is unpolarized light, is generated in the first rare-earth-doped optical fiber. Then, only light of a specific wavelength is extracted from the spontaneous emission light by the first optical filter, and the extracted spontaneous emission light is amplified to an appropriate level using a rare earth-doped optical fiber amplifier. Then, by extracting only light of a specific wavelength from the amplified light by the second optical filter, non-polarized output light of an appropriate level is obtained.

According to a third aspect of the present invention, there are provided (a) a first rare earth-doped optical fiber, (b) first light output means for outputting light of a first predetermined level, and (c) the first light output means. A first port to which the light output from the first port is input, a second port to supply the light input from the first port to the first rare earth-doped optical fiber, and a spontaneous emission light generated in the first rare earth-doped optical fiber. An optical coupler having a third port for emitting spontaneously emitted light emitted to the second port side; (d) second light output means for outputting light of a second predetermined level; A supply means for supplying the light output from the two-light output means to the first rare-earth-doped optical fiber from the other end to which the optical fiber is not connected; and (f) a light source connected to the third port of the optical coupler. An optical filter that transmits only light of a specific wavelength;
(G) a rare earth-doped optical fiber amplifier using a second rare earth-doped optical fiber for amplifying and outputting light from the optical filter;

That is, according to the third aspect of the present invention, the first
By introducing a predetermined level of light into the rare-earth-doped optical fiber from both directions, non-polarized light, which is a relatively high level of spontaneous emission, is generated in the first rare-earth-doped optical fiber. Then, by the optical filter, light other than the spontaneous emission light (light output by the second output means),
By cutting light other than light of a specific wavelength from the spontaneous emission light and amplifying the light from the optical filter to an appropriate level using a rare-earth-doped optical fiber amplifier, an appropriate level of non-polarized output light is obtained. .

According to a fourth aspect of the present invention, there are provided (a) a first rare earth-doped optical fiber, (b) first light output means for outputting light of a first predetermined level, and (c) the first light output means. A first port to which the light output from the first port is input, a second port to supply the light input from the first port to the first rare earth-doped optical fiber, and a spontaneous emission light generated in the first rare earth-doped optical fiber. An optical coupler having a third port for emitting spontaneously emitted light emitted to the second port side; (d) second light output means for outputting light of a second predetermined level; A supply means for supplying the light output from the two-light output means to the first rare-earth-doped optical fiber from the end to which the optical fiber is not connected, and (f) a light source connected to the third port of the optical coupler. A first optical filter that transmits only light of a specific wavelength; A rare-earth-doped optical fiber amplifier using a second rare-earth-doped optical fiber that amplifies and outputs the light from the optical filter, and (h) Only light of a specific wavelength connected to the output end of this rare-earth-doped optical fiber amplifier. And a second optical filter that transmits light.

That is, according to the fourth aspect of the present invention, the first
By introducing a predetermined level of light into the rare-earth-doped optical fiber from both directions, non-polarized light, which is a relatively high level of spontaneous emission, is generated in the first rare-earth-doped optical fiber. Then, the light other than the spontaneous emission light by the first optical filter (light output by the second output means)
For example, light other than light of a specific wavelength is cut from the spontaneous emission light, and light from the first optical filter is amplified to an appropriate level using a rare-earth-doped optical fiber amplifier. Then, by extracting only light of a specific wavelength from the amplified light by the second optical filter, non-polarized output light of an appropriate level is obtained.

In the invention of claim 2 or 4, the first optical filter and the second optical filter may be the same optical filter. Without considering the difference in the characteristics of
The light source can be configured at low cost.

[0014]

EXAMPLES The present invention will be described in detail below with reference to examples.

FIG. 1 shows a schematic structure of a light source according to an embodiment of the present invention. The light source of the embodiment is, as shown, A
Optical circuit for connecting the respective units and ES generating unit 21 and the AES amplifying section 22 (an optical isolator 14 _3, an optical filter 15, an optical coupler 16 ₁ and 16 ₂₎ is constituted by,
An optical output 25 is obtained from the optical coupler 16 ₁ .

[0016] AES generator 21, a rare-earth doped optical fiber 11 ₁ and the wavelength division multiplexing coupler 12 ₁ (hereinafter, WD
Notated as M coupler. ) And the excitation LD (which is constituted by a laser diode) 13 ₁ and the optical isolator 14 _1. As is clear from the figure, the rare earth-doped optical fiber 1
One end of 1 ₁ is non-reflectively terminated, and the other end thereof is connected to the WDM coupler 12 ₁ to which the pump LD 13 ₁ is connected.

The WDM coupler 12 ₁ is an optical circuit for introducing a certain level of pumping light output from the pumping LD 13 ₁ into the rare earth-doped optical fiber 11 _1. AES will occur within ₁ . Then, AES generated in the rare earth-doped optical fiber 11 _1, passes through the WDM coupler 12 ₁ and the optical isolator 14 _1, so that the output from the AES generating unit 21.

AES output from the AES generator 21
Is introduced into the optical filter 15 via the optical coupler 16 ₁ . The optical filter 15 is an optical circuit that extracts only light of a specific wavelength (range) within a wavelength range that can be amplified in an AES amplifying unit 22, which will be described in detail later. part 21 is output from the AES over a wide wavelength range, only AES having a specific wavelength is extracted, AES of the specific wavelength via the optical coupler 16 _2, it has been introduced into the AES amplifying unit 22.

[0019] AES amplifying unit 22 is an optical direct amplifier using a rare earth doped optical fiber is constituted by a rare earth-doped optical fiber 11 ₂ and the WDM coupler 12 ₂ and the excitation LD 13 ₂ and the optical isolator 14 _2. As is illustrated, AES from the optical filter 15, through the optical isolator 14 ₂ are introduced into the rare earth doped optical fiber 11 _2, AES is a rare earth-doped optical fiber 11 within _2, the excitation LD 13 ₂ Amplification is performed according to the level of the excitation light.

At this time, in the rare earth-doped optical fiber 11 ₂ , the wavelength range in which a high gain can be obtained is determined according to the type of the rare earth-doped optical fiber to be used. So that the optical filter 1
5, the light input to the rare earth-doped optical fiber 11 ₂ is filtered. Incidentally, the excitation light level to be outputted to the excitation LD 13 _2, depending on the level of the output light required, would be set.

The AES amplified in the rare earth-doped optical fiber 11 ₂ is input to the optical filter 15 through the optical isolator 14 ₃ and the optical coupler 16 ₂ and is again subjected to the filtering by the optical filter 15 and then the optical coupler 16 2. ₁
Is output as output light 25 through

In the above description, each optical isolator 1
Omitting 4 installation reasons described, the optical isolator 14 ₁ in the AES generator 21, primarily, is provided in order not to introduce the rare earth-doped optical fiber 11 ₁ light from AES amplifying unit 22. The optical isolator 14 ₂ in the AES amplifying unit 22 is provided mainly to prevent the pumping light from the pumping LD 13 ₂ from being output to the optical filter 15 side.
The optical isolator 14 ₃ mainly, the light from the AES generating unit 21 side is provided in order not to introduce the rare earth-doped optical fiber 11 _2. Note that each optical isolator 14 also has a function of preventing the influence of reflected light generated at the connection part.

As described above, in the light source of the embodiment, the excitation light is introduced into the rare earth-doped optical fiber to generate AES which is unpolarized light in the rare earth-doped optical fiber, and the light is amplified and then output. Therefore, the output light of the light source of the embodiment is an unpolarized light at an appropriate level.

In the light source of the embodiment, one optical filter is used for filtering the input light to the AES amplifying section and AE.
Although used for filtering the output light from the S amplifying unit, it is obvious that another optical filter may be provided at the output end of the AES amplifying unit 22 and the light from the optical filter may be used as the output light. If the output light is only required to be unpolarized light, no optical filter is provided, or only one of the input light to the AES amplifier or the output light from the AES amplifier is used. It is also possible to configure the light source to filter.

Modification

FIG. 2 shows a schematic configuration of a light source according to a modification of the present invention. As is apparent from the figure, the AES generation unit 21 provided in the light source of the modified example is the same as the AES generation unit of the light source of the embodiment except that the WDM coupler 12 ₄ and the pump LD 13 _{4 are provided.}
Is obtained by adding the door, the AES generator 21 of the modification, the light incident from the bidirectional, AES occurs in the rare earth-doped optical fiber 11 within _1.

For this reason, in the light source of the modified example, the level of the light (AES) output from the AES generating section 21 is high. As a result, even if the amplification factor in the AES amplifying section 22 is not excessively increased, An appropriate level of output light 25 is obtained.

The light source of this modification also has an AE
Another optical filter is provided at the output end of the S amplification section 22,
The light from the optical filter can be used as output light,
In this configuration, the optical filter 15, since the functions to cut the excitation light from the excitation LD 13 ₄ in the AES generating unit 21, even if only it is non-polarized light is required in the output light, light The light source cannot be configured so as not to provide any filter, and either one of the input light to the AES amplifier or the output light from the AES amplifier (preferably the input light) is filtered. The device needs to be configured.

[0029]

As described in detail above, claim 1 is as follows.
If the light source is configured to directly amplify the spontaneous emission light generated in the rare-earth-doped optical fiber to obtain the output light as in the invention according to claim 5, the light source is unpolarized and has an appropriate level. Output light can be stably obtained.

When the light source is constructed so as to extract a specific wavelength before and after amplifying the spontaneous emission light as in the invention according to claim 2 or claim 4 or claim 5, Also, it is possible to obtain light with a narrow wavelength range.

In the case where the light source is configured to introduce light into the rare-earth-doped optical fiber from both directions to generate spontaneous emission light, as in the invention according to claim 3 or 4, the rare-earth Since the level of spontaneous emission light output from the doped optical fiber is increased, an output light of an appropriate level can be obtained without performing amplification with a remarkably high gain.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of a light source according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a light source according to a modified example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Rare-earth-doped optical fiber 12 Wavelength division multiplexing coupler 13 Pumping LD 14 Optical isolator 15 Optical filter 16 Optical coupler 21 AES generator 22 AES amplifier 25 Output light

Claims (5)

[Claims] 1. A first rare earth-doped optical fiber, light output means for outputting light of a predetermined level, a first port to which light output from the light output means is input, and light to be input from the first port A second port for supplying the first rare earth-doped optical fiber to the first rare earth-doped optical fiber, and a spontaneous emission light emitted to the second port side among the spontaneous emission light generated in the first rare earth-doped optical fiber by the light from the second port And a rare-earth-doped optical fiber amplifier using a second rare-earth-doped optical fiber that amplifies and outputs spontaneous emission light emitted from the optical coupler. Characteristic light source. 2. A first rare earth-doped optical fiber, light output means for outputting light of a predetermined level, a first port to which light output from the light output means is input, and light to be input from the first port A second port for supplying the first rare earth-doped optical fiber to the first rare earth-doped optical fiber, and a spontaneous emission light emitted to the second port side among the spontaneous emission light generated in the first rare earth-doped optical fiber by the light from the second port An optical coupler having a third port that emits light, a first optical filter connected to the third port of the optical coupler that transmits only light of a specific wavelength, and amplifies light from the first optical filter. Output the second
A light source comprising: a rare-earth-doped optical fiber amplifier using a rare-earth-doped optical fiber; and a second optical filter connected to an output end of the rare-earth-doped optical fiber amplifier and transmitting only light of a specific wavelength. . 3. A first rare earth-doped optical fiber, first light output means for outputting a first predetermined level of light, a first port to which the light output by the first light output means is input, A second port for supplying light input from a port to the first rare earth-doped optical fiber; and a spontaneous emission light emitted to the second port side among spontaneous emission light generated in the first rare earth-doped optical fiber. An optical coupler having a third port that emits light; a second optical output unit that outputs a second predetermined level of light; and a light output by the second optical output unit to the first rare earth-doped optical fiber. Supply means for supplying from the end to which the optical fiber is not connected, an optical filter connected to the third port of the optical coupler, which transmits only light of a specific wavelength, and amplifies light from the optical filter The second rare earth addition A light source, comprising: a rare earth-doped optical fiber amplifier using an additive fiber. 4. A first rare earth-doped optical fiber, first light output means for outputting a first predetermined level of light, a first port to which light output by the first light output means is input, A second port for supplying light input from a port to the first rare earth-doped optical fiber; and a spontaneous emission light emitted to the second port side among spontaneous emission light generated in the first rare earth-doped optical fiber. An optical coupler having a third port that emits light; a second optical output unit that outputs a second predetermined level of light; and a light output by the second optical output unit to the first rare earth-doped optical fiber. Supply means for supplying from the end to which the optical fiber is not connected; a first optical filter connected to a third port of the optical coupler, which transmits only light of a specific wavelength; and a first optical filter. Amplify and output the light of the second
A light source comprising: a rare-earth-doped optical fiber amplifier using a rare-earth-doped optical fiber; and a second optical filter connected to an output end of the rare-earth-doped optical fiber amplifier and transmitting only light of a specific wavelength. . 5. The light source according to claim 2, wherein the first optical filter and the second optical filter are the same optical filter.