JPH1068909A - Sleeve built-in type optical isolator and optical semiconductor module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the adjustment at the time of assembly, to enable simple constitution to a small size and to enable the use of the optical isolator as an optical isolator of a surface packing and integrated type by installing an optical isolator element and a connecting capillary into a sleeve. SOLUTION: The part constituting the optical isolator part 1 is formed by holding both surfaces of a Faraday rotator for rotating the plane of polarization of the light passing the middle thereof with polarizers. The Faraday rotator rotates the planes of polarizer of the light entering from both sides (incident light and reflected light) to the same direction. The respective polarizers deviate in the polarization directions at 45 deg. with each other. Then, the polarizers allow the transmission of the incident light from an LD which is a light emitting source and are capable of shutting off the reflected light. Both end faces of the optical isolator part 1 are tightly connected by core enlarged fibers 4 and further, the incident end fiber end face of one side is formed as a lens structure. The reflection attenuation of the element end faces may be suppressed simply by diagonally polishing the core enlarged fibers 4 and capillaries 3 packaging these fibers and connecting the element by using the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical semiconductor module used in a transmitter for transmitting signal light in optical communication, and an optical isolator used therein for removing return light.

[0002]

2. Description of the Related Art Heretofore, in order to remove return light from an optical semiconductor laser, a Faraday rotator for rotating the polarization plane of light by 45 degrees is sandwiched between two polarizers whose polarization directions are rotated by 45 degrees. An optical isolator with an uneven structure is installed between the semiconductor laser chip and the optical fiber via a connecting lens.
The reflection inside the fiber and the return light reflected by each connection end are removed, thereby preventing the return light resonance in the laser from occurring.

[0003]

However, the optical isolator having the above configuration has the following disadvantages.

(1) The laser element, lens, optical isolator, and optical fiber are independent components, and alignment adjustment of each component is required at the time of assembly, which is troublesome.

(2) When a coupling system including an isolator is formed, a space is required and the overall size becomes large.

(3) Because of the lens coupling system, it is difficult to support high-density mounting on surface-mounted and integrated components.

(4) The characteristics change due to a change in the conditions of the coupling system due to environmental changes.

There are disadvantages such as:

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve these problems, and has two sides of an optical isolator element having polarizers on both sides and a Faraday rotator in both sides connected and fixed by a fiber capillary. Provided is an optical isolator that transmits light in one direction and blocks light in the opposite direction, wherein the optical isolator element and the connection capillary are installed in a sleeve.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the optical isolator according to the present invention will be described below with reference to the drawings. FIG. 1 (a)
It is a figure which showed the side cross section of the optical isolator with a built-in sleeve by this invention, and (b) shows the connection part detail of the optical isolator with a built-in sleeve. First, the part constituting the optical isolator section is one in which both surfaces of a Faraday rotator for rotating the plane of polarization of the light passing through in the middle are sandwiched by polarizers, and the Faraday rotator has both sides (incident light and reflected light).
Are rotated by 45 degrees in the same direction, and the polarization directions of the respective polarizers are relatively shifted by 45 degrees. By adopting such a configuration, the light emitting source LD
Incident light can be transmitted and reflected light can be blocked. In the present invention, both end faces of such an optical isolator are connected in close contact with a core-enlarged fiber, and furthermore, one end of the optical fiber is provided with a lens structure. The core-expanded fiber is an ordinary single-mode optical fiber that is locally heated to diffuse the additive that increases the refractive index inside the core by heating it at a high temperature. The field diameter increases. At this time, as the mode field diameter increases, the NA of the emitted light decreases, and the emitted light is narrowed. In other words, there is a collimating lens effect, and even if an element having a thickness between them is provided, connection can be made with low loss. In the present embodiment, when an optical isolator element having a thickness of 0.7 mm and a mode field diameter of 35 μm is used, an insertion loss of 1 dB or less is easily achieved. Further, in order to suppress the return loss of the element tanmen, as shown in the figure, the core enlarged fiber and the capillary on which it is mounted may be polished obliquely and connected using the same. Further, in the figure, a magnet for providing a saturation magnetic field to the Faraday rotator is provided. However, when the Faraday rotator itself is already magnetized and has a characteristic having a coercive force, the magnet becomes unnecessary. In FIG. 1 (a), one side tammen is processed into a spherical shape so that it can be directly connected to a light source. Other structures may be used as the lens structure. An optical isolator with a built-in sleeve constructed in this manner is connected to an LD as shown in FIG.
It can be mounted and configured as an optical module with an isolator by an easy alignment process by installing and fixing it in a V-groove or the like on a Si substrate having a metal thin film electrode on which an element and a PD element are mounted, and directly connecting to the LD element of the light source. I can do it. In FIG. 3, an optical isolator with a built-in sleeve is
By mounting on the board, packaging, part of the output side sleeve out of the package, and inserting the pigtail with the capillary attached to the end of the fiber, it can be easily connected to and detached from the fiber. When configuring an optical circuit, the routing fiber does not become an obstacle and can be easily assembled.

[0011]

As described above, according to the present invention,
There are the following excellent effects.

(1) An optical isolator element in a sleeve,
Since the light source connection lens is integrally formed, adjustment at the time of assembly is easy.

(2) It can be made compact and simple, and can be used as a surface mount / integrated optical isolator.

(3) Since the inside has a lensless structure, a component structure resistant to environmental changes is provided.

(4) By mounting on a module, a module component that can be easily connected to and removed from other fibers can be configured.

[Brief description of the drawings]

1A is a side sectional view of an optical isolator with a built-in sleeve according to the present invention, and FIG. 1B is a detailed structural view near a Faraday rotator in the sectional view.

FIG. 2A is a top view of an embodiment in which an optical isolator with a built-in sleeve according to the present invention is mounted on a Si substrate, and FIG. 2B is a side view of the optical isolator with a built-in sleeve according to the present invention. .

FIG. 3 is an external view of an optical module having a substrate on which an optical isolator with a built-in sleeve according to the present invention is mounted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical isolator element part 2 Sleeve 3 Capillary 4 Tanmen core expansion fiber 5 V-groove board 6 Sleeve built-in optical isolator 7 Optical package 8 Fiber pigtail

Claims (4)

[Claims] 1. An optical isolator having a polarizer on both sides and an optical isolator element having a Faraday rotator in both sides connected and fixed by a fiber capillary, transmitting light in one direction and blocking light in the opposite direction. An optical isolator with a built-in sleeve, wherein an optical isolator element and a connection capillary are set in a sleeve. 2. The optical isolator with a built-in sleeve according to claim 1, wherein the mode field of the fiber in the one-side entrance side capillary is enlarged. 3. The optical isolator with a built-in sleeve according to claim 1, wherein the incident-side end face fiber has a lens function. 4. An optical semiconductor wherein the optical isolator with a built-in sleeve is installed on a substrate having a V-groove shape or a similar shape, and the optical isolator with a built-in sleeve is coupled to an LD light source on the substrate. module.