JPH10160984A - Optical fiber module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber module which prevents reflected return light from bringing harmful effects. SOLUTION: The optical fiber module M constituted by assembling a light emission source 20, an optical system 30, and an optical fiber 40 has the light emission source 20 and optical system 30 installed while slightly shifted from the transmission optical axis L1 of the optical fiber 40, and the signal light from the light emission source 20 is made incident obliquely on the optical fiber 40 through the optical system 30. Consequently, nearly none of reflected return light returns to the side of the light emission source 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber module for preventing adverse effects due to reflected return light.

[0002]

2. Description of the Related Art As is well known, a light emitting source (for example, a laser diode = LD) and an optical system (for example, a spherical lens) are used.
In the case of the optical transmission system of the optical fiber module in which the optical fiber and the optical fiber are assembled, the light emitted from the light emitting source may return to the light emitting source side as reflected return light from various parts of the optical transmission system. is there.

[0005] The presence of this reflected return light causes inconveniences such as making the operation of the LD of the light emitting source unstable and appearing as noise in the emitted light. For this reason, conventionally, an optical isolator or the like is incorporated as a measure against general reflected return light.

[0004]

However, the above-mentioned conventional optical isolator has a rather complicated structure using a Faraday rotator, a mode converter, and the like, and is considerably expensive. For this reason, an optical fiber module using a 1.3 μm or 1.55 μm LD for high-speed, large-capacity communication over long distances is cost-effective, but has a short wavelength (0.8 μm) for short distances. An optical fiber module using an LD has a problem that it is too expensive and sometimes accounts for more than half of the total cost of the module.

The present invention has been made in view of such a conventional situation, and the positions of the light emitting source and the optical system are previously set at positions slightly shifted from the transmission optical axis of the optical fiber. It is an object of the present invention to provide an optical fiber module having a simple structure, in which reflected return light from the light source does not return to the light emitting source side.

[0006]

According to the present invention, there is provided an optical fiber module in which a light emitting source, an optical system, and an optical fiber are assembled, wherein the light emitting source and the optical fiber are arranged with respect to the transmission optical axis of the optical fiber. The optical fiber module is provided at a position slightly shifted from the optical system, and the signal light from the light emitting source is incident on the optical fiber from an oblique direction through the optical system.

[0007]

FIG. 1 shows an entire embodiment of an optical fiber module according to the present invention. In this optical fiber module M, reference numeral 10 denotes a housing made of plastic or the like, and reference numeral 20 denotes L as a light emitting source.
D and 30 are spherical lenses as an optical system, 40 is an optical fiber forming an optical transmission path, and L1 is a transmission optical axis of the optical fiber 40.

The housing 10 is provided with a connection hole 11 for an optical fiber on one side (right side in the figure), to which an optical fiber 40 is connected via a ferrule 41 made of ceramics, for example. is there. As a result, the position of the core portion (not shown) of the optical fiber 40 is determined substantially at the center portion of the connection hole 11. This connection hole 11
A lens holder 50 with a position adjusting mechanism for a spherical lens is provided near the central enlarged portion of the internal through hole of the housing 10 communicating with the housing 10, and the spherical lens 30 is mounted on the lens holder 50. is there. A light-emitting source fixing clamp having a light-emitting source holder 70 with a position adjusting mechanism for a light-emitting source is provided near the front end (right side in the drawing) of the housing 10 at the enlarged-diameter opening on the other side (left side in the figure). 60 is attached by screwing or the like.

The lens holder 50 with the position adjusting mechanism
Although not particularly limited, for example, as is clear from the enlarged view of FIG. 2, a slide frame 51 that can freely move in the up, down, left, and right directions with respect to the transmission optical axis L1 of the optical fiber 40, and the spherical lens 30 are provided. A free holder portion 52 that is fixed and slidably held in the slide frame 51 so that the inclination of the ball lens 30 can be adjusted.
Consists of As is apparent from the enlarged view of FIG. 2, the light emitting source holder 70 also has the slide frame 71 that can freely move in the up, down, left, and right directions and the LD 20, and is slidably inserted into the slide frame 71. It comprises a free holder part 72 that can be held and adjust the inclination of the LD 20.

Therefore, the actual LD 20 and the spherical lens 3
In setting the positioning of 0, while driving the LD 20 to emit light, a power meter is connected to the optical fiber 40 side, and the lens holder 50 with the position adjusting mechanism and the light emitting source holder 70 with the position adjusting mechanism are operated. Optical fiber 4
LD 20 and spherical lens 30 with respect to transmission optical axis L1 of zero.
Is shifted in a suitable direction, a point where the light incident power is maximized is found, and as shown in FIG. 2, they are arranged on the outgoing optical axis L2. As a result, the transmission optical axis L1 of the optical fiber 40 intersects obliquely from the oblique direction, and the L
D20 and the ball lens 30 are arranged. To fix the position, it is preferable to apply a UV adhesive or the like to each sliding contact surface and then irradiate with UV light to cure.

In the case of the optical fiber module M of the present invention having such a configuration, since the outgoing optical axis L2 of the LD 20 and the spherical lens 30 and the transmission optical axis L1 of the optical fiber 40 are displaced, the light is reflected in principle. Return light hardly returns to the LD 20 side.

Incidentally, in the optical fiber module M of the present invention having the above-mentioned configuration, as the LD, a relaxation oscillation type LD for communication (emission wavelength = 0.78 μm, emission output = maximum 5 m)
W) and a spherical lens having an outer diameter of 1.5
When various tests were performed using a lens having a refractive index of 1.517 mm and a lens having a refractive index of 1.517, the moving amount (deviation amount) of the spherical lens was L
When about 200 μm in the horizontal direction with respect to the active layer of D, the amount of light incident on the optical fiber and the amount of reflected return light from the optical fiber are moderately balanced, and an appropriate optical transmission system having no practical problem can be constructed. I understood. Here, the shifting direction may be a direction perpendicular to the active layer of the LD, but according to the above experimental results, the movement in the horizontal direction was more effective.

The light-emitting source of the present invention is not limited to an LD, and a light-emitting diode can be used for a short distance. Further, as an optical system, in addition to the spherical lens 30, if necessary, as shown by the chain line in FIG. 2, a focus type rod lens 80 can be provided.

In the above embodiment, the position adjustment of the LD 20 and the spherical lens 30 is performed by attaching the lens holder 50 with the position adjustment mechanism and the light emitting source holder 70 with the position adjustment mechanism. , 70 are omitted, and the LD 20 and the ball lens 30 are shifted to predetermined portions.
It can also be fixed directly with an adhesive or the like. In particular, after sufficient data is obtained from the experimental results as described above, it is possible to sufficiently cope with the fixation by direct bonding.

[0015]

As is apparent from the above description, the optical fiber module according to the present invention has the following excellent effects. (1) Since the emission optical axis of the light emitting source and the optical system is deviated from the transmission optical axis of the optical fiber, reflected return light hardly returns to the light emitting source side in principle. Therefore, inconveniences such as abnormal amplification due to external resonance in the light emitting source are eliminated, and stable operation can be ensured. In addition, an improvement in the durability of the light emitting source can be expected. (2) Since an expensive device such as an optical isolator does not need to be used, an inexpensive module can be provided. In particular, in an optical fiber module using a short-wavelength LD for a short distance, the cost can be significantly reduced as a practical module. (3) Since the number of assembling steps is almost the same as the conventional one, there is no problem such as a special increase in working cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of an optical fiber module according to the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part of FIG.

[Explanation of symbols]

 Reference Signs List 10 housing 20 light emitting source 30 optical system 40 optical fiber 50 lens holder with position adjusting mechanism 60 light emitting source fixing clamp 70 light emitting source holder with position adjusting mechanism M optical fiber module L1 transmission optical axis L2 emission optical axis

Claims (2)

[Claims] 1. An optical fiber module in which a light emitting source, an optical system, and an optical fiber are assembled, wherein the light emitting source and the optical system are installed at positions slightly shifted with respect to a transmission optical axis of the optical fiber, An optical fiber module, wherein signal light from the light emitting source is incident on the optical fiber from an oblique direction through an optical system. 2. The optical fiber module according to claim 1, wherein said light emitting source is a laser diode, and said optical system is a spherical lens.