JPS63181389A - Semiconductor module - Google Patents

Abstract

PURPOSE:To make it possible to realize high isolation under wide-ranging environmental conditions and to contrive to be able to control sufficiently both power consumption and the volume of the title semiconductor module by controlling temperatures of a semiconductor laser and a Faraday rotor in an airtight container. CONSTITUTION:An airtight container 21 provided with a cylindrical part 21a at its front part is blocked its upper part with a cover 22 and its front part with a transparent glass 23 and is held in an airtight state and a temperature control element 24 is arranged in its interior. A semiconductor laser 25, a photo diode 26 for monitor, a sphere-tipped rod lens 27, a permanent magnet 28 and a Faraday rotor 29 are arranged on the element 24 and a polarization isolation element 31 and an optical fiber terminal 33 are respectively arranged in the cylindrical part 21a and on the front end of the cylindrical part 21a. By causing the element 24 to hold the laser 25 and the rotor 29 thereon at a constant temperature in such a way, with the problem of temperature characteristics of the rotor 29 solved, a problem that the oscillation waveform of the laser 25 is changed by temperature can be also solved. Therefore, the wavelength dependence of the rotor 29 can be also indirectly relaxed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor module that is a light source for optical fiber communication, and more particularly to a semiconductor module incorporating an optical isolator.

[Conventional technology]

A conventional semiconductor module of this type with a built-in isolator is shown in FIG. In FIG. 4, a spherical tip lens 2 is fixed to the center of a housing 1 which has holes in the front and rear. A semiconductor module including a semiconductor laser 4, a monitor photodiode 5, a window glass 6, etc. housed in an airtight container 3 is housed in a hole on the rear side of the housing 1.

An optical isolator consisting of a Faraday rotator 8 within a permanent magnet 7, a polarization separation element 9, etc. is housed in a hole on the front side of the casing 1. An optical fiber 1 is installed at the front end of the housing 1.
An optical fiber terminal 12 having 1 at the center is fixed. The light from the semiconductor laser 4 of the semiconductor module having the optical isolator configured in this manner is prevented from being reflected toward the semiconductor laser 4 by the optical isolator provided between the semiconductor laser 4 and the optical fiber terminal 12. emits laser light. However, a semiconductor module having this type of optical isolator does not have a built-in temperature control element within the housing 1.

[Problem that the invention seeks to solve]

Due to the characteristics of the material, the Faraday rotation angle of the Faraday rotator changes depending on the surrounding temperature and the wavelength of the light used, so it achieves high isolation over the wide temperature and wavelength range required for optical communication light sources. The problem was that I couldn't do it.

Taking yttrium-iron-garnet (YIG), a typical material used for optical isolators in the ultrasonic band, as an example, the Faraday rotation angle is 10, 12 with respect to the wavelength.
in the proportion of [%·nm-') of 3 and with respect to temperature-
It changes at a rate of 0,088 [%·'C-').

The range required for optical communication light sources is, for example, 11 at temperature T.
0~60°C (25±35°C), 1290~ at wavelength λ
1230 (1310±20nm) and change amount ΔT depending on temperature
= 35° C. For one wavelength, the amount of change Δλ is generally ±20 nm. Since the center value of the Faraday rotation angle used in the optical isolator is 45°, the Faraday rotation angle θF at a temperature change ΔT = ±35°C is calculated as follows: ΔθF = -0,088÷100X45X (± 35
) changes by 1.4 degrees on ζ. Similarly, with a wavelength change of Δλ=±20 nm, the Faraday rotation angle is ΔθF = −0,123X45 X (±20)÷1
Changes by 00ζ±1.1deg. The theoretical value of the isolation of the optical isolator is given by the following equation.

l5olation = −IQ xlog (sin
21ΔθFl) [d B) Therefore, ΔT=±35°C temperature change and Δλ=20
By changing the wavelength in nm, the isolation changes from infinity to 32 dB and 34 dB, respectively.

Although the above description deals with temperature changes and wavelength changes separately, it becomes more complicated if both are taken into consideration at the same time.

Figure 5 shows the usage temperature and wavelength range (-10 to 60°C, 12
90 to 1330 nm). As is clear from this, the isolation that can be achieved within the usage range of the isolator is 25 dB.
Therefore, it is not possible to achieve isolation of 30 dB or more.

In this example, we have described the case of using YIG, but even with garnet films of various compositions, which have been actively researched recently, a film with less temperature/wavelength dependence than YIG has not been realized, and this poses a practical problem. It remains as it is.

An object of the present invention is to provide a semiconductor module having an optical isolator that solves the problem of data and temperature dependence of the two problems of wavelength and temperature dependence of Faraday rotation angle.

[Means for solving problems]

A semiconductor module of the present invention includes a semiconductor laser, at least one lens, a Faraday rotator/permanent magnet,
In a semiconductor module composed of an isolator consisting of a polarization separation element and a temperature control element, at least the semiconductor laser and the Faraday rotator are arranged on the temperature control element in an airtight container, and the semiconductor laser and the Faraday rotator are arranged on the temperature control element. The temperature is controlled to a constant temperature.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a longitudinal sectional side view of a semiconductor module showing an embodiment of the present invention. The airtight container 21, which has a cylindrical portion 21a at the front, is made airtight by closing the upper part with a lid 22 and the front part with a transparent glass 23. Inside the airtight container 21, a temperature control element 24 made of a Peltier element is arranged.

On this temperature control element 24, a semiconductor laser 25, a monitoring photodiode 26, a spherical rod lens 27,
A permanent magnet 28 and a Faraday rotator 29 are respectively arranged. A polarization separation element 31 is provided inside the cylindrical portion 21a.
However, optical fiber terminals 33 each having an optical fiber 32 are arranged at the front end of the cylindrical portion 21a. Here, as the Faraday rotator 29, a bismuth-substituted garnet film is used.

Rod lens 27, permanent magnet 28, Faraday rotator 2
9 are all fixed with metallized solder, so there is no need to use an adhesive that has a problem of outgassing inside the airtight container 21.

In the case of the embodiment shown in FIG. 1, the optical isolator includes a semiconductor laser 25 serving as a polarizing element, a permanent magnet 28, a Faraday rotator 29, and a polarization separation element 31 (analyzer) located outside the airtight container 21. It consists of As the polarization separation element 31, a rutile polarizing plate is used in this embodiment.

By maintaining the semiconductor laser 25 and the Faraday rotator 29 at a constant temperature by the temperature control element 24 in this way,
In addition to solving the temperature characteristic problem of the Faraday rotator 29, it is also possible to solve the problem that the oscillation wavelength of the semiconductor laser 25 changes depending on the temperature, so the problem of the wavelength dependence of the Faraday rotator 29 can be indirectly solved. It also has a relaxing effect.

Such an effect can also be achieved by controlling the temperature of the entire conventional semiconductor module that does not have a built-in temperature control element as explained in Fig. 4, but in that case, the power consumption will increase due to the large heat capacity l. , and the heat dissipation structure also needs to be large, so it is not practical.

FIG. 2 shows a semiconductor module according to another embodiment of the invention. The difference between this semiconductor module and the semiconductor module shown in FIG. 1 is that in this embodiment, a permanent magnet 28 and two polarization separation elements (polarizer and analyzer) 34 and 35 are fixed with adhesive. The entire optical isolator consisting of the Faraday rotator 29 is enclosed in an airtight container 37 having a pair of glass windows 36 at the front and rear, and this airtight container 37 is placed above the temperature control element 24.

By configuring the semiconductor module in this manner, the adhesive used in the optical isolator is prevented from damaging the semiconductor laser 25 due to outgas.

FIG. 3 shows a semiconductor module according to yet another embodiment of the invention. Inside an airtight container 21 having a glass 23, a semiconductor laser 25 and a monitoring photodiode 26 are installed.
, the permanent magnet 28 and the Faraday rotator 29 are temperature controlled by a temperature control element 24. rod lens 27
is not temperature controlled, and the polarization separation element 31 is mounted at the end of the optical fiber terminal 33.

In the above embodiment, one rod lens 27 is used, but the invention is not necessarily limited to this.

Further, the Faraday rotator 29, the polarization separation element 31, and the temperature control element 24 may be other than those used in the embodiment. Further, as shown in the embodiment, the optical isolator is not necessarily integrated. Further, the number of temperature control elements 24 is not limited to one, and a plurality of temperature control elements 24 may be used.

〔Effect of the invention〕

As explained above, according to the present invention, by controlling the temperature of the semiconductor laser and the Faraday rotator in an airtight container, it is possible to achieve high isolation under a wide range of environmental conditions. This semiconductor module has great practical effects because both power consumption and volume can be sufficiently suppressed. In particular, distributed feedback semiconductor radars, which have been attracting attention recently, require high isolation, so the effect of the present invention in putting this semiconductor module into practical use is very large.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional side view of a semiconductor module showing a first embodiment of the invention, FIG. 2 is a longitudinal sectional side view of a semiconductor module showing a second embodiment of the invention, and FIG. 3 is a longitudinal sectional side view of a semiconductor module showing a second embodiment of the invention. FIG. 4 is a vertical side view of a semiconductor module showing an example of a conventional semiconductor module; FIG.
The figure shows the relationship between isolation, operating temperature, and wavelength range for yttrium, iron, and garnet. 21... Airtight container, 24... Temperature control element, 25... Semiconductor laser, 27... Lens, 28... Permanent magnet, 29...Faraday rotator. Applicant: NEC Corporation Representative

Claims (1)

[Claims] A semiconductor module comprising a semiconductor laser, at least one lens, a Faraday rotator/permanent magnet, an isolator comprising a polarization separation element, and a temperature control element, at least the semiconductor laser and the Faraday rotator. A semiconductor module characterized in that a semiconductor laser and a Faraday rotator are temperature-controlled by being placed on a temperature control element in an airtight container.