JPH05341232A - Optical module for optical amplifier - Google Patents

Abstract

PURPOSE:To provide an optical module for an optical amplifier miniaturizing and highly stabilizing the optical circuit of the optical amplifier with low loss by using various kinds of optical films of open constitution and integrating optical functions integrally. CONSTITUTION:An integrated type optical function device 22 vapor-depositing the branching filter film 50, the polarizing separation film 52, etc., of the open constitution on both surfaces of a parallel plane shape glass substrate 46 is arranged in the optical path of a signal beam and an exciting beam. This module is constituted so that a polarization independent optical isolator 26, a narrow band-pass filter 66 and an optical coupier 28 are arranged on the down stream side of the integrated type optical function device 22 and these optical function parts are housed in a casing 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical module for an optical amplifier using an optical fiber doped with a rare earth element such as erbium.

Recently, research on an optical amplifier capable of directly amplifying an optical signal has been actively conducted, and among them, rare earth elements (E
Attention has been focused on an optical amplifier in which an optical fiber doped with (r, Nb, Yb, etc.) and pumping light are combined.

This optical amplifier has no polarization dependence.
It has excellent characteristics such as low noise and small coupling loss with the optical fiber transmission line, and is expected to make it possible to dramatically increase the transmission relay distance in an optical fiber transmission system and distribute it to many optical signals. There is.

In order to realize such an optical amplifier,
An optical circuit that includes at least a demultiplexer that demultiplexes the signal light and pumping light, a coupler for extracting the monitor light, etc. is required, and the optical circuit of the optical amplifier that integrates the optical functional devices is small with low loss. There is a demand for an optical module for an optical amplifier that can be made stable and highly stable.

[0005]

2. Description of the Related Art Conventionally, an optical module arranged in a subsequent stage of an erbium-doped fiber is constructed by mounting individual optical devices such as a demultiplexer and a coupler on a substrate. A cube-shaped beam splitter 2 constructed by vapor-depositing an optical film 4 such as a branching film and a coupler film on the slope of one right-angled prism 3 and bonding the other right-angled prism 5 with an optical adhesive 6 as shown in FIG. Was adopted.

Since the optical film of such an optical device is sandwiched between right-angled prisms, it is referred to as a short structure and the optical path structure can be simplified.

[0007]

As described above, the conventional optical module for an optical amplifier uses an optical device such as a cube-shaped beam splitter using an optical film having a short structure. When the signal light output becomes high power, there is a problem that the optical adhesive, which is an organic substance, is deteriorated and damaged by light energy, and the reliability of the optical device is impaired.

Further, conventionally, since the cube-shaped optical devices are individually mounted on the substrate to form the optical module, there is a problem that the mounting area increases and the insertion loss increases. Therefore, the optical module for an optical amplifier is shown in FIG.
As shown in FIG.
It is desirable to adopt an optical device such as a beam splitter 7 having an open configuration in which an optical film 9 such as a coupler film is deposited.

However, if a large number of open films are simply vapor-deposited on independent glass substrates and these glass substrates are individually fixed to the substrate or housing, the positions of the glass substrates relative to each other,
It is difficult to control the angle precisely, and the temperature of each glass substrate,
There is a problem in that the angle deviation due to changes over time is added for the number of reflections and the stability of the optical path is low.

The present invention has been made in view of the above circumstances, and an object of the present invention is to integrate various optical functions by using various optical films having an open structure so that the light of an optical amplifier can be integrated. It is an object of the present invention to provide an optical module for an optical amplifier, which can reduce the size of a circuit with low loss and stabilize the circuit.

[0011]

In order to solve the above-mentioned problems, the present invention partially vapor-deposits various open optical films such as a demultiplexing film, a coupler film and a polarization separation film on the surface of a parallel plate glass substrate. Then, by adopting an optical path configuration for reflecting or refracting on the surface of one glass substrate and within the substrate as much as possible, various optical functions are integrated together to form an optical module for an optical amplifier.

Further, the optical circuit of the optical amplifier has various configurations according to the purpose of use of the optical amplifier.
The array configuration of the optical film, the isolator, etc. is optimized in order to integrate them in a more efficient optical path.

[0013]

According to the present invention, since the functions of various optical devices are integrated by the open optical film partially vapor-deposited on the glass substrate, the device is deteriorated by the high power of the excitation light and the signal light as in the prior art. It is possible to provide a small-sized and highly reliable optical module for an optical amplifier.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings. First, referring to FIG. 2, there is shown a block diagram of an optical amplifier to which the optical module of the present invention is applied. 10 is E doped with erbium (Er) in the core
It is an r-doped optical fiber, and signal light is input to this optical fiber through a coupler 12 and an optical isolator 14. The signal light branched by the coupler 12 is detected by the photodiode 16, and the signal light is monitored.

Reference numeral 18 denotes a post-stage optical circuit integrated type optical module which is arranged in a stage subsequent to the Er-doped optical fiber 10 which is the object of the present invention, and which includes a polarization coupler 21, a demultiplexer 24, an optical isolator 26, and an optical isolator 26. It is composed of a coupler 28 and a photodiode 30.

The P-polarized pumping light emitted from the pumping laser diode 20a and the S-polarized pumping light emitted from the laser diode 20b are combined by the polarization coupler 22 and propagated to the demultiplexer 24. This excitation light is sent to the demultiplexer 24.
And is input to the Er-doped optical fiber 10 to excite Er ions in the doped optical fiber 10 to a high energy level.

In such a state, for example, a wavelength of 1.
When 55 μm signal light is input, stimulated emission of light having the same wavelength as the signal light occurs, and the signal light is gradually amplified along the Er-doped optical fiber.

The amplified signal light passes through the demultiplexer 24, the optical isolator 26 and the optical coupler 28 and is sent out to the optical fiber transmission line. The signal light branched by the optical coupler 28 is detected by the photodiode 30 and feedback-controlled by an APC circuit (not shown) so that the amplified signal light power becomes constant.

Further, the drive circuit of the LDs 20a and 20b is turned on / off by the output of the photodiode 16 according to the input of the signal light. Next, with reference to FIG. 3, an embodiment of the optical module with integrated second-stage optical circuit 18 shown in FIG. 2 will be described.

The housing 32 is provided with four lens assemblies 34, 36, 38, 40 for converting a light beam emitted from an optical fiber into a collimated beam and a photodiode 42 for feedback control.

The lens assembly 34 is connected to the Er-doped optical fiber 10, and the lens assembly 36 is connected to a single mode optical fiber 44 which constitutes a transmission line.

Further, the lens assembly 38 has a wavelength of 1.48 μm or 0.98 by the polarization-maintaining optical fiber 58.
Excitation laser diode 20a which outputs P-polarized light of μm
The lens assembly 40 is connected to the pumping laser diode 20b that outputs S-polarized light having a wavelength of 1.48 μm or 0.98 μm by the polarization-maintaining optical fiber 60.

Reference numeral 22 denotes an integrated optical functional device, which is formed by vapor-depositing a plurality of types of optical films on both surfaces of a parallel plate glass substrate 46. The glass substrate 46 is arranged at a predetermined angle θ (for example, 45 °) with respect to the signal light input optical path.

A first non-reflection film 48 is vapor-deposited on a portion of the glass substrate 46 where the signal light is incident on the first surface 46a when viewed from the signal light input direction, and the signal light refracted on the first surface 46a is reflected on the second surface. A branching film 50 that transmits the signal light and reflects the excitation light is vapor-deposited at a portion intersecting with 46b.

Further, the polarization splitting film 5 is formed at the portion where the light reflected by the demultiplexing film 50 intersects the first surface 46a of the glass substrate 46.
2 is vapor-deposited, and a total reflection film 54 is vapor-deposited on a portion where the light reflected by the polarization separation film 52 intersects the second surface 46b. A portion where the light reflected by the total reflection film 54 intersects the first surface 46a. A second antireflection film 56 is vapor-deposited on the.

Reference numeral 26 is a polarization-independent optical isolator, which is constituted by a tapered rutile type optical isolator as described in, for example, Japanese Patent Publication No. 61-58809.
On the downstream side of the polarization independent optical isolator 26, wavelengths of 1.
A narrow band bandpass filter 66 that transmits only 55 μm signal light is inserted.

Reference numeral 28 denotes an optical coupler formed by vapor-depositing a coupler film 64 on the surface of the parallel plate glass substrate 62. Most of the signal light is transmitted through the optical coupler 28 and coupled to the single mode optical fiber 44. However, a part of the signal light is branched by the optical coupler 28 and detected by the photodiode 42. The coupler film 64 is formed of a polarization-independent coupler film formed of a high refractive material or a narrow bandpass filter formed of a dielectric multilayer film.

Therefore, the wavelength of 1.
The 48 μm S-polarized excitation light passes through the second non-reflection film 56, is totally reflected by the total reflection film 54, and enters the polarization separation film 52.
It is reflected here again.

On the other hand, the wavelength of 1.4 emitted from the LD 20a is 1.4.
The 8 μm P-polarized excitation light passes through the polarization separation film 52, and S
It is combined with the polarized light and enters the branching film 50. The excitation light is reflected by the demultiplexing film 50, passes through the first non-reflective film 48, enters the Er-doped optical fiber 10, and excites Er ions to a high energy level.

The signal light amplified by the Er-doped optical fiber 10 is made into a collimated beam by the lens assembly 34 fixed to the housing 32, and the first non-reflection film 48 and the demultiplexing film 50 formed on the glass substrate 46 are made. The optical coupler 28 is transmitted through the polarization independent optical isolator 26 and the narrow band bandpass filter 66 that transmits only the signal light.
Incident on.

A part of the signal light is reflected and branched to the photodiode 42 by the coupler film 64 of the optical coupler 28, and most of the signal light passes through the optical coupler 28 and is coupled to the single mode optical fiber 44 via the lens assembly 36. To be done.

According to this embodiment, since the integrated optical functional device 22 in which optical films such as the demultiplexing film 50, the polarization separation film 52, and the total reflection film 54 are vapor-deposited on both surfaces of the glass substrate 46 is used, the polarization combining is performed. Since the optical module for backward pumping the pumping light whose output has been increased to the Er-doped optical fiber 10 can be configured with low loss in a small size and with high stability, the optical amplifier can be downsized and the performance can be improved.

As a modification of the integrated optical functional device 22 described above, a configuration in which the second antireflection film 56 is removed and an antireflection film is deposited at the position of the total reflection film 54 can be considered. In this case, the S-polarized light is made incident on the newly evaporated non-reflection film from the horizontal direction in FIG. The incident position of P-polarized light is shown in FIG.
It is similar to the embodiment of.

Another embodiment of the integrated optical functional device used in the optical module of the present invention will be described below with reference to FIGS. 4 to 6. Integrated optical functional device 2 of FIG.
2A is a parallel plate glass substrate 46, the first non-reflective film 48 is vapor-deposited on the portion of the first surface 46a where the signal light is incident when viewed from the signal light input direction, and the signal light refracted by the first surface 46a A demultiplexing film 50 that transmits the signal light and reflects the excitation light is vapor-deposited on the portion that intersects the two surfaces 46b.

Further, the total reflection film 6 is formed on the portion where the light reflected by the demultiplexing film 50 intersects the first surface 46a of the glass substrate 46.
8 is vapor-deposited, and the light reflected by the total reflection film 68 is the second surface 46.
The second antireflection film 70 is formed by vapor deposition on the portion intersecting with b.

According to this embodiment, the excitation light incident from the direction of the arrow A passes through the second non-reflection film 70 and is totally reflected.
The light is totally reflected at 8, is reflected by the branching film 50, is transmitted through the first non-reflection film 48, and is input to the Er-doped optical fiber 10.

Another configuration of this embodiment is the first configuration described in FIG.
It is similar to the embodiment. According to the present embodiment, only one excitation light source can be provided, but the structure of the optical module can be simplified accordingly.

Referring to FIG. 5, there is shown a schematic configuration of an optical module adopting an integrated optical functional device 22B according to still another embodiment of the present invention. The integrated optical function device 22B of this embodiment is configured as follows.

That is, the first non-reflective film 48 is vapor-deposited on the portion of the parallel plate glass substrate 46 where the signal light is incident on the first surface 46a when viewed from the signal light input direction, and the signal is refracted on the first surface 46a. A demultiplexing film 50 that transmits the signal light and reflects the excitation light is deposited on a portion where the light intersects the second surface 46b.

Further, a first total reflection film 68 is vapor-deposited on the portion where the light reflected by the demultiplexing film 50 intersects the first surface 46a of the glass substrate 46, and the light reflected by the first total reflection film 68 is The polarization separation film 72 is vapor-deposited on the portion intersecting with the two surfaces 46b.

Further, a second total reflection film 74 is vapor-deposited on the portion where the light reflected by the polarization splitting film 72 intersects the first surface 46a, and the light totally reflected by the second total reflection film 74 becomes the second surface 46b. The second antireflection film 76 is deposited on the intersecting portion.

When the integrated optical functional device 22B is configured in this way, the S-polarized excitation light is incident on the second antireflection film 76 from the direction of arrow A, and the P-polarized excitation light is polarized and separated from the direction of arrow B. It is incident on the film 72. The arrangement of the other functional components of this embodiment is the same as that of the first embodiment described above.

By adopting the configuration of this embodiment, all the light incident on the integrated optical function device 22B can be made incident in the horizontal direction, so that the optical module can be further miniaturized.

As a modified example of this embodiment, the second non-reflection film 76 formed on the second surface 46b is deleted and the second total reflection film 74 is removed.
A configuration in which the second antireflection film is vapor-deposited at the position is conceivable. According to this modification, the S-polarized excitation light is arranged so as to enter the second non-reflection film from above.

Next, with reference to FIG. 6, the structure of an optical module employing an integrated optical functional device according to still another embodiment of the present invention will be described. According to the present embodiment, the first non-reflective film 48 is vapor-deposited on the portion of the parallel plate glass substrate 46 where the signal light is incident when viewed from the signal light input direction, and the signal is refracted on the first surface 46a. A demultiplexing film 50 that transmits the signal light and reflects the excitation light is deposited on a portion where the light intersects the second surface 46b. Further, a second non-reflective film 78 is deposited on the portion where the light reflected by the demultiplexing film 50 intersects the first surface 46a.

According to this structure, the excitation light is incident on the second antireflection film in the direction of arrow A, and the excitation light refracted by the first surface 46a is reflected by the demultiplexing film 50 and transmitted through the first antireflection film 48. Then, it is input to the Er optical fiber 10.

As a modification of this embodiment, a demultiplexing film is vapor-deposited on the first antireflection film 48 portion of the first surface 46a, and the second surface 46b is formed.
A configuration in which a non-reflection film is vapor-deposited on the portion where the demultiplexing film 50 of FIG. According to this modification, the excitation light is arranged so as to be incident on the portion of the first surface 46a on which the demultiplexing film is deposited, on which the signal light is incident.

[0048]

Since the present invention is configured as described above in detail, the optical circuit of the optical amplifier can be downsized and highly stabilized with low loss, and the downsizing and high performance of the optical amplifier can be realized. Also,
Since the integrated optical functional device in which various kinds of optical films having an open structure are vapor-deposited on the glass substrate is adopted, the optical module for an optical amplifier can be downsized and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a short structure and an open structure of an optical film.

FIG. 2 is a block diagram of an optical amplifier to which the present invention is applied.

FIG. 3 is a sectional view of an embodiment of the present invention.

FIG. 4 is an optical component layout view of another embodiment of the present invention.

FIG. 5 is an optical component layout view of a further embodiment of the present invention.

FIG. 6 is a layout view of optical components according to still another embodiment of the present invention.

[Explanation of symbols]

 10 Er-doped optical fiber 18 Post-stage optical circuit integrated optical module 21 Polarization coupler 22, 22A, 22B, 22C Integrated optical functional device 24 Demultiplexer 26 Optical isolator 28 Optical coupler 46 Parallel plate glass substrate 50 Demultiplexing film 52, 72 Polarization Separation Film 54,68 Total Reflection Film 64 Coupler Film 66 Narrow Band Bandpass Filter

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location H01S 3/10 Z 8934-4M (72) Inventor Teruhiro Kubo 2 Kitaichijo Nishi, Chuo-ku, Sapporo -1 Within Fujitsu Hokkaido Digital Technology Co., Ltd.

Claims (12)

[Claims] 1. An optical amplifier optical module including at least a demultiplexing film that transmits signal light and reflects excitation light, a coupler film, and a light receiving element, wherein the parallel plate is inclined at a predetermined angle with respect to a signal light input optical path. The glass substrate (46) is arranged, and the first surface (4
The first non-reflective film (48) is formed on the portion where the signal light of 6a) enters, and the signal light refracted on the first surface (46a) transmits the signal light to the portion intersecting the second surface (46b). Splitter film that reflects the excitation light
(50) is formed and the light reflected by the demultiplexing film (50) is a glass substrate.
A polarization separation film (52) is formed at a portion intersecting the first surface (46a) of (46), and the light reflected by the polarization separation film (52) is reflected by the second surface (46).
A total reflection film (54) is formed at a portion intersecting with b), and a second antireflection film (56) is formed at a portion where the light reflected by the total reflection film (54) intersects with the first surface (46a). An optical module for an optical amplifier, which is characterized by being formed. 2. The second antireflection film (56) on the first surface (46a) of the glass substrate (46) is deleted, and the total reflection film (54) on the second surface (46b).
The optical module for an optical amplifier according to claim 1, wherein a third antireflection film is formed at the position instead of the above. 3. An optical amplifier optical module including a demultiplexing film that transmits at least signal light and reflects excitation light, a coupler film, and a light receiving element, wherein the parallel plate is inclined at a predetermined angle with respect to the signal light input optical path. The glass substrate (46) is arranged, and the first surface (4
The first non-reflective film (48) is formed on the portion where the signal light of 6a) enters, and the signal light refracted on the first surface (46a) transmits the signal light to the portion intersecting the second surface (46b). Splitter film that reflects the excitation light
(50) is formed and the light reflected by the branching film (50) is the glass substrate.
A total reflection film (68) is formed on the portion of (46) that intersects the first surface (46a), and the light reflected by the total reflection film (68) forms a first portion on the portion that intersects the second surface (46b). 2. An optical module for an optical amplifier, characterized in that a non-reflection film (70) is formed. 4. An optical amplifier optical module including a demultiplexing film that transmits at least signal light and reflects excitation light, a coupler film, and a light receiving element, wherein the parallel plate is inclined at a predetermined angle with respect to the signal light input optical path. The glass substrate (46) is arranged, and the first surface (4
The first non-reflective film (48) is formed on the portion where the signal light of 6a) enters, and the signal light refracted on the first surface (46a) transmits the signal light to the portion intersecting the second surface (46b). Splitter film that reflects the excitation light
(50) is formed and the light reflected by the branching film (50) is the glass substrate.
The first total reflection film (68) is formed on the portion intersecting the first surface (46a) of (46).
And the light reflected by the first total reflection film (68) forms the second surface.
A polarization separation film (72) is formed at a portion intersecting with (46b), and a second total reflection film (74) is formed at a portion where light reflected by the polarization separation film (72) intersects with the first surface (46a). Forming a second total reflection film (74)
An optical module for an optical amplifier, characterized in that a second non-reflective film (76) is formed at a portion where the light reflected by (2) intersects the second surface (46b). 5. The second antireflection film (76) formed on the second surface (46b) of the glass substrate (46) is removed, and the second total reflection film (74) formed on the first surface (46a). 5. The optical module for an optical amplifier according to claim 4, wherein a second antireflection film (76) is formed at that position instead of (4). 6. An optical amplifier optical module including a demultiplexing film that transmits at least signal light and reflects excitation light, a coupler film, and a light receiving element, wherein the parallel plate is inclined at a predetermined angle with respect to the signal light input optical path. The glass substrate (46) is arranged, and the first surface (4
The first non-reflective film (48) is formed on the portion where the signal light of 6a) enters, and the signal light refracted on the first surface (46a) transmits the signal light to the portion intersecting the second surface (46b). Splitter film that reflects the excitation light
(50) is formed and the light reflected by the branching film (50) is the glass substrate.
The second non-reflective film (78) is formed on the portion intersecting the first surface (46a) of (46).
An optical module for an optical amplifier, characterized in that 7. An optical amplifier optical module including a demultiplexing film that transmits at least signal light and reflects excitation light, a coupler film, and a light receiving element, wherein the parallel plate is inclined at a predetermined angle with respect to the signal light input optical path. The glass substrate (46) is arranged, and the first surface (4
A branching film (50) that transmits the signal light and reflects the excitation light is formed in the portion where the signal light of 6a) is incident, and the signal light refracted by the first surface (46a) is the second surface (46b). An optical module for an optical amplifier, characterized in that a non-reflective film is formed at the intersecting portion. 8. The optical amplifier according to claim 1, wherein a polarization-independent optical isolator (26) is inserted in the optical path of the signal light transmitted through the glass substrate (46). Optical module. 9. A parallel plate glass substrate (62) having a coupler film deposited on at least one surface thereof is arranged on the downstream side of the polarization-independent optical isolator (26) in the signal light propagation direction. Item 9. An optical module for an optical amplifier according to item 8. 10. The polarization independent optical isolator (26)
10. The optical module for an optical amplifier according to claim 9, wherein a narrow band bandpass filter (66) for transmitting only signal light is inserted between the glass substrate (62) with the coupler film. 11. The optical module for an optical amplifier according to claim 9, wherein the coupler film is a polarization independent coupler film formed of a high refractive index material. 12. The optical module for an optical amplifier according to claim 9, wherein the coupler film is formed of a narrow bandpass filter of a dielectric multilayer film.