JPS61226713A - Optical module for optical wavelength multiplex transmission - Google Patents

Abstract

PURPOSE:To simplify and economize an optical module by providing plural interference film filters at desired tilt angles between a photosemiconductor element and an optical fiber on the photosemiconductor element side with spacer glass between and arranging another photosemiconductor element on the optical axis of reflection of the interference film filters. CONSTITUTION:A light signal with wavelength lambda3 propagated in an optical fiber 12-2 for transmission as shown by an arrow 14 passes through a rod lens 35 to enter spacer glass 16, wherein the light becomes nearly parallel light; and the light is converged on the photodetection surface of a semiconductor photodetecting element 24 through a lens 23-1 after passing through an interference filter 19, spacer glass 17, an interference film filter 21, and spacer glass 18, so that the light signal is converted photoelectrically. A light signal with wavelength lambda1 which is emitted by a semiconductor light emitting element 25 is converted by a lens 23-3 into parallel light, which is incident on an interference film filter 20 at an angle theta1. The light signal with wavelength lambda1 which passes through the interference film filter 20 is incident on the interference film filter 19 and reflected in an angle direction of about 2theta1 to enter the rod lens 35; and the light is converged into the optical fiber 12-2 for transmission and propagated as shown by an arrow 13. Consequently, a small-sized, simple, and low-cost optical multiplexer/demultiplexer is obtained.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is for optical wavelength multiplexing transmission in which a single optical fiber transmission line is used to transmit optical signals of different wavelengths on the upstream and downstream sides of the transmission line. Regarding optical modules.

[Background of the invention]

Wavelength multiplexing transmission technology in optical fiber communications is important for economicalization. In the wavelength division multiplexing transmission described above, an optical multiplexer/demultiplexer is an essential device.

Conventionally, there is a two-wave multiplexer/demultiplexer for two-wave multiplexing as shown in Figure 1, which has been designed to reduce the number of optical multiplexer/demultiplexer components and make them more compact. ``Multiplexer/Demultiplexer'', Research and Practical Application Report, Vol. 32, No. 11 (1983),
P2375-P2385), 1.1' is a focusing rod lens.

2 is a bandpass filter that transmits the wavelength λ and reflects the wavelength λ, and 3, 4.5 are optical fibers.

First, the wavelength λ transmitted from the optical fiber 3.

The light beams of λ are each incident on a focusing rod lens 1. At this time, the light having the wavelength λ passes through the bandpass filter 2, is focused by the focusing rod lens 1', and is propagated to the optical fiber 5. On the other hand, the light having the wavelength λ is reflected by the bandpass filter 2, focused by the focusing rod lens l, and propagated to the optical fiber 4. Such a multiplexer/demultiplexer requires a plurality of focusing rod lenses, and since optical fibers are used at the input and output ends of the focusing rod lenses, the number of parts increases. had. Furthermore, since the diameter of the converging rod lens is approximately 21 mm, high-precision manufacturing technology is required to arrange the optical fibers and bandpass filters and obtain the desired optical characteristics. be.

[Purpose of the invention]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an optical module for optical wavelength division multiplexing transmission that is simpler and more economical.

(Summary of the Invention) The present invention provides a gradient index rod lens for optical coupling between an optical semiconductor element and an optical fiber. In addition, another optical semiconductor element is provided on the optical axis reflected by the interference film filter to constitute an optical module for optical wavelength multiplex transmission.

[Embodiments of the invention]

FIG. 2 shows an embodiment of the optical module for optical wavelength multiplexing transmission of the present invention, which is an example of three-wavelength multiplexing bidirectional transmission. That is, optical signals with wavelengths λ and λ are transmitted in the direction of arrow 13 within the transmission optical fiber 2-2.

The optical signal having the wavelength λ is propagated in the direction of the arrow 14, and the transmission optical fiber 2-
Place 2. An interference filter 9 is provided on the reflective end surface.
, 20, 21, 22 with spacer glass 16.17.
18 is provided. A semiconductor light-receiving element (for receiving an optical signal of wavelength λ) 24 with a lens 23-1 is mounted on an extension of the central axis of the rod lens, and a semiconductor light-emitting element (with a lens 23-2) is mounted on the radial side of the rod lens. For emitting optical signals with wavelength λ)26. This configuration includes a semiconductor light emitting element 25 (for emitting an optical signal of wavelength λ) with a lens 23-3. The wavelength characteristics of the interference film filters 19, 20, 21, and 22 are as shown in FIG. 3, and are composed of a short wavelength pass filter and a long wavelength pass filter.The operation summary of FIG. 2 will be described below. . The optical signal of wavelength λ that has propagated in the direction of arrow 14 within the transmission optical fiber 2-2 enters into the rod lens 35. The optical signal of wavelength λ that has passed through the rod lens 35 and entered the spacer glass 16 is converted into substantially parallel light, and is passed through the interference film filter 9. Spacer glass 17. Interference film filter 21. The light passes through the spacer glass 18 and is focused onto the light receiving surface of the semiconductor light receiving element 24 by a lens (ball lens or gradient index rod lens) 23-1, where it is photoelectrically converted. Semiconductor light emitting device 25 with wavelength λ
The optical signal is converted into parallel light by a lens (spherical lens, hemispherical lens, gradient index rod lens) 23-3, and is incident on the interference film filter 20 at an angle θ. Interference film filter 2
0 allows optical signals of wavelength λ to pass. Interference film filter 2
The optical signal of wavelength λ that has passed through 0 is incident on the interference film filter 9. The interference film filter 9 reflects the optical signal with the wavelength λ and is tilted at an angle of θ with respect to the central axis of the rod lens 35, so the optical signal with the wavelength λ that is incident on the interference film filter 19 is approximately 2θ. The angular direction of, i.e.
The light is reflected in the direction of the central axis of the rod lens 35, passes through the spacer glass 16, and enters the rod lens 35. As the optical signal propagates leftward within the rod lens 35, the beam diameter of the optical signal having the wavelength λ is narrowed, the beam is focused within the propagation optical fiber 2-2, and the beam is propagated in the direction of the arrow 13. The optical signal of the semiconductor light emitting device 26 with a wavelength λ is transmitted through a lens (ball lens, hemispherical lens, gradient index rod lens, etc.) 23
−2, it is converted into parallel light and sent to the interference film filter 22 at an angle θ
incident at

The interference film filter 22 passes an optical signal of wavelength λ.

The optical signal of wavelength λ that has passed through the interference film filter 22 enters the interference film filter 21 through the spacer glass 17. The interference film filter 21 reflects the optical signal of wavelength λ,
In addition, since the rod lens 35 is tilted at an angle of θ with respect to the central axis, the optical signal of wavelength λ2 incident on the interference film filter 21 is directed at an angle of about 20°, that is, in the direction of the central axis of the rod lens 35. The reflected light passes through the spacer glass 17 and enters the interference film filter 9 . Since the interference film filter 9 passes the optical signal with the wavelength λ 2 , the optical signal with the wavelength λ 2 passes through the spacer glass 16 and enters the rod lens 35 .

As it propagates to the left inside the rod lens 35, the beam diameter of the optical signal with wavelength λ decreases to 9.

The light is focused into the transmission optical fiber 2-2 and propagated in the direction of arrow 13.

As described above, it can be realized with a small number of parts, a small size, and a very simple configuration. Furthermore, since the interference film filter can be configured with a short wavelength pass type and a long wavelength pass type, it is possible to suppress an increase in loss due to wavelength fluctuations of a semiconductor light emitting element compared to a case where a band pass type filter is used. Further, the semiconductor light receiving element 24. Semiconductor light emitting device 25
．． 26 are spaced apart from each other, optical and electrical crosstalk can be prevented. In addition, since the heat generating part is not concentrated in one place, it prevents changes in the characteristics of each filter 19 to 22 due to temperature rise when housed in a small case, and prevents deterioration of the characteristics of the adhesive used to bond the spacer glass and the filter. be able to. In addition, since the semiconductor light emitting elements 25 and 26 are inclined at an angle with respect to the axis of the rod lens, 25.26
The reflected light within the module of the emitted light is transmitted to the light receiving element 24.
can be suppressed from entering the

FIG. 4 shows an embodiment of a spacer glass block with an interference film filter disposed on the reflective end face of a rod lens. (a) is a front view.

(b) is a top view, (C) is a bottom view, and (d) is a side view. The block in this case has a rectangular parallelepiped configuration with length 02 width Q and height a. The arrangement is stable if it is a rectangular parallelepiped.

Glass blocks are easy to cut and polish. A feature of this method is that it is easy to form an interference film filter. i,
n and n can be selected to be arbitrary values. However, Q 1 and Q 2 are preferably approximately equal to or thicker than the diameter of the rod lens.The cross section of the block may be a circular polygon instead of a quadrangle.

FIG. 5 shows another embodiment of the optical module for optical wavelength division multiplexing transmission of the present invention. This is an optical module for three-wave bidirectional multiplex transmission, with a semiconductor light emitting element 25°26 and a lens 23-2.
．． 23-3, interference film filters 20 and 22 are provided on one side.

If θ and θ are made equal, the semiconductor light emitting device 26 with lens 23-2 and the semiconductor light emitting device 25 with lens 23-3
can be arranged in parallel, reducing assembly and adjustment time. That is, the block 31 can be constructed as an integrated component, and optical axis adjustment can be completed by finely adjusting this in the x, y, and z directions. Further, if θ = θ, the spacer glass 17 becomes a parallelogram, which facilitates manufacturing.

Furthermore, since the configuration is such that the light emitted from the semiconductor light emitting elements 25 and 26 does not enter the light receiving element 24, the amount of near-end crosstalk attenuation can be increased. Also, in this configuration, the second
It can be made even smaller than the one shown. The block 31 may be housed in one container to suppress unnecessary light leakage, and the spacer glass 18 may be omitted.

FIG. 6 shows another embodiment of the optical module for optical wavelength division multiplexing transmission of the present invention. This is the case with an optical module for four-wave bidirectional multiplex transmission. The structure is such that wavelengths λ 1 and λ 2 are propagated in the direction of arrow 13 and wavelengths λ 1 and λ are propagated in the direction of arrow 14. 2
8 reflects only the optical signal of wavelength λ, and wavelengths λ, λ
, λ is an interference film filter that transmits optical signals of λ. 2
9 transmits only the optical signal of wavelength λ, and wavelengths λ, λλ
It is an interference film filter that reflects the optical signal of

30 is a semiconductor light receiving element that receives an optical signal of wavelength λ.

In Figure 2, the interference membrane filter 9.20°21.2
The characteristics of 2 can be selected as shown in FIG. 7, and 24 can have the configuration shown in FIG.

As described above, 24, 25, 26, and 30 may be either semiconductor light emitting devices or light receiving devices. Further, the number of wavelength multiplexing can easily be two or more. The semiconductor light emitting device may be either a semiconductor laser or a light emitting diode. In addition to optical modules for bidirectional communication, 24, 25, 26,
By making all of 30 semiconductor light emitting elements or light receiving elements, an optical module for one-way communication may be formed.

θ ~ 0 is selected from a range of several orders of magnitude to several tens of degrees, and furthermore,
The light-receiving element 2 can achieve extremely large near-end crosstalk attenuation.
In addition, reflected light from the filters 22, 21, 19 of the light emitted from the light emitting element 26 does not enter the light receiving element 24.

〔Effect of the invention〕

According to the present invention, it is possible to combine an optical coupling function and an optical multiplexing and demultiplexing function with a small number of parts, so it is small and simple.
Moreover, there is an effect that a low-cost optical multiplexer/demultiplexer can be provided.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the prior art, FIGS. 2, 5, and 6 are diagrams showing embodiments of the optical module for optical wavelength multiplexing transmission of the present invention, and FIGS. 3 and 7 are diagrams of the present invention. Fig. 4 is a diagram showing the wavelength characteristics of the interference film filter used in the embodiment of the optical module for optical wavelength multiplexing transmission of the present invention. It is a figure which shows an example. Explanation of symbols 12-2...Optical fiber, 24, 25, 26°30.
...Optical semiconductor element, 35...Lens, 16,17゜1
8.27...Block, 19, 20, 21° 22.
28.29...Interference film filter / Figure 2 Figure 4 (b) Onion I %tgA 2Σ 76 (4) Figure 7 (C) Figure (b) r

Claims (1)

[Claims] 1. At least one first optical interference film filter having a predetermined inclination angle on the first optical semiconductor element side of the lens provided between the first optical semiconductor element and the optical fiber. 1. An optical module for optical wavelength multiplexing transmission, characterized in that the block body is provided with a block body, and a second optical semiconductor element is provided on the optical axis reflected by the first interference film filter via a second interference film filter. 2. Claim 1 is characterized in that the inclination angle of the first interference film filter is set so that the input and output lights of the second optical semiconductor element and the optical fiber can be focused on each other. Optical module for optical wavelength division multiplexing transmission. 3. An optical module for optical wavelength division multiplex transmission according to claim 1, characterized in that when two or more first interference film filters are provided, the angles of inclination are the same.