JP2518027B2 - Semiconductor laser module - Google Patents

Description

The present invention relates to a semiconductor laser module for optical communication, and more particularly to a DFB-LD (Distributed feedback laser diode).
The present invention relates to a semiconductor laser module suitable for high speed transmission using a laser or the like.

[Conventional technology]

2. Description of the Related Art Conventionally, as a semiconductor laser module of this type, for example, as shown in FIG. 2, an optical isolator 4 is interposed between a semiconductor laser 1 and an optical fiber 3 on which light 2 emitted from the semiconductor laser 1 is incident. Known configurations are known. A lens 5 for converting the emitted light 2 into a parallel beam is interposed between the semiconductor laser 1 and the optical isolator 4, and a condenser lens 6 is provided between the optical isolator 4 and the optical fiber 3. Is intervening.

The emitted light 2 from the semiconductor laser 1 is converted into a parallel beam by the lens 5 and is incident on the optical isolator 4, and the emitted light from the optical isolator 4 is condensed by the lens 6 and coupled to the optical fiber 3.

The optical isolator 4 is an optical nonreciprocal element, has a function of preventing return light from the optical fiber 3 from reentering the semiconductor laser 1, and is a semiconductor for high-speed transmission for the purpose of stabilizing laser oscillation. It is widely used in laser modules.

[Problems to be Solved by the Invention]

The conventional semiconductor laser module described above can be miniaturized because it has the optical isolator 4 built-in, and is easy to handle. However, after being integrally assembled, the semiconductor laser module is separated between the semiconductor laser 1 and the optical isolator 4. The optical signal could not be extracted and the optical power could not be measured. Therefore, there is a disadvantage that the isolation (ratio of insertion loss in the forward direction and the insertion loss in the reverse direction), which is a basic characteristic of the optical isolator 4, cannot be measured after the semiconductor laser module is assembled.

As a semiconductor laser module used for advanced optical transmission such as coherent transmission, high isolation of about 40 dB is required, and determination of the actual value of isolation is essential. Conventionally, the ability of isolation cannot be determined unless the transmission characteristics are measured by incorporating it into the device after manufacturing the semiconductor laser module. Therefore, select one from many semiconductor laser modules that matches the required characteristics. Spends a lot of time on it.

The present invention has been made in view of such circumstances, and a semiconductor laser module in which the characteristics of the optical isolator can be confirmed even after the module is assembled, the transmission characteristics need not be measured by incorporating the device, and the time required for selection can be shortened. The purpose is to provide.

[Means for solving the problem]

A semiconductor laser module according to the present invention comprises, between a semiconductor laser and an optical isolator, a semitransparent mirror for extracting a part of the light from the semiconductor laser to the outside and a part of the light from the optical isolator to the outside. The above-mentioned object is achieved by providing a light extraction mechanism so that the isolation determination can be performed based on the optical signal extracted between the semiconductor laser and the optical isolator even after the module is assembled.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

As shown in FIG. 1, an optical isolator 14 is interposed between a semiconductor laser 11 and an optical fiber 13 on which light 12 emitted from the semiconductor laser 11 is incident. Semiconductor laser
A lens 15 for converting the emitted light 12 into a parallel beam is interposed between the optical isolator 14 and the optical isolator 14, and a condenser lens 16 is interposed between the optical isolator 14 and the optical fiber 13. There is.

In this structure, the semi-transparent mirror 17 is arranged between the optical isolator 14 and the lens 15 on the semiconductor lens 11 side of the optical isolator 14 in such a manner that the optical isolator 14 is inclined at a constant angle with respect to the optical path of the laser light.
Is provided.

Then, the emitted light 12 from the semiconductor laser 11 is converted into a parallel beam, then passes through the semitransparent mirror 17, and enters the optical isolator 14. After this, the light is emitted from the optical isolator 14 and is condensed by the lens 16 and coupled to the optical fiber 13. In this case, the emitted light 12 from the semiconductor laser 11
Is partially reflected by the surface of the semitransparent mirror 17, and the reflected light 18 is extracted to the outside.

Therefore, when measuring the isolation of the optical isolator 14, first, the optical power P ₁ of the reflected light 18 by the semitransparent mirror 17 is measured, and this optical power P ₁ and the tip surface of the optical fiber 13 are measured.
The insertion power L ₁ in the forward direction is obtained by comparing with the optical power P ₂ of the emitted light 19 from 13a. Next, the tip surface 13 of the optical fiber 13
A light beam 20 from another semiconductor laser (not shown) is incident on the a side in the opposite direction to the above. The optical power P ₃ of this light beam 20 and the optical power P ₄ of the reflected light 21 on the surface of the semitransparent mirror 17 after passing the optical isolator 14 of this light beam 20 are measured and compared, and the insertion loss in the opposite direction is measured. Find L ₂ . The isolation of the optical isolator 14 may be obtained from the ratio of the insertion losses L ₁ and L ₂ thus obtained.

According to the configuration of the above embodiment, since the characteristics of the optical isolator 14 can be confirmed even after the semiconductor laser module is assembled, the selection of the semiconductor laser module having the isolation required for the system to be applied can be incorporated in the device. It is possible before. Therefore, unlike the conventional semiconductor laser module that has to rely on the measurement of the transmission characteristics after being incorporated in the device, the characteristics can be determined on a module-by-module basis to facilitate selection in a short time.

〔The invention's effect〕

As described above, according to the semiconductor laser module of the present invention, it is possible to determine the characteristics of the optical isolator before the device is assembled into the device in the assembled state of the module, and it is possible to reduce the time required for selection. .

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional example. 11 …… Semiconductor laser, 12 …… Emitting light, 13 …… Optical fiber, 14 …… Optical isolator, 17 …… Semi-transparent mirror.

Claims (1)

(57) [Claims] 1. A semiconductor laser module in which an optical isolator is interposed between a semiconductor laser and an optical fiber to which light emitted from the semiconductor laser is incident, wherein the semiconductor laser module is provided between the semiconductor laser and the optical isolator. A semiconductor laser module comprising a light extraction mechanism including a semitransparent mirror for extracting a part of light from the semiconductor laser to the outside and a part of light from the optical isolator to the outside.