JPH01128011A - optical tuner - Google Patents

Abstract

PURPOSE:To provide an optical tuner having a simple structure capable of receiving only the light of a necessary wavelength from plural wavelengths in a piece of an output optical fiber by providing a rotating mechanism to a holographic diffraction grating. CONSTITUTION:Five different signals from the input optical fiber 3 are entrained in the light consisting of five different wavelengths and is projected diagonally to the holographic diffraction grating 1 through an aspherical lens 2, by which the light consisting of the five different wavelengths is subjected to wavelength dispersion and is reflected at the angle varying with each wavelength. This light is condensed by the aspherical lens 2 and only the light of one wavelength N in the light of the different wavelengths is focused onto the end face of the output optical fiber 4. The light of the other wavelengths is not projected onto the photodetecting element 4. The light of the other wavelengths can, therefore, be received by rotating the holographic diffraction grating by using the rotating mechanism to project the light of the required wavelength to the photodetecting element then by converting the same to an electric signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical tuner used on the receiving side of optical wavelength division multiplexing transmission in optical fiber communications.

Background of the Invention In recent years, optical wavelength division multiplexing transmission technology has become a means of increasing signal transmission capacity by effectively utilizing two optical fibers to transmit multiple signals at different wavelengths in optical fiber transmission. It is attracting attention and being used as such.

Conventionally, in the above-mentioned optical wavelength division multiplexing transmission, on the receiving side,
Wavelength devices were used to split light into wavelengths.

An example of this optical demultiplexer will be described below with reference to the drawings.

Figure 3 shows a conventional optical demultiplexer. In Figure 3, 31 is a sawtooth diffraction grating, 32 is a spherical lens, and 33 is a sawtooth diffraction grating.
is an input optical fiber, 34.35° 36.37.38 is an output optical fiber, 39.40° 41.42.43 is an optical-to-electrical converter, the spherical lens 42 is connected to the sawtooth diffraction grating 41, It is arranged between the input optical fiber 43 and the output optical fibers 44, 45, 46, 47, 48.

The operation of the optical demultiplexer configured as described above will be explained below.

By inputting light consisting of five different wavelengths from the input optical fiber 33 to the sawtooth diffraction grating through the spherical lens 32, the light undergoes wavelength dispersion and is reflected at different angles for each wavelength. The lights are converged by the spherical lens, and the lights with different wavelengths are sent to the output optical fiber 34.
, 35, 36° 37.38 and the light-to-electrical converter 3
9°40.41 and 42.43, respectively, and are converted into electrical signals to obtain wavelength characteristics as shown in FIG.

(For example, r1978 Institute of Electronics and Communication Engineers Technical Research Report
C378-166, pages 37 to 42) Problems to be Solved by the Invention However, although the above configuration is suitable for receiving multiple broadband signals at once, it is not suitable for receiving multiple channels of television. When only one signal, or one wavelength, is required at a time, such as broadcast-type optical wavelength division multiplexing, in which the signal is transmitted over a single optical fiber, the optical fiber and optical-to-electrical converter are However, due to the high cost of optical-to-electrical converters, there was a need for parts with new functions.

The present invention takes the above-mentioned problems into consideration and provides an optical chainer that is an optical receiving side device most suitable for broadcast-type optical wavelength division multiplexing transmission.

Means for Solving the Problems In order to solve the above problems, the optical tuner of the present invention has the following features:
an input optical fiber, a light receiving element, an aspherical lens disposed in a space in front of the input optical fiber and the light receiving element, and a space in front of the aspherical lens relative to the optical axis of the input optical fiber. The holographic diffraction grating has a holographic diffraction grating arranged obliquely, and the holographic diffraction grating is equipped with a rotation mechanism.

Effect of the present invention With the above-described configuration, by providing the holographic diffraction grating with a rotation mechanism, only the light of the required wavelength out of a plurality of wavelengths can be received by the output optical fiber. A light chainer with a simple structure can be created.

EXAMPLE Hereinafter, an optical tuner according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows an optical tuner according to the present invention.

In FIG. 1, l indicates a holographic diffraction grating,
2 indicates an aspherical lens.

In the above-mentioned configuration, five different signals from the input optical fiber 3 are put on light consisting of five different wavelengths,
By obliquely entering the holographic diffraction grating 1 through the aspherical lens 2, the light consisting of the five different wavelengths undergoes wavelength dispersion and is reflected at a different angle for each wavelength. Among the lights having different wavelengths, only one light of wavelength N is focused on the end face of the light receiving element 4, and light of other wavelengths is not incident on the light receiving element 4.

Therefore, when receiving light of another wavelength, the rotation mechanism 5 is used to rotate the holographic diffraction grating, and the light of the desired wavelength is incident on the light receiving element and converted into an electrical signal.

FIG. 2 is a diagram showing the imaging characteristics of a spherical lens and an aspherical lens. As shown in FIG. 2+al, a single spherical lens does not form an image at one point due to aberrations.

Therefore, conventionally, a combination of spherical lenses has been used as shown in Fig. 2).

In the present invention, an aspherical lens is used as the imaging component, and as shown in FIG. 2(C), imaging characteristics without spherical aberration can be obtained with a single lens.

Holographic diffraction gratings can be produced more easily and in a shorter time than conventional mechanically scored diffraction gratings.

As described above, according to this embodiment, by attaching a rotation mechanism to the holographic diffraction grating, a conventional optical demultiplexer can have a wavelength selection effect. It provides parts with new functions.

In this embodiment, a reflection type holographic diffraction grating has been described, but similar effects can be obtained with a transmission type holographic diffraction grating.

Effects of the Invention As described above, the present invention allows an optical tuner to be configured with an optical member having a very simple shape by providing a rotation mechanism to a holographic diffraction grating, and is suitable for broadcast type optical wavelength division multiplexing transmission. new optical components can be created.

[Brief explanation of the drawing]

Fig. 1 is a plan view of an optical tuner in an embodiment of the present invention, Fig. 2 is a graph showing wavelength selection characteristics of the optical tuner, Fig. 3 is a plan view of a conventional optical demultiplexer, and Fig. 4 is a graph showing the wavelength selection characteristics of the optical tuner. It is a characteristic diagram. 1... Holographic diffraction grating, 2...
... Aspherical lens, 3 ... Input optical fiber, 4
...... Light receiving element, 5... Rotation mechanism. Name of agent: Patent attorney Toshio Nakao and one other person (see figure 2) λ

Claims (1)

[Claims] one input optical fiber, one light receiving element, an aspherical lens disposed in a space in front of the input optical fiber and the light receiving element, and an aspherical lens arranged in a space in front of the aspherical lens on the optical axis of the input optical fiber. What is claimed is: 1. An optical tuner comprising: a holographic diffraction grating disposed obliquely relative to the holographic diffraction grating, the holographic diffraction grating comprising a rotation mechanism.