JP3798380B2 - Waveguide type optical wavelength multiplexer / demultiplexer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a waveguide-type optical wavelength multiplexer / demultiplexer used in, for example, an optical transceiver, and more particularly to reduce noise mixed in received light.
[0002]
[Prior art]
FIG. 3 shows the structure of the waveguide type optical wavelength multiplexer / demultiplexer described in Patent Document 1. In the waveguide type optical wavelength multiplexer / demultiplexer, a multilayer optical filter 3 is formed on the end face 2 of the optical waveguide substrate 1, and a first optical waveguide 4 and a second optical waveguide 5 coupled in a V shape on the end face 2. The first wavelength light A (for example, 1.5 μm) is incident from the transmitting light emitting element 8 toward the end face 2 through the first optical waveguide 4 and reflected by the multilayer optical filter 3 to be second. And is transmitted from the second optical waveguide 5 to the other party through the optical fiber 7. A second wavelength light B (for example, 1.3 μm) transmitted from the other party through the optical fiber 7 is incident from the second optical waveguide 5 toward the end face 2, and the second wavelength light B is a multilayer film. The light is transmitted through the optical filter 3 and emitted from the end face 2 to the outside of the optical waveguide substrate 1, the emitted second wavelength light B is received by the light receiving unit 6, and the transmission signal on the other party side is received. In this way, a two-way call can be performed by the single optical fiber 7.
[0003]
One of the important elements that enables this two-way call is the multilayer optical filter 3. The multilayer optical filter 3 shown in FIG. 3 is set to a characteristic that reflects the first wavelength light A of 1.5 μm and transmits the second wavelength light B of 1.3 μm. On the other hand, a multilayer optical filter having a characteristic of transmitting the first wavelength light A of 1.5 μm and reflecting the second wavelength light B of 1.3 μm is provided on the communication partner side.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-253848
[Problems to be solved by the invention]
As described above, the multilayer optical filter 3 completely reflects the component of the first wavelength light A with respect to the parallel light propagating in the transmission axis direction of the first optical waveguide 4 , and the second wavelength light B A multilayer film is formed on the end face 2 so that the above-mentioned components are completely transmitted.
However, the actual multilayer optical filter 3 has a characteristic that its transmission and reflection characteristics shift depending on the incident angle of incident light. In the waveguide type optical wavelength multiplexer / demultiplexer assumed by the present invention, the wavelength characteristic of the dielectric multilayer film is optimized with respect to the angle at which the transmission axis of the first optical waveguide 4 is incident on the multilayer optical filter 3. Designed. That is, for the parallel light propagating in the transmission axis direction of the first optical waveguide 4, the component of the first wavelength light A is completely reflected and the component of the second wavelength light B is completely transmitted. A multilayer film is formed on the end face 2.
[0006]
However, the light actually incident on the multilayer optical filter 3 is not only the plane wave in the transmission axis direction of the first optical waveguide 4, but the emitted light beam from the optical waveguide 4 draws an opening angle around the transmission axis at the end face 2. In fact, there is a component that propagates into the multilayer film at a considerable angle from the transmission axis direction of the first optical waveguide 4 (not shown).
The component of the first wavelength light A that is incident at an angle greatly deviating from the incident angle used as the standard for designing the multilayer optical filter 3 deviates from the reflection band of the multilayer due to the incident angle dependency. A transmission phenomenon occurs (see FIG. 4). For example, when the transmitted light P1 as an error is directly irradiated onto the light receiving surface 6A (see FIG. 4) of the light receiving unit 6 of the optical transceiver shown in FIG. 3, the light receiving unit 6 emits light other than the second wavelength light B. The component is also detected, which has the disadvantage of becoming noise. In order to reduce this noise, it is necessary to reduce the light receiving sensitivity, so that the reduction of the light receiving sensitivity becomes a big problem.
An object of the present invention is to provide a waveguide type optical wavelength multiplexer / demultiplexer that can prevent an optical component to be received by a communication partner from leaking to its own light receiver.
[0007]
[Means for Solving the Problems]
According to a first aspect of the present invention, a multilayer optical filter is formed on the end face of the optical waveguide substrate, the first optical waveguide intersects at the end face, and the second optical waveguide, and the first wavelength light is the first wavelength light. Incident from the optical waveguide toward the end face, reflected by the multilayer optical filter and coupled to the second optical waveguide, and the second wavelength light enters from the second optical waveguide toward the end face, and the multilayer optical filter Is formed on the end face of the waveguide type optical wavelength demultiplexer configured to include a light receiving portion that receives the second wavelength light emitted from the end face to the outside of the optical waveguide substrate. that with refractive Oriritsu the outer surface of the multilayer film optical filter is attached an optical resin layer having a 1.5 refractive index greater than, configured the waveguide is provided a gap between the light receiving unit the optical resin layer An optical wavelength multiplexer / demultiplexer is proposed.
According to the present invention, in the waveguide type optical wavelength multiplexer / demultiplexer in which the multilayer optical filter is formed on the end face of the optical waveguide substrate, the refractive index is about 1.5 on the outer surface of the multilayer optical filter formed on the end face. A waveguide-type optical wavelength multiplexer / demultiplexer with an optical resin layer having a refractive index of 1 is proposed.
[0008]
Effect an optical resin film layer refractive Oriritsu the outer surface of the multilayer film optical filter having a refractive index of about 1.5 is provided according to the present invention, provided with a gap between the light receiving unit The optical resin film layer Because of the configuration, the transmitted light that causes an error propagates through the optical resin film layer at a relatively large angle with respect to the transmission axis of the first optical waveguide, and against the interface between the optical resin layer and air. Reaching a large incident angle θ. Here, if the refractive index of the optical resin layer is higher than the refractive index “1” of air, most of the first wavelength light incident on the interface at this large angle θ is reflected at the interface between the optical resin layer and the air layer. In particular, the component where the incident angle θ is θ> θc (θc is a critical angle) is totally reflected, and an effect that the error light mixed in the light receiving portion that should receive the second wavelength light can be greatly reduced can be obtained. .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
1 and 2 show an embodiment of the present invention. Parts corresponding to those in FIGS. 3 and 4 are denoted by the same reference numerals. In the present invention, a multilayer optical filter 3 is formed on the end face 2 of the optical waveguide substrate 1. The end face 2 has a first optical waveguide 4 and a second optical waveguide 5 coupled in a V shape. Wavelength light A enters from the first optical waveguide 4 toward the end face 2, is reflected by the multilayer optical filter 3 and is coupled to the second optical waveguide 5, and the second wavelength light B is the second optical waveguide. A light receiving portion 6 that enters from the waveguide 5 toward the end face 2, passes through the multilayer optical filter 3, exits from the end face 2 to the outside of the optical waveguide substrate 1, and receives the emitted light of the second wavelength. In the waveguide type optical wavelength multiplexer / demultiplexer configured to comprise:
While attached optical resin layer 11 bending to the outer surface of the multilayer film optical filter 3 Oriritsu has a refractive index of about 1.5, which is formed on the end face 2, the light receiving surface 6A of the light-receiving portion 6 and the optical resin layer 11 This is characterized in that a gap 12 is provided between the two.
[0010]
The optical resin layer 11 may be a light-transmitting silicon resin or UV curable epoxy resin. The higher the numerical value of the refractive index, the smaller the critical angle θc, and the smaller the critical angle θc, the more errors. The effect that light can be reflected is obtained. Usually, the optical resin having the refractive index n = 1.5 which is most often used can sufficiently achieve the object of the invention. When an optical resin having a refractive index n of n = 1.5 is used, the critical angle θc is θc = sin ⁻¹ (1 / 1.5) = 41.8 °. That is, light having an incident angle θ greater than 41.8 ° is all reflected at the interface between the optical resin layer 11 and air.
[0011]
Further, since the optical resin layer 11 is provided, the transmitted light forms a sufficient spread inside the optical resin layer 11 and then reaches the interface with the air, so that the optical resin layer 11 has a certain thickness. desirable. Actually, a good effect was confirmed with a thickness of about several tens of μm. In forming the optical resin layer 11, the resin may be applied to the end surface 2 of the substrate 1 with a dispenser or the like and cured. In addition, the shape of the interface with the air does not require special accuracy, and may be a flat surface that can be obtained normally.
[0012]
In the embodiment shown in FIGS. 1 and 2, the wavelength of the first wavelength light A to be transmitted is 1.5 μm, and the wavelength of the second wavelength light B to be received is 1.3 μm. Although the case where the present invention is applied to the multiplexer / demultiplexer has been described, the waveguide-type optical wavelength multiplexer / demultiplexer used on the communication partner side transmits the first wavelength light A and reflects the second wavelength light B. Although it is set to the characteristic, it can be easily understood that the same effect can be obtained even if the present invention is applied to the multilayer optical filter having this characteristic.
The light receiving unit 6 described above can be applied to a light receiving element. However, instead of the light receiving element, for example, for a wavelength multiplexing optical system in which the light receiving unit 6 includes a large-diameter optical transmission means such as a multimode optical fiber. It can also be applied to couplers and the like.
[0013]
【The invention's effect】
As described above, in the present invention, since the optical resin layer 11 having a refractive index larger than the refractive index of air is disposed on the outer surface of the multilayer optical filter 3, the light having the first wavelength temporarily passes through the multilayer optical filter 3. Even if the light is transmitted, most of the transmitted light is reflected at the interface between the optical resin layer 11 and the air as shown in FIG. 2, and the amount reaching the light receiving surface of the light receiving element 6 can be made extremely small. Incidentally, in the past, the amount of transmitted light of the first wavelength was about 1/1000 of the amount of light of the first wavelength, but by applying this invention, it is improved to about 1 / 10,000. Can do. As a result, there is an advantage that the S / N ratio can be greatly improved.
Further, as a side effect of the present invention, since the outer surface of the multilayer optical filter 3 is covered with the optical resin layer 11, the multilayer optical filter 3 not only protects the optical waveguide substrate 1 but also the multilayer film. The effect of remarkably improving the moisture resistance of the optical filter 3 and the optical waveguide is also obtained.
[Brief description of the drawings]
FIG. 1 is a perspective view for explaining an embodiment of the present invention.
FIG. 2 is a cross-sectional view for explaining the structure of a main part of the present invention.
FIG. 3 is a perspective view for explaining a conventional technique.
FIG. 4 is a cross-sectional view for explaining a problem of a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Optical waveguide board | substrate 6 Light-receiving part 2 End surface 7 Optical fiber 3 Multilayer film optical filter 8 Light emitting element 4 1st optical waveguide 11 Optical resin layer 5 2nd optical waveguide 12 Air gap

Claims (2)

A multilayer optical filter is formed on the end face of the optical waveguide substrate, and has a first optical waveguide and a second optical waveguide that intersect at the end face, and the first wavelength light is transmitted from the first optical waveguide to the end face. Is incident on the multilayer optical filter, is reflected by the multilayer optical filter and is coupled to the second optical waveguide, and the second wavelength light is incident on the end surface from the second optical waveguide and is transmitted through the multilayer optical filter. In the waveguide type optical wavelength demultiplexer configured to include a light receiving unit that emits light from the end face to the outside of the optical waveguide substrate and receives the emitted second wavelength light,
With refractive Oriritsu the outer surface of the multilayer optical filter formed on the end surface is attached a layer optical resin having 1.5 refractive index greater than, provided a space between the optical resin layer and the light-receiving portion A waveguide-type optical wavelength multiplexer / demultiplexer characterized by comprising A multilayer optical filter is formed on the end face of the optical waveguide substrate, and has a first optical waveguide and a second optical waveguide that intersect at the end face, and the first wavelength light is transmitted from the first optical waveguide to the end face. Is incident on the multilayer optical filter, is reflected by the multilayer optical filter, and is coupled to the second optical waveguide. The second wavelength light is incident from the second optical waveguide toward the end surface, and is transmitted through the multilayer optical filter. In the waveguide type optical wavelength demultiplexer configured to include a light receiving unit that emits light from the end face to the outside of the optical waveguide substrate and receives the emitted second wavelength light,
  An optical resin layer having a refractive index of about 1.5 is attached to the outer surface of the multilayer optical filter formed on the end face, and a gap is provided between the optical resin layer and the light receiving portion. 1. A waveguide type optical wavelength multiplexer / demultiplexer characterized by comprising.

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