JP3042439B2 - Optical fiber amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber amplifier for directly amplifying an optical signal, and more particularly to an optical fiber amplifier having a structure suitable for miniaturization.

[0002]

2. Description of the Related Art In recent years, rare earth elements,
In particular, an optical fiber amplifier which is doped with Er (erbium) ions and directly amplifies an optical signal using stimulated emission.
Applications to 55 μm band optical communication systems are being promoted. Since this optical fiber amplifier has characteristics such as high gain, wide band, high saturation output, and low noise, it is very attractive in an optical communication system.

A conventional optical fiber amplifier for directly amplifying an optical signal includes, for example, an excitation laser module 9, an optical multiplexer 10, a transmission optical fiber 6, and an amplification optical fiber 7, as shown in FIG. Is done.

The pump laser module 9 includes:
A semiconductor laser having an oscillation wavelength in the 48 μm, 0.98 μm or 0.8 μm band is used, and an excitation LD (laser diode) element substrate 1 for emitting excitation light in the above-mentioned wavelength band is provided on the electronic cooling element 5. It is installed.

In order to guide the excitation light to the optical fiber 8 for the excitation laser module, the condensing lens 4 is
It is arranged between the D element substrate 1 and the optical fiber 8 for the excitation laser module. The electronic cooling element 5 of the excitation laser module 9 is for preventing a decrease in optical output due to heat generation of the excitation LD element substrate 1.

An optical multiplexer 10 is used to multiplex an optical signal having a wavelength in the 1.55 μm band from the transmission optical fiber 6 which is an input end of the optical fiber amplifier, with the pump light of the pump laser module 1. On the input side of the optical multiplexer 10, the lower optical fiber 6 for transmission and the optical fiber for the pump laser module are fusion-spliced.

On the other hand, on the output side of the optical multiplexer 10, an amplification optical fiber 7 is fusion-spliced. The optical multiplexer 1
Reference numeral 0 denotes an optical fiber coupler or a dielectric multilayer mirror. The amplification optical fiber 7 has a core doped with a rare earth element (Er ion).
Optical fibers are used.

The excitation light emitted from the active layer 2 of the excitation LD element substrate 1 of the excitation laser module 9 is condensed on the excitation laser module optical fiber 8 by the condensing lens 4 and passes through the optical multiplexer 10. The light enters the amplification optical fiber 7 to excite Er ions.

On the other hand, the signal light (1.55 μm) from the transmission optical fiber 6 connected to the input end of the optical fiber amplifier.
Light) also enters the amplification optical fiber 7 via the optical multiplexer 10.

In the amplification optical fiber 7, the signal light is
The stimulated emission of the excited Er ions causes amplification to a predetermined optical output. From the output side of the amplification optical fiber 7,
Is emitted.

By the way, in the conventional optical fiber amplifier,
The individual optical components of the pump laser module 9, the optical multiplexer 10, and the amplifying optical fiber 7 were separately manufactured and placed in the optical fiber amplifier.

[0012]

The above-mentioned conventional optical fiber amplifier has a problem that the device is large and it is difficult to reduce the size. The reason is as follows.

In the optical fiber amplifier, stimulated emission occurs when Er ions are excited in the amplification optical fiber, and the signal light gains and is amplified.

In order to amplify the signal light, a pump laser module that emits pump light and an amplification optical fiber, and an optical multiplexer that multiplexes different wavelengths of the pump light and the signal light and guides the signal to the amplification optical fiber are provided. Although required, each optical component is manufactured individually and placed in the optical fiber amplifier,
This is because a storage space is required.

As a prior art for miniaturizing an optical fiber amplifier, for example, Japanese Patent Laid-Open Publication No.
Japanese Patent Application Laid-Open Publication No. H11-163873 proposes a configuration using a silica-based waveguide as an optical multiplexer, but this configuration requires a storage space because the excitation light source and the optical multiplexer are not integrated. However, the above problems are not immediately solved.

For example, Japanese Patent Application Laid-Open No. Hei 5-21875 discloses a configuration in which signal light is passed through an active layer inside a pumping LD element, and the pumping light and the signal light are guided to an optical fiber by one condensing lens. However, in this case, since the wavelengths of the pump light and the signal light are different, the focal positions are different, and as a result, the loss of the pump light or the signal light increases when coupling with the optical fiber. Have a point.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide an optical fiber amplifier satisfying desired characteristics and achieving downsizing.

[0018]

An optical fiber amplifier according to the present invention for achieving the above object has a waveguide for transmitting signal light in addition to an active layer for generating pump light in a substrate of a pump LD element. It is.

In the present invention, on the input side of the pumping LD element substrate, a transmission optical fiber is provided at a position where signal light can enter the waveguide, and on one output side, an amplification optical fiber is provided. and excitation light generated in the active layer, the active
And a structure in which both optical outputs of signal light emitted through a waveguide provided separately from the conductive layer can be collected.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. In the optical fiber amplifier of the present invention, a waveguide (3 in FIG. 1) through which signal light passes is provided in the pumping LD element substrate (1 in FIG. 1), and the signal light can enter the waveguide on the input side of the waveguide. A transmission optical fiber (6 in FIG. 1) is provided as a means for optically transmitting the signal light, and an amplification optical fiber (7 in FIG. 1) is provided on the output side of the waveguide. It is arranged at a position where both optical outputs of the excitation light from the active layer (2 in FIG. 1) and the signal light emitted through the waveguide (3 in FIG. 1) can be collected.

In a preferred embodiment of the optical fiber amplifier of the present invention, the first condensing means (4 in FIG. 1) for condensing the pumping light output from the pumping LD element and propagating the pumping light output to the amplifying optical fiber. ) And a second light condensing means (4 'in FIG. 1) for condensing the optical output of the waveguide and propagating it to the amplification optical fiber, and multiplexing the outputs of the first and second light condensing means. Then, the light enters the amplification optical fiber.

In the optical fiber amplifier according to the embodiment of the present invention configured as described above, an active layer for generating pump light and a waveguide for passing signal light are provided in the substrate of the pump LD element, and the amplification is performed. The optical outputs of both the pump light and the signal light are multiplexed into the optical fiber for use and made incident.

As described above, since the pump laser module and the optical multiplexer, which are conventionally separate optical components, are combined into one, a space for accommodating the conventional optical multiplexer is not required, and the optical fiber amplifier is not required. Can be reduced in size.

[0024]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; In this embodiment, 1.5
An optical fiber amplifier for amplifying signal light in the 5 μm band will be described as an example.

FIG. 1 is a diagram showing the configuration of one embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an excitation LD element substrate, 2
Is an active layer, 3 is a waveguide, 4 and 4 'are condenser lenses, 5 is an electronic cooling element, 6 is a transmission optical fiber, and 7 is an amplification optical fiber.

In this embodiment, a semiconductor laser having an InGaAsP / InP-based crystal composition and having a wavelength in the 1.48 μm band is used as the pumping LD element substrate 1. The active layer 2 for generating excitation light has a strained multiple quantum well structure utilizing lattice mismatch of InGaAsP crystal, thereby enabling high-output operation.

The waveguide 4 is formed on the pumping LD element substrate 1 using InGaAsP as a core and InP as a cladding layer.

The size of the core of the waveguide 4 is the same as the size of the core of the transmission optical fiber 6 in order to reduce the coupling loss with the transmission optical fiber 6.

On the incident side of the excitation LD element substrate 1, the cores of the transmission line optical fiber 6 and the waveguide 3 are connected with an adhesive such that the centers of the respective cores coincide with each other.

On the exit side of the pumping LD element substrate 1, two condensing lenses 4, 4 'are arranged, and the first lens 4 is used to convert the pumping light generated in the active layer 2 into an amplifying optical fiber. 7. On the other hand, the second lens 4 ′ causes the signal light passing through the waveguide 3 to enter the amplification optical fiber 7.

The amplifying optical fiber 7 is an Er fiber in which an optical fiber is doped with a rare earth element, particularly Er ions.
A doped optical fiber is used.

The electronic cooling element 5 prevents the excitation LD element substrate 1 from lowering the optical output due to heat generation.
The D element substrate 1 is mounted on the thermoelectric cooler 5.

Next, the operation of the optical fiber amplifier of this embodiment shown in FIG. 1 will be described.

The signal light having a wavelength in the 1.55 μm band from the transmission optical fiber 6 passes through the waveguide 3 in the pumping LD element substrate 1 and then passes through the second condenser lens 4 ′. , Into the amplification optical fiber 7.

On the other hand, the excitation light generated in the active layer 2 in the excitation LD element substrate enters the amplification optical fiber 7 through the first condenser lens 4.

That is, the waveguide 3 of the excitation LD element substrate 1
And the excitation light from the active layer 2 are multiplexed by the first and second condenser lenses 4 and 4 ′, and are incident on the amplification optical fiber 7.

In the amplification optical fiber 7, Er is excited by pump light.
The ions are excited, and the signal light is gained and amplified by stimulated emission, and emitted from the output end of the amplification optical fiber 7.

In this embodiment, as the waveguide 4, I
Although nGaAsP is used as the core and InP is used as the clad, the present invention is not limited to this.

[0039]

As described above, according to the present invention,
This has the effect of making the optical fiber amplifier particularly small.

The reason is as follows. That is, in the present invention, an active layer for generating pump light and a waveguide through which signal light passes are provided in the substrate of the pump LD element, and the optical output of both the pump light and the signal light is multiplexed to the amplification optical fiber. And incident light.

For this reason, according to the present invention, since the pump laser module and the optical multiplexer, which have conventionally been separate optical components, are combined into one, the conventional optical multiplexer is housed. This eliminates the need for the space required for the optical fiber amplifier, and makes it possible to reduce the size of the optical fiber amplifier.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a configuration of a conventional optical amplifier.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 pump LD element substrate 2 active layer 3 waveguide 4, 4 ′ condenser lens 5 thermoelectric cooler 6 optical fiber for transmission line 7 amplification optical fiber 8 optical fiber for excitation laser module 9 excitation laser module 10 optical multiplexer

Claims (4)

(57) [Claims] 1. A is an active layer for generating excitation light with the excitation LD element substrate having a waveguide for propagating separately signal light, the input side, a signal light to the waveguide of the excitation LD element substrate Contact transmission optical fiber at a position capable of entering is disposed
On the output side, the optical outputs of both the pump light generated in the active layer of the pump LD element substrate and the signal light emitted through the waveguide provided separately from the active layer are collected. An optical fiber amplifier comprising an amplifying optical fiber at a position where light can be emitted. 2. An activity for generating excitation light on an excitation LD element substrate.
And a waveguide for transmitting the signal light . On the input side, the signal light is transmitted to a position where the signal light can enter the waveguide.
The transmission optical fiber is installed, and the output side is
Excitation light generated in the active layer and emitted through the waveguide
Amplification at a position where both optical outputs of the signal light can be collected
An optical fiber amplifier provided with an optical fiber, comprising: a first condensing lens for condensing an excitation light output from the active layer of the excitation LD element substrate and propagating the output to the amplification optical fiber; A second condensing lens for condensing the optical output of the waveguide of the LD element substrate and propagating the light output to the amplification optical fiber, wherein the outputs of the first and second condensing lenses are combined. Being waved and incident on the amplification optical fiber,
An optical fiber amplifier, characterized in that: 3. An active layer for generating excitation light, which is separate from an active layer in a substrate.
A semiconductor laser device for excitation provided with a waveguide through which a signal light passes; a transmission optical fiber disposed on an input side of the waveguide, for causing signal light to enter the waveguide; and an output side of the waveguide. In, the excitation light from the active layer of the semiconductor laser element for excitation, and an amplification optical fiber disposed so as to be able to collect the optical output of both the signal light emitted through the waveguide, Comprising, from the active layer
The pump light output and the signal light output from the waveguide are respectively
The light is multiplexed via a condenser lens and enters the amplification optical fiber.
Morphism is, the optical fiber amplifier, characterized in that. 4. Excitation in which a waveguide through which signal light passes is provided in a substrate.
Semiconductor laser element, and a signal light is disposed on the input side of the waveguide, and the signal light is transmitted to the waveguide.
An optical fiber for transmission to be incident, and the semiconductor laser for excitation on an output side of the waveguide.
Excitation light from the device and a signal emitted through the waveguide.
For amplification that is arranged so that both optical outputs of signal light can be collected
An optical fiber, comprising: a first light condensing means for condensing an excitation light output from the pumping semiconductor laser element and transmitting the light to the amplification optical fiber; Second condensing means for condensing the optical output and propagating the light to the amplifying optical fiber, wherein the outputs of the first and second condensing means are multiplexed and incident on the amplifying optical fiber. An optical fiber amplifier.