JPS58147186A - Laser diode module - Google Patents

Abstract

PURPOSE:To suppress the reincident of an emitted light to a laser diode by the reflection on the end face of an optical fiber by fixing a rod lens on the end face of the optical fiber and mounting a matching agent at the contact. CONSTITUTION:The light emitted from a laser diode chip 1a alters its optical path via a rod lens 10 and condensed at one point (g) of the end face of the rod lens. Since the end face of the optical fiber 4 is contacted directly with the focusing point (g) and a matching agent 11 is mounted, the light condensed at the point (g) is not reflected by Fresnel but coupled to the optical fiber 4. A transparent liquid or solid solution which is substantially equal to the optical fiber 4 in the refractive index is considered as the agent 11, such as a silicone oil.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser diode used for optical fiber transmission, and a laser diode module having a built-in optical fiber for transmitting light emitted from the laser diode.

Conventionally, there has been a laser diode module shown in FIG. In the figure, (1) is a laser diode, (2) is a rod lens, (3) is a case, +4) is an optical fiber, (5) is an optical fiber jacket, +61
is an optical fiber protection sleeve, (7) is a protective member, (8)
is a rubber hood. FIG. 2 is an enlarged view of only the optical system of the laser diode module shown in FIG. 1. In the figure, a is a laser diode chip, (
2) is a rod lens, (4) is an optical fiber, (9) is a ray trajectory, and f is an imaging point.

In the V-the diode module shown in FIG.

The light emitted from the laser diode chip a has its optical path changed by a Rollado lens (2) and is focused at an imaging point f. The imaging point f is adjusted so that the end face of the optical fiber (4) is located. Note that the light emitted from the laser diode chip a at this time is shown as a ray trajectory (9).

Since the conventional laser diode module is configured as described above, the light emitted from the laser diode chip a undergoes Fresnel reflection that occurs at the end face of the optical fiber (4), so that a part of the emitted light returns to the laser diode chip a. The disadvantage is that the operating characteristics deteriorate due to the self-coupling phenomenon. Characteristic deterioration includes deterioration in linearity of optical output, increase in noise, wavelength shift, and imbalance in the ratio of front light output to back light output.

This invention, which was sometimes a big problem in analog transmission, was made to eliminate the above-mentioned drawbacks of the conventional ones. The rod lens is fixed in the case, adjusted so that the light emitted from the laser diode is focused on the end face of the optical fiber, and a matching agent is attached to the contact point between the rod lens and the optical fiber. It is an object of the present invention to provide a laser diode module in which light emitted from the diode is prevented from being reflected by the end face of the optical fiber and re-entering the laser diode.

An embodiment of the present invention will be described below. FIG. 8 is a structural sectional view of a laser diode module according to the present invention. In Fig. 8, (1) is the laser diode, (3) is the case, (4) is the optical fiber, (51i optical fiber jacket, +61 is the optical fiber protection sleeve, (7) is the maintenance member, (8) is a rubber hood, Ql is a rod lens, and aυ is a matching agent that has the same refractive index as the optical fiber (4). In Figure 4, only the optical system of the laser diode tomo seal in Figure 8 is extracted and enlarged. The figure shown below is shown below.

In Fig. 4, a indicates a laser diode chip.

On the other hand, the ray locus 1g is the imaging point. The light emitted from the laser diode chip changes its optical path by the rod lens Q(I) and is focused on one point on the end face of the road lens. This point is called the imaging point g. Assuming that the focusing constant is human, the refractive index on the optical axis is No, and the pitch number is P, the gap of 1° between the laser diode chip a and the rod lens aI is expressed by equation (11).

1o = -No/;j tan 2 x p
(tllo≧0, so for equation (1) to have a solution, -(2n-1)≦p≦T n (n=1.2.8
．． -) (Need to satisfy 21.

2 (When the relational expression 11 (2) is satisfied, the light emitted from the laser diode chip a is focused at the imaging point g.The end face of the optical fiber (4) is directly connected to the liquid at the imaging point g. Since the matching agent I is attached to the contact point, the light focused at the imaging point g4C is coupled to the optical fiber (4) without Fresnel reflection.As the matching agent αυ, the refractive index is Transparent liquids or solid solutions that are almost the same as the optical fiber (4) can be considered, such as silicone oil, etc.The laser diode chip a used in Figures 2 and 4 may be used in other figures. This is a term used for convenience when enlarging the laser diode (1) used, and they have the same function.

As explained above, according to the present invention, the light emitted from the laser diode undergoes Fresnel reflection at the end face of the optical fiber and is prevented from re-entering the laser diode, resulting in improved operating characteristics and extremely practical effects. It's a big deal.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of a conventional laser diode module, Fig. 2 is a diagram showing the optical system of the laser diode module of Fig. 1, and Fig. 8 is a laser diode module with anti-reflection measures according to the present invention. 4 is a side sectional view of
This is a diagram showing the optical system of the laser diode module in Figure 9, (1) is the laser diode, (2) is the rod lens, (3j is the case, (4) is the optical fiber. +51 Fi optical fiber jacket), +61 is an optical fiber sleeve, (7) is a protective member, and (8) is a rubber hood. (9) is a ray locus, aO is a rod lens, aυ is a matching agent, and 03 is a ray locus. Note that in FIG. 1, the same or corresponding parts are designated by the same reference numerals. Agent Shin Kuzuno - Figure 1 Figure 2 Figure 3 Figure 4

Claims (2)

[Claims] (1) In a laser diode module incorporating a laser diode and an optical fiber to which the emitted light of the laser diode is optically coupled, a rod lens is provided between the laser diode and the laser diode so that liquid is applied directly to the end face of the optical fiber. By adjusting the gap between the laser diode and the rod lens or the length of the rod lens, after the light emitted from the laser diode enters one end surface of the rod lens,
A laser diode module characterized in that it is configured to form an image within the other end surface. (2) A surface of the rod lens that is in contact with the optical fiber is coated with a mass having substantially the same refractive index as the original fiber, and a mass and a tinging agent. A laser diode module according to claim 11, characterized in that a transparent liquid or solid is provided.