JPH0273684A - Semiconductor laser module - Google Patents

Abstract

PURPOSE:To cut down circuit scale and to superimpose an auxiliary signal on a main signal by applying auxiliary signal voltage to a primary electric optical element so as to modulate the phase of a laser beam. CONSTITUTION:An intensity-modulated laser beam from a semiconductor laser 10 is convered into parallel light by a first lens 11 and the phase is modulated through a polarizer 12 according to the auxiliary signal from an auxiliary signal voltage source 14 by a primary electron optical element 13 wherein the changes of refractive indexes of two kinds of light waves by double refraction can be obtained to the change of a low frequency electric field. The outgoing light of this element 13 is condensed with the second lens 13 and is emitted through an optical fiber 16. Hereby, there is no necessity of providing an electric circuit to superimpose an auxiliary signal at the outside, and the scale of circuit can be cut down and the auxiliary signal can be superimposed on the main signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to optical fiber communications, and particularly to a semiconductor laser module that converts electrical signals into optical signals.

[Conventional technology]

Conventionally, high-speed P using this type of semiconductor laser module
In image transmission systems using CM or analog direct modulation, as shown in Figure 2, the emitted light from the semiconductor laser l is
After being converted into parallel light by a lens 2, it passes through an optical isolator consisting of a polarizer 3, a Faraday rotator 4, and an analyzer 5, and is focused by a second lens 6 and coupled to an optical fiber 7. It was designed to prevent reflected waves from re-entering.

[Problem to be solved by the invention]

However, in the semiconductor laser module configured as described above, intensity modulation is determined by the semiconductor laser drive current, so when superimposing an auxiliary signal on the main signal, it is difficult to use the conventional semiconductor laser module. In this case, there was no means available, and an electric circuit for superimposing the auxiliary signal had to be constructed externally, which had the disadvantage of increasing the circuit scale.

The object of the present invention has been made in view of the above-mentioned drawbacks.
An object of the present invention is to provide a semiconductor laser module with a reduced circuit scale.

Means for Solving the Problem] In order to achieve the above-mentioned object, the present invention provides a semiconductor laser and an if for converting the emitted light of the semiconductor laser into manual light.
A primary electro-optical element that obtains changes in the refractive index of two types of light waves: birefringence due to changes in the electric field at a low frequency compared to the applied light waves; In a semiconductor laser module in which a second lens for condensing light emitted from an optical element and an optical fiber are sequentially arranged, an auxiliary signal voltage source is applied to the primary electro-optical element, and the auxiliary signal is added to the main signal as phase modulation. The structure is such that the images are superimposed on each other.

Two effects] As described above, the semiconductor laser module according to the present invention has the following effects:
If an auxiliary signal voltage is applied to the primary electro-optical element and the phase of the semiconductor laser output light is controlled to produce phase modulated light, the auxiliary signal can be superimposed on the main signal (intensity modulated signal by the drive current).

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment of a semiconductor laser module according to the present invention. The semiconductor laser module of this embodiment includes a semiconductor laser 10, and is arranged in front of this semiconductor laser IO. A first lens 11 that converts the emitted light of the P-conductor laser 10 into parallel light, a polarizer 12 placed in front of this first lens 11, and a light wave that is placed in front of this polarizer 12 and applied. A primary electro-optical element 13 that can obtain a change in the refractive index of two types of light waves due to birefringence in response to a change in a low-frequency electric field, and an auxiliary signal connected to this primary electro-optic element 13. Voltage source 1
4, a second lens 15 disposed in front of the primary electro-optical element 13 and condensing the emitted light of the primary electro-optical element 13, and an optical fiber disposed in front of the second lens 15. It consists of 16 pieces.

Next, the operation of the semiconductor laser module configured as above will be explained. First, the emitted light from the semiconductor laser 10 is converted into parallel light by the first lens IN, and the polarizer 12
The phase of the emitted wave is changed through the primary electro-optical element 13 into a linearly polarized wave. Note that the polarization direction of the polarizer 12 is the same as one of the dielectric principal axes electrically induced in the primary electro-optical element 13. At this time, since the phase of the light wave is changed by the auxiliary signal voltage source 14 connected to the primary electro-optical element 13, a phase modulation signal based on this auxiliary signal is obtained, which is focused by the second lens 15, It will be coupled to the optical fiber 16.

〔Effect of the invention〕

As explained above, the semiconductor laser module according to the present invention is configured to apply an auxiliary signal voltage source to the primary electro-optical element and superimpose the auxiliary signal on the main signal as phase modulation. When superimposing an auxiliary signal, it is no longer necessary to separately configure an external electrical circuit for superimposing the auxiliary signal, as was the case in the past. )
It produces a subdued effect.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of a semiconductor laser module according to the present invention, and FIG. 2 is a schematic diagram showing a conventional example of a semiconductor laser module. lO... Semiconductor laser, 11... First
lens, 12...Polarizer, 13...1
Secondary electro-optical element, 14... Auxiliary signal voltage source, 15... Second lens, 16... Optical fiber.

Claims (1)

[Claims] A semiconductor laser, a first lens that converts the emitted light of the semiconductor laser into parallel light, a polarizer, and refraction of two types of light waves due to birefringence in response to changes in the electric field at a lower frequency than the applied light wave. In a semiconductor laser module in which a primary electro-optic element for obtaining a change in rate, a second lens for condensing light emitted from the primary electro-optic element, and an optical fiber are sequentially arranged, the primary electro-optic element Apply an auxiliary signal voltage source to
A semiconductor laser module characterized in that it is configured to superimpose an auxiliary signal on a main signal as phase modulation.