WO2011145785A1

WO2011145785A1 - Optical module and fabricating method thereof

Info

Publication number: WO2011145785A1
Application number: PCT/KR2010/006856
Authority: WO
Inventors: Jae-Shik Choi; Gwan-Chong Joo; Do-Hoon Kim; Jung-Taek Kim; Hyo-Gyeom Kim
Original assignee: Hantech Co., Ltd.
Priority date: 2010-05-19
Filing date: 2010-10-07
Publication date: 2011-11-24
Also published as: TW201142399A; KR20110127522A

Abstract

Provided are an optical module and a method of fabricating the same. An optical fiber block includes an optical fiber array substrate having a plurality of receiving grooves in which optical fibers are respectively disposed, and an optical fiber array cover coupled to an upper surface of the optical fiber array substrate to fix the optical fiber. An optical bench has a plurality of through-holes in which the optical fibers protruding through a surface of the optical fiber block are respectively inserted. The number of the through-holes corresponds to the number of the receiving grooves formed in the optical fiber block. A first surface of the optical bench is fixed to the optical fiber block. An optical device block includes optical devices corresponding respectively to the through-holes formed in the optical bench. The optical device block is fixed to a second surface of the optical bench.

Description

OPTICAL MODULE AND FABRICATING METHOD THEREOF

The present disclosure relates to an optical module and a method of fabricating the optical module, and more particularly, to an optical module including an optical fiber block with protruded fibers and an optical substrate having circuit patterns for mounting optical devices as well as through-holes for the said optical fibers, and a method of fabricating the optical module.

As the number of high definition TVs has been rapidly increased for the last several years, the necessity of high definition multimedia interface (HDMI) cables has increased. Especially, as high bandwidths are increasingly required according to the recent release of 3D TVs or USB 3.0, a change from existing copper line HDMI cables to optical cables adapted for high capacity transmission are being required.

In general, an active optical device such as an Si PD and a vertical-cavity surface-emitting laser (VCSEL) with a wavelength band of 850 nm is used in a data communication module such as an optical HDMI. Unlike a lateral emission laser diode used in typical optical fiber communications, VCSEL emits light vertically to a surface of a laser, and thus, the optical axis of a fiber has to be aligned vertically to a laser emitting surface.

FIG. 1 is a schematic view illustrating an optical coupling device (hereinafter, referred to as a first related art) including microlens and guide pins in the related art. Referring to FIG. 1, the first related art uses the discrete guide pins and guide holes or recesses corresponding to the discrete guide pins to align a surface of an optical fiber with an active window of a laser diode. In this case, the lens is used to collect a beam emitted from a laser to a core of the optical fiber. Since the first related art requires a plurality of complicated structures for a precise optical alignment, a large number of parts to be aligned are needed, and thus, a fabricating process is difficult, and its volume is increased. Moreover, since the first related art includes many mechanically processed parts such as the guide pins and structures, it is difficult to align the processed parts with each other because of processing tolerances of the processed parts, and it is also difficult to adjust transmission characteristics.

FIG. 2 is a schematic view illustrating an optical coupling device (hereinafter, referred to as a second related art) including an optical waveguide and a dummy waveguide in the related art. Referring to FIG. 2, the second related art includes a substrate provided with a waveguide for transmitting a signal and a dummy waveguide for an optical alignment, and a glass substrate provided with an optical device and having excellent optical characteristics, and performs an optical alignment between the dummy waveguide and an alignment pattern that corresponds to the dummy waveguide on the glass substrate. In the second related art, since the glass substrate is installed between optical devices, an optical signal may be lost and distorted to a predetermined degree. As optical modules are gradually miniaturized, when a plurality of optical devices are spaced a typical distance (i.e., about 0.25 mm) in an optical module, the second related art is susceptible to an optical degradation due to the leakage of an optical signal to an adjacent channel. In addition, it is difficult to obtain a 1 m-level precision in performing an optical alignment process using the alignment pattern installed on the dummy waveguide and the glass substrate. Furthermore, in the second related art, when an optical fiber is vertical to an external circuit board to electrically connect an optical device to the external circuit board, a miniaturization of the module is limited, or when a flexible substrate attached to an electrode of an optical device is bent to be connected to the external circuit board as illustrated in FIG. 2 to parallel the optical fiber with the external circuit board, a physical reliability of a connection part is degraded and the volume and length for connecting electrodes are increased.

The present disclosure provides an optical module and a method of fabricating the optical module, which includes an optical fiber as an optical signal transmitting medium and an optical substrate fabricated through a semiconductor process without a guide device such as a lens for optical coupling, to align an active optical device with the optical fiber with a 1 μm-level precision and facilitate an electrode connection to an external circuit.

According to an exemplary embodiment, an optical module includes: an optical fiber block comprising an optical fiber array substrate having a plurality of receiving grooves in which optical fibers are respectively disposed, and an optical fiber array cover coupled to an upper surface of the optical fiber array substrate to fix the optical fiber; an optical bench having a plurality of through-holes in which the optical fibers protruding through a surface of the optical fiber block are respectively inserted, the number of the through-holes corresponding to the number of the receiving grooves formed in the optical fiber block, a first surface of the optical bench being fixed to the optical fiber block; and an optical device block comprising optical devices corresponding respectively to the through-holes formed in the optical bench, the optical device block being fixed to a second surface of the optical bench.

According to another exemplary embodiment, a method of fabricating an optical module includes: disposing optical fibers in at least one of a plurality of receiving grooves formed in an optical fiber array substrate and fixing an optical fiber array cover to the optical fiber array substrate with adhesive to fabricate an optical fiber block; attaching an optical device block comprising an optical device to an optical bench; and inserting the optical fibers protruding from the optical fiber array substrate in a plurality of through-holes formed in the optical bench, and then, fixing the optical bench to the optical fiber block.

In the optical module and the method of fabricating the optical module according to the embodiments, since the substrate having the through-hole is used to couple the optical device with the optical fiber, the number of parts is smaller than the number of parts in a related art two-way VCSEL-PD optical module, and the optical module is miniaturized. Furthermore, a miniaturized simple two-way optical module, which makes it possible to achieve a manual optical alignment within a 1 μm level without a guide pin and to achieve a mass production, can be formed. In addition, since the electrode conversion device is used when the optical device is electrically connected to an external circuit board, the optical module can be mounted to be horizontal to the circuit board within the minimum height, and thus, a transmitting distance of data is decreased, which makes a high speed signal transmitting possible.

FIG. 1 is a schematic view illustrating an optical coupling device including art microlens and guide pins in the related art;

FIG. 2 is a schematic view illustrating an optical coupling device including an optical waveguide and a dummy waveguide in the related art;

FIG. 3 is a schematic view illustrating an optical module according to an exemplary embodiment;

FIG. 4 is a schematic view illustrating an optical fiber block (310) and its assembly for protruded fibers (302);

FIG. 5 is a schematic view illustrating the second surface of an optical bench (320) on which optical devices (330, 340) are bonded;

FIG. 6 is a schematic view illustrating a process of manually aligning the optical bench (320);

FIG. 7 is a schematic view illustrating an optical bench (700) according to another exemplary embodiment;

FIG. 8 is a schematic view illustrating a process of manually aligning the optical bench (700);

FIG. 9 is a schematic view illustrating an optical bench (900) according to still another exemplary embodiment;

FIG. 10 is a schematic view illustrating a process of manually aligning the optical bench (900);

FIG. 11 is a schematic view illustrating an assembly of an optical module including electrode conversion blocks (350), the optical bench (320) and optical fiber block (310);

FIG. 12 is a schematic view illustrating an optical module (300) mounted on a substrate, according to yet another exemplary embodiment; and

FIG. 13 is a block diagram illustrating a method of fabricating an optical module according to yet still another exemplary embodiment.

Hereinafter, specific embodiments will be described in detail with reference to the accompanying drawings.

FIG. 3 is a schematic view illustrating an optical module according to an exemplary embodiment.

Referring to FIG. 3, an optical module 300 according to the current embodiment includes an optical fiber block 310, an optical bench 320, a laser diode array 330, a photodiode array 340, and conversion blocks 350 (350-1, 350-2). The laser diode array 330 includes a plurality of light emitting devices configured to convert electrical signals to optical signals and output them, and the photodiode array 340 includes a plurality of light receiving areas configured to convert incoming optical signals to electrical signals and output them. The laser diode array 330 and the photodiode array 340 are flip-chip bonded to the optical bench 320. The laser diode array 330 and the photodiode array 340 can be collectively called active optical devices 360.

A plurality of optical fibers or an optical fiber array (301) is mounted on the optical fiber block 310, and the optical bench 320 is attached to a surface of the optical fiber block 310. FIG. 4 is a schematic view illustrating the assembly of an optical fiber block 310. Referring to FIG. 4, the optical fiber block 310 includes an optical fiber array substrate 410 provided with V-shaped fiber receiving grooves, and an optical fiber array cover 420 configured to fix a plurality of optical fibers coupled to the optical fiber array substrate 410 and inserted in the receiving grooves, so as to align the optical fibers with a sub-micro level precision through semiconductor fabrication process or precise process equivalent to that of semiconductor. A plurality of cylindrical optical fibers having a diameter of tolerance of 0.5 μm or less are mounted in the receiving grooves of the optical fiber array substrate 410, and the optical fiber array cover 420 is fixed with adhesive to the upper surface of the optical fiber array substrate 410 to securely dispose the mounted optical fibers in the receiving grooves. At this point, the mounted optical fiber protrudes a predetermined length, which is preferably shorter than the through-hole 510 depth, from the optical fiber block 310 such that an end of the mounted optical fiber is inserted to a through-hole 510 formed in the optical bench 320. The tip face of the protruding optical fibers 320 facing active windows of the active optical devices 360 may be polished to an angle and/or coated for better optical performance or mechanical function. The optical fiber array cover 420 and the optical fiber array substrate 410 have the same size. However, if necessary, the optical fiber array cover 420 may be longer or shorter than the optical fiber array substrate 410 in the longitudinal direction of the optical fiber receiving grooves formed in the optical fiber array substrate 410.

The optical bench 320 is a module for effectively guiding the optical fiber to an intended point of the active optical device. FIG. 5 is a schematic view illustrating an optical bench 500 corresponding to the optical bench 320, according to an exemplary embodiment. Referring to FIG. 5, the optical bench 500 has a plurality of through-holes 510 corresponding to the active windows of the active optical devices 360 provided to the light emitting device block 330 and the light receiving device block 340 that are flip-chip bonded. The through-holes 510 guide the optical fibers 302 protruding from the optical fiber block 310 to the active windows of the active optical devices 360, and have a size corresponding to the diameter of the optical fibers 302. For example, the through-holes 510 may have a diameter of 1 μm or greater than that of the optical fibers 302, considering an alignment precision and a process feasibility. Solders and electrode lines 520 are formed on the second surface of the optical bench 500 to flip-chip bond the optical devices 360 and to electrically connect the optical devices 360 to an external circuit. One or more alignment indications 530 may be formed on the first surface of the optical bench 500 to align the optical bench 500 with the optical fiber block 310, and one or more alignment indications 540 may be formed on the second surface of the optical bench 500 to align the optical bench 500 with the light emitting device block 330 and the light receiving device block 340. The

alignment indications

530 and 540 are positioning indications for recognizing relative positions between the through-holes 510 and the optical fibers 302 in the up-and-down and left-and-right directions when the optical fibers 302 protruding from the optical fiber block 310 are aligned with the through-holes 510 of the optical bench 500, and may be formed by metal patterning or etching.

FIG. 6 is a schematic view illustrating a process of manually aligning the optical bench 500 according to the current embodiment.

Referring to FIG. 6, a guide structure 610 may be formed at the end of the through-holes 510 to guide a misaligned optical fiber easily to the center of the through-holes 510 formed in the optical bench 500. The diameter of the through-hole 510 in the rear surface of the optical bench 320, on which active optical devices 360 are bonded to bonding pads 620, that is, the diameter of the through-hole 510 in the side facing the light emitting device block 330 and the light receiving device block 340 corresponds to the size of an optical fiber, considering an optical alignment precision with the optical fiber, but the guide structure 610 has a tapered ring (also denoted by 610) such that the diameter of the through-hole 510 in the front surface of the optical bench 320, that is, the diameter of the through-hole 510 in the side facing the optical fiber block 310 is greater than the diameter of the through-hole 510, and thus, the optical fiber can be easily inserted in the through-holes 510. Alternatively, while the through-holes 510 may have a constant diameter, inclined recesses having a size greater than the diameter of the through-hole 510 may be formed in the front surface the optical bench 320 and disposed respectively around the through-holes 510, or auxiliary devices functioning as the inclined recesses may be disposed around the through-holes 510, so that the optical fiber can be easily inserted in the through-holes 510.

FIG. 7 is a schematic view illustrating an optical bench 700 according to another exemplary embodiment. FIG. 8 is a schematic view illustrating a process of manually aligning the optical bench 700 according to the current embodiment. Referring to FIGS. 7 and 8, the optical bench 700 has through-holes 710 with a multi-step structure, i.e., different diameters, to prevent physical contacts between optical fibers inserted in the through-holes 710 and the active windows of active optical devices 360. That is, the through-hole 710 has a diameter smaller than that of the optical fibers 302 in the immediate region from the first surface of the optical bench 700, contacting the optical devices provided to the light emitting device block 330 and the light receiving device block 340, to a predetermined point, and the through-hole 710 towards the first surface has a diameter greater than or equal to that of the optical fiber 302 from the predetermined point toward the optical fiber block 310. Thus, a step 820 is formed in the through-hole 710. Thus, the optical fiber inserted into the through-hole 710 can be stopped at a predetermined depth preventing direct physical contact to active optical devices 360.

FIG. 9 is a schematic view illustrating an optical bench 900 according to another exemplary embodiment. FIG. 10 is a schematic view illustrating a process of manually aligning the optical bench 900 according to the current embodiment. Referring to FIGS. 9 and 10, to prevent physical contacts between optical fibers 302 inserted into through-holes 910 and the active windows of the active optical devices 360, one end of through-holes 910 at the second surface of the optical bench 900 has a diameter smaller than the diameter of the optical fiber 302, while the other end at the first surface has a diameter larger than that of the optical fiber 302. Thus, the optical fiber inserted in the through-hole 910 is prevented from directly contacting the active optical device 360.

The light emitting device block 330 includes a plurality of light emitting devices configured to convert an electrical signal to an optical signal and output it, and the light receiving device block 340 includes a plurality of light receiving devices configured to convert an optical signal to an electrical signal and output it. The light emitting device block 330 and the light receiving device block 340 are bonded to the optical bench 320 through flip chip bonding.

The conversion block 350 is used to electrically connect the active optical devices 360 with an external circuit. When the fiber array block 300 is horizontally mounted on the circuit board, the active optical devices 360 bonded on the optical bench 320 are placed at right angle to the circuit board. If so, prohibitably difficult is the wire bonding for electrical connection between the active optical device and the circuit board. Conversion blocks 350 as a medium device facilitating wire bonding can be used to convert the direction of the right angled electrodes 502 on the optical module 300 to the direction parallel to the electrodes on external circuits. The conversion block 350 may be made of electrically resistive material such as silicon or glass. The conversion block 350 includes a transmitting line corresponding to an electrode 502 of each active optical device 360, and may include discrete blocks respectively corresponding to a positive electrode and a negative electrode of the optical device 360. In this case, an optical device transmitting line formed in the optical bench 320 is aligned with a transmitting line of conversion blocks 350-1 and 350-2, and then, side surfaces of the conversion blocks 350-1 and 350-2 are fixed to the optical bench 320 with adhesive, and solder or conductive epoxy is applied to a cross connection part between the two transmitting lines to physically connect electrodes. The conversion blocks 350-1 and 350-2 make it possible to connect electrodes within an even shorter distance than an electrode connection method using a flexible substrate in the related art, and thus, the signal loss in high-speed signal transmission can be reduced, and the size thereof can be minimized.

FIG. 11 is a schematic view illustrating a process of coupling the conversion block 350 with the optical bench 320. Referring to FIG. 11, the optical fiber block 310 is coupled to the optical bench 320 in which the active optical devices 360 are integrated, using vertical and horizontal alignment indications disposed respectively on the front and rear surfaces of the optical bench 320 to easily insert a plurality of protruding fiber optics in the through holes of the optical bench 320. When a protruding surface of the optical fiber block 310 contacts a surface of the optical bench 320, they are fixed with adhesive. The conversion block 350 includes conversion blocks 350-1 and 350-2, which are coupled respectively to portions of the optical bench 320. FIG. 12 is a schematic view illustrating the optical module 300 mounted on a substrate according to an exemplary embodiment. Referring to FIG. 12, the optical module 300 is wire-bonded to an external circuit 1200 such as a printed circuit board (PCB) on which an optical module is mounted.

FIG. 13 is a block diagram illustrating a method of fabricating an optical module according to an exemplary embodiment.

Referring to FIG. 13, an optical fiber is disposed in at least one of the receiving grooves formed in the optical fiber array substrate 410, and the optical fiber array cover 420 is fixed to the optical fiber array substrate 410 with adhesive to fabricate the optical fiber block 310 in operation S1300. At this point, an end of the optical fiber 302 protruding through an end of the optical fiber block 310 formed by coupling the optical fiber array substrate 410 and the optical fiber array cover 420 is ground or coated with an optical film. In operation S1310, the light emitting device block 330 and the light receiving device block 340, which include the optical devices, are attached to the optical bench 320 through flip chip bonding. In this case, operation S1310 may be performed before operation S1300, or operations S1310 and S1300 may be performed independently. In operation S1320, the optical fiber 302 protruding from the optical fiber block 310 is inserted in the through-

hole

510, 710, or 910 formed in the optical bench 320, and then, the optical bench 320 is fixed to the optical fiber block 310 with adhesive. In operation S1330, the conversion block 350 for connecting the active optical devices 360 to an external circuit 1200 is attached to the optical bench 320, and the electrode 502 is physically connected to the external circuit 1200 with solder or conductive epoxy.

Although the optical module and the method of fabricating the optical module have been described with reference to the specific embodiments, they are not limited thereto. Therefore, it will be readily understood by those skilled in the art that various modifications and changes can be made thereto without departing from the spirit and scope of the present invention defined by the appended claims.

Claims

An optical module comprising:

an optical fiber block comprising an optical fiber array substrate having a plurality of receiving grooves in which optical fibers are respectively disposed, and an optical fiber array cover coupled to an upper surface of the optical fiber array substrate to fix the optical fibers;

an optical bench having a plurality of through-holes in which the optical fibers protruding through a surface of the optical fiber block are respectively inserted, the number of the through-holes corresponding to the number of the receiving grooves formed in the optical fiber block, a first surface of the optical bench being fixed to the optical fiber block; and

an optical device block comprising optical devices corresponding respectively to the through-holes formed in the optical bench, the optical device block being fixed to a second surface of the optical bench.
The optical module of claim 1, further comprising a conversion block electrically connecting the optical device of the optical device block to an external circuit and fixed to the second surface of the optical bench.
The optical module of claim 2, wherein the conversion block comprises transmission line corresponding to an electrode of each optical device of the optical device block.
The optical module of claim 2 or 3, wherein the conversion block is a medium device configured to convert a state in which the electrode is vertical to a circuit board to a state in which the electrode is horizontal to the circuit board such that the electrode is electrically connected to the external circuit.
The optical module of claim 2 or 3, wherein discrete blocks correspond respectively to a positive electrode and a negative electrode of the optical device provided to the optical device block.
The optical module of claim 1, wherein the through-hole formed in the optical bench has a greater diameter than that of the inserted optical fiber.
The optical module of claim 1, wherein the through-hole formed in the optical bench has a smaller diameter than that of the inserted optical fiber from the second surface of the optical bench to a first point toward the first surface of the optical bench, and has a greater diameter than that of the inserted optical fiber from the first point to the first surface of the optical bench.
The optical module of claim 1, wherein the through-hole formed in the optical bench has a smaller diameter at the second surface of the optical bench than a diameter of the inserted optical fiber, and has a greater diameter at the first surface of the optical bench than the diameter of the inserted optical fiber, and constantly increases in diameter from the second surface of the optical bench to the first surface of the optical bench.
The optical module of claim 7 or 8, wherein the through-hole formed in the optical bench is tapered at the first surface of the optical bench.
The optical module of any one of claims 1, 2, 3, 6, 7 and 8, wherein an end of the optical fiber protruding through an end of the optical fiber block is polished or coated.
The optical module of any one of claims 1, 2, 3, 6, 7 and 8, wherein the first and second surfaces of the optical bench are provided with alignment indications formed through etching or metal patterning to align the optical fiber block with the optical device block.
A method of fabricating an optical module, the method comprising:

disposing optical fibers in at least one of a plurality of receiving grooves formed in an optical fiber array substrate and fixing an optical fiber array cover to the optical fiber array substrate with adhesive to fabricate an optical fiber block;

attaching an optical device block comprising an optical device to an optical bench; and

inserting the optical fibers protruding from the optical fiber array substrate in a plurality of through-holes formed in the optical bench, and then, fixing the optical bench to the optical fiber block.
The method of claim 12, further comprising attaching a conversion block to the optical bench, the conversion block being configured to electrically connecting the optical device provided to the optical device block to an external circuit.
The method of claim 12 or 13, wherein an end of the optical fiber protruding through an end of the optical fiber block is ground or coated with an optical film.
The method of claim 12 or 13, wherein the through-hole formed in the optical bench has a greater diameter than that of the inserted optical fiber.
The method of claim 12 or 13, wherein the through-hole formed in the optical bench has a smaller diameter than that of the inserted optical fiber from a second surface of the optical bench to a first point toward a first surface of the optical bench, and has a greater diameter than that of the inserted optical fiber from the first point to the first surface of the optical bench.
The method of claim 12 or 13, wherein the through-hole formed in the optical bench has a smaller diameter at a second surface of the optical bench than a diameter of the inserted optical fiber, and has a greater diameter at a first surface of the optical bench than the diameter of the inserted optical fiber, and constantly increases in diameter from the second surface of the optical bench to the first surface of the optical bench.