JPH04264506A - Optical multiplexer/demultiplexer - Google Patents

Abstract

PURPOSE:To provide the optical multiplexer/demultiplexer which facilitates optical axis alignment and has small light loss. CONSTITUTION:A slab type intermediate waveguide 10, channel type demultiplexing waveguides 12, multiplexing waveguides 13, and two-way waveguides 14 are provided on a substrate 16 in monolithic structure and the alignment of the optical axes is facilitated. The demultiplexing waveguides 12 and multiplexing waveguides 13 are provided on one side of the intermediate waveguide 10 and the two-way waveguides 14 are provided on the other side. A total reflecting surfaces 18 are provided on the opposite sides of the two-way waveguide 14 from the intermediate waveguides 10. When the difference (d) in length between adjacent two-way waveguides 14 is set to an optional suitable constant value, wavelength-multiplexed light can be converged on constant positions differing with the wavelength at the time of the incidence of the light on the intermediate waveguide 10 from the multiplexing waveguides 13 through the intermediate waveguide 10, two-way waveguides 14, and reflecting surfaces 18. The demultiplexing waveguides 12 are arranged at the convergence position of the light. The two-way waveguides 14 are arranged radially about the multiplexing waveguides 13f to narrow down the convergence area of the light by the wavelengths, thereby reducing the light loss.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical multiplexer/demultiplexer used, for example, in wavelength multiplexed optical communications.

0002

2. Description of the Related Art Conventionally, in wavelength division multiplexing communications, optical multiplexers and demultiplexers have been used to separate light into wavelengths and to multiplex lights with different wavelengths. As an optical multiplexer/demultiplexer, for example, Document 1: Coherent optical communication Institute of Electronics, Information and Communication Engineers 19
October 15, 1988 p. There is a diffraction grating type proposed in 57-59.

FIG. 3 is an exploded perspective view schematically showing the overall structure of the optical multiplexer/demultiplexer disclosed in Document 1. The optical multiplexer/demultiplexer shown in the figure includes a fiber array 10, a lens 12, a diffraction grating 14, an array holder 16, a grating holder 18, and a housing 20.
Consists of. The fiber array 10 is an array of a plurality of input/output optical fibers 22, and is fixed to an array holding section 16. Further, the diffraction grating 14 is provided on a grating holder 18. Then, the array holder 16, lens 12, and grating holder 18 are attached to the housing 20, and the optical axes of the fiber array 10, lens 12, and diffraction grating 14 are aligned.

0004

However, in the conventional optical multiplexer/demultiplexer described above, it is difficult to align the optical axes of the fiber array 10, lens 12, and diffraction grating 14, and it takes time and effort to create the optical multiplexer/demultiplexer. There was a problem with the cost.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical multiplexer/demultiplexer in which a slab waveguide and a channel waveguide are monolithically provided on a substrate in order to solve the above-mentioned conventional problems.

[0006]

[Means for Solving the Problems] In order to achieve this object, the optical multiplexer/demultiplexer of the present invention includes a slab-type intermediate waveguide, a channel-type multiplexer waveguide, a channel-type demultiplexer waveguide, and a channel-type reciprocating waveguide. A reciprocating waveguide is provided on a substrate, and has at least one multiplexing waveguide and a plurality of demultiplexing waveguides coupled to one side of the intermediate waveguide, and a plurality of reciprocating waveguides coupled to the other side of the intermediate waveguide. A reflecting surface is provided on the opposite side of the intermediate waveguide, and the reciprocating waveguides are arranged radially such that the waveguide spacing increases as the distance from the intermediate waveguide increases, and the difference in length between adjacent reciprocating waveguides is constant; The wavelength-multiplexed light output from the multiplexing waveguide is input to the reciprocating waveguide corresponding to the multiplexing waveguide via the intermediate waveguide, guided to the reflecting surface, reflected by the reflecting surface, and output from the reciprocating waveguide. , is characterized in that the light from the multiplexing waveguide is input to the corresponding demultiplexing waveguide for each wavelength via an intermediate waveguide.

[0007]

As described above, the optical multiplexer/demultiplexer of the present invention includes a slab-type intermediate waveguide, a channel-type multiplexer waveguide, a channel-type demultiplexer waveguide, and a channel-type reciprocating waveguide on a substrate. These waveguides can be created using known microfabrication techniques, waveguide creation techniques, etc. Therefore, each waveguide can be created using a mask that draws a waveguide pattern with the optical axes of the waveguides aligned with each other. Therefore, alignment of the optical axes of these waveguides can be simplified.

Further, the reciprocating waveguides are arranged radially such that the waveguide interval (the interval between adjacent reciprocating waveguides) increases as the distance from the intermediate waveguide increases. Therefore, it is possible to reduce the optical loss when the light output from the multiplexing waveguide is input to the reciprocating waveguide via the intermediate waveguide, and the light from the multiplexing waveguide output from the reciprocating waveguide can be It is possible to reduce optical loss when inputting to the demultiplexing waveguide via the waveguide.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the drawings are merely shown schematically to the extent that the invention can be understood, and therefore the invention is not limited to the illustrated examples.

FIG. 1 is a plan view schematically showing the overall configuration of an embodiment of the present invention. The optical multiplexer/demultiplexer of this example is
As shown in the figure, a slab-type intermediate waveguide 10, a channel-type branching waveguide 12, a channel-type multiplexing waveguide 13, and a channel-type reciprocating waveguide 14 are provided on a substrate 16. The intermediate waveguide 10 is a flat waveguide, and the branching waveguide 12,
The combining waveguide 13 and the reciprocating waveguide 14 are band-shaped (stripe-shaped) waveguides. In addition, in the figure, the branching waveguide 12,
The combining waveguide 13 and the reciprocating waveguide 14 are shown with dots.

A plurality of branching waveguides 12 and at least one multiplexing waveguide 13 are provided on one side of the intermediate waveguide 10.
are optically coupled, and a plurality of reciprocating waveguides 14 are optically coupled to the other side of the intermediate waveguide 10. In this embodiment, only one multiplexing waveguide 13 is provided, and end faces 12a and 13a of the splitting waveguide 12 and multiplexing waveguide 13 are brought into contact with one end face 10a of the intermediate waveguide 10 and optically coupled. Similarly, the end surface 14a of the reciprocating waveguide 14 is brought into contact with the other end surface 10b of the intermediate waveguide 10 and optically coupled. Optical fibers 22 are then coupled to the other end faces 12b and 13b of the branching waveguide 12 and the combining waveguide 13, respectively.

Further, a reflecting surface 18 is provided on the opposite side of the reciprocating waveguide 14 from the intermediate waveguide 10. In this embodiment, the reflective layer 20 having a lower refractive index than the reciprocating waveguide 14 is attached to the reciprocating waveguide 14.
A reflective surface 18 is provided on the substrate 16 in contact with the end surface 14b of the waveguide 4, and a reflective surface 18 that totally reflects light is formed at the interface between the reciprocating waveguide 14 and the reflective layer 20.

Furthermore, the reciprocating waveguides 14 are arranged radially such that the waveguide interval (the interval between adjacent reciprocating waveguides 14) increases as the distance from the intermediate waveguide 10 increases. In this embodiment, the reciprocating waveguide 14 is a straight waveguide, and the extension line of the axis T1 of the waveguide 14 is the end face 13a of the combining waveguide 13.
The reciprocating waveguides 14 are arranged radially such that the extension line of the axis T1 of the reciprocating waveguide 14 passes through the intersection S of the end surface 13a of the multiplexing waveguide 13 and its axis T2.

Further, the difference in length between adjacent reciprocating waveguides 14 is made constant. When the reciprocating waveguides 14 are counted sequentially from the left side of the figure, the lengths of the n-th and n+1-th reciprocating waveguides 14 are expressed as L(n) and L(n+1), respectively (where L(n) and L(n+1) are the lengths in the direction along the reciprocating waveguide 14), the n-th and the n+1-th
The difference d in the length of the second reciprocating waveguide 14 is d=|L(n)−
L(n+1)|=const. In this example, d=const. And L(n)>L(n+1).

Then, the wavelength-multiplexed light outputted from the multiplexing waveguide 13 is transmitted to the multiplexing waveguide 1 via the intermediate waveguide 10.
The light from the multiplexing waveguide 13 is input to the reciprocating waveguide 14 corresponding to 3 and guided to the reflecting surface 18, and the light from the multiplexing waveguide 13 is reflected by the reflecting surface 18 and output from the reciprocating waveguide 14. is input to the branching waveguide 12 corresponding to the waveguide.

FIG. 2 is a diagram for explaining the multiplexing and demultiplexing of light in this embodiment, and in the diagram, the propagation direction of light is indicated by solid lines and broken arrows.

First, the demultiplexing of light in the optical multiplexer/demultiplexer of this embodiment will be explained. In this embodiment, lights λ1 to λ5 having different wavelengths are multiplexed and input from a multiplexing waveguide 13 to an intermediate waveguide 10. Multiplexed light λ1 to λ5
When input to the intermediate waveguide 10, the wave spreads radially as shown by the solid line arrow in the figure and is guided through the intermediate waveguide 10 and input to each corresponding reciprocating waveguide 14, and is totally reflected at the reflecting surface 18 and reciprocated. The signal is input again from the waveguide 14 to the intermediate waveguide 10.

When these lights λ1 to λ5 enter the intermediate waveguide 10 again, they propagate through the intermediate waveguide 10 in different directions for each wavelength due to the diffraction effect of the light, and are therefore demultiplexed. At this time, by setting the difference d between the lengths of adjacent reciprocating waveguides 14 to an arbitrary suitable value D, each reciprocating waveguide 14
It is possible to converge the lights λ1 to λ5 outputted from each wavelength at a fixed position, and to make the convergence position different for each wavelength. For example, the state in which the light λ2 converges is shown by a broken line arrow in the figure. The light λ2 becomes a spherical wave having a spherical wavefront as shown by a broken line P in the figure. Set the difference d to an arbitrary suitable value D
By doing so, a spherical wave can be generated.

A branching waveguide 1 is provided at each convergence position of the lights λ1 to λ5.
For example, light λi is transmitted through the i-th branching waveguide 12 counting from the left in the figure, and each branching waveguide 12 transmits light having a different wavelength.

The phase difference between the lights output from adjacent reciprocating waveguides 14 can be expressed as 2.k0.n0.d. Here, k0 represents the wave number in vacuum, and n0 represents the refractive index of the reciprocating waveguide 14.

Furthermore, the angle Θ formed by the propagation direction of the light L1 input from the multiplexing waveguide 13 to the intermediate waveguide 10 and the propagation direction of the light L2 input from the reciprocating waveguide 14 to the intermediate waveguide 10
can be expressed as the following equation (1). Θ={2・N・dm・(λ/np)・N}/(N・W
) = (2・d)/W−(m/W)・(λ/np)
...(1) However, N is the number of reciprocating waveguides 14 into which the light L1 is input, m is the order of the light L2, and λ is the light L
2 and np represent the refractive index of the intermediate waveguide 10. Further, the widths of all the reciprocating waveguides 14 are equal, and the waveguide width of these reciprocating waveguides 14 is expressed as W.

Since light has the property of traveling in a straight line, the light intensity of the light L2 propagating in the propagation direction where Θ≈0 is the strongest. The order m of the light L2 with the highest light intensity can be expressed as in the following equation (2). m=(np/λ0)・2・d……(2
) However, λ0 is the light L2 propagating in the propagation direction where Θ≒0.
represents the wavelength of

Here, the wavelength of the light L2 is from λ0 to λ0+Δλ
, the angle formed by the propagation directions of the lights L1 and L2 changes from Θ (≈0) to Θ+ΔΘ. Δλ in this case
The relationship between ΔΘ and ΔΘ can be expressed as in the following equation (3). ΔΘ={m/(W・np)}・Δλ...
...(3) As can be understood from equation (3), the larger the order m is, the larger ΔΘ becomes, and therefore the resolution of the optical multiplexer/demultiplexer can be improved. The order m is the adjacent reciprocating waveguide 1
If the difference d between the lengths of 4 and 4 is increased, the difference becomes larger (see equation (2)).

Next, the multiplexing of light in the optical multiplexer/demultiplexer of this embodiment will be explained. Since the optical path in the case of light demultiplexing is reversible, the light λi is input from the i-th demultiplexing waveguide 12 to the intermediate waveguide 10, and is guided through the intermediate waveguide 10 while spreading radially. input to each reciprocating waveguide 14,
Then, it is totally reflected by the reflecting surface 18 and inputted again from each reciprocating waveguide 14 to the intermediate waveguide 10.

When the light λi enters the intermediate waveguide 10 again, it is diffracted in a direction corresponding to its wavelength and guided through the intermediate waveguide 10. At this time, since the difference d between the lengths of adjacent reciprocating waveguides 14 is set to an arbitrarily suitable specific value D, the light λi output from each reciprocating waveguide 14 is Converge on position. As a result, the light λi output from each demultiplexing waveguide 12 can be input to the multiplexing waveguide 13 and multiplexed, and therefore each demultiplexing waveguide 1
It is possible to multiplex the light λi from 2 and transmit the multiplexed light λ1 to λ5 through the multiplexing waveguide 13.

In the optical multiplexer/demultiplexer of the embodiment configured as described above, the reciprocating waveguide 14 is arranged radially with respect to the multiplexer waveguide 13, so that the light from the multiplexer waveguide 13 is transmitted to the multiplexer waveguide 12. When the light from the splitting waveguide 12 converges at the end face 12a position, and when the light from the splitting waveguide 12 converges at the end face 13a position of the multiplexing waveguide 13, the convergence region of the light is prevented from expanding for each wavelength and is narrowed to a narrower region. It can converge light.

In addition, in the optical multiplexer/demultiplexer of this embodiment, the intermediate waveguide 10, the demultiplexer waveguide 12, the multiplexer waveguide 13, and the reciprocating waveguide 14 can be easily created using known microfabrication techniques, waveguide fabrication techniques, etc. Therefore, since each waveguide can be created using a mask that draws a waveguide pattern with the optical axes of the waveguides aligned, alignment of the optical axes of these waveguides can be simplified.

The present invention is not limited to the above-described embodiments; therefore, the shape, size, arrangement position, number of arrangement, and other conditions of each component can be changed as desired.

For example, not only one but a plurality of multiplexing waveguides may be provided. Furthermore, in the above embodiment, the multiplexing waveguide and the multiplexing waveguide are arranged in an array, a waveguide array is constructed from these waveguides, and the multiplexing waveguide is disposed approximately in the center of this waveguide array. A multiplexing waveguide may be placed at the end of the array.

[0030]

Effects of the Invention As is clear from the above description, the optical multiplexer/demultiplexer of the present invention allows a slab-type intermediate waveguide, a channel-type demultiplexing waveguide, a channel-type multiplexing waveguide, and a channel-type reciprocating waveguide. Since they can be monolithically fabricated on the same substrate using known microfabrication techniques, waveguide fabrication techniques, etc., alignment of the optical axes of these waveguides can be simplified.

Furthermore, since the channel type reciprocating waveguide is arranged radially with respect to the channel type multiplexing waveguide, when the light from the channel type multiplexing waveguide converges on the end face position of the channel type multiplexing waveguide, When the light from the waveguide converges at the end face position of the channel type multiplexing waveguide, it is possible to prevent the light convergence area from expanding and converge the light in a narrower area, reducing optical loss. .

[Brief explanation of the drawing]

FIG. 1 is a plan view schematically showing the overall configuration of an optical multiplexer/demultiplexer according to an embodiment.

FIG. 2 is a diagram for explaining the multiplexing and demultiplexing of light in the optical multiplexer/demultiplexer of the embodiment.

FIG. 3 is an exploded perspective view schematically showing the overall configuration of a conventional optical multiplexer/demultiplexer.

[Explanation of symbols]

10: Slab type intermediate waveguide 12: Channel type branching waveguide 13: Channel type multiplexing waveguide 14: Channel type reciprocating waveguide 16: Substrate 18: Reflective surface

Claims (1)

[Claims] 1. A slab-type intermediate waveguide, a channel-type multiplexing waveguide, a channel-type splitting waveguide, and a channel-type reciprocating waveguide are provided on a substrate, and at least one multiplexing waveguide is provided on one side of the intermediate waveguide. and a plurality of branching waveguides are coupled together, a plurality of reciprocating waveguides are coupled to the other side of the intermediate waveguide, a reflecting surface is provided on the opposite side of the reciprocating waveguide to the intermediate waveguide, and the reciprocating waveguide is The waveguides are arranged radially such that the waveguide interval widens as the distance from the intermediate waveguide increases, the difference in length between adjacent round trip waveguides is constant, and the wavelength-multiplexed light output from the multiplexing waveguide is The light from the multiplexing waveguide is input to the reciprocating waveguide corresponding to the multiplexing waveguide through the waveguide and guided to the reflecting surface, and the light from the multiplexing waveguide is reflected by the reflective surface and output from the reciprocating waveguide. An optical multiplexer/demultiplexer characterized in that each wavelength is input to a corresponding demultiplexing waveguide via a wave path.