JP2949318B2 - Optical isolator with lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser and an optical isolator with a lens used for optical fiber communication using an optical fiber amplifier.

[0002]

2. Description of the Related Art Semiconductor lasers (hereinafter abbreviated as LDs)
In the case, when the emitted light is reflected outside and enters the active layer again as return light, the oscillation wavelength and output fluctuate. For this reason, it is indispensable to prevent return light in order to perform highly reliable optical communication such as high-speed and high-density signal transmission and high-precision optical measurement. Used.

As shown in a schematic sectional view of FIG. 5, an LD 27, an output monitoring photodiode 28, a lens, and a lens are connected to a conventional LD and an optical fiber via an optical isolator. 23a, 23
b, an optical isolator 24, and an optical fiber 20 are installed. The light emitted from the LD 27 is substantially collimated by the lens 23a, passes through the optical isolator 24, and is condensed by the lens 23b. And transmitted to the optical fiber 20.

Here, the method of assembling the semiconductor laser module is as follows. The LD 2 is placed inside a package 29 having an airtight window 25 for placing the LD 27 in an airtight state.
7. Install the photodiode 28 after adjusting the position.
Lens 2 for collimating light emitted from LD 27
3a is attached to the lens holder 26a, the position is adjusted with respect to the LD 27, and fixed by YAG welding or the like. The optical isolator holder 21 holding the optical isolator 24
Is adjusted so that the collimated light passes through the center,
The optical isolator holder 21 is fixed by YAG welding or the like.
Further, after the position of the lens holder 26b holding the lens 23b is adjusted and fixed, the position of the optical fiber 20 is adjusted and fixed at the optimum coupling position.

[0005]

However, in the conventional configuration, since many steps are required to manufacture an optical isolator with a lens, it is very complicated and time-consuming.
Further, since the lens holders 26a and 26b for holding the lenses 23a and 23b and the optical isolator 24 and the optical isolator holder 21 are required, the number of parts is inevitably increased, and unless the above is manufactured inside the package 29. There was a problem that did not become.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has been made in consideration of the above circumstances, and has been made in consideration of the above circumstances. An optical isolator with a lens in which a lens for condensing light on an optical fiber is fixed in this order in a cylindrical body.

[0007]

Embodiments of the present invention will be described below. As shown in a partially broken perspective schematic view of the optical isolator with a lens of the present invention in FIG. 1 and a schematic cross-sectional view of FIG. 2, an optical isolator with a lens of the present invention has a rod inside a cylindrical body 2. The lens 3, the optical isolator 4, and the aspherical lens 5 are arranged in this order. The rod lens 3, the optical isolator 4, and the aspherical lens 5 are fixed by incorporating the rod lens 3 into the cylindrical body 2, air-tightly fixing with a low-melting glass or the like, and then incorporating the optical isolator 4 into the rod lens 3 and the light. Adjust the position in the front-back direction and the rotation direction so that the axes match,
After fixing by YAG welding or the like, the lens holder 6 holding the aspherical lens 5 may be adjusted so that the optical axis coincides with the optical isolator 4 and fixed to the cylinder 2 by YAG welding or the like.

FIG. 3 is a schematic cross-sectional view of an LD module assembled in a semiconductor laser package using the optical isolator 1 with a lens having the above-described configuration, in which an LD 7 and a photodiode 8 for output monitoring are installed. It is composed of a package 9, an optical isolator 1 with a lens, and an optical fiber 10. When manufacturing, the optical isolator 1 with a lens is adjusted in position in the front-rear direction and the rotational direction with respect to the optical signal of the LD 7, and then fixed. In this case, the position of the optical fiber 10 may be adjusted and fixed so as to increase the height.

Here, as the optical isolator 4, FIG.
As shown in FIG. 2, a polarizer 11 that allows only linearly polarized light in a specific direction (0 °) to pass therethrough and blocks light having a polarization plane orthogonal to the polarization direction, and a polarization direction of the passing light by 45 ° irreversible A Faraday rotator 12 for rotating the polarizer 11 and an analyzer 13 which is the same member as the polarizer 11 and whose transmission polarization direction is inclined by 45 ° with respect to the transmission polarization direction of the polarizer 11 are arranged in a cylindrical magnet. What is necessary is just to comprise. With such a configuration, when clockwise as viewed from the left in the drawing is a positive angle, light coming from the left becomes linearly polarized light having a specific polarization component (0 °) by the polarizer 11. Since the polarization plane of the light is rotated by 45 ° by the Faraday rotator 12 and the polarization direction of the analyzer 13 is arranged in accordance with the polarization plane, the light passes through the analyzer 13 with almost no loss. Can be. Conversely, the light coming from the right side passes only linearly polarized light of the same polarization component as that of the analyzer 13 in the direction of 45 ° by the analyzer 13, and the polarization plane is further rotated by 45 ° by the Faraday rotator 12 to 90 °. However, since this plane of polarization is perpendicular to the plane of polarization of the polarizer 11, it cannot pass through the polarizer 11. Than this,
Light coming from the left can pass to the right, but light coming from the right cannot pass to the left.

When the optical isolator 4 is disposed in the LD module so that the polarizer 11 has the same polarization plane as the optical signal from the LD 7, the light emitted from the LD 7 is substantially collimated by the aspherical lens 5. After that, the light passes through the optical isolator 4 and is condensed by the rod lens 3 and transmitted to the optical fiber 10 with low loss. Further, light that is reflected in the middle of the transmission path, becomes return light, and exits from the optical fiber 10 in the opposite direction is blocked by the optical isolator 4 and
D7 does not return, and high-speed and high-precision optical communication and optical measurement can be performed.

As described above, with the configuration of the optical isolator 1 with a lens according to the present invention, the optical isolator 1 with a lens can be handled in the same manner as a lens.
The process of assembling the D module is greatly simplified, the number of components is minimized, and since the assembly is not performed in a narrow LD package, handling can be made very easy. When the optical isolator with lens 1 is welded to the package 9 by seam welding or the like, when the rod lens 3 is fixed to the cylindrical body 2, the rod lens 3 is air-tightly fixed with low-melting glass. Without using a special airtight member such as an airtight window, airtightness in the cylindrical body 2 can be easily maintained, and deterioration of the LD inside can be prevented.

As another example of the optical isolator, a polarization independent optical isolator using a birefringent element may be used. There is no problem even if the rod lens 3 and the aspherical lens 5 are reversed, and a ball lens may be used as the lens, and can be freely selected depending on various uses such as coupling efficiency. Further, in this embodiment, the rod lens 3 and the aspherical lens 5 are fixed with low-melting glass, but there is no problem if a metal film is formed on the outer periphery of the lens and hermetically fixed with solder.

[0013]

As described above, according to the optical isolator with a lens of the present invention, a lens for converting light emitted from a semiconductor laser into collimated light, an optical isolator, and an optical fiber for transmitting light passing through the optical isolator. By fixing the condensing lens to the cylinder in this order, the optical isolator with the lens can be handled in the same way as the lens, the process of assembling the LD module is greatly simplified, and the number of components is minimized. Limited and narrow L
Since it is not assembled in a D package, handling can be made very easy. In addition, when the lens is fixed to the cylinder, since the lens is air-tightly fixed with low-melting glass, no special air-tight parts such as air-tight windows are required, so that the air-tightness in the package is easily maintained, and the LD is sealed. Deterioration can be prevented.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective schematic view showing an optical isolator with a lens of the present invention.

FIG. 2 is a schematic sectional view showing an optical isolator with a lens according to the present invention.

FIG. 3 is a schematic sectional view showing a semiconductor laser package using the optical isolator with a lens of the present invention.

FIG. 4 is a diagram showing a structure of an optical isolator.

FIG. 5 is a schematic sectional view showing a conventional semiconductor laser package.

[Explanation of symbols]

 1: optical isolator with lens 2: cylindrical body 3: rod lens 4, 24: optical isolator 5: aspheric lens 6, 26a, 26b: lens holder 7, 27: LD 8, 28: photodiode 9, 29: package 10 , 20: Optical fiber 11: Polarizer 12: Faraday rotator 13: Analyzer 21: Optical isolator holder 23a, 23b: Lens 25: Airtight window

Claims (1)

(57) [Claims] An optical isolator with a lens attached to a package containing an optical element in a hermetically sealed state, wherein the collimator lens converts the light emitted from the optical element into collimated light; an optical isolator; An optical isolator with a lens, wherein a condensing lens for condensing light passing through the isolator into an optical fiber is housed in one cylinder, and at least one of the collimating lens and the condensing lens is hermetically fixed. .