JP2994261B2 - Optical circuit module - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical circuit module which is a component of an optical fiber communication system and the like.
In particular, the present invention relates to an optical circuit module which intervenes between three optical fibers and multiplexes or demultiplexes light of a plurality of systems having different wavelengths.

[0002]

[Prior art]

* Backward pumping type optical fiber amplifier As is well known, an optical fiber amplifier having a configuration shown in FIG. 1 is used in a certain type of optical fiber communication system. As shown in FIG. 1, a signal light having a wavelength of 1.55 μm introduced into the input port Pin propagates through the optical isolator 1 to the erbium-doped optical fiber 2. The signal light passes through the optical multiplexing / demultiplexing circuit 3 from the erbium-doped optical fiber 2, propagates to the optical fiber 4, passes through the optical isolator 5, and reaches the output port Pout.

On the other hand, an excitation light source 6 composed of a semiconductor laser generates excitation light having a wavelength of 1.48 μm. The pumping light propagates through the optical fiber 7 and is introduced into the optical multiplexing / demultiplexing circuit 3, from which it propagates through the erbium-doped optical fiber 2 in a direction opposite to the signal light. The signal light (wavelength 1.55 μm) propagating through the erbium-doped optical fiber 2 is amplified by the pump light (wavelength 1.48 μm) traveling in the opposite direction.

Since the traveling direction of the pump light and the traveling direction of the signal light are opposite to each other, this type is called a backward pumping type optical fiber amplifier. A forward-pumped optical fiber amplifier in which the traveling directions of the pump light and the signal light are the same, and a bidirectional pump-type optical fiber amplifier in which the backward and forward pumping types are combined are well known. Have been.

Structure of the conventional optical multiplexing / demultiplexing circuit 3 In the backward pumping type optical fiber amplifier shown in FIG. 1, the optical multiplexing / demultiplexing circuit 3 is configured as shown in FIG. The optical multiplexing / demultiplexing circuit module includes a ferrule 8 including the core 2a of the optical fiber 2, a ferrule 9 including the core 4a of the optical fiber 4, and a ferrule 10 including the core 7a of the optical fiber 7. ,
Collimating lenses 11, 12, and 13 disposed on the optical axes of the ferrules 8, 9, and 10, respectively, and an optical multiplexing / demultiplexing filter (also referred to as “WDM”) interposed between the optical axes of these three lenses. 14) and the optical filter 1 arranged on the optical axis of the collimator lens 13 in the excitation light path.
5 is provided.

Here, the optical multiplexing / demultiplexing filter 14 is formed by forming a dielectric multilayer film on a glass plate, and this is combined with three ferrules 8, 9, 10 and a collimating lens 11,
The following optical path is formed by the optical positional relationship between the optical fibers 12 and 13. The signal light having a wavelength of 1.55 μm emitted from the optical fiber core 2a of the amplification system and passed through the lens 11 is transmitted through the optical multiplexing / demultiplexing filter 14, collected by the lens 12, and introduced into the optical fiber core 4a of the output system. You. Excitation light having a wavelength of 1.48 μm emitted from the optical fiber core wire 7a and having passed through the lens 13 and the optical filter 15 is reflected by the optical multiplexing / demultiplexing filter 14, condensed by the lens 11, and is then amplified by the optical fiber core wire 2a. Will be introduced.

The optical filter 15 is also formed by forming a dielectric multilayer film on a glass plate, and has a characteristic of transmitting excitation light having a wavelength of 1.48 μm and blocking signal light having a wavelength of 1.55 μm. In other words, most of the signal light having a wavelength of 1.55 μm emitted from the optical fiber core wire 2a of the amplification system and passing through the lens 11 passes through the optical multiplexing / demultiplexing filter 14, but approximately several percent of the incident light is transmitted through the optical multiplexing / demultiplexing filter. The light is reflected by the surface 14 and propagates in a direction opposite to the direction of the excitation light, and travels toward the optical fiber core wire 7a of the excitation system. If the leakage component of the signal light reaches the excitation light source 6, the operation of the light source 6 becomes unstable, which is not preferable. Therefore, the optical filter 15 is placed on this optical path.
Are arranged to block leaked light having a wavelength of 1.55 μm.

[0008]

The conventional optical multiplexing / demultiplexing circuit module having the configuration shown in FIG. 2 has a problem that it is difficult to reduce the size. This module has three ferrules 8, 9, and 10 mounted so as to penetrate a case (not shown).
1, 12 and 13 are incorporated, and an optical multiplexing / demultiplexing filter 14 and an optical filter 15 are incorporated. And
Each optical fiber 2, 4 and 7 is drawn out of the case to the outside.

Here, the ferrule 8 (optical fiber core 2a) and the ferrule 9 (optical fiber core 4a) that are optically coupled in the transmission optical path of the optical multiplexing / demultiplexing filter 14 are substantially co-linear as shown in FIG. It becomes a side-by-side arrangement. On the other hand, the ferrule 8 (the optical fiber core wire 2a) and the ferrule 10 that optically couple in the reflection optical path of the optical multiplexing / demultiplexing filter 14 are used.
The (optical fiber core wire 7a) is attached to the case at an angle of about 50 ° to 80 ° with respect to the axial form formed by the ferrule 8 and the ferrule 9.

For this reason, the ferrule 10 has an arrangement relationship in which the ferrule 10 protrudes greatly to the side with respect to the main axis formed by the arrangement of the ferrule 8 and the ferrule 9. That is, almost T
It is shaped like a letter. Further, the collimating lens 11 for the ferrule 8 and the collimating lens 13 for the ferrule 10 are required, respectively, and the optical filter 15 is also required as an individual component. Therefore, the size of the entire case is increased, the optical fiber 4 and the optical fiber 7 are attached in a C-shape, and the mounting space is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and an object of the present invention is to solve the above-mentioned problems and to provide a high-precision optical circuit module which is smaller and requires less mounting space. Is to provide.

[0012]

In order to achieve the above object, in an optical circuit module according to the present invention, a single-core ferrule having a single core of an optical fiber and a core of two parallel optical fibers are provided. A two-core ferrule, an optical filter joined to an end surface of one core wire of the two-core ferrule, a first collimating lens disposed on the optical axis of the one-core ferrule, and a two-core ferrule.
A second collimating lens disposed at a position including two optical axes, and an optical multiplexing / demultiplexing filter disposed near a focal position of the second collimating lens, wherein the core wire of the one-core ferrule and the two-core ferrule are provided. And the two cores of the two-core ferrule are optically coupled through the reflection optical path of the optical multiplexing / demultiplexing filter. 1).

In this configuration, the optical filter may be a filter plate in which a dielectric multilayer film is formed on a glass plate, and the filter plate may be bonded to a predetermined portion of an end surface of the two-core ferrule. Further, a dielectric multilayer film may be directly formed on a predetermined portion of an end face of the two-core ferrule to form the optical filter (claim 3).

Here, the optical multiplexing / demultiplexing filter referred to in the present invention is a WDM (Wavelength Division Multiplexer / Demultiplexer).
Multiplexer) is an optical component that combines or separates light of different wavelengths. In other words, a function of discriminating wavelengths from light containing several different wavelengths and outputting light to the determined terminals (demultiplexing function), and inputting light of several wavelengths from different terminals. Function to emit light containing these wavelengths from one terminal (combining function)
Of these, an optical component having at least one function. Therefore, although the term "optical multiplexing / demultiplexing filter" is used, the concept is not limited to a filter having a multiplexing function and a demultiplexing function, but includes a filter having only a multiplexing function or only a demultiplexing function.

In the present invention, the one-core ferrule and the two-core ferrule
The two ferrules are arranged on the same straight line with the core ferrule, and also in the second invention, the two ferrules are arranged on the same straight line. Further, since the two fiber cores included in the two-core ferrule are very close to each other, the two cores can be handled by a common collimating lens.

Further, in order to perform optical multiplexing and optical demultiplexing, a predetermined opening angle must be provided in the optical path of the two lights. In the present invention, the axis of each core of the two-core ferrule is set to the axis of the collimating lens. Even if the ferrules arranged at positions shifted from the optical axis are arranged on a straight line, the exchangeable optical paths are separated due to the angle between the two optical paths incident and emitted from the two cores, and Light combining / spectral processing is performed.

Further, since the optical filter is joined to the end face of one core wire of the two-core ferrule, light to be transmitted from the other core wire of the two-core ferrule and to be transmitted by the optical multiplexing / demultiplexing filter is reflected. Thus, even if the light enters the one core wire, the light is blocked by the optical filter.

[0018]

FIG. 3 shows a schematic configuration of an optical circuit module according to one embodiment of the present invention. The module of this embodiment corresponds to the optical multiplexing / demultiplexing circuit 3 in the backward pumping type optical fiber amplifier shown in FIG.

As shown in FIG. 3, this optical multiplexing / demultiplexing circuit module has a single-core ferrule 9 having one optical fiber core 4a, and two parallel optical fiber cores 2a and 7a.
And a two-core ferrule 1 having
6, an optical filter 17 joined to the end face of one core wire 7a, a first collimating lens 12 arranged on the optical axis of the single-core ferrule 9, and two optical axes of the two-core ferrule 16 A second collimating lens 18 disposed at a position including the second collimating lens 18 and an optical multiplexing / demultiplexing filter 19 disposed near a focal position of the second collimating lens 18 are provided.

Further, the core wire 4a of the one-core ferrule 9 and one of the core wires 2a of the two-core ferrule 16 are optically coupled in the transmission optical path of the optical multiplexing / demultiplexing filter 19, and two of the two-core ferrule 16 Of the optical multiplexing / demultiplexing filter 19 are optically coupled.

That is, the core wire 2 in the two-core ferrule 16
a and 7a are collimating lenses 18 as shown in FIG.
Are positioned so that light that is displaced from the optical axis and parallel to the optical axis enters and exits. Specifically, the two core wires 2a, 7a
Since the two-core ferrule 16 is arranged symmetrically with respect to the axis, the axis of the ferrule 16 is aligned with the collimating lens 1.
The above condition is satisfied by setting the optical axis to coincide with the optical axis of No. 8. Thereby, as shown in the figure, the light from one core wire 2a (7a) is bent by the collimating lens 18 and converges on the focal position.

In the example shown in the figure, the two core wires 2a and 7a are displaced from the optical axis and are arranged in parallel and symmetrically. However, it is essential that the end of the core wire be displaced from the optical axis or be symmetrical. Instead, if the light is parallel to the optical axis of the collimating lens, it converges to the focal position.

In FIG. 3, one core wire 2a of the two-core ferrule 16 is connected to the erbium-doped optical fiber 2 for amplification in FIG. 1, and the other core wire 7a of the two-core ferrule 16 is an excitation optical fiber in FIG. The core wire 4a of the one-core ferrule 9 is connected to the optical fiber 4 of the output system in FIG.

The optical multiplexing / demultiplexing filter 19 is formed by forming a dielectric multi-layer film on a glass plate. The optical multiplexing / demultiplexing filter 19 has the following optical position relationship between the two-core ferrule 16 and the single-core ferrule 9 and the collimating lenses 12 and 18. Is formed.

That is, when the optical multiplexing / demultiplexing filter 19 is arranged at the focal position, the light reflected there reaches the other core wire 2a (7a). Using this principle, the two ferrules 9 and 16 are arranged almost in a straight line,
Demultiplexing can be performed. The optical path of the light that enters and exits from the single-core ferrule 9 is also shifted from the optical axis of the collimator lens 12 by a predetermined distance. As a result, an optical path indicated by a broken line in the figure is obtained.

Specifically, the optical fiber core 2a of the amplification system
1.55 μm emitted from the lens and passed through the collimating lens 18
Is transmitted through the optical multiplexing / demultiplexing filter 19, condensed by the collimator lens 12, and introduced into the optical fiber core wire 4a of the output system. Excitation light having a wavelength of 1.48 μm emitted from the optical fiber core wire 7a and having passed through the optical filter 17 and the collimating lens 18 is reflected by the optical multiplexing / demultiplexing filter 19, condensed by the same lens 18, and is amplified by the optical fiber of the amplification system. It is introduced into the core wire 2a.

This is an operation as an optical multiplexer, and if the transmission direction of light is reversed, it also operates as an optical demultiplexer. That is, light having a wavelength of 1.55 μm from the optical fiber 2 is transmitted through the optical multiplexing / demultiplexing filter 19 to the optical fiber 4. Light having a wavelength of 1.48 μm from the optical fiber 2 is reflected by the optical multiplexing / demultiplexing filter 19 and transmitted to the optical fiber 7.

The optical filter 17 of this embodiment is formed by forming a dielectric multilayer film on a glass plate, and has a characteristic of transmitting excitation light having a wavelength of 1.48 μm and blocking signal light having a wavelength of 1.55 μm. That is, FIG. 4A shows an example of the filter characteristics of the optical multiplexing / demultiplexing filter 19, and FIG. 4A shows an example of the filter characteristics of the optical filter 17.
(B). Thus, the two have opposite characteristics.

As shown in FIG. 5, a very small optical filter 17 is mounted on a two-core ferrule 1 via a holder 17a.
6 and positioned and joined. Most of the signal light having a wavelength of 1.55 μm emitted from the optical fiber core wire 2a of the amplification system and passing through the collimating lens 18 passes through the optical multiplexing / demultiplexing filter 19, but about a few percent of the surface of the optical multiplexing / demultiplexing filter 19 And propagates in the opposite direction to the traveling of the excitation light, and travels toward the optical fiber core wire 7a of the excitation system. When the leakage component of the signal light reaches the excitation light source 6 in FIG. 1, the operation of the light source 6 becomes unstable, which is not preferable. Therefore, an optical filter 17 is arranged on this optical path,
It blocks leakage light with a wavelength of 1.55 μm.

As another embodiment, as shown in FIG. 6, a dielectric multilayer film may be formed directly on a predetermined portion of the end face of the two-core ferrule 16 to form the optical filter 17. Specifically, the dielectric multilayer film is formed with at least the other core wire 2a masked. After that, when the masking material is removed, the core wire 2a side becomes the optical filter 1
7 is not formed, and the optical filter 1 is provided only on one core wire 7a side.
7 is deposited.

As shown in FIG. 3, the two-core ferrule 16, the collimator lens 18, the optical multiplexing / demultiplexing filter 19, the collimator lens 12, and the one-core ferrule 9 are arranged almost in a straight line. For this reason, the whole is housed in one cylindrical case (not shown). Two optical fibers 2 and an optical fiber 7 are drawn in parallel from one end of the cylindrical case, and one optical fiber 4 is drawn from the other end of the cylindrical case. Since such a module configuration is used, the outer shape of the case is a simple cylindrical shape as compared with the module configuration of the conventional configuration shown in FIG.

Since the two optical fiber cores 2a and 7a contained in the two-core ferrule 16 are very close to each other, the two optical fiber cores 2a and 7a are handled by a common collimating lens 18. it can. Therefore, FIG.
Since the number of optical components incorporated in the module case is reduced as compared with the conventional configuration of the above, it contributes to downsizing of the case. Further, a very small optical filter 17 is connected to the two-core ferrule 16.
2, the space occupied by this portion is extremely small as compared with the case where the optical filter 15 as an individual component is incorporated in the module case as in the conventional configuration of FIG. This also contributes to downsizing of the module case.

[0033]

As described above in detail, in the optical circuit module according to the present invention, the two-core ferrule, the first collimating lens, the optical multiplexing / demultiplexing filter, the second collimating lens, and the one-core ferrule are almost the same. They are arranged side by side in the same straight line, and the whole is housed in one cylindrical case in this arrangement relationship. Two optical fibers are drawn in parallel from one end of the cylindrical case, and one optical fiber 4 is drawn from the other end of the cylindrical case. With such a module configuration, the outer shape of the case is a simple cylindrical shape as compared with the module configuration of the conventional configuration, and the outer dimensions can be significantly reduced compared to the conventional configuration. Further, the arrangement of the three optical fibers at the time of mounting is simple, and the mounting space can be extremely reduced.

[0034] Also, the 2 core included in the 2-core ferrule
Since the two optical fiber core wires are very close, the two core wires can be handled by a common collimating lens.
Therefore, the number of optical components incorporated in the module case is reduced as compared with the conventional configuration, which contributes to downsizing of the case. Further, since a very small optical filter is locally joined to a predetermined portion of the end face of the two-core ferrule 16, the space occupied by this portion becomes extremely small.
This also contributes to downsizing of the module case.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a backward pumping type optical fiber amplifier as an example of an application object of the present invention.

FIG. 2 is a schematic diagram showing a conventional configuration example of an optical multiplexing / demultiplexing circuit module in the optical fiber amplifier.

FIG. 3 is a schematic configuration diagram of an optical multiplexing / demultiplexing circuit module according to an embodiment of the present invention.

FIG. 4A is a diagram illustrating an example of filter characteristics of an optical multiplexing / demultiplexing filter. (B) is a diagram showing an example of the filter characteristics of the optical filter.

FIG. 5 is an end view of the two-core ferrule in the embodiment of FIG. 3;

FIG. 6 is an end view of a two-core ferrule according to another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 optical isolator 2 erbium-doped optical fiber 2a optical fiber core 3 optical multiplexing / demultiplexing circuit 4 optical fiber 4a optical fiber core 5 optical isolator 6 excitation light source 7 optical fiber 7a optical fiber core 8 single core ferrule (conventional) 9 single core ferrule 10 1 core ferrule (conventional) 11 Collimating lens (conventional) 12 Collimating lens (conventional) 13 Collimating lens (conventional) 14 Optical multiplexing / demultiplexing filter (conventional) 15 Optical filter (conventional) 16 2-core filter 17 Optical filter 18 Collimating lens 19 Optical multiplexing / demultiplexing filter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ identification code FI H04J 14/00 14/02 (58) Fields investigated (Int.Cl. ⁶ , DB name) G02B ⁶ /28-6/293 H04B 10/12-10/14 H04J 14/00-14/02

Claims (3)

(57) [Claims] 1. A core wire (4a) of one optical fiber (4).
And a core wire (2a, 7) of two parallel optical fibers (2, 7).
a) and one core wire (7) of the two-core ferrule (16).
a) an optical filter (17) joined to the end face part of (a), a first collimating lens (12) arranged on the optical axis of the one-core ferrule (9), and two of the two-core ferrule (16). A second collimating lens (18) disposed at a position including two optical axes; and an optical multiplexing / demultiplexing filter (19) disposed near a focal position of the second collimating lens (18), The core wire (4a) of the one-core ferrule (9) and one of the core wires (2a) of the two-core ferrule (16) are optically coupled in the transmission optical path of the optical multiplexing / demultiplexing filter (19), and the two-core ferrule ( 16) The optical circuit module, wherein the two core wires (2a, 7a) are optically coupled on the reflection optical path of the optical multiplexing / demultiplexing filter (19). 2. The optical filter (17) is a filter plate in which a dielectric multilayer film is formed on a glass plate, and the filter plate is mounted on a predetermined portion of an end face of the two-core ferrule (16). The optical circuit module according to claim 1. 3. The light according to claim 1, wherein said optical filter is formed by directly forming a dielectric multilayer film on a predetermined portion of an end face of said two-core ferrule. Circuit module.