阅读说明：本技术 单光纤双向光学收发器子组件 (Single fiber bi-directional optical transceiver subassembly ) 是由 富田功 于 2019-11-22 设计创作，主要内容包括：提供了一种能够在改善复用/解复用滤波器的波长分离特性的同时还实现紧凑尺寸的单光纤双向光学收发器子组件(BOSA)。单光纤双向光学收发器子组件(1)设置有壳体(10)、光学插座(11)、复用/解复用滤波器(12)、接收侧光电转换单元(13)、发送侧光电转换单元(14)、隔离器(15)和准直透镜(16)。复用/解复用滤波器(12)被布置在光学插座(11)与发送侧光电转换单元(14)之间的光学路径上和光学插座(11)与接收侧光电转换单元(13)之间的光学路径上。隔离器(15)使从发送侧光电转换单元(14)输出的光学信号透过,但是阻挡朝发送侧光电转换单元(14)行进的光学信号。准直透镜(16)被布置在适合壳体(10)的外部尺寸的位置处,并且对入射到复用/解复用滤波器(22)的光进行准直。(A single fiber bi-directional optical transceiver subassembly (BOSA) is provided that is capable of achieving compact size while improving the wavelength separation characteristics of the multiplexing/demultiplexing filter. A single-fiber bidirectional optical transceiver subassembly (1) is provided with a housing (10), an optical receptacle (11), a multiplexing/demultiplexing filter (12), a reception-side photoelectric conversion unit (13), a transmission-side photoelectric conversion unit (14), an isolator (15), and a collimator lens (16). The multiplexing/demultiplexing filters (12) are arranged on an optical path between the optical receptacle (11) and the transmission-side photoelectric conversion unit (14) and on an optical path between the optical receptacle (11) and the reception-side photoelectric conversion unit (13). The isolator (15) transmits the optical signal output from the transmission-side photoelectric conversion unit (14), but blocks the optical signal that travels toward the transmission-side photoelectric conversion unit (14). The collimating lens (16) is arranged at a position suitable for the outer dimension of the housing (10), and collimates light incident to the multiplexing/demultiplexing filter (22).)

1. A single fiber bi-directional optical transceiver subassembly comprising:

a housing:

an optical receptacle;

a transmission-side photoelectric conversion device;

a reception-side photoelectric conversion device;

a multiplexing/demultiplexing filter disposed on an optical path between the optical receptacle and the transmit-side electro-optical conversion device and an optical path between the optical receptacle and the receive-side electro-optical conversion device;

an isolator configured to pass an optical signal output from the transmit-side photoelectric conversion device and block an optical signal traveling to the transmit-side photoelectric conversion device; and

at least one collimating lens disposed at a location that fits an outer dimension of the housing, the at least one collimating lens configured to collimate incident light onto the multiplexing/demultiplexing filter.

2. The single fiber bi-directional optical transceiver subassembly of claim 1, further comprising a holder configured to hold the collimating lens,

wherein at least a portion of the retainer is disposed at a location that fits the outer dimension of the housing.

3. The single fiber bi-directional optical transceiver subassembly of claim 1 or 2, wherein at least one of the at least one collimating lens is disposed at a position that fits the width of the receive-side photoelectric conversion device in the first direction, assuming that the optical axis direction of the optical receptacle is the first direction.

4. The single fiber bi-directional optical transceiver subassembly of claim 3, wherein one of the at least one collimating lenses is disposed on an optical axis between the optical receptacle and the multiplexing/demultiplexing filter.

5. The single fiber bi-directional optical transceiver subassembly of claim 3 or 4,

the isolator is arranged on an optical axis between the transmission-side photoelectric conversion device and the multiplexing/demultiplexing filter, and

one of the at least one collimator lens is arranged on an optical axis between the transmission-side photoelectric conversion device and the isolator.

6. The single fiber bi-directional optical transceiver subassembly of claim 3, wherein one of the at least one collimating lenses is disposed on an optical axis between the multiplexing/demultiplexing filter and the receive side photo-conversion devices.

7. The single fiber bi-directional optical transceiver subassembly of any one of claims 1 to 4, further comprising another collimating lens disposed on an optical axis between the transmit side photo-conversion devices and the multiplexing/demultiplexing filter.

8. The single fiber bi-directional optical transceiver subassembly of any one of claims 1 to 5, further comprising another collimating lens disposed on an optical axis between the receive-side photo-conversion devices and the multiplexing/demultiplexing filter.

Technical Field

The present disclosure relates to a single fiber bi-directional optical transceiver subassembly.

Background

Optical communications are often used for mobile fronthaul and mobile backhaul on mobile networks. Recently, with the transition from Long Term Evolution (LTE) to 5 th generation (5G), higher transmission speeds are required for these parts.

A single fiber bi-directional optical transceiver is an optical device for mobile fronthaul and mobile backhaul. Single fiber bidirectional optical transceivers have functionality for transmitting and receiving optical signals and typically use wavelength multiplexed communications that divide the wavelength band to be used for transmission and reception. Such single fiber bi-directional optical transceivers are provided with, as a component, a single fiber bi-directional optical transceiver subassembly, for example, known as a bi-directional optical subassembly (BOSA).

To meet the demand for higher transmission speed as described above, it is conceivable to improve the wavelength separation characteristics of the multiplexing/demultiplexing filter built in the BOSA. Therefore, it is conceivable to provide the BOSA with a collimating lens that collimates light incident on the multiplexing/demultiplexing filter into a collimated beam.

It should be noted that patent document 1 describes a technique of employing a collimator lens as a component of an optical amplifier, and patent document 2 describes a technique of employing a collimator lens as a component of a three-wavelength-multiplexing optical transceiver module.

CITATION LIST

Patent document

Patent document 1: japanese unexamined patent application publication No.2003-188444

Patent document 2: japanese unexamined patent application publication No.2010-286683

Disclosure of Invention

Technical problem

However, if one attempts to install a collimating lens in the BOSA, the size of the BOSA may increase due to the additional lens.

It is an object of the present disclosure to provide a single fiber bi-directional optical transceiver subassembly capable of achieving compact size while improving the wavelength separation characteristics of the multiplexing/demultiplexing filter.

Problem solving scheme

A single fiber bi-directional optical transceiver subassembly in accordance with one aspect of the present disclosure is provided with:

a housing:

an optical receptacle;

a transmitting-side photoelectric conversion unit;

a reception-side photoelectric conversion unit;

a multiplexing/demultiplexing filter arranged on an optical path between the optical receptacle and the transmission-side photoelectric conversion unit and on an optical path between the optical receptacle and the reception-side photoelectric conversion unit;

an isolator configured to pass an optical signal output from the transmission-side photoelectric conversion unit and block an optical signal traveling to the transmission-side photoelectric conversion unit; and

at least one collimating lens disposed at a location that fits an outer dimension of the housing, the at least one collimating lens configured to collimate incident light onto the multiplexing/demultiplexing filter.

Advantageous effects of the invention

According to the present disclosure, a single-fiber bi-directional optical transceiver subassembly capable of achieving a compact size while improving the wavelength separation characteristics of a multiplexing/demultiplexing filter may be provided.

Drawings

FIG. 1 is a schematic diagram illustrating an example configuration of a single fiber bi-directional optical transceiver subassembly according to a first example embodiment.

Fig. 2 is a cross-sectional view illustrating an example configuration of BOSA according to the second example embodiment.

FIG. 3 is an enlarged cross-sectional view of a portion of the BOSA of FIG. 2.

FIG. 4 is a schematic cross-sectional view of the first collimating lens of the BOSA of FIG. 2 and its holder.

Fig. 5 is a schematic cross-sectional view illustrating the second collimating lens of the BOSA in fig. 2 and a holder thereof, and is also a schematic cross-sectional view illustrating another example of the first collimating lens and a holder thereof.

Fig. 6 is a schematic cross-sectional view illustrating the third collimating lens of the BOSA in fig. 2 and a holder thereof, and is also a schematic cross-sectional view illustrating another example of the first collimating lens and a holder thereof.

Fig. 7 is a cross-sectional view illustrating another example configuration of the BOSA according to the second example embodiment.

Detailed Description

Hereinafter, example embodiments will be described with reference to the accompanying drawings. It should be noted that in example embodiments, identical or substantially identical elements may be denoted with identical reference numerals, and a repeated description of such elements may be omitted in some cases.

< first exemplary embodiment >

A single fiber bi-directional optical transceiver subassembly in accordance with a first exemplary embodiment will be described with reference to fig. 1. FIG. 1 is a schematic diagram illustrating an example configuration of a single fiber bi-directional optical transceiver subassembly according to a first example embodiment. A single fiber bi-directional optical transceiver subassembly may also be referred to as a bi-directional optical subassembly (BOSA), and will be referred to as BOSA hereinafter.

As shown in fig. 1, the BOSA 1 according to the present exemplary embodiment may be provided with a housing 10, an optical receptacle 11, a multiplexing/demultiplexing filter 12, a reception-side photoelectric conversion unit 13, a transmission-side photoelectric conversion unit 14, an isolator 15, and a collimator lens 16.

The BOSA 1 according to the present exemplary embodiment may be installed in a single-fiber bidirectional optical transceiver. BOSA 1 is capable of performing optical communication by Wavelength Division Multiplexing (WDM) with another device by means of an optical fiber, an end portion of which is included in, for example, an optical receptacle 11.

Hereinafter, each component of the BOSA 1 will be described.

The housing 10 may take any shape, but typically has a profile forming a generally rectangular parallelepiped shape. When describing other components, the shape of the housing 10 will be further described. Additionally, the housing 10 may be any material, but typically a metallic material is used.

Although details are not illustrated in the drawings, the optical receptacle 11 is a part for optically connecting between an optical fiber serving as a transmission line of optical communication and the BOSA 1, and is capable of accommodating the optical fiber inside. The optical receptacle 11 is arranged in the housing 10 so that an optical fiber (hereinafter, an internal optical fiber) contained therein can enter light from the multiplexing/demultiplexing filter 12 side and exit light to the multiplexing/demultiplexing filter 12 side.

For example, as shown in fig. 1, the housing 10 may include an opening into which at least a front portion of the optical receptacle 11 is inserted. However, as clarified in the above description, the shape of the connection portion of the housing 10 connected with the optical receptacle 11 is sufficient to ensure any shape of the optical path between the optical receptacle 11 and the multiplexing/demultiplexing filter 12. For example, the connection portion may also have a shape such that the entirety of the optical receptacle 11 is mounted on the outside of the housing 10.

The multiplexing/demultiplexing filter 12 is a filter that multiplexes and demultiplexes optical signals, and although a dielectric multilayer filter, for example, may be applied, the multiplexing/demultiplexing filter 12 is not limited thereto. Also, the multiplexing/demultiplexing filters 12 may be held by a holder, not shown, while being accommodated in the housing 10. The multiplexing/demultiplexing filter 12 is arranged at a position facing the internal optical fiber of the optical receptacle 11. Specifically, the multiplexing/demultiplexing filter 12 is placed on the optical path between the optical receptacle 11 and the transmission-side photoelectric conversion unit 14, and on the optical path between the optical receptacle 11 and the reception-side photoelectric conversion unit 13.

With this arrangement, the multiplexing/demultiplexing filter 12 can multiplex the optical signals having the transmission wavelength output from the transmission-side photoelectric conversion unit 14 and input the multiplexed optical signals into the internal optical fiber of the optical receptacle 11. In addition, the multiplexing/demultiplexing filter 12 may demultiplex an optical signal having a reception wavelength output from the internal optical fiber of the optical receptacle 11 and output the demultiplexed optical signal to the reception-side photoelectric conversion unit 13.

The reception-side photoelectric conversion unit 13 is a part that converts an optical signal into an electrical signal, and may be, for example, a Photodiode (PD) module. Hereinafter, the reception-side photoelectric conversion unit 13 will be referred to as a PD module 13. The transmission-side photoelectric conversion unit 14 is a part that converts an electric signal into an optical signal, and may be, for example, a Laser Diode (LD) module. Hereinafter, the transmission-side photoelectric conversion unit 14 will be referred to as an LD module 14. It should be noted that such PD module 13 and LD module 14 may also be referred to as PD-CAN and LD-CAN, respectively.

Both the PD module 13 and the LD module 14 may be arranged on the outside of the housing 10, but all or some of each module may also be accommodated within the housing 10. In the case where the PD module 13 and the LD module 14 are placed on the outside of the housing 10 in an at least partially exposed state, the housing 10 may have an external shape for placement, such as a concave shape.

The isolator 15 passes the optical signal output from the LD module 14 and blocks the optical signal traveling to the LD module 14. By such an isolator 15, the LD module 14 operates stably. As shown in fig. 1, the isolator 15 may be positioned on an optical path between the LD module 14 and the multiplexing/demultiplexing filter 12, for example, but is not limited thereto.

The collimator lens 16, which is a main feature of the present exemplary embodiment, is a lens capable of collimating light (incident light) entering the multiplexing/demultiplexing filter 12, thereby improving the wavelength separation characteristic of the multiplexing/demultiplexing filter 12.

Further, the collimator lens 16 is arranged at a position suitable for the outer size of the housing 10. In other words, the collimating lens 16 is positioned such that no portion of the collimating lens 16 protrudes from the outer dimension. The position of the collimator lens 16 shown in fig. 1 is merely an example, and in the BOSA 1 according to the present exemplary embodiment, it is sufficient that at least one collimator lens is arranged at a position suitable for the outer dimensions of the housing 10. The collimator lens 16 may be of any type, and for example, a Grin (GRINDEX) lens, a spherical lens, an aspherical lens, or the like may be applied.

As described above, the BOSA 1 according to the present exemplary embodiment employs a configuration in which at least one collimator lens is stored to fit the outer dimensions of the housing 10 (i.e., inside the housing 10). Therefore, the BOSA 1 according to the present exemplary embodiment can not only improve the wavelength separation characteristic of the multiplexing/demultiplexing filter 12 due to the addition of the collimator lens, but also suppress an increase in size of the BOSA due to the addition of the collimator lens.

< second exemplary embodiment >

In the second example embodiment, differences from the first example embodiment will be described mainly with reference to fig. 2 to 7, but various examples described in the first example embodiment are applicable. Fig. 2 is a cross-sectional view illustrating an example configuration of a BOSA according to a second example embodiment, and fig. 3 is an enlarged cross-sectional view of a portion of the BOSA in fig. 2.

As shown in fig. 2, the BOSA2 according to the present exemplary embodiment may be provided with a housing 20, an optical receptacle 21, a multiplexing/demultiplexing filter 22, a PD module 23, an LD module 24, an isolator 25, and first to third collimating lenses 26 to 28.

Here, the housing 20, the optical receptacle 21, and the multiplexing/demultiplexing filter 22 are examples of specific components corresponding to the housing 10, the optical receptacle 11, and the multiplexing/demultiplexing filter 12 in fig. 1, respectively. Also, the PD module 23, the LD module 24, the isolator 25, and the first collimating lens 26 are examples of specific components corresponding to the PD module 13, the LD module 14, the isolator 15, and the collimating lens 16, respectively, in fig. 1. It should be noted that the second and third collimating lenses 27, 28 may be of any type, and for example, GRIN lenses, spherical lenses, aspherical lenses, etc. may be applied.

As shown in the example of fig. 2, the BOSA2 according to the present example embodiment may be provided with a holder 31 that holds the first collimating lens 26. The holder 31 is arranged at a position where at least a part of the holder 31 fits the outer dimension of the housing 20. In addition, the BOSA2 may be provided with holders 32 and 33 that hold the second and third collimator lenses 27 and 28, respectively.

The housing 20 may include a concave portion 20a that engages with a portion of the PD module 23 and a portion of the holder 33, a concave portion 20b that engages with a portion of the LD module 24 and a portion of the holder 32, and a concave portion 20c that engages with a portion of the holder 31. It should be noted that after these parts are joined to each other, the parts may be aligned and then fixed by welding or the like. Also, the housing 20 has a shape that allows the housing portion of the optical receptacle 21 to be attached on the outside of the concave portion 20 c. It should be noted that the connection may be made by welding or the like, for example, after aligning the units. In this way, the housing 20 includes a structure capable of connecting the LD module 24, the PD module 23, and the optical receptacle 21 to which the optical fiber from the transmission line is connected.

In addition, a holder holding the multiplexing/demultiplexing filters 22 and a holder holding the isolators 25 are provided within the housing 20. In other words, the housing 20 is configured such that the multiplexing/demultiplexing filter 22 and the isolator 25 can be mounted inside. As shown in the example of fig. 2, the multiplexing/demultiplexing filters 22 are mounted at angles of 45 degrees and 135 degrees, respectively, with respect to the optical axis of incident light from the optical receptacle 11 side and with respect to the optical axis of reflected light traveling to the PD module 23, for example.

The optical receptacle 21 is a part for connecting an optical fiber (not shown) from a transmission line to the housing 20, and may include an internal optical fiber 21a internally connected to an optical fiber (not shown) from a transmission line, as described above.

The multiplexing/demultiplexing filter 22 includes a function of passing a specific wavelength band among the incident light and reflecting all other wavelength bands. In other words, the multiplexing/demultiplexing filter 22 passes light traveling from the LD module 24 to the internal fiber 21a, and reflects light traveling from the internal fiber 21a (in other words, from the transmission line) to the PD module 23. It should be noted that the latter light is in a different wavelength band from the light from the LD module 24. With this arrangement, the multiplexing/demultiplexing filter 22 can multiplex the optical signals output from the LD module 24 and input the multiplexed signals into the internal optical fiber 21a, and also demultiplex the optical signals output from the internal optical fiber 21a and output the demultiplexed signals to the PD module 23.

The PD module 23 may include a light receiving element (not shown) such as a PD chip. The LD module 24 may include a light emitting element (not shown) such as an LD chip serving as a light source; and a lens 24a that condenses light from the light emitting element onto a predetermined position.

To make the LD module 24 operate stably, the isolator 25 prevents reflected light from the LD module 24 of the multiplexing/demultiplexing filter 22 and from the end face of the internal optical fiber 21a and the like from returning to the LD module 24. Accordingly, the isolator 25 may be disposed on the optical axis between the LD module 24 and the multiplexing/demultiplexing filter 22.

In the present exemplary embodiment, at least one collimator lens arranged to fit the outer dimension of the housing 20 is arranged at a position that fits the width L1 of the PD module 23 in the first direction (the width along the first direction). Here, the first direction refers to an optical axis direction of the optical receptacle 21. Obviously, the position suitable for the width L1 refers to a position outside the PD module 23. The at least one collimating lens arranged is referred to as the first collimating lens 26 in the example of fig. 2.

The first collimating lens 26 converges the collimated light beam from the multiplexing/demultiplexing filter 22 onto the inner optical fiber 21 a. Accordingly, the first collimating lens 26 may be disposed on the optical path between the multiplexing/demultiplexing filter 22 and the internal optical fiber 21a of the optical receptacle 21.

Also, the second collimator lens 27 collimates the light from the LD module 24 into a collimated beam. Thus, for example, the second collimator lens 27 may be arranged on the optical path between the LD module 24 and the isolator 25. However, it is sufficient to arrange the second collimating lens 27 on the optical axis between the LD module 24 and the multiplexing/demultiplexing filter 22, and the isolator 25 may also be arranged on the optical axis between the LD module 24 and the second collimating lens 27. As shown in the example of fig. 2, the second collimating lens 27 does not have to fit completely to the outer dimensions of the housing 20. However, the BOSA2 may be configured such that the second collimating lens 27 is also arranged at a position suitable for the outer size of the housing 20, such as by changing the size and shape of the housing 20.

The third collimator lens 28 condenses the collimated light beam from the multiplexing/demultiplexing filter 22 onto the light receiving element of the PD module 23. Accordingly, the third collimating lens 28 may be arranged on the optical path between the multiplexing/demultiplexing filter 22 and the PD module 23. As shown in the example of fig. 2, the third collimating lens 28 need not fit entirely within the outer dimensions of the housing 20. However, the BOSA2 may be configured such that the third collimating lens 28 is also arranged at a position suitable for the outer size of the housing 20, such as by changing the size and shape of the housing 20. In this case, if the direction perpendicular to the first direction in fig. 2 is designed as the second direction, the third collimator lens 28 is arranged at a position suitable for the width in the second direction.

In this way, in BOSA2, a total of three collimator lenses may be arranged on the optical receptacle 21 side of the multiplexing/demultiplexing filter 22, on the LD module 24 side of the multiplexing/demultiplexing filter 22, and on the PD module 23 side of the multiplexing/demultiplexing filter 22.

Next, the operation in BOSA2 will be described.

The light emitted from the LD module 24 is once condensed in front of the second collimating lens 27 through the lens 24a inside the LD module 24, and then incident on the second collimating lens 27 while being diffused. The emitted light from the LD module 24 is made into a collimated beam by the second collimator lens 27, and passes through the isolator 25 and the multiplexing/demultiplexing filter 22 while maintaining the collimated beam. After that, the transmitted light is condensed onto the inner fiber 21a by the first collimator lens 26.

On the other hand, the light from the transmission line enters the internal optical fiber 21a, is incident on the first collimating lens 26 from the internal optical fiber 21a while being diffused, is made into a collimated beam by the first collimating lens 26, and is incident on the multiplexing/demultiplexing filter 22. The light from the transmission line is reflected by the multiplexing/demultiplexing filter 22 and is condensed onto a light receiving element (not shown) within the PD module 23 by the third collimator lens 28.

The light incident on the multiplexing/demultiplexing filter 22 from the LD module 24 and the internal optical fiber 21a (in other words, from the transmission line) is made into a collimated beam by the first to third collimating lenses 26 to 28. Therefore, even if the wavelength bands of the light emitted from the LD module 24 (transmission light) and the light incident on the light receiving element of the PD module 23 (reception light) are close to each other, the necessary wavelength separation characteristics can be ensured.

Also, as exemplified by the above example configuration, the BOSA2 employs the following configurations (1) to (3) to suppress an increase in the outer size of the housing 20 that may occur due to the addition of the first to third collimating lenses 26 to 28.

(1) In BOSA2, an isolator 25 is installed inside but not outside the housing 20, and a second collimating lens 27 that collimates light from the LD module 24 into a collimated beam is installed in the created empty space. The emitted light from the LD module 24 is made into a collimated beam by the second collimator lens 27, and thus the distance between the isolator 25 and the multiplexing/demultiplexing filter 22 can be shortened. In addition, a second collimator lens 27 is mounted on the optical axis between the LD module 24 and the isolator 25.

(2) The lens 24a has a fixed focal length, and therefore, in the case where no collimator lens is arranged, it is necessary to position the end face of the inner fiber 21a at the focal point of the lens 24 a. Therefore, in the case where the collimating lens is not arranged, it may be necessary to position the internal optical fiber 21a within the housing 20 at a position immediately adjacent to the multiplexing/demultiplexing filter 22. However, in the present exemplary embodiment, the first collimating lens 26 and the second collimating lens 27 are arranged to collimate the light from the lens 24a side into a collimated beam, and thus the constraint on the position of the end face of the inner optical fiber 21a is relaxed. With this arrangement, in the present exemplary embodiment, the inner fiber 21a can be moved back to the end of the housing 20 in a direction away from the multiplexing/demultiplexing filter 22 while keeping the PD module 23 at the same width in the first direction. It should be noted that the first collimating lens 26 is mounted in the empty space created by this back shift.

(3) A portion of the third collimating lens 28 is also mounted within the outer dimensions of the housing 20.

Next, examples of holders (lens holders) 31 to 33 of the collimator lenses will be described with reference to fig. 4 to 6. Fig. 4 is a schematic cross-sectional view illustrating the first collimating lens 26 of the BOSA2 and the holder 31 thereof. Also, fig. 5 is a schematic cross-sectional view illustrating an example of the second collimator lens 27 and its holder 32, and is also a schematic cross-sectional view illustrating another example of the first collimator lens 26 and its holder that can be mounted in the BOSA2 according to the present exemplary embodiment. Fig. 6 is a schematic cross-sectional view illustrating an example of the third collimating lens 28 and its holder 33, and also illustrates another example of the first collimating lens 26 and its holder that can be mounted in the BOSA2 according to the present exemplary embodiment.

As schematically illustrated in fig. 4, to mount the first collimating lens 26 within the housing 20, the holder 31 may have a shape such that a lens barrel surface on the focal point side (lower side of fig. 4) of the first collimating lens 26 abuts an inner circumferential surface of the holder 31. Here, the lens barrel surface refers to an outer circumferential surface of the metal lens barrel 26b that covers the lens part 26a in the first collimating lens 26. In other words, the holder 31 has a shape that holds the focal side of the lens barrel surface in a state where the first collimating lens 26 protrudes to the collimating side (upper side in fig. 4). The reason for this shape is that in order to reduce the overall size of the BOSA2, it is necessary to bring the collimating side (upper side of fig. 4) as close as possible to the components inside the housing 20.

Specifically, the retainer 31 may include a circumferential edge 31a provided on an end surface of the cylindrical body, and a circumferential protrusion 31b provided on an inner circumferential surface of the body. The rim 31a is a portion attached to the outer wall of the housing 20, and the projection 31b is a portion on which the first collimating lens 26 is placed. The projection 31b is provided between the edge 31a of the main body and an end face on the side opposite to the edge 31 a. It should be noted that the holder 31 may be attached to the concave portion 20a on the outer wall of the housing 20 in a state obtained by rotating fig. 4 by 90 degrees to the left.

As schematically illustrated in fig. 5, the holder 32 may have a shape such that the entire lens barrel surface of the second collimator lens 27 abuts against the inner circumferential surface of the holder 32. Here, the lens barrel surface refers to an outer circumferential surface of the metal lens barrel 27b that covers the lens part 27a in the second collimator lens 27.

In particular, the retainer 32 may include a circumferential edge 32a disposed on an end face of the cylindrical body. The edge 32a is a portion attached to the outer wall of the housing 20. It should be noted that the holder 32 may be attached to the concave portion 20b on the outer wall of the housing 20 in a state obtained by rotating fig. 5 by 90 degrees to the right.

As schematically illustrated in fig. 6, the holder 33 may have a shape such that a lens barrel surface on the collimation side (upper side of fig. 6) abuts an inner circumferential surface of the holder 33. Here, the lens barrel surface refers to an outer circumferential surface of the metal lens barrel 28b that covers the lens part 28a in the third collimator lens 28.

Specifically, the retainer 33 may include a circumferential edge 33a provided on an end surface of the cylindrical body, the end surface being on the opposite side to the edge 33a, and a circumferential protrusion 33b provided on an inner circumferential surface of the end surface of the body. The rim 33a is a portion attached to the outer wall of the housing 20, and the protrusion 33b is a portion on which the third collimating lens 28 is placed. It should be noted that the holder 33 may be attached to the concave portion 20c on the outer wall of the housing 20 in a state obtained by vertically inverting fig. 6.

As the holder for holding the first collimating lens 26, a holder shaped like the holder 32 or the holder 33 may be used. However, since it is necessary to bring the collimating side as close as possible to the internal components to reduce the overall size of the BOSA2, a shape like the holder 31 in fig. 4 is considered preferable as a holder that holds the first collimating lens 26.

Here, an example configuration not including the second collimator lens 27 will be briefly described with reference to fig. 7. Fig. 7 is a cross-sectional view illustrating another example configuration of BOSA according to the present example embodiment. BOSA2a illustrated in fig. 7 is obtained by removing the second collimator lens 27 and its holder 32 and installing the LD module 24b instead of the LD module 24 in BOSA2 illustrated in fig. 2. Here, the LD module 24b may be, for example, a gold box type module including the second collimator lens 24 ba. It should be noted that the concave portion 20b has a shape that engages with a portion of the LD module 24 b.

As described above, according to the present exemplary embodiment, BOSA2 or BOSA2a capable of achieving a compact size while improving the wavelength separation characteristics of the multiplexing/demultiplexing filter 22 can be provided. Specifically, in the present exemplary embodiment, the first to third collimating lenses 26 to 28 or 26, 24ba, and 28 are mounted so that collimated light beams can be incident on the multiplexing/demultiplexing filter 22, and the wavelength separation characteristic of the multiplexing/demultiplexing filter 22 is improved. Further, in the present exemplary embodiment, the outer dimensions of the housing 20 may be kept substantially the same as those in the case where the first to third collimator lenses 26 to 28 or 26, 24ba, and 28 are not mounted.

Supplementary explanation will be given for improvement of the wavelength separation characteristic. The wavelength separation characteristic of the multiplexing/demultiplexing filter tends to be optimal in the case where the incident light on the multiplexing/demultiplexing filter is a collimated beam, and tends to be degraded in the case where the incident light on the multiplexing/demultiplexing filter is incident while being converged or diffused. In the latter case, that is, in the case where the incident light on the multiplexing/demultiplexing filter is not a collimated light beam, it is necessary to sufficiently separate the wavelength band of light (transmission light) from the LD module and the wavelength band of light (reception light) to the PD module. Therefore, an optical signal having a wavelength of 1.27 μm and an optical signal having a wavelength of 1.33 μm are used by performing wavelength multiplexing, for example.

The present exemplary embodiment is configured such that a collimated light beam can be incident on the multiplexing/demultiplexing filter 22, thereby enabling the wavelength separation characteristic to be improved in a case where the wavelength band of the transmitted light and the wavelength band of the received light are close. For example, according to the present exemplary embodiment, an optical signal having a wavelength of 1.27 μm and an optical signal having a wavelength of 1.31 μm closer to the zero dispersion wavelength band can be used, thereby enabling a faster transmission speed to be obtained. For example, the BOSA2 including the above-described structure may be installed in a single-fiber bidirectional optical transceiver and used as a technique for increasing the transmission speed from 10Gb/s or less to 25 Gb/s.

Also, as illustrated by the example of the first collimating lens 26, the collimating lens disposed on the optical path between the multiplexing/demultiplexing filter 22 and the internal optical fiber 21a of the optical receptacle 21 may be arranged to fit the outer dimensions of the housing 20. With this configuration, after the LD module 24 side is fixed, the first collimating lens 26 can be fixed, and then the alignment of the inner optical fiber 21a can be easily performed when the optical receptacle 21 is attached thereafter.

< other example embodiments >

The above example embodiments describe example configurations of BOSA, but the shape and configuration are not limited to the illustrated examples. For example, in the second exemplary embodiment, as described above, an example is given in which only the first collimating lens 26 among the collimating lenses mounted in the BOSA2 or BOSA2a fits the outer dimensions of the housing 20. However, the BOSA2 may adopt a configuration such that only the second collimating lens 27 fits the outer dimensions of the housing 20. Also, BOSA2 or BOSA2a may also adopt a configuration such that only the third collimator lens 28 fits the outer dimension of the housing 20 (in this case, the dimension in the vertical direction of fig. 2). Further, BOSA2 or BOSA2a may also adopt a configuration such that two or three of the first collimating lens to the third collimating lens fit to the outer dimensions of the housing 20. Obviously, the first exemplary embodiment and the second exemplary embodiment may also adopt a configuration in which two collimator lenses are provided, or a configuration in which four or more collimator lenses are provided. Further, the various examples described in the first and second example embodiments may be appropriately combined.

It should be noted that the present disclosure is not limited to the various exemplary embodiments described above, and appropriate modifications may be made within the scope not departing from the gist. Further, the present disclosure can also be implemented by appropriately combining the respective exemplary embodiments.

The present invention has been described with reference to exemplary embodiments, but is not limited to the foregoing. Various modifications, which will occur to those skilled in the art, may be made in the arrangement and details of the invention within the scope of the invention.

This application claims priority to japanese patent application No.2019-061894, filed on day 27 of 2019 to the present patent office, the disclosure of which is incorporated by reference in its entirety.

List of reference numerals

1、2、2a BOSA

10. 20 casing

11. 21 optical receptacle

12 multiplexing/demultiplexing filter

13 photoelectric conversion unit (PD module) on receiving side

14 transmitting side photoelectric conversion unit (LD Module)

15. 25 isolator

16 collimating lens

20a, 20b, 20c concave portion

21a internal optical fiber

22 multiplexing/demultiplexing filter

23 PD module

24. 24b LD module

24a lens

26 first collimating lens

26a, 27a, 28a lens element

26b, 27b, 28b lens barrel

27. 24ba second collimating lens

28 third collimating lens

31. 32, 33 holder

31a, 32a, 33a edge

31b, 33b projection