JPH01128007A - 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 Fourier plane linear 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 on the holographic Fourier plane linear diffraction grating 1 through a 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 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 output optical fiber. The light of the other wavelengths can, therefore, be received simply by rotating the holographic Fourier plane linear diffraction grating by using the rotating mechanism 7 to project the light of the required wavelength on the output optical fiber.

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.

Conventional technology In recent years, optical wavelength division multiplexing transmission technology has become a means of increasing signal transmission capacity by effectively utilizing a single optical fiber to transmit multiple signals on different wavelengths. It is attracting attention and being used as such.

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

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

FIG. 5 shows a conventional optical demultiplexer. In Fig. 5, 51 is a planar linear diffraction grating, 52 is a lens, 53 is a manual optical fiber, 54.55° 56.57.58 is an output optical fiber, and 59, 60° 61.62.63 is an optical-to-electrical converter. The lens 52 is arranged between the planar linear diffraction grating 51 and the input optical fiber 53 and the output optical fiber 54, 55, 56, 57, 58.

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 53 to the plane linear diffraction grating through the lens 52, the light undergoes wavelength dispersion and is reflected at different angles for each wavelength. The lights converged by the lens and having different wavelengths are outputted to output optical fibers 54 and 55.
, 56.57° 58 and the photoelectric converter 59,6
0.61 degrees and 62.63 degrees, respectively, are converted into electrical signals.

(For example, 1978 IEICE Technical Research Report, CS 78-166, pages 37 to 42.) Problems to be Solved by the Invention However, with the above configuration, it is difficult to receive multiple broadband signals at once. However, when only one signal, or one wavelength, is required at a time, such as broadcast-type optical wavelength division multiplexing, which transmits many channels of television signals over a single optical fiber. For this purpose, only one set of optical fiber and optical-to-electrical converter is required, and since the cost of the optical-to-electrical converter is high, parts with new functions have been desired.

The present invention takes the above-mentioned problems into consideration and provides an optical tuner 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 one input optical fiber, one output optical fiber, and a space in front of the input optical fiber and the output optical fiber. and a diffraction grating arranged obliquely to the optical axes of the input optical fiber and the output optical fiber in a space in front of the lens, and the diffraction grating is equipped with a rotation mechanism. be.

Effect of the present invention With the above-described configuration, the holographic Fourier plane linear diffraction grating is provided with a rotation mechanism, so that only the light of the required wavelength from among a plurality of wavelengths can be transmitted.
It is possible to create an optical tuner with a simple structure that can receive light with a single output optical fiber.

EXAMPLE Hereinafter, an optical tuner according to an embodiment 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, 1 indicates a holographic ink Fourier plane linear diffraction grating, and 2 indicates a 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 Fourier plane linear diffraction grating 1 through the 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 of different wavelengths, only one light of wavelength N is focused on the end face of the output optical fiber 4, and light of other wavelengths is not input to the output optical fiber.

Therefore, when receiving light of other wavelengths, the rotating mechanism 5
The holographic Fourier plane linear diffraction grating may be rotated using the holographic Fourier plane linear diffraction grating, and light of a desired wavelength may be incident on the output optical fiber. Reference character e indicates an optical-to-electrical converter, which converts the light incident on the output optical fiber 4 into an electrical signal.

In particular, the first-order diffracted light returns to the incident optical axis in the so-called retro
At the angle θl, the input optical fiber and the output optical fiber can be placed in contact, which is advantageous in terms of miniaturization.

Figure 2 is a diagram showing the wavelength dispersion of a holographic Fourier plane linear diffraction grating. When incident on the holographic ink Fourier plane linear diffraction grating, the light beam of λ1 is diffracted at θ==are−sin(λ,/2d) under draw conditions. Here d is the width of the grid.

Therefore, in order to diffract the light with the wavelength of λ5 to the position (angle) of λl in Fig. 2(a), the holographic
The Fourier plane linear diffraction grating is shown in Figure 2 (θ0 as shown in bl).
It is preferable to perform a rotation operation by −θ5−θ1.

Figure 3 shows the number of grids N-1/d (books/crane) and λ=80
The difference Δθ between the dispersion angle θ at 0 nm and the dispersion angle at (λ−900 nm) when the wavelength increases by 1) 00n is shown.

As can be seen from FIG. 3, the rotation angle of the diffraction grating normally used in this wavelength range may be 10 degrees.

FIG. 4 is a diagram showing the accuracy of rotation angle and the value of wavelength change at λ-800 nm.

From Figure 4, in order to suppress Δλ to 20 nm or less, Δθ is 1.
It must be 0 minutes or less, and if Δθ = 1 minute, 3n
The wavelength change can be suppressed to less than m.

For this reason, it is necessary to use a pulse motor whose rotation is easy to control for the rotation mechanism, and to control the rotation with a small feed rate (at least 10 minutes or less, preferably with a feed accuracy of 1 minute).

In addition, the efficiency beam draw arrangement of a Fourier-shaped diffraction grating provides high efficiency equivalent to that of a sawtooth diffraction grating, making it possible to realize a high-performance optical component.

This Fourier-shaped diffraction grating can be formed by a holographic ink exposure method, a multiple exposure method, or the like.

Holographic ink diffraction gratings are easier to create than traditional mechanically scored diffraction gratings.

As described above, according to this embodiment, by attaching a rotation mechanism to the holographic Fourier plane linear diffraction grating, a conventional optical demultiplexer can have a wavelength selection effect. The input optical fiber and the output optical fiber can be brought closer to each other, and the present invention provides a component with new functions for compact, high-performance optical wavelength division multiplexing transmission.

In this embodiment, a reflection type diffraction grating has been described, but similar effects can be obtained with a transmission type diffraction grating or one including a mirror system.

Effects of the Invention As described above, the present invention provides an optical tuner with an optical member having a very simple shape by providing a rotation mechanism to a holographic Fourier plane linear diffraction grating, and allows broadcast-type optical wavelengths to be adjusted. New optical components suitable for multiplex transmission can be created.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an optical tuner in an embodiment of the present invention;
Figure 2 is a conceptual diagram showing the wavelength dispersion of a holographic Fourier plane linear diffraction grating, and Figure 3 is a diagram showing the number of gratings and 800
A graph showing the dispersion angle at a wavelength of nm, the dispersion angle at a wavelength of 1) 00n, and the difference Δθ from the dispersion angle when the wavelength increases by 1) 00n. Figure 4 shows the accuracy of the rotation angle at a wavelength of 800 nm. FIG. 5 is a perspective view of a conventional optical demultiplexer. ■... Holographic Fourier plane, linear diffraction grating, 2... Lens, 3... Input optical fiber, 4... Output optical fiber, 5...・・・
...Rotation mechanism, 6...Optical-electrical converter, 21
...Holographic Fourier plane linear diffraction grating. Name of agent: Patent attorney Toshio Nakao (1 person) Figure 1 1 - Holographic Fuse IT'D folding lattice 2 - Lens 3 - Human powered optical fiber 4 - Oriented bald fiber

Claims (5)

[Claims] (1) One input optical fiber, one output optical fiber, a lens disposed in a space in front of the input optical fiber and the output optical fiber, and a lens arranged in the space in front of the lens, the input optical fiber and the output optical fiber An optical tuner comprising: a diffraction grating arranged obliquely with respect to the optical axis of an optical fiber, the diffraction grating comprising a rotation mechanism. (2) The optical tuner according to claim (1), characterized in that a Fourier-shaped diffraction grating is used as the diffraction grating. (3) The optical tuner according to claim (1), characterized in that a holographic diffraction grating is used as the diffraction grating. (4) The optical tuner according to claim (1), characterized in that a pulse motor is used as the rotation mechanism, and the accuracy of rotation angle feeding is set to 10 minutes or less. (5) The optical tuner according to claim (1), wherein the diffraction grating is arranged at a Littrow angle with respect to the optical axis.