JPS607410A - Light source for optical communication - Google Patents

Abstract

PURPOSE:To control the extent of higher-order mode excitation to an optimum quantity of incident light, and use an optical fiber in a maximum transmission band state by providing an adjusting mechanism for the incidence conditions of the optical fiber between a condenser lens and an optical fiber end part. CONSTITUTION:Light emitted by a light emitting element 14 is incident on a lens 11 to obtain a parallel beam P, which strikes a pinhole 13. The striking beam is made incident to a lens 12 through the hole 131 of the pinhole 13. Therefore, the quantity of the incident light beam between the pinhole 13 and lens 12 is small depending upon how large the angles of incidence to spaces A and B encircled with broken lines and solid lines are large. Then, adjusted light beam is converged by the lens 12 and incident on the optical fiber 15. Thus, incidence NA to the optical fiber 15 is adjusted.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a light source for optical communication, and more particularly to a light source for optical communication in which the mode of incidence on an optical fiber can be adjusted γ11.

TECHNICAL BACKGROUND Generally, it is well known that the transmission bandwidth varies greatly depending on the optical fiber input conditions. This tendency is particularly noticeable in Gl fibers intended for broadband performance.

That is, when the higher-order mode excitation of an optical fiber decreases, the transmission band becomes wider and its life span9 becomes wider, and when the ratio of higher-order mode excitation becomes less than a predetermined value, the effect of broadening the transmission band almost disappears.

Therefore, in order to use an optical fiber at its maximum transmission band, it is necessary to adjust the incidence conditions and suppress the amount of higher-order mode excitation.

Prior Art and Problems However, conventional light sources for optical communication directly input light from an LD, 9, or LED element into an optical fiber via a lens. Therefore, it is not possible to control the conditions of incidence on the optical fiber, and there is a problem in that such a conventional method cannot be used to take advantage of the broadband properties of the optical fiber.

OBJECTS OF THE INVENTION An object of the present invention is to control the amount of excitation of higher-order modes, optimize the amount of incident light, and bring the optical fiber into the maximum transmission band state by providing an incident condition adjustment mechanism between the optical fiber and the light emitting element. It is to be used in.

According to the present invention, in a light source for optical communication in which light from a light emitting element is focused by a lens and made to enter an optical fiber, the light is transmitted between the focusing lens and the end of the optical fiber. A light source for optical communication is provided, which is characterized by being provided with a fiber incidence condition adjustment mechanism. □ In the above light source, it is preferable that the incident condition adjusting mechanism is formed by a pinhole or an incident condition adjusting fiber.

Embodiments of the Invention The present invention will now be described by way of embodiments with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a first embodiment of a light source for optical communication according to the present invention.

The light source 1 for optical communication is constructed by installing a pinhole 13 between lenses 11 and 12 arranged in front of a light emitting element 14, and the light incident from the light source 1 is transmitted via an optical fiber 15. .

The light emitting element 14 is formed from an LD or an LED. The lens 11 converts the light from the light emitting element 14 into a beam P parallel to the center line C. The pinhole 13 adjusts the parallel beam P. The lens 12 condenses a parallel beam whose incident amount is adjusted through a pinhole 13 and makes it enter an optical fiber 15 . Note that the ends of the light emitting element 14 and the optical fiber 15 are respectively arranged at the focal point of the lens 11.12.

The operation of the optical communication light source 1 having the above configuration will be described below.

After the light emitted from the light emitting element 14 enters the lens 11 as shown by the arrow, it becomes a parallel beam P and passes through the pinhole 1.
Collision with 3. The colliding beam has 130 pinholes and 1 hole.
31 and enters the lens 12. Therefore, between the pinhole 13 and the lens 120, the amount of incident light beam decreases as the incident angle between the walls A and B surrounded by the broken line and the solid line increases.

The light beam adjusted in this manner is collected by the lens 12 and enters the optical fiber 151C. This allows the NA of incidence on the optical fiber 15 to be adjusted.

FIG. 2 is a diagram showing the relationship between @transmission band f and attenuation amount d when the light source according to the present invention is used.

The solid line in FIG. 2 shows the transmission band f of a GI7 eyeglass having a length of 1.2 (km), measured using an LD light source with a wavelength of 1.3 [μm]. The input NA is set to 0 by the pinhole 13.
．． It was adjusted to 14. The NA of the optical fiber 15 is 0.21.

On the other hand, the broken line is a diagram of the transmission band measured by a conventional light source that is directly incident on the optical fiber.

The 6 dB transmission band is 800 (MHz
) In the conventional light source, it is 450 (MHz).

FIG. 3 shows a second embodiment of the light source of the present invention, in which an incident conditional clause fiber 16 is inserted between the lens 11 and the optical fiber 15. In this case, the NA of the adjusting fiber 16
It is sufficient to use an IL optical fiber having the same NA as the IL optical fiber 15 and the same or smaller core diameter than the fiber 15, and this configuration also makes it possible to reduce the suborder mode excitation scene.

Effects of the Invention In accordance with the above, according to the present invention, the amount of high-order mode excitation can be reduced by providing an incident condition adjustment mechanism, so that the optical 7-eyeper can be operated in the maximum transmission band state under the optimum incident sight. can be used.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the light source of the present invention, FIG. 2 is a diagram illustrating the effects of the present invention, and FIG. 3 is a block diagram showing a second embodiment of the present invention. 1... Light source for optical communication according to the present invention, 11.12...
Lens, 13... Pinhole, 14...46 Optical element, 15... Optical fiber.

Claims (1)

[Scope of Claims] 1. In a light source for optical communication in which light from a light emitting element is focused by a lens and made to enter an optical fiber, conditions for entering the optical fiber between the focusing lens and the end of the optical fiber are provided. A light source for optical communication, characterized in that it is provided with an adjustment device (14). 2. A light source for optical communication according to claim 1, wherein the incident condition adjustment mechanism is formed by a pinhole. 3. 2. The light source for optical communication according to claim 1, wherein the incident condition adjusting mechanism is formed of an incident condition adjusting fiber having a core diameter that is the same as or smaller than that of the optical fiber.