FR2766930A1 - Passive optical fibre alignment device - Google Patents

Abstract

A passive alignment device for aligning optical fibres with the input/output waveguides of an integrated optical device comprises: (a) a matrix block with spaced alignment grooves in which the optical fibres are received and held by a holding plate; (b) a waveguide chip with a matrix of input/output waveguides, corresponding to the fibres, and with alignment holes; and (c) an alignment platform with alignment stops spaced by the same spacing as the alignment grooves, alignment bumps formed at positions corresponding to the alignment holes, and a space between the alignment stops to prevent the holding plate from contacting the platform. The alignment platform and the matrix block consist of silicon substrates which are provided with a mask pattern by photolithography and then etched in a KOH solution, or which are precision moulded or machined. The waveguide chip is produced by forming a lower cladding layer on a substrate, forming a core layer of greater refractive index, forming channel-type waveguides by etching, forming an upper cladding layer, and then forming the alignment holes by precision machining. The waveguides may be silica, polymer, glass or lithium niobate waveguides. The chip, matrix block and platform are joined together with an optical adhesive or by welding. A similar matrix block is used for holding fibres at the opposite side of the chip.

Description

PASSIVE OPTIOUS FIBER ALIGNMENT DEVICE
USING AN ALIGNMENT PLATFORM
BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a device for passively aligning an optical fiber with an optical input / output waveguide and, more particularly, to a device for passively aligning an optical fiber with an optical waveguide of input / output of an integrated optical device in which optical waveguide devices having various functions are integrated into a planar substrate, using an alignment platform.

1. Description of associated art
In general, an active alignment method is used to attach an optical fiber to an optical waveguide device. In the active alignment method, after the incident light is guided by waves to the optical fiber or the optical waveguide device, the position of the optical fiber is precisely adjusted by measuring the optical power at the optical waveguide or the optical fiber output port. Then, the optical fiber and the optical waveguide are fixed in the maximum coupling position. On the other hand, in a passive alignment method, the optical fiber and the optical waveguide are automatically and precisely aligned in accordance with the shape or structure of a coupling portion, during the crossing of a light. in the optical fiber or the waveguide.

 The active alignment method requires a light source and a photodetector to align the optical fiber and the optical waveguide. Also, the optical fiber and the optical waveguide must be precisely aligned, with submicron precision with respect to an alignment axis having six degrees of freedom. Alignment is therefore difficult and time consuming.

SUMMARY OF THE INVENTION
To solve the above problems, an object of the present invention is to provide a passive optical fiber alignment device for easily aligning an optical fiber and an optical waveguide using an alignment platform having alignment bumps and alignment edges, capable of decreasing the time and cost required to attach the optical fiber to an optical waveguide device chip.

 To achieve the object of the present invention, there is provided a passive optical fiber alignment device intended to passively align optical fibers with optical input / output waveguides of an integrated optical device, comprising: an optical fiber matrix block on which the optical fibers are mounted with a predetermined spacing, having alignment grooves formed parallel to the optical fibers, at a predetermined spacing, and an optical fiber fixing plate for fixing the optical fibers mounted to a substrate; an optical waveguide device chip comprising an input / output optical waveguide matrix consisting of optical waveguides corresponding to the optical fibers, intended to be coupled to the optical fibers, and alignment holes ; and an alignment platform having first alignment edges separated by the same spacing as the alignment grooves, to be coupled to the alignment grooves, alignment bumps formed in positions corresponding to the alignment, to be coupled with the alignment holes and a space between the first alignment edges to prevent the optical fiber fixing plate of the optical fiber matrix block from coming into contact with the alignment platform.

 Preferably, the passive optical fiber alignment device further comprises a second block of optical fiber matrix coupled to the other side of the optical waveguide device chip, which is the same as the block of optical fiber. optical fiber matrix, in which the alignment platform comprises second alignment edges intended to be coupled with the second block of optical fiber matrix, at the end of the alignment platform opposite to the first alignment edges and a space between the second displacement edges to prevent the second die block from coming into contact with the alignment platform.

BRIEF DESCRIPTION OF THE DRAWINGS
The above objects and advantages of the present invention will become more evident on reading the detailed description of the preferred embodiments of the invention, given with reference to the accompanying drawings in which
FIG. 1 is a diagram showing the structure of a passive optical fiber alignment device using an alignment platform, according to a preferred embodiment of the present invention;
FIGS. 2A, 2B and 2C are plan, front and side views of an example of an alignment platform according to the present invention;
FIGS. 3A, 3B and 3C are plan, front and side views of an example of an optical fiber matrix block according to the present invention; and
FIGS. 4A, 4B and 4 C are plan, front and side views of an example of a device chip forming an optical waveguide according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Figure 1, a passive optical fiber alignment device according to a preferred embodiment of the present invention comprises an alignment platform 200 having alignment bumps and alignment edges, a optical fiber array block 300 having alignment grooves and an optical waveguide device chip 100 having alignment holes.

 The alignment platform 200 comprises alignment bumps 210 and alignment edges 220 at predetermined locations on its surface as shown in FIG. 1. According to a method of forming this block using a silicon substrate ( Si), a stripe pattern having a suitable width and length is formed of SiO2 or Si3N41 in a portion where the alignment bumps and alignment edges are formed, by photolithography and then wet etched in a solution of potassium hydroxide (KOH). This method is used to form V-shaped grooves in Si, to align the optical fibers in the form of a matrix at a predetermined spacing. Here, using an area (100) of the crystalline Si substrate and anisotropic etching characteristics, bumps and edges having triangular or trapezoidal sections can be obtained. As an alternative, the alignment edges and the alignment bumps can be formed from various materials by mechanical machining or precise molding. Thus, the shapes of the bumps and edges formed on the alignment platform 200 can be modified according to the purpose of use. Also, a portion between the edges 220 formed on the alignment platform is eliminated so that an optical fiber fixing plate 340 does not form a bump against the alignment platform 200 when the block of fiber optics 300 is coupled to the alignment platform 200.

 Figures 2A, 2B and 2C are plan, front and side views of the alignment platform 200 according to a preferred embodiment of the present invention.

 The optical fiber matrix block 300, on which the optical fibers are mounted at a predetermined spacing, includes alignment grooves 320, parallel to the optical fibers and having a predetermined length, and the optical fiber fixing plate 340 for fixing the optical fibers mounted on the substrate. That is, the optical matrix block 300 includes a V-shaped groove matrix for arranging a plurality of optical fibers 310 at a predetermined spacing and the alignment grooves 320 having a predetermined depth and the same separation distance as the alignment edges 220, one above the matrix of each of the grooves of the V-shaped matrix to support the optical fibers.

 A method of manufacturing the optical fiber matrix block 300 including the alignment grooves 320 according to a preferred embodiment of the present invention will be described. A crystalline Si substrate is used. First of all, SiO2 or Si3N4 is deposited on the Si (100) substrate,, eliminated by photolithography, in accordance with a strip pattern, so as to have a suitable width then, wet etched in a KOH solution .

Simultaneously, the alignment grooves 320 can be manufactured by the same process as the matrix of V-shaped grooves intended to support the optical fibers 310.

 FIGS. 3A, 3B and 3C are plan, front and side views of an example of an optical fiber matrix block 300 according to the present invention.

 In general, the overlap diameter of each optical fiber 310 is 125 µm, and the spacing of the V-shaped grooves for supporting the optical fibers is 250 µm. After manufacturing the block of optical fiber matrix 300, the optical fibers 310 are placed in the V-shaped grooves intended to support the optical fibers, an optical adhesive agent 330 is deposited on it, then the fiber fixing plate Optics 340 is placed above it, fixing the optical fibers. The mating surface of the optical matrix block 300 is polished to minimize coupling losses when an optical waveguide of the optical waveguide device 100 is coupled to the optical fibers 310. The optical fiber matrix block 300 including the alignment grooves 320 can also be formed from various materials, by precise mechanical machining or precise molding in place of the previous process. Also, the shapes of the alignment grooves 310 can be modified according to the purpose of use.

 The chip of the optical waveguide device 100, which is formed from a general optical waveguide device, has alignment holes 120 of a predetermined depth on both sides of the matrix of waveguides. optical input / output waves 110, corresponding to the locations of the alignment bumps 210 formed on the alignment platform 200.

 FIGS. 4A, 4B and 4 C are plan, front and side views of an example of a device chip forming an optical waveguide 100 according to the present invention.

A method of manufacturing the optical waveguide device chip 100 having the alignment holes 120 according to an example of the present invention will be described. First, a layer of silica intended to be covered below is formed on a Si substrate by flame hydrolysis (FHD) deposition, then a layer of silica intended to constitute a core is formed thereon, of a material having a refractive index greater than the covering, for
FHD. Then, photolithography and reactive ion etching (RIE) are performed, thereby producing a channel type optical waveguide. The spacing of the optical waveguides within an input / output optical waveguide matrix 110 is made equal to the spacing of the V-shaped grooves supporting the optical fiber of the matrix block of optical fibers 330, that is to say the spacing of optical fibers 310, for example 250 μm. Then, a layer of silica for upper covering is formed by FHD, thus completing the optical waveguide device. The silica layer and partially removed from the optical waveguide device obtained by photolithography, in order to form several adjustment holes 120 of a predetermined shape, at locations separated from the matrix of input optical waveguides / output 110 by a predetermined distance, thereby completing the optical waveguide device chip 100. Here, the locations of the alignment holes 120 correspond to the locations of the alignment bumps 210 for alignment of the platform alignment 200. The mating surface of the optical waveguide device chip 100 is also polished so that coupling losses are minimized when the matrix of optical input / output waveguides 110 of the optical waveguide device chip is coupled with the optical fibers 310.

 The chip of the optical waveguide device 100 having the alignment holes 120 may contain devices forming optical waveguides formed of various materials, such as polymeric optical waveguides, optical waveguides in glass and waveguides in lithium niobate (LiNbO3), as well as optical waveguides in silica.

 The alignment holes 120 can be formed on the device chip forming the optical waveguide 100 by dry etching such as RIE, or precise mechanical machining, by means of the above method. The shape of the alignment holes 120 can be changed to various shapes to allow stable coupling with the alignment bumps 210 of the alignment platform 200.

 A passive alignment method for aligning optical fibers with the optical waveguides by coupling the optical waveguide device chip 100, the alignment platform 200 and the optical fiber matrix block 300, will be described.

This coupling of the three elements occurs on the alignment platform 200. The optical waveguide device chip 100 is first mounted inverted from top to bottom on the alignment platform 200 so that the holes Alignment 120 of the optical waveguide device chip 100 are coupled with alignment bumps 210 of the alignment platform 200. In this assembled state, the optical waveguide device chip 100 is attached to the alignment platform 200.

 Then, the optical fiber matrix block 300 is mounted inverted from top to bottom on the alignment platform 200, so that the alignment grooves 320 of the optical fiber matrix block 300 are coupled to the edges of alignment 220 of the alignment platform 200. Then, the optical fiber matrix block 300 is pushed firmly against the device chip forming the optical waveguide 100.

 In this state, when the three elements are coupled together, the centers of the optical fiber cores 310 correspond exactly to the core centers of the waveguides of the input / output waveguide matrix 110, in all directions. For correspondence in the lateral direction, the position of the alignment grooves 320 relative to the optical fibers 310 of the optical fiber matrix block 300 is adapted to the position of the waveguides of the optical waveguide matrix d input / output 110 relative to the alignment holes 120 of the optical waveguide device chip 100 mounted on the alignment platform 200.

Consequently, the centers of the cores correspond regularly by mounting the block of optical fiber matrix 300 on the alignment platform so that the alignment grooves 320 are coupled with the alignment edges 220. For correspondence in the vertical direction, the depth of the alignment grooves 320 formed in the optical fiber matrix block 300 and the depth of the alignment holes 120 in the optical waveguide device chip 100 are controlled, so that the optical fiber cores 310 are aligned regularly with the waveguide cores of the optical waveguide matrix 110 when mounting the alignment grooves 320 of the optical fiber matrix block 300 and the alignment holes 120 of the optical waveguide device chip 100 on the alignment edges 220 and the alignment bumps 210 of the alignment platform 200.

 After mounting of the optical fiber matrix block 300 and the optical waveguide device chip 100 on the alignment platform 200, the coupling is maintained permanently by using an optical adhesive agent or by welding a metal. previously deposited on the coupling surfaces of the optical fiber matrix block 300 and the optical waveguide device chip 100.

 The passive optical fiber alignment device further includes a second optical fiber matrix block 400 coupled to the other side of the optical waveguide device chip 100, which is the same as the optical matrix block optical fibers 300.

The alignment platform 200 of the passive optical fiber alignment device further comprises second alignment edges 230 at its other end, intended to be coupled to the second block of optical fiber matrix 400 and a space between the second alignment edges 230, which prevents contact with the alignment platform 200 when the second block of optical fiber matrix 400 is mounted on the alignment platform 200. The manufacturing process for the second block of optical fiber matrix 400 and its operating principle, are the same as described above and thus, its explanation will be omitted.

 Consequently, the optical fibers can be easily aligned with optical waveguides by the passive optical fiber alignment device according to the present invention.

 Also, the passive optical fiber alignment device does not require a light source and photodetector, and alignment with submicron precision with respect to an alignment axis having six degrees of freedom, which is essential for the Active alignment, so that lower time and costs are required to attach the optical fibers to the optical waveguide device chip.

Claims (13)

 1. A passive optical fiber alignment device for passively aligning optical fibers (310) with optical input / output waveguides of an integrated optical device, comprising  an optical fiber matrix block (300) on which the optical fibers (310) are mounted with a predetermined spacing, having alignment grooves (320) formed parallel to the optical fibers (310), at a predetermined spacing and a plate fixing optical fibers (340) for fixing the optical fibers (310) mounted to a substrate;  an optical waveguide device chip (100) comprising an input / output optical waveguide matrix consisting of optical waveguides corresponding to the optical fibers (310), intended to be coupled to the optical fibers ( 310), and alignment holes (120); and  an alignment platform (200) having first alignment edges (220) separated by the same spacing as the alignment grooves (320), to be coupled to the alignment grooves (320), bumps d 'alignment (210) formed in positions corresponding to the alignment holes (120), to be coupled with the alignment holes (120), and a space between the first alignment edges (220) to prevent the plate from fiber optic attachment of the fiber optic matrix block (300) to come into contact with the alignment platform (200).  2. passive optical fiber alignment device according to claim 1, characterized in that the alignment platform is formed by forming a pattern having a predetermined width and length on a portion of the silicon substrate where the bumps d alignment (210) and the first alignment edges (220) are intended to be formed, by photolithography, then by wet etching of the resultant in a solution of potassium hydroxide (KOH).  3. passive optical fiber alignment device according to claim 2, characterized in that a surface (100) of the silicon crystal substrate and anisotropic etching characteristics are used to form the alignment bumps (210) and the first alignment edges (220) with a triangular or trapezoidal cross section.  4. passive optical fiber alignment device according to claim 1, characterized in that the alignment platform (200) is formed by mechanical machining or precise molding.  5. passive optical fiber alignment device according to claim 1, characterized in that the block of optical fiber matrix (300) is formed by deposition of SiO2 or Si3N4 on a silicon substrate (100), by removal of SiO2 or Si3N4 according to a strip pattern having a predetermined width by photolithography, then by wet etching of the resultant in a solution of potassium hydroxide (KOH).  6. passive optical fiber alignment device according to claim 1, characterized in that the alignment grooves (320) formed in the optical fiber matrix block (300) each have a V-shaped cross section.  7. passive optical fiber alignment device according to claim 1, characterized in that the block of optical fiber matrix (300) is formed by mechanical machining or precise molding.  8. passive optical fiber alignment device according to claim 1, characterized in that the alignment holes (120) of the optical waveguide device chip (100) are formed at a predetermined depth, in positions corresponding to the positions of the alignment bumps (210).  9. passive optical fiber alignment device according to claim 1, characterized in that the optical waveguide device chip (100) is formed by the steps of  (a) forming a lower covering layer on a substrate  (b) forming a core layer of a material having a higher refractive index than the covering layer and forming an optical waveguide of the channel type by etching  (c) fabricating an optical waveguide device by forming an upper cover layer; and  (d) forming the alignment holes (120) having a predetermined shape on the optical waveguide device in positions separated from the input / output optical waveguide array by a predetermined distance.  10. passive optical fiber alignment device according to claim 9, characterized in that the optical waveguide is a waveguide chosen from the group consisting of an optical waveguide made of silica, a optical waveguide in polymer, an optical waveguide in glass and an optical waveguide in lithium niobate (LiNbO3>  11. passive optical fiber alignment device according to claim 1, characterized in that the alignment holes (120) of the chip of the optical waveguide device (100) are formed by precise mechanical machining.  12. passive optical fiber alignment device according to claim 1, characterized in that the chip of the optical waveguide device (100), the block of optical fiber matrix (300) and the alignment platform ( 200) are joined together by an optical adhesive agent or by welding.  13. A passive optical fiber alignment device according to claim 1, further comprising a second block of optical fiber matrix (400) coupled to the other side of the chip of the optical waveguide device (100), which is the same as the optical fiber matrix block (300), characterized in that the alignment platform (200) comprises second alignment edges (230) intended to be coupled with the second matrix block fiber optics (400), at the end of the alignment platform (200) opposite the first alignment edges (220), and a space between the second displacement edges (220) to prevent the second block of matrix to come into contact with the alignment platform (200).