JPS58178228A - Optical wavelength dividing device - Google Patents

Abstract

PURPOSE:To make the device compact and low loss, by using a constitution, wherein a prism block, in which a group wavelength dividing interference filter is provided, and a prism block for changing a light path are combined, and constituting the entire device as one block. CONSTITUTION:Parallel luminous flux is vertically inputted to a surface 18 between an angle theta2 and an angle theta3 of the prism block B16, reflected by a total reflecting surface 19, inputted to the prism block A14, and reaches the interference filter plane 7. The condition, under which the light that is emitted from optical fiber and converted into the parallel luminous flux is totally reflected by the total reflecting surface 19 of the prism block B16, is based on the following expression: sintheta2>n0/n1, where n1 is the refractive index of the prism block, and n0 is the refractive index of a medium surrounding the prism block. The condition, under which the light that is transmitted through or reflected by the interference filter 7 of the prism block A14 is totally reflected by a total reflecting surface 20, is based on the following expression: sin (theta1+2theta2-pi/2)>n0/ n1...2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has a function of separating light of a plurality of different wavelengths propagated through one optical fiber into independent directions. This invention relates to an optical wavelength demultiplexing device using an interference filter.

FIG. 1 shows an example of an optical wavelength demultiplexing device using a conventional interference filter. In FIG. 1, each optical fiber (1a) to (
The end face of lens (1e) is placed at the focal plane of each lens (2a) to (2(2). Interference filter (3).

+41. f5+, +61. are each wavelength λ1. λ
2. λ3. λ4. It is a bandpass filter that transmits only light of wavelengths and reflects light of other wavelengths, and is installed at an angle with respect to the incident light. The transmission characteristics of an interference filter change depending on the incident angle of the light beam, so in order to obtain uniform characteristics, the light with wavelengths λ1 to λ2 emitted from the optical fiber (1a) is converted into a parallel beam by the lens (2a). It is converted and enters the first interference filter (3). Here the interference filter (
3) transmits only light of wavelength λl and reflects light of other wavelengths. Therefore, only the light of wavelength λl enters the optical fiber (1b) focused by the lens (2b), and the light of other wavelengths λ
2 to λ4 enters the second interference filter (4).

Here, the interference filter (4) transmits only light of wavelength λ2 and reflects light of other wavelengths. Therefore, an optical fiber (IC) in which only the light of wavelength λ2 is focused by the lens (2C)
The other wavelengths of light λ3 to λ4 enter the third interference filter (5). Similarly, the light with wavelength λ3 is transferred to the optical fiber (ld), and the light with wavelength λ4 is transferred to the optical fiber (1e).
) and the light is demultiplexed. In this way, light is demultiplexed by a bandpass filter, and the demultiplexing characteristics of the optical wavelength demultiplexer are determined by the spectral transmission characteristics of this bandpass filter. Figures 2 and 3 show examples of general spectral transmission characteristics of bandpass filters. Currently, the wavelength bands in which optical wavelength division multiplexing transmission can be realized are the 0.8 μl band and the 1.3 μl band, so Fig. 2 shows a filter with bandpass characteristics in the 0.8 μl band, and Fig. 3 shows a filter with bandpass characteristics in the 0.8 μl band. The spectral transmission characteristics of a filter having bandpass characteristics in the 3μ band are shown.

As shown in the figure, a bandpass filter with a 0.8μ band has a transmission range in the 1.3μ band, and a bandpass filter with a 1.3μ band has a transmission band in the 0.8μ band. Currently, a bandpass interference filter with good characteristics over both wavelength bands has not been obtained.

Therefore, in the optical wavelength demultiplexing device with the conventional configuration described above,
There is a drawback that only one wavelength band of light can be separated out of the two wavelength bands of the 0.8μ haze band and the 1.3μ haze band. The method of realizing a traveling wavelength demultiplexing device that covers both wavelength bands is to use a long-pass filter or short U-length light that first transmits only the long wavelength light for the 0.8 μl band light and the 1.3 μl band light. There is a group demultiplexing method in which the signals are separated using a short-pass filter that transmits Vj, and then sequentially demultiplexed using band-pass filters for each wavelength band. If an optical wavelength demultiplexing device using the t-demultiplexing method is constructed using the conventional method described above, the result will be as shown in FIG. 4, for example. In Fig. 4, the light emitted from the optical fiber (11) first enters the long-pass filter (), and then enters the long-pass filter (7).
The light that passed through the.

The configuration is such that the light is incident on a reflecting mirror (8). As a result, the traveling light emitted from the optical fiber (Ia) first enters the long-pass filter (7), where the light in the 1.3 μl band is transmitted, and the light from the 0.8 vocal fold is reflected. The transmitted light in the 1.3 μ band is further reflected by the reflecting mirror (8) and enters the 1.3 μ band pass filter 191 K, while the light in the 0.8 μ band is reflected by the long pass filter (7). is incident on a bandpass filter +31 with a band of 0.8μ. From this, the light in each wavelength band is sequentially demultiplexed in the process explained in FIG. In the above, the reason why the light transmitted through the long-pass filter (7) is further reflected by the reflecting mirror (8) is to prevent the optical fibers (1b) to (11) that receive the split-wavelength light from overlapping each other. be. Therefore, in the conventional optical wavelength demultiplexing apparatus, when attempting to demultiplex light from the 0.8-band to the 1.3-band, a reflecting mirror is required, which has the drawback of incurring losses. In addition, the configuration becomes complicated and installation of individual parts is not easy.

There were also drawbacks, such as the overall size.

In order to eliminate these drawbacks, the present invention combines prism blocks to achieve miniaturization and low loss, and will be described in detail below with reference to the drawings.

FIG. 5 is a diagram showing an embodiment of the present invention. An isosceles triangular prism block AO41 is bonded to the center of one surface of the flat glass substrate 0, with its base being open. This prism block AQ41 is made up of two rectangular prisms, and a long pass filter (7) is formed in the direction in which they join. A prism block Bαe for changing the incident optical path is joined to one of the hypotenuses of this prism block A (141), and a prism block Bαe for changing the incident optical path is joined to the incident surface parallel to the flat glass substrate 0 of this prism block B (141), and the other end surface is The output optical fiber (1a) was connected.V
A gradient index lens (1
7m+) are joined.

On the other hand, on both sides of the flat glass substrate 0, gradient index lenses (17b) to (IT i) having a length of 9ζ wavelengths are opposed to each other, with light receiving optical fibers (1b) to (11) connected to the other end surface. These gradient index lenses (17
At the interface between b) ~ 071) and the flat glass substrate (to),
Band pass filters (31 to a3 are formed) that transmit only light with specific wavelengths λ1 to λ8.Here, the light with wavelengths λ1 to λ4 passes through 0.8 μlll1, and the wavelengths λ5 to
The light of λ8 is a 1.3μ knitted light. All the elements are bonded using an optical adhesive having almost the same refractive index as the glass medium.

Next, the principle of operation of the embodiment of this invention will be explained.

Figure 6 shows the crism block human mouse and the prism block B.
FIG. 3 is a diagram illustrating the operating principle of the Qli portion. One optical fiber (1m) is used to transmit light with wavelengths λl to λ4 in the 0.8f band,
A total of eight optical signals of wavelengths λ6 to λ- of 1.3 μm wavelength are propagated, and these are independently split into eight optical fibers (1b) to (11).

- Light with wavelengths λl to λB emitted from the optical fiber (1a) enters the gradient index lens (lTa) and is converted into a parallel beam of light by this lens. This parallel light is sandwiched between angles θ2 and θ3 of prism block B@[fi(1[
It is incident perpendicularly to L, is totally reflected by the total reflection surface (2), enters the film block AQ-, and reaches the interference filter surface (71). Here, since a long pass filter is formed, the wavelength of 1.3μ bandless Light from λ5 to λ8 is transmitted, and 0
．． Light with wavelengths λ1 to λ4 in the 8fim band is reflected.

Hereinafter, the optical paths of the light reflected and the light transmitted through the bus filter (71) are symmetrical with respect to the filter surface, and are vertically symmetrical in Fig. 5. I will explain below.

Longpass filter (0,8 pwx reflected at 71
The light with wavelengths λ1 to λ4 in the band is a prism block person Qa
It is totally reflected on the total reflection surface ■ of the flat glass substrate U.
incident at an angle. The light with wavelengths λl to λ4 incident on the flat glass substrate (to) first enters the bandpass filter (3), where only the light with wavelength λl is transmitted, and the remaining wavelengths λ2 to λ
4 light is reflected. The transmitted light of wavelength λl is sent to an optical fiber (lb) by a gradient index lens (17b).
The light having a wavelength of 28 to λ4 that is focused and reflected by the bandpass filter (4) enters the bandpass filter (4). Here, only the light of wavelength λ2 is transmitted and is focused on the optical fiber (lc) by the gradient index lens (17c), and the remaining light of wavelength λ3. λ4
light is reflected. In this way, the light is transmitted through the interference filters 131 to 161.191N formed at the interface between the gradient index lenses (xrb) to (17i) and the flat glass substrate 0.
The light with wavelengths λ1 to λ8 that is demultiplexed one by one by O12 is
The light enters the optical fibers (1b) to (li), respectively. Here, the light emitted by the optical fiber (1 m) and converted into a parallel beam is reflected by the total reflection surface (toward) of the prism block BaIA.
The conditions for total reflection at , are based on the following equation.

3inθ2〉−・・・・・・・・・・・・・・・・・・
・・・・・・・・・−・・fi+1 Here, nl is the refractive index of the prism block.

n6 is the refractive index of the medium surrounding the prism block. Next, prism block A (14 interference filter surfaces (7
The conditions for the traveling light transmitted or reflected by 1 to be totally reflected by the total reflection surface are based on the following equation.

@in(θ1+2θ2 2) > page ・・・・・・
...... 121 Also, at this time, the angle of incidence on the interference filter surface (7) is β1. The angle of incidence β2 on the flat glass substrate (to) is expressed by the following equations.

β1=202−ii−−−−−1・・・・・・・・・・・・
Shout...Bright...131β2=2(θ2+02)-π...
・・・・・・・・・・・・・・・・・・ +41 Here, the angle of incidence β2 on the flat glass substrate (to) is when the refractive index on the flat glass substrate side is the same as that of the prism block t14. is the incident angle to the bandpass filter (3) ~161.191~U. Multilayer interference filters have a property that their transmission characteristics deteriorate when the angle of incidence of light on the filter surface is 25 degrees or more, so the prism blocks λα- and BaB are designed with βl and β2 in consideration of this. 2
It is necessary to design it so that the temperature is 5 degrees or less. For example, if the outside medium is air (no=1) and the material of the prism is BK-7 (nl-1,51), which is the most commonly used material, then if θ2=55 degrees and θ1-45 degrees, then β1. β
Both can be set to J'y. Also, at this time, total reflection conditional expression (1).

(21 is fully satisfied. Since such a prism can be easily manufactured, this grism block AQ
The combination of 4 and B@ can be easily realized.

In this way, in an optical wavelength demultiplexing device with a configuration of 9 or more, 0.8
Optical demultiplexer covering JllK band and 1.3μ band.

Each element for demultiplexing, collimating and condensing lenses, and light input/output fibers can be arranged on both sides of a single flat glass substrate, and can be realized using only a tongue, which has the advantage of a simple configuration. Furthermore, since all of the light emitted from the optical fiber passes through a glass medium, Fresnel loss that occurs when entering a medium with a different refractive index can be reduced.

Since the configuration is such that all optical path conversion is performed by the total reflection surface, there is an effect that loss can be reduced. Furthermore, the entire optical wavelength demultiplexing device can be configured as one block, which has the advantage of being easy to fix and allowing for miniaturization.

Although the case where light of eight wavelengths is demultiplexed has been described above, it is possible to construct an optical wavelength demultiplexing device for any number of demultiplexers with a similar configuration.

Further, although only the function as an optical wavelength demultiplexing device for separating two or more wavelengths has been described, it is clear that this device can also be applied as an optical wavelength multiplexing device by reversing the direction of the light beam shown in FIG.

As described above, the optical wavelength demultiplexing device according to the present invention uses a configuration in which a prism block having a group demultiplexing multilayer interference filter installed therein and a prism block for changing the optical path can be used to achieve 0. The optical wavelength demultiplexer i, which covers a wide wavelength range from the 8μ wavelength band to the 1.3μ wavelength range, can be constructed as a single block with a simple configuration, making it compact.

This has the advantage of reducing losses.

[Brief explanation of the drawing]

Figure 1 is a top view of a conventional optical wavelength demultiplexing device, Figure 2 id
FIG. 3 is a diagram showing an example of spectral transmission characteristics of an O, 8μ bandpass interference filter, and FIG. 3 is a diagram showing an example of spectral transmission characteristics of a 1.3μ bandpass interference filter. FIG. 4 is a top view of an optical wavelength demultiplexing device using a conventional group demultiplexing method, and FIG. 5 is a top view of an embodiment of the device according to the present invention.
6 is an enlarged detailed view of the prism block portion of FIG. 5. FIG. In the figure, (la) to (II) are optical fibers, (
2a) to (2e) are optical coupling lenses, t31 to 161d
0.8μ bandpass interference filter. 191~02d1.3μ dew band band pass filter, (7
1 is a long-pass interference filter, t8+ is a reflecting mirror, (2)
is prism block A, lL9 is right angle prism, Ql
l is prism block B, (17a) to (ffi)
is a gradient index lens for optical coupling, (ill is the incident surface of prism block B, am is the total reflection surface of prism block B, and aI is the total reflection surface of prism block A. In the figure, the same or equivalent Parts are indicated with the same reference numerals. Agent Shin Kuzuno - Stalk 4 Shame S's base t ρ

Claims (1)

[Claims] In a medium whose refractive index is n(1, sin θ〉−・・・−・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・ (1) Vertex angle θ1 that satisfies the town relationship. A block A is formed by joining two right-angle prisms having a refractive index n1 into an isosceles triangle shape with the apex angle θl as the apex and forming a multilayer interference filter on the boundary surface. It is joined at the bottom of the part. 5 inches (θ1+2θ2 2 ) > nl on one side of the two equal hypotenuses of the above block person.
・・・・・・・・・ (2; θ3=−−θl ・・・・
・・・・・・・・・・・・・・・・・・・・・・・・
- Angle θ2 that satisfies the relationship of +31. Angle θ3. refractive index n
A triangular prism block B having an angle θ2 is joined on the surface opposite to the angle θ2 so that the angle θ3 touches the apex of the block A, and on the surface between the angles θ2 and θ3, the output light is emitted through a lens. A fiber is connected to the block A of the flat glass substrate, and on both sides of the block A of the flat glass substrate, lenses having light receiving optical fibers connected to the other end are arranged facing each other on the F-arrayed glass substrate, and an interface between the lens and the flat glass is arranged. An optical wavelength demultiplexing device characterized by each having a multilayer interference filter formed thereon.