JPS589119A - Wavelength split multiple circuit - Google Patents

Abstract

PURPOSE:To correct the spectral characteristics even in case when wavelength of a light source has been varied by a temperature, by constituting so that one of a diffraction grating, an optical fiber or an optical detector train has a function for converting a variation of a temperature to a variation of a position or an angle. CONSTITUTION:An incident side fiber 1 is fixed to a body 5 in a state that it has been optically arranged in advance, together with an optical system consisting of a lens 3, and a diffraction grating 4. As for an output side fiber 2, its two sides are constituted of a bimetal 6 in a state that it has been arranged with the optical system, and it is fixed onto the remaining one side of a parallelogram whose other one side is the body 5. In this state, when a temperature variation occurs, two sides of the parallelogram constituted of the bimetal 6 are bent, a position of the output side fiber 2 is moved in parallel, and the spectral characteristics of a branching filter are compensated. Instead of the bimetal, it is also possible to give a turning moment to the diffraction grating by a temperature variation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a wavelength division multiplexing circuit that has a function of correcting wavelength characteristics in response to changes in ambient temperature, which can be signed once using a single transmission line in optical fiber communication. :The so-called wavelength division multiplexing method, which transmits multiple optical signals with different wavelengths, not only enables effective use of transmission lines (reducing cost per line), but also increases flexibility in system configuration. This is an extremely attractive method, as it can be expected to improve the quality of communication as the number of optical fiber communications increases and the scope of application of the optical fiber communication method expands.

Generally, three types of wavelength division multiplexing circuits have been developed to realize this method: one using a prism, one using a combination of interference film filters, and one using a diffraction grating. Among them, a wavelength division multiplexing circuit using a diffraction grating has the advantage that the number of multiplexed circuits can be easily increased and that it can be used in any wavelength range in principle.

It is expected that it will play a central role in wavelength division multiplexing circuits in the future.

On the other hand, a problem with the wavelength division multiplexing method is that the wavelength of the semiconductor laser or light emitting diode commonly used as a light source changes depending on the temperature. For example, AIGaAa (
(aluminum, gallium, arsenic) approx. 3^/℃ in Ruther
, and InGaAaP projected in the 1.0-1.7μ range.
(indium, gallium, arsenic, phosphorous) laser: approx. 5
It has a temperature coefficient of μm/°C.

These are, for example, about 150°C when the temperature changes from θ°C to 50°C.
X (for AJGa 8 laser) and approximately 250X (
In the case of InGaAsP lasers) wavelength changes occur.

A wavelength division multiplexing circuit using a refraction grating separates or combines differences in wavelength as a change in diffraction angle (or a change in position on the focal plane of an optical system). Therefore, as mentioned above (if a temperature change occurs in the two light sources and the wavelength shifts, the optical axis of each wavelength will shift in the optical fiber (input side, output side) section placed at the focal point of the optical system. , on the multiplexing side, as an increase in insertion loss, and in tIIL@, in addition to the increase in insertion loss, crosstalk between channels (between signals of adjacent wavelengths) increases and the quality of the two signals deteriorates. There was a drawback.

SUMMARY OF THE INVENTION An object of the present invention is to provide a wavelength division multiplexing circuit capable of eliminating the above-mentioned conventional drawbacks and realizing a predetermined system operation.

For this purpose, the present invention provides a wavelength division multiplexing circuit for multiplexing or demultiplexing optical signals of different wavelengths using a diffraction grating or an optical fiber or optical fiber optically coupled to the diffraction grating. Either or both of the detector rows is equipped with a function to convert changes in temperature into changes in position or angle, and when the wavelength of the light source changes due to temperature ζ2, the spectral characteristics are adjusted to follow that wavelength change ζ2. It is well known that the diffraction grating has the function of converting the difference in wavelength into a change in angle and separating each wavelength. - 10,000, combine a diffraction grating and a lens system (functions can be integrated by installing a diffraction grating on a concave mirror), and connect an optical fiber or photodetector array to the lens system (in the case of a concave diffraction grating). is the focal position C of the concave mirror), and when arranged, a change in wavelength appears as a change in position.

FIG. 1 is a perspective view of a conventional wavelength division multiplexing circuit to which this principle is applied, and FIG. 2 is a plan view thereof. In the figure, 1 is an input side optical fiber, 2 is an output side optical fiber, and the light wave emitted from the optical fiber 1 passes through a lens 3 and hits a diffraction grating 4, and is separated as a change in the diffraction angle and then sent to the output side optical fiber 2. It is emitted from. As described above, if the wavelength shifts due to a temperature change in the light source, the optical axis of each wavelength will shift in the optical fiber portion. therefore,
In the present invention, when the wavelength of the light source is shifted due to temperature change, the resulting angular change in the diffraction grating portion or the positional change in the cross section perpendicular to the optical axis that occurs at the focal position of the lens system is suppressed. , a wavelength division multiplex circuit with a correction function using a member (using the bimetal effect or the thermal expansion of the metal itself) that has the function of converting temperature changes into changes in position or angle. Configure. It is something.

Hereinafter, embodiments of the invention will be described with reference to the drawings.

FIG. 3 shows an embodiment of the demultiplexer according to the present invention. The input fiber l is optically aligned in advance with the optical system consisting of the lens 3 and the diffraction grating 4 in the main sample 5. The output fiber 2 is aligned with the optical system and has two sides made of bimetal 6, and is fixed on the remaining side of the parallelogram that goes down from the other side of the main body 5. There is.

``When a temperature change occurs here, the configuration changes in the bimetal 6. The material of the bimetal or the length of the two sides made of the bimetal should be appropriately selected so that this amount of change corresponds to the amount of wavelength change of the light source. Therefore, it is possible to compensate for wavelength changes due to the temperature of the light source using this demultiplexer.

FIG. 4 is a T plan view showing another embodiment of the demultiplexer according to the present invention. In this case, the input-side seven eye 6-pair 1, the output-side fiber 2, and the lens 3 are fixed to the main body '5 in advance in a state in which they are optically aligned with the diffraction grating 4. On the other hand, the diffraction grating 4 is optically aligned with the lens 3, the input fiber 1, and the output fiber 2, and has a structure in which it can be rotated so that the angle of incidence of the incident light with respect to the diffraction grating changes. It has become. The diffraction grating 4 has one end fixed to the main body 5, and is connected to a mainspring 7 which provides two rotation moments to the diffraction grating 4 due to temperature changes. For this reason, by appropriately selecting the material and length of the mainspring (2), it is possible to realize the spectral characteristics of the demultiplexer corresponding to the wavelength change on the light source side by subtle rotation of the diffraction grating 4 (2).

In the two embodiments described above, similar effects can be expected even if a photodetector array is placed in place of the output fiber. FIG. 5 shows the temperature characteristics of the spectral characteristics of the duplexer according to the present invention, and shows how the spectral characteristics change from condensed lines to broken lines due to temperature changes.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a wavelength division multiplexing circuit according to the prior art.
Fig. g2 is a plan view thereof, Fig. 3 is a side sectional view showing an embodiment of the present invention in which the position of the output side fiber is displaced in response to temperature change ζ2 using a bimetal, and Fig. 4 is a side sectional view. 5 is a plan view of another embodiment of the present invention in which a change in temperature is converted into a rotation term of a diffraction grating, and FIG. 5 is a diagram showing the spectral characteristics of a duplexer according to the present invention. l・-input end fiber, 2...output side fiber 3・-
Lens, 4--diffraction grating, 5--main body, 6--bimetal, 7--mainspring. Agent Patent Attorney Toshiyoshi Somekawa Go to Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] An array of optical fibers or optical detectors including optical fibers optically coupled to the system and the optical diffraction grating; 6 = a wavelength division multiplex circuit comprising the optical fibers or optical detectors; . (2) Consists of a diffraction grating, an optical i-coupling system, an optical fiber optically coupled to the cage diffraction grating, or a photodetector array including an optical fiber, and a holder for holding the optical fiber or photodetector array, and the temperature The T6 wavelength division polygon circuit is characterized by having a mainspring or cantilever beam that rotates the diffraction grating in response to changes.