JPH05341233A - Optical module for optical amplifier - Google Patents

Abstract

PURPOSE:To realize 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:The shapes of an exciting prism 46 forming a polarizing separation film 48 and a branching filter film 50 and a coupler prism 56 forming a coupler film 58 are optimized and further a setting angle to an optical path is adjusted and inserted into the optical path of a signal beam and an exciting beam. A polarization independent optical isolator 64 is inserted between the exciting prism 46 and the coupler prism 56. The shapes of the exciting prism 46 and the coupler prism 56 are optimized and further by adjusting an angle to the optical path, the signal beam or the exciting beam is coupled to four pieces of lens assembly 34, 36, 38, 40 arranged so as to be in parallel or intersect orthogonally each other.

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 including at least a demultiplexer for demultiplexing the signal light and the pump light, a coupler for extracting the monitor light, etc. is required, and an optical circuit arranged in front of the erbium-doped optical fiber and an optical circuit arranged in the rear. There is a demand for an optical module for an optical amplifier, which is a compact package.

[0005]

2. Description of the Related Art Conventionally, a front optical module and a rear optical module are separately arranged in front of an erbium-doped optical fiber, and each optical module has an individual optical device such as a demultiplexer and a coupler. It is configured by being mounted on a substrate.

As an optical device, an optical film 4 such as a demultiplexing film or a coupler film is vapor-deposited on the slope of one right-angle prism 3 as shown in FIG. The cube-shaped beam splitter 2 configured by bonding 5 is used.

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.

[0008]

As described above, since 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, the pumping light output is Also, 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, cube-shaped optical devices are individually mounted on a substrate to form a front optical module and a rear optical module, so that there is a problem that the mounting area increases and the insertion loss increases.

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, it is difficult to precisely control the mutual positions and angles of the glass substrates. However, there has been a problem that the angle deviation due to the temperature of each glass substrate, the change over time, etc. is added for the number of times of reflection, and the stability of the optical path is low.

Since there is an optical film whose incident angle is limited depending on the type of the optical film, the light beam must be set in the optical module unless the shape of the prism for reflecting or refracting the light beam and the angle with respect to the light beam are set optimally. There arises a problem that the optical ports for entering and exiting are oriented in various directions with respect to the main body substrate of the module.

The present invention has been made in view of the above circumstances, and the optical circuit of an optical amplifier can be miniaturized with low loss by integrally integrating optical functions by using various optical films having an open structure. , To provide an optical module for an optical amplifier that can be stabilized.

[0013]

In order to solve the above-mentioned problems, the present invention optimizes prism shapes such as a demultiplexing prism and a coupler prism, and a demultiplexing film is formed on the thus optimized prism surface. Various optical functions are integrated to form an optical module for an optical amplifier by partially vapor-depositing various open optical films such as a coupler film and taking an optical path configuration for reflecting or refracting on the prism surface and inside the prism.

For an optical film having a limited light ray incident angle, the angle of incidence on the optical film is manipulated by determining the angle of the prism surface with respect to the light ray from Snell's law, so that all the optical ports are incident on the module. Set parallel or perpendicular to the optical path.

[0015]

According to the present invention, since various optical devices are constituted by the open optical film partially vapor-deposited on the surface of the prism, the device is not deteriorated by the high power of the excitation light and the signal light unlike the conventional device. A compact and highly reliable optical module for an optical amplifier can be provided.

Further, by optimizing the shape of the prism and the installation angle thereof, all optical ports can be mounted horizontally or vertically to each other even when an optical film having a limited incident angle is used. The manufacturability of the module is improved.

[0017]

Embodiments of the present invention will now be described in detail with reference to the drawings. Referring first 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 via 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 21 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 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 output of the photodiode 16 controls the drive circuits of the LDs 20a and 20b to be turned on / off 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.

The lens assembly 38 has a wavelength of 1.48 μm or 0.98 by the polarization-maintaining optical fiber 66.
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 68.

Reference numeral 46 denotes the excitation light for Er-doped optical fiber 10.
A polarization splitting film 48 for polarization-coupling P-polarized light and S-polarized light on its four surfaces.
A demultiplexing film 50 and non-reflective films 52 and 54 that reflect the excitation light having a wavelength of 1.48 μm or 0.98 μm and transmit the signal light having a wavelength of 1.55 μm are formed.

A coupler prism 56 reflects and branches a part of the signal light, and a coupler film 58 and non-reflection films 60 and 62 are formed on the surface thereof. A polarization-independent optical isolator 64 is inserted in the optical path of the signal light between the excitation prism 46 and the coupler prism 56, and this optical isolator is, for example, Japanese Patent Publication No. 61-588.
No. 09 taper rutile type optical isolator.

Therefore, the wavelength of 1.
The 48 μm S-polarized pumping light is a polarization-maintaining optical fiber 68.
Then, the light enters the excitation prism 46 through the lens assembly 40, is refracted by the non-reflection film 54, and then is reflected by the polarization separation film 48.

On the other hand, the wavelength of 1.4 emitted from the LD 20a is 1.4.
The 8 μm P-polarized pumping light enters the pumping prism 46 via the polarization-maintaining optical fiber 66 and the lens assembly 38, passes through the polarization separation film 48, and is refracted to be combined with S-polarized light.

The combined excitation light is reflected by the demultiplexing film 50, refracted by the non-reflective film 52, and emitted.
Is incident on the Er-doped optical fiber 10 via the, and Er ions are excited 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 anti-reflection film 5 of the excitation prism 46.
After being incident on and refracted at 2, the branching film 50 is refracted and emitted, passes through the optical isolator 64, enters the non-reflective film 60 of the coupler prism 56, is refracted, and then enters the coupler film 58.

A part of the signal light is reflected and branched by the coupler film 58, refracted and emitted from the non-reflective film 62, and received by the photodiode 42 attached to the housing 32 so as to be orthogonal to the lens assembly 34. ..

Most of the signal light passes through the coupler film 58, is refracted, becomes parallel to the optical axis of the lens assembly 34, enters the lens assembly 36, and is coupled to the single mode optical fiber 44 constituting the transmission path. ..

According to the present embodiment, the optical module for backward pumping the pumping light, which has been increased in power by polarization combining, into the Er-doped optical fiber 10 can be constructed with low loss and in a compact and highly stable manner. And higher performance can be realized.

Further, since the shapes and the angular arrangements of the excitation prism 46 and the coupler prism 56 are optimized, all the optical ports can be configured to be parallel or perpendicular to the optical axis of the lens assembly 34, and at the time of making a module. The handling property of is improved.

Next, referring to FIG. 4,
The shapes of the excitation prism 46 and the coupler prism 56 corresponding to
And how to set the angle. Figure 4 is optional
When the direction of the optical path with respect to the coordinate system U is opposite to the X axis of the coordinate system U
FIG. Angle θ with respect to coordinate system U₁Also
Ray B₁Is θ with respect to the coordinate system U _M3With an angle of
It is incident on the rhythm surface and is refracted to the coordinate system U by θ.₂of
Angled ray B₂Take the route of.

The ray B ₂ is incident on the prism surface having an angle of θ _M1 with respect to the coordinate system U, is refracted there, and takes the path of the ray B ₃ having an angle of θ ₃ . Similarly, the ray B ₃ is refracted by the prism surface having an angle of θ _M5 and θ _{4 with} respect to the coordinate system U.
Taking the path of rays B ₄ having an angle of, further beam B _{4
Refracts on} the prism surface having an angle of θ _M6 and takes the path of a ray B ₅ having an angle of θ ₅ with respect to the coordinate system U.

Ray B _{4 of} ray B ₄ reflected from the prism surface
₆ has an angle of θ ₆ with respect to the coordinate system U, and this ray B ₆ is refracted on the prism surface with an angle of θ _M7 with respect to the coordinate system U,
Take a path of a ray B ₇ having an angle θ ₇ with respect to the coordinate system U.

Further, the light ray B ₈ reflected from the prism surface from the light ray B ₂ is incident on the prism surface having an angle of θ _M2 with respect to the coordinate system U at an angle of θ ₈ and is refracted there to be coordinate system U. Follow the path of ray B ₉ having an angle of θ ₉ with respect to.

In this embodiment, θ_Five, Θ₇, Θ₉, Θ₁₁But
Θ₁Add 0 °, 90 °, 180 °, or 270 ° to
Θ to obtain the angle_M1,θ_M2,θ_M3,θ_M4,θ
_M5,θ _M6,θ_M7To set.

Next, the configuration of the optical module according to the second embodiment of the present invention will be described with reference to FIG. In the description of the present embodiment, the same reference numerals will be given to components that are substantially the same as those in the first embodiment shown in FIG.

The laser diode 20 is provided on the end wall 32a of the housing 32 via a lens assembly 34 connected to the Er-doped optical fiber 10 and a polarization-maintaining optical fiber 66.
A lens assembly 38 connected to a is attached. In addition, the other end wall 32 opposite to the end wall 32a
A lens assembly 36 connected to the transmission path optical fiber 44 is attached to b.

A lens assembly 40 connected to the laser diode 20b via a polarization-maintaining optical fiber 68 is provided on one side wall 32c orthogonal to the end walls 32a and 32b.
And the photodiode 42 is attached, and the optical axis of the lens assembly 40 and the optical axis of the photodiode 42 are orthogonal to the optical axis of the lens assembly 38.

Reference numeral 70 denotes a polarization synthesizing prism, and a polarization separation film 72 for polarization synthesizing P-polarized light having a wavelength of 1.48 μm or 0.98 μm and S-polarized light having a wavelength of 1.48 μm or 0.98 μm on the surface thereof. The non-reflective films 74 and 76 are vapor-deposited.

Reference numeral 80 denotes a demultiplexing prism, on the surface of which a signal light having a wavelength of 1.55 μm is transmitted and a wavelength of 1.48 μm.
Demultiplexing film 82 that reflects the excitation light of
Is vapor-deposited.

Reference numeral 90 denotes a coupler prism, on the surface of which a coupler film 92 for branching the signal light at a predetermined branching ratio,
Non-reflection films 94 and 96 are vapor-deposited. A polarization independent optical coupler 64 is inserted between the demultiplexing prism 80 and the coupler prism 90.

However, the S-polarized pumping light having a wavelength of 1.48 μm emitted from the laser diode 20b is incident on the polarization combining prism 70 via the polarization-maintaining optical fiber 68 and the lens assembly 40, and is transmitted through the non-reflection film 74. Then, the light is reflected by the polarization separation film 72.

On the other hand, the P-polarized pumping light having a wavelength of 1.48 μm emitted from the laser diode 20a enters the polarization combining prism 70 via the polarization-maintaining optical fiber 66 and the lens assembly 38, and passes through the polarization separation film 72. After that, it is refracted and combined with S-polarized light.

The combined excitation light is used for the polarization coupling prism 70.
Of the non-reflective film 76 and the non-reflective film 84 of the demultiplexing prism 80, enters the demultiplexing film 82, is reflected here, and refracts and exits the non-reflective film 86 of the demultiplexing prism 80. It is incident on the Er-doped optical fiber 10 via 34 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, is incident on the antireflection film 86 of the demultiplexing prism 80, is refracted, and is further divided. It passes through the wave film 82 and is refracted.

The signal light transmitted through the demultiplexing film 82 passes through the polarization-independent optical isolator 64, the non-reflection film 94 of the coupler prism 90, and enters the coupler film 92. A part of the signal light is reflected and branched by the photodiode 42 by the coupler film 92 of the coupler prism 90, and most of the signal light is transmitted through the coupler film 92 and refracted in the direction parallel to the optical axis of the lens assembly 34, and the lens assembly 36. Is coupled to the transmission line optical fiber 44 via.

Next, referring to FIG. 6, there is shown a block diagram of an optical amplifier to which an optical module of a third embodiment of the present invention described later is applied. 110 is an Er-doped optical fiber in which erbium (Er) is doped in the core,
A front optical circuit 112 is provided in front of the r-doped optical fiber 110.
Is provided, and a rear optical circuit 126 is provided at the rear.

The forward optical circuit 112 comprises an optical coupler 114, an optical isolator 116, a demultiplexer 118, a photodiode 120, and a polarization coupler 124. The photodiode 120 detects the signal light branched by the coupler 114 and monitors the signal light.

The rear optical circuit 126 comprises a demultiplexer 128, an optical isolator 130, an optical coupler 132, photodiodes 134 and 136, and a polarization coupler 140.

The photodiode 134 is an optical coupler 132.
The signal light branched by is detected, and feedback control is performed by an APC circuit (not shown) so that the amplified signal light power becomes constant.

In the photodiode 136, when the connector connected to the optical fiber on the output side is uncoupled, the signal light is reflected and returns, but a part of this is reflected by the optical coupler 132 and the photodiode 136. Laser diode for excitation 122a, 122b, 138a, 138b
This is for the purpose of safety by stopping the optical amplifier by lowering the drive current of.

However, the pumping laser diode 122a
P-polarized excitation light emitted from the laser diode 1
The S-polarized excitation light emitted from 22b is polarized by the polarization coupler 1
24, is reflected by the demultiplexer 118, and is input to the Er-doped optical fiber 110.
The Er ions inside are excited to a high energy level.

Similarly, a laser diode for excitation 138a
P-polarized excitation light emitted from the laser diode 1
The S-polarized excitation light emitted from 38 b is polarized by the polarization coupler 1
The light is synthesized in 40, reflected by the demultiplexer 128, input into the Er-doped optical fiber 110 from the rear, and excites Er ions to a high energy level.

In such a state, the optical coupler 11
4. When signal light having a wavelength of 1.55 μm, for example, is input through the optical isolator 116 and the demultiplexer 118, stimulated emission of light having the same wavelength as the signal light occurs, and the signal light gradually propagates along the Er-doped optical fiber 110. Is amplified.

The amplified signal light passes through the demultiplexer 128, the optical isolator 130 and the optical coupler 132 and is sent out to the optical fiber transmission line. The signal light branched by the optical coupler 132 is detected by the photodiode 134 and feedback-controlled by an APC circuit (not shown) so that the amplified signal light power becomes constant.

The drive circuit of the LDs 122a, 122b, 138a, 138b is on / off controlled by the output of the photodiode 120 according to the input of the signal light. Next, with reference to FIG. 7, an optical module of a third embodiment of the present invention applied to the optical amplifier shown in FIG. 6 will be described. Constituent parts substantially the same as those shown in the block diagram of FIG. 6 will be described with the same reference numerals.

On the end wall 142a of the housing 142, the light beam emitted from the optical fiber is converted into a collimated beam.
Individual lens assemblies 144, 146, 148, 152
Is attached. The lens assembly 144 is Er
The lens assembly 146 is connected to the input end of the doped optical fiber 110 and the lens assembly 146 is connected to the output end of the doped optical fiber 110.

Further, the lens assembly 148 has a wavelength of 1.48 μm or a wavelength of 0.
Laser diode 122a that emits P-polarized light of 98 μm
, And the lens assembly 152 also has a wavelength of 1.48 μm or 0.
Laser diode 138a that emits P-polarized light of 98 μm
It is connected to the. Each lens assembly 144,14
The optical axes of 6, 148 and 152 are arranged parallel to each other.

The end wall 142b facing the end wall 142a
Two lens assemblies 156 and 160 are attached to the lens assembly so that the optical axis thereof is parallel to the optical axis of the lens assembly 144. The lens assembly 156 is connected to the input side optical fiber 158, and the lens assembly 160
Is connected to the output side optical fiber 162.

The optical axis of one side wall 142c orthogonal to the end walls 142a and 142b is the lens assembly 14.
Two lens assemblies 164, 1 orthogonal to the optical axis of 4
68 and the photodiode 134 are attached.

The lens assembly 164 has a wavelength of 1.48 μm or 0.98 μ via a polarization-maintaining optical fiber 166.
The lens assembly 168 is connected to the laser diode 122b that outputs S-polarized light of m.
It is connected to a laser diode 138b that outputs S-polarized light of m. Two photodiodes 120 and 136 are attached to the other side wall 142d.

Reference numeral 170 denotes a polarization combining prism, on the surface of which a polarization splitting film 1 for transmitting P polarized light and reflecting S polarized light is formed.
72 and antireflection films 174 and 176 are vapor-deposited. 1
Reference numeral 80 is a demultiplexing prism, which has a wavelength of 1.5 on its surface.
Wavelength of 1.48 μm or 0.98 through 5 μm signal light
The demultiplexing film 182 that reflects the excitation light of μm and the non-reflection film 18
4,186 are vapor-deposited.

Reference numeral 190 denotes a coupler prism, on the surface of which a coupler film 192 for branching the signal light with a predetermined branching ratio.
Then, non-reflective films 194 and 196 are deposited. A polarization-independent optical isolator 198 is inserted in the optical path of the signal light on the input side between the demultiplexing prism 180 and the coupler prism 190, and a polarization-independent optical isolator is also installed on the optical path of the signal light on the output side. 200 is inserted. Further, a narrow band bandpass filter 202 that transmits only the signal light is inserted on the optical path of the signal light between the coupler prism 190 and the optical isolator 200.

However, the S-polarized excitation light having a wavelength of 1.48 μm or 0.98 μm emitted from the LD 122b is incident on the non-reflective film 174 of the polarization combining prism 170 via the polarization-maintaining optical fiber 166 and the lens assembly 164. After passing through the non-reflection film 174, it is reflected by the polarization separation film 172.

On the other hand, the wavelength of 1.
The P-polarized excitation light of 48 μm or 0.98 μm is incident on the polarization separation film 172 of the polarization beam combiner prism 170 via the polarization-maintaining optical fiber 150 and the lens assembly 148, passes through the polarization separation film 172, and then is refracted. LD122
Combined with S-polarized light from b.

The combined excitation light is transmitted through the antireflection film 176 and the antireflection film 184 of the demultiplexing prism 180, and then the demultiplexing film 18 is transmitted.
The laser beam is reflected at 2, and then is refracted after passing through the non-reflective film 186 and then introduced into the Er-doped optical fiber 110 through the lens assembly 144 from the front to excite Er ions to a high energy level.

Further, the wavelengths of 1.
The 48 μm or 0.98 μm S-polarized pumping light is incident on the non-reflective film 174 of the polarization combining prism 170 via the polarization-maintaining optical fiber 169 and the lens assembly 168, passes through this, and is reflected by the polarization separation film 172. To be done.

On the other hand, the P-polarized excitation light having a wavelength of 1.48 μm or 0.98 μm emitted from the LD 138a enters the polarization separation film 172 of the polarization combining prism 170 via the polarization-maintaining optical fiber 154 and the lens assembly 152. The light is transmitted there through, refracted, and then combined with the S-polarized light from the LD 138b.

The combined excitation light is transmitted through the antireflection film 176 and the antireflection film 184 of the demultiplexing prism 180, and then the demultiplexing film 1 is transmitted.
The light is reflected at 82, further transmitted through the non-reflective film 186, then refracted and introduced into the Er-doped optical fiber 110 from the rear via the lens assembly 146 to excite Er ions to a high energy level.

The signal light from the input side optical fiber 158 enters the optical module through the lens assembly 156, passes through the coupler prism 190, the optical isolator 198 and the demultiplexing prism 180, and passes through the lens assembly 144 to Er-doped light. It is input to the fiber 110.

Since the Er ions are excited to a high energy level, when signal light having a wavelength of 1.55 μm is input to the doped optical fiber 110, light having the same wavelength as the signal light is stimulated and emitted, and the signal light becomes It is gradually amplified along the doped optical fiber 110.

A part of the input signal light is reflected by the coupler film 192 of the coupler prism 190, and the photodiode 1
Detected at 20. The output of the photodiode 120 controls on / off of the drive circuits of the LDs 122a, 122b, 138a, 138b.

The signal light amplified by the Er-doped optical fiber 110 is fixed to the housing 142 by the lens assembly 14
6 is a collimated beam, is transmitted through the non-reflective film 186 and the demultiplexing film 182 formed on the surface of the demultiplexing prism 180, and is further transmitted by only the polarization independent optical isolator 200 and the signal light. The light passes through 202 and enters the coupler prism 190.

A part of the signal light is reflected and branched to the photodiode 134 by the coupler film 192 of the coupler prism 190, and feedback-controlled by an APC circuit (not shown) so that the signal light power after amplification becomes a constant value. Most of the signal light passes through the coupler film 192 and is coupled to the output side optical fiber 162 via the lens assembly 160.

When the optical connector connected to the tip of the output side optical fiber 162 is disengaged, the signal light is reflected and returns to the amplifier. This reflected feedback light is incident on the coupler prism 190 from the lens assembly 160. Then, a part thereof is reflected by the coupler film 192 and detected by the photodiode 136. When the reflected feedback light is detected by the photodiode 136, the pumping LDs 122a, 122b, 138a,
The drive current of 138b is dropped to stop the optical amplifier to ensure safety.

In the third embodiment described above, three prisms, that is, the polarization combining prism 170 and the demultiplexing prism 180 are used.
Although the coupler prism 190 is used, the polarization combining prism 170 and the demultiplexing prism 180 are integrated to form an excitation prism, and the two optical prisms of the excitation prism and the coupler prism 190 constitute a similar optical module. It is also possible to do so.

[0082]

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. Further, even when an optical film with a limited incident angle is used, the directions of the optical ports can be parallel or perpendicular to each other, which improves the handleability when manufacturing the optical module.

[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 the first embodiment of the present invention.

FIG. 4 is a diagram illustrating setting of a prism angle with respect to a light beam.

FIG. 5 is a sectional view of a second embodiment of the present invention.

FIG. 6 is a block diagram of another optical amplifier to which the present invention is applied.

FIG. 7 is a sectional view of a third embodiment of the present invention.

[Explanation of symbols]

 10,110 Er-doped optical fiber 42,142 Housing 46 Excitation prism 56,90,190 Coupler prism 70,170 Polarization combining prism 80,180 Demultiplexing prism 48,72,172 Polarization separation film 50,82,182 Demultiplexing Membrane 58,92,192 Coupler Membrane

Front page continuation (72) Inventor Tatsuya Murai 2-1 Kitaichijo Nishi, Chuo-ku, Sapporo-shi, Hokkaido Within Fujitsu Hokkaido Digital Technology Co., Ltd.

Claims (6)

[Claims] 1. An optical module for an optical amplifier, comprising an optical circuit behind a rare earth-doped optical fiber in a casing with respect to a signal light propagation direction, the one end wall (32a) of a casing (32). The first lens assembly (34) to which the rare earth-doped optical fiber (10) is connected and the second lens assembly (38) into which the excitation light from the first excitation light source (20a) is introduced are parallel to each other. The third lens assembly (36) is provided and the output optical fiber (44) is connected to the other end wall (32b) facing the one end wall (32a). 34, 38) and the fourth lens assembly (40) in which the pumping light from the second pumping light source (20b) is introduced to one side wall (32c) orthogonal to both end walls and the signal light. Light receiving element (4
2) is provided, and the multiplexing prism (46) on which the polarization separation film (48) and the demultiplexing film (50) are formed, and the coupler prism (5 on which the coupler film (58) is formed
6) is inserted into the optical path of the signal light propagating in the housing (32), and the pumping lights from the first and second pumping light sources (20a, 20b) are combined by the polarization separation film (48). Reflected by the branching film,
The shape of the multiplexing prism (46) and the arrangement angle with respect to the signal light optical path are set so that the signal light reflected by the coupler film (58) is incident on the first lens assembly (34). Four
An optical module for an optical amplifier, characterized in that the shape of the coupler prism (56) and the arrangement angle with respect to the signal light optical path are set so as to be incident on 2). 2. A signal light is allowed to pass from the first lens assembly (34) to the third lens assembly (36) only between the excitation prism (46) and the coupler prism (56). The optical module for an optical amplifier according to claim 1, further comprising a polarization-independent optical isolator (64). 3. An optical module for an optical amplifier, in which an optical circuit behind a rare-earth-doped optical fiber with respect to a signal light propagating direction is formed in a housing, the one end wall (32a) of the housing (32). The first lens assembly (34) to which the rare earth-doped optical fiber (10) is connected and the second lens assembly (38) into which the excitation light from the first excitation light source (20a) is introduced are parallel to each other. The third lens assembly (36) is provided and the output optical fiber (44) is connected to the other end wall (32b) facing the one end wall (32a). 34, 38) and the fourth lens assembly (40) in which the pumping light from the second pumping light source (20b) is introduced to one side wall (32c) orthogonal to both end walls and the signal light. Light receiving element (4
2) is provided, and a polarization beam combining prism (70) having a polarization splitting film (72) for polarization coupling the pumping light from the first and second pumping light sources (20a, 20b) and the signal light Splitting film that transmits and reflects excitation light (82)
The demultiplexing prism (80) formed with a coupler prism (90) formed with a coupler film (92) for reflecting a part of the signal light to enter the light receiving element (42) (32) ) Is inserted in the optical path of the signal light or the pumping light propagating in the inside, and the pumping lights from the first and second pumping light sources (20a, 20b) are combined by the polarization separation film (72), and the demultiplexing film is formed. The polarization combining prism (70) and the demultiplexing prism (80) are shaped so as to be reflected by (82) and incident on the first lens assembly (34) and the angular arrangement with respect to the signal light optical path and the excitation light optical path. The shape of the coupler prism (90) and the angle arrangement with respect to the optical path of the signal light are set so that a part of the signal light is reflected by the coupler film (92) and enters the light receiving element (42). A characteristic optical module for optical amplifiers. 4. The signal light is allowed to pass from the first lens assembly (34) only to the third lens assembly (36) between the demultiplexing prism (80) and the coupler prism (90). The optical module for an optical amplifier according to claim 2, further comprising a polarization-independent optical isolator (64). 5. An optical module for an optical amplifier, wherein an optical circuit in front of a rare earth-doped optical fiber and an optical circuit in the rear of the rare earth-doped optical fiber are arranged in a common housing with respect to a signal light propagating direction. The first excitation light and the first lens assembly (144) and the second lens assembly (146) to which the input end and the output end of the rare earth-doped optical fiber (110) are connected to the one end wall (142a), respectively. The third lens assembly (148) to be introduced and the fourth lens assembly (152) to which the third excitation light is introduced are provided, and the input light is input to the other end wall (142b) facing the one end wall. Fifth to which the fiber (158) is connected
The lens assembly (156) and the sixth lens assembly (160) to which the output optical fiber (162) is connected are provided, and the second excitation light is introduced into one side wall (142c) orthogonal to both end walls. The seventh lens assembly (164) and the eighth lens assembly (168) into which the fourth excitation light is introduced are provided, and one side of the signal light on the input side is provided on the other side wall (142d) facing the one side wall of the housing. The first light receiving element (120) for receiving the light is attached, and the second light receiving element (134) for receiving a part of the signal light on the output side is attached to the one side wall (142c) of the housing. In addition to inserting the polarization combining prism (170) with the polarization separation film (172) formed in the optical path of the excitation light inside
A demultiplexing prism (180) with a demultiplexing film (182) and a coupler prism with a coupler film (192) in the optical path of signal light
(190) is inserted, and the first and second excitation lights are combined by the polarization separation film (172) and then reflected by the demultiplexing film (182) to enter the first lens assembly (144). , The third and fourth excitation lights are combined by the polarization separation film (172) and then reflected by the demultiplexing film (182) to enter the second lens assembly (146). The shapes of the prism (170) and the demultiplexing prism (180) and the angular arrangement with respect to the excitation light optical path and the signal light optical path are set, and a part of the input signal light is reflected by the coupler film (192) to receive the first light reception. A part of the output signal light incident on the element (120) is reflected by the coupler film (192) and the second light receiving element (134)
The optical module for an optical amplifier, characterized in that the shape of the coupler prism (190) and the angular arrangement with respect to the optical path of the signal light are set so as to enter the optical module. 6. The fifth lens assembly (15) between the coupler prism (190) and the demultiplexing prism (180).
8) A first polarization-independent optical isolator for allowing signal light to pass only in the direction of the first lens assembly (144)
(198) and a second polarization-independent optical isolator (200) that allows the passage of signal light only from the second lens assembly (146) to the sixth lens assembly (160). The optical module for an optical amplifier according to claim 5.