JPH0453908A - Optical multiplexer/demultiplexer and optical module - Google Patents

Abstract

PURPOSE:To minaturize the optical multiplexer/demultiplexer and to decrease the crosstalk by forming a reflecting end face having an angle of about 45 degrees against the waveguide direction in the tip of bend part of a bend waveguide, and also, exposing its reflecting end face so as to come into contact with air. CONSTITUTION:An optical signal which is made incident on an optical multiplexer/ demultiplexer 10 is demultiplexed by an optical multiplexing/demultiplexing waveguide 7 and propagated to demultiplexed light emitting part 6,8 sides of the respective wavelength. The demultiplexer light propagated to a demultiplexed light emitting part 14 consisting of a bend waveguide 4 of roughly and L-shape is emitted in the direction being different by about 90 degrees against the demultiplexed light of other wavelength. In such a state, a reflecting end face 12 is formed in the tip 9 of bend part of the bend wavelength 4, and its reflecting end face 12 is exposed to come into contact with air. Accordingly, the demultiplexed light is subjected to total reflection by the reflecting end face 12 and its propagation direction can be varied by 90 degrees thereby, therefore, a propagation loss caused by providing the bend waveguide 4 is suppressed extremely small. In such a way, the optical multiplexer/demultiplexer can be miniaturized and the electrical and optical crosstalk can be decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical multiplexer/demultiplexer for wavelength multiplexing transmission, and an optical module in which a light emitting element, a light receiving element, etc. are mounted on the optical multiplexer/demultiplexer.

[Prior Art] Wavelength division multiplexing transmission technology C in optical fiber communication is important for economicalization of communication systems.

In wavelength multiplexing transmission, an optical module for wavelength multiplexing transmission, which is equipped with an optical multiplexer/demultiplexer 1, a light emitting element, a light receiving element, a pigtail fiber, and an electronic circuit, is an essential device.

The present applicant has proposed an optical module for wavelength division multiplexing transmission having the configuration shown in FIG. 5 (Imoto).

Others "Waveguide type optical multiplexing/demultiplexing", Hitachi Cable, NO, 0, 8p
p, 19-24.19139), this is an optical multiplexer/demultiplexer 51. of waveguide structure on the same substrate 50. Semiconductor laser LD.

A light receiving element PD and a pigtail fiber 52 are mounted, and the pigtail fiber 52 is mounted at one end of the optical multiplexer/demultiplexer 51, and the semiconductor laser LD and the light receiving element PD are mounted at the other end.
etc. are connected and configured. Furthermore, an electronic circuit 53 for operating the semiconductor laser LD and the light receiving element PD is also mounted on the substrate 50.

[Problems to be Solved by the Invention] By the way, if the configuration of the wavelength multiplex transmission module shown in FIG. 5 is to be realized using the current technology, the semiconductor laser LD and the light receiving element PD must be mounted in the form of a chip.

In that case, the reliability of the chip can be increased by hermetically sealing the entire module. but,
The technology of hermetically sealing the entire module is also currently unfeasible. In addition, in order to increase the coupling efficiency between the semiconductor laser LD and the waveguide, it is necessary to couple them through at least one lens with little aberration, or at present, it is necessary to form a monolink lens with the above function on the waveguide. It's far away.

Therefore, at present, we have no choice but to use a semiconductor laser package in which a semiconductor laser and a lens are mounted on a mount and hermetically sealed, or a photodetector package in which a photodetector and a lens are mounted on a mount and hermetically sealed. . However, the height, width, and length of these packages are all several meters.
The length is about m.

Therefore, as shown in FIG. 6, the distance 2G between the waveguide 54 connected to the semiconductor laser LD and the waveguide 55 connected to the photodetector PD must be several mm or more. If the gap 2G is set to several mm or more, the length B of the curved part will inevitably become longer, and as shown in Figure 7, the total length of the waveguide will become more than 20 mm, making it difficult to miniaturize. There's a problem. There is also the problem that propagation loss increases as the total length of the waveguide increases.

Furthermore, since the semiconductor laser package and the photodetector package are placed close to each other, crosstalk occurs due to optical and electrical signals crossing over.
There is also concern that this may occur. In particular, when performing high-speed, broadband signal transmission (>several hundred Mb/s), the occurrence of crosstalk becomes a serious problem. An object of the present invention is to solve the above-mentioned problems and provide an optical multiplexer/demultiplexer and an optical module for wavelength division multiplexing transmission that are small and have little crosstalk.

[Means for Solving the Problems] The present invention achieves the above object by multiplexing and demultiplexing optical signals of a plurality of wavelengths in a cladding layer formed on a substrate. In an optical multiplexer/demultiplexer in which an optical multiplexer/demultiplexer waveguide is formed, at least one demultiplexed light output portion of the optical multiplexer/demultiplexer waveguide is composed of an abbreviated curved waveguide, and the tip of the bent portion of the curved waveguide A reflective end face having an angle of approximately 45 degrees with respect to the waveguide direction is formed at the end, and the reflective end face is exposed so as to come into contact with the air.

Further, the optical multiplexer/demultiplexer may be formed by connecting a plurality of the optical multiplexer/demultiplexer waveguides on the same substrate, and at least one demultiplexed light output portion of each optical multiplexer/demultiplexer waveguide may be formed of the curved waveguide.

Furthermore, the present invention multiplexes a plurality of optical signals of different wavelengths in a cladding layer formed on a substrate.

Alternatively, in an optical module in which an optical multiplexing/demultiplexing waveguide for multiplexing and demultiplexing is formed and a light emitting element, a light receiving element, etc. are provided at each output end from which the demultiplexed light of the optical multiplexing/demultiplexing waveguide is taken out, the optical multiplexing/demultiplexing waveguide is provided. At least one demultiplexed light output part of the demultiplexing waveguide is composed of an abbreviated curved waveguide, and a reflective end face having an angle of approximately 45 degrees with respect to the waveguide direction is formed at the tip of the bent part of the curved waveguide. At the same time, its reflective end face is exposed so as to come into contact with the air.

[Operation] The optical signal incident on the optical multiplexer/demultiplexer is branched by the optical multiplexer/demultiplexer waveguide and propagated to the demultiplexed light output section of each wavelength. The demultiplexed light that has propagated to the demultiplexed light emitting section formed of the abbreviated curved waveguide is emitted in a direction approximately 90 degrees different from the demultiplexed light of other wavelengths. By forming the above-mentioned reflective end face at the tip of the bent part of the curved waveguide and exposing the reflective end face to contact with air, the branched light is totally reflected at the reflective end face and its propagation direction is changed by approximately 90 degrees. Therefore, the propagation loss due to the provision of the curved waveguide can be suppressed to an extremely low level.

In addition, by forming a plurality of optical multiplexing/demultiplexing waveguides connected according to the number of wavelength components in the incident light, the incident optical signal is sequentially split into optical signals of side wavelengths in each optical multiplexing/demultiplexing waveguide. It is branched and emitted.

Therefore, an optical signal consisting of a large number of wavelength components can be demultiplexed into optical signals of individual wavelengths. Further, by configuring at least one optical signal output portion of each optical multiplexing/demultiplexing waveguide as a substantially I-shaped curved waveguide, the output ends of the demultiplexed light can be sufficiently spaced from each other. Thereby, when a light emitting element, a light receiving element, etc. are provided at the output end of the demultiplexed light, these elements can be arranged with a sufficient distance from each other.

Further, since the optical module is configured such that a light emitting element, a light receiving element, etc. are provided at the output end of the branched light of the optical multiplexer/demultiplexer, these elements can be arranged with a sufficient distance from each other. Therefore, optical crosstalk and electrical crosstalk can be effectively prevented.

[Example] Examples of the present invention will be described.

FIG. 1(a) is a side view showing an example of an optical multiplexer/demultiplexer of the present invention, and FIG. 1(b) is a sectional view taken along the line I--■ in FIG. 1(a). This optical multiplexer/demultiplexer has two distinct wavelengths λ1. λ
A directional coupling type optical multiplexing/demultiplexing waveguide 7 for demultiplexing two input optical signals is formed on the substrate 1. The waveguide is constructed as a buried type. That is, a high refractive index nw()n is formed in the cladding layer 2 with a low refractive index nc formed on the substrate 1.
It is mainly composed of the core waveguides 3 and 4 of c) embedded therein. A linear core waveguide 3 is provided so as to penetrate between a pair of opposing side surfaces of the cladding layer 2, and is configured such that the input end 5 of the optical signals of the wavelengths λ1 and λ2 faces the end face,
The input end 6 of one of the branched optical signals of wavelength λ1 is connected to the end surface R.
Configure.

The core waveguide 4 that is formed close to the linear core waveguide 3 and constitutes the optical multiplexing and demultiplexing waveguide #I7 has a demultiplexed light output section 14 consisting of an abbreviated curved waveguide 1-1. The curved waveguide 11 has an output end 8 with the other wavelength λ2 on an end face where the input end 5 and the output end 6 are formed, and on an end face different from R.
As shown in FIG. 1(b), the one-curved waveguide 11 constituting the curved waveguide 11 has a reflective end face 12 formed by cutting its bent end 9 at an angle of about 45 degrees with respect to the waveguide direction. . In order to expose the reflective end face 12 to the cladding layer 2 so as to make it contact with the air, ? 1113 is formed.

Here, the total reflection critical angle θc at the reflective end face 12
(=2cos-'(nw/n,)) is 92.8 degrees, so when the bending angle θ of the curved waveguide 11 becomes larger than this, the propagation loss at this bend increases rapidly. Therefore, the bending angle θ of the direction waveguide 11 is set to a value close to 90 degrees so as not to exceed 92.8 degrees. Also,
The groove 13 is formed, for example, by digging from the upper surface of the cladding layer 2 using photolithography and dry etching processes. The depth d of the well is dug deeper than the depth at which the core waveguide is embedded, and it may be dug into the substrate 1 if necessary.The width G of the well 13 is required to be at least several μm; The wider the distance, the better the light propagation efficiency.

Note that the substrate 1 is made of semiconductors such as St, GaAs, InP, etc.
fO□, SiO□ with various additives added, glass such as sapphire, or LiNbO5, LiTa0
A ferroelectric material such as i, or even a magnetic material may be used.

Next, the operating principle of this optical multiplexer/demultiplexer will be explained.

There are two different wavelengths λ1 in the linear core waveguide F#13.
．． An optical signal of λ2 is input. Optical signal is optical multiplexing/demultiplexing waveguide F
! ? 17, where an optical signal of wavelength λ1 and an optical signal of wavelength λ2
The optical signal is split into two. One optical signal of wavelength λ1 propagates within the linear core waveguide 3 and is emitted from the output end 6 on the end surface R side. The other optical signal with wavelength λ2 is transmitted through curved waveguide 1.
Propagate within 1.

During propagation in this curved waveguide 11, the optical signal is totally reflected at the reflective end face 12 of the bending part tip 9, and the traveling direction is approximately relative to the traveling direction of the optical signal propagating in the linear core waveguide 3. Can be turned in orthogonal directions. And the optical signal of wavelength λ2 is
The light is emitted from the output end 8 on the side of the end face different from the end face R where the incident @5 and the outgoing end 6 are formed.

By configuring the demultiplexed light output section 14 of the optical multiplexing/demultiplexing waveguide 7 with the abbreviated curved waveguide 1111 in this way, the output ends 6 and 8 of each demultiplexed light can be connected without increasing the total length of the waveguide.
can be formed at an appropriate position. This makes it possible to downsize the optical multiplexer/demultiplexer and reduce propagation loss. Furthermore, as in this embodiment, by completely differentiating the side from which the optical signal of one wavelength λ1 is emitted and the side from which the other optical signal of wavelength λ2 is emitted, it is possible to Since the elements can be provided with a sufficient distance from each other, optical crosstalk and electrical crosstalk can be effectively prevented.

As shown in FIG. 2, the demultiplexed light output section 14 that propagates the optical signal of wavelength λ1 is an abbreviated curved waveguide #II.
It'' may be configured.

The optical multiplexer/demultiplexer 17 shown in FIG.
2. λ2. and λ1, two directional coupling type optical multiplexing/demultiplexing waveguides 7a and 7b are installed on the same substrate.
are formed by connecting them to each other. That is, 21! of one linear core waveguide 3 having an input end 5 and an output end 6 at opposite end positions of the substrate! Two core waveguides 4a constituting the optical multiplexing/demultiplexing S wavepaths 7a and 7b are placed at the i location.
.

4b are formed close to each other. A demultiplexed light output section 14a of these two core waveguides 4a and 4b.

14b is a FIIi L-shaped curved waveguide 1 facing in opposite directions.
It consists of 1a and llb. As a result, an output end 15° 16 of the demultiplexed light is formed on the end surface where the input tIN5 and the output end 6 are formed, and on the opposite end surface U, which is different from R. Also, a curved waveguide 11a.

A reflective end face 12a having an angle of approximately 45 degrees with respect to the waveguide direction is provided at the tip ends 9a and 9b of the bent portion 11b.

12b are formed, and the cladding layer 2 has these reflective end faces 1.
Rectangular arms 13a, 13 to expose 2a, 12b.
b is formed. Optical multiplexing/demultiplexing waveguide 7 on the input #i5 side
a is a curved waveguide 11a that splits light with one wavelength λ2.
It is configured so that the light with wavelengths λ1 and λ3 is guided to the PI and passes through as is. The optical multiplexing/demultiplexing waveguide 7b on the side of the output end 6 is configured to split light with a wavelength λ and guide it to the curved waveguide 11b, while allowing the light with a wavelength λ1 to pass through as is.

Three different wavelengths λ1λ2 . The optical signals of
It is split into two at a. That is, among these three wavelengths, the optical signal with wavelength λ2 is demultiplexed and guided to the curved waveguide 11a side and emitted from the end face, and the remaining optical signals with wavelengths λ1 and λ are guided to the optical multiplexing/demultiplexing waveguide i7b side. be led to. The optical signals with wavelengths λ1 and λ are transmitted through the optical multiplexing/demultiplexing waveguide 7.
After being further split at b, the optical signal of wavelength λ is sent to the curved waveguide #
? The optical signal with the wavelength λl is guided to l1lbflll and emitted from the end surface U, and the optical signal with the wavelength λl propagates as it is in the core waveguide 3 and is emitted from the end surface R. In this way, the demultiplexed light output portions 14a of the respective optical multiplexing/demultiplexing waveguides 7a, 7b.

14b is an abbreviated curved waveguide F! By configuring with @lla and 11b, the three output ends 6, 15, 16 can be formed at different end face positions.

In order to maintain high isolation between wavelengths, interference film filters may be provided at the outputs of the respective demultiplexed lights @6, 15, and 16 to suppress optical signals of undesired wavelengths. Also,
Demultiplexed light output parts 14a, 14 of optical multiplexing/demultiplexing waveguides 7a, 7b
b may be constructed of a curved waveguide having a plurality of bent portions, and the position of the output end may be changed as appropriate.

FIG. 4 shows an embodiment of the optical module of the present invention. This optical module is an optical multiplexer/demultiplexer module for bidirectional transmission constructed using the optical multiplexer/demultiplexer 10 of FIG. 1 described above.

That is, in the optical module 18, the optical fiber 19 is connected to the input @5 on the end surface of the optical multiplexer/demultiplexer 10, the semiconductor laser (light emitting element) 20 with a lens is connected to the output end 6 of the end surface R, and the optical fiber 19 is connected to the above-mentioned output @5 on the end surface. A light receiving element 22 having an interference film filter 21 is provided at the end 8. In addition, the end surface R
is an angle φ so that the optical signal of the semiconductor laser 20 is not reflected by this end surface R and returns to the semiconductor laser 20 again.
It is processed diagonally.

This angle φ is set to 10 degrees or less.The interference film filter 21 is for passing the optical signal of wavelength λ2 and blocking the optical signal of wavelength λ1.

Optical signal oscillated from semiconductor laser 20 (wavelength λ1)
enters the core waveguide 3 of the optical multiplexer/demultiplexer 10, propagates toward the end face side as shown by arrow A, and is emitted into the optical fiber 19. On the other hand, the optical signal (
The wavelength λ2) enters the core waveguide F#I3 from the input end 5, is branched by the optical multiplexing/demultiplexing waveguide #I7, propagates within the curved waveguide 11, passes through the interference film filter 21, and reaches the light receiving element. 22
Injected into the interior.

Since the positions of the semiconductor laser 2o and the light receiving element 22 are thus far apart, the influence of optical crosstalk and electrical crosstalk can be suppressed to a small level. In addition, by configuring the branched light output section 14 of the optical multiplexing/demultiplexing waveguide 7 with an abbreviated curved waveguide #&11, the semiconductor laser 2 can be used without increasing the total length of the waveguide.
Since the optical module 0 and the light receiving element 22 are provided with a sufficient distance from each other, the optical module can be made compact. Note that the optical module may be a demultiplexer module in which only a light receiving element is mounted, or a multiplexer module in which only a light emitting element is mounted.

[Effects of the Invention] In summary, according to the present invention, it is possible to realize an optical multiplexer/demultiplexer and an optical module for wavelength multiplexing transmission that are small and have little electrical and optical crosstalk.

[Brief explanation of the drawing]

FIG. 1(a) is a side view showing an embodiment of the optical multiplexer/demultiplexer of the present invention, FIG. 1(b) is a sectional view taken along the line II in FIG. 1(a),
2 and 3 are diagrams showing other embodiments of the optical multiplexer/demultiplexer of the present invention, FIG. 4 is a diagram showing an embodiment of the optical module of the present invention, and FIG. 5 is a diagram showing an optical fiber for wavelength multiplexing transmission. FIG. 6 is a perspective view showing a conventional example of a module; FIG. 6 is a diagram showing a conventional example of an optical multiplexer/demultiplexer; FIG. It is a graph showing the calculation result of the relationship. In the figure, 1 is a substrate, 2 is a cladding layer, and 7.7a. 7b is an optical multiplexing/demultiplexing waveguide, 6.8 is an output end, 9°9a, 9
b is the tip of the bent part, 1o is the optical multiplexer/demultiplexer, 11, lla, l
lb is a curved waveguide, 12° 12a, 12b are reflective end faces,
14.14a. 14b is a demultiplexed light emitting section, 18 is an optical module, 20 is a light emitting element, and 22 is a light receiving element. Patent Applicant Hitachi Cable Co., Ltd. Patent Attorney Nobuo Kinutani Figure 1 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. An optical multiplexer in which an optical multiplexing/demultiplexing waveguide for multiplexing, demultiplexing, or multiplexing and demultiplexing a plurality of optical signals of different wavelengths is formed in a cladding layer formed on a substrate. In the demultiplexer, at least one demultiplexed light output portion of the optical multiplexing/demultiplexing waveguide is comprised of a substantially L-shaped curved waveguide, and the tip of the curved portion of the curved waveguide is formed at an angle of approximately 45 degrees with respect to the waveguide direction. What is claimed is: 1. An optical multiplexer/demultiplexer characterized in that a reflective end face is formed and the reflective end face is exposed so as to come into contact with air. 2. The optical multiplexing/demultiplexing waveguide is formed by connecting a plurality of them on the same substrate, and at least one optical combining/demultiplexing waveguide of each optical multiplexing/demultiplexing waveguide is formed of the curved waveguide. Optical multiplexer/demultiplexer. 3. An optical multiplexing/demultiplexing waveguide for multiplexing, demultiplexing, or multiplexing/demultiplexing optical signals of a plurality of different wavelengths is formed in the cladding layer formed on the substrate, and the optical multiplexing/demultiplexing waveguide is In an optical module in which a light emitting element, a light receiving element, etc. are provided at each output end from which the subsequent light is extracted, at least one branched light output section of the optical multiplexing/demultiplexing waveguide is comprised of a substantially L-shaped curved waveguide; An optical module characterized in that a reflective end face having an angle of approximately 45 degrees with respect to the waveguide direction is formed at the tip of a bent portion of a curved waveguide, and the reflective end face is exposed so as to come into contact with air.