JP3428874B2 - Composite module for 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 a composite module for optical fiber amplifier used in optical communication.

[0002]

2. Description of the Related Art An optical fiber amplifier is manufactured by fusion-splicing a plurality of optical components such as an erbium-doped fiber and an optical isolator. In recent years, with the rapid development of optical communication, due to demands for cost reduction of optical fiber amplifiers, shortening of assembly work time, reduction of mounting area, etc.,
Composite modules in which the plurality of optical components are integrated into one package have been used.

[0003]

By the way, in the above-mentioned composite module, the optical path in the package becomes complicated due to the integration of a plurality of optical components. Therefore, in the composite module provided with the light receiver for monitoring the signal light, in addition to the signal light to be monitored, stray light reflected by the end faces of a plurality of optical components arranged in the package enters the light receiver, This stray light may cause a malfunction. For this reason, the optical fiber amplifier using the above composite module has a concern in terms of stability and reliability of operation over a long period of time.

The present invention has been made in view of the above points, and by preventing stray light from entering the light receiver, it is possible to suppress the occurrence of malfunction and achieve stability and reliability for a long period of time. An object is to provide a composite module for an optical fiber amplifier.

[0005]

In order to achieve the above object, in a first optical fiber amplifier composite module of the present invention, a first light guide for introducing signal light and a second light for guiding signal light are provided. A guide and a third light guide for introducing pumping light are attached to the box-shaped package, and the box-shaped package is integrated with a plurality of optical components including an optical isolator and a photodetector for monitoring a part of the signal light. At the same time, the inside is divided into an area on the excitation light incident side and an area on the light receiver arrangement side by a holding component that holds and fixes the optical isolator in the box-shaped package.

To achieve the above object, in the second optical fiber amplifier composite module of the present invention, the first optical guide for introducing the signal light and the second optical guide for introducing the signal light are provided.
And a light source for excitation and a collimating means for collimating the excitation light emitted from the light source are attached to a box type package, and the box type package includes an optical isolator and a light receiver for monitoring a part of the signal light. A plurality of optical components including are integrated, and the inside is divided into an area where the excitation light source is installed and an area on the side where the light receiver is arranged by a holding component that holds and fixes the optical isolator in the box-shaped package. It has a different configuration.

Further, in order to achieve the above object, in the third optical fiber amplifier composite module of the present invention, the first optical guide for introducing the signal light and the signal light and the rare earth-doped fiber or A second optical guide connected to the rare earth-doped fiber via a normal optical fiber is attached to a box-shaped package, and the box-shaped package includes a plurality of optical isolators and a light receiver for monitoring a part of the signal light. The optical components are integrated, and an area where the pumping light remaining inside the rare earth-doped fiber is incident by a holding component that holds and fixes the optical isolator in the box-shaped package and an area on the side where the optical receiver is arranged. The structure is divided into and.

Preferably, the holding component is formed of metal, ceramics, opaque plastic that blocks the signal light and the excitation light, or glass whose surface is coated with a coating film that blocks the signal light and the excitation light.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a composite module for an optical fiber amplifier according to the present invention (hereinafter referred to as "composite module").
FIG. 1 shows a rear excitation type composite module as one embodiment.
It will be described in detail based on. Here, in the present specification, backward pumping refers to a case where pumping light is incident on a fiber for optical amplification, for example, an erbium-doped fiber, in a direction opposite to the transmission direction of signal light, and forward pumping is pumping light. Is incident in the same direction as the signal light transmission direction.

The composite module 1, as shown in FIG.
A box-type package (hereinafter referred to as “package”) 2 is provided with a first fiber component 3, a second fiber component 4, a third fiber component 5, an interference film filter 6, an optical isolator 7, a beam splitter 8 and a photodiode 9. ing. The package 2 has the interference film filter 6, the optical isolator 7, and the beam splitter 8 integrated therein, and the holding component 10 for holding and fixing the optical isolator 7 in the package 2 allows the inside to be the excitation light incident side in the first area. A1
And a second area A2 on the side where the photodiode 9 is arranged. Thereby, the first area A1 and the second area A2 inside the package 2 are blocked, and stray light does not enter from the first area A1 to the second area A2.

The first fiber component 3 is for injecting a signal light of wavelength λ1 into the package 2, and includes a fiber for optical amplification, for example, an erbium-doped fiber or a normal optical fiber 3a connected to it, and an end portion thereof. It has a holder 3b to be attached. The holder 3b is attached to one side of the package 2, and a collimator (not shown) such as a lens for collimating the signal light is housed inside. A rare earth-doped fiber, for example, an erbium-doped fiber is used as the optical amplification fiber.

The second fiber component 4 is an optical fiber 4a.
And a holder 4b attached to its end. The holder 4b has the same structure as the holder 3b, and is attached to the other side of the package 2 so as to face the holder 3b. As a result, the composite module 1 forms a transmission path of signal light which becomes the first fiber component 3, the interference film filter 6, the optical isolator 7, the beam splitter 8 and the second fiber component 4 in the package 2.

The third fiber component 5 is for inputting pumping light of wavelength λ2 into the package 2 and is composed of an optical fiber 5a.
And a holder 5b attached to the end thereof. The holder 5b is configured similarly to the holder 3b, and is attached to the package 2 so that the incident excitation light is reflected by the interference film filter 6 and is transmitted to the first fiber component 3 side.

The interference film filter 6 is a filter in which an interference film is formed on the surface of glass or the like, and as shown in the drawing, an optical path of the excitation light is transmitted so that the reflected excitation light is transmitted to the first fiber component 3 side. And is inclined by a predetermined angle. The optical isolator 7 is an optical component that transmits signal light only in the arrow direction, and is held and fixed by the holding component 10 at approximately the center of the package 2. Here, the holding component 10 partitions the inside of the package 2 into the first area A1 and the second area A2 as described above.

The beam splitter 8 is an optical isolator 7.
An optical component that transmits the signal light that has passed through to the second fiber component 4 side and reflects a part of the signal light (reflectance of about 1 to 10%) to reflect it to the photodiode 9 side.
The fiber component 4 and the optical isolator 7 are arranged so as to be inclined at a predetermined angle with respect to the transmission path of the signal light. The reflectance of the beam splitter 8 is usually selected in the range of about 1 to 10%, but the lower the reflectance, the less the loss of signal light, and the more efficient the composite module can be obtained.

The photodiode 9 monitors a part of the signal light reflected by the beam splitter 8. The photodiode 9 has a function of monitoring a part of the signal light, and it is needless to say that the photodiode 9 is not limited to the photodiode and is not limited to the photodiode. The holding component 10 holds the optical isolator 7 and divides the inside of the package 2 into a first area A1 on the excitation light incident side and a second area A2 on the photodiode 9 arrangement side. It has a cylindrical hole for holding it without a gap, and is shaped like a collar or a block so as to contact the outer wall of the package 2 without a gap. As the material of the holding component 10,
For example, metal, ceramics, opaque plastic that blocks the signal light of wavelength λ1 and pumping light of wavelength λ2, or glass whose surface is coated with a coating film that blocks the signal light and pumping light can be used.

The composite module 1 of this embodiment is configured as described above and is used as follows when the optical fiber amplifier is pumped backward. First, the third fiber component 5
When pumping light of wavelength λ2 is injected into the package 2 from
The light is reflected by the interference film filter 6 and enters the first fiber component 3. Then, in the first fiber component 3, the signal light having the wavelength λ1 amplified by stimulated emission in the optical fiber 3a is emitted into the package 2.

The signal light passes through the interference film filter 6, the optical isolator 7 and the beam splitter 8 and is incident on the second fiber component 4. At the same time, a part of the signal light is reflected by the beam splitter 8 and emitted to the photodiode 9. , Used for monitoring signal light. By the way, when the composite module according to the prior art is used for the backward pumping type optical fiber amplifier, from the first fiber component 3 and the third fiber component 5,
For example, it is assumed that signal light and excitation light of 100 mW or more are emitted. On the other hand, in the beam splitter 8, if the reflectance is selected to be about 1% for the above reason, the signal light of about 1 mW enters the photodiode 9.

On the other hand, in the first area A1 of the package 2, the third fiber component 5 to the first fiber component 3 due to the reflection of the excitation light on the interference film filter 6 and the holder 3b.
Estimating the coupling loss to 10%, stray light of about 10 mW exists. Therefore, in the composite module 1, this stray light enters the photodiode 9 on the second area A2 side without the holding component 10. As a result, in addition to the regular signal light, the photodiode 9 may malfunction due to stray light whose light level is about 10 times higher than that of the monitor light.

However, in the present invention, the holding component 10
Divides the package 2 into a first area A1 and a second area A2 so that the stray light does not enter from the first area A1 side to the second area A2 side. Therefore, in the composite module 1 of the present embodiment, malfunction of the photodiode 9 due to the stray light is suppressed, so that stability and reliability of operation for a long period are guaranteed. Moreover, the holding component 10
Since the optical isolator 7 is simply held and fixed in the package 2, the structure is simple, and it can be easily applied to an existing package to assemble the composite module of the present invention.

On the other hand, when the composite module of the present invention is used as a forward excitation type composite module, each component is arranged as shown in FIG. Here, in each composite module described below, FIG.
The same components as those of the composite module 1 of 1 are assigned the same reference numerals and detailed description thereof will be omitted.

That is, the composite module 20 has a transmission path of signal light (wavelength λ1) which becomes the first fiber component 3, the beam splitter 8, the optical isolator 7, the interference film filter 6 and the second fiber component 4 in the package 2. A part of the signal light that has been formed and reflected by the beam splitter 8 is monitored by the photodiode 9. The excitation light (wavelength λ2) is made incident from the third fiber component 5, reflected by the interference film filter 6 and made incident on the second fiber component 4.

In this case, unlike the composite module 1, the optical fiber 4a is an erbium-doped fiber or an ordinary optical fiber connected thereto, and the optical fiber 3a is an ordinary optical fiber. In this way, since the composite module 20 has the forward pumping type configuration, similar to a normal optical fiber amplifier, for example, about 1 mW of signal light is output from the first fiber component 3 and the third fiber component 5 is output from the third fiber component 5. Is 1
When pumping light of 00 mW or more is emitted and the reflectance of the beam splitter 8 is about 1%, the signal light of about 0.01 mW is incident on the photodiode 9.

Therefore, the forward excitation type composite module 20
In the case of, in the same manner as in the case of the composite module 1, in the second area A2 of the package 2, the third fiber component 5 accompanying the reflection of the excitation light with the interference film filter 6 and the holder 4b.
When the coupling loss to the second fiber component 4 is estimated to be 10%, stray light of about 10 mW exists. Therefore, this stray light is about 1000 times larger than the level of light monitored by the photodiode 9 (= about 0.01 mW).

Therefore, the forward excitation type composite module 2
At 0, the holding component 10 divides the package 2 into a first area A1 and a second area A2 to prevent stray light from entering from the first area A1 to the second area A2. Compared with the module 1, it is more significant in suppressing malfunction of the photodiode 9 due to the stray light and ensuring stability and reliability of operation for a long period of time.

The composite module of the present invention includes the backward pumped composite module 1 shown in FIG. 1 in which pumping light is incident into the package 2 using the third fiber component 5, and the composite module shown in FIG. It may be configured like the module 30. That is, the composite module 30 includes the laser diode (hereinafter simply referred to as “LD”) element 1 which is a light source for excitation.
1 and a collimating lens 12 are arranged on the first area A1 side of the package 2 so that collimated light can be emitted.

In the composite module 30 in which the LD element 11 which is a light source for excitation is arranged in the package 2 in such a positional relation that the collimated light can be emitted by the collimator lens 12, the rear excitation type composite module 1 is specified. The numerical aperture (NA) due to the fibers when the excitation light is incident on the package 2 using the third fiber component 5, is reflected by the interference film filter 6 and is coupled to the first fiber component 3 is as follows. Unlike the case where the coupling is about 0.1 to 0.2, the numerical aperture (NA) of the LD element 11 for the excitation light source is about 0.6, which is very large. Therefore, the composite module 30 has a larger coupling loss than the coupling between the fibers, and the stray light is also large by the coupling loss.

Further, as described above, the light source for excitation L
Since the numerical aperture (NA) of the D element 11 is as large as about 0.6, when the radial laser light emitted from the LD element 11 is made incident on the collimator lens 12, laser light outside the effective NA is reflected. There is a possibility that it will be diffused due to factors such as stray light. Therefore, in the backward excitation type composite module 30, stray light exists in the package 2 in the composite module 1 or more. Therefore, in the composite module 30, the holding component 10 moves the inside of the package 2 into the first area A.
It is divided into 1 and the second area A2, from the first area A1 to the second area
By preventing the stray light from entering the area A2, the malfunction of the photodiode 9 due to the stray light is suppressed, which is more significant in ensuring the stability and reliability of the operation for a long period of time.

For the same reason, the LD element 11 which is a light source for excitation is arranged in the package 2 in a positional relationship such that the collimated lens 12 can emit the collimated light. Module 4
It goes without saying that 0 becomes even more significant in ensuring the stability and reliability of long-term operation.

Further, in addition to the forward pumping type or backward pumping type composite module as described above, like the composite module 50 shown in FIG. 5, the signal light is transmitted through the first fiber component 3, the beam splitter 8, the optical isolator 7, The interference film filter 13 and the second fiber component 14 may be formed with a signal light transmission path, and a part of the signal light reflected by the beam splitter 8 may be monitored by the photodiode 9.

Here, in the interference film filter 13, as shown in the figure, when a part of the excitation light of the wavelength λ2 is incident on the composite module 50 from the rear side through the optical fiber 14a,
It is installed so as to block a part of the excitation light, and one that transmits the signal light (wavelength λ1) and reflects the excitation light (wavelength λ2) is selected. The illustrated composite module 50 is
Unlike the above-mentioned composite modules, the pump light is packaged 2
The third fiber component 5 to be incident inside and the LD element 11 which is a light source for excitation are not built in the package 2,
The second optical fiber component 14 uses an erbium-doped fiber or an ordinary optical fiber connected to an erbium-doped fiber as the optical fiber 14a.

Therefore, also in the composite module 50 shown in FIG. 5, the first fiber component 3 and the second fiber component 14 are
When the coupling loss of the signal light between and exists as stray light in the package 2 and a part of the pumping light of wavelength λ2 enters the composite module 50 from the rear stage side through the optical fiber 14a as shown in the figure. Also, the interference film filter 1
It is highly possible that the excitation light having the wavelength λ2 remains in the first area A1 of the package 2 as stray light due to reflection by the light source 3 and the like.

However, the composite module 50 is provided with the holding component 10 to divide the first area A1 and the second area A2. Therefore, in the composite module 50, the stray light described above is prevented from entering the first area A1 to the second area A2, and malfunction of the photodiode 9 due to stray light is suppressed, and the safety and reliability of long-term operation are improved. Is guaranteed.

[0034]

As is clear from the above description, according to the present invention, by preventing the stray light from entering the light receiver, the occurrence of malfunction can be suppressed and the stability and the reliability can be achieved for a long time. A possible composite module for optical fiber amplifier can be provided. Moreover, according to the present invention, since the holding component only holds and fixes the optical isolator in the package, the structure is simple and can be easily applied to an existing package to assemble the composite module of the present invention. .

[Brief description of drawings]

FIG. 1 shows a first embodiment of the present invention and is a front view showing a schematic configuration of a backward pumping type composite module for optical fiber amplifiers.

FIG. 2 shows a second embodiment of the present invention and is a front view showing a schematic configuration of a forward pumping type composite module for optical fiber amplifiers.

FIG. 3 shows a third embodiment of the present invention, and is a front view showing a schematic configuration of a backward-pumped composite module for optical fiber amplifiers having an LD element built therein.

FIG. 4 shows a fourth embodiment of the present invention and is a front view showing a schematic configuration of a forward-pumping composite module for optical fiber amplifiers having an LD element built therein.

FIG. 5 shows a fifth embodiment of the present invention and is a front view showing a schematic configuration of a fiber amplifier composite module used in the preceding stage of an erbium-doped optical fiber at the time of backward pumping.

[Explanation of symbols]

1 compound module 2 packages 3 First fiber component 3a optical fiber 3b holder 4 Second fiber parts 4a optical fiber 4b holder 5 Third fiber component 5a optical fiber 5b holder 6 Interference membrane filter 7 Optical isolator 8 beam splitter 9 Photodiode 10 holding parts 11 LD element 12 Collimating lens 13 Interference membrane filter 14 Second optical fiber parts 14a optical fiber 20 compound modules 30 compound modules 40 compound modules 50 composite modules A1 first area (excitation light incident side area) A2 2nd area (area on the side where the receiver is located) λ1 Signal light wavelength λ2 Excitation light wavelength

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-7-335956 (JP, A) JP-A-7-174933 (JP, A) JP-A-5-341233 (JP, A) JP-A-8- 254723 (JP, A) JP-A-9-93202 (JP, A) JP-A-11-97777 (JP, A) JP-A-10-256672 (JP, A) JP-A-8-179157 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01S 3/00-3/30

Claims (4)

(57) [Claims] 1. A first light guide for introducing signal light, a second light guide for deriving signal light, and a third light guide for introducing pumping light.
Is attached to a box-shaped package, and the box-shaped package is integrated with a plurality of optical components including an optical isolator and a light receiver for monitoring a part of the signal light.
A holding module for holding and fixing the optical isolator in the box-shaped package divides the inside into an area on the excitation light incident side and an area on the light receiver arrangement side, which is characterized in that . 2. A box-shaped package comprising a first light guide for introducing signal light, a second light guide for deriving signal light, a pumping light source and a collimating means for collimating pumping light emitted from the light source. The box-type package is attached with a plurality of optical components including an optical isolator and a light receiver for monitoring a part of the signal light, and a holding component for holding and fixing the optical isolator in the box-type package. The inside is divided into an area in which the excitation light source is installed and an area on the side where the photodetector is arranged, the composite module for an optical fiber amplifier. 3. A first light guide for introducing the signal light, and a second light guide for guiding the signal light and connected to the rare earth-doped fiber via a rare earth-doped fiber or an ordinary optical fiber. The box-shaped package is attached to the box-type package, and the box-type package has a plurality of optical components including an optical isolator and a photodetector for monitoring a part of the signal light, and holds the optical isolator in the box-type package. A composite module for an optical fiber amplifier, wherein the holding component to be fixed divides the inside into an area where the excitation light remaining in the rare earth-doped fiber is incident and an area on the side where the photodetector is arranged. 4. The holding component is formed of metal, ceramics, opaque plastic that blocks the signal light and excitation light, or glass whose surface is coated with a coating film that blocks the signal light and excitation light. A composite module for an optical fiber amplifier according to any one of items 1 to 3.