JPS62188391A - Semiconductor laser diode module - Google Patents

Abstract

PURPOSE:To enable production of the prescribed output laser beam driving a semiconductor laser diode at the most suitable driving current point thereof by a method wherein an attenuating means is provided in an output laser beam producing path to attenuate a transmitting beam. CONSTITUTION:An attenuating means 102 to attenuate a transmitting beam is provided in an output laser beam producing path, and a semiconductor laser diode 101 is made to be driven at the most suitable driving current point thereof. For example, as optical fiber to construct pigtail fiber 3A, fibers having different attenuations per unit length are used, and moreover by changing length thereof, fiber having voluntarily different attenuation can be manufactured. Thereupon, by selecting fiber from preliminarily prepared pigtail fibers having various attenuations and using the fiber thereof, the desired attenuation can be bestowed. Accordingly, the prescribed output laser beam can be produced driving the semiconductor laser diode at the most suitable driving current point thereof even when the beam output characteristic of the semiconductor laser diode has dispersion.

Description

[Detailed Description of the Invention] [Summary] A semiconductor L in which light generated by a built-in semiconductor laser diode is outputted from a pigtail fiber.
In the D module, a predetermined output light can be extracted while driving the semiconductor laser diode at its optimum drive current point by providing an attenuation means in the output light extraction path to attenuate the transmitted light.

[Industrial application field]

The present invention relates to a semiconductor LD module that integrates a semiconductor laser diode (LD) and an output optical fiber,
In particular, the present invention relates to a semiconductor LD module that can obtain a predetermined optical output without adjusting the drive circuit.

Semiconductor LD modules are used in the field of optical communications as a source of optical signals sent to optical fibers, and therefore their optical output must be at a specified value, but usually due to various reasons. There are variations, and adjustments are required to match the specified values. It is desired that such adjustment work be as simple as possible in terms of both labor and cost.

[Conventional technology]

A conventional semiconductor LD module generally has a structure as shown in FIG. In the figure, reference numeral 1 denotes an LD chip, which emits light in response to a drive current from a drive circuit (not shown). Reference numeral 2 denotes a lens system that converges the light generated by the LD chip and inputs it into an optical fiber for output extraction, that is, a pigtail fiber 3. An optical connector 4 is provided at the output end of the pigtail fiber 3, and couples the optical output to a signal transmission optical fiber (not shown).

The main factor that determines the optical output characteristics of such a semiconductor LD module is the driving current (1
)-light output (L) characteristics, the coupling efficiency between the LD chip 1 and the pigtail fiber 3, and the optical loss of the pigtail fiber 3.

FIG. 7 explains the optical output characteristics of the LD chip, and as shown in the figure, the desired optical output PI is determined by the drive current In, and one drive current is a DC dark value current 1th.
and a pulsed modulation current IM.

Dark value current 1th and modulation current in LD chip ■9
It is inevitable that there will be some degree of variation in the value of . Therefore, conventionally, by adjusting the drive current source side, the dark value current value, the characteristics of the LD chip, and the LD
The modulation current is adjusted based on the modulation current versus optical output characteristic, which includes the coupling efficiency between the chip and the pigtail fiber, the loss of the bigtail fiber, etc., that is, the external differential efficiency (η), to obtain a constant optical output characteristic.

[Problem that the invention seeks to solve]

In the drive circuit for the semiconductor LD module, the DC current circuit for supplying the dark value current has a simple configuration, a small circuit scale, and the current value can be easily adjusted.

However, a pulse current circuit for supplying a modulated current is generally complicated and large in circuit scale, and it is difficult to adjust the current value. This becomes especially difficult when the pulse rate increases.

On the other hand, it is conceivable to make the optical output constant by keeping the modulation current value supplied from the drive circuit constant and changing the external differential efficiency in the semiconductor LD module. The light output in LD chips is gradually increasing with the advancement of technology. Therefore, if you use the LD chip at its optimum drive current value and attenuate its optical output in some way to obtain a constant optical output,
Although it is possible to simplify the adjustment of the drive circuit, thereby simplifying the circuit configuration and reducing the circuit scale, such a semiconductor LD module has not been proposed at all in the past.

[Means for solving problems]

In order to solve the problems of the prior art, the semiconductor LD module of the present invention has a basic configuration consisting of various means as shown in FIG.

A semiconductor laser diode 101 is driven by its optimum driving current to generate optical output.

102 is an attenuation means, which includes a semiconductor laser diode (
101) to produce output light.

[For production]

The semiconductor LD module of the present invention is equipped with an attenuation means to arbitrarily attenuate the optical output of the semiconductor laser diode, so even if there are variations in the optical output characteristics of the semiconductor laser diode, the semiconductor laser diode can be adjusted to its optimum driving current point. A predetermined optical output can be extracted while driving the device.

〔Example〕

FIG. 2 shows one embodiment of the present invention, and shows the sixth embodiment of the present invention.
The same parts as in the figure are indicated by the same numbers, and 3A is the pigtiled fiber in this example.

The pigtiled fiber 3A in FIG. 2 differs from the pigtiled fiber 3 shown in FIG. 6 in that it is an optical fiber with a large amount of attenuation. The pigtail fiber 3A can be manufactured by using optical fibers having different attenuation amounts per unit length, or by changing the length of the optical fibers having different attenuation amounts. Therefore, by selecting and using pigtail fibers having various attenuation amounts prepared in advance, it is possible to provide desired attenuation.

According to the embodiment shown in FIG. 2, the LD drive circuit only adjusts the dark value current value, and the modulation current value is
The most 'JI! The optical output of the semiconductor LD module can be easily adjusted to a specified value by adjusting the attenuation of the pigtail fiber 3A and changing the external differential efficiency while maintaining the drive current at the i drive current point. Simplify.

This means that it can be made smaller and easier to adjust, making the overall circuit size smaller and easier to handle.
The intended purpose is achieved.

As another example, the pigtail fiber 3A in FIG. 2 is constructed in advance from an optical fiber with a small attenuation per unit length, and a color center is created in the optical fiber by irradiating it with appropriate radiation during adjustment. may be caused to increase the amount of attenuation. In this case, there is an advantage that an arbitrary amount of attenuation can be continuously achieved by adjusting the radiation intensity, irradiation time, etc. to be irradiated.

FIG. 3 shows a second embodiment of the present invention,
The same parts as in FIG. 6 are designated by the same numbers, and 5 is a pressurizing device.

In the embodiment of FIG. 3, the amount of attenuation can be increased arbitrarily by applying pressure using the pressure device 5 to the pigtail fiber 3 passing through it. Therefore, with the embodiment shown in FIG. 3, the optical output can be adjusted to a specified value by arbitrarily changing the external differential efficiency, as in the other embodiments described above.

FIG. 4 shows a third embodiment of the present invention,
The same parts as in FIG. 6 are indicated by the same numbers, and 6 is an optical attenuator.

In the embodiment shown in FIG. 4, the light generated by the LD chip 1 is attenuated by passing through an optical attenuator 6 when it passes through the lens system 2 and enters the pigtail fiber 3. The optical attenuator 6 is made of a well-known structure such as an optical multilayer film, and can be manufactured with its attenuation value adjusted in advance to an arbitrary value. Therefore, it is possible to easily adjust the optical output of the semiconductor LD module to a specified value by preparing optical attenuators having various attenuation amounts in advance and selecting and using them to provide the desired attenuation. and the intended purpose is achieved.

FIG. 5 shows a fourth embodiment of the present invention,
The same parts as in FIG. 6 are indicated by the same numbers, and 7 and 8 are polarizing plates, respectively.

In the embodiment shown in FIG. 5, by mutually rotating the polarization directions of the polarizing plates 7.8, a wide range of attenuation can be achieved, from approximately 0 when the two polarization directions are parallel to almost infinite when they are orthogonal. can be realized. Therefore, when adjusting a semiconductor LD module, for example, by fixing one polarizing plate 7 and rotating the other polarizing plate 8 in a direction perpendicular to the optical axis, it is possible to give an arbitrary amount of attenuation to the optical output. Therefore, the optical output of the semiconductor LD module can be easily adjusted to a predetermined value.

Further, the polarizing plates can not only be arranged at both ends of the pigtail fiber 3, but also can be arranged overlappingly on one side.

〔Effect of the invention〕

As explained above, according to the present invention, an attenuation means is provided in the optical output extraction path of the semiconductor laser diode to arbitrarily attenuate the transmitted light, so that even if there are variations in the optical output characteristics of the semiconductor laser diode, However, while driving the semiconductor laser diode at its optimum driving point,
A predetermined optical output can be extracted, and therefore the configuration of the drive circuit can be simplified and the scale can be reduced, and adjustment can be made simple. Therefore, according to the present invention, it is possible to reduce the circuit scale as a whole and to facilitate adjustment, thereby reducing labor and cost.

[Brief explanation of drawings]

Fig. 1 shows the basic configuration of the present invention, Figs. 2 to 5 each show an embodiment of the present invention, and Fig. 2 shows how the desired attenuation amount is achieved by the attenuation of the pigtail fiber itself. Figure 3 shows the case when pressure is applied to the pigtail fiber to increase the attenuation, Figure 4 shows the case when an optical attenuator is used, Figure 5 shows the case when two polarizing plates are used, and Figure 6 shows the case when two polarizing plates are used. 7 is a diagram showing a conventional semiconductor LD module, and FIG. 7 is a diagram showing the optical output characteristics of the LD chip. 1... Laser diode (LD) chip 2... Lens system 3.3A... Pigtail fiber 4... Optical connector 5... Pressure device 6... Optical attenuator 7.8...・Polarizing plate patent applicant: Fujitsu Co., Ltd. Agent Patent attorney: Hisashi Tamamushi (1 other person)

Claims (5)

[Claims] (1) In a semiconductor LD module that includes a semiconductor laser diode (101) and extracts the light generated by the semiconductor laser diode (101) through an output light extraction path including a pigtail fiber, the output light extraction path includes attenuation means (
102) is provided, and the semiconductor laser diode (101
) is driven at its optimum drive current point. (2) The semiconductor LD module according to claim 1, wherein the attenuating means (102) comprises the pigtail fiber that attenuates light. (3) The semiconductor LD module according to claim 1, wherein the damping means (102) comprises pressurizing means for applying pressure to the pigtail fiber. (4) The semiconductor LD module according to claim 1, wherein the attenuation means (102) comprises an optical attenuator inserted in the output light extraction path. (5) The attenuation means (102) is comprised of two polarizing plates inserted in series in the output light extraction path and whose polarization directions can be mutually rotated. semiconductor LD module.