JPH0798423A - Optical multiplexer - Google Patents

Abstract

PURPOSE:To realize the small-sized optical multiplexer which is simple in constitution. CONSTITUTION:This optical multiplexer 61 has first to fourth input and output terminals 521 to 524. A light signal 12 emitted from the first input/output terminal 521 is partly reflected by a branch film 63 formed on one surface of a glass plate 62 and is introduced to the second input/output terminal 522. The remaining light signal transmits the glass plate 62, transmits a wavelength synthesizing film 64 formed on the other surface as well and is introduced to the third input/output terminal 523. Exciting light 14 emitted from the fourth output terminal 24 is reflected by this wavelength synthesizing film 64 and is introduced to the third input/output terminal 523. Since the glass plate 62 is one sheet as compared with heretofore, the constitution is simplified. Particularly, the thickness (t) of a substrate is so set that the misalignment quantity of the optical axis by refraction at the time of incidence on the substrate is larger than a beam diameter. Leaking light is further decreased by adding an aperture to the substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical multiplexer for splitting incident first light and multiplexing one of the split light with a second light.

[0002]

2. Description of the Related Art In an optical communication system for long-distance optical communication, it is necessary to amplify an optical signal weakened in a transmission cable. Conventionally, when an optical signal is amplified, it is converted into an electric signal, electrically amplified, and then converted into an optical signal again. In recent years, an optical fiber amplifier that directly amplifies an optical signal has also been proposed.

FIG. 10 shows the configuration of a conventionally proposed optical fiber amplifier. Optical fiber amplifier 11
Is a first optical branching device 1 for branching an input optical signal 12
3, a multiplexer 15 for multiplexing the pumping light 14, and an optical isolator 16 are connected in series to the input side of the rare earth ion-doped fiber 17, and an optical isolator 18 and a second optical splitter 19 are provided on the output side. Are connected in series. First
The optical signal 21 branched by the optical branching device 13 is detected by the first monitor photodiode 22 for monitoring, and the signal 23 branched by the second optical branching device 19,
One of 24 is detected by the second monitor photodiode 25 for monitoring. The other optical signal 24 becomes the output of this optical fiber amplifier 11. A pumping light source 26 is connected to the multiplexer 15 in the optical fiber amplifier 11 and the pumping light 14 output from the pumping light source 26 is connected to the multiplexer 15.
Is injected into the rare earth ion-doped fiber 17, and the optical signal 27 passing through the first optical branching device 13 is directly amplified.

FIG. 7 specifically shows the configuration of a first optical branching device as an example of the optical branching device used in this conventional optical fiber amplifier. The configuration of the second optical branching device 19 is substantially the same as that of the first optical branching device 13.

The first optical branching device 13 has a first input / output terminal 311 and a second input / output terminal 312 arranged in a direction orthogonal to the traveling direction of the optical signal 32 entering the first input / output terminal 311. It is provided with three input / output terminals 311 to 313 of a third input / output terminal 313 arranged in the traveling direction of the optical signal 32 incident from the input / output terminal 311. First optical branching device 13
Inside the optical signal 32, a glass plate 33 is arranged so as to be inclined at a predetermined angle with respect to the traveling direction of the optical signal 32.
A branching film 34 is formed on the surface on the incident side of, and an antireflection film 35 is formed on the opposite surface.

In the first optical branching device 13, for example, when an optical signal 32 of wavelength λ1 is incident from the first input / output terminal 311, a part of the optical signal 32 is branched by the branching film 34, and the second optical branching device
Is output from the input / output terminal 312 of the. The remaining optical signal passes through the glass plate 33 and is emitted from the third input / output terminal 313.

FIG. 8 specifically shows the configuration of a conventional multiplexer used in the optical fiber amplifier shown in FIG. The multiplexer 15 has a first input / output terminal 411,
Three input / output terminals 411, a second input / output terminal 412 arranged in the traveling direction of the optical signal 27 to be incident and a third input / output terminal 413 arranged in a direction orthogonal to the traveling direction of the optical signal 27. .About.413. This multiplexer 1
A glass plate 43 is arranged inside the optical fiber 5 so as to be inclined at a predetermined angle with respect to the traveling direction of the optical signal 27.
An antireflection film 44 is formed on the incident side surface of No. 7, and a wavelength synthesizing film 45 is formed on the opposite surface.

In this multiplexer 15, the first input / output terminal 41
It is assumed that the optical signal 27 of wavelength λ1 is incident from 1 and the excitation light 14 of wavelength λ2 is incident from the third input / output terminal 413. The optical signal 27 is transmitted through the antireflection film 44, the glass plate 43, and the wavelength synthesis film 45 in this order, and the second input / output terminal 41.
Guided to 2. The other excitation light 14 is reflected by the wavelength synthesizing film 45 and is similarly guided to the second input / output terminal 412.

As described above, in the conventional optical fiber amplifier,
The first optical branching device 13 and the optical multiplexer 15 are separately arranged as physically different parts on the input side of the rare earth ion-doped fiber 17. Therefore, not only the number of parts is increased, but also the first optical branching device 13 and the multiplexer 15 need to be relatively aligned. Therefore, an optical multiplexer in which both are combined and integrated is proposed.

FIG. 9 specifically shows the configuration of the proposed optical demultiplexer. This optical multiplexer 51 has a first input / output terminal 521, a second input / output terminal 522 arranged in one direction orthogonal to the traveling direction of the optical signal 12 of wavelength λ1 incident from here, and the optical signal 12 The third input / output terminal 523 and the second input / output terminal 522 which are arranged in the traveling direction of
Scene 4 of the 4th input / output terminal arranged at the position facing
It has two input / output terminals 521 to 524.

In the optical path connecting the first optical input / output terminal 521 and the third optical input / output terminal 523 in the optical multiplexer 51,
The first glass plate 53 and the fourth glass plate 54 have the same inclination angle and are arranged at a predetermined interval. First
A branch film 55 is formed on the incident side surface of the glass plate 53, and an antireflection film 56 is formed on the other surface. An antireflection film 57 is formed on the incident side surface of the second glass plate 54.
Further, a wavelength synthesis film 58 is formed on each of the other surfaces.

In such an optical multiplexer 51, the optical signal 21 reflected by the optical branching film 55 of the first glass plate 53 is used.
Is output as monitor light from the second input / output terminal 522, and the first monitor photodiode 2 shown in FIG.
2 will be incident. Further, the optical signal transmitted through each of the branch film 55, the first glass plate 53 and the antireflection film 56 is transmitted through each of the other antireflection film 57, the second glass plate 54 and the wavelength synthesizing film 58. The pumping light 14 having the wavelength λ2 that has entered from the fourth input / output terminal 524 is reflected by the wavelength combining film 58, so that the lights having both wavelengths λ1 and λ2 are combined and guided to the third input / output terminal 523. It will be.

[0013]

In the optical multiplexer 51 shown in FIG. 9, since the branching film 55 and the wavelength synthesizing film 58 are formed on different glass plates 53 and 54, they are the same. It cannot be shared as a part. Therefore, there is a problem that the number of parts is still large, and the size of the optical multiplexer 51 becomes larger than that of the conventional branching device or multiplexer. There is also a problem that the structure of the optical multiplexer 51 is complicated.

Japanese Patent Laid-Open No. 3-225304 discloses an optical multiplexer / demultiplexer having another structure, which is an optical element for separating light having a mixture of two wavelengths λ1 and λ2. , Is different from an optical multiplexer that performs both branching and multiplexing, and is not directly related to the present invention.

Therefore, an object of the present invention is to provide an optical multiplexer which has a simple structure and can be reduced in size.

[0016]

The optical optical multiplexer according to the present invention comprises:
A first optical input / output terminal for inputting / outputting light of wavelength λ1 and an optical branching film for transmitting a part of light of wavelength λ1 output from the first optical input / output terminal and reflecting the rest are provided on one side. The wavelength λ is formed on the surface opposite to the surface on which the optical branching film is formed.
There is used a substrate that transmits light of No. 1 and transmits light having an optical multiplexing film that reflects light of wavelength λ2. Then, the light is transmitted through the second optical input / output terminal to which the light of the wavelength λ1 output from the first optical input / output terminal and reflected by the optical branching film is input, the optical branching film, the substrate, and the optical multiplexing / demultiplexing film. Wavelength λ1
Third light input / output terminal to which the light of (4) is input, and fourth light that is reflected by the optical multiplexing film and outputs light of wavelength λ2 arranged at a position where light is input to the third light input / output terminal. It is characterized by having input / output terminals.

A light branching film for partially reflecting the light of the first wavelength emitted from the first light input / output terminal and guiding it to the second light input / output terminal is formed on one surface of the substrate. There is. The light transmitted through the light branching film is transmitted and guided to the third light input / output terminal, and the light of the second wavelength emitted from the fourth light input / output terminal is reflected to generate the third light input / output terminal. Is formed on the other surface of the substrate. Here, the substrate can be composed of, for example, one transparent glass plate.

That is, in the present invention, the light branching film is formed on one surface of the substrate, and the light multiplexing film is formed on the other surface. The light of the first wavelength is incident on the light branching film, a part of the light is branched, and the remaining light is transmitted through the light branching film and the light multiplexing film. On the other hand, the light of the second wavelength is incident on the optical multiplexing film, and is combined and emitted with the light of the first wavelength that has passed through the optical multiplexing film.

The present invention also includes a first optical input / output terminal and a second optical input / output terminal.
The light input / output terminal, the third light input / output terminal, and the fourth light input / output terminal are provided with means for collecting input / output light. Here, the refractive index of the substrate is n, the beam diameter of the light of wavelength λ2 output from the fourth light input / output terminal is w, and the incident angle from the fourth light input / output terminal to the light transmitting substrate is θ. When the thickness t of the substrate is

[0020]

[Equation 3]

It is characterized by satisfying.

According to the present invention, an optical branching film is formed on one surface of a substrate that transmits light, and an optical multiplexing film is formed on the other surface, so that the functions of the optical branching device and the optical multiplexing device are combined and integrated. By doing so, miniaturization has been achieved. Further, the signal light output from the first optical input / output terminal is split on the monitor side and is combined with the pumping light only by passing through one substrate. Therefore, the effect that the optical loss of the signal light is smaller than that of the conventional configuration can be obtained.

Here, as described above, when the optical branching film and the optical multiplexing film are formed on both surfaces of one substrate, the pumping light of wavelength λ2 output from the light input / output terminal on the pumping light source side is In some cases, the light is not reflected by the light-multiplexing film and a part of the light is transmitted. Then, since the leaked light is input to the optical input / output terminals on the monitor side, which are arranged at positions facing each other with the substrate sandwiched, part of the high intensity pumping light is mixed with the weak signal light that should be originally received. Therefore, the noise of the monitor light becomes large, and it may not be possible to perform sufficient monitoring. Therefore, the present invention is characterized in that the thickness of the substrate is equal to or more than the thickness defined by the above equation so that such a problem does not occur even when the optical branching device and the optical multiplexer are combined and integrated. There is.
That is, by making the substrate thick, even if a part of the excitation light is transmitted through the optical demultiplexing film, the light transmitted through the substrate is deviated from the optical axis to the optical input / output terminal on the monitor side.

Further, the present invention is characterized in that a film for blocking excitation light is formed on a part of the surface on which the light branching film is formed. By blocking the excitation light with the blocking film, leakage to the monitor side can be further reduced.

[0025]

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

FIG. 1 shows the structure of an optical multiplexer according to an embodiment of the present invention. The optical multiplexer of the present invention shown in FIG.
It is applied to an optical amplifier for an optical communication system in the 1.55 μm band. It has a function of branching a part of the input signal light of wavelength 1.55 μm to the monitor PD and multiplexing the remaining signal light with the excitation light of wavelength 1.48 μm. In FIG. 1, the same parts as those in FIG. 9 are designated by the same reference numerals, and the description thereof will be appropriately omitted.

This optical multiplexer 61 has a first input / output terminal 5
The substrate 62 is arranged so as to be inclined with respect to the straight line connecting 21 and the third input / output terminal 523. A branch film 63 is vapor-deposited on the surface of the substrate 62 on which the first light (optical signal 12) having the wavelength λ1 is incident. In addition, the second light of the wavelength λ2 (excitation light 1
An optical multiplexing film 64 is vapor-deposited on the surface that reflects 4).

The light branching film 63 is made of Ti deposited on the substrate 1.
It is composed of a multilayer film of O2 and SiO2, and has a characteristic of transmitting about 90% of incident light and reflecting the remaining 10%. On the other hand, the optical multiplexing film 64 has a wavelength of 1.55μ.
m has a characteristic of transmitting signal light of m and reflecting excitation light of wavelength 1.48 μm, and is composed of a multilayer film similar to the light branching film 2. The same BK7 glass as the conventional one is used for the substrate 1.

A part of the optical signal 12 incident on the branch film 63 is reflected and guided toward the second input / output terminal 522.
The remaining optical signal 12 is transmitted through the branch film 63, the glass plate 62 and the optical multiplexing film 64, and is guided to the third input / output terminal 523. Further, the excitation light 14 incident from the second input / output terminal 524 is reflected by the optical multiplexing film 64, and the excitation light 14 is also emitted from the third input / output terminal 524.
Of the input / output terminal 523.

If the optical multiplexer 61 of this embodiment is used for an optical fiber amplifier as shown in FIG. 10 as an example, it is incident on the first monitor photodiode 22 from the second input / output terminal 522. Monitor light is obtained. From the third input / output terminal 523, the combined light of the wavelength λ1 and the wavelength λ2 that is incident on the rare earth ion-doped fiber 17 via the optical isolator 16 is emitted.

In this embodiment, the branch film 63 has a wavelength of 1.55 μm.
It has a function of branching the optical signal 12 of m (wavelength λ1) into 9: 1, the optical multiplexing film 64 transmits the optical signal 12 of wavelength 1.55 μm, and pumps the wavelength of 1.48 μm (wavelength λ2). It has a function of reflecting the light 14. Therefore, 10% of the optical signal having a wavelength of 1.55 μm emitted from the first input / output terminal 522 is reflected by the branching film 63 to be guided to the second input / output terminal 522, and 90% of which is transmitted to the second input / output terminal 522. 3 to the input / output terminal 523. In addition, the fourth input / output terminal 524
The excitation light 14 having a wavelength of 1.48 μm emitted from is reflected by the optical multiplexing film 64 and guided to the third input / output terminal 523.

Each of the first to fourth optical input / output terminals 521
˜524 are equipped with an aspherical lens (not shown) that collimates the light emitted from the optical fiber at the tip of the optical fiber terminal where the end face of the optical fiber is terminated. About 10% of the signal light 12 output from the first light input / output terminal 521 is reflected by the branch film 63. The reflected light is input to the second optical input / output terminal 522 and then input to the monitor PD outside the optical multiplexer 61. The remaining signal light that has passed through the branching film 63 passes through the substrate 62 and the optical multiplexing film 64, is input to the third optical input / output terminal 523, and is transmitted to the external optical amplification fiber.

On the other hand, the wavelength 1.
The 48 μm excitation light 14 is output from the fourth light input / output terminal 524, reflected by the multiplexing film 64, and input 523 to the third light input / output terminal. The signal light 12 output from the first optical input / output terminal 521 is multiplexed and transmitted to the optical fiber for optical amplification.

As described above, according to the present invention, a single glass plate or the like is used in contrast to the conventional case where one glass plate is required for splitting and combining light. Since this is enough, the volume of the optical multiplexer is about half that of the conventional one. Further, as compared with the case where two substrates are used, it is not necessary to position the substrates to each other, so that the number of optical axis adjustment and fixing points is reduced, and the productivity can be improved. Furthermore, since the branching device is formed on one surface of the substrate and the optical multiplexing film is formed on the other surface of the substrate, the number of parts can be significantly reduced, and the cost required for manufacturing and storing individual parts can be reduced.

Next, the structure for improving the characteristics of the optical multiplexer of the present invention will be described in detail. The isolation (stopband attenuation amount) in the reflection stopband of the optical multiplexing film 64 formed of the multilayer film is usually only about 25 dB. That is, in the above-described embodiment, 99% or more of the pumping light 5 having a wavelength of 1.48 μm output from the fourth light input / output terminal 524 is reflected by the optical multiplexing film 64. However, a small amount of light of 0.2 to 0.3% is transmitted through the optical multiplexing film 64, and is input to the second optical input / output terminal 522 which is arranged at a position opposed to the substrate 62. . The optical signal is branched from the signal light 12 and is originally the second optical input / output terminal 52.
The monitor light to be input to 2 is weak light attenuated by being transmitted. On the other hand, the excitation light 14 leaking from the fourth light input / output terminal 524 side has a very high intensity. Therefore, if even a small proportion of light is input to the second light input / output terminal 522, it becomes impossible to accurately monitor the signal light 12.

In the optical multiplexer 61 of the present invention, the thickness of the substrate 62 is made thicker than a certain amount in order to avoid the above problems. The optical path of the light transmitted through the optical multiplexing film 63 shifts the optical path taken because the signal light is input to the second optical input / output terminal 522. Here, the shifted pumping light 1 with respect to the optical path of the signal light 12 input to the second optical input / output terminal 522.
The separation distance d of the optical path of No. 4 is expressed by the equation (1).

[0037]

[Equation 4]

Here, t is the thickness of the substrate 1, θ is the angle of incidence of the signal light or excitation light on the substrate, and n is the refractive index of the substrate 1. Assuming that the beam diameters of the signal light 12 and the excitation light 14 are 0.5 mm, the incident angle to the substrate 62 is 45 degrees, the refractive index of the substrate 64 is 1.5, and the plate thickness of the substrate 64 is 3.0 mm, separation occurs. The distance d is 2.26 mm, and the optical path of the excitation light 14 can be sufficiently separated from the optical path of the signal light 12.

FIG. 2 shows the separation distance with respect to the optical axis to the second optical input / output terminal 522 and the first output light from the fourth optical input / output terminal 523 when the beam diameter is 0.5 mm. 3 shows the relationship with the isolation of light emitted from the light input / output terminal. When the separation distance is set to about 2 mm, the isolation becomes about 70 dB, so that the leakage light from the fourth light input / output terminal can be sufficiently reduced.

An optical multiplexer of the present invention is actually manufactured with such a configuration, and the pumping light 14 is supplied from the fourth optical input / output terminal 524.
Is output. At this time, no excitation light was detected from the second light input / output terminal 522 within the range of measurement sensitivity, and it was confirmed that the isolation was 80 dB or more. For example, the intensity of the signal light 12 output from the first optical input / output terminal 521 is −20 dBm, and the intensity of the pumping light 14 output from the fourth optical input / output terminal 14 is +15 dBm. Then, the intensity of the signal light 12 input to the second optical input / output terminal 522 is −30 dBm, whereas the intensity of the pump light is −65 dBm or less. Therefore,
The pumping light component does not affect the monitoring of the signal light 12.

In general, if the optical path is separated from the beam diameter, sufficient isolation can be secured. Therefore, if the thickness t of the substrate 1 is set to a value satisfying the expression (2) from the expression (1), it is possible to sufficiently prevent the excitation light from being input to the optical input / output terminal on the monitor side.

[0042]

[Equation 5]

In this way, the light branching film and the light multiplexing film are formed on both surfaces of the same substrate, and the light is branched by transmission and reflection on the side where the light branching film is formed. By adopting a configuration in which light of two different wavelengths is multiplexed on the side where the optical multiplexing film is formed, the optical branching device and the optical multiplexing device can be combined and integrated. The volume can be reduced to less than half that of the conventional one. Moreover, the signal light emitted from the optical fiber of the first optical input / output terminal is collimated by the aspherical lens,
It transmits the light branching film and the light combining film at once. As a result, the number of times the light is collimated or condensed is reduced and the number of times the light is transmitted through the substrate is reduced as compared with the conventional configuration, so that the passage loss is reduced. Further, the antireflection film is not required on the end surface of the substrate. Further, the number of optical input / output terminals is reduced from 6 terminals to 4 terminals as compared with the conventional one, so that the number of parts is reduced and the manufacturing process is simplified.

Furthermore, by making the thickness of the substrate a certain value or more and shifting the optical path of the leakage light of the excitation light from the optical path of the signal light to the monitor side, the excitation light leaks to the monitor side even if they are integrated. It can be omitted and the signal light can be monitored without being affected by the pump light.

In the above-described embodiment of the present invention, the light branching film is formed of a multilayer film, but the invention is not limited to this.
Other means such as a grating may be used. Further, although the incident angle to the light branching film and the light combining film is 45 degrees, it goes without saying that the angle can be freely selected.

Next, another embodiment in which the characteristics of the embodiment of the present invention shown in FIG. 1 are further improved will be described. FIG. 3 shows a perspective view of a substrate used in the improved embodiment. Like the substrate 62 shown in FIG. 1, the substrate 72 shown in FIG. 3 has a light branching film 63 formed on the surface that receives the light emitted from the first light input / output terminal 521. In addition to the light branching film 63, the substrate 72 further includes an aperture 75 made of a metal film having a hole only near the center.
Is equipped with.

The diameter of the hole provided in the aperture 75 is about 800 μm, which is slightly larger than the beam diameter of the light 12 emitted from the first light input / output terminal 521. First
The light 12 emitted from the light input / output terminal 521 passes through this hole and is partially transmitted by the light branching film 63. The remaining light is reflected to the second light input / output terminal 522 side. Also,
As the metal film, chromium and gold are directly deposited on the upper surface of the light branching film 63. The hole forming the aperture 75 is formed by lifting off after vapor deposition. Since the aperture 75 has a high reflectance, even if a part of the emitted light 12 from the first optical input / output terminal hits the metal film, it is reflected to the second optical input / output terminal 522 side, so that there is no light loss. Don't

On the other hand, as shown in FIG. 4, of the excitation light 14 incident from the fourth light input / output 524 side, the leaked light λ2 ′ that has passed through the optical multiplexing film 64 is at the position where the hole is provided. And reach the off position. Therefore, this leaked light λ
2'is reflected by the aperture 75. Therefore, it is possible to prevent the excitation light 14 from leaking and entering the second light input / output terminal 522.

Apart from adding an aperture having a hole on the upper surface of the light branching film 63, only the side where the second light input / output terminal 522 is arranged with respect to the center of the substrate as shown in FIG. The same effect can be obtained by using an aperture having a metal film formed therein. Further, the aperture 75 is not limited to the metal film, and may be anything as long as it blocks light.

Further, as shown in FIG. 6, the monitor photodiode 80 may be arranged directly at the monitor side optical input / output terminal without an optical fiber. In this case, leak light can be reduced by adding an aperture 81 having a hole having a size substantially equal to the beam diameter to the front surface of the photodiode. Furthermore, as shown in the figure,
The isolator 82 may be built in the optical multiplexer 61. Similarly, it is also possible to directly arrange the pumping light source at the optical input / output terminal on the pumping light source side without using an optical fiber.

As described above, according to the optical multiplexer of the present invention, the optical branching device and the optical multiplexer can be combined into a single unit, whereby the size can be greatly reduced and the insertion loss can be reduced. Have an effect. Furthermore, the number of parts is reduced, and the manufacturing process is simplified, which also contributes to the cost reduction.

[0052]

As described above, according to the present invention, one glass plate is conventionally required for splitting and combining light, whereas one glass plate is used. Since it is sufficient to use the optical multiplexer, the volume of the optical multiplexer becomes about one half that of the conventional one, which greatly contributes to miniaturization. Further, as compared with the case where two substrates are used, it is not necessary to position the substrates to each other, and the number of adjustment or fixing points is reduced, and the productivity can be improved. Further, since the branching device is formed on one surface of the substrate and the wavelength synthesizing film is formed on the other surface, the number of parts is significantly reduced, and the cost required for manufacturing and storing individual parts can be reduced.

[Brief description of drawings]

FIG. 1 is a principle diagram showing a configuration of an optical multiplexer according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the separation distance and the isolation in the optical multiplexer according to the embodiment of the present invention.

FIG. 3 is a perspective view of a substrate used in another embodiment of the present invention.

FIG. 4 is a top view showing a configuration of an optical multiplexer according to another embodiment of the present invention.

FIG. 5 is a perspective view showing another configuration of a substrate used in another embodiment of the present invention.

FIG. 6 is a top view showing an embodiment in which a light receiving element and an isolator are integrated in the optical multiplexer of the present invention.

FIG. 7 is a schematic configuration diagram of an optical fiber amplifier which has conventionally been configured to perform branching and multiplexing of light using a branching device and a multiplexing device.

8 is a principle diagram showing an example of a configuration of the conventional branching device shown in FIG.

9 is a principle diagram showing an example of a configuration of the conventional multiplexer shown in FIG.

FIG. 10 is a principle diagram showing the principle of a conventionally proposed optical multiplexer.

[Explanation of symbols]

 11 Optical Fiber Amplifier 12 Optical Signal 13 Optical Brancher 14 Excitation Light 15 Optical Multiplexer 16 Isolator 17 Erbium Doped Fiber 18 Isolator 19 Optical Brancher 21 Monitor Light 22 Monitor Photodiode 23 Monitor Light 24 Amplified Light 25 Monitor Photodiode 26 Pumping semiconductor laser 27 Optical signal 51 Optical fiber amplifier 521 to 524 First to fourth input / output terminals 62 Substrate 63 Optical branching film 64 Optical multiplexing film 72 Substrate 75 Aperture 80 Light receiving element 81 Aperture 82 Isolator λ1 Optical signal wavelength λ2 Excitation light wavelength

Claims (16)

[Claims] 1. A branch film for partially reflecting the light of the first wavelength emitted from the first terminal and guiding it to the second terminal is formed on one surface of the substrate and transmitted through this branch film. A wavelength synthesizing film that transmits light and guides it to the third terminal and reflects light of the second wavelength emitted from the fourth terminal and guides it to the third terminal is formed on the other surface of the substrate. An optical multiplexer characterized in that. 2. The optical multiplexer according to claim 1, wherein the substrate is a single transparent glass plate and has a sufficient thickness as compared with a beam system that transmits the glass plate. 3. A first optical input / output terminal for inputting / outputting light of wavelength λ1, and a portion of the light of wavelength λ1 output from the first optical input / output terminal, and the remaining light A light having a light-branching film formed on one side and a light-multiplexing film formed on one surface to transmit the light of wavelength λ1 and reflect the light of wavelength λ2 on the surface opposite to the surface on which the light-branching film is formed. A substrate for transmitting light, a second light input / output terminal to which the light of wavelength λ1 output from the first light input / output terminal and reflected by the light branching film is input, the light branching film and the substrate And a third optical input / output terminal to which the light of wavelength λ1 transmitted through the optical multiplexing film is input, and a position where the light is input to the third optical input / output terminal after being reflected by the optical multiplexing film. An optical multiplexer comprising a arranged fourth optical input / output terminal for outputting light of wavelength λ2. 4. The first light input / output terminal, the second light input / output terminal, the third light input / output terminal, and the fourth light input / output terminal.
The light input / output terminal is provided with a condenser lens for converting the emitted light into parallel light at the emission end.
3) Optical multiplexer. 5. When the refractive index of the substrate is n, the beam diameter of the output light from the fourth optical input / output terminal is w, and the incident angle from the fourth optical input / output terminal to the substrate is θ, The thickness t of the light transmitting substrate is The optical multiplexer according to claim 4, characterized in that: 6. A first optical input / output terminal for inputting / outputting light of wavelength λ1 and a part of the light of wavelength λ1 output from the first optical input / output terminal is transmitted, and the remaining light is transmitted. A light having a light-branching film formed on one side and a light-multiplexing film formed on one surface to transmit the light of wavelength λ1 and reflect the light of wavelength λ2 on the surface opposite to the surface on which the light-branching film is formed. A substrate that transmits light, a light receiving element that receives the light of wavelength λ1 output from the first light input / output terminal and reflected by the light branching film, and converts the light of wavelength λ1 into an electrical signal; A third light input / output terminal to which the light of wavelength λ1 that has passed through the light branching film, the substrate, and the light combining film is input, and is reflected by the light combining film to emit light to the third light input / output terminal. A fourth optical input / output terminal for outputting light of wavelength λ2 arranged at a position where That optical multiplexer. 7. The first light input / output terminal, the third light input / output terminal, and the fourth light input / output terminal each have a condenser lens for converting output light into parallel light at an output end. 7. The optical multiplexer according to claim 6, wherein the light receiving element has a condenser lens on the front surface of the light receiving surface. 8. When the refractive index of the substrate is n, the beam diameter of the output light from the fourth optical input / output terminal is w, and the incident angle from the fourth optical input / output terminal to the substrate is θ, The thickness t of the light transmitting substrate is The optical multiplexer according to claim 7, characterized in that: 9. The optical device according to claim 4, wherein the substrate has a film for blocking or reflecting light formed on a part of the surface on the side where the light branching film is formed. Wave instrument. 10. The optical device according to claim 7, wherein the substrate has a film for blocking or reflecting light formed on a part of the surface on the side where the light branching film is formed. Wave instrument. 11. The film has a hole having an inner diameter substantially equal to the beam diameter of the light emitted from the first light input / output terminal, at a position irradiated with the light emitted from the first light input / output terminal. The optical multiplexer according to claim 9, characterized by having. 12. The film has a hole having an inner diameter substantially equal to the beam diameter of light emitted from the first light input / output terminal, at a position irradiated with light emitted from the first light input / output terminal. The optical multiplexer according to claim 10, characterized in that it has. 13. The film is formed in a substantially half region on the side of the second light input / output terminal, centered on a position irradiated with light emitted from the first light input / output terminal. The optical multiplexer according to claim 9, characterized in that 14. The film is formed in a substantially half region on the side of the second light input / output terminal centering on a position irradiated with light emitted from the first light input / output terminal. An optical multiplexer according to claim 10, characterized in that 15. The optical multiplexer according to claim 3, wherein an isolator is arranged between the substrate and the third optical input / output terminal. 16. The optical multiplexer according to claim 6, wherein an isolator is arranged between the substrate and the third optical input / output terminal.