JPS60262111A - Optical multiplexing and demultiplexing device - Google Patents

Abstract

PURPOSE:To improve the light convergence efficiency of a lens of the optical multiplexing and demultiplexing device and to hold characteristics of filters constant, to prevent reflected light from returning to a light source, and to reduce the number of lenses by arranging optical fibers nearby optical axes of lenses and installing the filters at specific angles to incident light beams. CONSTITUTION:Light beams of wavelengths lambda2 and lambda3 propagating in an optical fiber 22 for transmission are collimated by a cylindrical distributed index lens 27, transmitted through filters 32 and 33, and incident on a prism 30. A filter 35 is installed on one surface of the prism 30 at an angle alpha to a surface perpendicular to the optical axis, and the light of wavelength lambda2 is reflected by this filter 35, passed through a filter 34 installed on a surface (a) of the prism 30 at an angle beta to the surface perpendicular to the optical axis, and converged on an optical fiber 25 through a lens 29. Further, light of wavelength lambda1 is reflected by a filter 32 and light of wavelength lambda4 is reflected by a filter 33; and both are converged on the optical fiber 22.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical multiplexing/demultiplexing device that performs wavelength multiplexing transmission in optical fiber transmission.

Conventional configuration and its problems FIG. 1 shows a conventional optical multiplexing/demultiplexing device.

The configuration of this conventional example will be explained below with reference to FIG. 1. In Figure 1, 1, 2, 3, 4, and 5 are optical fibers, and these optical fibers 1, 2, and 3°4.5 are cylindrical gradient index lenses (hereinafter referred to as lenses).
It is installed on the end face of 6.7.8.9.10.11.

Reference numerals 12, 13, and 14 are wavelength selection filters (hereinafter referred to as filters). filters 12, 13 .
Lenses 7, 8 and 10 are attached to the other side of '14 as shown in the figure. The lens 8 is bonded together as shown in the figure on the surface composed of the lenses 6 and 11, and the filter 13 is bonded to the other surface.

Next, the operation of the above conventional example will be explained. FIG. 2 shows the spectral characteristics of the filters 12, 13, and 14 used in the conventional example, the spectral characteristics of the light source (here, a semiconductor laser), and their positional relationship on the wavelength axis. From the optical fiber 1 to the lens 6 is a wavelength λ2. having the spectral characteristics 16, 1.7 shown in FIG. Light of λ3 is incident. The wavelength λ1. reflected by the filter 12 having the spectral characteristic 19. The light of λ2 is transmitted through lens 6.
The light travels backwards and enters the lens 8. The incident light with a wavelength λ2 passes through a filter 13 having a spectral characteristic 20, is focused by a lens 9, and is emitted from an optical fiber 3. The light of wavelength λ3 that entered the lens 8 is reflected by the filter 13,
Move lens 8 backwards. The retrograde light of wavelength λ3 is transmitted through lens 1
After passing through a filter 14 having a spectral characteristic 21, the light is condensed by a lens 10 and emitted from an optical fiber 4. Spectral characteristics 15 from optical fiber 2 to lens 7
After passing through a lens 7 and a filter 12 having a spectral characteristic 19, the light having a wavelength λ1 is transmitted through a lens 6 to an optical fiber 1
The light is focused and emitted. Lens 11 from optical fiber 5
Light with a wavelength λ4 having a spectral characteristic 18 enters the lens 11 and is reflected by the filter 4 having a spectral characteristic 21.

The reflected light with the wavelength λ4 travels backward through the lens 11 and passes through the lens 8.
incident on . The incident light of wavelength λ4 is reflected by filter 13 having spectral characteristics 20, travels backward through lens 8, and enters lens 6.

The incident light of wavelength λ4 is reflected by a filter 12 having spectral characteristics 19, travels backward through a lens 6, is focused on an optical fiber 1, and is emitted. In the conventional example shown in FIG. 1, optical fibers and lenses 6, 7.8.9. Since the 10° 11 is placed off the optical axis, the light collection efficiency of the lens decreases,
This method has the disadvantage that the spectral characteristics of the filter are shifted, and there is also the problem that a large number of lenses (six in the conventional example) must be used.

OBJECTS OF THE INVENTION The present invention aims to eliminate the above-mentioned drawbacks, and aims to create a structure in which the optical fiber is brought closer to the optical axis of the lens, and to further reduce the number of lenses.

Structure of the Invention In order to achieve the above object, the present invention combines a first lens and a second lens to a first prism, and connects the second prism to the first prism.
A prism is coupled to the second prism, and a third lens is coupled to the second prism, so that the optical fiber is placed near the optical axis of the lens, and the filter is placed at a predetermined angle with respect to the incident angle of the light beam. This improves the light collection efficiency, keeps the characteristics of the filter constant, and prevents the reflected light from the filter surface from returning to the light source. Furthermore, by combining transmission and reflection of the filter, the number of lenses can be reduced.

DESCRIPTION OF EMBODIMENTS The configuration of an embodiment of the present invention will be described below with reference to the drawings. In Figure 3, 22.23°24.25
．． 26 is shown in FIG. 1], 2. '3.4. , 5, and the optical fiber 22
has four different wavelengths λ1. λ2. λ3. λ4 (λ1 and λ4 go in the same direction, λ2 and λ3 go in opposite directions) is transmitted. 2.7.28.29 is a lens that converts the light emitted from the optical fiber into parallel light or converges the light onto the optical fiber. 32, 33, 34, and 35 are filters, and FIG. 4 shows the spectral characteristics of each filter.

Spectral characteristics 40 are of the filter 32, spectral characteristics 41 are of the filter 35, spectral characteristics 42 are of the filter 34, spectral characteristics 4
3 is the characteristic of the filter 33. These filters are 4
It reflects and transmits light of two wavelengths and combines or separates it. In Figure 4, 36.37.38°3
9 is the same light source λ1.15.16.1.7.18 shown in FIG. λ2. λ3. These are the spectral characteristics of 30 in Figure 3
．． 31 is a prism, and light is parallel light in this prism.

Note that (a), (b), and ()→ represent the surfaces of the prism 30, each having a predetermined angle from a surface perpendicular to the optical axis.

Next, the operation of the above embodiment will be explained. Similar to the conventional example shown in FIG. 1, the wavelength λ2. Outputs light of wavelength λ3, and outputs light of wavelength λ0.
The case where light of λ4 is input will be explained. The lights of wavelengths λ2 and λ3 that have propagated through the transmission optical fiber 22 are converted into parallel lights by a lens 27, and after passing through a filter 322 having a spectral characteristic 40 and a filter 33 having a spectral characteristic 43,
The light enters the prism 30. A filter 35 having a spectral characteristic 41 is installed on one surface (b) of this prism 30 at an angle α (20° or less) with respect to a surface perpendicular to the optical axis.

Light with wavelength λ2 is reflected by this filter 35, and transmitted through a filter 34 having spectral characteristics 42, which is installed on the surface (c) of the prism 30 at an angle β with respect to a surface perpendicular to the optical axis, and passes through the lens. 28. The incident light having a wavelength λ2 is focused onto the optical fiber 24 by the lens 28 and is emitted. On the other hand, the light having the wavelength λ3 passes through the filter 35 and enters the prism 31. This light of wavelength λ3 enters the lens 29, is focused by the lens 29 onto the optical fiber 25, and is emitted.

The light of wavelength λ1 that enters the optical fiber 23 in the opposite direction passes through the lens 27.
The light is converted into parallel light and reflected by a filter 32 having spectral characteristics 40 provided on the end face of the lens 27 on the side where the fiber is not provided.

, ::□゛ The reflected light of wavelength λ1 travels backward through the lens 27, is focused by the lens 27 onto the optical fiber 22, and is emitted. Light with a wavelength λ1 entering the optical fiber 26 in the opposite direction is converted into parallel light by a lens 27, and after passing through a filter 32 having a spectral characteristic 40, the light is placed at a slight angle γ with a plane perpendicular to the optical axis. Filter 3 having spectral characteristics 43
It is reflected at 3. The reflected light with wavelength λ4 is passed through filter 32
is transmitted again and enters the lens 27. The light of wavelength λ4 that has entered the lens 27 is focused onto the optical fiber 22 by the lens 27, and is emitted. The reason why the filter 34 is provided obliquely with respect to the optical axis in the optical path of the wavelength λ2 is that a part of the wavelength λ3 is mixed in the component of the light reflected by the filter 35, so this component is This is to remove the light and to prevent a portion of the light reflected by the filter 34 from traveling back along the same optical path, returning to the optical fiber 22, and further returning to the light source, inducing noise. Note that, as is clear from FIG. 3, all the filters are provided obliquely to the optical path, so that the reflected light from the filter surface does not go back to the light source.

In this way, two wavelengths λ2. λ3 is split into two wavelengths λ1. λ4 can be multiplexed. In this example, since the optical fiber can be placed near the optical axis of the lens, the light collection efficiency can be improved, and the shift in the spectral characteristics of the filter caused by moving the optical axis can be improved. can do.

Effects of the Invention The present invention has the above-described configuration, and provides the following effects.

(a) Since the optical fiber can be placed near the optical axis of the lens, it is possible to improve the light collection efficiency, and it is also possible to improve the shift in the spectral characteristics of the filter caused by moving the optical axis off.

(bl) Since it uses a small number of lenses and inexpensive prisms, the price can be kept low.

(C) Since the filter is installed obliquely to the optical path, reflected light from the filter surface does not return to the light source.

[Brief explanation of the drawing]

FIG. 1 is a plan view of essential parts of a conventional optical multiplexing/demultiplexing device, FIG. 2 is a diagram showing the spectral characteristics of a filter and a light source used in the conventional example, and FIG. 3 is a diagram showing the spectral characteristics of a filter and a light source used in the conventional example. FIG. 4, which is a plan view of the main part of the wave demultiplexing device, is a diagram showing the spectral characteristics of a filter and the spectral characteristics of a light source used in an embodiment of the present invention. 22.23,24,25.26...optical fiber, 27
゜28.29・Lens, 30.31・・Prism, 32
゜33.34.35...Filter. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure ↓ Ward I Figure 4

Claims (1)

[Claims] 1st. 1 on each second side. A first prism provided with a second wavelength selection filter, one optical fiber for optical transmission, and two optical fibers for optical input are provided on the focal plane, and the other surface is provided with a third wavelength selection filter. via the above first
A first cylindrical gradient index lens arranged at a predetermined angle on the wavelength selection filter, one light output optical fiber is provided on the focal plane, and the other surface is arranged on the second wavelength selection filter. a second cylindrical gradient index lens arranged at a predetermined angle; and a second prism whose first surface is joined to the third surface of the first prism via a fourth wavelength selection filter. Optical multiplexing comprising a prism and a third cylindrical gradient index lens provided at the focal plane of one optical fiber for outputting light and whose other surface is joined to the second surface of the second prism. Demultiplexing device.