JPH08234046A - Optical parts - Google Patents

Abstract

PURPOSE: To facilitate integration with other optical parts and to obtain a smaller size and higher reliability by expanding the mode field diameter of optical fibers at input and output ends. CONSTITUTION: Optical elements ISO are composed by holding and tightly integrating Faraday rotators fr and half-wave plates hw with two sheets of double refractive elements dr. The fibers f (2), f (5) expanded with the cores at the end faces are respectively tightly adhered and integrated to the end faces of two sheets of the double refractive elements dr constituting these input and output parts. The end faces of the fibers f (2), f (5) expanded with the cores at the end faces may be worked by grinding, etc., to lenses of a conical shape, etc., and lensless integrated constitution is obtd. as optical composite function parts, by which coupling efficiency is enhanced. Then, the tight connection to other optical parts and lensless connection are made possible. The integrated constitution (miniaturization, improvement of reliability, decreasing of the number of parts and a cost reduction) with other optical parts is facilitated as well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical component formed by bundling a plurality of optical fibers and forming a coupling portion by fusion-spreading the intermediate portion of the optical fibers. It can be used as an optical component for an amplifier, which can be reduced in size, improved in reliability, and reduced in price.

[0002]

2. Description of the Related Art Conventionally, in order to construct an optical fiber amplifier, in addition to a rare earth-doped optical fiber doped with a rare earth (Er, Pr, etc.) in a core, signal light is monitored, pumping light is combined, and return light is generated. Needed an optical circuit to shut off. For that purpose, an optical multiplexer, an optical branching device, and an in-line type (birefringence type) optical isolator were combined according to the application, and the fiber ends of each component were connected to form a circuit. However, such conventional optical circuits for fiber amplifiers have the following drawbacks. Further, usually, a fiber fusion-stretching type component in which a plurality of optical fibers are bundled and a middle portion thereof is fusion-stretched to form a coupling portion is used as an optical multiplexer and an optical brancher in an optical circuit for a fiber amplifier. Has been.

[0003]

[Problems to be Solved by the Invention]

(1) Since the individual parts having various functions are connected by fusion splicing of the fiber ends for use, wiring turns (remaining length treatment) and connection reinforcement parts for fixing are required separately, and the number of parts and circuit Storage space has increased.

(2) Therefore, it is necessary to separately prepare a reinforcing member and perform fusion splicing, which increases the number of parts used in the process, makes it difficult to reduce the price, and makes it difficult to mount the device in small size.

(3) A splice loss occurs at the fiber splicing portion, and there is a problem in reliability due to aging.

(4) Most of the functional parts used have a structure in which a lens is used, which requires time and effort for assembly adjustment, making it difficult to reduce the size and cost.

[0007]

In view of the above-mentioned problems, the present invention makes it easy to assemble and adjust a fiber fusion drawing type component by eliminating splice components and lens components and easily integrating it with other optical elements. In order to achieve miniaturization and high reliability, the mode field diameter of the optical fiber is enlarged at the input and output ends of the fiber fusion-type component, which allows the functional components to be sandwiched. It is a thing.

[0008]

An embodiment according to the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of an optical component structure for an amplifier according to the present invention, showing an optical circuit for forward pumping. Here, the pumping light multiplexer WDM and the amplified light monitor coupler COP are configured by a fiber fusion drawing type, and a mode field expansion is performed on the fiber input / output end face for connection with the optical element ISO functioning as an in-line type isolator. It has been processed.

In the mode field expansion treatment, the core CO is heated by locally heating the fiber at around 1500.degree.
It is obtained by diffusing an additive (dopant) such as Ge contained in RE that increases the refractive index. The present invention uses a fiber with an expanded mode field by locally heating the mode field by expanding the core.

As the mode field diameter is expanded, the opening of the end face core expanding fiber is narrowed, and the emitted light is in a state close to parallel light due to the lens effect. Therefore, a low-loss connection can be realized with the optical element ISO sandwiched without using a lens. Further, the end faces of the respective fibers may be connected in a flat state, but they may be formed into a spherical shape or a conical shape so as to have a lens function. By adopting such a connection configuration, a low loss configuration can be achieved without using a separate lens.

Here, the in-line type optical isolator uses a birefringent optical material, a Faraday rotator, etc., and blocks return light by a separation optical system, and is constructed by closely adhering and integrating each component. .

In FIG. 1, reference numerals 1 to 6 are optical fibers, 7 is a fixed substrate of the pumping light multiplexer WDM, 8 is a fixed substrate of the coupler for amplifying light monitor COP, and 9 is a fiber end portion of the pumping light multiplexer WDM. A ferrule for holding (optical fiber 5), 10 is a ferrule for holding the fiber end (optical fiber 2) of the coupler for amplified light monitor COP, 11
Is ferrule 9, ferrule 10, and optical element ISO (M
G is a case that integrally houses a cylindrical magnet for applying a magnetic field to the Faraday rotator, and finally 12 is a case that integrally houses the fixed substrate 7, the fixed substrate 8 and the case 11.

FIG. 2A shows a structure in which the fiber input / output end face and the optical element ISO are closely integrated with each other. Reference symbols f (2) and f (5) are end face core expansion fibers, and dr.
Is a birefringent element, fr is a Faraday rotator, hw is 1/2
A birefringent element dr with two optical elements ISO is shown showing a wave plate.
The Faraday rotator fr and the half-wave plate hw are sandwiched and closely integrated with each other.
An end face core expansion fiber f is provided on the end face of the single birefringent element dr.
(2) and f (5) are tightly integrated with each other. The dotted line in the optical element ISO indicates the forward optical path (left to right direction), and the alternate long and short dash line indicates the reverse optical path (right to left).

Further, as shown in FIG. 2B, the end faces of the end face core expanding fibers f (2) and f (5) may be processed into a lens having a conical shape by grinding or the like. It can be integrated without a lens, and the coupling efficiency can be improved.

The mounting of the end portion of the optical fiber on the ferrules 9 and 10 comprises the steps of thermal diffusion treatment of the dopant at the end portion of the optical fiber, inserting the optical fiber into the ferrule, and then polishing the end surface of the ferrule. . When the lens processing is applied to the end portion of the fiber, it includes the steps of performing the dopant diffusion processing and the lens processing processing, inserting the optical fiber into the ferrule, and polishing the end surface of the ferrule.

In the above embodiment, the multiplexing and branching are described as an example in which the fiber type component (WDM, COP) and the optical element ISO are integrally formed, but the present invention is not limited to this, and other functions are provided. It can also be applied to a structure without a fiber-to-fiber connection part that is configured by a functional component made of the micro optical element.

3 (a) and 3 (b) are circuit configuration examples using the optical parts according to the present invention, and a configuration having only a branching function or only a multiplexing function can be taken as required.

FIG. 4 shows an embodiment in which a bidirectional pumping fiber amplifier is constructed by using the optical parts according to the present invention, and can be applied to forward pumping, backward pumping, etc., if necessary.

[0019]

As described above, the following effects are provided by the present invention.

(1) The fiber-fusion type optical component can be directly connected to other optical components, that is, by increasing the mode field diameter at the input and output ends, the coupling efficiency is increased and the assembly is easy. Therefore, close connection and lensless connection with other optical components are possible, and the integrated configuration with other optical components (miniaturization, reliability improvement, reduction of the number of components, cost reduction) is facilitated.

(2) Conventionally, in order to construct a pumping optical circuit of an optical amplifier, it was troublesome to wire the optical fiber. However, according to the present invention, the fiber fusion drawing type component and the in-line type optical isolator are used. Since it can be configured integrally, there is no wiring turning connection portion, the number of steps is reduced, and the space can be reduced.

(3) Lensless connection is possible and alignment-free construction is possible, which is advantageous for downsizing and cost reduction.

[Brief description of drawings]

FIG. 1 is a structural cross-sectional view showing an embodiment in which a forward pumping optical circuit used in an optical amplifier is constituted by an optical component according to the present invention.

2A and 2B are detailed configuration diagrams of a mode field expansion connection unit of FIG.

FIG. 3 is a diagram showing an optical circuit configuration example of an optical component according to the present invention.

FIG. 4 is a configuration diagram of an embodiment in which a bidirectional pumping optical fiber amplifier is configured using the optical component according to the present invention.

[Explanation of symbols]

 1 to 6: Optical fiber 7, 8: Fixed substrate 9, 10: Ferrule 11, 12: Case ISO: Optical element (birefringent isolator) MG: Cylindrical magnet WDM: Excitation optical multiplexer BO: Adhesive COP: Amplified light Monitor couplers f (2), f (5): end face core expanding fiber CORE: core L.P. D. : Semiconductor laser Er: Er-doped fiber sc: Splice connection

Claims (5)

[Claims] 1. An optical component formed by bundling a plurality of optical fibers and forming a joint portion by fusion-stretching an intermediate portion of the optical fibers,
The optical component is characterized in that a mode field diameter is enlarged at an input / output end of the optical fiber. 2. The optical component according to claim 1, wherein the mode field diameter at the input / output end of the optical fiber is expanded by thermal diffusion of a dopant. 3. The optical component according to claim 1, wherein the input / output end face of the optical fiber is closely fixed to another optical element. 4. The optical component according to claim 1, wherein the input and output ends of the optical fiber are processed into a spherical shape or a conical shape to form a lens. 5. An optical fiber output end face of one optical component and an optical fiber input end face of the other optical component are used to form an input / output end face of an in-line type optical isolator which is another optical element. 5. The optical component according to claim 1, wherein the birefringent elements are closely fixed to each other to form a pumping optical circuit of an optical fiber amplifier.